全文获取类型
收费全文 | 173495篇 |
免费 | 16920篇 |
国内免费 | 12090篇 |
专业分类
化学 | 92941篇 |
晶体学 | 1849篇 |
力学 | 11915篇 |
综合类 | 666篇 |
数学 | 43442篇 |
物理学 | 51692篇 |
出版年
2024年 | 239篇 |
2023年 | 1998篇 |
2022年 | 2490篇 |
2021年 | 3443篇 |
2020年 | 4110篇 |
2019年 | 3872篇 |
2018年 | 13087篇 |
2017年 | 12640篇 |
2016年 | 10389篇 |
2015年 | 5452篇 |
2014年 | 6062篇 |
2013年 | 7823篇 |
2012年 | 12656篇 |
2011年 | 19325篇 |
2010年 | 11920篇 |
2009年 | 11961篇 |
2008年 | 12900篇 |
2007年 | 14254篇 |
2006年 | 5771篇 |
2005年 | 5885篇 |
2004年 | 5093篇 |
2003年 | 4817篇 |
2002年 | 3622篇 |
2001年 | 2455篇 |
2000年 | 2227篇 |
1999年 | 2200篇 |
1998年 | 1922篇 |
1997年 | 1700篇 |
1996年 | 1745篇 |
1995年 | 1479篇 |
1994年 | 1313篇 |
1993年 | 1094篇 |
1992年 | 953篇 |
1991年 | 838篇 |
1990年 | 700篇 |
1989年 | 560篇 |
1988年 | 434篇 |
1987年 | 395篇 |
1986年 | 391篇 |
1985年 | 307篇 |
1984年 | 229篇 |
1983年 | 188篇 |
1982年 | 166篇 |
1981年 | 116篇 |
1980年 | 105篇 |
1979年 | 68篇 |
1978年 | 56篇 |
1973年 | 42篇 |
1914年 | 45篇 |
1909年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
931.
We prove some extension theorems for analytic objects, in particular sections of a coherent sheaf, defined in semi q-coronae of a complex space. Semi q-coronae are domains whose boundary is the union of a Levi flat part, a q-pseudoconvex part and a q-pseudoconcave part. Such results are obtained mainly using cohomological techniques. 相似文献
932.
Optimal explicit Runge–Kutta methods consider more stages in order to include a particular spectrum in their stability domain
and thus reduce time-step restrictions. This idea, so far used mostly for real-line spectra, is generalized to more general
spectra in the form of a thin region. In thin regions the eigenvalues may extend away from the real axis into the imaginary
plane. We give a direct characterization of optimal stability polynomials containing a maximal thin region and calculate these
polynomials for various cases. Semi-discretizations of hyperbolic–parabolic equations are a relevant application which exhibit
a thin region spectrum. As a model, linear, scalar advection–diffusion is investigated. The second-order-stabilized explicit
Runge–Kutta methods derived from the stability polynomials are applied to advection–diffusion and compressible, viscous fluid
dynamics in numerical experiments. Due to the stabilization the time step can be controlled solely from the hyperbolic CFL
condition even in the presence of viscous fluxes. 相似文献
933.
934.
Ding-kang WANG~ Yan ZHANG Key Laboratory of Mathematics Mechanization Academy of Mathematics Systems Science Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2007,50(10):1441-1450
We present an algorithm to decompose a polynomial system into a finite set of normal ascending sets such that the set of the zeros of the polynomial system is the union of the sets of the regular zeros of the normal ascending sets.If the polynomial system is zero dimensional,the set of the zeros of the polynomials is the union of the sets of the zeros of the normal ascending sets. 相似文献
935.
We obtain asymptotic lower bounds for the spectral function of the Laplacian and for the remainder in local Weyl’s law on
manifolds. In the negatively curved case, thermodynamic formalism is applied to improve the estimates. Key ingredients of
the proof include the wave equation parametrix, a pretrace formula and the Dirichlet box principle. Our results develop and
extend the unpublished thesis of A. Karnaukh [Ka].
The first author was supported by NSERC, FQRNT, Alfred P. Sloan Foundation Fellowship and Dawson Fellowship. The second author
was supported by NSERC and FQRNT.
Received: April 2006 Revision: October 2006 Accepted: October 2006 相似文献
936.
Victor V. Dodonov Margarita A. Man’ko Vladimir I. Man’ko Apostol Vourdas 《Journal of Russian Laser Research》2007,28(5):404-428
A brief review of the history of ten workshops/conferences on “Squeezed States and Uncertainty Relations” and main achievements
in the related fields of quantum physics for the period from 1991 to 2007 are presented. 相似文献
937.
938.
939.
A group of machines for processing a set of jobs in a manufacturing system is often located in a serial line. An efficient strategy for locating these machines such that the total travel distance or the cost of transporting the jobs is minimized is desired. In this research, the assumption of a linear line with equally spaced machine location is relaxed. This research addressed problems of locating unique machines. It is found that the machine distances possess unique properties in this type of a problem. Utilizing these properties, heuristic strategies are proposed to obtain efficient solution where optimal methods are expected to be computationally prohibitive. A lower bound for the optimum solution is also proposed. Results are encouraging. 相似文献
940.
Martin I. Karakhanyan 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2007,42(3):146-150
The paper proves some general facts on commutators that refer to Fuglede-Putnam classical theorem in the spectral theory of not necessarily selfadjoint operators. 相似文献