全文获取类型
收费全文 | 2864篇 |
免费 | 366篇 |
国内免费 | 343篇 |
专业分类
化学 | 364篇 |
晶体学 | 12篇 |
力学 | 283篇 |
综合类 | 98篇 |
数学 | 2190篇 |
物理学 | 626篇 |
出版年
2024年 | 5篇 |
2023年 | 20篇 |
2022年 | 48篇 |
2021年 | 70篇 |
2020年 | 98篇 |
2019年 | 75篇 |
2018年 | 76篇 |
2017年 | 103篇 |
2016年 | 111篇 |
2015年 | 85篇 |
2014年 | 89篇 |
2013年 | 217篇 |
2012年 | 142篇 |
2011年 | 145篇 |
2010年 | 156篇 |
2009年 | 181篇 |
2008年 | 173篇 |
2007年 | 207篇 |
2006年 | 153篇 |
2005年 | 188篇 |
2004年 | 139篇 |
2003年 | 130篇 |
2002年 | 115篇 |
2001年 | 99篇 |
2000年 | 100篇 |
1999年 | 83篇 |
1998年 | 80篇 |
1997年 | 68篇 |
1996年 | 62篇 |
1995年 | 45篇 |
1994年 | 52篇 |
1993年 | 28篇 |
1992年 | 34篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 15篇 |
1984年 | 27篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1975年 | 2篇 |
排序方式: 共有3573条查询结果,搜索用时 31 毫秒
111.
《Angewandte Chemie (International ed. in English)》2017,56(5):1411-1415
Tetratrifylpropene (TTP) has been developed as a highly acidic, allylic C–H acid for Brønsted and Lewis acid catalysis. It can readily be obtained in two steps and consistently shows exceptional catalytic activities for Mukaiyama aldol, Hosomi–Sakurai, and Friedel–Crafts acylation reactions. X‐ray analyses of TTP and its salts confirm its designed, allylic structure, in which the negative charge is delocalized over four triflyl groups. NMR experiments, acidity measurements, and theoretical investigations provide further insights to rationalize the remarkable reactivity of TTP. 相似文献
112.
113.
114.
115.
In this article, we prove some strong and weak convergence theorems for quasi-nonexpansive multivalued mappings in Banach spaces. The iterative process used is independent of Ishikawa iterative process and converges faster. Some examples are provided to validate our results. Our results extend and unify some results in the contemporary literature. 相似文献
116.
The purpose of this paper is to study a new two-step iterative scheme with mean errors of mixed type for two asymptotically nonexpansive self-mappings and two asymptotically nonexpansive nonself-mappin... 相似文献
117.
Amirali Sadeqi Shapour Moradi Kourosh Heidari Shirazi 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2020,26(1):55-79
ABSTRACTThe scope of output-only/blind identification is restricted to stochastic/statistical processes, but for the first time in this study, the detectability conditions for general output-only subspace identification are investigated. This aids the range of input sources to be extended in a much realistic manner, beyond the only stochastic inputs. For this purpose, the subspace framework is assigned to make a connection between the output signal contents and the LTI system order. A few substantial hypotheses and algebraic statements are propounded affirming the sufficiency of the genuine output sequences for the identification purpose. This can be perceived as the cornerstone of state-space model reconstruction. In order to consolidate the notions according to reality, several examples are studied and examined for different input classes with stochastic disturbance. 相似文献
118.
119.
Both residual Cesàro alpha-integrability (RCI( α)) and strongly residual Cesàro alpha-integrability (SRCI(α)) are two special kinds of extensions to uniform integrability, and both asymp-totically almost negative association (AANA) and asymptotically quadrant sub-independence (AQSI) are two special kinds of dependence structures. By relating the RCI(α) property as well as the SRCI(α) property with dependence condition AANA or AQSI, we formulate some tail-integrability conditions under which for appropriate α the RCI(α) property yields L1-convergence results and the SRCI(α) property yields strong laws of large numbers, which is the continuation of the corresponding literature. 相似文献
120.
Based on the Modified Couple Stress Theory,a functionally graded micro-beam under electrostatic forces is studied.The FGM micro-beam is made of two materials and material properties vary continuously along the beam thickness according to a power-law.Dynamic and static pull-in voltages are obtained and it is shown that the static and dynamic pull-in voltages for some materials cannot be obtained using classic theories and components of couple stress must be taken into account.In addition,it is shown that the values of pull-in voltages depend on the variation through the thickness of the volume fractions of the two constituents. 相似文献