全文获取类型
收费全文 | 11146篇 |
免费 | 1069篇 |
国内免费 | 783篇 |
专业分类
化学 | 1933篇 |
晶体学 | 22篇 |
力学 | 724篇 |
综合类 | 205篇 |
数学 | 7834篇 |
物理学 | 2280篇 |
出版年
2024年 | 15篇 |
2023年 | 73篇 |
2022年 | 129篇 |
2021年 | 214篇 |
2020年 | 209篇 |
2019年 | 256篇 |
2018年 | 233篇 |
2017年 | 347篇 |
2016年 | 403篇 |
2015年 | 258篇 |
2014年 | 510篇 |
2013年 | 893篇 |
2012年 | 584篇 |
2011年 | 555篇 |
2010年 | 499篇 |
2009年 | 626篇 |
2008年 | 668篇 |
2007年 | 713篇 |
2006年 | 650篇 |
2005年 | 590篇 |
2004年 | 526篇 |
2003年 | 429篇 |
2002年 | 456篇 |
2001年 | 410篇 |
2000年 | 339篇 |
1999年 | 356篇 |
1998年 | 281篇 |
1997年 | 246篇 |
1996年 | 209篇 |
1995年 | 187篇 |
1994年 | 153篇 |
1993年 | 121篇 |
1992年 | 126篇 |
1991年 | 105篇 |
1990年 | 74篇 |
1989年 | 63篇 |
1988年 | 53篇 |
1987年 | 55篇 |
1986年 | 50篇 |
1985年 | 61篇 |
1984年 | 69篇 |
1983年 | 24篇 |
1982年 | 37篇 |
1981年 | 20篇 |
1980年 | 24篇 |
1979年 | 27篇 |
1978年 | 12篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 229 毫秒
31.
32.
33.
Eric C. Chi Liuyi Hu Arvind K. Saibaba Arvind U. K. Rao 《Journal of computational and graphical statistics》2019,28(1):36-47
We consider the problem of performing matrix completion with side information on row-by-row and column-by-column similarities. We build upon recent proposals for matrix estimation with smoothness constraints with respect to row and column graphs. We present a novel iterative procedure for directly minimizing an information criterion to select an appropriate amount of row and column smoothing, namely, to perform model selection. We also discuss how to exploit the special structure of the problem to scale up the estimation and model selection procedure via the Hutchinson estimator, combined with a stochastic Quasi-Newton approach. Supplementary material for this article is available online. 相似文献
34.
In this paper, we investigate the complete moment convergence for dependent linear processes with random coefficients to form 相似文献
35.
Rik H. Verschueren Julie Schmauck Dr. Michael S. Perryman Dr. Hui-Lan Yue Julian Riegger Dr. Bertrand Schweitzer-Chaput Dr. Martin Breugst Dr. Martin Klussmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(38):9088-9097
In this work, the reactivities of acetonyl and benzoyl radicals in aromatic substitution and addition reactions have been compared in an experimental and computational study. The results show that acetonyl is more electrophilic than benzoyl, which is rather nucleophilic. A Hammett plot analysis of the addition reactions of the two radicals to substituted styrenes clearly support the nucleophilicity of benzoyl, but in the case of acetonyl, no satisfactory linear correlation with a single substituent-related parameter was found. Computational calculations helped to rationalize this effect, and a good linear correlation was found with a combination of polar parameters (σ+) and the radical stabilization energies of the formed intermediates. Based on the calculated philicity indices for benzoyl and acetonyl, a quantitative comparison of these two radicals with many other reported radicals is possible, which may help to predict the reactivities of other aromatic radical substitution reactions. 相似文献
36.
Verena Bögelein Frank Duzaar Leah Schätzler Christoph Scheven 《Journal of Differential Equations》2019,266(11):7709-7748
We establish that solutions to the Cauchy–Dirichlet problem for functionals of linear growth can be obtained as limits of solutions to flows with p-growth in the limit . The result can be interpreted on the one hand as a stability result. On the other hand it provides an existence result for general flows with linear growth. 相似文献
37.
A linear optical unambiguous discrimination of hyperentangled Bell states is proposed for two‐photon systems entangled in both the polarization and momentum degrees of freedom (DOFs) assisted by time bin. This unambiguous discrimination scheme can completely identify 16 orthogonal hyperentangled Bell states using only linear optical elements, where the function of the auxiliary entangled Bell state is replaced by time bin. Moreover, the possibility of extending this scheme for distinguishing hyperentangled Bell states in n DOFs is discussed, and it shows that hyperentangled Bell states in n ( ) DOFs can be distinguished with k ( ) auxiliary entangled states of additional DOFs by introducing a time delay, which decreases the auxiliary entanglement resource required for unambiguous discrimination of hyperentangled Bell state. Therefore, this scheme provides a new way for distinguishing hyperentangled states with current technology, which will extend the application of discrimination of hyperentangled states via linear optics to other quantum information protocols besides hyperdense coding schemes in the future. 相似文献
38.
针对设计的一种场畸变气体开关,研究中间电极材料分别为不锈钢和黄铜条件下的烧蚀特性,结合开关寿命期间静态与触发特性的变化规律,获得决定开关寿命的关键因素,为三电极场畸变气体开关的性能优化提供理论支撑。研究结果表明,采用不锈钢和黄铜作为中间电极的烧蚀区域以及表面粗糙度均随着放电次数增加而增大,黄铜电极烧蚀较为严重且表面有明显的烧蚀圆斑,不锈钢电极则具有更高的表面粗糙度,阴阳极表面烧蚀存在明显差异,随着放电次数的增加,击穿点向电极边缘区域集中,影响开关的沿面绝缘特性,是导致开关寿命终结的主要原因。 相似文献
39.
40.