全文获取类型
收费全文 | 15262篇 |
免费 | 2777篇 |
国内免费 | 1428篇 |
专业分类
化学 | 5095篇 |
晶体学 | 279篇 |
力学 | 3853篇 |
综合类 | 196篇 |
数学 | 1726篇 |
物理学 | 8318篇 |
出版年
2024年 | 49篇 |
2023年 | 168篇 |
2022年 | 524篇 |
2021年 | 541篇 |
2020年 | 518篇 |
2019年 | 445篇 |
2018年 | 424篇 |
2017年 | 551篇 |
2016年 | 723篇 |
2015年 | 599篇 |
2014年 | 838篇 |
2013年 | 1424篇 |
2012年 | 917篇 |
2011年 | 1020篇 |
2010年 | 883篇 |
2009年 | 935篇 |
2008年 | 957篇 |
2007年 | 1046篇 |
2006年 | 916篇 |
2005年 | 809篇 |
2004年 | 660篇 |
2003年 | 667篇 |
2002年 | 538篇 |
2001年 | 465篇 |
2000年 | 447篇 |
1999年 | 355篇 |
1998年 | 387篇 |
1997年 | 282篇 |
1996年 | 230篇 |
1995年 | 198篇 |
1994年 | 188篇 |
1993年 | 154篇 |
1992年 | 109篇 |
1991年 | 94篇 |
1990年 | 74篇 |
1989年 | 55篇 |
1988年 | 43篇 |
1987年 | 38篇 |
1986年 | 34篇 |
1985年 | 45篇 |
1984年 | 20篇 |
1983年 | 8篇 |
1982年 | 22篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1979年 | 14篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Theoretical models for Monte Carlo simulation of radiative processes, i.e. bremsstrahlung and characteristic x-ray emission, are presented. Possible strategies for simulating electron transport are briefly described. For mechanisms involving energy loss and angular deflections, difficulties for strict implementation of accurate numerical differential cross sections still remain due to the strong correlations between these variables. Practical solutions for the case of inelastic collisions and bremsstrahlung emission are described. Comparisons of simulation results with experimental data for several problems of interest in electron probe microanalysis are presented. 相似文献
112.
Software Cold Test Simulation of Coupled Cavity Slow-Wave Structure in Millimeter Wave TWT 总被引:2,自引:0,他引:2
In this paper, the software cold-test simulation method to obtain RF dispersion, interaction impedance by MAFIA software is discussed considering effect of the conducting barrel in the millimeter-wave TWT. The dispersion simulation result is obtained more consistent with experiment data than the method that ignoring effect of the conducting barrel. By changing the structure parameter, high frequency characteristic will be affected. The change relationship of high frequency characteristic with structure parameter is obtained. The different calculation methods of the interaction impedance are discussed. These results are received and are consistent with experiment data. 相似文献
113.
LI Na ZHAO Degang & YANG Hui State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences Beijing China 《中国科学G辑(英文版)》2004,47(6):694-701
Because of their large band-gap, large high-field electron velocity, large breakdownfield, and large thermal conductivity, GaN and its heterojunction with AlGaN and InGaNhave foreseeable potential in the applications of high-power/temperature electronics, andoptoelectronic devices operative in UV and visible wavelength. Polarization inducedelectric field can reach the magnitude of ~MV/cm[1,2]. For AlGaN/GaN based FETs theconcentration of sheet carrier induced by polarization in the cha… 相似文献
114.
115.
116.
Statics of elasto-plastic media is stated in terms of eigenstrains acting upon a background elastic problem with fixed (initial) stiffness. In order to minimize the number of unknowns and to provide computationally cheap algorithms plastic multipliers are used as main driving variables. Fixed-point type iterations are suggested for computing plastic multipliers within the load increment. Numerical experiments results are shown to be in good correlation with other software results. A range of problems is outlined where the usage of the proposed algorithms can be advantageous. 相似文献
117.
In this Letter, structural properties of liquid Ni20Al80 have been studied through molecular dynamics (MD) simulations, and results agree well with X-ray experiments. The prepeak in the structure factor manifests the existence of medium-range structural order (MRSO) in liquid Ni20Al80. Analyses in MRSO reveal the dominance of ideal icosahedra and defective icosahedra which, furthermore, form clusters and share common atoms. 相似文献
118.
We couple a morphological study of an immiscible binary AB mixture with a micromechanical simulation to determine how the spatial distribution of the A and B domains and the interfacial region (interphase) affects the mechanical behavior of the blend. The morphological studies are conducted through a three-dimensional Cahn-Hilliard (CH) simulation. Through the CH calculations, we obtain the size and structure of the domains for different blend compositions. The output of the CH model serves as the input to the Lattice Spring Model (LSM), which consists of a three-dimensional network of springs. In particular, the location of the different phases is mapped onto the LSM lattice and the appropriate force constants are assigned to the LSM sites. A stress is applied to the LSM lattice and we calculate the elastic response of the material. We find that the local stress and strain fields are highly dependent on the morphology of the system. By integrating the morphological and mechanical models, we can isolate how modifications in the composition of the mixture affect the macroscopic behavior. Thus, we can establish how choices made in the components affect the ultimate performance of the material. 相似文献
119.
120.
Conducting drop tests to investigate impact behavior and identify failure mechanisms of small-size electronic products is
generally expensive and time-consuming. Nevertheless, strict drop/impact performance criteria for hand-held electronic products
such as cellular phones play a decisive role in the design because they must withstand unexpected shocks. The design of product
durability on impact has heavily relied on the designer's intuition and experience. In this study, a reliable drop/impact
simulation for a cellular phone is carried out using the explicit code LS-DYNA. Subsequently globallocal experimental verification
is accomplished by means of high-speed photography and impact response measurement. Using this methodology, we predict potential
damage locations in a cellular phone and compare them with real statistical data. It is envisaged that development of a reliable
methodology of drop/impact simulation will provide us with a powerful and efficient vehicle for improvement of the design
quality and reduction of the product development cycle. 相似文献