全文获取类型
收费全文 | 32785篇 |
免费 | 785篇 |
国内免费 | 167篇 |
专业分类
化学 | 19126篇 |
晶体学 | 194篇 |
力学 | 1038篇 |
综合类 | 9篇 |
数学 | 5067篇 |
物理学 | 8303篇 |
出版年
2023年 | 150篇 |
2022年 | 350篇 |
2021年 | 576篇 |
2020年 | 528篇 |
2019年 | 488篇 |
2018年 | 546篇 |
2017年 | 479篇 |
2016年 | 898篇 |
2015年 | 737篇 |
2014年 | 834篇 |
2013年 | 1416篇 |
2012年 | 1790篇 |
2011年 | 2031篇 |
2010年 | 1170篇 |
2009年 | 1113篇 |
2008年 | 1713篇 |
2007年 | 1667篇 |
2006年 | 1557篇 |
2005年 | 1900篇 |
2004年 | 1869篇 |
2003年 | 1345篇 |
2002年 | 998篇 |
2001年 | 704篇 |
2000年 | 636篇 |
1999年 | 416篇 |
1998年 | 372篇 |
1997年 | 373篇 |
1996年 | 453篇 |
1995年 | 376篇 |
1994年 | 381篇 |
1993年 | 384篇 |
1992年 | 375篇 |
1991年 | 310篇 |
1990年 | 270篇 |
1989年 | 251篇 |
1988年 | 218篇 |
1987年 | 218篇 |
1986年 | 203篇 |
1985年 | 266篇 |
1984年 | 274篇 |
1983年 | 222篇 |
1982年 | 232篇 |
1981年 | 214篇 |
1980年 | 209篇 |
1979年 | 178篇 |
1978年 | 208篇 |
1977年 | 166篇 |
1976年 | 148篇 |
1974年 | 147篇 |
1973年 | 137篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
51.
Robert de Levie 《The Chemical Educator》2002,7(3):132-135
Using contemporary accounts, we describe the scope of the Henderson approximation, and its relationship to the mass action law of Guldberg & Waage. The Henderson approximation, apparently written in logarithmic form by Hasselbalch, has the same form as the mass action law, but has a completely different meaning and a much more restricted range of applicability. The Guldberg-Waage law is the fundamental mass action relationship valid for all chemical equilibria, whereas the Henderson approximation is useful only within a limited range of a sufficiently concentrated two-component buffer mixture. 相似文献
52.
Marcelo Queiroz Joaquim Jú dice Carlos Humes Jr.. 《Mathematics of Computation》2004,73(248):1849-1863
In this paper the Eigenvalue Complementarity Problem (EiCP) with real symmetric matrices is addressed. It is shown that the symmetric (EiCP) is equivalent to finding an equilibrium solution of a differentiable optimization problem in a compact set. A necessary and sufficient condition for solvability is obtained which, when verified, gives a convenient starting point for any gradient-ascent local optimization method to converge to a solution of the (EiCP). It is further shown that similar results apply to the Symmetric Generalized Eigenvalue Complementarity Problem (GEiCP). Computational tests show that these reformulations improve the speed and robustness of the solution methods.
53.
Antonio Uris Jose Maria Bravo Jaime Llinares Hermelando Estelles 《Applied Acoustics》2004,65(4):421-430
In this paper the influence on sound reduction index of the length and the depth of sound leaks at the perimeter of lightweight partitions was examined. It was shown that the most important decrease on sound reduction index is caused by the first slit between lightweight partition and one of the structural members. When the length of the slit is increased, the decrease on sound reduction index is less significative. Calculated results show the same effects as measured ones. 相似文献
54.
A.F. Mesquita A.O. Porto G.M. de Lima J.M. Delgado F.S. Lameiras 《Solid State Communications》2005,136(3):133-137
Hexagonal and cubic cadmium selenide were prepared from a chemical route by using cadmium chloride and potassium selenium hydride obtained from reaction of selenium powder and potassium boron hydride. The product obtained was thermally treated under argon flux at 300, 500 and 600 °C for 2 h and characterized by X-ray photoelectron spectroscopy and X-ray diffraction. The X-ray diffraction data were refined by Rietveld method and the structural parameters were determined for the phases of each annealed samples. At 300 °C five phases were identified: Cubic and hexagonal cadmium selenides and the contaminants: Potassium chloride, boron oxide and cadmium boron oxide. At 500 and 600 °C only the hexagonal cadmium selenide phase was identified besides the other above mentioned contaminant. 相似文献
55.
J.-C. Thomas L. Achouri J. Äystö R. Béraud B. Blank G. Canchel S. Czajkowski P. Dendooven A. Ensallem J. Giovinazzo N. Guillet J. Honkanen A. Jokinen A. Laird M. Lewitowicz C. Longour F. de Oliveira Santos K. Peräjärvi M. Stanoiu 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):419-435
56.
YBa2Cu3O7-x (YBCO) bulk is one of the most important high temperature superconducting materials for magnetic levitation applications, because it has a high magnetic irreversibility field Hirr at liquid nitrogen temperature, and can grow into large grains. The levitation force of YBCO bulk is proportional to the critical current density (Jc) and grain radius (r)[1], so higher Jc and r are appreciated for YBCO bulks to achieve higher levitation force. Now single-domain YBCO bulks up to s… 相似文献
57.
Affine Arithmetic: Concepts and Applications 总被引:2,自引:0,他引:2
Affine arithmetic is a model for self-validated numerical computation that keeps track of first-order correlations between computed and input quantities. We explain the main concepts in affine arithmetic and how it handles the dependency problem in standard interval arithmetic. We also describe some of its applications. 相似文献
58.
Palladium-containing zeolites catalyze the cycloisomerization of diethyl diallylmalonate to dimethylcyclopentenes. When the reaction is carried out in toluene, the performance of the palladium catalyst depends on the pore size of the zeolites. At 60 °C, palladium adsorbed on large pore size Beta zeolite (pore size ∼7.4 Å) is more active than medium pore size ZSM-5 (pore size ∼5.4 Å). This lower activity of ZSM-5 compared to Beta is attributable to the restricted diffusion of reagent and products through the ZSM-5 channels as compared to Beta zeolite. However, due to the gas-like diffusion characteristic of the supercritical state, the activity of ZSM-5 increases and becomes identical to that of Beta zeolite using supercritical CO2 as medium. 相似文献
59.
60.
Antonio Longi 《Fresenius' Journal of Analytical Chemistry》1884,23(1):149-151
Ohne Zusammenfassung 相似文献