全文获取类型
收费全文 | 364065篇 |
免费 | 4715篇 |
国内免费 | 1062篇 |
专业分类
化学 | 183263篇 |
晶体学 | 5378篇 |
力学 | 16539篇 |
综合类 | 12篇 |
数学 | 45015篇 |
物理学 | 119635篇 |
出版年
2021年 | 3407篇 |
2020年 | 3805篇 |
2019年 | 4110篇 |
2018年 | 5685篇 |
2017年 | 5916篇 |
2016年 | 8370篇 |
2015年 | 4892篇 |
2014年 | 7870篇 |
2013年 | 17813篇 |
2012年 | 13960篇 |
2011年 | 16530篇 |
2010年 | 12174篇 |
2009年 | 11893篇 |
2008年 | 14797篇 |
2007年 | 14678篇 |
2006年 | 13551篇 |
2005年 | 11779篇 |
2004年 | 10924篇 |
2003年 | 9561篇 |
2002年 | 9435篇 |
2001年 | 11039篇 |
2000年 | 8228篇 |
1999年 | 6369篇 |
1998年 | 5335篇 |
1997年 | 5159篇 |
1996年 | 4918篇 |
1995年 | 4270篇 |
1994年 | 4268篇 |
1993年 | 4175篇 |
1992年 | 4599篇 |
1991年 | 4641篇 |
1990年 | 4451篇 |
1989年 | 4328篇 |
1988年 | 4071篇 |
1987年 | 4221篇 |
1986年 | 3965篇 |
1985年 | 5092篇 |
1984年 | 5113篇 |
1983年 | 4249篇 |
1982年 | 4359篇 |
1981年 | 4089篇 |
1980年 | 4036篇 |
1979年 | 4255篇 |
1978年 | 4219篇 |
1977年 | 4238篇 |
1976年 | 4190篇 |
1975年 | 3971篇 |
1974年 | 3906篇 |
1973年 | 3888篇 |
1972年 | 2737篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
951.
Received December 31, 2001 / Published online May 21, 2002 相似文献
952.
953.
Recently, the theory of sortability of partition property has been shown to be an effective tool to prove the existence of an optimal partition with that property. In this paper, we extend the theory to multi-partition where the partition is on t types of components. We apply our results to settle an optimal assignment problem whose proof was incomplete as given in the literature. 相似文献
954.
955.
Effects of various cardioactive agents and a water extract of the pilose antler of Cervus nippon var. mantchuricus on periodic beating of cultured myocardial cell sheets were examined by using an image analyzing system. Norepinephrine increased the beating rate and the beating amplitude, whereas digoxin and forskolin enlarged only the beating amplitude. Verapamil and propranolol decreased both the beating rate and the beating amplitude. The water extract of the pilose antler showed no remarkable effects in a standard medium (2.1 mM Ca2+). However, it significantly increased the beating amplitude when the beating was suppressed by replacement with a low calcium medium (0.5 mM Ca2+). A similar effect was found for 70% ethanol-soluble and -insoluble fractions of the extract. 相似文献
956.
957.
T Yamakawa H Matsukura Y Nomura M Yoshioka M Masaki H Igata S Okabe 《Chemical & pharmaceutical bulletin》1991,39(7):1746-1752
A series of N-substituted 2-[(2-imidazolylsulfinyl)methyl]anilines (3) was synthesized and evaluated for its biological activity against gastric H+/K(+)-ATPase prepared from rabbit stomach and gastric acid secretions in Heidenhain pouch dogs. Monoalkyl substituents on the nitrogen atom of the aniline moiety markedly inhibited the enzyme activity to the same degree as omeprazole, a representative H+/K(+)-ATPase inhibitor. Most of these compounds, administered at 3 mg/kg i.v. inhibited histamine-stimulated gastric acid secretion. The inhibitory activity of these derivatives on the enzymes at pH 6.0 was more potent than that at pH 7.4, and was distinctly correlated to stability in aqueous solution at pH 5.0. 相似文献
958.
959.
960.
An order-level inventory model is developed for deteriorating items with uniform rate of production and stock-dependent demand. Shortages are allowed, and excess demand is backlogged. Results are illustrated with numerical examples.
相似文献