全文获取类型
收费全文 | 98231篇 |
免费 | 5562篇 |
国内免费 | 4644篇 |
专业分类
化学 | 56014篇 |
晶体学 | 1332篇 |
力学 | 5534篇 |
综合类 | 322篇 |
数学 | 11861篇 |
物理学 | 33374篇 |
出版年
2022年 | 1492篇 |
2021年 | 1978篇 |
2020年 | 2296篇 |
2019年 | 2480篇 |
2018年 | 2849篇 |
2017年 | 2787篇 |
2016年 | 3454篇 |
2015年 | 2348篇 |
2014年 | 3424篇 |
2013年 | 4877篇 |
2012年 | 5029篇 |
2011年 | 5368篇 |
2010年 | 4250篇 |
2009年 | 4269篇 |
2008年 | 4464篇 |
2007年 | 4179篇 |
2006年 | 3810篇 |
2005年 | 3377篇 |
2004年 | 3036篇 |
2003年 | 2710篇 |
2002年 | 2829篇 |
2001年 | 2552篇 |
2000年 | 1989篇 |
1999年 | 1605篇 |
1998年 | 1537篇 |
1997年 | 1330篇 |
1996年 | 1295篇 |
1995年 | 1081篇 |
1994年 | 1156篇 |
1993年 | 1095篇 |
1992年 | 1061篇 |
1991年 | 1125篇 |
1990年 | 1119篇 |
1989年 | 1044篇 |
1988年 | 917篇 |
1987年 | 917篇 |
1986年 | 881篇 |
1985年 | 924篇 |
1984年 | 915篇 |
1983年 | 822篇 |
1982年 | 800篇 |
1979年 | 801篇 |
1978年 | 812篇 |
1977年 | 806篇 |
1976年 | 919篇 |
1975年 | 812篇 |
1974年 | 844篇 |
1973年 | 847篇 |
1972年 | 752篇 |
1971年 | 742篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
971.
Yu. V. Vandakurov 《Technical Physics》2003,48(3):298-302
In rotating stellar convective zones, heat transfer is shown to be associated with unbalanced azimuth forces arising in the
radially ascending (heated) or descending (cold) matter. The presence of a longitude-dependent magnetic field generates additional
azimuth forces, hence, new ways of compensating for the unbalanced forces. Generally speaking, this magnetic field is variable
but may be nearly static in layers where convective equilibrium is replaced by radiative equilibrium. The condition for the
coexistence of the static and usual fields is derived. To this end, an axisymmetric azimuth magnetic field of energy comparable
to the energy of rotation should be introduced into models under consideration. In such configurations, conditions for magnetic
field generation, as in the Sun, may appear. 相似文献
972.
The single domain size of BaFe12O19 powder with crystallite sizes less than 200 nm was produced using a citric acid precursor method. Fe3+ and Ba2+, in a molar ratio of 12, were chelated by COOH− in an aqueous solution. After ethylene glycol additions, esterification, dehydration, and calcination led to the formation of ester-derived BaFe12O19 powder. High pH and/or high citric acid contents in the starting solution are required to complete chelate metallic ions in the solution and to form pure barium ferrite powder at 1073 K. Pure single magnetic domain BaFe12O19 particles of M(30 kOe)≈54 emu/g, Mr≈28 emu/g, and Hc≈3.7 kOe were produced using [citric acid]/[metallic ions]=1.5 and pH7. 相似文献
973.
Effect of a magnetic field on the starting stress and mobility of individual dislocations in silicon
M. V. Badylevich Yu. L. Iunin V. V. Kveder V. I. Orlov Yu. A. Osip’yan 《Journal of Experimental and Theoretical Physics》2003,97(3):601-605
The strong effect of a magnetic field on the starting stress and mobility of individual dislocations is discovered in silicon grown by the Czochralski method with a high concentration of dissolved oxygen. It is shown that exposure of dislocations preliminarily introduced into the sample to a magnetic field considerably reduces the starting stresses for the motion of these dislocations. The effect is not observed in samples with a low oxygen concentration. It is assumed that the magnetic field induces singlet-triplet transitions in thermally excited states of silicon-oxygen complexes in the dislocation core, thus stimulating a change in the state (atomic configuration) of oxygen already located at dislocations. As a result, the mean binding energy of oxygen with a dislocation decreases. 相似文献
974.
Study of the viscoelastoplastic deformation of an element of a body with a three-branch loading path
Yu. N. Shevchenko R. G. Terekhov N. S. Braikovskaya S. M. Zakharov 《International Applied Mechanics》1991,27(12):1162-1167
Institute of Mechanics, Academy of Sciences of the Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 27, No. 12, pp. 26–33, December, 1991. 相似文献
975.
We consider estimation after a group sequential test about a multivariate normal mean, such as a χ2 test or a sequential version of the Bonferroni procedure. We derive the density function of the sufficient statistics and show that the sample mean remains to be the maximum likelihood estimator but is no longer unbiased. We propose an alternative Rao-Blackwell type unbiased estimator. We show that the family of distributions of the sufficient statistic is not complete, and there exist infinitely many unbiased estimators of the mean vector and none has uniformly minimum variance. However, when restricted to truncation-adaptable statistics, completeness holds and the Rao-Blackwell estimator has uniformly minimum variance. 相似文献
976.
977.
V. Yu. Venediktov 《Technical Physics》2007,52(1):126-128
The potential of the technology of reflective diffraction (holographic) optical elements intended for the EUV range is considered, and their application in projection lithography is discussed. 相似文献
978.
The purpose of this paper is to report some experimental results with HfSiO films formed on silicon substrates by electron beam evaporation (EB-PVD) and annealed at different temperatures. The images of atomic force microscope (AFM) indicated that HfSiO film annealed at 900 °C was still amorphous, with a surface roughness of 0.173 nm. X-ray photoelectron spectroscopy (XPS) analysis revealed that the chemical composition of the film was (HfO2)3(SiO2) and Hf-Si-O bonds existed in the annealed film. Electrical measurements showed that the equivalent oxide thickness (EOT) was 4 nm, the dielectric constant was around 6, the breakdown voltage was 10 MV/cm, the fixed charge density was −1.2 × 1012 cm−2, and the leakage current was 0.4 μA/cm2 at the gate bias of 2 V for 6 nm HfSiO film. The annealing after deposition effectively reduced trapping density and the leakage current, and eliminated hysteresis in the C-V curves. Annealing also induced SiO2 growth at the interface. 相似文献
979.
Yu. A. Konyaev 《Mathematical Notes》2007,81(3-4):477-482
We present a new method (the method of unitary transformations), which differs from the existing ones, for studying the stability and the norm of solutions of regular and singularly perturbed initial-value problems for nonautonomous linear and quasilinear systems of ODE with normal and “almost normal” matrices. Our results generalize similar theorems for the corresponding systems with constant matrices. This method allows one to avoid rather cumbersome traditional analysis, including the Lyapunov function method. For special classes of singularly perturbed problems, the method provides estimates for the norms of solutions in the presence of exponential or power boundary layers; these observations enrich the collection of known results in this field. 相似文献
980.
For a real measure with variation V(x) satisfying the estimate V(x) ≤ c 0 exp(Cx) and for the Laplace transform holomorphic in the disk {¦ -C¦ ≤ C} and having at least one pole of order m, we obtain lower bounds for the positive and negative parts of the measure V ± (x) > cx m , x > x 0. We establish lower bounds for V +- (x) on “short” intervals. Applications to number theory of the results obtained are considered. 相似文献