全文获取类型
收费全文 | 53737篇 |
免费 | 8249篇 |
国内免费 | 5960篇 |
专业分类
化学 | 37665篇 |
晶体学 | 549篇 |
力学 | 3667篇 |
综合类 | 514篇 |
数学 | 5968篇 |
物理学 | 19583篇 |
出版年
2024年 | 116篇 |
2023年 | 1028篇 |
2022年 | 1370篇 |
2021年 | 1660篇 |
2020年 | 2050篇 |
2019年 | 1912篇 |
2018年 | 1599篇 |
2017年 | 1435篇 |
2016年 | 2316篇 |
2015年 | 2188篇 |
2014年 | 2850篇 |
2013年 | 3631篇 |
2012年 | 4690篇 |
2011年 | 4899篇 |
2010年 | 3169篇 |
2009年 | 3075篇 |
2008年 | 3400篇 |
2007年 | 3086篇 |
2006年 | 2894篇 |
2005年 | 2500篇 |
2004年 | 1916篇 |
2003年 | 1609篇 |
2002年 | 1601篇 |
2001年 | 1285篇 |
2000年 | 1164篇 |
1999年 | 1262篇 |
1998年 | 1051篇 |
1997年 | 993篇 |
1996年 | 1126篇 |
1995年 | 898篇 |
1994年 | 853篇 |
1993年 | 676篇 |
1992年 | 655篇 |
1991年 | 560篇 |
1990年 | 450篇 |
1989年 | 380篇 |
1988年 | 302篇 |
1987年 | 224篇 |
1986年 | 221篇 |
1985年 | 183篇 |
1984年 | 132篇 |
1983年 | 105篇 |
1982年 | 64篇 |
1981年 | 58篇 |
1980年 | 33篇 |
1978年 | 27篇 |
1977年 | 30篇 |
1976年 | 27篇 |
1975年 | 33篇 |
1974年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Yun-Zhi Tang Shao-Song Qian Xi-Sen Wang Hong Zhao Xue-Feng Huang Yong-Hua Li Xing-Cai Jiao Ren-Gen Xiong Prof. Dr. 《无机化学与普通化学杂志》2004,630(11):1623-1626
The in situ hydrolysis of phthalyl-γ-glutaminyl-histidine with Cd(ClO4)2·6H2O in the presence of water and methanol affords a novel two-dimensional cadmium coordination polymer, a new phase, anhydrous cadmium(II) phthalate, ( 1 ). The structure was determined by single crystal X-ray diffraction. Crystal data: P21/c, a = 13.8168(14), b = 7.0351(7), c = 8.2054(8) Å, β = 105.540(2)°, V = 768.43(13) Å3, Z = 4, R1 = 0.0380, wR2 = 0.1111. 相似文献
93.
94.
ZHU Yabin ZHOU Yueliang LIU Zhen WANG Shufang CHEN Zhenghao U Huibin YANG Guozhen XlAO Ling Ren Hongtao JIAO Yulei Zheng Minghui 《中国科学G辑(英文版)》2004,47(2):165-172
The irreversibility field (Hirr) of Y-based superconductor is much higher than that of Bi-based superconductor. Y-based superconductor is capable of maintaining stable electrical currents in high magnetic field and electric field, so it is a better suited mate-rial for electric-current applications. Commonly, the Y-based tapes comprise a YBCO thick film deposited on a flexible substrate, typically with an intermediate buffer layer, and an overcoat of noble metal. In this process, the interm… 相似文献
95.
Hong-Xing Zheng Dao-Yin Yu 《International Journal of Infrared and Millimeter Waves》2005,26(9):1343-1353
In this paper, a very useful numerical technique has been developed for analyzing the transient characteristics of a planar-spiral inductor on-chip. A locally conformal technique and an alternating-direction implicit scheme are applied to the finite-difference time-domain method. A formulation for solving three dimensional Maxwell’s equations is proposed. Using the proposed method, various parameters of the planar-spiral inductors have been analyzed and an equivalent circuit, which includes frequency-independent circuit elements, has been introduced. Highly computational efficiency is implemented. Numerical results show excellent agreement with the measured data over a wide frequency range. 相似文献
96.
勿庸置疑,课堂只是学生腾飞的基地,社会才是学生飞翔的天空.如何架设课堂与社会之间的桥梁,使学生从理论走向实践,从空想走向实际,是每位教师必须思考的问题.就物理教学而言,实验是架设课堂和社会的桥梁之一.那就是通过物理实验来实现. 相似文献
97.
A fluorous osmium catalyst was firstly developed. It had been effectively used as recoverable and reusable catalyst in the dihydroxylation of olefins. 相似文献
98.
The lattice profile analyzes the intrinsic structure of pseudorandom number sequences with applications in Monte Carlo methods and cryptology. In this paper, using the discrete Fourier transform for periodic sequences and the relation between the lattice profile and the linear complexity, we give general formulas for the expected value, variance, and counting function of the lattice profile of periodic sequences with fixed period. Moreover, we determine in a more explicit form the expected value, variance, and counting function of the lattice profile of periodic sequences for special values of the period. 相似文献
99.
Tian-Xi ZhouGuan-Hu Bao Qin-Gao MaGuo-Wei Qin Chu-Tao CheYang Lv Cheng WangQi-Tai Zheng 《Tetrahedron letters》2003,44(1):135-137
Langduin C, a novel dimeric diterpenoid, was isolated from the roots of Euphorbia fischeriana and its structure was established by spectral data and single-crystal X-ray diffraction analysis. 相似文献
100.
Li Yingle Huang Jiying Gong Shuohong 《International Journal of Infrared and Millimeter Waves》2003,24(6):953-961
The dielectric constant for rain medium is investigated by utilizing the system identification method. The rain rate model and frequency model of permittivity in millimeter waves band for rain medium are presented. The results obtained with models are in very good agreement with references in calculating the attenuation of electromagnetic waves induced by rain, which Shows that the obtained models are valid and practicable. The cross-polar discrimination gotten with rain rate model is in agreement with references. 相似文献