全文获取类型
收费全文 | 603902篇 |
免费 | 5656篇 |
国内免费 | 1688篇 |
专业分类
化学 | 293955篇 |
晶体学 | 9282篇 |
力学 | 29569篇 |
综合类 | 9篇 |
数学 | 87116篇 |
物理学 | 191315篇 |
出版年
2021年 | 4542篇 |
2020年 | 5063篇 |
2019年 | 5641篇 |
2018年 | 13397篇 |
2017年 | 13907篇 |
2016年 | 13916篇 |
2015年 | 7482篇 |
2014年 | 10816篇 |
2013年 | 25748篇 |
2012年 | 22625篇 |
2011年 | 31879篇 |
2010年 | 21917篇 |
2009年 | 21624篇 |
2008年 | 28357篇 |
2007年 | 30437篇 |
2006年 | 19587篇 |
2005年 | 21898篇 |
2004年 | 18260篇 |
2003年 | 16509篇 |
2002年 | 14990篇 |
2001年 | 16030篇 |
2000年 | 12421篇 |
1999年 | 9560篇 |
1998年 | 7994篇 |
1997年 | 7675篇 |
1996年 | 7554篇 |
1995年 | 6617篇 |
1994年 | 6561篇 |
1993年 | 6486篇 |
1992年 | 6976篇 |
1991年 | 7198篇 |
1990年 | 6895篇 |
1989年 | 6684篇 |
1988年 | 6525篇 |
1987年 | 6508篇 |
1986年 | 6118篇 |
1985年 | 8042篇 |
1984年 | 8283篇 |
1983年 | 6744篇 |
1982年 | 7002篇 |
1981年 | 6700篇 |
1980年 | 6485篇 |
1979年 | 6860篇 |
1978年 | 6916篇 |
1977年 | 6808篇 |
1976年 | 6935篇 |
1975年 | 6415篇 |
1974年 | 6399篇 |
1973年 | 6533篇 |
1972年 | 4574篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
Necessary conditions for the Gâteaux differentiability of the distance function to a set are considered. A series of characterizing results is obtained. 相似文献
93.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
94.
E. P. Gordov 《Russian Physics Journal》1981,24(11):1039-1041
An evolution operatior is described, which acts on the operators of a problem to take it into the solutions of the corresponding problem of semiclassical electrodynamics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 66–69, November, 1981. 相似文献
95.
Dominant nonlinear electric dipole polarizations at the interaction of fundamental and second harmonic waves in centrosymmetric media without and with memory are treated in this paper. The process of forming a permanent spatially periodic quadratic susceptibility grating in the medium with memory is described from the phenomenological point of view.Dedicated to the Czechoslovak Student Movement '89. 相似文献
96.
97.
The variational problem of contact equilibrium of a punch and an elastic body is considered. An equivalent formulation of the problem is given in variational inequality form. Existence and uniqueness of the solution is investigated in a particular case. A penalty method is proposed for approximate solution of the problem.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 56, pp. 97–103, 1985. 相似文献
98.
D. A. Tikhomirov O. S. Slyadevskaya A. V. Eremeev 《Chemistry of Heterocyclic Compounds》1991,27(9):966-969
A convenient method of synthesis of 2-(methoxycarbonylmethylene)-substituted imidazolidines and imidazolidinium bromides, and also of bicyclic diazo compounds has been developed starting from methyl bromopropiolate and ethylenediamine and its derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1205–1208, September, 1991. 相似文献
99.
100.
A firm's logistics cost, including shipping and inventory-carrying, is a substantial percentage of its sales. Nevertheless, typical inventory-control methods ignore or insufficiently represent the shipping cost. This paper describes a recursive algorithm that determines the reorder cycle-time that minimizes total logistics cost. It allows for a realistic accounting of shipping cost, which is modelled here as a function of shipping distance and weight. The algorithm uses a relaxation procedure to identify a suitable initial approximation to the optimal order cycle-time and then, through a series of recursive steps, moves to the optimal result. We demonstrate the algorithm with a single item, with a group of items that share a common order cycle, and with multi-items when item demands are random variables. Experience with this algorithm indicates that it converges to the optimal result in a very few steps. 相似文献