全文获取类型
收费全文 | 11460篇 |
免费 | 2347篇 |
国内免费 | 2089篇 |
专业分类
化学 | 8862篇 |
晶体学 | 253篇 |
力学 | 739篇 |
综合类 | 173篇 |
数学 | 1545篇 |
物理学 | 4324篇 |
出版年
2024年 | 22篇 |
2023年 | 166篇 |
2022年 | 260篇 |
2021年 | 380篇 |
2020年 | 433篇 |
2019年 | 482篇 |
2018年 | 418篇 |
2017年 | 385篇 |
2016年 | 586篇 |
2015年 | 672篇 |
2014年 | 716篇 |
2013年 | 879篇 |
2012年 | 1002篇 |
2011年 | 1013篇 |
2010年 | 845篇 |
2009年 | 822篇 |
2008年 | 877篇 |
2007年 | 722篇 |
2006年 | 636篇 |
2005年 | 600篇 |
2004年 | 539篇 |
2003年 | 463篇 |
2002年 | 590篇 |
2001年 | 517篇 |
2000年 | 357篇 |
1999年 | 261篇 |
1998年 | 217篇 |
1997年 | 150篇 |
1996年 | 134篇 |
1995年 | 119篇 |
1994年 | 99篇 |
1993年 | 86篇 |
1992年 | 80篇 |
1991年 | 68篇 |
1990年 | 50篇 |
1989年 | 43篇 |
1988年 | 30篇 |
1987年 | 27篇 |
1986年 | 19篇 |
1985年 | 14篇 |
1984年 | 19篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
根据密度泛函理论对钴掺硫化锌周围的品格进行了结构优化,计算得到了钴杂质周围的晶体结构、电子态密度分布和吸收光谱.计算结果表明,由于Co原子掺入ZnS晶格常数减小,导致晶格畸变;带隙变窄;吸收峰展宽至更长波长区域. 相似文献
92.
Based on the anisotropic Seebeck tensor coefficients, a light-thermo-radiation detector made of high-Tc superconductor (YBa2Cu3O7-δ) was fabricated, which can function at room temperature. The induced voltaic signals at various modulation frequencies for radiation from He-Ne laser and from a 500 K black body were measured. The noise ratio for detecting He-Ne laser radiation and the D* for black body were evaluated. Compared with bolometer made of high-Tc superconductor which functions at liquid nitrogen, and with pyroelectric detector, it was found that the advantages of this new device are that the device can work at room temperature with very low noise and very fast response. Although having a lower D* value than that of bolometer for the present device construction, we point out the possibility and the direction for improving the D* value, hence the promising prospect of this kind of device. 相似文献
93.
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
94.
Three novel zinc complexes [Zn(dbsf)(H2O)2] ( 1 ), [Zn(dbsf)(2,2′‐bpy)(H2O)]·(i‐C3H7OH) ( 2 ) and [Zn(dbsf)(DMF)] ( 3 ) (H2dbsf = 4,4′‐dicarboxybiphenyl sulfone, 2,2′‐bpy = 2,2′‐bipyridine, i‐C3H7OH = iso‐propanol, DMF = N,N‐dimethylformamide) were first obtained and characterized by single crystal X‐ray crystallography. Although the results show that all the complexes 1–3 have one‐dimensional chains formed via coordination bonds, unique three‐dimensional supramolecular structures are formed due to different coordination modes and configuration of the dbsf2? ligand, hydrogen bonds and π–π interactions. Iso‐propanol molecules are in open channels of 2 while larger empty channels are formed in 3 . As compared with emission band of the free H2dbsf ligand, emission peaks of the complexes 1–3 are red‐shifted, and they show blue emission, which originates from enlarging conjugation upon coordination. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
95.
FANG Qi LEI Hong CUI Yuezhi HUANG Zhenli XUE Gang & YU Wentao . State Key Laboratory of Crystal Materials Shandong University Jinan China . School of Information Science Engineering Shandong University Jinan China . Department of Chemical Engineering Light Industry College of Shandong Jinan China . Key Laboratory of Biomedical Photonics Ministry of Education Huazhong University of Science Technology Wuhan China 《中国科学B辑(英文版)》2005,48(3)
Organic nonlinear optics (NLO) is also called mo-lecular nonlinear optics. In recent years organic mate-rials have been intensively studied because of their large NLO coefficients and structural diversities[1―3]. Second harmonic generation (SHG) is a bas… 相似文献
96.
98.
Guilin Wen Qing-Guo Wang Chong Lin Xu Han Guangyao Li 《Chaos, solitons, and fractals》2006,29(5):1142-1146
Synchronization under output feedback control with multiple random time delays is studied, using the paradigm in nonlinear physics—Chua’s circuit. Compared with other synchronization control methods, output feedback control with multiple random delay is superior for a realistic synchronization application to secure communications. Sufficient condition for global stability of delay-dependent synchronization is established based on the LMI technique. Numerical simulations fully support the analytical approach, in spite of the random delays. 相似文献
99.
By introducing the conception "relativistic differential Galois group" for the second order polynomial systems, we establish the relation between the conformal relativistic differential Galois group and the subgroup of M(o)bius transformations, and prove that the system is integrable in the sense of Liouville if its conformal relativistic differential Galois group is solvable with a derived length at most 2. Some omissions on the structures of solvable subgroups of M(o)bius transformations at the first author's article published in this journal in 1996 are refreshed in this paper. 相似文献
100.
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