全文获取类型
收费全文 | 98315篇 |
免费 | 4775篇 |
国内免费 | 12794篇 |
专业分类
化学 | 79022篇 |
晶体学 | 1215篇 |
力学 | 2416篇 |
综合类 | 873篇 |
数学 | 12812篇 |
物理学 | 19546篇 |
出版年
2024年 | 124篇 |
2023年 | 783篇 |
2022年 | 2037篇 |
2021年 | 1986篇 |
2020年 | 2474篇 |
2019年 | 2393篇 |
2018年 | 2056篇 |
2017年 | 2961篇 |
2016年 | 3043篇 |
2015年 | 2545篇 |
2014年 | 3681篇 |
2013年 | 7480篇 |
2012年 | 6499篇 |
2011年 | 5323篇 |
2010年 | 4502篇 |
2009年 | 6104篇 |
2008年 | 6352篇 |
2007年 | 6673篇 |
2006年 | 6066篇 |
2005年 | 5196篇 |
2004年 | 4865篇 |
2003年 | 4006篇 |
2002年 | 5113篇 |
2001年 | 3008篇 |
2000年 | 2779篇 |
1999年 | 2613篇 |
1998年 | 2261篇 |
1997年 | 1762篇 |
1996年 | 1491篇 |
1995年 | 1437篇 |
1994年 | 1306篇 |
1993年 | 1079篇 |
1992年 | 1003篇 |
1991年 | 687篇 |
1990年 | 564篇 |
1989年 | 547篇 |
1988年 | 403篇 |
1987年 | 321篇 |
1986年 | 291篇 |
1985年 | 238篇 |
1984年 | 253篇 |
1983年 | 142篇 |
1982年 | 225篇 |
1981年 | 183篇 |
1980年 | 199篇 |
1979年 | 189篇 |
1978年 | 170篇 |
1977年 | 123篇 |
1976年 | 109篇 |
1973年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Yang Woo Shin 《Operations Research Letters》2004,32(4):364-373
We consider a single server queue with disasters where the arrivals of customers and disasters are correlated. When a disaster occurs, it removes all the customers in the system and there requires repair time for the system to be operated normally. The stationary queue length distribution at the embedded points and at an arbitrary time are presented. 相似文献
102.
We will prove a result concerning the inclusion of non-trivial invariant ideals inside non-trivial ideals of a twisted crossed
product. We will also give results concerning the primeness and simplicity of crossed products of twisted actions of locally
compact groups on -algebras.
Received: 25 January 2002; in final form: 22 May 2002/Published online: 2 December 2002
This work is partially supported by Hong Kong RGC Direct Grant. 相似文献
103.
Zhu Yongliang; Pagilla Prabhakar R. 《IMA Journal of Mathematical Control and Information》2005,22(2):181-186
We derive some useful and easily computable necessary conditionsfor the existence of a positive semi-definite solution to thealgebraic Ricatti equation (ARE). A motivating example is givento highlight the usefulness of the conditions for controllerand observer designs for nonlinear systems. Further, an upperbound on the trace of the solution to the ARE is also derived. 相似文献
104.
I. Peshko G. Galich M. Lopiychuk A. Khizhnyak V. Nakvasuk 《Optics & Laser Technology》1997,29(4):211-215
A laser system containing four CW Nd:YAG double-rod lasers, transforming optics and a fibre with input-output optics has been designed and investigated. It is shown that reduction of the beam parameter product of the non-Gaussian beams in the image space of the lens has made it possible to collect the emission of four lasers to the same fibre. Independent laser operation has provided the output power control in the range of 10–900 W with a stable light spot size on the input end of the fibre. 相似文献
105.
报道了KDP晶体中的三倍频产生的实验研究,计算了比较了直接三倍频过程和级联过程对KDP晶体三阶有效非线性系数的贡献,并探讨了KDP作为非线性晶体材料三阶非线性系数测量基准的可行性。 相似文献
106.
107.
Mass distributions of fragments in the low-energy fission of nuclei from 187Ir to 213At have been analysed. This analysis has shown that shell effects in symmetric-mode fragment mass yields from the fission of pre-actinide nuclei could be described if one assumes the existence of two strongly deformed neutron shells in the arising fragments with neutron numbers N1 ≈ 52 and N2 ≈ 68. A new method has been proposed for quantitatively describing the mass distributions of the symmetric fission mode for pre-actinides with A ≈ 180–220. 相似文献
108.
We investigate several versions of a cardinal characteristic defined by Frankiewicz. Vojtáš showed , and Blass showed . We show that all the versions coincide and that is greater than or equal to the splitting number. We prove the consistency of and of .
Received: 2 October 1996 / Revised version: 22 May 1997 相似文献
109.
本文首先提出逆(反)对策这一新问题,给出了数学模型;探讨了“奇门遁甲”预测理论(术)中的数学问题;通过系统分析“专门遁甲”预测过程,可知它的预测过程隐含着一个特殊的逆(反)对策问题;最后指出逆(反)对策问题的广泛存在并给出案例分析. 相似文献
110.
Summary. We study a diffusion model of an interacting particles system with general drift and diffusion coefficients, and electrostatic
inter-particles repulsion. More precisely, the finite particle system is shown to be well defined thanks to recent results
on multivalued stochastic differential equations (see [2]), and then we consider the behaviour of this system when the number
of particles goes to infinity (through the empirical measure process). In the particular case of affine drift and constant diffusion coefficient,
we prove that a limiting measure-valued process exists and is the unique solution of a deterministic PDE. Our treatment of
the convergence problem (as ) is partly similar to that of T. Chan [3] and L.C.G. Rogers - Z. Shi [5], except we consider here a more general case allowing
collisions between particles, which leads to a second-order limiting PDE.
Received: 5 August 1996 / In revised form: 17 October 1996 相似文献