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   20730篇
  免费   2403篇
  国内免费   4篇
  2021年   254篇
  2019年   163篇
  2018年   204篇
  2017年   208篇
  2016年   323篇
  2015年   501篇
  2014年   628篇
  2013年   783篇
  2012年   933篇
  2011年   976篇
  2010年   644篇
  2009年   561篇
  2008年   799篇
  2007年   859篇
  2006年   806篇
  2005年   746篇
  2004年   744篇
  2003年   722篇
  2002年   672篇
  2001年   594篇
  2000年   608篇
  1999年   542篇
  1998年   339篇
  1997年   258篇
  1996年   256篇
  1995年   226篇
  1994年   218篇
  1993年   240篇
  1992年   443篇
  1991年   373篇
  1990年   405篇
  1989年   332篇
  1988年   382篇
  1987年   367篇
  1986年   297篇
  1985年   352篇
  1984年   281篇
  1983年   280篇
  1982年   257篇
  1981年   226篇
  1980年   213篇
  1979年   278篇
  1978年   237篇
  1977年   225篇
  1976年   224篇
  1975年   205篇
  1974年   218篇
  1973年   210篇
  1972年   203篇
  1971年   169篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The rat optic nerve is a useful model for stem cell regeneration research. Direct injection into the rat optic nerve allows delivery into the central nervous system in a minimally-invasive surgery without bone removal. This technique describes an approach to visualization and direct injection of the optic nerve following minor fascial dissection from the orbital ridge, using a conjunctival traction suture to gently pull the eye down and out. Representative examples of an injected optic nerve show successful injection of dyed beads.  相似文献   
52.
53.
The cold-shock response — a hot topic   总被引:4,自引:2,他引:2  
  相似文献   
54.
55.
56.
57.
Techniques are described for capturing and marking redtail monkeys (Cercopithecus ascanius). An air-powered darting rifle and syringe darts loaded with a Ketamine-Rompun mixture were used for capture. Ketamine was used for maintaining anesthesia. Monkeys were darted 48 times and captured 27 times. In 24 of the 27 captures, the monkeys were released unharmed. Adult males were marked with radiotransmitters attached to collars of nylon webbing. Females received nylon webbing collars with colorcoded plastic washers for identification.  相似文献   
58.
59.
Despite the efficacy of antiretroviral-based pre-exposure prophylactics (PrEP) in men who have sex with men, studies in women have produced widely varying outcomes. Recent evidence demonstrates that vaginal microbial communities are associated with increased HIV acquisition risk and may impact PrEP efficacy. Here, we investigate the mechanisms underlying how vaginal bacteria alter PrEP drug levels and impact HIV infection rates ex vivo. Using cervicovaginal lavages (CVLs) from women with or without bacterial vaginosis (BV), we identified microbial metabolism of PrEP drugs in BV samples through LC-MS/MS analysis of soluble drug levels and metabolite formation in dual T-cell cultures. CVL samples were assessed for microbiome analysis using sequencing of bacterial 16S rRNA genes. We also observed non-Lactobacillus bacteria that are associated with BV may potentially impact PrEP efficacy through increased HIV infection rates in co-cultures containing Lactobacillus or BV bacteria, PrEP drugs, CEM-GFP cells, and HIV-1LAI virus. Finally, we used these data to develop a novel predictive mathematical simulation modeling system to predict these drug interactions for future trials. These studies demonstrate how dysbiotic vaginal microbiota may impact PrEP drugs and provides evidence linking vaginal bacteria to PrEP efficacy in women.  相似文献   
60.
Major and minor electrophoretic variants of juvenile hormone esterase (JHE) were found in the hemolymph of last instar larvae of Trichoplusia ni, both before and after metamorphic commitment. The average ratios of activity of the two major forms were similar during both last stadium peaks in activity. Immunological analysis showed that the hemolymph concentration of JHE during this stadium paralleled the level of enzymatic activity, and no putative higher molecular weight, inactive forms were detected. Immunological analysis provided the first evidence of relatedness of major and minor forms. After hormonal stimulation, the concentration of the two major forms increased concomitantly and by a similar proportion, suggesting that charge variation, at least for these two major forms, is not a point of hormonal or developmental regulation of JHE.  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