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   3247948篇
  免费   238686篇
  国内免费   5594篇
耳鼻咽喉   47272篇
儿科学   103152篇
妇产科学   86730篇
基础医学   455385篇
口腔科学   93706篇
临床医学   292731篇
内科学   623779篇
皮肤病学   68942篇
神经病学   262450篇
特种医学   131273篇
外国民族医学   1147篇
外科学   491239篇
综合类   72827篇
现状与发展   2篇
一般理论   1196篇
预防医学   255545篇
眼科学   76697篇
药学   246402篇
  13篇
中国医学   6470篇
肿瘤学   175270篇
  2018年   34650篇
  2017年   27755篇
  2016年   29823篇
  2015年   34472篇
  2014年   47081篇
  2013年   68620篇
  2012年   96779篇
  2011年   97998篇
  2010年   57427篇
  2009年   55898篇
  2008年   90632篇
  2007年   97338篇
  2006年   98736篇
  2005年   102034篇
  2004年   100006篇
  2003年   93141篇
  2002年   87724篇
  2001年   151041篇
  2000年   155260篇
  1999年   132847篇
  1998年   36724篇
  1997年   32950篇
  1996年   32779篇
  1995年   31420篇
  1994年   29354篇
  1993年   27441篇
  1992年   107220篇
  1991年   103925篇
  1990年   101068篇
  1989年   97659篇
  1988年   90307篇
  1987年   88458篇
  1986年   84058篇
  1985年   79874篇
  1984年   59616篇
  1983年   50592篇
  1982年   29563篇
  1981年   26064篇
  1979年   55846篇
  1978年   38582篇
  1977年   33077篇
  1976年   30345篇
  1975年   33189篇
  1974年   40520篇
  1973年   38380篇
  1972年   36321篇
  1971年   33927篇
  1970年   31898篇
  1969年   29947篇
  1968年   27089篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Geneticists have, for years, understood the nature of genome‐wide association studies using common genomic variants. Recently, however, focus has shifted to the analysis of rare variants. This presents potential problems for researchers, as rare variants do not always behave in the same way common variants do, sometimes rendering decades of solid intuition moot. In this paper, we present examples of the differences between common and rare variants. We show why one must be significantly more careful about the origin of rare variants, and how failing to do so can lead to highly inflated type I error. We then explain how to best avoid such concerns with careful understanding and study design. Additionally, we demonstrate that a seemingly low error rate in next‐generation sequencing can dramatically impact the false‐positive rate for rare variants. This is due to the fact that rare variants are, by definition, seen infrequently, making it hard to distinguish between errors and real variants. Compounding this problem is the fact that the proportion of errors is likely to get worse, not better, with increasing sample size. One cannot simply scale their way up in order to solve this problem. Understanding these potential pitfalls is a key step in successfully identifying true associations between rare variants and diseases.  相似文献   
72.
73.
74.
75.
The aim of the present study was to evaluate the antimicrobial activity of two synbiotic combinations, Lactobacillus fermentum with short-chain fructooligosaccharides (FOS-LF) and Bifidobacterium longum with isomaltooligosaccharides (IMO-BL), against enterohaemorrhagic Escherichia coli O157:H7 and enteropathogenic E. coli O86. Antimicrobial activity was determined (1) by co-culturing the synbiotics and pathogens in batch cultures, and (2) with the three-stage continuous culture system (gut model), inoculated with faecal slurry from an elderly donor. In the co-culture experiments, IMO-BL was significantly inhibitory to both E. coli strains, while FOS-LF was slightly inhibitory or not inhibitory. Factors other than acid production appeared to play a role in the inhibition. In the gut models, both synbiotics effectively inhibited E. coli O157 in the first vessel, but not in vessels 2 and 3. E. coli O86 was not significantly inhibited.  相似文献   
76.
Farnesyltransferase (FTase) is one of the prenyltransferase family enzymes that catalyse the transfer of 15-membered isoprenoid (farnesyl) moiety to the cysteine of CAAX motif-containing proteins including Rho and Ras family of G proteins. Inhibitors of FTase act as drugs for cancer, malaria, progeria and other diseases. In the present investigation, we have developed two structure-based pharmacophore models from protein–ligand complex (3E33 and 3E37) obtained from the protein data bank. Molecular dynamics (MD) simulations were performed on the complexes, and different conformers of the same complex were generated. These conformers were undergone protein–ligand interaction fingerprint (PLIF) analysis, and the fingerprint bits have been used for structure-based pharmacophore model development. The PLIF results showed that Lys164, Tyr166, TrpB106 and TyrB361 are the major interacting residues in both the complexes. The RMSD and RMSF analyses on the MD-simulated systems showed that the absence of FPP in the complex 3E37 has significant effect in the conformational changes of the ligands. During this conformational change, some interactions between the protein and the ligands are lost, but regained after some simulations (after 2 ns). The structure-based pharmacophore models showed that the hydrophobic and acceptor contours are predominantly present in the models. The pharmacophore models were validated using reference compounds, which significantly identified as HITs with smaller RMSD values. The developed structure-based pharmacophore models are significant, and the methodology used in this study is novel from the existing methods (the original X-ray crystallographic coordination of the ligands is used for the model building). In our study, along with the original coordination of the ligand, different conformers of the same complex (protein–ligand) are used. It concluded that the developed methodology is significant for the virtual screening of novel molecules on different targets.  相似文献   
77.
78.
79.
80.
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