全文获取类型
收费全文 | 35980篇 |
免费 | 256篇 |
国内免费 | 281篇 |
专业分类
化学 | 14465篇 |
晶体学 | 461篇 |
力学 | 1541篇 |
综合类 | 12篇 |
数学 | 10124篇 |
物理学 | 9914篇 |
出版年
2022年 | 119篇 |
2021年 | 179篇 |
2020年 | 125篇 |
2019年 | 160篇 |
2018年 | 1326篇 |
2017年 | 1581篇 |
2016年 | 935篇 |
2015年 | 748篇 |
2014年 | 726篇 |
2013年 | 1246篇 |
2012年 | 3404篇 |
2011年 | 2641篇 |
2010年 | 2065篇 |
2009年 | 1781篇 |
2008年 | 889篇 |
2007年 | 912篇 |
2006年 | 856篇 |
2005年 | 4622篇 |
2004年 | 4103篇 |
2003年 | 2498篇 |
2002年 | 656篇 |
2001年 | 449篇 |
2000年 | 232篇 |
1999年 | 275篇 |
1998年 | 221篇 |
1997年 | 155篇 |
1996年 | 129篇 |
1995年 | 156篇 |
1994年 | 112篇 |
1993年 | 79篇 |
1992年 | 243篇 |
1991年 | 201篇 |
1990年 | 207篇 |
1989年 | 172篇 |
1988年 | 166篇 |
1987年 | 119篇 |
1986年 | 111篇 |
1985年 | 140篇 |
1984年 | 148篇 |
1983年 | 98篇 |
1982年 | 88篇 |
1981年 | 97篇 |
1980年 | 98篇 |
1979年 | 87篇 |
1978年 | 89篇 |
1977年 | 89篇 |
1976年 | 143篇 |
1975年 | 96篇 |
1974年 | 90篇 |
1973年 | 91篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
JingXiaWANG ChengYouKAN DeShanLIU 《中国化学快报》2004,15(10):1161-1163
Two novel polymerizable dyes with anthraquinone residue have been prepared, and their structures were characterized by FTIR, ^1HNMR and EA. 相似文献
32.
33.
Paramagnetic pyrroline and 1,2,3,6-tetrahydropyridine derivatives of BODIPY and their diamagnetic analogs have been synthesized and characterized as novel redox double sensor and cation sensitive reagents. 相似文献
34.
35.
Jan Cieliski 《Chaos, solitons, and fractals》1995,5(12):2303-2313
An effective algorithm to construct the Darboux matrix based on the dressing method is proposed. Our approach consists in representing the linear problem as a system of algebraic constraints on two matrices. The Darboux matrix is determined from the requirement that the Darboux-Bäcklund transformation preserves these constraints. A non-isospectral deformation of the derivative nonlinear Schrödinger equation is discussed as an example. 相似文献
36.
S. Kwieciński M. Weychert A. Jasiński P. Kulinowski I. Wawer E. Sieradzki 《Applied magnetic resonance》2002,22(1):23-29
The disintegration of bromhexin tablets was monitored by magnetic resonance imaging. The fast imaging method FLASH with spoiling
gradients was used to obtain images of the tablets in short time intervals. The rate of the disintegration depends on the
preparation method, kind and percentage of the carrier (polyethylene glycol, lactose). Solid dispersion with slow evaporation
of solvent yields materials with decreased dissolution rate. Increasing molecular mass of polyethylene glycol and its percentage
content also hampers disintegration. 相似文献
37.
Supported by SFB 170 “Geometrie und Analysis” at the University of G?ttingen 相似文献
38.
Zdzislaw Skupień 《Graphs and Combinatorics》1993,9(2-4):353-363
The aim of this paper is to introduce the notions of floor and ceiling functions related to graph edge-decompositions intot mutually isomorphic parts. It is shown that, given any natural numbert, uniform and extremal t-packing andt-covering exist for each complete graph and each complete bipartite graph. Extremal in this context means that both a remainder and a surplus are absolutely minimum. In proofs, decompositions of multigraphs into matchings are involved. Open problems and conjectures are stated. 相似文献
39.
We prove that RANDOM EDGE, the simplex algorithm that always chooses a random improving edge to proceed on, can take a mildly exponential number of steps in the model of abstract objective functions (introduced by Williamson Hoke [Completely unimodal numberings of a simple polytope, Discrete Appl. Math. 20 (1988) 69-81.] and by Kalai [A simple way to tell a simple polytope from its graph, J. Combin. Theory Ser. A 49(2) (1988) 381-383.] under different names). We define an abstract objective function on the n-dimensional cube for which the algorithm, started at a random vertex, needs at least exp(const·n1/3) steps with high probability. The best previous lower bound was quadratic. So in order for RANDOM EDGE to succeed in polynomial time, geometry must help. 相似文献
40.
Finitely generated linear semigroups over a field K that have intermediate growth are considered. New classes of such semigroups are found and a conjecture on the equivalence of the subexponential growth of a finitely generated linear semigroup S and the nonexistence of free noncommutative subsemigroups in S, or equivalently the existence of a nontrivial identity satisfied in S, is stated. This ‘growth alternative’ conjecture is proved for linear semigroups of degree 2, 3 or 4. Certain results supporting the general conjecture are obtained. As the main tool, a new combinatorial property of groups is introduced and studied. 相似文献