全文获取类型
收费全文 | 2279篇 |
免费 | 130篇 |
国内免费 | 11篇 |
专业分类
化学 | 1453篇 |
力学 | 62篇 |
数学 | 518篇 |
物理学 | 387篇 |
出版年
2023年 | 29篇 |
2022年 | 15篇 |
2021年 | 58篇 |
2020年 | 41篇 |
2019年 | 38篇 |
2018年 | 46篇 |
2017年 | 42篇 |
2016年 | 108篇 |
2015年 | 101篇 |
2014年 | 97篇 |
2013年 | 189篇 |
2012年 | 159篇 |
2011年 | 162篇 |
2010年 | 121篇 |
2009年 | 88篇 |
2008年 | 117篇 |
2007年 | 141篇 |
2006年 | 111篇 |
2005年 | 111篇 |
2004年 | 86篇 |
2003年 | 61篇 |
2002年 | 65篇 |
2001年 | 35篇 |
2000年 | 30篇 |
1999年 | 17篇 |
1998年 | 17篇 |
1997年 | 23篇 |
1996年 | 18篇 |
1995年 | 17篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 21篇 |
1991年 | 15篇 |
1990年 | 20篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1974年 | 7篇 |
1934年 | 11篇 |
排序方式: 共有2420条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
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
6.
7.
Robert Andreu Gerard Lligadas Joan Carles Ronda Marina Galià Virginia Cádiz 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4965-4973
A new oxazolidine derivative was obtained from phenol, 2‐amino‐2‐methylpropane‐1,3‐diol and paraformaldehyde. The reaction of this novel oxazolidine diol with phenylisocyanate lead to a urethane model compound which can be polymerized thermally by oxazolidine ring opening to give a Mannich bridge structure. Linear segmented polyurethanes were prepared by reaction of different ratios of oxazolidine diol and commercial polyethylenglycol (Mw ~ 400) with 4,4′‐methylenbis (cyclohexylisocyanate) (HMDI, 90% isomers mixture). The polyurethanes were thermally characterized and crosslinked by oxazolidine ring opening to obtain materials which showed improved thermal stability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4965–4973, 2007 相似文献
8.
Optimality conditions are obtained for a nonlinear fractional multiobjective programming problem involving η-semidifferentiable functions. Also, a general dual is formulated and a duality result is proved using concepts of generalized ρ-semilocally type I-preinvex functions. 相似文献
9.
Hà Huy Tài 《manuscripta mathematica》2002,107(4):479-501
Suppose ? is a set of arbitrary number of smooth points in ℙ2
its defining ideal. In this paper, we study the Rees algebras of the ideals generated by I
t
, t ≥α. When the points of ? are general, we give a set of defining equations for the Rees algebra . When the points of ? are arbitrary, we show that for all t≫ 0, the Rees algebra is Cohen-Macaulay and its defining ideal is generated by quadratics. A cohomological characterization for arithmetic Cohen-Macaulayness
of subvarieties of a product space is also given.
Received 4 April 2001 相似文献
10.