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   1517415篇
  免费   148214篇
  国内免费   1566篇
  2021年   18121篇
  2019年   16297篇
  2018年   18283篇
  2017年   17051篇
  2016年   28633篇
  2015年   42956篇
  2014年   51096篇
  2013年   77495篇
  2012年   42141篇
  2011年   31772篇
  2010年   45354篇
  2009年   46287篇
  2008年   29619篇
  2007年   27899篇
  2006年   32396篇
  2005年   33349篇
  2004年   32288篇
  2003年   30237篇
  2002年   28042篇
  2001年   42853篇
  2000年   40459篇
  1999年   38165篇
  1998年   26707篇
  1997年   26733篇
  1996年   26089篇
  1995年   24232篇
  1994年   23953篇
  1993年   23304篇
  1992年   33470篇
  1991年   31927篇
  1990年   30239篇
  1989年   30817篇
  1988年   28287篇
  1987年   27346篇
  1986年   25760篇
  1985年   27551篇
  1984年   26247篇
  1983年   23262篇
  1982年   22702篇
  1981年   21599篇
  1980年   20243篇
  1979年   22931篇
  1978年   20740篇
  1977年   19712篇
  1976年   18822篇
  1975年   18645篇
  1974年   19462篇
  1973年   19564篇
  1972年   16968篇
  1971年   15527篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Sulcal patterns of 14 genera of Old World monkeys were analyzed from 107 endocasts. Colobines and cercopithecines differ in patterns of cerebral convolutions, and functional and evolutionary hypotheses are here proposed regarding those differences. The cercopithecine pattern seems to be the more derived since it suggests relative expansion of prefrontal, and inferior temporal integration cortices as compared to the colobine pattern.  相似文献   
992.
A new method has been proposed for analysis of experimental data on ligand-receptor binding at equilibrium. This method makes it possible to detect heterogeneity of a receptor system in cases where the contribution of the high-affinity site to total binding is rather small and the problem of graphic discrimination of a model cannot be solved unambiguously by other methods. The difference method permits us to exclude experiments on measuring nonspecific binding. A computer program for analysis of ligand-receptor binding has been worked out in which the difference method and traditional methods of binding isotherm analysis are realized. Numerical modeling has shown that the best strategy in experimental data processing is the treatment of total binding isotherms by both the difference method and regression analysis, including the nonspecific binding constant as one of the regression parameters.  相似文献   
993.
A computer simulation model was developed to investigate nitrogenfluxes associated with microbial interactions in plankton communities.A short time scale was used, appropriate to the build-up anddecline of phytoplankton blooms in temperate shelf waters aftera mixing or upwelling event. The model depicts a continuum ofevents, many of which have been observed in coastal, upwellingand oceanic systems, including two phytoplankton peaks correspondingto ‘new production’ and ‘regenerated production’.It predicts that nitrogen loss through sedimentation of phytoplanktonand faeces may result in a smaller bloom with a delayed onsetand prolonged duration. Microbial regeneration of nitrogen wasfound to be important in sustaining the middle stages of a phytoplanktonbloom, whereas micro- and meso-zooplankton regeneration occurredtowards the end of the bloom.  相似文献   
994.
Volatiles from the epicuticular wax of watercress were collected by ether washing and examined using gas chromatographic and mass spectrometric analysi  相似文献   
995.
996.
The distribution of regular secondary structures, viz. α-helices and β-strands, along the length of over 70 properties whose secondary structural details have been reported, has been analysed. The occurrence of these regular structures tends to be a maximum at the N- and C-termini. Our analysis suggests that both these free ends could possibly serve as nucleating centers for secondary structures and could play an important role in the folding of proteins.  相似文献   
997.
The flavonoids of five Geranium, fourteen Erodium and four Monsonia species were studied. Quercetin was the most common aglycone with lesse  相似文献   
998.
999.
1000.
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