全文获取类型
收费全文 | 583037篇 |
免费 | 4938篇 |
国内免费 | 1466篇 |
专业分类
化学 | 299349篇 |
晶体学 | 8306篇 |
力学 | 28401篇 |
综合类 | 19篇 |
数学 | 76329篇 |
物理学 | 177037篇 |
出版年
2021年 | 5525篇 |
2020年 | 6038篇 |
2019年 | 6821篇 |
2018年 | 9074篇 |
2017年 | 9228篇 |
2016年 | 12740篇 |
2015年 | 6903篇 |
2014年 | 11527篇 |
2013年 | 25843篇 |
2012年 | 20451篇 |
2011年 | 24238篇 |
2010年 | 18032篇 |
2009年 | 17866篇 |
2008年 | 22799篇 |
2007年 | 22678篇 |
2006年 | 20718篇 |
2005年 | 18552篇 |
2004年 | 17212篇 |
2003年 | 15532篇 |
2002年 | 15430篇 |
2001年 | 16045篇 |
2000年 | 12411篇 |
1999年 | 9624篇 |
1998年 | 8432篇 |
1997年 | 8239篇 |
1996年 | 7685篇 |
1995年 | 6910篇 |
1994年 | 6874篇 |
1993年 | 6711篇 |
1992年 | 7054篇 |
1991年 | 7489篇 |
1990年 | 7165篇 |
1989年 | 7088篇 |
1988年 | 6827篇 |
1987年 | 6647篇 |
1986年 | 6377篇 |
1985年 | 8021篇 |
1984年 | 8533篇 |
1983年 | 7129篇 |
1982年 | 7463篇 |
1981年 | 6950篇 |
1980年 | 6578篇 |
1979年 | 7094篇 |
1978年 | 7442篇 |
1977年 | 7284篇 |
1976年 | 7202篇 |
1975年 | 6870篇 |
1974年 | 6745篇 |
1973年 | 6995篇 |
1972年 | 5104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
The modifying action of chloroform on photochemical reactions induced in the eye lenses of rats by UVB radiation is revealed. In anesthetic concentrations, halogenmethane increases the quantum yield of photodisintegration of protein tryptophanyls with formation of a new photochemical product that absorbs radiation in the UVA range and possesses the photosensitizing activity. 相似文献
932.
V. G. Domelunksen I. R. Krylov G. A. Polyanskaya M. A. Tsygankov 《Optics and Spectroscopy》2004,97(1):136-140
An interference method for measuring certain parameters of a substance in the vicinity of the critical state is proposed. The essence of the method is to decipher the interference pattern arising upon grazing incidence of a laser beam on a curved liquid-vapor interface. The deciphering allows one to determine the difference between the refractive indices of the two phases and the scaling factor of the wetting meniscus shape. This, in turn, makes it possible to calculate the critical exponents for the temperature dependences of the surface tension and the difference in the densities of the two phases. The ratio of these critical exponents for xenon, measured in the paper, is 3.81±0.03. 相似文献
933.
A. M. Povolotsky V. B. Priezzhev Chin-Kun Hu 《Journal of statistical physics》2003,111(5-6):1149-1182
An asymmetric stochastic process describing the avalanche dynamics on a ring is proposed. A general kinetic equation which incorporates the exclusion and avalanche processes is considered. The Bethe ansatz method is used to calculate the generating function for the total distance covered by all particles. It gives the average velocity of particles which exhibits a phase transition from an intermittent to continuous flow. We calculated also higher cumulants and the large deviation function for the particle flow. The latter has the universal form obtained earlier for the asymmetric exclusion process and conjectured to be common for all models of the Kardar–Parisi–Zhang universality class. 相似文献
934.
Harper equations are derived for a px, py electronic system. Analysis is carried out for extreme points of the quasi-continuous spectrum in the cases when the number of magnetic flux quanta through a unit cell is a rational number and calculations are made for square and triangular lattices as well as for a honeycomb lattice with two nonequivalent atoms. The possibility of application of the results for explaining the fractional Hall effect is considered. 相似文献
935.
O. I. Reinov 《Journal of Mathematical Sciences》2003,115(2):2243-2250
We investigate Banach spaces possessing (or not possessing) the approximation properties AP s, 0 < s ≤ 1, in connection with the following known question in the geometric theory of operators: under which conditions on Banach spaces X and Y and on positive numbers r and p does the p-nuclearity of the second adjoint of a continuous operator T from X to Y imply the p-nuclearity of T? Actually, we give necessary and sufficient conditions under which this question is answered affirmatively. In addition, the corresponding counterexamples are obtained in the maximally strong form. For instance, it is shown (and this statement is a significant strengthening of the previous results of that sort) that there exists a pair of separable Banach spaces Z and W such that the spaces Z ** and W have Schauder bases, while for every p, 1 ≤ p < 2, there is a non-p-nuclear operator from W to Z with a p-nuclear second adjoint. Earlier, in similar examples, the corresponding spaces did not possess even the Grothendieck approximation property. The technique developed in this paper does not allow us to treat the case p > 2. That case will be studied in a forthcoming paper of the author. Bibliography: 11 titles. 相似文献
936.
For an arbitrary finite time interval, the unique solvability of a linear half-space problem is obtained in Hölder classes of functions. The problem arises as the result of the linearization of a free boundary problem for the Navier--Stokes system governing the unsteady motion of a finite mass of a compressible fluid. The boundary conditions in the linear problem are noncoercive because of the surface tension acting on the free boundary. This fact presents the main difficulty in the problem, while the differential system in itself is parabolic in the sense of Petrovskii. The principal idea of the investigation is to reduce the noncoercive problem to a coercive one with zero coefficient of the surface tension. Bibliography: 6 titles. 相似文献
937.
O. Wibbelhoff C. Meier A. Lorke P. Schafmeister A. D. Wieck 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):516
We use frequency-dependent capacitance–voltage spectroscopy to study the dynamic charging of self-assembled InAs quantum dots. With increasing frequency, the AC charging becomes suppressed, beginning with the low-energy states. By applying an in-plane magnetic field, we generate an additional magnetic confinement that alters the tunneling barrier and hence the charging dynamics. In traveling through the potential barrier, the electrons acquire an additional momentum k0, proportional to the magnetic field B. As the tunneling is enhanced, when k0 matches the maximum of the electronic wave function Ψ (in momentum representation), we are able to map out the shape of Ψ by varying B. 相似文献
938.
939.
O. Naumenko 《Journal of Molecular Spectroscopy》2003,221(2):221-226
The very weak water vapor absorption spectrum has been investigated between 9520 and 10 010 cm−1 by intracavity laser absorption spectroscopy based on a vertical external cavity surface emitting laser. The rovibrational assignment performed on the basis of the ab initio calculations of Schwenke and Partridge has allowed for determining 156 new energy levels belonging to a total of 13 vibrational states. The assignment process is detailed. The results are compared with the available databases and discussed in regard of recent investigations by Fourier transform spectroscopy. 相似文献
940.
J. Wang J. Kono A. Oiwa H. Munekata C. J. Stanton 《Superlattices and Microstructures》2003,34(3-6):563
We have carried out an ultrafast time-resolved differential reflectivity study of a ferromagnetic semiconductor InGaMnAs and made a systematic comparison with low-temperature grown and high-temperature grown InGaAs reference films. Very short carrier lifetimes (2 ps) were observed in InGaMnAs and the low-temperature grown InGaAs film, but not in the high-temperature grown InGaAs film. We attribute the short lifetimes to carrier trapping by mid-gap states introduced during low-temperature MBE growth. Furthermore, at long times, we observed periodic oscillations in the differential reflectivity signal with period 20 ps, which we interpret as coherent acoustic phonons. 相似文献