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   242970篇
  免费   16670篇
  国内免费   51篇
  259691篇
  2021年   1961篇
  2018年   3491篇
  2017年   3403篇
  2016年   4097篇
  2015年   3567篇
  2014年   4890篇
  2013年   7036篇
  2012年   8860篇
  2011年   9479篇
  2010年   6482篇
  2009年   5398篇
  2008年   8402篇
  2007年   8682篇
  2006年   8327篇
  2005年   7733篇
  2004年   7810篇
  2003年   7477篇
  2002年   7435篇
  2001年   9989篇
  2000年   9782篇
  1999年   7370篇
  1998年   2315篇
  1997年   2108篇
  1996年   2001篇
  1992年   5616篇
  1991年   5823篇
  1990年   5803篇
  1989年   5741篇
  1988年   5345篇
  1987年   4981篇
  1986年   4557篇
  1985年   4826篇
  1984年   3842篇
  1983年   3151篇
  1982年   2173篇
  1981年   1879篇
  1980年   1834篇
  1979年   3464篇
  1978年   2667篇
  1977年   2461篇
  1976年   2409篇
  1975年   2904篇
  1974年   3202篇
  1973年   3154篇
  1972年   2789篇
  1971年   2661篇
  1970年   2251篇
  1969年   2209篇
  1968年   2076篇
  1967年   1832篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Antibodies to calcitonin, parathyroid hormone and cortisol are detected in acute stage of infection-caused bronchial asthma. The appearance of antibodies is paralleled by marked hypercalcaemia. The antibodies may bind excessive hormones in the blood, preventing further hormonal imbalance. Ten-day treatment with glucocorticoids decreased the amount of antibodies possibly due to normalization of hormonal secretion and restoration of their balance. As a result, calcium blood levels returned to normal.  相似文献   
42.
43.
44.
Using homogeneous cytochrome P-450, we have shown that the well-known metyrapone-dithionite reduced cytochrome P-450 complex is specific for the cytochrome P-450b induced by phenobarbital. A linear relationship was observed between the absorbance of metyrapone-reduced cytochrome P-450 complex and the one of CO-reduced cytochrome P-450 complex, the usual method for the determination of cytochrome P-450. A method has been proposed for the specific determination of the cytochrome P-450b.  相似文献   
45.
The time and dose dependence of the relationship between uptake of labelled precursors into protein and RNA and production of testosterone by rabbit follicles was examined. Although testosterone production was stimulated by luteinizing hormone at concentrations between 0.1 and 10 microgram/ml, the uptake of [3H]leucine into protein was significant only when the concentration of luteinizing hormone was greater than 2.5 microgram/ml. Increased production of testosterone was observed within 15 min of stimulation with luteinizing hormone whereas uptake of [3H]leucine was only significant at 90 min. Puromycin (40 microgram/ml) and cycloheximide (10 microgram/ml) in the presence of luteinizing hormone inhibited the synthesis of both testosterone and protein. However, lower concentrations of puromycin (0.1, 1 and 10 microgram/ml) and cycloheximide (1 microgram/ml) had no effect on luteinizing hormone-induced testosterone production but significantly inhibited protein synthesis by 58, 37, 31 and 71%, respectively. Actinomycin D (20, 80 and 160 microgram/ml) alone and in combination with 5 microgram luteinizing hormone/ml severely inhibited uptake of [3H]uridine into RNA without affecting testosterone production. However, with 1 microgram actinomycin/ml, testosterone production was significantly (P less than 0.01) greater than in the presence of luteinizing hormone alone. These results cast doubt on the obligatory role of RNA and protein synthesis in rabbit ovarian follicular steroidogenesis.  相似文献   
46.
47.
48.
49.
An easy, reproducible and fast procedure to isolate DNA from cotton leaves is described. The addition of 0.5 M glucose in the extraction buffer avoids browning by polyphenolic compounds and improves the quality of DNA for molecular analysis. The DNA yield ranged between 150–400 mg per gram of fresh tissue. The DNA was suitable for digestion by restriction enzymes and amplificatiion by Taq DNA polymerase.  相似文献   
50.
Intrastriatal corticotrophin-releasing hormone (CRH) was shown to induce a decrease in the plasma tectosterone concentration. Besides, the 6-OHDA pre-treatment completely prevented the suppression of plasma testosterone in response to intrastriatal CRH administration. The findings suggest that the striatum is involved in the extrahypothalamic regulation of the gonadal endocrine function.  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