全文获取类型
收费全文 | 866篇 |
免费 | 16篇 |
国内免费 | 15篇 |
专业分类
化学 | 393篇 |
晶体学 | 5篇 |
力学 | 19篇 |
数学 | 344篇 |
物理学 | 136篇 |
出版年
2023年 | 8篇 |
2022年 | 20篇 |
2021年 | 25篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 17篇 |
2017年 | 19篇 |
2016年 | 21篇 |
2015年 | 24篇 |
2014年 | 26篇 |
2013年 | 64篇 |
2012年 | 47篇 |
2011年 | 45篇 |
2010年 | 42篇 |
2009年 | 49篇 |
2008年 | 48篇 |
2007年 | 61篇 |
2006年 | 47篇 |
2005年 | 44篇 |
2004年 | 27篇 |
2003年 | 33篇 |
2002年 | 27篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1989年 | 4篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1961年 | 3篇 |
1939年 | 2篇 |
1938年 | 2篇 |
1936年 | 4篇 |
1932年 | 2篇 |
排序方式: 共有897条查询结果,搜索用时 31 毫秒
41.
Mihai Răducă Cristian D. Ene Sorana Ionescu Mihaela Florea 《Journal of Coordination Chemistry》2019,72(8):1222-1237
Abstract1-D coordination polymers, 1∞[Zn(fl)2]·2EtOH and 1∞[Zn(fl)2]·2MeOH, and a dinuclear complex, [{Zn(fl)2}2(dienpip)]·4H2O·4EtOH (dienpip?= N,N′-bis(2-aminoethyl)piperazine), were obtained using Zn(II) ions and fluorescein anions (fl). Thermal analysis shows stability of the polymers after solvent removal up to more than 400?°C. Crystallization solvent molecules were removed under reduced pressure with the preservation of the polymeric structure, 1∞[Zn(fl)2]. Desolvated crystals were exposed to I2 vapors and the crystal structure determination by X-ray diffraction confirmed the presence of I2 molecules in the channels generated in crystals by the metal-organic framework. The iodine content, evaluated by X-ray diffraction, corresponds to the overall formula 1∞[Zn(fl)2]·0.3I2. The optical properties of the coordination polymers and the dinuclear complex have been investigated. 相似文献
42.
In this paper we prove large-data local stability theorems for several spin-field models in two dimensions, both in the focusing
case (spherical target) and the defocusing case (hyperbolic target). 相似文献
43.
Ciprian Dragan Adrian Samuila Subhankar Das Dan Iancu Mihai Bilici Lucian Dascalescu 《Journal of Electrostatics》2009,67(2-3):184-188
The aim of this study is to refine the understanding of the tribo-electrostatic phenomena that can affect the efficiency of suction-type dilute-phase transport systems. The study was conducted with mm-size ABS-PC particles, a granular material originating from genuine information technology wastes. The tribo-charging process was modelled using the response surface method of experimental design. The controlled variables were the granular material feed rate and the aspirating air speed rate. The monitored variable was the charge imparted to a well-defined section of the duct and which is equal to the charge transferred to the particles passing through that section of the pneumatic transport system. An induction type sensor connected to an electrometer has been employed for the measurements. The data were processed by a virtual instrument developed in LabView. A commercial software package was employed for estimating the effects of the various factors and predicting the optimum operating conditions, which were then confirmed by a final experiment. 相似文献
44.
45.
Mihai Mari 《Journal de Mathématiques Pures et Appliquées》2002,81(12):109-1239
We are interested in the existence of travelling-waves for the nonlinear Schrödinger equation in RN with “ψ3−ψ5”-type nonlinearity. First, we prove an abstract result in critical point theory (a local variant of the classical saddle-point theorem). Using this result, we get the existence of travelling-waves moving with sufficiently small velocity in space dimension N4. 相似文献
46.
Lucian M. Ionescu 《Applied Categorical Structures》2002,10(1):35-47
We review several known categorification procedures, and introduce a functorial categorification of group extensions (Section 4.1) with applications to non-Abelian group cohomology (Section 4.2). The obstruction to the existence of group extensions (Section 4.2.4, Equation (9)) is interpreted as a coboundary condition (Proposition 4.5). 相似文献
47.
Vlad Ionescu 《Integral Equations and Operator Theory》1999,34(1):45-55
Based on the Ben Artzi-Gohberg result concerning the equivalence between the invertibility of theL
2-operator
and the exponential dichotomic evolution defined byA(t), the time-varying counterpart of the Redheffer theorem is considered under relaxed conditions. 相似文献
48.
M. Petrascu A. Isbasescu I. Lazar I. Mihai H. Petrascu A. T. Rudchik V. A. Chernievski O. A. Ponkratenko V. A. Ziman 《Zeitschrift für Physik A Hadrons and Nuclei》1993,345(4):395-399
The energy spectra and angular distributions of products in the reaction27Al(14N,X) have been measured at 116 MeV bombarding energy. It is shown that the energy spectra of the products lighter than the projectile, are well described by a three-body breakup calculation. The experimental total breakup cross-section estimated in the present work, together with Glas-Mosel calculation of the fusion cross-section, are in a reasonable agreement with the optical model total reaction cross-section. 相似文献
49.
A new cell is described which allows simultaneous measurement of the electrical and catalytic properties of a promoted Bi–Mo catalyst. The electrical resistance data show that the interaction of propylene with the catalyst starts at 310 °C.
, Bi–Mo. , 310°C.相似文献
50.