全文获取类型
收费全文 | 27768篇 |
免费 | 912篇 |
国内免费 | 171篇 |
专业分类
化学 | 18479篇 |
晶体学 | 282篇 |
力学 | 795篇 |
综合类 | 1篇 |
数学 | 2596篇 |
物理学 | 6698篇 |
出版年
2023年 | 166篇 |
2022年 | 454篇 |
2021年 | 640篇 |
2020年 | 492篇 |
2019年 | 522篇 |
2018年 | 451篇 |
2017年 | 408篇 |
2016年 | 804篇 |
2015年 | 694篇 |
2014年 | 956篇 |
2013年 | 1642篇 |
2012年 | 1966篇 |
2011年 | 2226篇 |
2010年 | 1427篇 |
2009年 | 1220篇 |
2008年 | 1870篇 |
2007年 | 1612篇 |
2006年 | 1660篇 |
2005年 | 1405篇 |
2004年 | 1237篇 |
2003年 | 1052篇 |
2002年 | 990篇 |
2001年 | 627篇 |
2000年 | 561篇 |
1999年 | 381篇 |
1998年 | 242篇 |
1997年 | 245篇 |
1996年 | 324篇 |
1995年 | 222篇 |
1994年 | 230篇 |
1993年 | 252篇 |
1992年 | 195篇 |
1991年 | 159篇 |
1990年 | 157篇 |
1989年 | 132篇 |
1988年 | 95篇 |
1987年 | 97篇 |
1986年 | 79篇 |
1985年 | 101篇 |
1984年 | 68篇 |
1983年 | 57篇 |
1982年 | 79篇 |
1981年 | 86篇 |
1980年 | 47篇 |
1979年 | 64篇 |
1978年 | 56篇 |
1977年 | 52篇 |
1976年 | 60篇 |
1975年 | 48篇 |
1974年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Seok-Soo Yoon N.A. Buznikov Lan Jin Chong-Oh Kim CheolGi Kim 《Journal of magnetism and magnetic materials》2006
The off-diagonal magnetoimpedance in field-annealed CoFeSiB amorphous ribbons was measured using a pick-up coil wound around the sample. One side of a ribbon was etched in hydrofluoric acid solution during various times in order to change the thickness of the surface crystalline layer appearing after annealing. The asymmetric two-peak field dependence of the off-diagonal impedance was observed for all samples. The evolution of the off-diagonal magnetoimpedance with the change in the ribbon thickness is analyzed. 相似文献
62.
S. S. Dragomir Y. J. Cho S. S. Kim J. Roumeliotis 《Journal of Applied Mathematics and Computing》2006,20(1-2):279-292
A reverse of Bessel’s inequality in 2-inner product spaces and companions of Grüss inequality with applications for determinantal integral inequalities are given. 相似文献
63.
64.
65.
We investigated that the effect of the number of segregated Li atoms on the rate of oxidation on a LiAl alloy surface. Oxygen molecules adsorbed on the LiAl alloy react with the surface atoms to form stable oxides. The segregated Li atoms at reconstructed surfaces (c(2×2) and (2×1)) enhance the oxidation rate and form stable LiAlOx and Li2O. The degree of enhancement of oxidation by segregated Li atoms varies as a function of O2 exposure and annealing temperature, where the latter is directly related to the mode of surface reconstruction by Li segregation. 相似文献
66.
Kyung Hwa Hong Jong Lyoul Park In Hwan Sul Ji Ho Youk Tae Jin Kang 《Journal of Polymer Science.Polymer Physics》2006,44(17):2468-2474
Polyvinyl alcohol (PVA) nanofibers containing Ag nanoparticles were prepared by electrospinning PVA/silver nitrate (AgNO3) aqueous solutions, followed by short heat treatment, and their antimicrobial activity was investigated for wound dressing applications. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for the preparation of wound dressing nanofibers. After heat treatment at 155 °C for 3 min, the PVA/AgNO3 nanofibers became insoluble, while the Ag+ ions therein were reduced so as to produce a large number of Ag nanoparticles situated preferentially on their surface. The residual Ag+ ions were reduced by subsequent UV irradiation for 3 h. The average diameter of the Ag nanoparticles after the heat treatment was 5.9 nm and this value increased slightly to 6.3 nm after UV irradiation. It was found that most of the Ag+ ions were reduced by the simple heat treatment. The PVA nanofibers containing Ag nanoparticles showed very strong antimicrobial activity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2468–2474, 2006 相似文献
67.
This paper presents the development and laboratory evaluation of a PM10/2.5/1.0 trichotomous sampling inlet that consists of two main parts: a previously designed PM10 size‐selective inlet part and a PM2.5/1.0 two‐stage virtual impactor, which was newly fabricated and attached serially to the PM10 size selective inlet part. Particles are collected in three locations through the trichotomous sampling inlet to provide for not only particle concentration measurements of PM10, PM2.5 and PM1.0, but also those of PM2.5–10 and PM1.0–2.5. 相似文献
68.
Diem Ho 《Numerische Mathematik》1989,56(7):721-734
Summary The acceleration by Tchebychev iteration for solving nonsymmetric eigenvalue problems is dicussed. A simple algorithm is derived to obtain the optimal ellipse which passes through two eigenvalues in a complex plane relative to a reference complex eigenvalue. New criteria are established to identify the optimal ellipse of the eigenspectrum. The algorithm is fast, reliable and does not require a search for all possible ellipses which enclose the spectrum. The procedure is applicable to nonsymmetric linear systems as well. 相似文献
69.
H-J Kim D-H Lee P Xirouchakis 《The Journal of the Operational Research Society》2006,57(10):1231-1240
This paper considers the problem of determining the disassembly schedule (quantity and timing) of products in order to satisfy the demand of their parts or components over a finite planning horizon. The objective is to minimize the sum of set-up, disassembly operation, and inventory holding costs. As an extension of the uncapacitated versions of the problem, we consider the resource capacity restrictions over the planning horizon. An integer program is suggested to describe the problem mathematically, and to solve the problem, a heuristic is developed using a Lagrangean relaxation technique together with a method to find a good feasible solution while considering the trade-offs among different costs. The effectiveness of the algorithm is tested on a number of randomly generated problems and the test results show that the heuristic suggested in this paper can give near optimal solutions within a short amount of computation time. 相似文献
70.
For the methylsilsesquioxane film whose optical birefringence is almost zero, it was recently reported that its vertical thermal expansion coefficient (CTE) was approximately one order of magnitude larger than the lateral CTE. Though the birefringence is not an absolute predictor of anisotropic behavior, the discrepancy in both the CTEs was so remarkable that it was essential to investigate whether the anisotropy was intrinsic property or not. If the effect of Poisson's ratio is considered in the calculation of the vertical CTE and when elastic modulus measured by surface acoustic wave spectroscopy is used in the assessment of the lateral CTE, both the CTEs are coincident with each other. Therefore, it can be concluded that the discrepancy in the CTEs can be attributed to a higher in‐plane polymer chain orientation but it can also arise from the misleadingly assumed modulus and Poisson's ratio. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3109–3120, 2006 相似文献