全文获取类型
收费全文 | 1963篇 |
免费 | 11篇 |
国内免费 | 33篇 |
专业分类
系统科学 | 46篇 |
丛书文集 | 14篇 |
教育与普及 | 4篇 |
理论与方法论 | 45篇 |
现状及发展 | 860篇 |
研究方法 | 177篇 |
综合类 | 815篇 |
自然研究 | 46篇 |
出版年
2019年 | 13篇 |
2018年 | 19篇 |
2017年 | 20篇 |
2016年 | 21篇 |
2015年 | 17篇 |
2014年 | 17篇 |
2013年 | 42篇 |
2012年 | 70篇 |
2011年 | 93篇 |
2010年 | 25篇 |
2009年 | 11篇 |
2008年 | 50篇 |
2007年 | 50篇 |
2006年 | 71篇 |
2005年 | 55篇 |
2004年 | 59篇 |
2003年 | 91篇 |
2002年 | 126篇 |
2001年 | 144篇 |
2000年 | 95篇 |
1999年 | 66篇 |
1997年 | 11篇 |
1992年 | 25篇 |
1990年 | 18篇 |
1989年 | 15篇 |
1988年 | 20篇 |
1987年 | 24篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 24篇 |
1979年 | 38篇 |
1978年 | 35篇 |
1977年 | 34篇 |
1976年 | 30篇 |
1975年 | 39篇 |
1974年 | 29篇 |
1973年 | 30篇 |
1972年 | 43篇 |
1971年 | 43篇 |
1970年 | 31篇 |
1969年 | 32篇 |
1968年 | 25篇 |
1967年 | 29篇 |
1966年 | 33篇 |
1965年 | 21篇 |
1958年 | 9篇 |
排序方式: 共有2007条查询结果,搜索用时 105 毫秒
211.
P Lemay N Pluquet de Temmerman A Tavitian J Bernard 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,284(24):2573-2575
A DNA complementary to the viral genome of C-type particles produced by a Mouse myeloma derived cell line (MF2 cell line) was synthesized. This cDNA was used as a probe to study the viral genome expression among the total RNA and the poly (A)-rich RNA extracted from the MF2 and Balb/c embryonic cells. As evidenced by molecular hybridization experiments, the presence of at least one endogenous Balb/c virus in the MF2 virus stocks is suggested. In the productive cells, the viral RNA sequences are expressed in the poly (A)-rich RNA fraction. 相似文献
212.
A highly significant enhancement of the hydrosmotic actions both of vasopressin and of exogenous cAMP was seen in the presence of quercetin. The hypothesis is advanced that quercetin affects the intracellular coupling between Ca++ in cAMP. 相似文献
213.
G. de Saint Blanquat P. Fritsch R. Derache 《Cellular and molecular life sciences : CMLS》1975,31(12):1432-1434
Summary Pylorus ligature hides the inhibitory effects of endogenous cholecystokinine-pancreozyme (CCK-PZ) on gastric mucosal secretion and irrigation, whereas the juice collected through transduodenal pyloric fistula makes this phenomenon obvious. It appears that the pyloric fistula encourages inhibition of gastrinic secretion, so that the CCK-PZ can achieve its effects. 相似文献
214.
Beta 2-microglobulin from serum associates with MHC class I antigens on the surface of cultured cells 总被引:3,自引:0,他引:3
Beta 2-microglobulin (beta 2-m) is a highly conserved polypeptide (12,000 molecular weight; 12K) noncovalently associated with the heavy chain (45-48K) of the major histocompatibility complex (MHC) class I antigens. Its synthesis is required for expression of the HLA-A/B and H-2K/D heavy chains at the cell surface; beta 2-m is also associated with the human cell-surface antigens T6 and M241 isolated from thymocytes. However, on the T leukaemic cell line MOLT-4 some of the T6 antigens contain a different 12K subunit, termed beta t (refs 3, 7, 8). Purified human beta 2-m can exchange partially both with human beta 2-m associated with HLA-antigens, and with mouse beta 2-m associated with murine alloantigens. As MOLT-4 cells were grown in the presence of fetal calf serum (FCS) and as serum is known to contain some free beta 2-m, we examined whether beta t was bovine beta 2-m which had replaced endogenous beta 2-m on the surface of the cell. Here we show both that beta 2-m from FCS or human serum (HuS) used in cell culture can exchange with beta 2-m on the cell surface, and that beta t is in fact bovine beta 2-m. 相似文献
215.
216.
J. de Koning A. M. I. Tijssen J. A. M. J. van Dieten T. R. Koiter G. A. Schuiling G. P. van Rees 《Cellular and molecular life sciences : CMLS》1986,42(1):60-62
Summary The patterns of LH secretion during constant stimulation of the pituitary glands of estradiol-treated ovariectomized rats with a maximally stimulating amount of LH-RH in vivo and in vitro correspond with each other qualitatively and quantitatively. In vitro the changes with time of the LH secretion rate are somewhat retarded, especially the occurrence of desensitization. 相似文献
217.
218.
219.
F Ferre M Breuiller D de Pariente L Cedard 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,285(1):73-76
The hydrolysis of cAMP by phosphodiesterase was studied in whole homogenate from human myometrium at the end of the pregnancy before onset of labour. Tissue samples were taken from outer and inner layers of placental and anti-placental sites. Kinetic analysis shows in every case two apparent Km values for low and high cAMP concentrations in the order of 1 x 10(-5) M and 1 x 10(-4) M. On the other hand Vmax values are lower for the enzyme isolated from the placental site than for the one isolated from the anti-placental area. In the 4 zones studied, an appreciable proportion of the low Km enzyme is present. 相似文献
220.