全文获取类型
收费全文 | 1538篇 |
免费 | 148篇 |
国内免费 | 316篇 |
专业分类
化学 | 637篇 |
晶体学 | 10篇 |
力学 | 91篇 |
综合类 | 310篇 |
数学 | 480篇 |
物理学 | 474篇 |
出版年
2024年 | 10篇 |
2023年 | 43篇 |
2022年 | 54篇 |
2021年 | 40篇 |
2020年 | 14篇 |
2019年 | 50篇 |
2018年 | 46篇 |
2017年 | 19篇 |
2016年 | 40篇 |
2015年 | 35篇 |
2014年 | 83篇 |
2013年 | 63篇 |
2012年 | 117篇 |
2011年 | 154篇 |
2010年 | 114篇 |
2009年 | 85篇 |
2008年 | 92篇 |
2007年 | 86篇 |
2006年 | 73篇 |
2005年 | 62篇 |
2004年 | 68篇 |
2003年 | 61篇 |
2002年 | 61篇 |
2001年 | 47篇 |
2000年 | 52篇 |
1999年 | 23篇 |
1998年 | 13篇 |
1997年 | 23篇 |
1996年 | 24篇 |
1995年 | 27篇 |
1994年 | 24篇 |
1993年 | 4篇 |
1992年 | 22篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 21篇 |
1988年 | 22篇 |
1987年 | 12篇 |
1986年 | 22篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1963年 | 4篇 |
1959年 | 8篇 |
1958年 | 8篇 |
1957年 | 12篇 |
排序方式: 共有2002条查询结果,搜索用时 390 毫秒
191.
Chun-Chuan Liu · Feng-Ming Li · Ting-Wei Liang · Wen-Hu Huang P.O.Box School of Astronautics Harbin Institute of Technology Harbin China 《Acta Mechanica Sinica》2011,27(5):785-795
In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory (MPT) and classic plate theory (CPT).To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed. 相似文献
192.
Cheng-Kang Wu · Hai-Xing Wang · Xian Meng · Xi Chen · Wen-Xia PanInstitute of Mechanics Chinese Academy of Sciences Beijing China School of Astronautics Beijing University of Aeronautics Astronautics Beijing China Department of Engineering Mechanics Tsinghua University Beijing China 《Acta Mechanica Sinica》2011,27(2):152-163
The aerodynamic aspects of indirect thrust measurement by the impulse method have been studied both experimentally and numerically. The underlying basic aerodynamic principle is outlined, the phenomena in subsonic, supersonic and arc-heated jets are explored, and factors affecting the accuracy of the method are studied and discussed. Results show that the impulse method is reliable for indirect thrust measurement if certain basic requirements are met, and a simple guideline for its proper application is given. 相似文献
193.
Long-He Xu · Zhong-Xian Li · Jia-Ru Qian School of Civil Engineering Beijing Jiaotong University Beijing China School of Civil Engineering Tianjin University Tianjin China Department of Civil Engineering Tsinghua University Beijing China 《Acta Mechanica Sinica》2011,27(3):399-405
A two-stage damage detection approach is proposed and experimentally demonstrated on a complicated spatial model structure with a limited number of measurements. In the experiment,five known damage patterns,including 3 brace damage cases and 2 joint damage cases,were simulated by removing braces and weakening beam-column connections in the structure. The limited acceleration response data generated by hammer impact were used for system identification,and modal parameters were extracted by using the eigensystem realization algorithm. In the first stage,the possible damaged locations are determined by using the damage index and the characteristics of the analytical model itself,and the extent of damage for those substructures identified at stage I is estimated in the second stage by using a second-order eigen-sensitivity approximation method. The main contribution of this paper is to test the two-stage method by using the real dynamic data of a complicated spatial model structure with limited sensors. The analysis results indicate that the two-stage approach is ableto detect the location of both damage cases,only the severity of brace damage cases can be assessed,and the reasonable analytical model is critical for successful damage detection. 相似文献
194.
195.
证明对一切θ∈(0,1),θ(2(λμ)~(1/2)-λ-μ)都是偏微分方程形式的M/M/1排队模型主算子的几何重数为1的特征值. 相似文献
196.
对具有分布时滞的递归神经网络模型进行了研究,并通过构造适当的Lyapunov-Krasovskii函数和非线性控制函数,采用不等式估计方法,得到了所研究模型一般衰减同步的充分条件.最后给出了一个例子,进一步说明了所得结论的正确性. 相似文献
197.
717树脂吸附磺原酸钾吸附富集-原子吸收法测定天然水中的微量金属元素 总被引:1,自引:0,他引:1
用717氯型强硷性阴离子交换树脂和乙原磺酸钾一起加热,树脂吸附了磺原酸钾,树脂中含有二硫代羧酸基团,具有二硫代羧酸螯合树脂的一些特性。用静态法和柱法讨论了树脂对金属离子的吸附性能和解脱条件,共存离子对微量金属元素的干扰影响。用原子吸收法测定天然水中的微量铜、钴、镍、铅、镉、锰等元素,从回收率和精密度说明结果较满意。 相似文献
198.
极小超曲面上Laplace算子的谱 总被引:1,自引:0,他引:1
本文证明了单位球面S^n+1中某些Clifford超曲面,复射影空间和四元数射影空间中广YQ LIFFORDFHV MA DM J MH ADW H Laplace算子的谱唯一确定。 相似文献
199.
200.