全文获取类型
收费全文 | 55794篇 |
免费 | 4862篇 |
国内免费 | 4264篇 |
专业分类
化学 | 22381篇 |
晶体学 | 458篇 |
力学 | 4506篇 |
综合类 | 577篇 |
数学 | 11336篇 |
物理学 | 25662篇 |
出版年
2024年 | 94篇 |
2023年 | 509篇 |
2022年 | 1268篇 |
2021年 | 1256篇 |
2020年 | 1282篇 |
2019年 | 1309篇 |
2018年 | 1171篇 |
2017年 | 1403篇 |
2016年 | 1564篇 |
2015年 | 1309篇 |
2014年 | 2027篇 |
2013年 | 3548篇 |
2012年 | 2328篇 |
2011年 | 2595篇 |
2010年 | 2058篇 |
2009年 | 3207篇 |
2008年 | 3504篇 |
2007年 | 3861篇 |
2006年 | 3304篇 |
2005年 | 2634篇 |
2004年 | 2275篇 |
2003年 | 2515篇 |
2002年 | 2866篇 |
2001年 | 2162篇 |
2000年 | 2090篇 |
1999年 | 1754篇 |
1998年 | 1721篇 |
1997年 | 1052篇 |
1996年 | 976篇 |
1995年 | 837篇 |
1994年 | 871篇 |
1993年 | 642篇 |
1992年 | 720篇 |
1991年 | 490篇 |
1990年 | 459篇 |
1989年 | 360篇 |
1988年 | 324篇 |
1987年 | 311篇 |
1986年 | 280篇 |
1985年 | 269篇 |
1984年 | 254篇 |
1983年 | 154篇 |
1982年 | 214篇 |
1981年 | 217篇 |
1980年 | 135篇 |
1979年 | 166篇 |
1978年 | 141篇 |
1977年 | 131篇 |
1976年 | 91篇 |
1973年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
182.
Hidetoshi Shimodaira 《Annals of the Institute of Statistical Mathematics》1997,49(3):395-410
The asymptotic error probability of Linhart's model selection test isevaluated, and compared with the nominal significance level. We examine thecase where the expected discrepancies of the candidate models from the truemodel are asymptotically equal. The local alternatives method is employed inthe limiting operation of the asymptotic evaluation. Although the errorprobability under the null hypothesis is actually shown to be equal to orless than the level for most situations, intolerable violations of the errorcontrol are observed for nested models: It is often erroneously concludedthat the smaller model is significantly better than the larger model. Toprevent this violation, a modification of Linhart's test statistic isproposed. The effectiveness of the proposed test is confirmed throughtheoretical analysis and numerical simulations. 相似文献
183.
We show that the LF-algebra considered by Akkar and Nacir in [1] is topologically simple. 相似文献
184.
采用MSDI严格角动量投影46Ti、48Cr形变HF谱 总被引:1,自引:1,他引:0
采用修正的表面δ相互作用(MSDI),以球形壳模型单粒子态作基矢,对fp壳层区偶偶核46Ti、48Cr进行形变Hartree–Fock(HF)计算,并用形变HF单粒子态构造Slater行列式波函数,即形变HF内禀态,然后对其实施严格角动量投影程序,得到比较合理的结果. 相似文献
185.
186.
Fusion-evaporation cross-sections for the α-induced reactions upon197Au,193Ir,191Ir,185Re,181Ta,121Sb and69Ga nuclei at bombarding energies near the Coulomb barrier have been measured by off-line observation of the γ-rays emitted
in the radioactive decay of the residual nuclei using stacked foil technique. The total fusion cross-section for the systems
have been compared with simple statistical model calculations using the code ALICE/91 as well as with the coupled channel
calculations that include the β2 and ν4 slatic deformations and dynamic couplings of the vibrational/rotational states of the target and the projet tile using the
code CCDEF. 相似文献
187.
设计一种用归零码及多重相关解调技术的传输方案,并给了所需的几种抗干扰单元电路,最后结合实验说明了此方案可提高不良环境下传输数据的置信率。 相似文献
188.
This paper describes a method and the corresponding algorithms for simplification of large-scale linear programming models. It consists of the elimination of the balance constraints (i.e. constraints with zero RHS term). The idea is to apply some linear transformations to the original problem in order to nullify the balance constraints. These transformations are able to simultaneously eliminate more balance rows. The core of this contribution is the introduction of the reduction matrix and the associated theorems on the equivalent linear programs (original and reduced). The numerical experiments with this method of simplification proved this approach to be beneficial for a large class of LP problems.This research work was done while the first author was at Duisburg University, Mess-, Steuer und Regelungstechnik, Germany, under the greatly appreciated financial assistance given by the Alexander-von-Humboldt Foundation. 相似文献
189.
190.
Recently extremal double circulant self-dual codes have been classified for lengths n ≤ 62. In this paper, a complete classification
of extremal double circulant self-dual codes of lengths 64 to 72 is presented. Almost all of the extremal double circulant
singly-even codes given have weight enumerators for which extremal codes were not previously known to exist. 相似文献