首页 | 官方网站   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   137篇
  免费   3篇
自然科学   140篇
  2021年   1篇
  2020年   1篇
  2019年   2篇
  2018年   7篇
  2017年   11篇
  2016年   1篇
  2015年   4篇
  2014年   2篇
  2013年   2篇
  2012年   10篇
  2011年   15篇
  2010年   2篇
  2008年   3篇
  2007年   6篇
  2006年   7篇
  2005年   6篇
  2004年   2篇
  2003年   4篇
  2002年   6篇
  2001年   5篇
  2000年   6篇
  1999年   4篇
  1992年   2篇
  1990年   1篇
  1988年   1篇
  1986年   2篇
  1984年   1篇
  1983年   1篇
  1980年   2篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1974年   4篇
  1973年   1篇
  1971年   1篇
  1970年   2篇
  1968年   4篇
  1965年   5篇
  1963年   1篇
  1961年   1篇
  1957年   1篇
排序方式: 共有140条查询结果,搜索用时 15 毫秒
101.
Zusammenfassung Ein salinischer Extrakt desCorpus pineale erzeugt bei normalen, nicht aber bei adrenalektomierten Ratten eine starke Retention von Natrium. Auf Grund der besonderen anatomischen Verhältnisse des Corpus pineale der Ratte vertreten wir die Auffassung, dass die wirksame Substanz, wahrscheinlich Adrenoglomerulotropin, in der Zirbeldrüse selbst erzeugt wird und nicht aus der Nachbarschaft dort angereichert wird.  相似文献   
102.
RNA interference (RNAi) regulates gene expression by the cleavage of messenger RNA, by mRNA degradation and by preventing protein synthesis. These effects are mediated by a ribonucleoprotein complex known as RISC (RNA-induced silencing complex). We have previously identified four Drosophila components (short interfering RNAs, Argonaute 2 (ref. 2), VIG and FXR) of a RISC enzyme that degrades specific mRNAs in response to a double-stranded-RNA trigger. Here we show that Tudor-SN (tudor staphylococcal nuclease)--a protein containing five staphylococcal/micrococcal nuclease domains and a tudor domain--is a component of the RISC enzyme in Caenorhabditis elegans, Drosophila and mammals. Although Tudor-SN contains non-canonical active-site sequences, we show that purified Tudor-SN exhibits nuclease activity similar to that of other staphylococcal nucleases. Notably, both purified Tudor-SN and RISC are inhibited by a specific competitive inhibitor of micrococcal nuclease. Tudor-SN is the first RISC subunit to be identified that contains a recognizable nuclease domain, and could therefore contribute to the RNA degradation observed in RNAi.  相似文献   
103.
Silva AJ  Josselyn SA 《Nature》2002,418(6901):929-930
  相似文献   
104.
105.
106.
107.
Breast cancer is the most common cancer among women. To date, 22 common breast cancer susceptibility loci have been identified accounting for ~8% of the heritability of the disease. We attempted to replicate 72 promising associations from two independent genome-wide association studies (GWAS) in ~70,000 cases and ~68,000 controls from 41 case-control studies and 9 breast cancer GWAS. We identified three new breast cancer risk loci at 12p11 (rs10771399; P = 2.7 × 10(-35)), 12q24 (rs1292011; P = 4.3 × 10(-19)) and 21q21 (rs2823093; P = 1.1 × 10(-12)). rs10771399 was associated with similar relative risks for both estrogen receptor (ER)-negative and ER-positive breast cancer, whereas the other two loci were associated only with ER-positive disease. Two of the loci lie in regions that contain strong plausible candidate genes: PTHLH (12p11) has a crucial role in mammary gland development and the establishment of bone metastasis in breast cancer, and NRIP1 (21q21) encodes an ER cofactor and has a role in the regulation of breast cancer cell growth.  相似文献   
108.
We consider a forecasting problem that arises when an intervention is expected to occur on an economic system during the forecast horizon. The time series model employed is seen as a statistical device that serves to capture the empirical regularities of the observed data on the variables of the system without relying on a particular theoretical structure. Either the deterministic or the stochastic structure of a vector autoregressive error correction model of the system is assumed to be affected by the intervention. The information about the intervention effect is just provided by some linear restrictions imposed on the future values of the variables involved. Formulas for restricted forecasts with intervention effects and their mean squared errors are derived as a particular case of Catlin's static updating theorem. An empirical illustration uses Mexican macroeconomic data on five variables and the restricted forecasts consider targets for years 2011–2014. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
109.
A resource for large-scale RNA-interference-based screens in mammals   总被引:2,自引:0,他引:2  
Gene silencing by RNA interference (RNAi) in mammalian cells using small interfering RNAs (siRNAs) and short hairpin RNAs (shRNAs) has become a valuable genetic tool. Here, we report the construction and application of a shRNA expression library targeting 9,610 human and 5,563 mouse genes. This library is presently composed of about 28,000 sequence-verified shRNA expression cassettes contained within multi-functional vectors, which permit shRNA cassettes to be packaged in retroviruses, tracked in mixed cell populations by means of DNA 'bar codes', and shuttled to customized vectors by bacterial mating. In order to validate the library, we used a genetic screen designed to report defects in human proteasome function. Our results suggest that our large-scale RNAi library can be used in specific, genetic applications in mammals, and will become a valuable resource for gene analysis and discovery.  相似文献   
110.
High-percent mammographic density adjusted for age and body mass index is one of the strongest risk factors for breast cancer. We conducted a meta analysis of five genome-wide association studies of percent mammographic density and report an association with rs10995190 in ZNF365 (combined P = 9.6 × 10(-10)). Common variants in ZNF365 have also recently been associated with susceptibility to breast cancer.  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-23

京公网安备 11010802026262号