全文获取类型
收费全文 | 2646篇 |
免费 | 92篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 75篇 |
儿科学 | 56篇 |
妇产科学 | 65篇 |
基础医学 | 338篇 |
口腔科学 | 49篇 |
临床医学 | 266篇 |
内科学 | 494篇 |
皮肤病学 | 17篇 |
神经病学 | 202篇 |
特种医学 | 99篇 |
外科学 | 442篇 |
综合类 | 9篇 |
预防医学 | 192篇 |
眼科学 | 40篇 |
药学 | 253篇 |
中国医学 | 3篇 |
肿瘤学 | 147篇 |
出版年
2022年 | 22篇 |
2021年 | 28篇 |
2020年 | 31篇 |
2019年 | 49篇 |
2018年 | 69篇 |
2017年 | 48篇 |
2016年 | 60篇 |
2015年 | 78篇 |
2014年 | 64篇 |
2013年 | 109篇 |
2012年 | 153篇 |
2011年 | 140篇 |
2010年 | 70篇 |
2009年 | 70篇 |
2008年 | 144篇 |
2007年 | 149篇 |
2006年 | 136篇 |
2005年 | 152篇 |
2004年 | 130篇 |
2003年 | 150篇 |
2002年 | 108篇 |
2001年 | 46篇 |
2000年 | 48篇 |
1999年 | 50篇 |
1998年 | 24篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1995年 | 14篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 21篇 |
1991年 | 25篇 |
1990年 | 32篇 |
1989年 | 28篇 |
1988年 | 28篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 25篇 |
1984年 | 14篇 |
1983年 | 20篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 21篇 |
1976年 | 17篇 |
1975年 | 12篇 |
1974年 | 17篇 |
1968年 | 23篇 |
1967年 | 13篇 |
排序方式: 共有2747条查询结果,搜索用时 15 毫秒
21.
The aim of this study is to describe mental psychiatric health nurses' experiences of caring for persons with the dual disorders of major depression and alcohol abuse. The study was conducted in 2003 on three psychiatric wards located in two general hospitals in Sweden. The study group comprised 11 registered nurses with experience of caring for patients with dual disorders. The data were analyzed by means of qualitative content analysis. The findings revealed three categories: Enabling a good level of cooperation with patients; Facilitating continued care and treatment; and Understanding barriers to cooperation with patients. Building a trusting relationship in order to enable cooperation with patients was the basis for continued care and treatment. The nurses needed more training and multidisciplinary knowledge in order to meet the particular clinical needs of this patient group. Nurses have an important obligation to utilize the best available evidence, including research findings and other scientific sources. 相似文献
22.
Aim: The article focuses on the radioprotective effect of acute hypoxia on healthy tissues during preoperative accelerated hypoxyradiotherapy of colorectal carcinoma performed as locoregional irradiation including the common iliac lymph nodes. Analysis of early and late side effects and complications.Patients and Methods: In this prospective study, early and late complications were assessed in 50 patients as a function of hypoxyradiotherapeutic dose increase. The preliminary treatment results of this radiotherapeutic modification were evaluated after a median follow-up of 48 months using Kaplan-Meier analysis. Between April 1991 and February 1997, 50 patients (36 men and 14 women) with colorectal carcinoma were treated preoperatively with locoregional accelerated hypofractionated hypoxyradiotherapy. The extent of disease was classified according to Dukes' criteria (A. four patients, B: 28 patients, C: 18 patients). We used a 20-MeV linear accelerator with two parallel opposed fields. Hypoxyradiotherapy was peformed extending from the perineum to the vertebral L4 region. Acute hypoxia was induced during irradiation by ventilation of a hypoxic gas mixture containing 7.8–8.0% oxygen. Total doses of 24 Gy/8 days, 28 Gy/9 days, and 32 Gy/10 days were applied in five, 20, and 25 patients, respectively. Low anterior resection or abdominoperineal amputation of the rectum was performed the day after completion of preoperative hypoxyradiotherapy. The early reactions after irradiation were evaluated according to the Common Toxicity Criteria of the National Cancer Institute (CTC-NCI).Results: Early postirradiation proctitis was documented in three and early radiation-induced cystitis in two patients only. Neither early nor late radiation-associated complications were observed in any of the three hypoxyradiotherapy schedules during the follow-up period of 6ndash;105 months. Based on Kaplan-Meier analysis (median 48 months), a 5-year overall survival rate of approximately 61.5% and a local relapse-free survival rate of approximately 84.2% can be expected. Treatment failures were predominantly systemic.Conclusion: We believe it can be concluded that acute hypoxia has a radioprotective effect on normal tissues during accelerated hypoxyradiotherapy of colorectal carcinoma. Hypoxyradiotherapy permits safe administration of doses higher than those tolerated by normoxic, noncancerous tissue, resulting in the amplification of the biological effect of radiation on tumor tissue and contributing to an improved outcome after combined radiosurgical treatment of colorectal carcinoma. 相似文献
23.
Hartford M Wiklund O Mattsson Hultén L Perers E Person A Herlitz J Hurt-Camejo E Karlsson T Caidahl K 《International journal of cardiology》2006,108(1):55-62
OBJECTIVES: The objectives of this study were to examine the time course of the inflammatory response in acute coronary syndromes (ACS) and to assess the markers of inflammation and their relation to disease severity. METHODS: We prospectively studied 134 patients with ACS who survived for at least 30 months. The patients were divided into four groups: acute myocardial infarction (MI) with (n=54) or without (n=46) ST-segment elevation and unstable angina with (n=14) or without (n=20) increased risk. Plasma levels of C-reactive protein (CRP), interleukin-6 (IL-6), secretory phospholipase A2 group IIA (sPLA2-IIA), and intercellular adhesion molecule-1 (ICAM-1) were measured on days 1 and 4 and after 3 and 30 months. RESULTS: The highest levels of CRP and sPLA2-IIA were seen on day 4 but for IL-6 on day 1. These three markers, but not ICAM-1, were significantly related to disease severity, CKMB, and ejection fraction. Patients in Killip class II-IV had higher levels than those in Killip class I. The individual acute-phase responses correlated with marker levels at 3 and 30 months. ICAM-1 correlated with the development of congestive heart failure. CONCLUSIONS: In ACS there seems to be an individual predisposition to inflammatory response. Plasma IL-6 is the first marker to rise, while sPLA2-IIA and CRP peak later. All three markers, especially CRP, may discriminate between MI and non-MI. ICAM-1 seems to reflect other aspects of the inflammatory processes than the other markers. The results emphasize the complexity of the inflammatory response in ACS and stress the need for further studies involving multiple markers. 相似文献
24.
25.
Sartorius B Andersson Y Velicko I De Jong B Löfdahl M Hedlund KO Allestam G Wångsell C Bergstedt O Horal P Ulleryd P Soderstrom A 《Scandinavian journal of infectious diseases》2007,39(4):323-331
A large community outbreak of norovirus (NV) gastrointestinal infection occurred in V?stra G?taland County, Sweden in August 2004, following attendance at recreational lakes. A frequency age-matched case control study was undertaken of persons who had attended these lakes to identify risk factors. 163 cases and 329 controls were included. Analysis indicates that having water in the mouth while swimming (OR=4.7; 95% CI 1.1-20.2), attendance at the main swimming area at Delsj?n Lake (OR=25.5; 95% CI 2.5-263.8), taking water home from a fresh water spring near Delsj?n lake (OR=17.3; 95% CI 2.7-110.7) and swimming less than 20 m from shore (OR=13.4; 95% CI 2.0-90.2) were significant risk factors. The probable vehicle was local contamination of the lake water (especially at the main swimming area). The source of contamination could not be determined. 相似文献
26.
OBJECTIVE: We aimed to investigate whether the elevated risk of gastric cancer among patients with gastric ulcer (GU) and the enigmatic low risk among patients with duodenal ulcer (DU) pertain to both cardia and noncardia cancer. We also studied the risks among operated patients while taking the disparate baseline risks into consideration. METHODS: Retrospective cohorts of 59,550 and 79,412 unoperated patients with DU and GU, respectively, plus 12,840 patients with partial gastric resection and 8,105 with vagotomy, recorded in the Swedish Inpatient Register since 1970, were followed from the first hospitalization (date of operation for the surgery cohort) until occurrence of any cancer, death, emigration, definitive surgery, or December 31, 2003. Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) expressed relative risk (RR), compared to the age-, sex-, and calendar period-matched Swedish population. Cox regression produced adjusted RR estimates among operated patients, relative to unoperated ones with the same ulcer type. RESULTS: While unoperated DU patients had a halved risk of noncardia cancer (SIR=0.5, 95% CI 0.4-0.7), their risk of cardia cancer was slightly above expectation (SIR=1.2, 95% CI 0.8-1.7). Unoperated GU patients had doubled risks for both cancers (SIR=2.1, 95% CI 2.0-2.4 and SIR=1.9, 95% CI 1.4-2.3, respectively). DU patients who underwent gastric resection had a 60% risk elevation (RR=1.6, 95% CI 1.0-2.5) compared to unoperated ones. Vagotomy was associated with a greater risk in the first 10 yr, but this excess disappeared with further follow-up. Resected GU patients had a 40% risk reduction relative to their unoperated peers (RR=0.6, 95% CI 0.5-0.8). This reduction persisted well beyond the first postoperative decade. CONCLUSION: The DU-related protection against gastric cancer does not seem to pertain to cardia cancer. With gastric resection, risks are shifted toward normality, regardless of underlying ulcer type. 相似文献
27.
Hiraoka A Horiike N Akbar SM Michitaka K Matsuyama T Onji M 《Pathology, research and practice》2005,201(5):379-384
CD163 is a marker of activated macrophages, and increased levels of soluble CD163 have been detected in sera obtained from patients with hepatitis. The aim of this study was to detect the expression of CD163 in the liver from patients with viral hepatitis. Frozen sections of liver specimens were obtained from 5 patients with acute viral hepatitis (AH) and from 23 patients with chronic viral hepatitis (CH). The expression of CD163 in the liver was determined immunohistochemically using monoclonal antibody to human CD163. Double immunostaining was done to assess those cell types that express CD163 in the liver. The frequencies of CD163-positive cells were significantly higher both in the portal areas and in the hepatic lobules in the liver of patients with AH compared to those with CH (p < 0.05). Double immunostaining revealed that most of the CD163-positive cells were macrophages and Kupffer cells, because they expressed CD68. The expression of CD163 was very low in endothelial cells and liver stellate cells. This study shows that macrophages are activated in hepatitis liver. 相似文献
28.
K. Olof Johansson Tyler Dillstrom Matteo Monti Farid El Gabaly Matthew F. Campbell Paul E. Schrader Denisia M. Popolan-Vaida Nicole K. Richards-Henderson Kevin R. Wilson Angela Violi Hope A. Michelsen 《Proceedings of the National Academy of Sciences of the United States of America》2016,113(30):8374-8379
Many oxygenated hydrocarbon species formed during combustion, such as furans, are highly toxic and detrimental to human health and the environment. These species may also increase the hygroscopicity of soot and strongly influence the effects of soot on regional and global climate. However, large furans and associated oxygenated species have not previously been observed in flames, and their formation mechanism and interplay with polycyclic aromatic hydrocarbons (PAHs) are poorly understood. We report on a synergistic computational and experimental effort that elucidates the formation of oxygen-embedded compounds, such as furans and other oxygenated hydrocarbons, during the combustion of hydrocarbon fuels. We used ab initio and probabilistic computational techniques to identify low-barrier reaction mechanisms for the formation of large furans and other oxygenated hydrocarbons. We used vacuum-UV photoionization aerosol mass spectrometry and X-ray photoelectron spectroscopy to confirm these predictions. We show that furans are produced in the high-temperature regions of hydrocarbon flames, where they remarkably survive and become the main functional group of oxygenates that incorporate into incipient soot. In controlled flame studies, we discovered ∼100 oxygenated species previously unaccounted for. We found that large alcohols and enols act as precursors to furans, leading to incorporation of oxygen into the carbon skeletons of PAHs. Our results depart dramatically from the crude chemistry of carbon- and oxygen-containing molecules previously considered in hydrocarbon formation and oxidation models and spearhead the emerging understanding of the oxidation chemistry that is critical, for example, to control emissions of toxic and carcinogenic combustion by-products, which also greatly affect global warming.Oxygenated hydrocarbons produced during combustion can have a wide range of detrimental effects on human health, air quality, and regional and global climate. Furans, for example, are compounds that contain five-membered rings with four carbon atoms and one oxygen atom. They are frequently observed in the exhaust plumes and nearby environment of combustion sources. Many studies have shown that they are toxic, whether ingested or inhaled, and thus pose a considerable threat to human health (1–4). The simplest of these compounds (i.e., unsubstituted furan, C4H4O) is a cyclic, dienic ether with a low molecular weight, high volatility, and high lipophilicity. Studies on rats and mice have shown a dose-dependent increase in hepatocellular adenomas and carcinomas, indicating that furan is carcinogenic (4), and furan is marked as a high-priority substance and a carcinogenic risk by the World Health Organization (5).Combustion sources of furans include biomass burning (6–9), cigarette and pipe smoke (10, 11), waste incineration (12), electronic waste recycling (13, 14), and volcanic activity (15). The polychlorinated dibenzofurans (PCDFs) are among the most notorious environmental pollutants, and the main source of PCDFs is biomass burning (6–9, 16). Nonchlorinated furans and PCDFs have been shown to be kinetically linked (17, 18). Furans released during combustion are often partitioned into particles and are found in ash from peat (9) and wood (6) burning, in primary organic aerosols from meat cooking (19), and in secondary organic aerosols from hydrocarbon oxidation (20, 21). Wood burning for heating and cooking constitute a major human exposure to airborne particulate PCDFs in some parts of the world (22, 23).Previous work has suggested that oxygenated species can be attached to surfaces of soot particles of varying maturity emitted from flames and diesel engines, even before atmospheric processing (24–32). Functional groups that have been identified include alcohols/enols, carbonyls, peroxies, and ethers. Oxygen atoms bound to organic species on the particle surface have been shown to greatly affect soot hygroscopicity (28) and the ability of soot particles to adsorb atmospheric water vapor and act as cloud-condensation or ice nuclei. Soot particles emitted from combustors, such as diesel engines, are generally hydrophobic, and enhancements in hygroscopic particle emissions could have substantial indirect climate effects via their influence on cloud formation (33). The effect of soot emissions on cloud-nucleation properties is a major uncertainty in climate predictions (34–36).Despite the impact of large oxygenated hydrocarbons on combustion chemistry, the environment, and human health, very little is known about their formation mechanisms and emissions. In this paper we present evidence of the formation of oxygenated compounds, including furans, during the combustion of hydrocarbon fuels. Via a synergistic approach that includes ab initio methods and a stochastic model in conjunction with experimental measurements, we identify reaction pathways leading to formation of oxygenated compounds during the combustion of ethylene. We recorded aerosol mass spectra sampled from premixed and diffusion flames, using synchrotron-generated vacuum-UV (VUV) radiation for ionization, for comparison with masses of the predicted chemical compositions. The mass spectra show masses of oxygenated species that agree with the atomic compositions predicted by the simulations. Both experiments and simulations demonstrate that ∼50% of the mass peaks observed at some flame heights in the mass range 140–350 u (unified atomic mass units) contain signal from oxygenated species. We also recorded X-ray photoelectron spectroscopy (XPS) spectra of soot samples extracted from these flames for further validation of these mechanisms by comparison with functional groups of the predicted oxygenated species incorporated into particles. The XPS measurements confirm formation of furan precursors, hydroxyl groups, early in the soot-formation process and evolution of furan signatures, ether groups, as the combustion and particles evolve.The present study represents an important step toward the development of predictive models for the oxidation of hydrocarbons, which will require that the presence and reactivity of these oxygenated compounds are taken into account. Understanding the chemistry related to high-temperature hydrocarbon oxidation may provide a key to controlling emissions of harmful combustion byproducts, such as soot, nonchlorinated furans, and PCDFs, leading to multiple environmental and health benefits. 相似文献
29.
Purpose. To describe how women with a spinal cord injury (SCI) perceived changes in the social network, and how these changes affected their ability to participate in occupation.
Method. Thirteen women, aged 25 to 61 years, with a SCI were interviewed twice. The interviews focused on their ability to participate in occupation, their relations with individuals within the social network, and changes in the social network following the SCI. The analysis was carried out using qualitative content analysis.
Results. The women described an emotional need for social support after the SCI to participate in occupation. This was a new experience that required time to adapt to. The women also described a need for practical social support from the social network members to manage meaningful occupation. After the SCI, the women had developed new habits through close cooperation with members in the social network. The women felt that they had become more responsible for the development of their relations. Many relations had improved after the SCI, while some had decreased. The women had also developed new relations with other persons with disabilities.
Conclusions. The women perceived substantial changes in the social network following the SCI, which in several ways affected their ability to participate in occupation. To adapt to their new life situation, the women gradually developed different strategies. The results point out the need to identify persons in the social network that women with SCI develop relations with, and integrate them in the rehabilitation process. 相似文献
Method. Thirteen women, aged 25 to 61 years, with a SCI were interviewed twice. The interviews focused on their ability to participate in occupation, their relations with individuals within the social network, and changes in the social network following the SCI. The analysis was carried out using qualitative content analysis.
Results. The women described an emotional need for social support after the SCI to participate in occupation. This was a new experience that required time to adapt to. The women also described a need for practical social support from the social network members to manage meaningful occupation. After the SCI, the women had developed new habits through close cooperation with members in the social network. The women felt that they had become more responsible for the development of their relations. Many relations had improved after the SCI, while some had decreased. The women had also developed new relations with other persons with disabilities.
Conclusions. The women perceived substantial changes in the social network following the SCI, which in several ways affected their ability to participate in occupation. To adapt to their new life situation, the women gradually developed different strategies. The results point out the need to identify persons in the social network that women with SCI develop relations with, and integrate them in the rehabilitation process. 相似文献
30.
Götz H de Jong B Lindbäck J Parment PA Hedlund KO Torvén M Ekdahl K 《Scandinavian journal of infectious diseases》2002,34(2):115-121
In March 1999, an outbreak of gastroenteritis occurred affecting 30 day-care centres served by the same caterer. A retrospective cohort study was performed in 13 randomly selected day-care centres to determine the source and mode of transmission. Electron microscopy and PCR were used to verify the diagnosis. The overall attack rate (AR) was 37% (195/524): 30% in children and 62% in adults. Modified by the age of the patient, eating pumpkin salad served on 1 March was associated with becoming an early case (odds ratio = 3.9; 95% confidence interval 1.8-8.8). No significant association was found between food consumption and becoming a late case. The primary food-borne AR was 27% and the secondary AR was 14%. The same genotype of Norwalk-like virus was found in 5 cases and in 1 ill and 1 asymptomatic food-handler. Contamination by 1 of the food-handlers seems the most likely route of spread of the virus and underlines the importance of strict hygienic routines. 相似文献