全文获取类型
收费全文 | 2241篇 |
免费 | 135篇 |
国内免费 | 49篇 |
专业分类
化学 | 1604篇 |
晶体学 | 13篇 |
力学 | 142篇 |
数学 | 266篇 |
物理学 | 400篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 37篇 |
2021年 | 83篇 |
2020年 | 113篇 |
2019年 | 105篇 |
2018年 | 132篇 |
2017年 | 105篇 |
2016年 | 163篇 |
2015年 | 121篇 |
2014年 | 162篇 |
2013年 | 266篇 |
2012年 | 178篇 |
2011年 | 169篇 |
2010年 | 152篇 |
2009年 | 131篇 |
2008年 | 134篇 |
2007年 | 87篇 |
2006年 | 45篇 |
2005年 | 34篇 |
2004年 | 33篇 |
2003年 | 30篇 |
2002年 | 19篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1974年 | 1篇 |
排序方式: 共有2425条查询结果,搜索用时 46 毫秒
1.
Clemens G. Raab Georg Regensburger Jamal Hossein Poor 《Journal of Pure and Applied Algebra》2021,225(5):106564
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials. 相似文献
2.
3.
4.
5.
Behnam Reza Roghani-Mamaqani Hossein Salami-Kalajahi Mehdi 《Journal of Thermal Analysis and Calorimetry》2019,135(6):3311-3319
Journal of Thermal Analysis and Calorimetry - Effect of different chain extenders, silica nanoparticle loading, and using sol–gel method on the thermal properties of polyurethane (PU) hybrid... 相似文献
6.
Zheng Yuanzhou Yang Haoran Mazaheri Hossein Aghaei Alireza Mokhtari Namjoo Afrand Masoud 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1425-1438
Journal of Thermal Analysis and Calorimetry - The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a... 相似文献
7.
8.
Mohammad Mazloum Ardakani Ali Asghar Ensafi Mohammad Salavati Niasari Hossain Mirhoseini 《Analytical sciences》2003,19(8):1187-1190
The performance of octahydroxycalix[4]arene derivative used as a neutral carrier for silver polymeric membrane electrode was studied. The sensor gave a good Nernstian response of 58 +/- 1 mV per decade for silver ion in the activity range 3.3 x 10(-6) to 3.3 x 10(-2) M Ag+. The limit of detection reached 2.1 x 10(-6) M Ag+ and exhibited high selectivity for silver ion against the alkali, alkaline earth and transition metal ions. The sensor can be used in wide pH range from 1.5 to 6.5. The response time of the sensor is less than 20 s. The potentiometric sensor was used as the indicator electrode in the titration of Ag+ ions by sodium chloride solution. 相似文献
9.
Ashfaque H. Bokhari Abdul R. Kashif Asghar Qadir 《General Relativity and Gravitation》2003,35(6):1059-1076
Curvature collineations are symmetry directions for the Riemann tensor, as isometries are for the metric tensor and Ricci collineations are for the Ricci tensor. Complete listings of many metrics possessing some minimal symmetry have been given for a number of symmetry groups for the latter two symmetries. It is shown that a claimed complete listing of cylindrically symmetric static metrics by their curvature collineations [1] was actually incomplete and is completed here. It turns out that in this complete list, unlike the previous claim, there are curvature collineations that are distinct from the set of isometries and of Ricci collineations. The physical interpretation of some of the metrics obtained is given. 相似文献
10.
Hossein A. Oskooie Majid M. Heravi Khadijeh Bakhtiari Shima Taheri 《Monatshefte für Chemie / Chemical Monthly》2007,138(9):875-877
Summary. A facile synthesis of quinoxaline derivatives catalyzed by KHSO4 in very high yields at room temperature is reported. 相似文献