全文获取类型
收费全文 | 729篇 |
免费 | 26篇 |
国内免费 | 7篇 |
专业分类
化学 | 401篇 |
晶体学 | 13篇 |
力学 | 34篇 |
数学 | 168篇 |
物理学 | 146篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 18篇 |
2019年 | 22篇 |
2018年 | 26篇 |
2017年 | 22篇 |
2016年 | 40篇 |
2015年 | 34篇 |
2014年 | 38篇 |
2013年 | 111篇 |
2012年 | 49篇 |
2011年 | 51篇 |
2010年 | 44篇 |
2009年 | 49篇 |
2008年 | 42篇 |
2007年 | 36篇 |
2006年 | 30篇 |
2005年 | 13篇 |
2004年 | 23篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1967年 | 2篇 |
1939年 | 1篇 |
1935年 | 1篇 |
1934年 | 2篇 |
1933年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有762条查询结果,搜索用时 187 毫秒
641.
642.
643.
Yusuf Sicak Emine E. Oruç-Emre Mehmet Öztürk Ayşegül Karaküçük-İyidoğan Said Nadeem 《Journal of heterocyclic chemistry》2020,57(2):830-841
Twenty-four pyrazolo derivatives (1–4)(a-f) were synthesized and characterized by FTIR, 1H, and 13C NMR (Nuclear Magnetic Resonance), and elemental analysis. The synthesized compounds were also investigated for their antioxidant and anticholinesterase activities. The compounds (3–4)(a-f) carrying morpholine ring were more active than the piperidinyl containing compounds (1–2)(a-f) in both activities. The compound 4f showed higher activity in both assays as compared with the others. Additionally, the anticholinesterase activity test provided higher values than the galantamine in the BChE assay. Therefore, compound 4f can be used as anticholinesterase agent and/or anticholinesterase assay standard. 相似文献
644.
645.
646.
Derya Avcı Beyza Billur İskender Eroğlu Necati Özdemir 《Numerical Methods for Partial Differential Equations》2023,39(1):231-241
In this study, a heat transfer problem defined by the Caputo–Fabrizio derivative, which is known to behave by the exponential decaying law, is addressed in an axially symmetric cylindrical region. Thus, the fundamental solutions of the heat diffusion process and the associated thermal stresses are aimed to find. For this purpose, Laplace and finite Hankel integral transforms are applied according to the geometry of the region. To obtain the thermal stresses, constitutive relations of the classical thermoelasticity theory are used. The effects of fractional orders on the diffusion process are illustrated graphically using MATLAB. 相似文献
647.
İskender Muz Osman Canko Murat Atiş Erdem Kamil Yıldırım 《Journal of computational chemistry》2015,36(6):385-391
The global minimum structures of AlB3H2n (n = 0–6) clusters are determined using the stochastic search method at the B3LYP/6–31G level of theory. These initially specified geometries are recalculated using B3LYP and CCSD(T) methods using the 6–311++G** basis set. The structural and electronic properties of the two lowest‐lying isomers are presented. The structural parameters obtained for aluminum borohydride are compared with the experimental and theoretical results. The H2 fragmentation energies of the most stable isomers are investigated. Chemical bonding analyses for the global minimum of AlB3H2n (n = 0–6) clusters are performed using the adaptive natural density partitioning method. © 2014 Wiley Periodicals, Inc. 相似文献
648.
C. Yalçın Kaya 《Computational Optimization and Applications》2017,68(3):719-747
Markov–Dubins path is the shortest planar curve joining two points with prescribed tangents, with a specified bound on its curvature. Its structure, as proved by Dubins in 1957, nearly 70 years after Markov posed the problem of finding it, is elegantly simple: a selection of at most three arcs are concatenated, each of which is either a circular arc of maximum (prescribed) curvature or a straight line. The Markov–Dubins problem and its variants have since been extensively studied in practical and theoretical settings. A reformulation of the Markov–Dubins problem as an optimal control problem was subsequently studied by various researchers using the Pontryagin maximum principle and additional techniques, to reproduce Dubins’ result. In the present paper, we study the same reformulation, and apply the maximum principle, with new insights, to derive Dubins’ result again. We prove that abnormal control solutions do exist. We characterize these solutions, which were not studied adequately in the literature previously, as a concatenation of at most two circular arcs and show that they are also solutions of the normal problem. Moreover, we prove that any feasible path of the types mentioned in Dubins’ result is a stationary solution, i.e., that it satisfies the Pontryagin maximum principle. We propose a numerical method for computing Markov–Dubins path. We illustrate the theory and the numerical approach by three qualitatively different examples. 相似文献
649.
650.
Burak Kaya 《Israel Journal of Mathematics》2017,220(2):873-897
In this paper, we analyze the Borel complexity of the topological conjugacy relation on Toeplitz subshifts. More specifically, we prove that topological conjugacy of Toeplitz subshifts with separated holes is hyperfinite. Indeed, we show that the topological conjugacy relation is hyperfinite on a larger class of Toeplitz subshifts which we call Toeplitz subshifts with growing blocks. This result provides a partial answer to a question asked by Sabok and Tsankov. 相似文献