全文获取类型
收费全文 | 232957篇 |
免费 | 2229篇 |
国内免费 | 800篇 |
专业分类
化学 | 116940篇 |
晶体学 | 3996篇 |
力学 | 10759篇 |
综合类 | 1篇 |
数学 | 25519篇 |
物理学 | 78771篇 |
出版年
2020年 | 1789篇 |
2019年 | 2044篇 |
2018年 | 2720篇 |
2017年 | 2652篇 |
2016年 | 3913篇 |
2015年 | 2392篇 |
2014年 | 3968篇 |
2013年 | 10079篇 |
2012年 | 7535篇 |
2011年 | 9406篇 |
2010年 | 6692篇 |
2009年 | 6629篇 |
2008年 | 8716篇 |
2007年 | 8745篇 |
2006年 | 8289篇 |
2005年 | 7496篇 |
2004年 | 6928篇 |
2003年 | 6117篇 |
2002年 | 6062篇 |
2001年 | 7094篇 |
2000年 | 5377篇 |
1999年 | 4238篇 |
1998年 | 3565篇 |
1997年 | 3473篇 |
1996年 | 3295篇 |
1995年 | 3012篇 |
1994年 | 2953篇 |
1993年 | 3044篇 |
1992年 | 3153篇 |
1991年 | 3333篇 |
1990年 | 3086篇 |
1989年 | 3027篇 |
1988年 | 3067篇 |
1987年 | 2955篇 |
1986年 | 2802篇 |
1985年 | 3810篇 |
1984年 | 4007篇 |
1983年 | 3201篇 |
1982年 | 3412篇 |
1981年 | 3339篇 |
1980年 | 3235篇 |
1979年 | 3339篇 |
1978年 | 3424篇 |
1977年 | 3350篇 |
1976年 | 3451篇 |
1975年 | 3144篇 |
1974年 | 3151篇 |
1973年 | 3196篇 |
1972年 | 2237篇 |
1971年 | 1849篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
201.
Summary We have estimated and measured the daily thermal expansion of an oceanographic platform. This has been found negligible as
far as the calibration of a satellite altimeter is concerned. 相似文献
202.
Settling of a large solid particle in bioconvection flow caused by gyrotactic microorganisms is investigated. The particle is released from the top of the bioconvection chamber; its settling pattern depends on whether it is released in the centre of the bioconvection plume or at its periphery. The Chimera method is utilized; a subgrid is generated around a moving particle. The method suggested by Liu and Wang (Comput. Fluid 2004; 33 :223–255) is further developed to account for the presence of a moving boundary in the streamfunction‐vorticity formulation using the finite‐difference method. A number of cases for different release positions of the particle are computed. It is demonstrated that bioconvection can either accelerate or decelerate settling of the particle depending on the initial position of the particle relative to the plume centre. It is also shown that the particle impacts bioconvection plume by changing its shape and location in the chamber. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
203.
D. B. Kayumova Yu. P. Syrnikov N. V. Penkina M. N. Rodnikova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(10):1634-1635
The structural relaxation time for series of various liquids (alkanes, aliphatic alcohols, and diols) are calculated from published data on the shear viscosity and the heat of evaporation per unit volume. Liquids having a 3D H-bond network (diols) are characterized by relaxation times one to two orders of magnitudes longer than those typical of liquids without such a network (alkanes and aliphatic alcohols). 相似文献
204.
Henry P. McKean 《纯数学与应用数学通讯》2003,56(5):638-680
205.
The fine-structure parameters of a series of configurations of the first ion of indium and the gyromagnetic ratios in intermediate coupling are calculated by a semiempirical method in the single-configuration approximation. 相似文献
206.
207.
S. Mancini D. Vitali V. Giovannetti P. Tombesi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):417-422
We show that the optomechanical coupling between an optical cavity mode and two movable cavity mirrors is able to entangle
two different macroscopic oscillation modes of the mirrors. This continuous variable entanglement is maintained by the light
bouncing between the mirrors and is robust against thermal noise. In fact, it could be experimentally demonstrated using present
technology.
Received 2 September 2002 / Received in final form 10 October 2002 Published online 7 January 2003 相似文献
208.
We derive a test problem for evaluating the ability of time-steppingmethods to preserve the statistical properties of systems inmolecular dynamics. We consider a family of deterministic systemsconsisting of a finite number of particles interacting on acompact interval. The particles are given random initial conditionsand interact through instantaneous energy- and momentum-conservingcollisions. As the number of particles, the particle density,and the mean particle speed go to infinity, the trajectory ofa tracer particle is shown to converge to a stationary Gaussianstochastic process. We approximate this system by one describedby a system of ordinary differential equations and provide numericalevidence that it converges to the same stochastic process. Wesimulate the latter system with a variety of numerical integrators,including the symplectic Euler method, a fourth-order Runge-Kuttamethod, and an energyconserving step-and-project method. Weassess the methods' ability to recapture the system's limitingstatistics and observe that symplectic Euler performs significantlybetter than the others for comparable computational expense. 相似文献
209.
The ultraviolet band systemsA
1Π-X
1Σ+ of P14N and P15N were excited in an electrodeless tube containing traces of phosphorus specpure nitrogen and neon using a microwave discharge
(2450 MHz). Bands of the isotopic species, P15N, were obtained using15N2 enriched to 95.5%. Rotational analyses of eleven bands of P14N and sixteen bands of P15N were carried out. Three perturbing statese
3Σ−,d
3Δ andb
3Π, arising from the lower valence configurations were identified from the observed perturbations in thev′=0–4 levels of theA
1Π state. Deperturbation studies led to the determination of molecular constants of the perturbing states. Vibrational assignments
of the perturbing states were made from isotope shift studies. 相似文献
210.
We develop a theory of the magnetic-zenith effect (MZE) observed upon the ionosphere modification by powerful radio waves.
The dependences of MZE on main parameters, such as the magnetic-field inclination angle, pump-wave frequency and power, and
angular width of HF beam are obtained. The optimal elevation angle of pump-wave beam is predicted.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 772–787, September 2005. 相似文献