首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5255篇
  免费   296篇
  国内免费   22篇
耳鼻咽喉   51篇
儿科学   98篇
妇产科学   57篇
基础医学   659篇
口腔科学   83篇
临床医学   553篇
内科学   1421篇
皮肤病学   94篇
神经病学   507篇
特种医学   237篇
外科学   723篇
综合类   15篇
一般理论   5篇
预防医学   311篇
眼科学   43篇
药学   375篇
中国医学   7篇
肿瘤学   334篇
  2024年   4篇
  2023年   31篇
  2022年   56篇
  2021年   132篇
  2020年   70篇
  2019年   114篇
  2018年   166篇
  2017年   128篇
  2016年   130篇
  2015年   160篇
  2014年   207篇
  2013年   281篇
  2012年   430篇
  2011年   466篇
  2010年   254篇
  2009年   209篇
  2008年   383篇
  2007年   355篇
  2006年   289篇
  2005年   350篇
  2004年   307篇
  2003年   259篇
  2002年   238篇
  2001年   39篇
  2000年   30篇
  1999年   38篇
  1998年   42篇
  1997年   46篇
  1996年   42篇
  1995年   47篇
  1994年   36篇
  1993年   27篇
  1992年   22篇
  1991年   15篇
  1990年   22篇
  1989年   21篇
  1988年   8篇
  1987年   5篇
  1986年   15篇
  1985年   15篇
  1984年   10篇
  1983年   11篇
  1982年   16篇
  1981年   12篇
  1980年   9篇
  1979年   3篇
  1977年   3篇
  1975年   5篇
  1974年   3篇
  1969年   3篇
排序方式: 共有5573条查询结果,搜索用时 12 毫秒
1.
Objective: To study the pharmacodynamic and pharmacokinetic properties of oral and intravenous methylergometrine upon uterine motility during menstruation. Study-design: Intra-uterine pressure was measured in six volunteers with a fluid-filled sponge-tipped catheter during menstruation. Methylergometrine was given orally (0.5 mg) or intravenously (0.2 mg) in a cross-over design. Results: After intravenous administration, a fast increase of the frequency of uterine contractions and basal tone occurred with a decrease of amplitude, lasting at least 30 min. Oral administration had a late and less marked effect on uterine motility. An intravenous dose administered 24 h after an oral dose had no effect on uterine motility. Pharmacokinetic data, such as the maximum plasma concentration (Cmax), the time at which Cmax is reached (tmax) and the half-life of absorption (t1/2abs) also demonstrated large individual variations after oral administration. Conclusion: Oral administration of methylergometrine had an unpredictable and late effect on uterine motility on the menstruating uterus, probably due to an unpredictable bioavailability, in contrast with the fast and predictable effect after intravenous administration.  相似文献   
2.
BACKGROUND: End-stage renal disease patients have a poor quality of life (QoL), suffer from impaired cognitive functioning, and their electroencephalogram (EEG) shows abnormalities. Conventional haemodialysis (CHD) only partially restores these disorders. Short daily haemodialysis (SDHD) has been reported to improve QoL, but effects on cognitive functioning and EEG have yet to be described. METHODS: Of the 13 patients (11 male, 2 female, age 45.5 +/- 8.1 years), 11 completed the Kidney Disease Quality of Life and Affect Balance Scale questionnaires, 10 underwent neuropsychological testing, and all 13 underwent EEG examination. For the neuropsychological assessments, nine patients (six male, three female, age 45.4 +/- 12.6) who remained on the CHD schedule, served as controls. The dialysis schedule of thrice-a-week for 4 h was changed in the experimental group to six times a week for 2 h (SDHD) over a period of 6 months and back to thrice a week for 4 h. RESULTS: When on SDHD, patients rated several dimensions of health-related QoL as being improved. After resuming CHD, one of these dimensions again decreased and several others worsened even lower than baseline. Cognitive functioning did not change when compared with control data. On the EEG, alpha peak frequency increased slightly when on SDHD but decreased significantly after resuming CHD. CONCLUSIONS: SDHD improves health-related QoL, but has no clear effects on cognitive functioning and EEG. Resumption of CHD after SDHD decreases aspects of QoL and EEG alpha peak frequency but has no effect on cognitive functioning.  相似文献   
3.
OBJECTIVE Protein hypercatabolism and preservation of fat depots are hallmarks of critical illness, which is associated with blunted pulsatile GH secretion and low circulating IGF-I, TSH, T4 and T3. Repetitive TRH administration is known to reactivate the pituitary-thyroid axis and to evoke paradoxical GH release in critical illness. We further explored the hypothalamic-pituitary function in critical illness by examining the effects of GH-releasing hormone (GHRH) and/or GH-releasing peptide-2 (GHRP-2) and TRH administration. PATIENTS AND DESIGN Critically ill adults (n=40; mean age 55 years) received two i.v. boluses with a 6-hour interval (0900 and 1500 h) within a cross-over design. Patients were randomized to receive consecutively placebo and GHRP-2 (n=10), GHRH and GHRP-2 (n=10), GHRP-2 and GHRH+GHRP-2 (n=10), GHRH+GHRP-2 and GHRH+GHRP-2+TRH (n=10). The GHRH and GHRP-2 doses were 1μg/kg and the TRH dose was 200μg. Blood samples were obtained before and 20, 40, 60 and 120 minutes after each injection. MEASUREMENTS Serum concentrations of GH, T4, T3, rT3, thyroid hormone binding globulin (TBG), IGF-I, insulin and cortisol were measured by RIA; PRL and TSH concentrations were determined by IRMA. RESULTS Critically ill patients presented a striking GH response to GHRP-2 (mean±SEM peak GH 51±9 μg/l in older patients and 102±2μg/l in younger patients; P=0.005 vs placebo). The mean GH response to GHRP-2 was more than fourfold higher than to GHRH (P=0.007). In turn, the mean GH response to GHRH+GHRP-2 was 2.5-fold higher than to GHRP-2 alone (P=0.01), indicating synergism. Adding TRH to the GHRH+GHRP-2 combination slightly blunted this mean response by 18% (P=0.01). GHRP-2 had no effect on serum TSH concentrations whereas both GHRH and GHRH+GHRP-2 evoked an increase in peak TSH levels of 53 and 32% respectively. The addition of TRH further increased this TSH response < ninefold (P=0.005), elicited a 60% rise in serum T3 (P=0.01) and an 18% increase in T4 (P=0.005) levels, without altering rT3 or TBG levels. GHRH and/or GHRP-2 induced a small increase in serum PRL levels. The addition of TRH magnified the PRL response 2.4-fold (P=0.007). GHRP-2 increased basal serum cortisol levels (531±29nmol/l) by 35% (P=0.02); GHRH provoked no additional response, but adding TRH further increased the cortisol response by 20% (P=0.05). CONCLUSIONS The specific character of hypothalamic-pituitary function in critical illness is herewith extended to the responsiveness to GHRH and/or GHRP-2 and TRH. The observation of striking bursts of GH secretion elicited by GHRP-2 and particularly by GHRH+GHRP-2 in patients with low spontaneous GH peaks opens the possibility of therapeutic perspectives for GH secretagogues in critical care medicine.  相似文献   
4.
5.
We investigated four acrylic cement preparation techniques for their effects on cement porosity: hand mixing, pressurization in a pneumatic pistol, centrifugation, and vacuum mixing. All the techniques were tested on three types of cement with different viscosity characteristics. The best results were obtained with vacuum mixing using a newly designed experimental system, yielding porosity reductions of 60-80 percent relative to hand mixing. Vacuum mixing with a commercial system was also effective, but to a somewhat lesser extent.

Pressurization and centrifugation had no substantial effect on the overall porosity. Centrifugation led to considerable nonuniformity in the distribution of pores and additives.  相似文献   
6.
7.
The purpose of this study was to present the long-term follow-up of a case series of arthroscopically assisted fixation of juvenile intraarticular epiphyseal ankle fractures. The functional and radiographic outcomes of 6 patients with a range of follow-up of 1 to 5 years were evaluated. Five of the 6 patients had triplane injuries, whereas the remaining patient sustained a juvenile Tillaux fracture. All of the patients returned to full activity within 14 weeks of surgery, and none of the patients had any restriction in the ankle range of motion at the time of last follow-up. The results of this small series of patients suggest that arthroscopic-assisted, percutaneous fixation of intraarticular juvenile epiphyseal ankle fractures is an effective, less invasive surgical technique. Several surgical maneuvers that are helpful in the consistent execution of this technique are also mentioned.  相似文献   
8.
9.
Infection with human immunodeficiency virus (HIV) and the resulting immunosuppression are associated with an increased risk for human papillomavirus (HPV) persistence and related malignancies. In the present study we investigated the prevalence of HPV in urine samples from 104 HIV-infected men with low CD4+ cell counts (<100 per mm(3)) and 115 urine samples from HIV-negative men. A high prevalence of HPV DNA (39.4%) was found in the HIV patients. Most of the HPV types were high risk (81.4%), with HPV 52 as the most prevalent type (12.5%), followed by HPV 18 (6.7%), HPV 35 (5.8%), and HPV 70 (4.8%). Multiple HPV genotypes were observed in 17 (41%) of the 41 HPV- and HIV-positive men. In contrast, only 11 (9.6%) HPV DNA-positive cases were observed among the 115 HIV-uninfected men, and 3 (27.3%) contained multiple genotypes. Quantitative analyses indicated that the HPV viral load, as measured in urine samples, is significantly higher in HIV-positive men compared to HIV-negative men. In the present study we show that urine samples are useful for detecting HPV DNA, there is a high prevalence of HPV in HIV-positive men, and the HPV viral load is substantially higher in HIV-positive than in HIV-negative men. More studies are needed to evaluate the risk and natural development of HPV-related malignancies in HIV-positive men.  相似文献   
10.
Connective tissue growth factor (CTGF) is reported to be a target gene of transforming growth factor beta (TGFbeta) and bone morphogenetic protein (BMP) in vitro. Its physiological role in angiogenesis and skeletogenesis during mouse development has been described recently. Here, we have mapped expression of CTGF mRNA during mouse heart development, postnatal adult life, and after experimental myocardial infarction. Furthermore, we investigated the relationship between CTGF and the BMP/TGFbeta signaling pathway in particular during heart development in mutant mice. Postnatally, CTGF expression in the heart became restricted to the atrium. Strikingly, 1 week after myocardial infarction, when myocytes have disappeared from the infarct zone, CTGF and TGFbeta expression as well as activated forms of TGFbeta but not BMP, Smad effector proteins are colocalized exclusively in the fibroblasts of the scar tissue, suggesting possible cooperation between CTGF and TGFbeta during the pathological fibrotic response.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号