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   578078篇
  免费   61616篇
  国内免费   9770篇
  649464篇
  2022年   5057篇
  2021年   9017篇
  2020年   6135篇
  2019年   7574篇
  2018年   8764篇
  2017年   7430篇
  2016年   10527篇
  2015年   15043篇
  2014年   17677篇
  2013年   21598篇
  2012年   25590篇
  2011年   25157篇
  2010年   16267篇
  2009年   14808篇
  2008年   19978篇
  2007年   19848篇
  2006年   18370篇
  2005年   16709篇
  2004年   16256篇
  2003年   15154篇
  2002年   14394篇
  2001年   22197篇
  2000年   21826篇
  1999年   17710篇
  1998年   7008篇
  1997年   6943篇
  1996年   6569篇
  1995年   6238篇
  1994年   5885篇
  1993年   5697篇
  1992年   14138篇
  1991年   13846篇
  1990年   13426篇
  1989年   12860篇
  1988年   11880篇
  1987年   11235篇
  1986年   10618篇
  1985年   10411篇
  1984年   8482篇
  1983年   7395篇
  1982年   5532篇
  1979年   7944篇
  1978年   6387篇
  1977年   5693篇
  1976年   5310篇
  1975年   6244篇
  1974年   6836篇
  1973年   6644篇
  1972年   5994篇
  1971年   5585篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The neutrophil-stimulating properties of 38 S. aureus strains and 32 S. epidermidis strains were studied in the reaction of luminol-mediated chemiluminescence. All S. aureus strains and 29 S. epidermidis strains were found to possess neutrophil-stimulating activity, the mean activity index for S. aureus being significantly higher. The stimulating activity of the strains varied within a wide range (the variation coefficient was 120.0 +/- 21.9%) and did not correlate with the content of protein A in bacterial cells and the degree of their hydrophoby. The opsonization of staphylococci with normal human serum enhanced the neutrophil reaction 1.5- to 100-fold and simultaneously leveled out the chemiluminescence indices in experiments with different strains (the variation coefficient was 8.0 +/- 1.5%). The nature of the neutrophil-stimulating effect of staphylococci and its relationship to the exploratory reactions of phagocytes are discussed.  相似文献   
102.
103.
104.
105.
106.
107.
Samples of marine pleuston were collected from the sea-surface along considerable sections of the track of Eye of the Wind during its 2-year circumnavigational expedition 'Operation Drake' from November 1978 to October 1980. One hundred and eleven of the tow samples contained insects of the genus Halobates . They were assigned to four oceanic species: H. micans, H. sericeus, H. germanus and H. splendens; two coastal species: H. maculatus, H. princeps, and one undescribed species. Various development stages of the oceanic species were found. The locations, time of collection and surface temperatures where sea-skaters were collected are tabulated. Distributional boundaries and population densities of the oceanic species collected are discussed.  相似文献   
108.
A computer-assisted analysis of the spatial distribution of neurons having homogeneous characteristics is described in this paper. The camera lucida drawings of sections of a brain nucleus and the points representing the neurons labeled on the basis of a specific behavior of discharge rates were digitized on a personal computer Amiga 2000 or IBM compatible. Our software provided: a) the computerized, stereotaxically oriented reconstruction of the stored sections and of the plotted neurons; b) the identification within each section of the mass center (MC) of the units sharing a given behavior and of the area where the density of such neurons was maximal (MDA). The routine was tested on the spatial distribution of neuronal responses to serotonin in the lateral vestibular nucleus.  相似文献   
109.
110.
Rosette and single-element strain gauges were implanted on the tibia in 2 dogs and recordings were made during locomotion on a treadmill. At foot contact and during the swing phase of locomotion, bone strains were low and directions of the principal strains were variable. There was a large shift in the directions of the principal strains at the beginning of the stance phase and bone strains were considerably higher. Peak strain occurred midway through the stance phase. At that time, the maximum principal strain (tension) was directed upwards and anteriorly between 30 and 60 degrees with respect to the long axis of the tibia. These bone strain patterns in the dog are similar to those found in sheep while both differ markedly from those found in humans.  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