全文获取类型
收费全文 | 13861篇 |
免费 | 543篇 |
国内免费 | 1217篇 |
专业分类
化学 | 9246篇 |
晶体学 | 134篇 |
力学 | 301篇 |
综合类 | 10篇 |
数学 | 2086篇 |
物理学 | 3844篇 |
出版年
2022年 | 76篇 |
2021年 | 120篇 |
2020年 | 165篇 |
2019年 | 167篇 |
2018年 | 196篇 |
2017年 | 201篇 |
2016年 | 336篇 |
2015年 | 313篇 |
2014年 | 356篇 |
2013年 | 951篇 |
2012年 | 828篇 |
2011年 | 908篇 |
2010年 | 528篇 |
2009年 | 616篇 |
2008年 | 647篇 |
2007年 | 553篇 |
2006年 | 599篇 |
2005年 | 568篇 |
2004年 | 869篇 |
2003年 | 646篇 |
2002年 | 618篇 |
2001年 | 334篇 |
2000年 | 256篇 |
1999年 | 251篇 |
1998年 | 214篇 |
1997年 | 191篇 |
1996年 | 200篇 |
1995年 | 154篇 |
1994年 | 146篇 |
1993年 | 150篇 |
1992年 | 144篇 |
1991年 | 113篇 |
1990年 | 124篇 |
1989年 | 100篇 |
1988年 | 92篇 |
1987年 | 83篇 |
1986年 | 98篇 |
1985年 | 141篇 |
1984年 | 149篇 |
1983年 | 128篇 |
1982年 | 159篇 |
1981年 | 133篇 |
1980年 | 124篇 |
1979年 | 127篇 |
1978年 | 136篇 |
1977年 | 138篇 |
1976年 | 142篇 |
1975年 | 121篇 |
1974年 | 110篇 |
1973年 | 110篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
1.
2.
3.
4.
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
5.
Lubomír Havlk Jan Fbry Margarida Henriques Michal Duek 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(7):623-630
The title structures of KScS2 (potassium scandium sulfide), RbScS2 (rubidium scandium sulfide) and KLnS2 [Ln = Nd (potassium neodymium sufide), Sm (potassium samarium sulfide), Tb (potassium terbium sulfide), Dy (potassium dysprosium sulfide), Ho (potassium holmium sulfide), Er (potassium erbium sulfide), Tm (potassium thulium sulfide) and Yb (potassium ytterbium sulfide)] are either newly determined (KScS2, RbScS2 and KTbS2) or redetermined. All of them belong to the α‐NaFeO2 structure type in agreement with the ratio of the ionic radii r3+/r+. KScS2, the member of this structural family with the smallest trivalent cation, is an extreme representative of these structures with rare earth trivalent cations. The title structures are compared with isostructural alkali rare earth sulfides in plots showing the dependence of several relevant parameters on the trivalent cation crystal radius; the parameters thus compared are c, a and c/a, the thicknesses of the S—S layers which contain the respective constituent cations, the sulfur fractional coordinates z(S2−) and the bond‐valence sums. 相似文献
6.
Simen Gjelseth Antonsen Arne Joakim C. Bunkan Tomas Mikoviny Yngve Stenstrøm Armin Wisthaler 《Molecular physics》2020,118(15)
The kinetics of the O3, OH and NO3 radical reactions with diazomethane were studied in smog chamber experiments employing long-path FTIR and PTR-ToF-MS detection. The rate coefficients were determined to be k CH2NN+O3?=?(3.2?±?0.4)?×?10?17 and k CH2NN+OH?=?(1.68?±?0.12)?×?10?10 cm3 molecule?1 s?1 at 295?±?3?K and 1013?±?30 hPa, whereas the CH2NN?+?NO3 reaction was too fast to be determined in the static smog chamber experiments. Formaldehyde was the sole product observed in all the reactions. The experimental results are supported by CCSD(T*)-F12a/aug-cc-pVTZ//M062X/aug-cc-pVTZ calculations showing the reactions to proceed exclusively via addition to the carbon atom. The atmospheric fate of diazomethane is discussed. 相似文献
7.
8.
9.
It is proved that biorthogonal polynomials obey two different kinds of Christoffel-Darboux-type formulae, one linking polynomials with a different parameter and one combining polynomials with different degrees. This is used to produce a mixed recurrence relation, which is valid for all biorthogonal polynomials. This recurrence relation establishes several results on interlacing property of zeros of successive biorthogonal polynomials and leads to a new result on the interlace of zeros of orthogonal polynomials (of equal degrees) with respect to two distributionsdψ(x) andx p dψ(x), 0<p≤1, with support in either [0, 1] or [1, ∞). 相似文献
10.
Kasper K. Berthelsen Jesper Møller 《Bulletin of the Brazilian Mathematical Society》2002,33(3):351-367
This primer provides a self-contained exposition of the case where spatial birth-and-death processes are used for perfect
simulation of locally stable point processes. Particularly, a simple dominating coupling from the past (CFTP) algorithm and
the CFTP algorithms introduced in [13], [14], and [5] are studied. Some empirical results for the algorithms are discussed.
Received: 30 June 2002 相似文献