全文获取类型
收费全文 | 487785篇 |
免费 | 47454篇 |
国内免费 | 196篇 |
专业分类
535435篇 |
出版年
2018年 | 5060篇 |
2017年 | 4782篇 |
2016年 | 6225篇 |
2015年 | 6906篇 |
2014年 | 8760篇 |
2013年 | 12340篇 |
2012年 | 14313篇 |
2011年 | 14919篇 |
2010年 | 10144篇 |
2009年 | 9307篇 |
2008年 | 13361篇 |
2007年 | 13854篇 |
2006年 | 13362篇 |
2005年 | 12665篇 |
2004年 | 12635篇 |
2003年 | 12257篇 |
2002年 | 12156篇 |
2001年 | 24771篇 |
2000年 | 24823篇 |
1999年 | 19094篇 |
1998年 | 5682篇 |
1997年 | 5856篇 |
1996年 | 5414篇 |
1995年 | 4931篇 |
1994年 | 4870篇 |
1993年 | 4884篇 |
1992年 | 15032篇 |
1991年 | 15107篇 |
1990年 | 14633篇 |
1989年 | 14423篇 |
1988年 | 13429篇 |
1987年 | 12559篇 |
1986年 | 11414篇 |
1985年 | 11453篇 |
1984年 | 9061篇 |
1983年 | 7731篇 |
1982年 | 5384篇 |
1981年 | 4714篇 |
1980年 | 4564篇 |
1979年 | 8300篇 |
1978年 | 6409篇 |
1977年 | 5838篇 |
1976年 | 5410篇 |
1975年 | 6311篇 |
1974年 | 6767篇 |
1973年 | 6636篇 |
1972年 | 5928篇 |
1971年 | 5540篇 |
1970年 | 4830篇 |
1969年 | 4687篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
L I Kulikova G A Iatskiavichiute V S Tsvetkov Iu E Ershikova S P Gordienko 《Biulleten' eksperimental'no? biologii i meditsiny》1987,104(8):224-226
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
92.
93.
94.
95.
96.
97.
V. Luu-The J. Cumps P. Dumont 《Biochemical and biophysical research communications》1980,93(3):776-781
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
98.
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
99.
The ability of human uterine endometrium to aromatize androstenedione to estrogens was investigated using 10 normal and neoplastic tissues. Normal and neoplastic endometrial homogenates were incubated with [6,7-3H]androstenedione (A) and NADPH. Estrone (E1) and estradiol (E2) were subsequently isolated in amounts ranging from 0-17600 fmol/h/g and 0-377 fmol/h/g, respectively, from the incubates after purifications by using Bio-Rad AG1-X2 column, thin layer chromatographies and co-crystallization. The conversion of A to E1 and E2 was significantly higher in neoplastic tissues. 相似文献
100.
Properties of purified colchicine-binding protein from a cultured carrot cell extract 总被引:1,自引:0,他引:1
Colchicine-binding protein (CBP) was purified from a cultured carrot cell extract by DEAE-Sephacel, phosphocellulose and Sephadex G200 column chromatographies. The purified CBP separated into three bands on SDS-polyacrylamide gel electrophoresis. One of them reacted with a monoclonal antibody against chick brain alpha-tubulin and the other two with that against beta-tubulin. Colchicine-binding activity of the purified protein was enhanced by tartrate and inhibited little by an excess of podophyllotoxin. It decayed following first order kinetics, but was more stable than the CBP in the crude extract. The binding constant of the purified CBP for colchicine was 0.57 microM-1 and the number of binding sites of colchicine per mg protein was about 2 nmol. This binding constant is about ten times lower than that of porcine brain tubulin under identical conditions. 相似文献