全文获取类型
收费全文 | 607965篇 |
免费 | 4359篇 |
国内免费 | 1567篇 |
专业分类
化学 | 277937篇 |
晶体学 | 8953篇 |
力学 | 35197篇 |
综合类 | 10篇 |
数学 | 103656篇 |
物理学 | 188138篇 |
出版年
2021年 | 5079篇 |
2020年 | 5401篇 |
2019年 | 6313篇 |
2018年 | 18736篇 |
2017年 | 18758篇 |
2016年 | 17945篇 |
2015年 | 7221篇 |
2014年 | 11693篇 |
2013年 | 24271篇 |
2012年 | 22482篇 |
2011年 | 32136篇 |
2010年 | 22725篇 |
2009年 | 23446篇 |
2008年 | 27060篇 |
2007年 | 28756篇 |
2006年 | 19100篇 |
2005年 | 17629篇 |
2004年 | 16978篇 |
2003年 | 15875篇 |
2002年 | 15107篇 |
2001年 | 15828篇 |
2000年 | 12164篇 |
1999年 | 9263篇 |
1998年 | 8180篇 |
1997年 | 7835篇 |
1996年 | 7336篇 |
1995年 | 6429篇 |
1994年 | 6366篇 |
1993年 | 6264篇 |
1992年 | 6566篇 |
1991年 | 7106篇 |
1990年 | 6808篇 |
1989年 | 6753篇 |
1988年 | 6376篇 |
1987年 | 6553篇 |
1986年 | 6129篇 |
1985年 | 7435篇 |
1984年 | 7710篇 |
1983年 | 6502篇 |
1982年 | 6677篇 |
1981年 | 6248篇 |
1980年 | 6044篇 |
1979年 | 6666篇 |
1978年 | 6695篇 |
1977年 | 6824篇 |
1976年 | 6833篇 |
1975年 | 6398篇 |
1974年 | 6208篇 |
1973年 | 6405篇 |
1972年 | 5005篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
942.
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
943.
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
944.
N. V. Shiran A. V. Gektin V. K. Komar I. M. Krasovitska V. V. Shlyahturov 《Radiation measurements》1995,24(4):435-437
Optical properties of pure and RE doped KMgF3 crystals were studied. Thermoluminescence curves are independent of the introduced impurity for all dopant besides europium. Emission, radiation damage and TL are found to be significantly dependent on the types of Eu-dopant added to the melt: europium fluoride or oxide. An intensive high temperature TL peak at 390°C in KMgF3(Eu2O3) may be used as a dosimetric one not only for ionizing but also for UV radiation. 相似文献
945.
946.
A. Maignan Ch. Simon V. Caignaert B. Raveau 《Zeitschrift für Physik B Condensed Matter》1995,99(1):305-310
The exploration of the magnetic and transport properties of four series of manganese perovskites, Pr0.7Ca0.34−xAxMnO3−δ (A=Sr, Ba), Pr0.7−xLaxCa0.3 MnO3−δ and Pr0.66Ca0.34−x
SrxMnO3−δ has allowed four phases with colossal magnetoresistive (CMR) properties to be isolated: Pr0.7Ca0.25Sr0.025MnO3−δ and Pr0.66Ca0.26Sr0.08MnO3−δ that exhibit a variation of resistance of 2.5. 107% and 109% at μ0 H=5 T for T=88 K and 50 K respectively, Pr0.58La0.12Ca0.3 MnO3−δ that exhibits a variation of 6.106% for μ0 H=5 T at T=80 K and Pr0.7Ba0.025Ca0.275MnO3−δ for which a resistance variation of 5.109%, at T=50 K, for μ0 H=5 T is evidenced. for each compound of this series except the barium phase, one observes that the temperature Tmax, which corresponds to the resistance maximum on the R(T) curves in zero magnetic field, increases dramatically as the mean
size of the interpolated cations increases, and that the CMR effect correlatively decreases dramatically. The comparison of
the two series Pr0.7Ca0.3−xSrxMnO3−δ and Pr0.66Ca0.34−xSrxMnO3−δ shows also the crucial role of the hole carrier density: for a same mean ionic radius of the interpolated cation Tmax is decreased of about 50 K by introducing 0.034 hole per Mn mole. 相似文献
947.
Y. Yamamoto H. Kidooka Y. Honda S. Yasuda 《International Journal of Infrared and Millimeter Waves》1995,16(3):579-589
A novel method using small neon glow lamps with electrodes is developed for measuring intense microwave field patterns. When the lamp axis coincide with the electric field direction, the lamp discharge starts at the feeblest microwave electric field strength. Therefore, the lamp axis shows the field direction and the discharge starting indicates the field strength. The field strength for starting the microwave discharge is less than the strength for AC discharge, because of its low loss discharge mechanism. In the experiments using a microwave oven, it has been demonstrated again comparing with the simulated results that the method is able to use for measuring the intense electric field strength and direction. 相似文献
948.
V. L. Bratman G. G. Denisov A. V. Savilov 《International Journal of Infrared and Millimeter Waves》1995,16(3):459-471
A relatively high level of the minimal electron energy at the gyrotron output even at very large spread in pitch factor is explained. An estimation of the recuperation efficiency, which can be obtained due to this effect, is given. 相似文献
949.
950.
Starting from a general hamiltonian system with superstable pairwise potential, we construct a stochastic dynamics by adding a noise term which exchanges the momenta of nearby particles. We prolve that, in the scaling limit, the time conserved quantities, energy, momenta and density, satisfy the Euler equation of conservation laws up to a fixed timet provided that the Euler equation has a smooth solution with a given initial data up to timet. The strength of the noise term is chosen to be very small (but nonvanishing) so that it disappears in the scaling limit.Research partially supported by U.S. National Science Foundation grants DMS 89001682, DMS 920-1222 and a grant from ARO, DAAL03-92-G-0317Research partially supported by U.S. National Science Foundation grants DMS-9101196, DMS-9100383, and PHY-9019433-A01, Sloan Foundation Fellowship and David and Lucile Packard Foundation Fellowship 相似文献