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   8306篇
  免费   713篇
  国内免费   2篇
  2023年   16篇
  2022年   54篇
  2021年   138篇
  2020年   99篇
  2019年   107篇
  2018年   161篇
  2017年   130篇
  2016年   232篇
  2015年   353篇
  2014年   360篇
  2013年   588篇
  2012年   647篇
  2011年   651篇
  2010年   410篇
  2009年   379篇
  2008年   533篇
  2007年   552篇
  2006年   524篇
  2005年   473篇
  2004年   418篇
  2003年   432篇
  2002年   449篇
  2001年   82篇
  2000年   63篇
  1999年   92篇
  1998年   109篇
  1997年   61篇
  1996年   72篇
  1995年   63篇
  1994年   63篇
  1993年   50篇
  1992年   49篇
  1991年   32篇
  1990年   48篇
  1989年   35篇
  1988年   28篇
  1987年   24篇
  1986年   21篇
  1985年   24篇
  1984年   28篇
  1983年   21篇
  1982年   25篇
  1981年   26篇
  1979年   22篇
  1978年   20篇
  1977年   22篇
  1976年   23篇
  1975年   16篇
  1974年   21篇
  1972年   19篇
排序方式: 共有9021条查询结果,搜索用时 15 毫秒
1.

Backgound  

It has been reported that Toll-like receptor 4 (TLR4) deficiency reduces infarct size after myocardial ischemia/reperfusion (MI/R). However, measurement of MI/R injury was limited and did not include cardiac function. In a chronic closed-chest model we assessed whether cardiac function is preserved in TLR4-deficient mice (C3H/HeJ) following MI/R, and whether myocardial and systemic cytokine expression differed compared to wild type (WT).  相似文献   
2.
Orientation of optically nonlinear organic molecules inside sol-gel matrices upon application of an external D.C. electrical field is demonstrated for the first time. The quadratic nonlinear response of silicon oxide or transition metal oxide based gels containing organic molecules has been determined from Electric Field Induced Second Harmonic (EFISH) measurements. Large concentrations of Optically Nonlinear Organic Molecules (ONOM) have been either incorporated inside the macromolecular network or chemically bonded to the oxide backbone of the gels. These results demonstrate the feasibility of permanently poled doped sol-gel matrices. Moreover, EFISH measurements performed on organic molecules appear to be a useful tool for monitoring the changes occurring during sol-gel transformations.  相似文献   
3.
4.

Background  

It has long been known that rates of synonymous substitutions are unusually low in mitochondrial genes of flowering and other land plants. Although two dramatic exceptions to this pattern have recently been reported, it is unclear how often major increases in substitution rates occur during plant mitochondrial evolution and what the overall magnitude of substitution rate variation is across plants.  相似文献   
5.
6.
7.
Thermosensation provides vital inputs for the malaria vector mosquito, Anopheles gambiae which utilizes heat-sensitivity within a broad spectrum of behaviors, most notably, the localization of human hosts for blood feeding. In this study, we examine thermosensory behaviors in larval-stage An. gambiae, which as a result of their obligate aquatic habitats and importance for vectorial capacity, represents an opportunistic target for vector control as part of the global campaign to eliminate malaria. As is the case for adults, immature mosquitoes respond differentially to a diverse array of external heat stimuli. In addition, larvae exhibit a striking phenotypic plasticity in thermal-driven behaviors that are established by temperature at which embryonic development occurs. Within this spectrum, RNAi-directed gene-silencing studies provide evidence for the essential role of the Transient Receptor Potential sub-family A1 (TRPA1) channel in mediating larval thermal-induced locomotion and thermal preference within a discrete upper range of ambient temperatures.  相似文献   
8.
Notes that augment an earlier essay on R. S. Williams’ botanical activities and the distribution of his collections from Bolivia and Peru are presented. Twelve species based on Williams’ vascular plant collections are added to a catalog that was previously published. Synonymies of an additional 22 taxa are corrected or updated. Notes also are provided concerning the typification or orthography of two species.  相似文献   
9.
The oncolytic peptide LTX-315 has been designed for killing human cancer cells and turned out to stimulate anti-cancer immune responses when locally injected into tumors established in immunocompetent mice. Here, we investigated the question whether LTX-315 induces apoptosis or necrosis. Transmission electron microscopy or morphometric analysis of chromatin-stained tumor cells revealed that LTX-315 failed to induce apoptotic nuclear condensation and rather induced a necrotic phenotype. Accordingly, LTX-315 failed to stimulate the activation of caspase-3, and inhibition of caspases by means of Z-VAD-fmk was unable to reduce cell killing by LTX-315. In addition, 2 prominent inhibitors of regulated necrosis (necroptosis), namely, necrostatin-1 and cycosporin A, failed to reduce LTX-315-induced cell death. In conclusion, it appears that LTX-315 triggers unregulated necrosis, which may contribute to its pro-inflammatory and pro-immune effects.  相似文献   
10.
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