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   335822篇
  免费   22777篇
  国内免费   1145篇
  359744篇
  2018年   14129篇
  2017年   12955篇
  2016年   10668篇
  2015年   4237篇
  2014年   4863篇
  2013年   6849篇
  2012年   11313篇
  2011年   20394篇
  2010年   17072篇
  2009年   12757篇
  2008年   16410篇
  2007年   18146篇
  2006年   6990篇
  2005年   6917篇
  2004年   7279篇
  2003年   7168篇
  2002年   6786篇
  2001年   12266篇
  2000年   12131篇
  1999年   9176篇
  1998年   2683篇
  1997年   2770篇
  1996年   2707篇
  1995年   2480篇
  1994年   2429篇
  1993年   2347篇
  1992年   7201篇
  1991年   7023篇
  1990年   7078篇
  1989年   6859篇
  1988年   6389篇
  1987年   6037篇
  1986年   5375篇
  1985年   5671篇
  1984年   4479篇
  1983年   3884篇
  1982年   2676篇
  1981年   2495篇
  1980年   2306篇
  1979年   4111篇
  1978年   3138篇
  1977年   2885篇
  1976年   2832篇
  1975年   3277篇
  1974年   3500篇
  1973年   3529篇
  1972年   3298篇
  1971年   3107篇
  1970年   2540篇
  1969年   2305篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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   
42.
43.
Galactose- and inositol-binding proteins with lectin activity (GL-GAL and GL-I, respectively) were isolated from membranes enriched with cells of chicken brain fractions. Both lectins are glycoproteins of molecular mass 13.5 and 11.5 kDa, respectively; they show a high affinity to EDTA (GL-I) and EGTA (GL-GAL, GL-I), which indicates an important role of Ca+2 in molecular organization of these lectins. In brain glial cells of chick embryos, unlike adult chickens, a soluble form of lectins has been revealed; it is easily extracted with 2 mM EDTA and shows sensitivity to L-lactose, D-galactose, and N-acetyl-D-galactosamine. It is suggested that in the course of embryonal and postembryonal development of the chicken brain, a transformation and qualitative changes of the lectin spectrum occur due to a change of function of glial cells.  相似文献   
44.
45.
46.
47.
48.
A rational attempt to prepare FmocHis(piTrt)OH regiospecifically gave in fact the well-known tau-trityl isomer, and experiments with model systems indicate that the prospects for access to pi-trityl histidine derivatives, which would be of great value for the racemization-free synthesis of histidine-containing peptides, are poor.  相似文献   
49.
50.
A comparative study of dark respiration and effects of high and low temperature on dark respiration in five greenhouse cultivated tropical and sub-tropical species was made. The respiration rates determined manometrically were low in all species. Respiration rates increased with increasing temperature. Low temperature treatment accelerated the rate of respiration at 25 °G except in two species. An attempt has been made to determine the critical and optimum temperature for these species. The respiratory behaviour of these species has been discussed with respect to their original habitats and prevailing environmental conditions.  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