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   1629篇
  免费   137篇
  国内免费   5篇
  2024年   2篇
  2023年   24篇
  2022年   46篇
  2021年   91篇
  2020年   49篇
  2019年   53篇
  2018年   56篇
  2017年   47篇
  2016年   67篇
  2015年   117篇
  2014年   120篇
  2013年   146篇
  2012年   168篇
  2011年   139篇
  2010年   79篇
  2009年   68篇
  2008年   76篇
  2007年   65篇
  2006年   63篇
  2005年   45篇
  2004年   55篇
  2003年   39篇
  2002年   26篇
  2001年   16篇
  2000年   9篇
  1999年   24篇
  1998年   6篇
  1997年   4篇
  1995年   1篇
  1994年   4篇
  1993年   1篇
  1992年   6篇
  1991年   7篇
  1990年   2篇
  1989年   8篇
  1988年   2篇
  1987年   6篇
  1986年   8篇
  1985年   2篇
  1984年   4篇
  1983年   5篇
  1982年   4篇
  1981年   2篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1972年   1篇
  1936年   1篇
排序方式: 共有1771条查询结果,搜索用时 140 毫秒
31.
32.
33.
Dissecting the genetic basis of intraspecific variations in life history traits is essential to understand their evolution, notably for potential biocontrol agents. Such variations are observed in the endoparasitoid Cotesia typhae (Hymenoptera: Braconidae), specialized on the pest Sesamia nonagrioides (Lepidoptera: Noctuidae). Previously, we identified two strains of C. typhae that differed significantly for life history traits on an allopatric host population. To investigate the genetic basis underlying these phenotypic differences, we used a quantitative trait locus (QTL) approach based on restriction site‐associated DNA markers. The characteristic of C. typhae reproduction allowed us generating sisters sharing almost the same genetic content, named clonal sibship. Crosses between individuals from the two strains were performed to generate F2 and F8 recombinant CSS. The genotypes of 181 clonal sibships were determined as well as the phenotypes of the corresponding 4,000 females. Informative markers were then used to build a high‐quality genetic map. These 465 markers spanned a total length of 1,300 cM and were organized in 10 linkage groups which corresponded to the number of C. typhae chromosomes. Three QTLs were detected for parasitism success and two for offspring number, while none were identified for sex ratio. The QTLs explained, respectively, 27.7% and 24.5% of the phenotypic variation observed. The gene content of the genomic intervals was investigated based on the genome of C. congregata and revealed 67 interesting candidates, as potentially involved in the studied traits, including components of the venom and of the symbiotic virus (bracovirus) shown to be necessary for parasitism success in related wasps.  相似文献   
34.
Plant and Soil - Contrasting nutrient-acquisition strategies would explain why species differ in their distribution in relation to soil phosphorus (P) availability, promoting diversity. However,...  相似文献   
35.
36.
37.
Molecular Biology Reports - Western flower thrips, Frankliniella occidentalis is an economically important agricultural pest. It causes damage by feeding and oviposition or indirectly by plant...  相似文献   
38.
The International Journal of Life Cycle Assessment - In this paper, we present new tools to ease the analysis of the effect of variability and uncertainty on life cycle assessment (LCA) results....  相似文献   
39.
In studies based on electronic health records (EHR), the frequency of covariate monitoring can vary by covariate type, across patients, and over time, which can limit the generalizability of inferences about the effects of adaptive treatment strategies. In addition, monitoring is a health intervention in itself with costs and benefits, and stakeholders may be interested in the effect of monitoring when adopting adaptive treatment strategies. This paper demonstrates how to exploit nonsystematic covariate monitoring in EHR‐based studies to both improve the generalizability of causal inferences and to evaluate the health impact of monitoring when evaluating adaptive treatment strategies. Using a real world, EHR‐based, comparative effectiveness research (CER) study of patients with type II diabetes mellitus, we illustrate how the evaluation of joint dynamic treatment and static monitoring interventions can improve CER evidence and describe two alternate estimation approaches based on inverse probability weighting (IPW). First, we demonstrate the poor performance of the standard estimator of the effects of joint treatment‐monitoring interventions, due to a large decrease in data support and concerns over finite‐sample bias from near‐violations of the positivity assumption (PA) for the monitoring process. Second, we detail an alternate IPW estimator using a no direct effect assumption. We demonstrate that this estimator can improve efficiency but at the potential cost of increase in bias from violations of the PA for the treatment process.  相似文献   
40.
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