全文获取类型
收费全文 | 616308篇 |
免费 | 4701篇 |
国内免费 | 1523篇 |
专业分类
化学 | 309080篇 |
晶体学 | 8790篇 |
力学 | 31866篇 |
综合类 | 35篇 |
数学 | 83409篇 |
物理学 | 189352篇 |
出版年
2021年 | 5746篇 |
2020年 | 6196篇 |
2019年 | 7075篇 |
2018年 | 9676篇 |
2017年 | 9850篇 |
2016年 | 13402篇 |
2015年 | 7170篇 |
2014年 | 12063篇 |
2013年 | 27053篇 |
2012年 | 21063篇 |
2011年 | 25023篇 |
2010年 | 19073篇 |
2009年 | 19048篇 |
2008年 | 23769篇 |
2007年 | 23517篇 |
2006年 | 21356篇 |
2005年 | 19012篇 |
2004年 | 17761篇 |
2003年 | 15985篇 |
2002年 | 15949篇 |
2001年 | 17172篇 |
2000年 | 13267篇 |
1999年 | 10228篇 |
1998年 | 8952篇 |
1997年 | 8770篇 |
1996年 | 8090篇 |
1995年 | 7310篇 |
1994年 | 7261篇 |
1993年 | 7058篇 |
1992年 | 7442篇 |
1991年 | 8041篇 |
1990年 | 7667篇 |
1989年 | 7629篇 |
1988年 | 7397篇 |
1987年 | 7213篇 |
1986年 | 6893篇 |
1985年 | 8801篇 |
1984年 | 9113篇 |
1983年 | 7719篇 |
1982年 | 8003篇 |
1981年 | 7513篇 |
1980年 | 7077篇 |
1979年 | 7736篇 |
1978年 | 8049篇 |
1977年 | 7975篇 |
1976年 | 7959篇 |
1975年 | 7639篇 |
1974年 | 7430篇 |
1973年 | 7787篇 |
1972年 | 5808篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
G. Baldsiefen H. Hübel W. Korten U. J. van Severen J. A. Cizewski N. H. Medina D. R. Napoli C. Rossi Alvarez G. Lo Bianco S. Signorelli 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):337-338
High-spin states in196Pb have been populated using the reaction170Er(30Si,4n). The previously observed shears bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin. 相似文献
992.
V. I. Pogorelov 《Radiophysics and Quantum Electronics》1995,38(7):417-422
A general expression describing the coherent scattering indicatrix by arbitrary inhomogeneities of the medium is derived. It is shown that a universal program can be devised for calculation of such indicatrices to avoid difficulties in the analytical and experimental investigations of the media through the wave processes.Institute of Applied Geophysics, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 631–638, July, 1995. 相似文献
993.
994.
P. G. Baranov N. G. Romanov A. Hofstaetter A. Scharmann C. Schnorr F. J. Ahlers K. Pierz 《JETP Letters》1996,64(10):754-759
Two types of excitons, localized at opposite interfaces and characterized by different magnitudes of the exchange interactions
at the same radiation energies, are simultaneously in type-II GaAs/AlAs superlattices. It is shown that the additional long-wavelength
luminescence line in superlattices grown with growth interruptions after the GaAs layers is due to the recombination of an
exciton localized at an inverted interface in regions where the quantum-well width is increased by one monolayer.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 701–706 (25 November 1996) 相似文献
995.
A generalized Gibbs-ensemble methodology with a fluctuating particle is used to determine the coexistence vapor-liquid densities for a square-well fluid. It is shown that the presence of the fluctuating particle in sub-states of the Markov chain of states supresses considerably density fluctuations which makes it possible to carry out simulations efficiently even for temperatures very close to the critical temperature. 相似文献
996.
The behaviour of La-containing strontium zirconate based ceramics is revised. La additions contribute to improve the sinterability
of these materials, but transport properties are also affected. Sr1−xLaxZrO3+δ show some unusual changes in transport properties when samples are exposed to H2-containing atmospheres and then reoxidized. Nevertheless, the transport properties of (Sr,La)(Zr,Y)O3−δ, are still mainly dependent on Y additions, at least for cases when the fraction of Y exceeds the fraction of La. In addition,
lanthanum causes significant changes in lattice parameters. A combination of conductivity measurements in different atmospheres,
ion blocking experiments, and emf measurements has been used to demonstrate that electron hole conductivity increases with
temperature, and the protonic contribution drops. The transport properties at temperatures lower than about 800 °C might be
affected by structural changes.
Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995 相似文献
997.
A. Gerasimov 《Journal of statistical physics》1993,70(3-4):939-948
The analysis is carried out of the response of the center of gravity (dipole moment) of the distribution of noninteracting thermalized nonlinear oscillators to a sinusoidal driving force. Heat bath coupling is modeled by damping and noise. The driving is weak, but the frequency is resonant, so that there is a nonlinear resonance in the phase space. The response has a linear part that can be obtained from the perturbation analysis and a small nonlinear correction that is specific for the resonant structure. 相似文献
998.
This Review discusses the synthesis and characterization by our Group of new antibiotics belonging to the class of penicillins, cephalosporins and rifamycins with ferrocenyl and 1, 1′-ferrocenilene residues in the molecule. As reactants for 6-aminopenicillanic acid (6-APA) and 7-aminocephalosporanic acid (7-ACA) the following were used: 1, 1-bis(chlorocarbonyl)ferrocene, ferrocenyl sulfochloride, 1, 1′-ferrocenylenedisulfochloride and thioglycolic acids S-modified with ferrocene. In the synthesis of rifamycins, the hydrazides of the thioglycolic acids, S-modified with ferrocene, were employed as nucleophilic agents. The synthesized intermediates were characterized by elemental analysis, TLC, IR, UV and 1H NMR spectra. The characterization of new antibiotics was made by TLC, IR and UV spectral analysis. Biological activity was tested on Gram-negative and Gram-positive bacteria. Good activity is reported towards Gram-positive bacteria in the case of derivatives containing residues of thioglycolic acid S-modified with ferrocene, the antibacterial activity being similar to that of amoxicillin, carbenicillin and cephalothin. All compounds are inactive towards Gram-negative bacteria. 相似文献
999.
A quasipotential operator for a system of two scalar particles, and also an integral equation and a normalization condition for the wave function of the connected state, are obtained by the method of two-time Green's functions in an explicitly covariant form. The cases are considered of scalar and electromagnetic interactions of particles of the system.Frantsiska Skoriny Gomel' State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 112–118, June, 1993. 相似文献
1000.
The gravitational interaction between grooves machined in a hollow cylindrical mass of uniform density, and an external point mass, is derived in terms of the Associated Legendre functions, and the parametric form of the coupling coefficients is presented. The cross-sections of the grooves, which are regularly spaced in azimuth, are in the form of truncated sectors of the cylinder's end-faces. This theory is applied to the test-masses for the Satellite Test of the Equivalence Principle (STEP) experiment, for which four grooves have been assumed, and an expression for the axialforce is derived which is more than 104 times faster to compute than a Monte-Carlo integration of similar accuracy. Following this analysis it is suggested that the STEP test-masses should carry at least 6 grooves. This theory has wider application to gravitational problems involving general sectored cylindrical bodies. 相似文献