全文获取类型
收费全文 | 79185篇 |
免费 | 6407篇 |
国内免费 | 4997篇 |
专业分类
化学 | 24280篇 |
晶体学 | 1811篇 |
力学 | 3503篇 |
综合类 | 314篇 |
数学 | 17522篇 |
物理学 | 43159篇 |
出版年
2022年 | 242篇 |
2021年 | 326篇 |
2020年 | 611篇 |
2019年 | 915篇 |
2018年 | 869篇 |
2017年 | 571篇 |
2016年 | 419篇 |
2015年 | 390篇 |
2014年 | 1033篇 |
2013年 | 1592篇 |
2012年 | 1132篇 |
2011年 | 1674篇 |
2010年 | 2277篇 |
2009年 | 6780篇 |
2008年 | 7847篇 |
2007年 | 6306篇 |
2006年 | 5764篇 |
2005年 | 3918篇 |
2004年 | 3743篇 |
2003年 | 3953篇 |
2002年 | 5185篇 |
2001年 | 3715篇 |
2000年 | 3480篇 |
1999年 | 3323篇 |
1998年 | 2734篇 |
1997年 | 1892篇 |
1996年 | 1716篇 |
1995年 | 2194篇 |
1994年 | 2135篇 |
1993年 | 1590篇 |
1992年 | 1104篇 |
1991年 | 826篇 |
1990年 | 677篇 |
1989年 | 604篇 |
1988年 | 565篇 |
1987年 | 403篇 |
1986年 | 191篇 |
1985年 | 943篇 |
1984年 | 615篇 |
1983年 | 487篇 |
1982年 | 639篇 |
1981年 | 794篇 |
1980年 | 721篇 |
1979年 | 559篇 |
1978年 | 581篇 |
1977年 | 538篇 |
1976年 | 540篇 |
1975年 | 319篇 |
1974年 | 356篇 |
1973年 | 462篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
LI Wangliang XING Jianmin XIONG Xiaochao SHAN Guobin & LIU Huizhou . Laboratory of Separation Science Engineering Institute of Process Engineering Chinese Academy of Sciences Beijing China . Graduate School of the Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2005,(6)
More and more stringent regulations of gasoline and diesel oil were proposed with the awareness of environmental protection. Hydrodesulfurization (HDS) is a conventional method to remove sulfur compounds for industrial purpose. The main drawbacks of this … 相似文献
992.
Three-dimensional (3-D) ZnO random-wall nanostructures and one-dimensional (1-D) ZnO nanorods were prepared on silicon substrates by a simple solid-vapour phase thermal sublimation technique. Optical pumped random lasing has been observed in the ZnO random-wall arrays with a threshold intensity of 0.38 MW/cm2 in the emission wavelength from 380 to 395 nm. The optical gain was attributed to the closed-loop scattering and light amplification of the ZnO random-wall. The experimental result suggests that the morphology of nanostructure is the key factor to effect random lasing. 相似文献
993.
得到局部G-凸一致空间上具有S-KKM性质的集值映射的新的几乎不动点定理和不动点定理.我们的结果对已有文献中的相应结论进行了改进和一般化. 相似文献
994.
利用η-Carleson测度给出了单位球上不同Privalov以及不同加权Bergman-Privalov空间之间的复合算子是度量有界或度量紧的充要条件,并给出了一些函数理论方面的刻画. 相似文献
995.
Oxide heterojunctions made of p-type La0.8Sr0.2MnO3 (LSMO) and niobium-doped n-type SrTiO3 (STO:Nb) have been fabricated by the pulsed laser deposition (PLD) technique and characterized under UV light irradiation by measuring the current-voltage, photovoltaic properties and the junction capacitance. It is shown that the heterojunctions work as an efficient UV photodiode, in which photogenerated holes in the STO:Nb substrate are injected to the LSMO film. The maximum surface hole density Q/e and external quantum efficiency γ are estimated to be 8.3×1012 cm−2 and 11% at room temperature, respectively. They are improved significantly in a p-i-n junction of LSMO/STO/STO:Nb, where Q/e and γ are 3.0×1013 cm−2 and 27%, respectively. 相似文献
996.
DaXinSHI YaQingFENG ShunHeZHONG 《中国化学快报》2005,16(5):685-687
Photoinduced synthesis of CO2 and CH4 was investigated using a batch reaction system on several photoactive materials supported on silicon dioxide. Single semiconductor showed higher selectivity to C1 compounds. The production of C2-C3 oxygenates took place preferentially on composite semiconductor photocatalysts. In particular, it was found that acetone was the primary product over Cu/CdS-TiO2/SiO2. 相似文献
997.
In order to check whether superconductivity occurs in the acceptor doped fullerenes C60(MF6)2 (M=As, P, Sb) and to study their magnetic and structural properties, we have carried out magnetic, EPR and NMR measurements of these compounds. Temperature dependences of magnetic susceptibility down to 5 K and field dependences of magnetic moment at 5 K show no ‘bulk’ transition in superconducting state. Some reasons of the absence of superconductivity, such as insufficient charge transfer between C60 and intercalated species and inhomogeneity of the compounds under study, are discussed. 相似文献
998.
Qixin Guo Mitsuhiro NishioHiroshi Ogawa Akira Yoshida 《Solid State Communications》2003,126(11):601-604
Temperature dependence of optical reflectance spectra in vacuum ultraviolet region for aluminum nitride has been measured on high-quality single crystal with synchrotron radiation. The dominant structure due to the interband transition is observed at photon energy around 7.7 eV. With decreasing temperature, the energy position of the dominant structure in the reflectance spectra shifts towards higher energy. The experimental data has been fitted to the Bose-Einstein expression and the obtained parameter related to the strength of the electron-phonon interactions is much smaller than that for the peak at 6.2 eV, suggesting that the higher-lying interband transition energy decreases more slowly with increasing temperature in aluminum nitride (AlN). 相似文献
999.
Recently, Miracle proposed that the intermediate structure in metallic glasses could be usefully characterized as an ordered face centered cubic packing of solute-centered coordination clusters. In this paper we examine the stability of such solute ordered arrangements in binary hard sphere mixtures subject to density maximization through local particle moves. 相似文献
1000.
O. Maksimov P. Fisher M. Skowronski P.A. Salvador M. Snyder J. Xu X. Weng 《Journal of Crystal Growth》2008,310(11):2760-2766
MgO films were grown on (0 0 1) yttria-stabilized zirconia (YSZ) substrates by molecular beam epitaxy (MBE). The crystalline structures of these films were investigated using X-ray diffraction and transmission electron microscopy. Growth temperature was varied from 350 to 550 °C, with crystalline quality being improved at higher temperatures. The MgO films had a domain structure: (1 1 1)[1 1 2¯]MgO(0 0 1)[1 0 0]YSZ with four twin variants related by a 90° in-plane rotation about the [1 1 1]MgO axis. The observed epitaxial orientation was compared to previous reports of films grown by pulsed laser deposition and sputtering and explained as resulting in the lowest interface energy. 相似文献