全文获取类型
收费全文 | 140871篇 |
免费 | 11548篇 |
国内免费 | 7788篇 |
专业分类
化学 | 69516篇 |
晶体学 | 1539篇 |
力学 | 10357篇 |
综合类 | 427篇 |
数学 | 38938篇 |
物理学 | 39430篇 |
出版年
2024年 | 63篇 |
2023年 | 1384篇 |
2022年 | 1592篇 |
2021年 | 2407篇 |
2020年 | 2821篇 |
2019年 | 2701篇 |
2018年 | 12169篇 |
2017年 | 11904篇 |
2016年 | 8991篇 |
2015年 | 3994篇 |
2014年 | 4117篇 |
2013年 | 5200篇 |
2012年 | 9699篇 |
2011年 | 16198篇 |
2010年 | 9645篇 |
2009年 | 9757篇 |
2008年 | 10645篇 |
2007年 | 12358篇 |
2006年 | 3703篇 |
2005年 | 4300篇 |
2004年 | 3758篇 |
2003年 | 3771篇 |
2002年 | 2733篇 |
2001年 | 1609篇 |
2000年 | 1509篇 |
1999年 | 1582篇 |
1998年 | 1366篇 |
1997年 | 1254篇 |
1996年 | 1225篇 |
1995年 | 1082篇 |
1994年 | 886篇 |
1993年 | 788篇 |
1992年 | 615篇 |
1991年 | 577篇 |
1990年 | 515篇 |
1989年 | 398篇 |
1988年 | 307篇 |
1987年 | 269篇 |
1986年 | 269篇 |
1985年 | 242篇 |
1984年 | 157篇 |
1983年 | 158篇 |
1982年 | 124篇 |
1981年 | 96篇 |
1980年 | 85篇 |
1979年 | 64篇 |
1978年 | 42篇 |
1973年 | 42篇 |
1914年 | 45篇 |
1909年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
研究了非相干辐照对LiNbO3:Fe晶体中从自散焦到自聚焦的动态转换过程的影响和控制作用.无论是从前向还是从背向加入非相干辐照,都能加快自散焦、自聚焦过程以及从自散焦到自聚焦的转换过程,增大折射率的变化值.当非相干辐照以一定的时间间隔重复辐照在晶体上时,透射功率能迅速地上升和下降,具有明显的开关效应.这种在非相干辐照控制下折射率的迅速改变有望应用于全光学开关器件.
关键词:
非相干辐照
光伏效应
自散焦
自聚焦 相似文献
992.
993.
The classes ofL
1-matrices,L
2-matrices,L
3-matrices andW-matrices are introduced to study solvability of a linear complementarity problem via solving a linear program. Three sufficient
conditions are presented to guarantee that a linear complementarity problem is solvable via a linear program. The new sufficient
conditions are weaker than the ones introduced by Mangasarian. This fact is also illustrated by an example.
Partially supported by NSFC.
This author is also with College of Business Administration of Human University as a Lotus chair professor. 相似文献
994.
Gergely Harcos 《Mathematische Annalen》2003,326(2):347-365
We establish an estimate on sums of shifted products of Fourier coefficients coming from holomorphic or Maass cusp forms
of arbitrary level and nebentypus. These sums are analogous to the binary additive divisor sum which has been studied extensively.
As an application we derive, extending work of Duke, Friedlander and Iwaniec, a subconvex estimate on the critical line for
L-functions associated to character twists of these cusp forms.
Received: 2 October 2001 / Revised version: 9 September 2002 /
Published online: 28 March 2003
Mathematics Subject Classification (2000): Primary 11F30, 11F37; Secondary 11M41. 相似文献
995.
We report on Raman scattering of VO2 films prepared by radio frequency magnetron sputtering under different conditions. Our investigations revealed that the dominated Raman peaks shift towards high frequency for both V-rich and O-rich VO2 films, compared with the stoichiometry VO2 films. The experimental evidence is presented and the cause for nonstoichiometry dependence of Raman spectra of VO2 films is discussed. 相似文献
996.
The existing model for multivariate skew normal data does not cohere with the joint distribution of a random sample from a
univariate skew normal distribution. This incoherence causes awkward interpretation for data analysis in practice, especially
in the development of the sampling distribution theory. In this paper, we propose a refined model that is coherent with the
joint distribution of the univariate skew normal random sample, for multivariate skew normal data. The proposed model extends
and strengthens the multivariate skew model described in Azzalini (1985,Scandinavian Journal of Statistics,12, 171–178). We present a stochastic representation for the newly proposed model, and discuss a bivariate setting, which confirms
that the newly proposed model is more plausible than the one given by Azzalini and Dalla Valle (1996,Biometrika,83, 715–726). 相似文献
997.
BinayakS.Choudhury 《分析论及其应用》2003,19(2):99-107
In the present paper we introduce a random iteration scheme for three random operators defined on a closed and convex subset of a uniformly convex Banach space and prove its convergence to a common fixed point of three random operators. The result is also an extersion of a known theorem in the corresponding non-random case. 相似文献
998.
M Khouja 《The Journal of the Operational Research Society》2003,54(9):984-994
Supply chain management literature calls for coordination between the different members of the chain. Materials should be moved from one supplier to the next according to a just-in-time schedule. In this paper, we show that for many supply chain configurations, complete synchronization will result in some members of the chain being ‘losers’ in terms of cost. We develop an algorithm for optimal synchronization of supply chains and provide some guidelines for incentive alignment along the supply chain. In developing the model, we use the economic delivery and scheduling problem model and analyze supply chains dealing with single and multiple components. For single-component supply chains, we derive a closed-form expression for the optimal synchronized cycle time. For multi-component supply chains, we develop an algorithm for finding the optimal synchronized cycle time. We test the performance of the algorithm and show that it provides optimal solutions for a wide range of problems. We illustrate the models with numerical examples. 相似文献
999.
This paper firstly examines the value of optical bypass scheme in packet ring networks. An Integer Linear Program (ILP) formulation is presented and analytical results under different traffic patterns are given. 相似文献
1000.
We prove that, under the assumption of the Generalized Riemann Hypothesis, the exponent of the ideal class group of a CM-field
goes to infinity with its absolute discriminant. This gives a positive answer to a question raised by Louboutin and Okazaki
[4].
Received September 10, 2001; in revised form April 5, 2002 相似文献