全文获取类型
收费全文 | 124185篇 |
免费 | 9584篇 |
国内免费 | 7724篇 |
专业分类
化学 | 41622篇 |
晶体学 | 1940篇 |
力学 | 5727篇 |
综合类 | 1215篇 |
数学 | 39780篇 |
物理学 | 51209篇 |
出版年
2023年 | 527篇 |
2022年 | 690篇 |
2021年 | 1978篇 |
2020年 | 1607篇 |
2019年 | 1941篇 |
2018年 | 1811篇 |
2017年 | 1608篇 |
2016年 | 1662篇 |
2015年 | 1581篇 |
2014年 | 2903篇 |
2013年 | 5016篇 |
2012年 | 3174篇 |
2011年 | 4011篇 |
2010年 | 4441篇 |
2009年 | 9463篇 |
2008年 | 10580篇 |
2007年 | 9086篇 |
2006年 | 7989篇 |
2005年 | 5619篇 |
2004年 | 5347篇 |
2003年 | 5408篇 |
2002年 | 8437篇 |
2001年 | 4982篇 |
2000年 | 4578篇 |
1999年 | 4202篇 |
1998年 | 3611篇 |
1997年 | 2622篇 |
1996年 | 2385篇 |
1995年 | 2741篇 |
1994年 | 2626篇 |
1993年 | 2145篇 |
1992年 | 1652篇 |
1991年 | 1201篇 |
1990年 | 981篇 |
1989年 | 844篇 |
1988年 | 818篇 |
1987年 | 618篇 |
1986年 | 427篇 |
1985年 | 1292篇 |
1984年 | 880篇 |
1983年 | 637篇 |
1982年 | 915篇 |
1981年 | 1071篇 |
1980年 | 967篇 |
1979年 | 847篇 |
1978年 | 758篇 |
1977年 | 655篇 |
1976年 | 630篇 |
1974年 | 382篇 |
1973年 | 517篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
41.
42.
Umie F.M. Haziz Rosenani A. Haque Shun-Ze Zhan Hassan H. Abdallah Mohd R. Razali 《应用有机金属化学》2020,34(10):e5818
The synthesis and characterizations for a series of dinuclear gold (I)-di-NHC complexes, 1–8 through the trans-metalation method of their respective silver (I)-di-NHC complexes, i–viii are reported (where NHC = N-heterocyclic carbene). The successful complexation of a series of unusual non-symmetrical and symmetrical di-NHC ligands, 3,3'-(ethane-1,2-diyl)-1-alkylbenzimidazolium-1'-butylbenzimidazolium (with alkyl = methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, benzyl) with the gold (I) ions are suggested by elemental analysis, Fourier transform-infrared, 1H- and 13C-NMR data. The 13C-NMR spectra of 1–8 show a singlet sharp peak in the range of 190.00–192.00 ppm, indicating the presence of a carbene carbon that bonded to the gold (I) ion. From single crystal X-ray diffraction data, the structure of complex 6 with the formula of [di-NHC-Au (I)]2·2PF6 is obtained [where NHC = 3,3'-(ethane-1,2-diyl)-1-hexylbenzimidazolium-1'-butylbenzimidazolium]. The photophysical study in solid state of 6 displays an intense photoluminescence with a strong emission maxima, λem = 480 nm, upon excitation at 340 nm at room temperature. Interestingly, the emission maximum at 77 K shows a structural character with a strong peak at 410 nm, a medium at 433 nm and a weak at 387 nm, accompanied by a tail band to about 500 nm. 相似文献
43.
We theoretically study complementarity between micro-micro and micro-macro entanglement in a Bose–Einstein condensate with two Rydberg impurities. We investigate quantum dynamics of micro-micro and micro-macro entanglement in the micro-macro system. It is found that strong micro-macro entanglement between Rydberg impurities and the BEC can be generated by the use of initial micro-micro entanglement between two Rydberg impurities, which acts as the seed entanglement to create micro-macro entanglement. We demonstrate a curious complementarity relation between micro-micro and micro-macro entanglement, and find that the complementarity property can be sustained to some extent even though in the presence of the BEC decoherence. 相似文献
44.
文[1]提出了两个DEA的逆问题,并用搜索法来解.而本文根据所证的定理,对每个问题一般只要解二、三个线性规划问题就能得到答案. 相似文献
45.
In this work, the variation of the magnetic moments of the Ni/Pt multilayers are studied using the linearized augmented plane waves (LAPW) method in the framework of the density functional theory (DFT) implemented in the version of WIEN2K program. The systems have been modeled by seven layers slab separated in z direction by a vacuum region of four substrate layers. We present the results of the dependence of the magnetic properties with respect to the thickness variation of the different multilayers. The modeling of these systems finds an important empirical support. Experiment and theory show the same trends for the magnetic moments: hybridization effects between Ni and Pt are mostly localized at the interface. 相似文献
46.
Single-crystalline gallium nitride nanobelts have been synthesized through the reaction of gallium vapor with flowing ammonia using nickel as a catalyst. The as-synthesized products were characterized using X-ray powder diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected-area electron diffraction (SAED). XRD and SAED results revealed that the products are pure, single-crystalline GaN with hexagonal structure. The widths and thickness of the nanobelts ranged from 80 to 200 nm, and 10 to 30 nm, respectively. The lengths were up to several tens of micrometers. The nanobelts had smooth surface with no amorphous sheath, and a sharp-tip end. The growth mechanism of nanobelts was discussed. 相似文献
47.
49.
Inner derivations and norm equality 总被引:3,自引:0,他引:3
Mohamed Barraa Mohamed Boumazgour 《Proceedings of the American Mathematical Society》2002,130(2):471-476
We characterize when the norm of the sum of two bounded operators on a Hilbert space is equal to the sum of their norms.
50.
本文证明了Heisenberg群上Laplace算子的Dirichlet特征值的存在性,给出了特征值的估计 相似文献