全文获取类型
收费全文 | 79201篇 |
免费 | 23414篇 |
国内免费 | 17041篇 |
专业分类
化学 | 49494篇 |
晶体学 | 980篇 |
力学 | 5304篇 |
综合类 | 20篇 |
数学 | 10601篇 |
物理学 | 53257篇 |
出版年
2023年 | 698篇 |
2022年 | 741篇 |
2021年 | 709篇 |
2020年 | 936篇 |
2019年 | 1440篇 |
2018年 | 1402篇 |
2017年 | 2048篇 |
2016年 | 2290篇 |
2015年 | 2456篇 |
2014年 | 2262篇 |
2013年 | 4195篇 |
2012年 | 4520篇 |
2011年 | 6087篇 |
2010年 | 9377篇 |
2009年 | 9538篇 |
2008年 | 3551篇 |
2007年 | 3082篇 |
2006年 | 2723篇 |
2005年 | 3079篇 |
2004年 | 4029篇 |
2003年 | 3213篇 |
2002年 | 3001篇 |
2001年 | 3126篇 |
2000年 | 2304篇 |
1999年 | 2538篇 |
1998年 | 2167篇 |
1997年 | 1996篇 |
1996年 | 2323篇 |
1995年 | 2768篇 |
1994年 | 2834篇 |
1993年 | 2894篇 |
1992年 | 2470篇 |
1991年 | 2113篇 |
1990年 | 1777篇 |
1989年 | 1875篇 |
1988年 | 1877篇 |
1987年 | 1158篇 |
1986年 | 1204篇 |
1985年 | 903篇 |
1984年 | 1023篇 |
1982年 | 932篇 |
1981年 | 772篇 |
1980年 | 809篇 |
1979年 | 564篇 |
1978年 | 554篇 |
1977年 | 660篇 |
1976年 | 1060篇 |
1973年 | 442篇 |
1972年 | 534篇 |
1971年 | 442篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Meccanica - The static limit analysis of axially symmetric masonry domes subject to pseudo-static seismic forces is addressed. The stress state in the dome is represented by the shell stress... 相似文献
3.
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
4.
量子自旋液体是最近几年刚被人们证实除铁磁体、反铁磁体之外的第三种磁性类型,因其有望解释高温超导的运行机制、改变计算机硬盘信息存储方式而在物理、材料等领域备受关注。自旋阻挫作为量子自旋液体的最小单元可能是解开量子自旋液体诸多问题的钥匙,所以在磁学、电学研究领域再一次成为人们研究的热点。基于文献报道的三核铜配合物[Cu3(μ3-OH)(μ-OPz)3(NO3)2(H2O)2]·CH3OH(1),我们合成了三维金属有机框架配合物{[Ag(HOPz)Cu3(μ3-OH)(NO3)3(OPz)2Ag(NO3)]·6H2O}n(2)(HOPz=甲基(2-吡嗪基)酮肟),并从自旋阻挫的角度对二者磁性质进行对比和详细分析。磁化率数据表明自旋间有很强的反铁磁相互作用和反对称交换。通过包含各向同性和反对称交换的哈密顿算符对两者磁学数据进行拟合并研究其磁构关系,所获最佳拟合参数为:配合物1:Jav=-426 cm^-1,g⊥=1.83,g∥=2.00;配合物2:Jav=-401 cm^-1,g⊥=1.85,g∥=2.00。 相似文献
5.
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
6.
7.
Carello Giuliana Landa Paolo Tnfani Elena Testi Angela 《Central European Journal of Operations Research》2022,30(1):159-187
Central European Journal of Operations Research - In the past years, the number of patients in need of chemotherapy treatments has been constantly increasing. Chemotherapy treatments must be... 相似文献
8.
Vito Gigante Laura Aliotta Maria Beatrice Coltelli Patrizia Cinelli Luigi Botta Francesco Paolo La Mantia Andrea Lazzeri 《Journal of polymer science. Part A, Polymer chemistry》2020,58(23):3264-3282
The development of biodegradable materials for tailored applications, particularly in the field of polymeric films and sheets, is a challenging technological goal as well as a contribution to help protect the environment. Poly(lactic) acid (PLA) is a promising substitute for several oil-based polymers; however, to overcome its thermal and mechanical drawbacks, researchers have developed solutions such as blending PLA with polybutylene adipate terephthalate (PBAT), which is capable of increasing the ductility of the final material. In this study, PLA/PBAT binary blends, with minimum possible content of nonrenewable materials, were examined from processing, thermal, morphological, and rheological perspective. An optimized PLA/PBAT ratio was chosen as the polymeric basis to obtain a biodegradable formulation by adding a biobased plasticizer and appropriate fillers to produce a micrometer film with tailored flexibility and tear resistance. The processing technology involved flat-die extrusion, followed by calendering. The tearing resistance of the produced film was investigated, and the results were compared with literature data. A study on the essential work of fracture was implemented to explore the mode III out-of-plane fracture resistance starting from a trouser tear test. 相似文献
9.
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
10.