全文获取类型
收费全文 | 10922篇 |
免费 | 1666篇 |
国内免费 | 1924篇 |
专业分类
化学 | 9209篇 |
晶体学 | 169篇 |
力学 | 513篇 |
综合类 | 121篇 |
数学 | 1291篇 |
物理学 | 3209篇 |
出版年
2024年 | 18篇 |
2023年 | 120篇 |
2022年 | 358篇 |
2021年 | 313篇 |
2020年 | 361篇 |
2019年 | 461篇 |
2018年 | 367篇 |
2017年 | 369篇 |
2016年 | 515篇 |
2015年 | 619篇 |
2014年 | 689篇 |
2013年 | 864篇 |
2012年 | 1032篇 |
2011年 | 997篇 |
2010年 | 736篇 |
2009年 | 750篇 |
2008年 | 847篇 |
2007年 | 721篇 |
2006年 | 640篇 |
2005年 | 614篇 |
2004年 | 531篇 |
2003年 | 390篇 |
2002年 | 444篇 |
2001年 | 371篇 |
2000年 | 276篇 |
1999年 | 188篇 |
1998年 | 165篇 |
1997年 | 128篇 |
1996年 | 103篇 |
1995年 | 75篇 |
1994年 | 89篇 |
1993年 | 55篇 |
1992年 | 54篇 |
1991年 | 48篇 |
1990年 | 52篇 |
1989年 | 28篇 |
1988年 | 34篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1977年 | 3篇 |
1959年 | 2篇 |
1939年 | 1篇 |
1936年 | 7篇 |
1935年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
界面应力的正确评价是分析薄膜涂层材料力学特性的难题之一。利用镜像点法和Dirichlet等值性原理,本文推导了等厚双层薄膜涂层材料受表面集中力作用的平面问题理论解。该显式理论解是以固定在各镜像点上的局部坐标系下的Goursat应力函数的形式给出的。对应于高阶镜像点的应力函数,可通过递推的方法,从对应于低阶镜像点的应力函数求得,而且也易于计算机编程。随着镜像点阶数的增大,它与界面的距离也越来越大,因而相对应的应力函数对界面应力的影响越来越小。最后的算例表明,只需考虑前面有限个镜像点,便可获得足够精度的解。该理论解可作为格林函数,以求解复杂问题的理论解,也可用作边界元法的基本解,提高数值计算的精度和效率。 相似文献
33.
Chongyi Wan Shiming Liu Rongqing Tan Jin Wu Jinwen Zhou Yan Lv Yanning Yu Hua Yang 《Optics & Laser Technology》2004,36(8):2389-649
A high average power, high-repetition-rate TEA CO2 laser employing printed-circuit-board preionizer is described. The power scaling of this preionization configuration has been demonstrated. The average output power reaches 3.6 kW at pulse repetition rate of 180 pps. Furthermore, the scaling-up ability of the rotating spark gap as high-voltage switch for high-average-power gas laser has been validated. 相似文献
34.
35.
36.
The electronic structure and magnetism of SmCo7-xZrx alloy are investigated using the spin-polarized MS-X. method. The results show that a few of electrons are transferred to the Sm(5d0) orbital due to orbital hybridization between Sm and Co atoms. The exchange interactions between 3d and 5d electrons are more important than the polarization effects of the conductive electrons, thus it is the main reason resulting in the long-range ferromagnetic order in SmCo7-xZrx. The Curie temperature of SmCo7-xZrx is generally lower than that of corresponding pure Co, which may be explained by the weaker average coupling strength between Co lattices due to some negative couplings mainly occurring of 2e site. The calculated results for the Sm5Co32Zr2 cluster may lead to a better understanding of why SmCo7-xZrx is stable phase. Since the spin-up DOS peak of d electrons at EF arises and the bonding of electrons at EF strengthens with increasing Zr concentration, which results in the internal energy of the system decrease, the stable ferromagnetic order forms in SmCo7-xZrx. 相似文献
37.
Hua Ning LIU Wen Peng ZHANG 《数学学报(英文版)》2007,23(5):915-924
The main purpose of this paper is to use the generalized Bernoulli numbers, Gauss sums and the mean value theorems of Dirichlet L-functions between a quadratic residue and its inverse modulo p value formula. to study the asymptotic property of the difference (a prime), and to give an interesting hybrid mean 相似文献
38.
39.
40.
Measurement of small-signal and large-signal responses of packaged laser modules at high temperature
Ning Hua Zhu Ji Min Wen Hai Peng Song Shang Jian Zhang Liang Xie 《Optical and Quantum Electronics》2006,38(15):1245-1257
In this paper, the pulsed injection method is extended to measure the chip temperature of various packaged laser modules,
such as the DFB laser modules, the FP laser modules, and the EML laser modules. An optimal injection condition is obtained
by investigating the dependence of the lasing wavelength on the width and period of the injection pulse in a relatively wide
temperature range. The small-signal frequency responses and large-signal performances of packaged laser modules at different
chip temperature are measured. The adiabatic small-signal modulation characteristics of packaged LD are first extracted. In
the large-signal measurement, the effects of chip temperature, bias current and driving signal on the performances of the
laser modules are discussed. It has been found that the large-signal performances of the EML modules depend on the different
red-shift speeds of the DFB and EAM sections as chip temperature varying, and the optimal characteristics may be achieved
at higher temperature. 相似文献