全文获取类型
收费全文 | 181958篇 |
免费 | 19788篇 |
国内免费 | 459篇 |
出版年
2021年 | 1776篇 |
2019年 | 1429篇 |
2018年 | 2157篇 |
2017年 | 2008篇 |
2016年 | 2925篇 |
2015年 | 4114篇 |
2014年 | 4881篇 |
2013年 | 5974篇 |
2012年 | 7272篇 |
2011年 | 7122篇 |
2010年 | 4655篇 |
2009年 | 4331篇 |
2008年 | 5845篇 |
2007年 | 5761篇 |
2006年 | 5339篇 |
2005年 | 4968篇 |
2004年 | 4728篇 |
2003年 | 4505篇 |
2002年 | 4225篇 |
2001年 | 12099篇 |
2000年 | 11882篇 |
1999年 | 9123篇 |
1998年 | 2430篇 |
1997年 | 2538篇 |
1996年 | 2247篇 |
1995年 | 1978篇 |
1994年 | 1896篇 |
1993年 | 1800篇 |
1992年 | 6037篇 |
1991年 | 5766篇 |
1990年 | 5213篇 |
1989年 | 5154篇 |
1988年 | 4671篇 |
1987年 | 4080篇 |
1986年 | 3618篇 |
1985年 | 3480篇 |
1984年 | 2614篇 |
1983年 | 2289篇 |
1982年 | 1640篇 |
1981年 | 1361篇 |
1980年 | 1284篇 |
1979年 | 2368篇 |
1978年 | 1837篇 |
1977年 | 1642篇 |
1976年 | 1396篇 |
1975年 | 1621篇 |
1974年 | 1672篇 |
1973年 | 1595篇 |
1972年 | 1450篇 |
1971年 | 1285篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
131.
Stimulation of leucine uptake by addition of concanavalin A, mediated by increase of intracellular free Ca2+ concentration [( Ca2+]), in lymphocytes (Mitsumoto, Y., Sato, K. and Mohri, T. (1988) Biochim. Biophys. Acta 968, 353-358) was abolished by N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) and chlorpromazine, which inhibited membrane hyperpolarization induced by the mitogen. Quinine (0.5-1 mM) completely inhibited the concanavalin A-induced hyperpolarization and extensively inhibited the induced stimulation of leucine uptake. Based on these results, we suggest that the stimulation of leucine uptake by concanavalin A is largely due to activation of the Ca2+-dependent K+ channel which reinforces negative potential of the plasma membrane and is regulated by calmodulin. 相似文献
132.
133.
134.
135.
O. V. Yagodina E. B. Nikol’skaya I. Y. Shemarova A. E. Khovanskikh 《Journal of Evolutionary Biochemistry and Physiology》2000,36(3):244-248
A comparison has been performed of catalytic properties of unicellular microorganism amine oxidases (AO) from two new enzyme
sources, the bacteriumMethanosarcina barkeri and the infusoriaTetrahymena pyriformis. It was shown that the both studied AO deaminate tyramine, serotonin, and benzylamine, but do not deaminate histamine. The
AO fromMethanosarcina barkeri catalyzes deamination of all three substrates at an identical rate, while the rate of tyramine deamination under effect of
AO fromTetrahymena pyriformis is one order higher than the rate of serotonin deamination, and about two orders higher than the rate of benzylamine deamination.
Based on the data of the substrate-inhibitor analysis, a suggestion was made about the existence of one center for the substrate
binding in the AO of the studied bacterium, while several centers in the AO of the studied infusoria. 相似文献
136.
A rapid, sensitive, assay for enzymes that degrade heparin is described. The procedure is based on the interference of heparin with color development during the interaction of protein with the dye Coomassie brilliant blue. The loss of this property when the glycosaminoglycan is degraded by heparinase can be used to quantify activity of the enzyme in pure form, or in complex biological samples such as tissue homogenates or serum. The assay is also suitable for studying dependence of heparinase activity under conditions such as varying pH and temperature. 相似文献
137.
138.
139.
Spencer G. Lucas Bolat U. Bayshashov Lyubov A. Tyutkova Ayzhan K. Zhamangara Bolat Z. Aubekerov 《Pal?ontologische Zeitschrift》1997,71(3-4):305-314
At Aktau Mountain in the Ili depression of eastern Kazakstan, fossil mammals that encompass the Paleogene-Neogene boundary occur at three stratigraphic levels. The lowest level is in the lower Kyzylbulak Formation and produces Brontotheriidae and the hyracodontidArdynia and is tentatively assigned a late Eocene (Ergilian) age. The lower part of the overlying Aktau Formation produces fossils of the giant rhinocerosParaceratherium and is tentatively assigned a late Oligocene (Tabenbulukian) age. The upper part of the Aktau Formation yields a fossil mammal assemblage that includesGomphotherium,Stephanocemas, Brachypotherium andLagomeryx. It is clearly of Miocene age, probably late early Miocene (late Burdigalian), a correlative of European Reference Level MN 5 and the late Shanwangian of China. The Paleogene-Neogene boundary at Aktau Mountain thus is in the Aktau Formation. 相似文献
140.
The circulatory anatomy of the iliofemoral region was elucidated by doing detailed angiography in 50 cases, and we classified the vessels into 4 types. In most cases, the s.c.i.a. predominated over the s.i.e.a. Therefore, it is probably better to plan free flaps supplied by this artery. This vessel usually arises approximately two or three fingerbreadths inferior to the intersection of the femoral artery and the inguinal ligament, and the skin flap should be designed in the area inferior and parallel to the inguinal ligament. 相似文献