全文获取类型
收费全文 | 2488篇 |
免费 | 317篇 |
国内免费 | 192篇 |
专业分类
化学 | 1199篇 |
晶体学 | 10篇 |
力学 | 881篇 |
综合类 | 13篇 |
数学 | 194篇 |
物理学 | 700篇 |
出版年
2023年 | 22篇 |
2022年 | 56篇 |
2021年 | 36篇 |
2020年 | 94篇 |
2019年 | 68篇 |
2018年 | 89篇 |
2017年 | 84篇 |
2016年 | 130篇 |
2015年 | 97篇 |
2014年 | 130篇 |
2013年 | 177篇 |
2012年 | 119篇 |
2011年 | 144篇 |
2010年 | 127篇 |
2009年 | 147篇 |
2008年 | 151篇 |
2007年 | 145篇 |
2006年 | 146篇 |
2005年 | 136篇 |
2004年 | 111篇 |
2003年 | 102篇 |
2002年 | 93篇 |
2001年 | 68篇 |
2000年 | 55篇 |
1999年 | 46篇 |
1998年 | 61篇 |
1997年 | 44篇 |
1996年 | 36篇 |
1995年 | 47篇 |
1994年 | 40篇 |
1993年 | 24篇 |
1992年 | 45篇 |
1991年 | 29篇 |
1990年 | 28篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有2997条查询结果,搜索用时 15 毫秒
131.
132.
This is one of the applications of Part (I), in which the angular stiffness, and the corresponding stress distributions of U-shaped bellows were discussed. The bellows
was divided into protruding sections, concave sections and ring plates for the calculation that the general solution (I) with its reduced form to ring plates were used respectively, but the continuity of the surface stresses and the meridian
rotations at each joint of the sections were entirely satisfied. The resent results were compared with those of the slender
ring shell solution proposed earlier by the authors, the standards of the Expansion Joint Manufacturers Association (EJMA),
the experiment and the finite element method. It is shown that the governing equation and the general solution (I) are very effective.
Contributed by HUANG Qian
Biography: ZHU Wei-ping (1962-) 相似文献
133.
从Donnell圆柱壳方程出发,利用复变函数与保角映射的方法,将圆柱壳展开面上的开孔边界线保角晨射成单位圆,并在映射平面上给出了逼近大开孔圆柱壳方程解答的完备函数逼近序列,进而利用边界条件和正交函数展开的方法得到了自由孔边应力集中系数的表达式,最后,对具有开孔率的圆柱壳在不同荷载条件下的自由孔口边界上的应力集中的系数进行了计算,此种方法,同时研究圆柱壳开非圆大孔和接管等问题提供了可能性。 相似文献
134.
135.
Shu-Xian Gu 《Acta Mechanica Solida Sinica》1988,1(4):369-381
In this paper, we treat the nonlinear stability problem of shallow spherical shells with large values ofk(k=12(1–v) · 2f/h,f = shell rise,h = shell thickness) under the action of uniformly distributed line load along a circle concentric with the shell boundary. Load-deflection curves are computed at successive increments of uniformly distributed line loads by using both cubic B-spline approximations and iterative techniques. Our algorithm yields fairly good convergent results for values ofk as large as 400. The limiting case in which shells are loaded along a circle of small radius has been specially investigated and the computed critical loads are compared with those obtained with central point loads by other authors. 相似文献
136.
Erzsébet Oláh Szabolcs Fekete Jenő Fekete Katalin Ganzler 《Journal of chromatography. A》2010,1217(23):3642-3653
Today sub-2 μm packed columns are very popular to conduct fast chromatographic separations. The mass-transfer resistance depends on the particle size but some practical limits exist not to reach the theoretically expected plate height and mass-transfer resistance. Another approach applies particles with shortened diffusion path to enhance the efficiency of separations. In this study a systematical evaluation of the possibilities of the separations obtained with 5 cm long narrow bore columns packed with new 2.6 μm shell particles (1.9 μm nonporous core surrounded by a 0.35 μm porous shell, Kinetex™, Core-Shell), packed with other shell-type particles (Ascentis Express™, Fused-Core), totally porous sub-2 μm particles and a 5 cm long narrow bore monolith column is presented. The different commercially available columns were compared by using van Deemter, Knox and kinetic plots. Theoretical Poppe plots were constructed for each column to compare their kinetic performance. Data are presented on polar neutral real-life analytes. Comparison of a low molecular weight compounds (MW = 270–430) and a high molecular weight one (MW ∼ 900) was conducted. This study proves that the Kinetex column packed with 2.6 μm shell particles is worthy of rivaling to sub-2 μm columns and other commercially available shell-type packings (Ascentis Express or Halo), both for small and large molecule separation. The Kinetex column offers a very flat C term. Utilizing this feature, high flow rates can be applied to accomplish very fast separations without significant loss in efficiency. 相似文献
137.
138.
139.
The Gamow-Teller transitions for pf shell nuclei with proton number less than 40 and neutron number larger than 40 were believed to be blocked, due to the full filling of the neutron orbit. However, recent experimental research shows that the Gamow-Teller transitions for these kinds of nuclei are not blocked. In this paper, we systematically calculate the GT transition of pf shell nuclei 76Se in different truncations, and the results are compared with experimental results. It is shown that, due to correlations, the believed blocked GT transition occurs, and the shell model calculations reproduce the experimental GT strength. In addition, the electron capture rates in a stellar environment are calculated and discussed. 相似文献
140.
Tomohiro Suetsuna Seiichi SuenagaShinya Sakurada Koichi HaradaMaki Tomimatsu Toshihide Takahashi 《Journal of magnetism and magnetic materials》2011,323(13):1793-1798
Self-forming core/shell nanoparticles of magnetic metal/oxide with crystalline grain size of less than 40 nm were synthesized. The nanoparticles were highly concentrated in an insulating matrix to fabricate a nanocomposite, whose magnetic properties were investigated. The crystalline grain size of the nanoparticles strongly influenced the magnetic anisotropy field, magnetic coercivity, relative permeability, and loss factor (tan δ=μ″/μ′) at high frequency. The packing ratio of the magnetic metallic phase in the nanocomposite also influenced those properties. High permeability with low tan δ of less than 1.5% at up to 1 GHz was obtained in the case of the nanoparticles with crystalline grain size of around 15 nm with large packing ratio of the nanoparticles. 相似文献