全文获取类型
收费全文 | 61318篇 |
免费 | 2231篇 |
国内免费 | 410篇 |
专业分类
化学 | 42396篇 |
晶体学 | 530篇 |
力学 | 1600篇 |
综合类 | 2篇 |
数学 | 8273篇 |
物理学 | 11158篇 |
出版年
2023年 | 296篇 |
2022年 | 711篇 |
2021年 | 908篇 |
2020年 | 1027篇 |
2019年 | 1032篇 |
2018年 | 740篇 |
2017年 | 700篇 |
2016年 | 1656篇 |
2015年 | 1443篇 |
2014年 | 1783篇 |
2013年 | 3173篇 |
2012年 | 4091篇 |
2011年 | 4543篇 |
2010年 | 2600篇 |
2009年 | 2307篇 |
2008年 | 3971篇 |
2007年 | 3704篇 |
2006年 | 3615篇 |
2005年 | 3373篇 |
2004年 | 2925篇 |
2003年 | 2341篇 |
2002年 | 2282篇 |
2001年 | 1154篇 |
2000年 | 1039篇 |
1999年 | 742篇 |
1998年 | 645篇 |
1997年 | 701篇 |
1996年 | 779篇 |
1995年 | 568篇 |
1994年 | 640篇 |
1993年 | 605篇 |
1992年 | 565篇 |
1991年 | 480篇 |
1990年 | 396篇 |
1989年 | 345篇 |
1988年 | 350篇 |
1987年 | 338篇 |
1986年 | 272篇 |
1985年 | 537篇 |
1984年 | 441篇 |
1983年 | 376篇 |
1982年 | 461篇 |
1981年 | 364篇 |
1980年 | 367篇 |
1979年 | 300篇 |
1978年 | 307篇 |
1977年 | 299篇 |
1976年 | 298篇 |
1975年 | 286篇 |
1974年 | 238篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
We shall answer several questions concerning additive or multiplicative commutators in a division ring which are algebraic of bounded degree over its center. 相似文献
102.
103.
The control of piecewise-deterministic processes is studied where only local boundedness of the data is assumed. Moreover the discount rate may be zero. The value function is shown to be solution to the Bellman equation in a weak sense; however the solution concept is strong enough to generate optimal policies. Continuity and compactness conditions are given for the existence of nonrelaxed optimal feedback controls. 相似文献
104.
Hayoung Lee 《Mathematical Methods in the Applied Sciences》2004,27(3):249-287
The motion of a collisionless plasma is modelled by the Vlasov–Maxwell system. In this paper, solutions of the relativistic Vlasov–Maxwell system are considered in two space dimensions. The speed of light, c, appears as a parameter in the system. With representations of the electric and magnetic fields, conditions are established under which solutions of the relativistic Vlasov–Maxwell system converge pointwise to solutions of the non‐relativistic Vlasov–Poisson system as c tends to infinity, at the asymptotic rate of 1/c. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
105.
The reaction of Me2CuLi with sterically congested α,β-unsaturated esters in the presence of TMSCl in CH2Cl2 proceeded very smoothly to produce the conjugate addition products in high yields. 相似文献
106.
107.
Several models have been developed in order to categorize the numerous expressions that people use in order to describe their emotional experiences. The focus of the present study is on one of these theoretical classifications proposed by Pekrun (1992) specifically concerning emotions which are directly related to learning and achievement in mathematics. In his model, emotions are classified according to their valence (positive vs. negative) and their level of activation. In testing the assumptions of this model, we investigated students' enjoyment, anxiety, anger and boredom experienced before, during, and after the completion of a math test. Correspondence analyses which were used to generate a graphical illustration of structural interrelationships between these emotions provide empirical support for the theoretical classification. 相似文献
108.
109.
110.