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   11741篇
  免费   726篇
  国内免费   5篇
  2023年   107篇
  2022年   92篇
  2021年   180篇
  2020年   191篇
  2019年   181篇
  2018年   409篇
  2017年   375篇
  2016年   499篇
  2015年   741篇
  2014年   734篇
  2013年   893篇
  2012年   1073篇
  2011年   922篇
  2010年   595篇
  2009年   395篇
  2008年   718篇
  2007年   629篇
  2006年   581篇
  2005年   503篇
  2004年   445篇
  2003年   403篇
  2002年   366篇
  2001年   162篇
  2000年   153篇
  1999年   106篇
  1998年   74篇
  1997年   41篇
  1996年   58篇
  1995年   58篇
  1994年   35篇
  1993年   40篇
  1992年   73篇
  1991年   58篇
  1990年   51篇
  1989年   38篇
  1988年   41篇
  1987年   44篇
  1986年   28篇
  1985年   52篇
  1984年   37篇
  1983年   18篇
  1982年   24篇
  1981年   21篇
  1980年   23篇
  1979年   23篇
  1978年   22篇
  1977年   23篇
  1975年   17篇
  1974年   14篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 47 毫秒
1.
Four new species ofCayaponia are described and illustrated: three from Brazil (C. cogniauxiana, C. nitida andC. rugosa) and one from Brazil and Bolivia (C. ferruginea).  相似文献   
2.
A formalin-fixed paraffin-embedded (FFPE) sample usually yields highly degraded DNA, which limits the use of techniques requiring high-quality DNA, such as Infinium Methylation microarrays. To overcome this restriction, we have applied an FFPE restoration procedure consisting of DNA repair and ligation processes in a set of paired fresh-frozen (FF) and FFPE samples. We validated the FFPE results in comparison with matched FF samples, enabling us to use FFPE samples on the Infinium HumanMethylation450 Methylation array.  相似文献   
3.
4.
5.
6.
7.
8.
Biomechanics and Modeling in Mechanobiology - The goal of this work is to assess the impact of vascular anatomy definition degree in the predictions of blood flow models of the arterial network. To...  相似文献   
9.
Assessing small mammal diversity is a common procedure, which usually employs widespread standard techniques, for gathering information for a wide range of studies. Traditional methods, however, may be biased against capturing arboreal marsupials, such as Dromiciops gliroides, an endemic marsupial currently considered a rare species in the Patagonian temperate rainforest due to the low abundances reported previously. I tested a new capturing methodology to assess the small mammal diversity of an old-growth forest in Patagonia, based on a randomized and balanced design, which incorporated a combination of different trap types, bait types, and placement heights. The proposed methodology included four trap types (two for live-capturing: wire-mesh and Sherman traps, and two sign-recording traps for tracks and hair), two types of bait (banana and rolled oats), and two trap placements (ground level and 1.5–2.5 m above the ground). Trap type, bait type, and height of placement all had significantly different effects on capturing and detecting rodents or marsupials; environmental variables at the trap location also affected the ability to detect rodents and marsupials. Traditional methods used for sampling small mammals performed well for rodents but are not effective for capturing marsupials and vice versa, showing species-specific sampling protocols. There is no single combination of trap-bait-height capable to assess the entire small mammal community, but the combination of the most effective protocol for rodents and the most effective protocol for marsupials guarantee better results.  相似文献   
10.
How often will elections end in landslides? What is the probability for a head-to-head race? Analyzing ballot results from several large countries rather anomalous and yet unexplained distributions have been observed. We identify tactical voting as the driving ingredient for the anomalies and introduce a model to study its effect on plurality elections, characterized by the relative strength of the feedback from polls and the pairwise interaction between individuals in the society. With this model it becomes possible to explain the polarization of votes between two candidates, understand the small margin of victories frequently observed for different elections, and analyze the polls'' impact in American, Canadian, and Brazilian ballots. Moreover, the model reproduces, quantitatively, the distribution of votes obtained in the Brazilian mayor elections with two, three, and four candidates.  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