全文获取类型
收费全文 | 376524篇 |
免费 | 4126篇 |
国内免费 | 1519篇 |
专业分类
化学 | 203319篇 |
晶体学 | 5596篇 |
力学 | 16141篇 |
综合类 | 8篇 |
数学 | 42787篇 |
物理学 | 114318篇 |
出版年
2020年 | 2701篇 |
2019年 | 3004篇 |
2018年 | 3403篇 |
2017年 | 3346篇 |
2016年 | 5719篇 |
2015年 | 4162篇 |
2014年 | 5902篇 |
2013年 | 17445篇 |
2012年 | 13110篇 |
2011年 | 16321篇 |
2010年 | 10477篇 |
2009年 | 10567篇 |
2008年 | 14787篇 |
2007年 | 14874篇 |
2006年 | 13895篇 |
2005年 | 12944篇 |
2004年 | 11580篇 |
2003年 | 10206篇 |
2002年 | 10028篇 |
2001年 | 11621篇 |
2000年 | 8832篇 |
1999年 | 6876篇 |
1998年 | 5616篇 |
1997年 | 5564篇 |
1996年 | 5305篇 |
1995年 | 4924篇 |
1994年 | 4643篇 |
1993年 | 4623篇 |
1992年 | 5080篇 |
1991年 | 5087篇 |
1990年 | 4678篇 |
1989年 | 4662篇 |
1988年 | 4689篇 |
1987年 | 4537篇 |
1986年 | 4305篇 |
1985年 | 6158篇 |
1984年 | 6251篇 |
1983年 | 5119篇 |
1982年 | 5569篇 |
1981年 | 5359篇 |
1980年 | 5189篇 |
1979年 | 5232篇 |
1978年 | 5473篇 |
1977年 | 5273篇 |
1976年 | 5423篇 |
1975年 | 5005篇 |
1974年 | 5048篇 |
1973年 | 5360篇 |
1972年 | 3259篇 |
1971年 | 2425篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
A. Veider G. Badurek R. Grssinger H. Kronmüller 《Journal of magnetism and magnetic materials》1986,60(2-3):182-194
The domain configuration of amorphous ribbons with positive, vanishing and negative magnetostriction constant λs has been investigated by means of the longitudinal magneto-optical Kerr-effect and a three-dimensional neutron depolarization analysis. The influence of an external tensile stress on the domain arrangement depends on the sign and the magnitude of the magnetostriction constant and could be measured quantitatively in the depolarization experiment. With the aid of the optical observations domain models have been established; these models were tested and completed by means of an analytic calculation of the corresponding depolarization matrix and a comparison with experimental data. Domain reorientation processes within the ribbons under an imposed tensile stress were found to agree with theoretical predictions. The nearly nonmagnetostrictive alloys shows neither stripe domains nor simple wide domains but a more complicated structure with several layers of domains. 相似文献
993.
994.
C.T. Hsieh 《Applied Surface Science》2005,252(5):1899-1909
A magnetic force microscopy is used to examine the domain walls in nickel and cobalt films deposited by argon ion sputtering. Thin nickel films deposited at high substrate temperatures exhibit coexistent Bloch and Neel walls. Films grown at room temperature display alternative Bloch lines with cap switches. These films agglomerate to form grains after annealed at high temperatures. The film composed of larger grains behaves better nucleation implying magnetic domains of closure, while the film composed of smaller grains exhibits more defects implying alternative Bloch lines. We have also observed domain displacements and cap switches, which occur due to precipitation of particles in small grain size films. Stripe domains are observed for film thicknesses larger than 100 nm. They become zigzag cells when an external field of 1.5 T is applied perpendicular to the surface of the films. This experiment indicates that the domain sizes in thin films and the strip widths for thick films both depend on the square-root of the film thickness, which varies from 5 to 45 nm and from 100 to 450 nm, respectively. 相似文献
995.
This paper introduces a profile empirical likelihood and a profile conditionally empirical likelihood to estimate the parameter
of interest in the presence of nuisance parameters respectively for the parametric and semiparametric models. It is proven
that these methods propose some efficient estimators of parameters of interest in the sense of least-favorable efficiency.
Particularly, for the decomposable semiparametric models, an explicit representation for the estimator of parameter of interest
is derived from the proposed nonparametric method. These new estimations are different from and more efficient than the existing
estimations. Some examples and simulation studies are given to illustrate the theoretical results.
The first author is supported by NNSF projects (10371059 and 10171051) of China. The second author is supported by a grant
from The Research Grants Council of the Hong Kong Special Administrative Region, China (#HKU7060/04P). The third author is
supported by the University Research Committee of the University of Hong Kong and a grant from the Research Grants Council
of the Hong Kong Special Administrative Region, China (Project No. HKU7323/01M). 相似文献
996.
A particle imaging technique has been used to collect droplet displacement statistics in a round turbulent jet of air. Droplets are injected on the jet axis, and a laser sheet and position-sensitive photomultiplier tube are used to track their radial displacement and time-of-flight. Dispersion statistics can be computed which are Lagrangian or Eulerian in nature. The experiments have been simulated numerically using a second-order closure scheme for the jet and a stochastic simulation for the particle trajectories. Results are presented for non-vaporizing droplets of sizes from 35 to 160 μm. The simulations have underscored the importance of initial conditions and early droplet displacement history on the droplet trajectory for droplets with large inertia relative to the turbulence. Estimates of initial conditions have been made and their effect on dispersion is quantified. 相似文献
997.
998.
The arc discharge was studied in a transparent channel at an intense flow rate of nitrogen, hydrogen, air, carbon dioxide in the current range 100–1500 A. The internal diameter of the porous channel varied from 10 to 34 mm, the length - from 50 to 150 mm, the air and nitrogen flow rates - from 0.05 to 1.5 kg/s, hydrogen - from 0.005 to 0.05 kg/s. The electric field strength in the arc channel reached a value of 300 V/cm for N2 and 500 V/cm for H2. The effect of plasma thermochemical non-equilibrium was discovered. 相似文献
999.
Summary The role of chemical reactions in the selection of patterns in phase-separating mixtures is presented. Linearized theory and
computer simulation show that the initial long-wavelength instability characteristic of spinodal decomposition is suppressed
by chemical reactions, which restrict domain growth to intermediate length scales even in the late stages of phase separation.
Our findings suggest that chemical reactions may provide a novel way to stabilize and tune the steady-state morphology of
phase-separating materials.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
1000.
P. Schwab A. Kochemasov R. Kullmer D. Bäuerle 《Applied Physics A: Materials Science & Processing》1992,54(2):166-169
Pulsed-laser deposition of YBa2Cu3O7 in N2O permits lowering of the substrate temperature with respect to deposition in O2 atmosphere. Additional photodissociation of N2O near the substrate surface deteriorates the superconducting properties of deposited films.On leave from: Institute of Applied Physics of the Academy of Sciences of the USSR, SU-603600 Nishni Nowgorod, USSR 相似文献