全文获取类型
收费全文 | 215217篇 |
免费 | 2670篇 |
国内免费 | 816篇 |
专业分类
化学 | 118877篇 |
晶体学 | 3743篇 |
力学 | 8384篇 |
综合类 | 41篇 |
数学 | 21020篇 |
物理学 | 66638篇 |
出版年
2020年 | 1887篇 |
2019年 | 2082篇 |
2018年 | 2390篇 |
2017年 | 2490篇 |
2016年 | 3822篇 |
2015年 | 2472篇 |
2014年 | 3891篇 |
2013年 | 9803篇 |
2012年 | 7088篇 |
2011年 | 8680篇 |
2010年 | 6176篇 |
2009年 | 6107篇 |
2008年 | 7760篇 |
2007年 | 7706篇 |
2006年 | 7212篇 |
2005年 | 6584篇 |
2004年 | 6052篇 |
2003年 | 5633篇 |
2002年 | 5440篇 |
2001年 | 6541篇 |
2000年 | 4991篇 |
1999年 | 3810篇 |
1998年 | 2954篇 |
1997年 | 2891篇 |
1996年 | 2802篇 |
1995年 | 2654篇 |
1994年 | 2543篇 |
1993年 | 2334篇 |
1992年 | 2977篇 |
1991年 | 2888篇 |
1990年 | 2839篇 |
1989年 | 2830篇 |
1988年 | 2837篇 |
1987年 | 2846篇 |
1986年 | 2706篇 |
1985年 | 3503篇 |
1984年 | 3530篇 |
1983年 | 2743篇 |
1982年 | 2873篇 |
1981年 | 2901篇 |
1980年 | 2675篇 |
1979年 | 3006篇 |
1978年 | 2965篇 |
1977年 | 3131篇 |
1976年 | 2946篇 |
1975年 | 2667篇 |
1974年 | 2614篇 |
1973年 | 2572篇 |
1972年 | 1763篇 |
1968年 | 1730篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
231.
S. I. Anisimov V. V. Zhakhovskii N. A. Inogamov K. Nishihara A. M. Oparin Yu. V. Petrov 《JETP Letters》2003,77(11):606-610
Molecular-dynamics (MD) simulation of the destruction of a crystal film heated by a femtosecond laser pulse was carried out. Heating is assumed to be instantaneous, because there is no time for the material to be displaced during the pulse. Film destruction is caused by the interaction of unloading waves. It can be considered as a model of a more complex process of splitting out of a thin surface layer from a massive target in the case where the layer remains solid after heating. It was found that the crystal order is broken due to the stretching strains and to the strong anisotropy of residual stress, resulting in a bipartition of the layer separating from the target. The lattice stretching and the formation of anisotropic stresses are due to the expansion of a heated lattice. 相似文献
232.
233.
M. Stangl V. Dittel J. Acker V. Hoffmann W. Gruner S. Strehle K. Wetzig 《Applied Surface Science》2005,252(1):158-161
At room temperature electroplated copper layers exhibit changes in resistivity, residual stress, and microstructure. This process, known as self-annealing, is intimately linked to the release of organic impurities, which stem from the incorporation of organic additives into the Cu layer in the course of the electroplating process. The behavior of these impurities during self-annealing, represented by the carbon content, could be detected by analytical radio frequency glow discharge optical emission spectrometry (GD-OES) and carrier gas hot extraction (CGHE). The precondition of a quantitative determination is a surface cleaning procedure to remove adsorbed organics from the copper surface. It was observed that at first almost all impurities have to leave the Cu metallization before an accelerated abnormal grain growth can start. The small amount of remaining organic species after self-annealing could be quantified by both examination techniques, GD-OES and CGHE. 相似文献
234.
235.
I. M. Kolthoff S. R. Cooper V. J. Tulane F. Reimers H. A. J. Pieters K. Höppner V. H. Matula C. B. Macek W. N. Skworzow J. S. Schepelewa F. Čuta K. Kámen S. Cohen R. E. Oesper D. S. Narayanamurthi T. R. Seshadri H. M. State A. W. Kirssanow W. M. Tscherkassow D. M. Mukherjee T. Akiyama Y. Mine S. Yabe Y. Volmar M. Déribéré 《Analytical and bioanalytical chemistry》1937,111(5-6):192-197
236.
K. Vierordt 《Fresenius' Journal of Analytical Chemistry》1872,11(1):429
Ohne Zusammenfassung 相似文献
237.
238.
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
239.
The rate constants k1 for the reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals were determined by using both absolute and relative rate methods. The absolute rate constants were measured at 250–430 K using the flash photolysis–laser‐induced fluorescence (FP‐LIF) technique and the laser photolysis–laser‐induced fluorescence (LP‐LIF) technique to monitor the OH radical concentration. The relative rate constants were measured at 253–328 K in an 11.5‐dm3 reaction chamber with either CHF2Cl or CH2FCF3 as a reference compound. OH radicals were produced by UV photolysis of an O3–H2O–He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during the UV irradiation. The k1 (298 K) values determined by the absolute method were (1.69 ± 0.07) × 10?15 cm3 molecule?1 s?1 (FP‐LIF method) and (1.72 ± 0.07) × 10?15 cm3 molecule?1 s?1 (LP‐LIF method), whereas the K1 (298 K) values determined by the relative method were (1.87 ± 0.11) × 10?15 cm3 molecule?1 s?1 (CHF2Cl reference) and (2.12 ± 0.11) × 10?15 cm3 molecule?1 s?1 (CH2FCF3 reference). These data are in agreement with each other within the estimated experimental uncertainties. The Arrhenius rate constant determined from the kinetic data was K1 = (4.71 ± 0.94) × 10?13 exp[?(1630 ± 80)/T] cm3 molecule?1 s?1. Using kinetic data for the reaction of tropospheric CH3CCl3 with OH radicals [k1 (272 K) = 6.0 × 10?15 cm3 molecule?1 s?1, tropospheric lifetime of CH3CCl3 = 6.0 years], we estimated the tropospheric lifetime of CF3CF2CF2CF2CF2CHF2 through reaction with OH radicals to be 31 years. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 26–33, 2004 相似文献
240.
A homologous series of azomesogens, 2″-[4-(4′-n-alkoxybenzoyloxy)-2-chlorophenylazo] naphthalenes, with lateral chloro groups was synthesised. All the homologues synthesized
exhibit enantiotropic nematic mesophase. The mesomorphic properties of the present series are compared with other structurally
related series to evaluate the effect of lateral chloro group and its position on mesomorphism
This paper was presented at the 10th National Conference on Liquid Crystals held at Bangalore, India during 9–11 October 2003. 相似文献