全文获取类型
收费全文 | 10424篇 |
免费 | 364篇 |
国内免费 | 88篇 |
专业分类
化学 | 7135篇 |
晶体学 | 93篇 |
力学 | 267篇 |
综合类 | 1篇 |
数学 | 1740篇 |
物理学 | 1640篇 |
出版年
2023年 | 81篇 |
2022年 | 121篇 |
2021年 | 193篇 |
2020年 | 210篇 |
2019年 | 250篇 |
2018年 | 158篇 |
2017年 | 159篇 |
2016年 | 384篇 |
2015年 | 288篇 |
2014年 | 320篇 |
2013年 | 603篇 |
2012年 | 607篇 |
2011年 | 653篇 |
2010年 | 453篇 |
2009年 | 404篇 |
2008年 | 586篇 |
2007年 | 630篇 |
2006年 | 494篇 |
2005年 | 547篇 |
2004年 | 440篇 |
2003年 | 350篇 |
2002年 | 336篇 |
2001年 | 162篇 |
2000年 | 144篇 |
1999年 | 96篇 |
1998年 | 103篇 |
1997年 | 109篇 |
1996年 | 113篇 |
1995年 | 93篇 |
1994年 | 84篇 |
1993年 | 100篇 |
1992年 | 78篇 |
1991年 | 79篇 |
1990年 | 74篇 |
1989年 | 64篇 |
1988年 | 51篇 |
1987年 | 55篇 |
1986年 | 69篇 |
1985年 | 103篇 |
1984年 | 101篇 |
1983年 | 79篇 |
1982年 | 69篇 |
1981年 | 72篇 |
1980年 | 68篇 |
1979年 | 64篇 |
1978年 | 68篇 |
1977年 | 41篇 |
1976年 | 40篇 |
1975年 | 50篇 |
1974年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
We investigate traces of functions, belonging to a class of functions with dominating mixed smoothness in ℝ3, with respect to planes in oblique position. In comparison with the classical theory for isotropic spaces a few new phenomenona
occur. We shall present two different approaches. One is based on the use of the Fourier transform and restricted to p = 2. The other one is applicable in the general case of Besov-Lizorkin-Triebel spaces and based on atomic decompositions. 相似文献
32.
The stoichiometric reactions of trimethylaluminum with 2,6‐(MeOCH2)2C6H3OH (LH) revealed compounds L3Al ( 1 ) and L2AlMe ( 2 ). On the other hand reaction of 1 equiv. of LH with trimethylaluminum did not lead to the formation of complex LAlMe2 ( 3 ), rather 2 together with Me3Al were observed as a result of a disproportionation of 3 . Compounds 1 and 2 were characterized by elemental analysis, 1H and 13C NMR spectroscopy and in the case of 1 by X‐ray diffraction. Derivative 2 underwent transmetalation with Ph3SnOH, giving LSnPh3 ( 4 ) as the result of a migration of ligand L from the aluminum to the tin atom. The identity of 4 was established by elemental analysis, 1H, 13C and 119Sn NMR spectroscopy and 1H, 119Sn HMBC experiments. The system 2 and B(C6F5)3 in a 1:1 molar ratio was shown to be active in the polymerization of propylene oxide and ε‐caprolactone. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
33.
Applying a Lindemann like criterion obtained previously by Kierfeld et al. [J. Kierfeld, T. Nattermann, T. Hwa, Phys. Rev. B 55 (1997) 626], we estimate the magnetic field and temperature for a high-Tc superconductor, at which a topologically ordered vortex glass phase becomes unstable with respect to a disorder-induced formation of dislocations. The employed criterion is shown to be equivalent to a conventional phenomenological Lindemann criterion including the values for the numerical factors, i.e., for the Lindemann number. The positional correlation length of the topologically ordered vortex glass is calculated. 相似文献
34.
35.
Jan Novotný 《General Relativity and Gravitation》1987,19(10):1043-1052
Direct calculation proves that the total energy-momentum vector derived from the Møller energy-momentum complex from 1958 does not transform like a free 4-vector with respect to the Lorentz transformation. This conforms with the conclusion formulated by Møller himself, but it contradicts the result of the critical analysis of Kovacs. Defects in Kovacs argumentation are found. 相似文献
36.
37.
Measurement has been made of the dependence of the molecular weight distribution on the ratio of the catalytic system components and on the polymerization time for polycaprolactam obtained by anionic polymerization. A bimodal character of the curves was observed for products made using molar ratios of activator (N-benzoylcaprolactam) to initiator (sodium dihydro-bis(methoxyethoxy)aluminate) of 1:1 and 1:3, when the polymerization times were less than 1 hr. This course is explained by the influence of fast side-reactions, mainly condensations. For a ratio of 3:1 of the components of the catalytic system, smooth integral distribution curves are obtained, accounting for a very fast decrease in the strong base concentration in the initial stages of the polymerization. 相似文献
38.
Horváth-Szabó G Czarnecki J Masliyah JH 《Journal of colloid and interface science》2002,253(2):427-434
Equilibrium liquid crystal (LC) layer on an interface between crude oils and water was observed at high pH. This layer is composed mainly of sodium naphthenates produced in situ at the water/oil interface. Transient LC layer was also evolved at the interface of aqueous phase of sodium hydroxide solutions and oleic phase of naphthenic acid (NA) solutions as result of a chemical reaction between NaOH and NA. This chemical reaction causes transport process resulting in a disturbance of the interface. Optical observation of this interface disturbance reviled that the interface covered with LC shows considerably lower flexibility as compared to LC free interface. The LC layer eventually dissolves in the water phase at low oil-to-water ratio, while at high oil-to-water ratio it can form an equilibrium phase, which spreads spontaneously at the oil-water interface. 相似文献
39.
The sorption of solvent vapours onto dried cellulose has been investigated. The time-dependence and the effect of the solvent-water ratio is discussed. The studies concerned the properties of methanol, ethanol, propanol and butanol. 相似文献
40.
The occurrence and magnitude of secondary kinetic isotope effects in the gas phase has been determined for deuterium abstraction from the CD3 group in CD3CH2Cl, CD3CHDCl, and CD3CD2Cl by photochemically generated ground-state chlorine atoms. Over the temperature range 10–94°C a discernible “inverse” kinetic isotope effect is observed. Both the pre-exponential factors and activation energies decrease with deuterium substitution in the vicinal chloromethyl group. The opposing trends result in a net effect close to unity. 相似文献