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   12565篇
  免费   863篇
  国内免费   5篇
  13433篇
  2023年   81篇
  2022年   93篇
  2021年   205篇
  2020年   153篇
  2019年   172篇
  2018年   290篇
  2017年   248篇
  2016年   355篇
  2015年   599篇
  2014年   631篇
  2013年   842篇
  2012年   957篇
  2011年   934篇
  2010年   565篇
  2009年   480篇
  2008年   750篇
  2007年   730篇
  2006年   650篇
  2005年   638篇
  2004年   612篇
  2003年   561篇
  2002年   486篇
  2001年   234篇
  2000年   173篇
  1999年   166篇
  1998年   102篇
  1997年   85篇
  1996年   69篇
  1995年   74篇
  1994年   59篇
  1993年   57篇
  1992年   92篇
  1991年   74篇
  1990年   77篇
  1989年   65篇
  1988年   60篇
  1987年   55篇
  1986年   51篇
  1985年   65篇
  1984年   58篇
  1983年   44篇
  1982年   48篇
  1981年   57篇
  1980年   38篇
  1979年   63篇
  1978年   65篇
  1976年   40篇
  1975年   36篇
  1974年   49篇
  1971年   44篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
A comparison was made between a hay fed group, consisting of 23 ewes, and a grass silage fed group of 22 ewes, all pregnant. Excretion of Listeria monocytogenes (Lm) in the faeces and milk, antibody titres in sera and whey and delayed hypersensitivity against Lm, and several blood components were determined. The animals had previously been exposed to Lm, and Lm was isolated from the faeces from several animals when the experiment started. No significant difference in number of excretors between the 2 groups was found during the experimental period. The haemagglutination titres in both sera and whey were low and on the same level in both groups. The titres were higher in animals with 1 foetus than in animals with more than 1 foetus. In the first part of the experimental period the silage group had a reduced number of lymphocytes, lower total serum protein values and higher serum iron values, compared with the hay group. The silage group also had a stronger delayed hypersensitivity reaction against Lm than the hay group, and in the silage group the reaction was significantly stronger in ewes with 3 or more foetuses than in ewes with 1 foetus. In conclusion, the combined effect of some of the changes found in animals fed grass silage may leave them more susceptible to infections.  相似文献   
2.
G Gaál  E Bácsy  G Rappay 《Histochemistry》1988,88(3-6):401-406
Cultured cells from the anterior pituitary glands of adult rats were treated with the tripeptide aldehyde proteinase inhibitor, BOC-DPhe-Phe-Lys-H. The addition of this tripeptide aldehyde decreased the in vitro release of prolactin to 25% of the control value, while the release of growth hormone in the same cultures decreased to 33% of the control value. Prolactin immunostaining was stronger in semithin sections of proteinase-inhibitor-treated cultures than in control sections. After 2 h treatment with the inhibitor, prolactin- and growth hormone-containing secretory granules were numerous, and the number of crinophagic vacuoles had increased. In the presence of the inhibitor, the overall cytoarchitecture of parenchymal cells was well preserved, and the pathway of the uptake of cationic ferritin appeared to be unaffected.  相似文献   
3.
4.
5.
6.
Monoclonal antibodies were produced to electrophoretically pure hydrogenase fromThiocapsa roseopersicina. Protein immunoelectroblotting was used to identify the hydrogenase-specific antibodies. Among the 18 monoclonal antibodies selected by enzyme immunoassay, three were found to react with highly immunogenic trace contaminating proteins. One cell line produced antibody that inhibitied hydrogenase activity. This was the first specific inhibitor of the hydrogenase function. The results suggest that monoclonal antibodies could provide valuable new informations about the enzyme structure as well.  相似文献   
7.
8.
A major haemophiliac A, 27 years old, has been treated during 30 months, with high dosage of imported Factor VIII, in order to reduce the titer of a F VIII antibody. A good clinical result has been obtained. No sign of immunodeficiency has been observed. Normal values were obtained for T4/T8, ratio B2 microglobulin and no antibody was detected against the LAV virus isolated from cases of AIDS.  相似文献   
9.
To determine if human XX maleness results from an abnormal chromosomal X-Y interchange, we studied the inheritance of the paternal pseudoautosomal region in nine patients. Those six patients in whom Y-specific DNA was found (Y(+)) inherited the entire pseudoautosomal region from the paternal Y chromosome and lost that of the paternal X chromosome. Moreover, in three Y(+) cases, we observed the deletion of a paternal Xp locus tightly linked to the pseudoautosomal region. These results definitively show that an abnormal and terminal X-Y interchange during paternal meiosis causes Y(+)XX maleness. In contrast, no abnormal X-Y interchange was observed in any of the three Y(-) cases analyzed, suggesting that maleness can occur in the absence of any Y-specific DNA.  相似文献   
10.
Summary A sample of 235 individuals from 49 French cystic fibrosis (CF) families with at least one living affected child was typed with probes for restriction fragment length polymorphisms (RFLPs) known to be linked to the CF gene, and was screened for the ΔF508 mutation. Using a combination of six probes, 44 out of the 49 families were sufficiently informative to enable prenatal diagnosis or carrier determination. As in many other populations, linkage disequilibrium was found between the CF locus and the haplotype B (XV2c: allele 1; KM19: allele 2), which accounts for about 78% of CF chromosomes in our families. The ΔF508 deletion was present in 64.3% of CF chromosomes.  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