全文获取类型
收费全文 | 163736篇 |
免费 | 868篇 |
国内免费 | 310篇 |
专业分类
化学 | 63281篇 |
晶体学 | 2470篇 |
力学 | 10376篇 |
综合类 | 8篇 |
数学 | 29961篇 |
物理学 | 58818篇 |
出版年
2022年 | 420篇 |
2021年 | 459篇 |
2020年 | 446篇 |
2019年 | 426篇 |
2018年 | 10072篇 |
2017年 | 10954篇 |
2016年 | 5243篇 |
2015年 | 1582篇 |
2014年 | 1119篇 |
2013年 | 2624篇 |
2012年 | 6896篇 |
2011年 | 16274篇 |
2010年 | 9841篇 |
2009年 | 9995篇 |
2008年 | 14071篇 |
2007年 | 17736篇 |
2006年 | 2667篇 |
2005年 | 9631篇 |
2004年 | 5747篇 |
2003年 | 5413篇 |
2002年 | 3163篇 |
2001年 | 3181篇 |
2000年 | 2401篇 |
1999年 | 1526篇 |
1998年 | 1072篇 |
1997年 | 1017篇 |
1996年 | 997篇 |
1995年 | 872篇 |
1994年 | 786篇 |
1993年 | 685篇 |
1992年 | 1010篇 |
1991年 | 1001篇 |
1990年 | 910篇 |
1989年 | 821篇 |
1988年 | 823篇 |
1987年 | 882篇 |
1986年 | 729篇 |
1985年 | 970篇 |
1984年 | 931篇 |
1983年 | 661篇 |
1982年 | 655篇 |
1981年 | 625篇 |
1980年 | 588篇 |
1979年 | 733篇 |
1978年 | 766篇 |
1977年 | 691篇 |
1976年 | 644篇 |
1975年 | 536篇 |
1974年 | 574篇 |
1973年 | 545篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
N. A. Kuzmina N. N. Eremin E. I. Marchenko I. L. Svetlov N. A. Muromtsev A. V. Neuman D. A. Yakushev 《Crystallography Reports》2018,63(3):319-326
Structural models of the α, β, and γ modifications of Nb5Si3 silicides, which are used as a reinforcing phase in composites obtained in situ based on the Nb?Si system, have been constructed by computer simulation methods. A geometric analysis of unit cells is performed using the H-poisk program to estimate the voids existing in the structures. The results of measuring the number of voids and their sizes are reported. A conclusion about possible diffusion paths of interstitial boron, carbon, nitrogen and oxygen atoms is drawn based on the calculation results, and the solubility of these impurities in the structure of each Nb5Si3 modification is estimated. 相似文献
92.
S. Q. Hou W. Wang Z. Y. Wang Z. W. Hu K. Liu 《Journal of Applied Mechanics and Technical Physics》2018,59(1):153-162
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages. 相似文献
93.
94.
K. E. Prikhodko M. M. Dementyeva B. A. Gurovich D. A. Komarov L. V. Kutuzov 《Crystallography Reports》2018,63(2):241-244
The change in the free-electron density in ultrathin (5 nm) superconducting NbN films in the initial state and after irradiation by O+ ions to doses of (0.1–0.9) × 1017 cm–2 has been studied by electron energy-loss spectroscopy (EELS). The analysis has been performed on cross section samples prepared by the focused ion beam method, using plasmon oscillations with energies up to 50 eV. The radiation-induced replacement of nitrogen atoms with oxygen atoms in niobium nitride is found to change the electrical properties of the material, which leads to a decrease in the free-electron density with an increase in the irradiation dose. 相似文献
95.
V. P. Danko S. N. Diyanova A. G. Abazyan 《Journal of Applied Mechanics and Technical Physics》2018,59(4):673-678
Hydrodynamic regimes of heat and mass transfer apparatuses with a moving packing are considered. Relations defining the critical velocity, the loss of momentum in the working area, and the dynamic thickness of the layer of packing elements are obtained which are necessary for engineering calculations. 相似文献
96.
The problem of describing the behavior of a highly filled polymeric material under compression, which was preceded by preliminary compression and unloading, is considered. The peculiarity of the compression diagrams obtained in the experiment is the downward convexity of the curves of the stress modulus versus time. To solve this problem, a variant of the non-linear endochronic theory of aging viscoelastic materials with several aging and viscosity functions and a numerical-graphical method for identifying the properties of viscoelasticmaterials proposed by the authors earlier, suggesting comparison of the deformation diagrams of intact samples and those that received preliminary damage, are used. 相似文献
97.
98.
M. Kroon E. Andreasson E. Persson Jutemar V. Petersson L. Persson M. Dorn P.A.T. Olsson 《Experimental Mechanics》2018,58(1):75-86
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters. 相似文献
99.
The method of many scales was used to construct an asymptotic expansion up to thirdorder terms for the velocity potential of a fluid of finite depth and the flexural deformations of a floating elastic plate arising from the interaction of harmonics of finite-amplitude progressive surface waves. An expression for the second-harmonic amplitude was obtained, and critical values of the wavenumber were determined. Vibrations of plates with different thicknesses and elastic modulus were analyzed. Vertical displacements of the plate under flexural deformation were studied. 相似文献
100.
A. V. Zvyagin 《Siberian Mathematical Journal》2018,59(5):843-859
We study the problem of existence of a weak solution to the initial-boundary value thermoviscoelasticity problem for the model describing the motion of weakly concentrated water solutions of polymers. 相似文献