全文获取类型
收费全文 | 38206篇 |
免费 | 66篇 |
国内免费 | 100篇 |
专业分类
系统科学 | 175篇 |
丛书文集 | 757篇 |
教育与普及 | 102篇 |
理论与方法论 | 222篇 |
现状及发展 | 16559篇 |
研究方法 | 1581篇 |
综合类 | 18462篇 |
自然研究 | 514篇 |
出版年
2013年 | 200篇 |
2012年 | 502篇 |
2011年 | 1054篇 |
2010年 | 211篇 |
2008年 | 649篇 |
2007年 | 672篇 |
2006年 | 700篇 |
2005年 | 718篇 |
2004年 | 656篇 |
2003年 | 685篇 |
2002年 | 693篇 |
2001年 | 1195篇 |
2000年 | 1114篇 |
1999年 | 757篇 |
1994年 | 340篇 |
1992年 | 720篇 |
1991年 | 574篇 |
1990年 | 625篇 |
1989年 | 601篇 |
1988年 | 586篇 |
1987年 | 622篇 |
1986年 | 631篇 |
1985年 | 777篇 |
1984年 | 621篇 |
1983年 | 512篇 |
1982年 | 445篇 |
1981年 | 451篇 |
1980年 | 555篇 |
1979年 | 1226篇 |
1978年 | 1044篇 |
1977年 | 993篇 |
1976年 | 721篇 |
1975年 | 773篇 |
1974年 | 1072篇 |
1973年 | 916篇 |
1972年 | 969篇 |
1971年 | 1196篇 |
1970年 | 1542篇 |
1969年 | 1171篇 |
1968年 | 1116篇 |
1967年 | 1141篇 |
1966年 | 986篇 |
1965年 | 724篇 |
1959年 | 417篇 |
1958年 | 621篇 |
1957年 | 500篇 |
1956年 | 412篇 |
1955年 | 355篇 |
1954年 | 403篇 |
1948年 | 236篇 |
排序方式: 共有10000条查询结果,搜索用时 820 毫秒
321.
Summary Microelectrophoretic administration of D--aminoadipate reversibly reduced excitatory responses of cat dorsal horn neurones evoked by iontophoretic glutamate and non-noxious peripheral stimuli but did not influence similar responses evoked by noxious peripheral stimuli or iontophoretic substance P. 相似文献
322.
Summary The active calcium transport along the small intestine of adult rat was shown to exhibit daily rhythmic variations of considerable amplitude. Both the light-dark cycle and the time of food presentation acted as synchronizers of the rhythm observed.This work has been supported by Polish Academy of Sciences within the project MR II.1.1.6. 相似文献
323.
Streptozotocin diabetic rats were infertile as a result of decreased Leydig cell function of the testes. The major changes found were: decreased number of Leydig cells and their spontaneous secretion of testosterone. No change in the receptors to LH on the Leydig cells was observed. LH was found to be obligatory for the regulation of Leydig cell function and fertility. 相似文献
324.
The levels of membrane alkaline phosphatase have been measured on different lymphocyte fractions from human peripheral blood separated on bovine serum albumin discontinuous gradients. The peak in enzyme activity was observed in a non-T-, non-B-cell fraction, rich in "null" lymphocytes; the lowest values were found in the fraction with the highest proportion of T-cells. 相似文献
325.
Using an automated system for the analysis of amylase, the release of this enzyme was compared in superfused parotid gland segments from control and reserpine treated rats. Stimulant-evoked amylase release was delayed and of smaller magnitude in the glands of the treated animals and a reduction of the transmembrane K+ gradient caused a smaller and short lasting reduction in Ach-evoked release of amylase in the glands from these animals. 相似文献
326.
A. Borowska S. Sierakowski J. Maćkowiak K. Wiśniewski 《Cellular and molecular life sciences : CMLS》1979,35(10):1368-1370
Summary A correlation between the postirradiation increase of the small intestine motility and the prostaglandin-like activity in this organ during gastrointestinal syndrome was observed. Indomethacin decreased the elevated motility of intestine and reduced the prostaglandin-like activity in this syndrome.Acknowledgments. The work was supported by the Polish Academy of Sciences. 相似文献
327.
Three acidic polysaccharide (AP) fractions and the prostaglandin-like substances (PLS) isolated from P. acnes were investigated regarding their chemotactic activities on polymorphonuclear leukocytes. Both AP's and PLS induced a significant chemotatic response, which suggests their involvement in inflammatory acne vulgaris. 相似文献
328.
It was shown that, in physiological concentrations, insulin enhances, in vitro, the immunological phagocytosis of sensitized sheep erythrocytes by cultured mouse peritoneal macrophages. Insulin seems to stimulate macrophage phagocytosis as a cholinomimetic agonist by increasing the intracellular levels of cyclic GMP. 相似文献
329.
Suppressor cell induction can be demonstrated during antigen specific blastogenesis by using the same methods which have shown induction of suppressor cells by Con A. Since suppressor cells are rapidly generated during antigen specific blastogenesis, they must regulate the final level of blastogenesis induced during the seven day in vitro incubation. 相似文献
330.
During the maturation of red blood cells from rats after stress erythropoiesis, adenyl cyclase activity and beta-adrenoceptor density (pmoles/mg protein) decrease at distinctly different rates suggesting a different turnover of these membrane units. 相似文献