全文获取类型
收费全文 | 323902篇 |
免费 | 3510篇 |
国内免费 | 942篇 |
专业分类
化学 | 177779篇 |
晶体学 | 4969篇 |
力学 | 13781篇 |
综合类 | 11篇 |
数学 | 32626篇 |
物理学 | 99188篇 |
出版年
2018年 | 2600篇 |
2016年 | 4440篇 |
2015年 | 3046篇 |
2014年 | 4524篇 |
2013年 | 13316篇 |
2012年 | 9450篇 |
2011年 | 11903篇 |
2010年 | 8073篇 |
2009年 | 8056篇 |
2008年 | 10881篇 |
2007年 | 11083篇 |
2006年 | 10515篇 |
2005年 | 9607篇 |
2004年 | 8740篇 |
2003年 | 7766篇 |
2002年 | 7684篇 |
2001年 | 9351篇 |
2000年 | 7168篇 |
1999年 | 5650篇 |
1998年 | 4625篇 |
1997年 | 4622篇 |
1996年 | 4418篇 |
1995年 | 4112篇 |
1994年 | 4014篇 |
1993年 | 3768篇 |
1992年 | 4457篇 |
1991年 | 4410篇 |
1990年 | 4235篇 |
1989年 | 4249篇 |
1988年 | 4133篇 |
1987年 | 4068篇 |
1986年 | 3806篇 |
1985年 | 5150篇 |
1984年 | 5258篇 |
1983年 | 4333篇 |
1982年 | 4673篇 |
1981年 | 4491篇 |
1980年 | 4363篇 |
1979年 | 4621篇 |
1978年 | 4988篇 |
1977年 | 4738篇 |
1976年 | 4710篇 |
1975年 | 4493篇 |
1974年 | 4506篇 |
1973年 | 4522篇 |
1972年 | 2971篇 |
1971年 | 2564篇 |
1968年 | 2887篇 |
1967年 | 3101篇 |
1966年 | 2627篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
981.
A. Yu. Kolesov E. F. Mishchenko N. Kh. Rozov 《Proceedings of the Steklov Institute of Mathematics》2007,259(1):101-127
We carry out a detailed analysis of the existence, asymptotics, and stability problems for periodic solutions that bifurcate
from the zero equilibrium state in systems with large delay. The account is based on a specific meaningful example given by
a certain scalar nonlinear second-order differential-difference equation that is a mathematical model of a single-circuit
RCL oscillator with delay in a feedback loop. 相似文献
982.
L. Erbe A. Peterson S.H. Saker 《Journal of Mathematical Analysis and Applications》2007,329(1):112-131
In this paper, we extend the oscillation criteria that have been established by Hille [E. Hille, Non-oscillation theorems, Trans. Amer. Math. Soc. 64 (1948) 234-252] and Nehari [Z. Nehari, Oscillation criteria for second-order linear differential equations, Trans. Amer. Math. Soc. 85 (1957) 428-445] for second-order differential equations to third-order dynamic equations on an arbitrary time scale T, which is unbounded above. Our results are essentially new even for third-order differential and difference equations, i.e., when T=R and T=N. We consider several examples to illustrate our results. 相似文献
983.
984.
985.
N. B. Valetova L. L. Semenycheva I. S. Il’ichev A. N. Artemov D. F. Grishin 《Russian Journal of Applied Chemistry》2007,80(5):818-821
Features of radical polymerization of styrene in the presence of (diphenylbutadiene)tricarbonylchromium were studied. 相似文献
986.
R. Brunner R. Meisels F. Kuchar M. ElHassan J. Bird K. Ishibashi 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):491
The properties of open quantum dots are examined in magneto-transport. The quantum dots are prepared from a two-dimensional electron system (2DES) in AlGaAs/GaAs by lateral gate structures. These quantum dots are open, i.e. they are still connected to the surrounding 2DES regions. The low magnetic field magnetoresistance shows peak structures. These structures can be related to semi-classical ballistic trajectories in the confining potential of a dot. The calculations of different confining potentials (abrupt “hard-wall” and parabolic “soft-wall”) are compared with the experimental results. The experiments are better described by a soft-wall potential. 相似文献
987.
M. C. Caracoche J. A. Martínez P. C. Rivas M. A. Taylor A. F. Pasquevich S. Barolin O. A. de Sanctis 《Hyperfine Interactions》2007,179(1-3):87-93
The hyperfine quadrupole interaction at Hf sites in films and powders of 14 mol% CaO–HfO2 and 20 mol% CaO–HfO2 has been determined as a function of temperature. Results indicate the formation of a cubic solid solution and other microstructures assigned to the ?1 (CaHf4O9) and ?2 (Ca6Hf19O44) phases. Dynamical effects on the electric field gradient reveal the existence of oxygen vacancies movements in the solid solution. The thermal behavior of the relaxation constant observed in films allowed the determination of activation energies of 0.54 eV and 0.70 eV for the 14 mol% and 20 mol% CaO doped hafnias, respectively. The influence of the microdomains and the stability of the cubic solid solution are discussed. 相似文献
988.
989.
Werner WinterGünther W.H Höhne 《Thermochimica Acta》2003,403(1):43-53
A method for measuring heat capacities of small samples using a chip-calorimeter and a heat pulse technique is described. The theoretical background to calculate the heat transport properties and the heat capacity of the sample from the pulse response function is given. Problems and potentials of the method are discussed. An example is given. 相似文献
990.
D. H. Beck 《Progress in Particle and Nuclear Physics》2003,50(2):248-449
A brief review of the structure of the nucleon as determined through parity-violating electron scattering is presented. The relationship between the electromagnetic and neutral weak currents is developed in a pedagogical introduction. Recent results and present measurements are discussed. 相似文献