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   874篇
  免费   53篇
  2022年   11篇
  2021年   25篇
  2020年   10篇
  2019年   13篇
  2018年   20篇
  2017年   19篇
  2016年   14篇
  2015年   24篇
  2014年   41篇
  2013年   71篇
  2012年   73篇
  2011年   79篇
  2010年   29篇
  2009年   33篇
  2008年   43篇
  2007年   33篇
  2006年   36篇
  2005年   34篇
  2004年   39篇
  2003年   18篇
  2002年   17篇
  2001年   13篇
  2000年   16篇
  1999年   13篇
  1998年   8篇
  1997年   4篇
  1996年   4篇
  1992年   9篇
  1991年   12篇
  1990年   8篇
  1989年   16篇
  1988年   6篇
  1987年   6篇
  1986年   7篇
  1985年   10篇
  1984年   10篇
  1983年   5篇
  1982年   6篇
  1981年   5篇
  1980年   6篇
  1979年   9篇
  1977年   6篇
  1976年   7篇
  1975年   18篇
  1974年   15篇
  1973年   3篇
  1971年   3篇
  1970年   3篇
  1969年   2篇
  1967年   2篇
排序方式: 共有927条查询结果,搜索用时 15 毫秒
11.
Extract of alfalfa seed (ethanolic 50 % v/v) prevents the development of plaque formation and hyperlipidaemia in cholesterol fed rabbits. It inhibits the elevation of serum total cholesterol, triglycerides, phospholipids, LDL-cholesterol and total cholesterol/phospholipid ratio, while HDL-cholesterol/total cholesterol ratio increases, which is associated with a reduced incidence of atherosclerosis. Further reduction in total cholesterol and phospholipid contents of liver and heart muscle are suggestive of a beneficial role of the seed extract. The possible mechanisms of action are discussed.  相似文献   
12.
Identification and characterization of bacterial endophytes of rice   总被引:7,自引:0,他引:7  
We isolated seven different bacteria from rice seedlings grown from surface sterilized seeds. Three were associated with the rice seed husk and the other four were growing endophytically within the seed. Microscopic studies revealed that the endophytes were concentrated in the root stele region. Some of the bacteria exhibited strong anti-fungal activity against Rhizoctonia solani, Pythium myriotylum, Guamannomyces graminis and Heterobasidium annosum.  相似文献   
13.
14.
Isolation of the fibrinogen-binding region of platelet thrombospondin   总被引:11,自引:0,他引:11  
Purified platelet thrombospondin binds to immobilized fibrinogen if both Ca++ and Mg++ are present. Digestion of the purified molecule with thermolysin results in a limited number of discrete proteolytic fragments. When such digests are subjected to affinity chromatography on immobilized fibrinogen, only the fragments with Mr of 120,000 and 140,000 are specifically bound and subsequently eluted by the addition of EDTA to the column buffer. Examination by SDS-PAGE under both reducing and nonreducing conditions reveals that the fibrinogen-binding domain is derived from the region of the thrombospondin molecule containing the interchain disulfide bonds. The requirement for Ca++ and Mg++ for optimal binding to fibrinogen is also manifest by the Mr 120,000/140,000 thermolytic fragments.  相似文献   
15.
Extract of the flower Malva viscus conzattii (M. conzattii) was administered at a dose of 25/50 mg/day/animal to 30 healthy adult male gerbils and 30 adult male house rats to determine its effect on fertility. After 25 days' treatment fin l body weight, and the weights of testes, epididymides, seminal vesicles, and adrenal glands were measured. Testis, epididymides, and seminal vesicles were prepared for histological examination and total protein, RNA, sialic acid, and alkaline phosphatase activity were determined. Quantitative estimation of cholesterol was also made. While overall body weight remained stable during treatment, testicular weight in both animals was drastically decreased. A complete spermatogenic arrest in the testes was evident in house rats treated with 50 mg/day for 20 days and in the gerbil treated with 25 mg/day for 25 days. The seminiferous tubules showed marked degeneration, lined by 1 or 2 cell layers. Epididymides showed degenerative changes as well. RNA contents of the testes, epididydmides, and seminal vesicles of treated anials were significantly lowered as was sialilc acid content. Total cholesterol was increased significantly. M. conzattii causes an effective inhibition of spermatogenesis in gerbils and house rats in 25 states and induces infertility.  相似文献   
16.
M Arya  S Gupta  V P Dixit 《Acta anatomica》1979,103(3):259-265
Effects of cyproterone acetate, a synthetic steroidal compound, on the reproductive organs of female rats have been investigated. This agent caused reduction of ovarian weights indicative of suppression of pituitary gonadotrophins. Oestrogenic nature of cyproterone acetate was investigated in intact and ovariectomized rats taking uterine weight and vaginal keratinization as an index of oestrogenicity. Cyproterone acetate in ovariectomized animals induced vaginal keratinization and increased the uterine weights. These effects were parallel to the effect of oestradiol dipropionate in ovariectomized animals, thus indicating oestrogenic activity of cyproterone acetate. We may conclude that the above compound caused antifertility effects due to its oestrogenic nature at the dose level of 2 mg/alternate day in rats when the compound was administered subcutaneously.  相似文献   
17.
There exist two distinct thrombospondin molecules (designated TSP1 and TSP2) which are encoded by separate genes. TSP1 is a trimeric cell surface and extracellular matrix molecule. Sequence comparison reveals that the 2 cysteines involved in interchain disulfide linkage and trimer assembly in TSP1 are conserved in TSP2 (Laherty, C. D., O'Rourke, K., Wolf, F. W., Katz, R., Seldin, M. F., and Dixit, V. M. (1992) J. Biol. Chem. 267, 3274-3281). Swiss 3T3 fibroblasts express both TSP1 and TSP2, and, therefore, an important question is whether TSP in such cells is expressed as homotrimers or as heterotrimers. We find that Swiss 3T3 cells and epithelial cells transfected with TSP expression vectors express both homo- and heterotrimeric forms of TSP. In addition, homotrimeric TSP2 has a lower affinity for heparin than homotrimeric TSP1. Thus, the heparin affinity of TSP can be modulated by the expression of TSP as homo- or heterotrimers.  相似文献   
18.
1. Goitrogenic action of methallibure (ICI-33828) has been studied in mice gerbil and hedgehog using thyroid weight and histological structure as an index. Liquefaction and vacuolation of thyroid follicles were most prevelant after methallibure administration. 2. The I131 content of the thyroid gland was significantly higher in the methallibure treated groups than in the controls. This denotes a decrease in the rate of discharge of thyroid hormone. 3. Protein bound radioiodine (Pb I131) was low after methallibure administration. 4. Methallibure administration brings about hypertrophy of pituitary thyrotrophs which is also reflected in the increased basophilic cell percentage in gerbil (control: 15.5 percent; methallibure: 22.8 percent). 5. It is concluded that methallibure acts on thyroid function both by a direct effect on the gland as well as by influencing pituitary thyrotrophic activity in enhancing I131 uptake.  相似文献   
19.
20.
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