全文获取类型
收费全文 | 1523篇 |
免费 | 157篇 |
国内免费 | 85篇 |
专业分类
化学 | 520篇 |
晶体学 | 4篇 |
力学 | 243篇 |
综合类 | 49篇 |
数学 | 452篇 |
物理学 | 497篇 |
出版年
2024年 | 4篇 |
2023年 | 21篇 |
2022年 | 57篇 |
2021年 | 51篇 |
2020年 | 48篇 |
2019年 | 46篇 |
2018年 | 39篇 |
2017年 | 45篇 |
2016年 | 77篇 |
2015年 | 44篇 |
2014年 | 69篇 |
2013年 | 129篇 |
2012年 | 64篇 |
2011年 | 95篇 |
2010年 | 77篇 |
2009年 | 92篇 |
2008年 | 84篇 |
2007年 | 88篇 |
2006年 | 56篇 |
2005年 | 84篇 |
2004年 | 55篇 |
2003年 | 51篇 |
2002年 | 57篇 |
2001年 | 50篇 |
2000年 | 42篇 |
1999年 | 31篇 |
1998年 | 20篇 |
1997年 | 19篇 |
1996年 | 27篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有1765条查询结果,搜索用时 31 毫秒
161.
162.
We demonstrate the ability to determine stress intensity factors in orthotropic materials directly from measured temperatures
away from the crack and using far-field expressions for the stresses. This is advantageous, recognizing that recorded thermoelastic
data can be very unreliable near the tip of a crack. In addition to singular terms that govern in the immediate vicinity of
the crack tip, the present series expressions for the stresses contain higher-order finite terms. Little measured input information
is needed and data acquisition positions can be selected largely at the user's discretion. 相似文献
163.
压荷载下类岩石材料中的锯齿形裂纹分析 总被引:8,自引:0,他引:8
针对类岩石材料的复杂性和非均质性,特别是材料中一些强度相对较弱的晶界的存在等,对形状较为复杂的两种锯齿形裂纹:内张型滑动裂纹和单翼滑动裂纹的应力强度因子进行了分析.结合经典的滑动裂纹模型,讨论了裂纹起裂角、侧压以及翼裂长度等对应力强度因子的影响.分析的结果为进一步研究类岩石材料的断裂损伤机理提供了理论基础. 相似文献
164.
压-剪复合应力波作用下材料动态断裂韧性研究 总被引:2,自引:0,他引:2
提出亚微秒单脉冲应力波载荷作用下Ⅱ型裂纹的平板冲击实验技术 .加载率为dK dt~ 10 8MPa·m1 2 ·s-1.实验中由锰铜应力片和弹性波理论分别测定和计算了压应力 ;通过微观分析确定了动态裂纹的平均扩展长度 ;引进等效应力强度因子 ,用动态断裂理论确定了 6 0 #钢的动态断裂韧性KⅠd和KⅡd ;建立了亚微秒冲击载荷作用下确定材料动态断裂韧性的方法 相似文献
165.
166.
167.
板结构功率流的参数研究 总被引:1,自引:0,他引:1
板以及肋板结构在工程中有着广泛的应用,其振动嗓声问题一直受到理论和工程领域的关注。本文在板结构功率流理论的基础上 ̄[1],对板的损耗因子和不同加肋形式对其功率流的影响进行了分析和测量。 相似文献
168.
A full field solution, based on small deformation, three-dimensional elastic–plastic finite element analysis of the centrally cracked thin disk under mode I loading has been performed. The solution for the stresses under small-scale yielding and lo!cally fully plastic state has been compared with the HRR plane stress solution. At the outside of the 3D zone, within a distance of rσo/J=18, HRR dominance is maintained in the presence of a significant amount of compressive stress along the crack flanks. Ahead of this region, the HRR field overestimate the stresses. These results demonstrate a completely reversed state of stress in the near crack front compared to that in the plane strain case. The combined effect of geometry and finite thickness of the specimen on elastic–plastic crack tip stress field has been explored. To the best of our knowledge, such an attempt in the published literature has not been made yet. For the qualitative assessment of the results some of the field parameters have been compared to the available experimental results of K, gives a fair estimate of the crack opening stress near the crack front at a distance of order 10−2 in. On the basis of this analysis, the Linear Elastic Fracture Mechanics approach has been adopted in analyzing the fatigue crack extension experiments performed in the disk (Part II). 相似文献
169.
The interaction of a screw dislocation with an interfacial edge crack in a two-phase piezoelectric medium is investigated.
Closed-form solutions of the elastic and electrical fields induced by the screw dislocation are derived using the conformal
mapping method in conjunction with the image principle. Based on the electroelastic fields derived, the stress and electric
displacement intensity factors, the image force acting on the dislocation are given explicitly. We find that the stress and
electric displacement intensity factors depend on the effective electroelastic material constants. In the case where one of
two phases is purely elastic, the stress intensity factor and image force are plotted to illustrate the influences of electromechanical
coupling effect, the position of the dislocation and the material properties on the interaction mechanism.
The project supported by the Doctoral Foundation of Hebei Province (B2003113) 相似文献
170.
Xiaoyu Jia Yi Han Xinli Liu Taicheng Duan Hangting Chen 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(1):88-92
The dispersive liquid-liquid microextraction (DLLME) combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry for the speciation of mercury in water samples was described. Firstly methylmercury (MeHg+) and mercury (Hg2+) were complexed with sodium diethyldithiocarbamate, and then the complexes were extracted into carbon tetrachloride by using DLLME. Under the optimized conditions, the enrichment factors of 138 and 350 for MeHg+ and Hg2+ were obtained from only 5.00 mL sample solution. The detection limits of the analytes (as Hg) were 0.0076 ng mL−1 for MeHg+ and 0.0014 ng mL−1 for Hg2+, respectively. The relative standard deviations for ten replicate measurements of 0.5 ng mL−1 MeHg+ and Hg2+ were 6.9% and 4.4%, respectively. Standard reference material of seawater (GBW(E)080042) was analyzed to verify the accuracy of the method and the results were in good agreement with the certified values. Finally, the developed method was successfully applied for the speciation of mercury in three environmental water samples. 相似文献