全文获取类型
收费全文 | 148909篇 |
免费 | 1555篇 |
国内免费 | 717篇 |
专业分类
化学 | 59100篇 |
晶体学 | 1844篇 |
力学 | 10152篇 |
综合类 | 10篇 |
数学 | 38642篇 |
物理学 | 41433篇 |
出版年
2022年 | 514篇 |
2021年 | 651篇 |
2020年 | 651篇 |
2019年 | 633篇 |
2018年 | 11160篇 |
2017年 | 10873篇 |
2016年 | 7279篇 |
2015年 | 1813篇 |
2014年 | 1718篇 |
2013年 | 3708篇 |
2012年 | 6798篇 |
2011年 | 14177篇 |
2010年 | 8183篇 |
2009年 | 8604篇 |
2008年 | 9951篇 |
2007年 | 11887篇 |
2006年 | 3312篇 |
2005年 | 4032篇 |
2004年 | 3981篇 |
2003年 | 4069篇 |
2002年 | 2989篇 |
2001年 | 3495篇 |
2000年 | 2658篇 |
1999年 | 1865篇 |
1998年 | 1423篇 |
1997年 | 1341篇 |
1996年 | 1246篇 |
1995年 | 999篇 |
1994年 | 879篇 |
1993年 | 815篇 |
1992年 | 1114篇 |
1991年 | 1090篇 |
1990年 | 974篇 |
1989年 | 901篇 |
1988年 | 872篇 |
1987年 | 929篇 |
1986年 | 792篇 |
1985年 | 1025篇 |
1984年 | 979篇 |
1983年 | 672篇 |
1982年 | 692篇 |
1981年 | 668篇 |
1980年 | 637篇 |
1979年 | 750篇 |
1978年 | 777篇 |
1977年 | 749篇 |
1976年 | 679篇 |
1975年 | 564篇 |
1974年 | 596篇 |
1973年 | 543篇 |
排序方式: 共有10000条查询结果,搜索用时 750 毫秒
91.
The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method. 相似文献
92.
Julio Castellanos 《Mathematische Zeitschrift》2002,239(4):777-802
We consider complete ideals supported on finite sequences of infinitely near points, in regular local rings with dimensions
greater than two. We study properties of factorizations in Lipman special *-simple complete ideals. We relate it to a type
of proximity, linear proximity, of the points, and give conditions in order to have unique factorization. Several examples
are presented.
Received: 2 February 2000 / in final form: 14 March 2001 / Published online: 18 January 2002 相似文献
93.
94.
95.
Y.Y. Lee 《Applied Acoustics》2002,63(11):1157-1175
The nonlinear natural frequency of a rectangular box, which consists of one flexible plate and five rigid plates, is studied in this paper. The flexible plate is assumed to vibrate like a simple piston. The behavior of the structural-acoustic coupling between the flexible plate and the air cavity is analyzed by using the proposed finite element modal method. The system finite element equation is reduced and expressed in terms of the modal coordinates with small degrees of freedom by using the proposed reduction method. The system nonlinear stiffness matrix representing the large amplitude vibration can be transformed to be a constant modal matrix. The natural frequencies are determined by using the harmonic balance method to solve the eigenvalue equations of the structural-acoustic system. The effect of the cavity depth on the natural frequencies and convergence studies are discussed in detail. 相似文献
96.
Alexander Krasnosel'skii Dmitrii Rachinskii 《NoDEA : Nonlinear Differential Equations and Applications》2002,9(1):93-115
We consider autonomous systems with a nonlinear part depending on a parameter and study Hopf bifurcations at infinity. The
nonlinear part consists of the nonlinear functional term and the Prandtl--Ishlinskii hysteresis term. The linear part of the
system has a special form such that the close-loop system can be considered as a hysteresis perturbation of a quasilinear
Hamiltonian system. The Hamiltonian system has a continuum of arbitrarily large cycles for each value of the parameter. We
present sufficient conditions for the existence of bifurcation points for the non-Hamiltonian system with hysteresis. These
bifurcation points are determined by simple characteristics of the hysteresis nonlinearity. 相似文献
97.
K. Yatsu T. Cho H. Higaki M. Ichimura K. Ishii Y. Ishimoto M. K. Islam A. Itakura I. Katanuma J. Kohagura Y. Nakashima T. Saito Y. Takemura Y. Tatematsu M. Yoshida M. Yoshikawa 《Czechoslovak Journal of Physics》2002,52(10):1143-1148
GAMMA 10 experiments have advanced in high density experiments after the last EPS Workshop where we reported high density
plasma production by using an ion cyclotron range of frequency heating at a high harmonic frequency and neutral beam injection
in the central cell. Recently a high density plasma was obtained with much improved reproducibility than before and without
degradation of diamagnetic signal. The high density plasma was attained by adjusting the spacing of the conducting plates
installed in the anchor transition regions. Dependencies of particle confinement time, ion energy confinement time and plasma
confining potential on plasma density were obtained for the first time in the high density region.
Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreus, Switzerland, June 23–24,
2002. 相似文献
98.
Claudia-Elisabeth Wulz 《Czechoslovak Journal of Physics》2002,52(3):C155-C170
The principal physics goals of the Compact Muon Solenoid experiment under construction at the Large Hadron Collider at CERN in Geneva are reviewed. Procedures to search for the Standard Model Higgs boson, supersymmetric Higgses and other supersymmetric particles are described. 相似文献
99.
Y. CHENL. GUO 《Journal of sound and vibration》2002,254(4):727-732
A proof is offered for the equivalence of the group velocity and the energy velocity for elastic waves in a free anisotropic homogenous plate. The proof is valid in the case where the group velocity may be negative while the wave number is positive. 相似文献
100.
Several 5-substituted derivatives of 7-ethoxycarbonyl-6,8-dimethyl-1(2H)- phthalazinone were prepared by means of nitration, reductive amination, and diazonium decomposition. The substituents introduced included NO2, NH2, F, Cl, CN. Among the derivatives, the fluorine compound was obtained only in poor yield because intramolecular cyclization occurred predominantly. 相似文献