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   1080篇
  免费   133篇
  国内免费   4篇
  1217篇
  2022年   10篇
  2021年   9篇
  2020年   8篇
  2019年   14篇
  2018年   16篇
  2017年   12篇
  2016年   25篇
  2015年   44篇
  2014年   32篇
  2013年   40篇
  2012年   52篇
  2011年   55篇
  2010年   30篇
  2009年   45篇
  2008年   59篇
  2007年   40篇
  2006年   49篇
  2005年   43篇
  2004年   46篇
  2003年   47篇
  2002年   51篇
  2001年   39篇
  2000年   45篇
  1999年   34篇
  1998年   17篇
  1997年   11篇
  1996年   13篇
  1995年   8篇
  1994年   14篇
  1993年   8篇
  1992年   23篇
  1991年   13篇
  1990年   27篇
  1989年   9篇
  1988年   8篇
  1987年   17篇
  1986年   13篇
  1985年   16篇
  1983年   12篇
  1981年   8篇
  1980年   7篇
  1979年   8篇
  1978年   9篇
  1977年   8篇
  1975年   9篇
  1974年   8篇
  1973年   8篇
  1970年   11篇
  1967年   7篇
  1962年   6篇
排序方式: 共有1217条查询结果,搜索用时 15 毫秒
1.
2.
The study tested the proposition that relationship involvement influences the implicit responses of women to high- and low-status professions. It was hypothesized that when a high-involvement context was primed, women would have more positive implicit associations with high-status occupations than when a low-involvement context was primed. In contrast, when a high-involvement context was primed, women would have more negative associations with low-status occupations than when a low-involvement context was primed. To test the hypothesis, 123 female participants received a high or low relationship involvement prime. Then the participants completed a single category implicit associations test designed to measure the participants' associations with either high- or low-status occupations. As predicted, the relationship involvement prime influenced the positivity of associations made with high- and low-status occupations. The study pointed to the possibility that persons possess evolutionary-based implicit associations.  相似文献   
3.
4.
5.
6.
S J Millar  D Dempsey  D P Dickinson 《BioTechniques》1992,13(4):554-6, 558-60, 562
Certain genomic sequences cannot be recovered efficiently in cosmid or lambda bacteriophage clones, presenting a barrier to efforts to construct a contiguous cloned library of a genome. We have encountered such sequences during our efforts to isolate cosmid and bacteriophage lambda clones carrying members of the human type 2 cystatin gene family. Several cosmid clones constructed in the pWE 15 vector did not survive purification, and using standard techniques, we were unable to obtain significant amounts of cosmid DNA from those clones we could purify. Similarly, several lambda bacteriophage clones constructed in the lambda DASH II vector could not be purified, and those lambda clones we were able to isolate gave low titers in liquid lysates. In this paper, we describe generally applicable methods for preparing high yields of recombinant DNA from such recalcitrant cosmid and lambda clones constructed in these vectors.  相似文献   
7.
We have constructed a library of recombinant phage containing DNA from salivary gland chromosomes of Rhynchosciara americana. We have isolated phage from this library that carry sequences homologous to cDNA clones that hybridize in situ to the DNA puffs at the polytene chromosome regions C3 and C8. This has enabled us to demonstrate a 16-fold amplification of the genomic DNA sequences at these regions during DNA-puffing. At the C8 site there is a sequence element that has characteristics of 'scrambled' moderately repetitive DNA. This is located within 3 kb from the gene encoding a 1.95-kb mRNA. We have assayed restriction fragments from the two DNA puffs for Ars activity in yeast. The only strong Ars activity is associated with a part of the moderately repetitive DNA element from the C8 puff which is not present at this site in all animals.  相似文献   
8.
9.
In rams a positive correlation (P less than 0.001) existed between average testosterone levels from 30-min blood sampling for 18 h and average testosterone levels of samples taken 0, 1 and 2 h after injection of LH-RH administered 90 min after anaesthesia. Attempts were therefore made to assess testosterone status by LH-RH challenge and limited blood sampling in animals immobilized in their natural habitat. In impala (Aepyceros melampus) territorial males had higher plasma testosterone values than did bachelors after LH-RH challenge (8.1 compared with 2.6 ng/ml, P less than 0.05). In blesbok (Damaliscus dorcas), the relationship was less clear, but testicular volume was correlated with plasma testosterone concentration and with testicular responsiveness measured by testosterone produced per unit of LH (P less than 0.001 and P less than 0.05, respectively). The LH-RH challenge technique therefore has value as a measure of testicular function and permits study of ungulates in their natural environment.  相似文献   
10.
Internal water balance of barley under soil moisture stress   总被引:1,自引:1,他引:0       下载免费PDF全文
Leaf water potential, leaf relative water content, and relative transpiration of barley were determined daily under greenhouse conditions at 3 growth stages: tillering to boot, boot to heading, and heading to maturity. The leaf moisture characteristic curve (relative water content versus leaf water potential) was the same for leaves of the same age growing in the same environment for the first 2 stages of growth, but shifted at the heading to maturity stage to higher leaf relative water content for a given leaf water potential. Growth chamber experiments showed that the leaf moisture characteristic curve was not the same for plants growing in different environments.

Relative transpiration data indicated that barley stomates closed at a water potential of about −22 bars at the 3 stages studied.

The water potential was measured for all the leaves on barley to determine the variation of water potential with leaf position. Leaf water potential increased basipetally with plant leaf position. In soil with a moisture content near field capacity a difference of about 16.5 bars was observed between the top and bottom leaves on the same plant, while in soil with a moisture content near the permanent wilting point the difference was only 5.6 bars between the same leaf positions.

  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