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   2027篇
  免费   156篇
  国内免费   10篇
耳鼻咽喉   39篇
儿科学   172篇
妇产科学   13篇
基础医学   216篇
口腔科学   53篇
临床医学   137篇
内科学   369篇
皮肤病学   22篇
神经病学   107篇
特种医学   176篇
外科学   341篇
综合类   65篇
预防医学   164篇
眼科学   18篇
药学   225篇
中国医学   6篇
肿瘤学   70篇
  2023年   14篇
  2021年   21篇
  2020年   12篇
  2019年   35篇
  2018年   27篇
  2017年   17篇
  2016年   41篇
  2015年   67篇
  2014年   57篇
  2013年   65篇
  2012年   85篇
  2011年   89篇
  2010年   61篇
  2009年   60篇
  2008年   62篇
  2007年   70篇
  2006年   65篇
  2005年   82篇
  2004年   69篇
  2003年   77篇
  2002年   62篇
  2001年   58篇
  2000年   58篇
  1999年   60篇
  1998年   55篇
  1997年   60篇
  1996年   41篇
  1995年   33篇
  1994年   29篇
  1993年   29篇
  1992年   44篇
  1991年   43篇
  1990年   48篇
  1989年   61篇
  1988年   51篇
  1987年   53篇
  1986年   44篇
  1985年   29篇
  1984年   14篇
  1983年   19篇
  1982年   15篇
  1981年   12篇
  1979年   15篇
  1977年   13篇
  1976年   12篇
  1973年   12篇
  1972年   16篇
  1971年   23篇
  1970年   11篇
  1969年   17篇
排序方式: 共有2193条查询结果,搜索用时 0 毫秒
11.
12.
KA Forde 《Surgical endoscopy》1998,12(12):1375-1376
  相似文献   
13.
14.
PURPOSE: To identify benchmarks of financial and staff support in internal medicine residency training programs and their correlation with indicators of quality. METHOD: A survey instrument to determine characteristics of support of residency training programs was mailed to each member program of the Association of Program Directors of Internal Medicine. Results were correlated with the three-year running average of the pass rates on the American Board of Internal Medicine certifying examination using bivariate and multivariate analyses. RESULTS: Of 394 surveys, 287 (73%) were completed: 74% of respondents were program directors and 20% were both chair and program director. The mean duration as program director was 7.5 years (median = 5), but it was significantly lower for women than for men (4.9 versus 8.1; p =.001). Respondents spent 62% of their time in educational and administrative duties, 30% in clinical activities, 5% in research, and 2% in other activities. Most chief residents were PGY4s, with 72% receiving compensation additional to base salary. On average, there was one associate program director for every 33 residents, one chief resident for every 27 residents, and one staff person for every 21 residents. Most programs provided trainees with incremental educational stipends, meals while oncall, travel and meeting expenses, and parking. Support from pharmaceutical companies was used for meals, books, and meeting expenses. Almost all programs provided meals for applicants, with 15% providing travel allowances and 37% providing lodging. The programs' board pass rates significantly correlated with the numbers of faculty fulltime equivalents (FTEs), the numbers of resident FTEs per office staff FTEs, and the numbers of categorical and preliminary applications received and ranked by the programs in 1998 and 1999. Regression analyses demonstrated three independent predictors of the programs' board pass rates: number of faculty (a positive predictor), percentage of clinical work performed by the program director (a negative predictor), and financial support from pharmaceutical companies (also a negative predictor). CONCLUSIONS: These results identify benchmarks of financial and staff support provided to internal medicine residency programs. Some of these benchmarks are correlated with board pass rate, an accepted indicator of quality in residency training. Program directors and chairs can use this information to identify areas that may benefit from enhanced financial and administrative support.  相似文献   
15.
16.
AIMS: An important consideration in the design of a tumour vaccine is the ability of tumour-specific cytotoxic T lymphocytes (CTL) to recognise unmanipulated tumour cells in vivo. To determine whether B-CLL might use an escape strategy, the current studies compared B-CLL and normal B cell MHC class I expression. METHODS: Flow cytometry, TAP allele PCR and MHC class I PCR were used. RESULTS: While baseline expression of MHC class I did not differ, upregulation of MHC class I expression by B-CLL cells in response to IFN-gamma was reduced. No deletions or mutations of TAP 1 or 2 genes were detected. B-CLL cells upregulated TAP protein expression in response to IFN-gamma. Responsiveness of B-CLL MHC class I mRNA to IFN-gamma was not impaired. CONCLUSIONS: The data suggest that MHC class I molecules might be less stable at the cell surface in B-CLL than normal B cells, as a result of the described release of beta(2)m and beta(2)m-free class I heavy chains from the membrane. This relative MHC class I expression defect of B-CLL cells may reduce their susceptibility to CTL lysis in response to immunotherapeutic approaches.  相似文献   
17.
The Th2 cytokine interleukin 4 (IL-4) has been identified as having a central role in driving the inflammatory immune responses which are present in atopic airway disease. This study examined the distribution of two putative IL-4 promoter polymorphisms (-285 C-T and -81 A-G) in groups of patients with severe and moderate asthma, non-asthmatic atopy and control subjects. Neither polymorphism was identified in any of the samples tested. The data suggest that either the polymorphisms are present at very low frequencies or are artefacts of the B cell lines from which they were identified.  相似文献   
18.
Background:  Control of mRNA stability is an essential regulatory process in eukaryotic gene expression. HuR, a 3'UTR mRNA binding protein, can protect AU-rich mRNA from degradation in response to stresses. PlGF, an angiogenic growth factor, contains two consensus AU-rich sites suggesting that under normal conditions HuR may protect PlGF mRNA from degradation. Trophoblast expression of PlGF is significantly decreased in preeclampsia and by hypoxia in vitro . We hypothesize that decreased levels of cytoplasmic HuR may contribute to decreased PlGF expression in hypoxic and preeclamptic trophoblast.
Methods:  Western blots were used to determine relative effects of in vitro hypoxia on HuR protein expression and subcellular localization in trophoblast. Immunohistochemistry was used to compare HuR expression patterns in trophoblast of preeclamptic and normal placentae.
Results:  Cytoplasmic expression of HuR was decreased 1.4 fold in the cytoplasm and 1.2 fold in the nucleus of JEG3 cells. A shift in HuR was more apparent in primary trophoblast with a greater than 2-fold decrease in the cytoplasm and a 1.4 fold decrease in the nucleus following 24 hr of hypoxia. Immunohistochemical analyses detected HuR expression in near term trophoblast in situ . However, this technical approach did not detect a significant change in HuR expression between normal and preeclamptic trophoblast.
Conclusions:  HuR expression is decreased in hypoxic trophoblast, at least in vitro , which may provide a causal link to decreased PlGF mRNA expression. Down regulation of trophoblast PlGF expression is thought to contribute to the pathophysiology associated with preeclampsia including the relative lack of perfusion of the placenta and systemic renal effects.  相似文献   
19.
20.
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