全文获取类型
收费全文 | 16397篇 |
免费 | 901篇 |
国内免费 | 1437篇 |
专业分类
化学 | 12941篇 |
晶体学 | 131篇 |
力学 | 325篇 |
综合类 | 10篇 |
数学 | 2227篇 |
物理学 | 3101篇 |
出版年
2023年 | 112篇 |
2022年 | 73篇 |
2021年 | 353篇 |
2020年 | 283篇 |
2019年 | 322篇 |
2018年 | 261篇 |
2017年 | 265篇 |
2016年 | 607篇 |
2015年 | 503篇 |
2014年 | 568篇 |
2013年 | 1242篇 |
2012年 | 1350篇 |
2011年 | 1455篇 |
2010年 | 833篇 |
2009年 | 1058篇 |
2008年 | 1030篇 |
2007年 | 1003篇 |
2006年 | 852篇 |
2005年 | 888篇 |
2004年 | 1163篇 |
2003年 | 812篇 |
2002年 | 721篇 |
2001年 | 343篇 |
2000年 | 260篇 |
1999年 | 201篇 |
1998年 | 191篇 |
1997年 | 169篇 |
1996年 | 175篇 |
1995年 | 155篇 |
1994年 | 113篇 |
1993年 | 136篇 |
1992年 | 115篇 |
1991年 | 76篇 |
1990年 | 80篇 |
1989年 | 64篇 |
1988年 | 67篇 |
1987年 | 55篇 |
1986年 | 64篇 |
1985年 | 89篇 |
1984年 | 90篇 |
1983年 | 66篇 |
1982年 | 57篇 |
1981年 | 59篇 |
1980年 | 50篇 |
1979年 | 32篇 |
1978年 | 28篇 |
1977年 | 35篇 |
1976年 | 26篇 |
1975年 | 24篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
1.
Zlámalová M. Pitňa Lásková B. Vinarčíková M. Zukalová M. Kavan L. 《Journal of Solid State Electrochemistry》2022,26(3):639-647
Journal of Solid State Electrochemistry - The addition of nanocrystalline titanium dioxide (P90) to a cathode of Li/S cell enhances its voltammetric charge capacity by 19%, from which only a small... 相似文献
2.
Numerical Algorithms - An inverse central ordering of the nodes is proposed for the Newton interpolation formula. This ordering may improve the stability for certain distributions of nodes. For... 相似文献
3.
Garcia-Vicua Daniel Esparza Laida Mallor Fermin 《Central European Journal of Operations Research》2022,30(1):213-249
Central European Journal of Operations Research - This paper presents a discrete event simulation model to support decision-making for the short-term planning of hospital resource needs, especially... 相似文献
4.
Dariusz Marek Adam Domaski Joanna Domaska Jakub Szygua Tadeusz Czachrski Jerzy Klamka 《Entropy (Basel, Switzerland)》2021,23(5)
In this article, a way to employ the diffusion approximation to model interplay between TCP and UDP flows is presented. In order to control traffic congestion, an environment of IP routers applying AQM (Active Queue Management) algorithms has been introduced. Furthermore, the impact of the fractional controller ath xmlns:mml="http://www.w3.org/1998/Math/MathML" id="mm1">P I γ ath> and its parameters on the transport protocols is investigated. The controller has been elaborated in accordance with the control theory. The TCP and UDP flows are transmitted simultaneously and are mutually independent. Only the TCP is controlled by the AQM algorithm. Our diffusion model allows a single TCP or UDP flow to start or end at any time, which distinguishes it from those previously described in the literature. 相似文献
5.
Redondo Mara Julia Romn Lucrecia Rossi Bertone Fiorela Verdecchia Melina 《Algebras and Representation Theory》2022,25(4):1037-1059
Algebras and Representation Theory - Let A and B be two Morita equivalent finite dimensional associative algebras over a field ��. It is well known that Hochschild cohomology is... 相似文献
6.
Dr. Silvia Castro-Fernández Carlos M. Cruz Dr. Inês F. A. Mariz Dr. Irene R. Márquez Vicente G. Jiménez Lucía Palomino-Ruiz Prof. Juan M. Cuerva Dr. Ermelinda Maçôas Dr. Araceli G. Campaña 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(18):7205-7211
A new family of distorted ribbon-shaped nanographenes was designed, synthesized, and their optical and electrochemical properties were evaluated, pointing out an unprecedented correlation between their structural characteristics and the two-photon absorption (TPA) responses and electrochemical band gaps. Three nanographene ribbons have been prepared: a seven-membered-ring-containing nanographene presenting a tropone moiety at the edge, its full-carbon analogue, and a purely hexagonal one. We have found that the TPA cross-sections and the electrochemical band gaps of the seven-membered-ring-containing compounds are higher and lower, respectively, than those of the fully hexagonal polycyclic aromatic hydrocarbon (PAH). Interestingly, the inclusion of additional curvature has a positive effect in terms of non-linear optical properties of those ribbons. 相似文献
7.
Yorioka introduced a class of ideals (parametrized by reals) on the Cantor space to prove that the relation between the size of the continuum and the cofinality of the strong measure zero ideal on the real line cannot be decided in alt="urn:x-wiley:09425616:media:malq201800034:malq201800034-math-0001" class="section_image" src="/cms/asset/352a4309-20cb-452b-b495-22960b69bbcd/malq201800034-math-0001.png">. We construct a matrix iteration of c.c.c. posets to force that, for many ideals in that class, their associated cardinal invariants (i.e., additivity, covering, uniformity and cofinality) are pairwise different. In addition, we show that, consistently, the additivity and cofinality of Yorioka ideals does not coincide with the additivity and cofinality (respectively) of the ideal of Lebesgue measure zero subsets of the real line. 相似文献
8.
Ariel Carreño-Montero Luis A. Maldonado María Isabel Chávez Simón Hernández-Ortega Guillermo Delgado 《Tetrahedron letters》2019,60(48):151282
The synthesis of ethyl (2′-hydroxy-4′,5′-methylendioxophenyl)acetate, a fragment of the antihyperglycemic natural coumarin subcoriacin, is reported. We found an expeditious route to the title compound in five steps. Final metal catalyzed acid ethanolysis of the vinylic 1,1-methylthio methylsulfoxide derivative afforded the required aryl acetic ester, but in the absence of metal catalyst, an unexpected Pummerer rearrangement produced the 2,3-dimethylthiofuran derivative as the major product. This last result provides an alternative entry to 2,3-dimethlythiobenzofurans. 相似文献
9.
Reversible Activation of Water by an Air- and Moisture-Stable Frustrated Rhodium Nitrogen Lewis Pair
Dr. María Carmona Dr. Joaquina Ferrer Dr. Ricardo Rodríguez Dr. Vincenzo Passarelli Prof. Dr. Fernando J. Lahoz Dr. Pilar García-Orduña Dr. Laura Cañadillas-Delgado Prof. Dr. Daniel Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(60):13665-13670
[Cp*Rh(κ3N,N′,P- L )][SbF6] (Cp*=C5Me5), bearing a guanidine-derived phosphano ligand L , behaves as a “dormant” frustrated Lewis pair and activates H2 and H2O in a reversible manner. When D2O is employed, a facile H/D exchange at the Cp* ring takes place through sequential C(sp3)−H bond activation. 相似文献
10.
Joseph Aswathy Fal Jacek Żyła Gaweł Mathew Suresh 《Journal of Thermal Analysis and Calorimetry》2019,135(2):1373-1380
Journal of Thermal Analysis and Calorimetry - Understanding the behavior of ionic liquids (ILs) in ionic liquid-based nanofluids has great significance for its proper application. The phase changes... 相似文献