全文获取类型
收费全文 | 4516篇 |
免费 | 181篇 |
国内免费 | 11篇 |
专业分类
化学 | 2921篇 |
晶体学 | 18篇 |
力学 | 153篇 |
数学 | 750篇 |
物理学 | 866篇 |
出版年
2023年 | 37篇 |
2022年 | 76篇 |
2021年 | 128篇 |
2020年 | 117篇 |
2019年 | 82篇 |
2018年 | 83篇 |
2017年 | 67篇 |
2016年 | 202篇 |
2015年 | 164篇 |
2014年 | 146篇 |
2013年 | 282篇 |
2012年 | 300篇 |
2011年 | 328篇 |
2010年 | 215篇 |
2009年 | 149篇 |
2008年 | 261篇 |
2007年 | 279篇 |
2006年 | 256篇 |
2005年 | 210篇 |
2004年 | 211篇 |
2003年 | 161篇 |
2002年 | 141篇 |
2001年 | 73篇 |
2000年 | 46篇 |
1999年 | 28篇 |
1998年 | 32篇 |
1997年 | 43篇 |
1996年 | 41篇 |
1995年 | 34篇 |
1994年 | 30篇 |
1993年 | 24篇 |
1992年 | 35篇 |
1991年 | 19篇 |
1990年 | 29篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 25篇 |
1982年 | 25篇 |
1981年 | 23篇 |
1980年 | 25篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1974年 | 12篇 |
1934年 | 11篇 |
排序方式: 共有4708条查询结果,搜索用时 15 毫秒
1.
Bonelli Giulio Grassi Alba Tanzini Alessandro 《Letters in Mathematical Physics》2019,109(9):1961-2001
Letters in Mathematical Physics - We propose that the grand canonical topological string partition functions satisfy finite-difference equations in the closed string moduli. In the case of genus... 相似文献
2.
3.
A (di)graph is supereulerian if it contains a spanning eulerian sub(di)graph. This property is a relaxation of hamiltonicity. Inspired by this analogy with hamiltonian cycles and by similar results in supereulerian graph theory, we analyze a number of sufficient Ore type conditions for a digraph to be supereulerian. Furthermore, we study the following conjecture due to Thomassé and the first author: if the arc‐connectivity of a digraph is not smaller than its independence number, then the digraph is supereulerian. As a support for this conjecture we prove it for digraphs that are semicomplete multipartite or quasitransitive and verify the analogous statement for undirected graphs. 相似文献
4.
5.
6.
Alessandro Morando Paola Trebeschi Tao Wang 《Journal of Differential Equations》2019,266(9):5397-5430
We show the short-time existence and nonlinear stability of vortex sheets for the nonisentropic compressible Euler equations in two spatial dimensions, based on the weakly linear stability result of Morando and Trebeschi (2008) [20]. The missing normal derivatives are compensated through the equations of the linearized vorticity and entropy when deriving higher-order energy estimates. The proof of the resolution for this nonlinear problem follows from certain a priori tame estimates on the effective linear problem in the usual Sobolev spaces and a suitable Nash–Moser iteration scheme. 相似文献
7.
We report studies on the structure of the metallic core and the alkyl cap layer in monolayer protected gold nanoparticles having sizes down to 1.6 nm. These particles are obtained by laser ablating gold targets in alkane-thiol solutions at different concentrations. The electronic structure of gold core and the vibrational properties of the capping hydrocarbon chains reveal effects connected with the nanosized nature of the particles. 相似文献
8.
Alessandro Conflitti 《Finite Fields and Their Applications》2003,9(4):423-431
We propose a probabilistic algorithm to reduce computing the greatest common divisor of m polynomials over a finite field (which requires computing m−1 pairwise greatest common divisors) to computing the greatest common divisor of two polynomials over the same field. 相似文献
9.
Alessandro Cecchi Giuditta Bartalucci Cinzia Chiappe Roberto Bianchini 《国际化学动力学杂志》2007,39(4):197-203
The kinetics of the electrophilic bromination of three allylic ethers in a nonprotic solvent, 1,2‐dichloroethane, has been investigated. Two of them followed a prevalent second‐order pathway, while the third one exhibited a classical, clean third order. The second‐order pathway in the first two olefins is attributed to electrophilic assistance of the ethereal oxygen to the attacking bromine molecule. In the molecular bromination of 2,4‐cis‐dimethyl‐8‐oxabicyclo[3.2.1]‐6‐octen‐3‐cis‐ol, opposite temperature dependences were found for the two different kinetic pathways. An exoergonic process for the second‐order reaction was explained by the lesser stability of the bromiranium–bromide ionic intermediate, compared to the bromiranium–tribromide in the third‐order profile. © 2007 Wiley Periodicals, Inc. 39: 197–203, 2007 相似文献
10.
We present a new generic problem solving approach for over-constrained problems based on Max-SAT. We first define a Boolean
clausal form formalism, called soft CNF formulas, that deals with blocks of clauses instead of individual clauses, and that allows one to declare each block either as hard (i.e., must be satisfied by any solution) or soft (i.e., can be violated by some solution). We then present two Max-SAT solvers that find a truth assignment that satisfies
all the hard blocks of clauses and the maximum number of soft blocks of clauses. Our solvers are branch and bound algorithms
equipped with original lazy data structures, powerful inference techniques, good quality lower bounds, and original variable
selection heuristics. Finally, we report an experimental investigation on a representative sample of instances (random 2-SAT,
Max-CSP, graph coloring, pigeon hole and quasigroup completion) which provides experimental evidence that our approach is
very competitive compared with the state-of-the-art approaches developed in the CSP and SAT communities.
Research partially supported by projects TIN2004-07933-C03-03 and TIC2003-00950 funded by the Ministerio de Educación y Ciencia. The second author is supported by a grant Ramón y Cajal. 相似文献