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   1098篇
  免费   66篇
  国内免费   17篇
耳鼻咽喉   8篇
儿科学   25篇
妇产科学   12篇
基础医学   184篇
口腔科学   6篇
临床医学   90篇
内科学   225篇
皮肤病学   29篇
神经病学   99篇
特种医学   15篇
外科学   127篇
综合类   27篇
一般理论   1篇
预防医学   170篇
眼科学   8篇
药学   81篇
中国医学   3篇
肿瘤学   71篇
  2024年   3篇
  2023年   17篇
  2022年   35篇
  2021年   40篇
  2020年   21篇
  2019年   43篇
  2018年   38篇
  2017年   24篇
  2016年   35篇
  2015年   44篇
  2014年   44篇
  2013年   59篇
  2012年   85篇
  2011年   103篇
  2010年   51篇
  2009年   47篇
  2008年   59篇
  2007年   68篇
  2006年   67篇
  2005年   70篇
  2004年   51篇
  2003年   55篇
  2002年   47篇
  2001年   8篇
  2000年   5篇
  1999年   3篇
  1998年   5篇
  1997年   5篇
  1996年   8篇
  1995年   2篇
  1994年   2篇
  1993年   5篇
  1992年   3篇
  1991年   2篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1986年   4篇
  1985年   5篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1969年   1篇
  1968年   1篇
排序方式: 共有1181条查询结果,搜索用时 31 毫秒
101.
Four pearl millet cultivars of two different species--Kordofani and Ugandi (Pennisetum typhoideum) and Madelkawaya and Shambat (Pennisetum glaucum)--were germinated for 6 days. The germinated grains were dried and milled. Phytic acid and polyphenol contents and hydrochloric acid (HCl) extractability of minerals from the malt flours were determined at intervals of 2 days during germination. Phytic acid and polyphenol contents decreased significantly (P <0.01) with an increase in germination time, with a concomitant increase in HCl extractable minerals. However, the major mineral content was significantly decreased while that of trace minerals was increased with germination time. When the grains were germinated for 6 days, Madelkawaya had higher extractable calcium while Ugandi had higher extractable phosphorus, whereas iron and manganese recorded high levels in Shambat and Madelkawaya, respectively. There was good correlation between antinutritional factors reduction and the increment in extractable minerals with germination time.  相似文献   
102.
Diaries are written for critically ill patients, to help them understand their intensive care stay and come to terms with their illness. The aim of this content analysis of eight such diaries is to understand the potential benefits for patients and families of this care intervention. A main category emerged: Sharing throughout the ICU time. Four themes were identified: (a) Sharing the story, (b) Sharing the presence, (c) Sharing feelings, and (d) Sharing through support. The first theme reflects the narration of daily events. The second is the perceived presence of health professionals and family at the patient's bedside and the presence of the patient as a person through the diary entries. The third theme describes the expression of feelings as written throughout the text. The last theme refers to the support offered to the patient. The diaries reflect the commitment and care of contributors to the patients' welfare.  相似文献   
103.
BACKGROUND: The incidence of end-stage renal failure is high and it is responsible for the increase of the rate of morbidity and mortality rates among our patients. AIM:The objective is to study patient characteristics before starting hemodialysis and to evaluate factors influencing their short and long term survival. METHODS: This is a prospective study of 127 patients starting hemodialysis between June and December 2001. On May 31, 2005, their survival was analyzed according to different parameters. RESULTS: Patients were 77 males and 50 females. Their mean age was 51.4 +/- 16.1 years (15 to 78 years). Diabetes was observed in 33.9% of cases. Only 70.9% of patients were covered by a social service. Chronic renal failure was diagnosed at the end stage in 34.6% of cases. Before starting hemodialysis, only 4 patients were vaccinated against B hepatitis and arteriovenous fistula were not made in any patients. Pericarditis was observed in 9.4% of patients. Albuminemia was < 35 g/l in 60.5% of patients. First hemodialysis session was programmed in 53.5% of patients and realized urgently in 46.3% of patients. Patients were hemodialysed 4, 8 and 12 hours per week respectively in 16.5%, 15.8% and 67.7% of cases. On May 31, 2005, 35.4% of patients died. Their actuarial survivals at 3 months, 1 year and 4 years were respectively at 87.5%, 79.5% and 64.4%. Acturial survival was bad in patients with pericarditis, diabetes, hemodialysed less than 12 hours/week and when the first hemodialysis session was started urgently. CONCLUSION: The diagnosis of renal failure was frequently made at end-stage. There are no preparations before starting hemodialysis. We have to reinforce prevention programmes and increase the number of nephrologists and nephrology departments.  相似文献   
104.
Rabies virus strain production in Vero cells grown on Cytodex 1 in a 2 L stirred tank bioreactor and in a medium free of components of human or animal origin (VP-SFM) is described. Cell banking procedure in VP-SFM supplemented with an animal components free mixture (10%DMSO+0.1%methylcellulose) was reported and cell growth after revitalization was assessed. Vero cells exhibited growth performances (specific growth rate and cell division number) similar to that obtained in serum containing medium. To design a scalable process that is totally free of animal-derived substances, two proteases: TrypLE Select and Accutase, were assessed as an alternative to trypsin which is routinely used for cell passage. Growth performance of Vero cells grown in VP-SFM and MEM+10% fetal calf serum (FCS) over four passages and subcultivated with either TrypLE Select or Accutase was evaluated. TrypLE Select showed the best performance in terms of specific growth rate and cell division number. Kinetics of cell growth and rabies virus production (LP2061/Vero strain) were investigated in spinner flask and in a 2 L bioreactor. In spinner flask, a maximal cell density level of 1.85x10(6) cells/mL was achieved when the cells were grown in VP-SFM on 2 g/L Cytodex 1. Cell infection experiments conducted at an MOI of 0.3 and without the medium exchange step, typically needed for serum containing rabies virus production, resulted in a maximal virus titer equal to 2x10(7) (Fluorescent Focus Unit) FFU/mL. In stirred tank bioreactor, Vero cell growth in VP-SFM on 3 g/L Cytodex 1 was shown to be sensitive to the aeration mode. Sparging the culture was detrimental for cell growth, whereas cell density level was greatly enhanced when only headspace aeration was used. A cell density level of 2.6x10(6) cells/mL was obtained when the cells were grown on 3g/L Cytodex 1 and in batch culture mode. Cell infection at an MOI of 0.1 without any medium exchange, yielded a maximal rabies virus titer of 2.4x10(7) FFU/mL. Furthermore, Vero cell growth in a 2 L bioreactor using recirculation culture mode during cell proliferation step and perfusion for virus multiplication phase was investigated. In comparison to batch culture, a higher cell density level that was equal to 5x10(6) cells/mL was reached. Cell infection under conditions similar to batch culture, resulted in a maximal virus titer equal to 1.38x10(8) FFU/mL. The potency of the pooled inactivated virus harvests showed an activity of 2.58 IU/mL which was comparable to that obtained in serum supplemented medium.  相似文献   
105.
OBJECTIVES: To assess the relationships between current smoking status and psychosocial working conditions. METHODS: A cross-sectional population-based telephone survey was conducted (66% response rate, N = 1,101). Job stress was measured using the demand/control, effort/reward imbalance (ERI), and job pressure models. Multiple regression modelling was conducted for smoking status (current versus non-smokers, and a more restricted analysis of current versus former-smokers) and daily smoking intensity outcomes in relation to job stress measures, working hours, shift work, and other independent variables. RESULTS: After adjustment for age, education, martial status, and hostility, high job strain was positively associated with current smoking in men only. Employment in active jobs was associated with decreased odds of smoking among women only. High strain jobs were associated with decreased odds of current smoking compared to former smoking in women. In men, extreme and moderate job pressure were related to current smoking compared to current non-smoking, and moderate job pressure was associated with current smoking compared with former smokers. Other working conditions associated with smoking were excessive working hours in men and physical demand in women. Daily smoking intensity in current smokers was associated with high psychological demand and with ERI in women. CONCLUSIONS: These results suggest that job stress is related to smoking status at the population level, with different patterns in men and women.  相似文献   
106.
107.

Aims

Multiple genetic alterations, including alternative lengthening of telomeres (ALT) and NOTCH mutations, have been described in angiosarcoma. Loss of α‐thalassaemia/mental retardation syndrome X‐linked (ATRX) and death domain‐associated protein 6 (DAXX) expression is frequently associated with the ALT phenotype. Additionally, inhibition of NOTCH signalling induces the development of malignant vascular tumours in mice, indicating a tumour suppressive role of the NOTCH pathway in the pathogenesis of angiosarcoma. The aim of this study was to evaluate the immunohistochemical expression of ATRX, DAXX and NOTCH receptors (NOTCH1 and NOTCH2) in a large cohort of angiosarcomas, and study their clinicopathological and prognostic significance.

Methods and results

One hundred and forty cases of angiosarcoma were stained for ATRX, DAXX, NOTCH1 and NOTCH2. ATRX loss (<10% labelling) was seen in seven of 118 (6%) cases, and was more frequent in deep soft tissue tumours than in other body sites (P = 0.004). Angiosarcomas with ATRX loss were associated with worse event‐free survival than angiosarcomas with retained ATRX expression (P = 0.003). DAXX was retained in all specimens examined. Decreased NOTCH1 expression (≤1+ intensity) was seen in 29 of 123 (24%) cases, and was associated with a cutaneous site of origin (P = 0.013) and advanced disease (P = 0.026). NOTCH2 expression was decreased in 16 of 103 (16%) cases, was associated with visceral tumours (P = 0.001), and correlated with worse disease‐specific survival (P = 0.033).

Conclusions

ATRX, NOTCH1 and NOTCH2 expression varies in angiosarcomas and shows significant correlations with site of origin and poor clinical outcome, thus highlighting the biological heterogeneity within this tumour type.  相似文献   
108.
Experimental autoimmune encephalomyelitis (EAE) is mediated by autoantigen-specific T cells dependent on critical costimulatory signals for their full activation and regulation. We report that the programmed death-1 (PD-1) costimulatory pathway plays a critical role in regulating peripheral tolerance in murine EAE and appears to be a major contributor to the resistance of disease induction in CD28-deficient mice. After immunization with myelin oligodendrocyte glycoprotein (MOG) there was a progressive increase in expression of PD-1 and its ligand PD-L1 but not PD-L2 within the central nervous system (CNS) of mice with EAE, peaking after 3 wk. In both wild-type (WT) and CD28-deficient mice, PD-1 blockade resulted in accelerated and more severe disease with increased CNS lymphocyte infiltration. Worsening of disease after PD-1 blockade was associated with a heightened autoimmune response to MOG, manifested by increased frequency of interferon gamma-producing T cells, increased delayed-type hypersensitivity responses, and higher serum levels of anti-MOG antibody. In vivo blockade of PD-1 resulted in increased antigen-specific T cell expansion, activation, and cytokine production. Interestingly, PD-L2 but not PD-L1 blockade in WT animals also resulted in disease augmentation. Our data are the first demonstration that the PD-1 pathway plays a critical role in regulating EAE.  相似文献   
109.

OBJECTIVE:

Smoking prevalence is frequently estimated on the basis of self-reported smoking status. That can lead to an underestimation of smoking rates. The aim of this study was to evaluate the difference between self-reported smoking status and that determined through the use of objective measures of smoking at a pulmonary outpatient clinic.

METHODS:

This was a cross-sectional study involving 144 individuals: 51 asthma patients, 53 COPD patients, 20 current smokers, and 20 never-smokers. Smoking status was determined on the basis of self-reports obtained in interviews, as well as through tests of exhaled carbon monoxide (eCO) and urinary cotinine.

RESULTS:

All of the asthma patients and COPD patients declared they were not current smokers. In the COPD and asthma patients, the median urinary cotinine concentration was 167 ng/mL (range, 2-5,348 ng/mL) and 47 ng/mL (range, 5-2,735 ng/mL), respectively (p < 0.0001), whereas the median eCO level was 8 ppm (range, 0-31 ppm) and 5 ppm (range, 2-45 ppm), respectively (p < 0.05). In 40 (38%) of the patients with asthma or COPD (n = 104), there was disagreement between the self-reported smoking status and that determined on the basis of the urinary cotinine concentration, a concentration > 200 ng/mL being considered indicative of current smoking. In 48 (46%) of those 104 patients, the self-reported non-smoking status was refuted by an eCO level > 6 ppm, which is also considered indicative of current smoking. In 30 (29%) of the patients with asthma or COPD, the urinary cotinine concentration and the eCO level both belied the patient claims of not being current smokers.

CONCLUSIONS:

Our findings suggest that high proportions of smoking pulmonary patients with lung disease falsely declare themselves to be nonsmokers. The accurate classification of smoking status is pivotal to the treatment of lung diseases. Objective measures of smoking could be helpful in improving clinical management and counseling.  相似文献   
110.
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