全文获取类型
收费全文 | 379614篇 |
免费 | 6961篇 |
国内免费 | 5260篇 |
专业分类
化学 | 190593篇 |
晶体学 | 5347篇 |
力学 | 19944篇 |
综合类 | 328篇 |
数学 | 56257篇 |
物理学 | 119366篇 |
出版年
2022年 | 2775篇 |
2021年 | 3577篇 |
2020年 | 3996篇 |
2019年 | 4436篇 |
2018年 | 12521篇 |
2017年 | 12943篇 |
2016年 | 10491篇 |
2015年 | 5149篇 |
2014年 | 6938篇 |
2013年 | 13580篇 |
2012年 | 14939篇 |
2011年 | 23417篇 |
2010年 | 15508篇 |
2009年 | 15581篇 |
2008年 | 20822篇 |
2007年 | 23624篇 |
2006年 | 11043篇 |
2005年 | 14990篇 |
2004年 | 11365篇 |
2003年 | 10841篇 |
2002年 | 9149篇 |
2001年 | 8219篇 |
2000年 | 6685篇 |
1999年 | 4938篇 |
1998年 | 4399篇 |
1997年 | 4185篇 |
1996年 | 4112篇 |
1995年 | 3381篇 |
1994年 | 3524篇 |
1993年 | 3492篇 |
1992年 | 3589篇 |
1991年 | 3697篇 |
1990年 | 3593篇 |
1989年 | 3513篇 |
1988年 | 3348篇 |
1987年 | 3277篇 |
1986年 | 3185篇 |
1985年 | 3893篇 |
1984年 | 4099篇 |
1983年 | 3345篇 |
1982年 | 3585篇 |
1981年 | 3371篇 |
1980年 | 3140篇 |
1979年 | 3466篇 |
1978年 | 3639篇 |
1977年 | 3567篇 |
1976年 | 3652篇 |
1975年 | 3427篇 |
1974年 | 3418篇 |
1973年 | 3602篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
A. Vukics H. Ritsch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):585-599
We present a framework for efficiently performing Monte Carlo
wave-function simulations in cavity QED with moving particles. It
relies heavily on the object-oriented programming paradigm as realised
in C++, and is extensible and applicable for simulating open
interacting qua
ntum dynamics in general. The user is provided with a
number of “elements”, e.g. pumped moving particles, pumped lossy
cavity modes, and various interactions to compose complex interacting
systems, which contain several particles moving in electromagnetic
fields of various configurations, and perform wave-function
simulations on such systems. A number of tools are provided to
facilitate the implementation of new elements. 相似文献
942.
Numerical studies were conducted to investigate the natural convection heat transfer around a uniformly heated thin plate
with arbitrary inclination in an infinite space. The numerical approach was based on the finite volume technique with a nonstaggered
grid arrangement. For handling the pressure–velocity coupling the SIMPLE-algorithm was used. QUICK scheme and first order
upwind scheme were employed for discretization of the momentum and energy convective terms respectively. Plate width and heating
rate were used to vary the modified Rayleigh number over the range of 4.8×106 to 1.87×108. Local and average heat transfer characteristics were compared with regarding to the inclination angle. The empirical expressions
for local and average Nusselt number were correlated. It has been found that for inclination angle less than 10∘, the flow and heat transfer characteristics are complicated and the average Nusselt number can not be correlated by one equation
while for inclination angle larger than 10∘, the average Nusselt number can be correlated into an elegant correlation.
Received on 18 April 2001 / Published online: 29 November 2001 相似文献
943.
944.
D. P. Samsonov E. M. Pasynkova G. V. Bornovalova 《Journal of Analytical Chemistry》2002,57(6):513-517
It is shown that toxicant MX can be reliably identified and determined quantitatively by ion-trap tandem mass spectrometry with an accuracy as high as that for high-resolution mass spectrometry. 相似文献
945.
Experimental research on the improvement of the sensitivity and time resolution of pulsed magnetic resonance spectrometers
is discussed. It is shown that application of a time-variable feedback of a signal to the input of the receiver amplifier
can decouple, the “fixed” relationship between the quality factorQ and the ringdown time of the resonance system. Experiments were performed with low-frequency, radio-frequency and microwave
pulse-type magnetic resonance receivers. Modifications of an S/C-band electron spin echo modulation spectrometer carried out
to check the “time-variable feedback” performance are described. It is demonstrated that the application of a time-variable
feedback can significantly reduce the ringdown time and improve the recovery properties of the magnetic resonance receiver
system. It is also demonstrated that the time-variable feedback can improve the overall receiver sensitivity due to the fact
that the working bandwidth of the resonance system can be optimized separately for the transmitting and the receiving mode.
Signal values could be increased at least three times and the signal-to-noise ratio about 1.5–2 times. The largest improvement
is achieved with the initially overcoupled resonator. Experimental spectra of test samples for different settings of the time-variable
feedback are shown. 相似文献
946.
C. Bogani M. G. Gasparo A. Papini 《Journal of Optimization Theory and Applications》2007,134(1):47-59
We propose a pattern search method to solve a classical nonsmooth optimization problem. In a deep analogy with pattern search
methods for linear constrained optimization, the set of search directions at each iteration is defined in such a way that
it conforms to the local geometry of the set of points of nondifferentiability near the current iterate. This is crucial to
ensure convergence. The approach presented here can be extended to wider classes of nonsmooth optimization problems. Numerical
experiments seem to be encouraging.
This work was supported by M.U.R.S.T., Rome, Italy. 相似文献
947.
S. B. Gashkov 《Moscow University Mathematics Bulletin》2007,62(3):87-89
It is shown that Lozhkin’s method (1981) for minimization of the depth of formulas with a bounded number of changing types of elements in paths from input to output and Hoover-Klawe-Pippenger’s method (technical report in 1981, journal publication in 1984) for minimization of the depth of circuits with unbounded branching by insertion of trees from buffers with bounded branching of outputs for each buffer are dual to each other and can be proved by one and the same method. 相似文献
948.
E. P. Vdovin 《Doklady Mathematics》2007,76(1):544-547
949.
950.
O. N. Karpenkov 《Monatshefte für Mathematik》2007,152(3):217-249
In this paper we develop an integer-affine classification of three-dimensional multistory, completely empty convex marked
pyramids. We apply it to obtain the complete lists of compact two-dimensional faces of multidimensional continued fractions
lying in planes at integer distances 2, 3, 4, … to the origin. The faces are considered up to the action of the group of
integer-linear transformations. 相似文献