全文获取类型
收费全文 | 337884篇 |
免费 | 2770篇 |
国内免费 | 890篇 |
专业分类
化学 | 162080篇 |
晶体学 | 5036篇 |
力学 | 16557篇 |
综合类 | 2篇 |
数学 | 50590篇 |
物理学 | 107279篇 |
出版年
2020年 | 1764篇 |
2019年 | 2037篇 |
2018年 | 10974篇 |
2017年 | 11786篇 |
2016年 | 7782篇 |
2015年 | 3437篇 |
2014年 | 4009篇 |
2013年 | 11265篇 |
2012年 | 12248篇 |
2011年 | 22149篇 |
2010年 | 13530篇 |
2009年 | 13500篇 |
2008年 | 19308篇 |
2007年 | 22853篇 |
2006年 | 8549篇 |
2005年 | 14616篇 |
2004年 | 10404篇 |
2003年 | 9530篇 |
2002年 | 7507篇 |
2001年 | 7355篇 |
2000年 | 5660篇 |
1999年 | 4248篇 |
1998年 | 3592篇 |
1997年 | 3593篇 |
1996年 | 3456篇 |
1995年 | 3229篇 |
1994年 | 3029篇 |
1993年 | 3071篇 |
1992年 | 3359篇 |
1991年 | 3401篇 |
1990年 | 3211篇 |
1989年 | 3172篇 |
1988年 | 3245篇 |
1987年 | 3107篇 |
1986年 | 2996篇 |
1985年 | 4062篇 |
1984年 | 4244篇 |
1983年 | 3477篇 |
1982年 | 3828篇 |
1981年 | 3720篇 |
1980年 | 3594篇 |
1979年 | 3643篇 |
1978年 | 3882篇 |
1977年 | 3627篇 |
1976年 | 3864篇 |
1975年 | 3435篇 |
1974年 | 3555篇 |
1973年 | 3898篇 |
1972年 | 2363篇 |
1971年 | 1807篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
N. L. Dmitruk O. Yu. Borkovskaya R. V. Konakova I. B. Mamontova S. V. Mamykin D. I. Voitsikhovskiy 《Technical Physics》2002,47(6):698-702
The effect of 60Co gamma irradiation at doses of 103-2×105 Gy on the photoconversion and dark I-V characteristics of Au/GaAs surface-barrier solar cells (SCs) is studied. The morphology of the interface microrelief is varied
to reach the highest photoconversion efficiency. Of the two types of microrelief morphology (dendritic and quasi-grating)
obtained by the chemical anisotropic etching of n-(100)GaAs, the latter is more promising, particularly for SCs designed for space application, since the associated SCs offer
higher efficiency and radiation resistance. 相似文献
192.
A detailed analysis is made within perturbative QCD of the decays into gluon jets of P-wave and S-wave quarkonia (JPC = 0++, 1++, 2++, 1+? and 0?+, 1??). For all those states we compute to leading non-trivial order in αs the conventional fraction f(?, δ) of the jet-like hadronic final states, characterized by the back-to-back cone of half angle δ, in which all but a small fraction ? of the total energy is emitted. To the same order we give also the average values of thrust momenta and spherocity distributions. 相似文献
193.
Inventiones mathematicae - 相似文献
194.
195.
196.
S. P. Mukherjee A. K. Chattopadhyay 《The Journal of the Operational Research Society》1989,40(5):489-494
Consider an organization with several categories of staff, each having a specified number of members. The age of entry into service and the age of retirement are both specified. Withdrawals occur at time-independent rates. Under this set-up, the authors have computed the maximum ages at which promotions should take place, assuming that the staff members continuing at various ages are random. Some illustrative calculations have been carried out. 相似文献
197.
We describe a new algorithm which uses the trajectories of a discrete dynamical system to sample the domain of an unconstrained objective function in search of global minima. The algorithm is unusually adept at avoiding nonoptimal local minima and successfully converging to a global minimum. Trajectories generated by the algorithm for objective functions with many local minima exhibit chaotic behavior, in the sense that they are extremely sensitive to changes in initial conditions and system parameters. In this context, chaos seems to have a beneficial effect: failure to converge to a global minimum from a given initial point can often be rectified by making arbitrarily small changes in the system parameters. 相似文献
198.
199.
The diffraction of plane surface gravitational waves by the edge of an ice cover lying on the surface of an incompressible fluid of infinitely great depth is considered. The ice cover is simulated by a thin elastic plate. The wave reflection and transmission coefficients are determined when it interacts with the ice cover. A wave field is constructed in the fluid under the conditions that a periodic lumped force and a lumped moment act on the edge of the ice cover. It is shown that as the incident wavelength increases the reflection coefficient tends to zero and the transmission coefficient tends to unity. 相似文献
200.
N. S. Simonović 《Few-Body Systems》2006,38(2-4):139-145
In agreement with the Kohn theorem the relative motion (rel) of three electrons in a two-dimensional parabolic trap separates
from the centre-of-mass (CM) motion. By introducing new coordinates the Hamiltonian for relative motion in the approximation
of non-interacting electrons can be taken to the normal form. The eigenstates of the normalized Hamiltonian are products of
the Fock-Darwin states for normal modes. The energy levels for relative motion are obtained by diagonalizing the exact Hamiltonian
in the eigenbasis for the non-interacting case. In this basis the interaction matrix elements can be obtained in the analytical
form. Since the rank of the Hamiltonian matrix is significantly reduced, the calculations are faster and more accurate than
those for the full (CM + rel) motion. This advantage is especially important for the calculations of excited states and the
analysis of energy spectra. 相似文献