全文获取类型
收费全文 | 4145篇 |
免费 | 87篇 |
国内免费 | 22篇 |
专业分类
化学 | 2714篇 |
晶体学 | 25篇 |
力学 | 161篇 |
数学 | 651篇 |
物理学 | 703篇 |
出版年
2021年 | 27篇 |
2020年 | 31篇 |
2019年 | 33篇 |
2018年 | 39篇 |
2017年 | 38篇 |
2016年 | 61篇 |
2015年 | 73篇 |
2014年 | 86篇 |
2013年 | 229篇 |
2012年 | 170篇 |
2011年 | 199篇 |
2010年 | 124篇 |
2009年 | 116篇 |
2008年 | 171篇 |
2007年 | 165篇 |
2006年 | 177篇 |
2005年 | 197篇 |
2004年 | 158篇 |
2003年 | 146篇 |
2002年 | 157篇 |
2001年 | 61篇 |
2000年 | 70篇 |
1999年 | 65篇 |
1998年 | 47篇 |
1997年 | 73篇 |
1996年 | 75篇 |
1995年 | 65篇 |
1994年 | 55篇 |
1993年 | 60篇 |
1992年 | 51篇 |
1991年 | 54篇 |
1990年 | 39篇 |
1989年 | 44篇 |
1988年 | 35篇 |
1987年 | 32篇 |
1985年 | 79篇 |
1984年 | 62篇 |
1983年 | 50篇 |
1982年 | 65篇 |
1981年 | 72篇 |
1980年 | 54篇 |
1979年 | 71篇 |
1978年 | 68篇 |
1977年 | 78篇 |
1976年 | 52篇 |
1975年 | 54篇 |
1974年 | 50篇 |
1973年 | 38篇 |
1971年 | 36篇 |
1968年 | 27篇 |
排序方式: 共有4254条查询结果,搜索用时 31 毫秒
21.
Perdigón-Melón J. A. Auroux A. Bonnetot B. 《Journal of Thermal Analysis and Calorimetry》2003,72(2):443-451
As supported palladium oxide catalysts present the best performances in methane combustion in lean conditions, microcalorimetric
studies of the interaction between methane and palladium oxide or metallic palladium supported on Al2O3, ZrO2 and BN have been performed at 673 K. At this temperature methane reduced the palladium oxide, and the heat of reduction of
palladium oxide was shown to depend on the dispersion and on the support. The lowest heats of reduction corresponded to the
highest rates of methane combustion. Moreover methane reforming occurred on metallic palladium, producing hydrogen, and again
methane decomposition was shown to depend on the support.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
22.
Patrick Pruja Sauveur Bnet Bernard Claudet Olivier Faugeroux Jean-Jacques Serra 《Superlattices and Microstructures》2004,35(3-6):409
Modeling the behavior of a protective coating during a thermal shock not only requires the knowledge of its own thermophysical characteristics, but also those of the coating–substrate discontinuity. According to its nature, this discontinuity can be modeled as a zero-thickness interface (thermal contact resistance) or a finite thickness layer (thermal third body). This paper presents an experimental device and two associated thermal transfer models developed in view of the microscale characterization of such discontinuities. 相似文献
23.
A perturbation wave solution of the Robinson-Trautman equations is proved to be a perturbation of the Schwarzschild black hole which describes an outgoing axial gravitational wave and corresponds to a special case of Chandrasekhar's algebraically special perturbation of the Schwarzschild metric. 相似文献
24.
25.
26.
The purpose of this paper is to analyze the convergence of interval-type algorithms for solving the generalized fractional program. They are characterized by an interval [LB
k
, UB
k
] including*, and the length of the interval is reduced at each iteration. A closer analysis of the bounds LB
k
and UB
k
allows to modify slightly the best known interval-type algorithm NEWMODM accordingly to prove its convergence and derive convergence rates similar to those for a Dinkelbach-type algorithm MAXMODM under the same conditions. Numerical results in the linear case indicate that the modifications to get convergence results are not obtained at the expense of the numerical efficiency since the modified version BFII is as efficient as NEWMODM and more efficient than MAXMODM.This research was supported by NSERC (Grant A8312) and FCAR (Grant 0899). 相似文献
27.
Edward R. T. Tiekink Tomas Kurucsev Bernard F. Hoskins 《Journal of chemical crystallography》1989,19(5):823-839
The preparation, characterization, and X-ray structure analysis of (adeninatoN9)triethylphosphinegold(I) is reported. The crystal structure consists of discrete molecules, the adeninate anion coordinates via the N(9) atom with a Au-N(9) bond distance of 2.057(5) Å and the linear geometry about the Au atom is completed by the P atom of a disordered Et3P ligand; the Au-P(1) bond distance is 2.238(2) Å and the N(9)-Au-P(1) bond angle is 178.8(2)°. The crystals are orthorhombic, space groupPbca, with unit cell dimensionsa=8.528(1),b=17.797(3),c=18.526(2) Å andZ=8. The structure was refined by a full-matrix least-squares procedure to finalR=0.030 andR
w
=0.033 for 1749 reflections withI>2.5a(I). The electronic spectrum of the complex dissolved in water in the near ultraviolet is consistent with essentially separate -electron systems of the adenine and phosphinegold moieties; a conclusion which corroborates the X-ray structural results. 相似文献
28.
29.
The first reported synthesis of 3-formyltetronic acid and its conversion to enamine derivatives is described. 3-Dimethylaminomethylene-2,4-dioxotetrahydrofuran derivatives were also prepared by treatment of tetronic acids with dimethylformamide diethyl acetal. Nmr spectral studies are included. 相似文献
30.