全文获取类型
收费全文 | 8387篇 |
免费 | 245篇 |
国内免费 | 30篇 |
专业分类
化学 | 6276篇 |
晶体学 | 89篇 |
力学 | 99篇 |
综合类 | 1篇 |
数学 | 442篇 |
物理学 | 1755篇 |
出版年
2023年 | 41篇 |
2021年 | 82篇 |
2020年 | 117篇 |
2019年 | 115篇 |
2018年 | 79篇 |
2017年 | 67篇 |
2016年 | 146篇 |
2015年 | 144篇 |
2014年 | 189篇 |
2013年 | 424篇 |
2012年 | 378篇 |
2011年 | 470篇 |
2010年 | 262篇 |
2009年 | 263篇 |
2008年 | 462篇 |
2007年 | 461篇 |
2006年 | 476篇 |
2005年 | 491篇 |
2004年 | 465篇 |
2003年 | 326篇 |
2002年 | 281篇 |
2001年 | 200篇 |
2000年 | 181篇 |
1999年 | 91篇 |
1998年 | 56篇 |
1997年 | 78篇 |
1996年 | 99篇 |
1995年 | 81篇 |
1994年 | 97篇 |
1993年 | 106篇 |
1992年 | 125篇 |
1991年 | 106篇 |
1990年 | 82篇 |
1989年 | 101篇 |
1988年 | 89篇 |
1987年 | 65篇 |
1986年 | 67篇 |
1985年 | 127篇 |
1984年 | 145篇 |
1983年 | 74篇 |
1982年 | 94篇 |
1981年 | 87篇 |
1980年 | 82篇 |
1979年 | 92篇 |
1978年 | 80篇 |
1977年 | 94篇 |
1976年 | 68篇 |
1975年 | 60篇 |
1974年 | 62篇 |
1973年 | 62篇 |
排序方式: 共有8662条查询结果,搜索用时 93 毫秒
1.
Yasuhito Tanaka 《Operations Research Letters》2019,47(5):406-409
We study a dynamic free-entry oligopoly with sluggish entry and exit of firms under general demand and cost functions. We show that the number of firms in a steady-state open-loop solution for a dynamic free-entry oligopoly is smaller than that at static equilibrium and that the number of firms in a steady-state memoryless closed-loop solution is larger than that in an open-loop solution. 相似文献
2.
Masaharu Ueno Satoshi D. Ohmura Makoto Wada Norikazu Miyoshi 《Tetrahedron letters》2019,60(7):570-573
We developed an environmentally friendly method for aerobic oxidation of alcohols using a commercially available, relatively benign bismuth salt as a catalyst. We found that the catalytic combination of BiBr3 with nitric acid is key for enhancing the reactivity. The reaction proceeds well under air, making the use of pure oxygen unnecessary. Each of the primary or secondary alcohols tested was oxidized to the corresponding aldehydes or ketones using this protocol. 相似文献
3.
Numerical Algorithms - The LP-Newton method solves linear programming (LP) problems by repeatedly projecting a current point onto a certain relevant polytope. In this paper, we extend the... 相似文献
4.
5.
Aoshima Makoto Yata Kazuyoshi 《Annals of the Institute of Statistical Mathematics》2019,71(3):473-503
Annals of the Institute of Statistical Mathematics - We consider classifiers for high-dimensional data under the strongly spiked eigenvalue (SSE) model. We first show that high-dimensional data... 相似文献
6.
Shigeaki Koike Takahiro Kosugi Makoto Naito 《Journal of Mathematical Analysis and Applications》2018,457(1):436-460
The rate of convergence of approximate solutions via penalization for free boundary problems are concerned. A key observation is to obtain global bounds of penalized terms which give necessary estimates on integrations by the nonlinear adjoint method by L.C. Evans. 相似文献
7.
8.
9.
9,10‐Diaminoanthracenes Revisited: The Influence of N‐Substituents on Their Electronic States 下载免费PDF全文
Masashi Uebe Prof. Dr. Tatsuhisa Kato Prof. Dr. Kazuyoshi Tanaka Dr. Akihiro Ito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18923-18931
The electronic and molecular structures of 9,10‐diamino‐substituted anthracenes with different N‐substituents have been re‐examined. In particular, different N‐substituents influence both the electronic and molecular structures of the oxidized species of 9,10‐diaminoanthracenes. The anthrylene moiety of 9,10‐bis(N,N‐di(p‐anisyl)amino)anthracene retains its planarity during the course of two successive one‐electron oxidations, whereas 9,10‐bis(N,N‐dimethylamino)anthracene and 9,10‐bis(N‐p‐anisyl‐N‐methylamino)anthracene undergo a substantial structural change to a butterfly‐like structure through a two‐electron oxidation process. The structural changes observed for the oxidized states are ascribed to significant differences in the frontier molecular orbitals of the above‐mentioned three kinds of 9,10‐diaminoanthracenes due to different extents of mixing between the amine‐localized and anthrylene‐localized orbitals. 相似文献
10.
Shota Ooi Takayuki Tanaka Kyu Hyung Park Dongho Kim Atsuhiro Osuka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(22):6645-6649
The oxidation of 10–10′ singly linked corrole dimers with DDQ at low concentration in CHCl3 afforded meso–meso, β–β, β–β triply linked 2H‐corrole dimers (with two inner NH groups in each corrole unit), which exhibited characteristic 1H NMR and absorption spectra attributable to their nonaromatic electronic networks. These 2H‐corrole dimers were reduced with NaBH4 to aromatic 3H‐corrole dimers, which were unstable and easily oxidized back to the 2H‐corrole dimers upon exposure to air. Bis(zinc(II)) complexes of the 2H‐corrole dimers were synthesized and characterized as rare examples of nonaromatic zinc(II) corrole complexes. 相似文献