全文获取类型
收费全文 | 27536篇 |
免费 | 3212篇 |
国内免费 | 1881篇 |
专业分类
化学 | 19582篇 |
晶体学 | 246篇 |
力学 | 106篇 |
综合类 | 66篇 |
数学 | 125篇 |
物理学 | 12504篇 |
出版年
2024年 | 35篇 |
2023年 | 193篇 |
2022年 | 662篇 |
2021年 | 755篇 |
2020年 | 889篇 |
2019年 | 861篇 |
2018年 | 735篇 |
2017年 | 830篇 |
2016年 | 1299篇 |
2015年 | 1286篇 |
2014年 | 1311篇 |
2013年 | 2345篇 |
2012年 | 1675篇 |
2011年 | 1806篇 |
2010年 | 1508篇 |
2009年 | 1939篇 |
2008年 | 1835篇 |
2007年 | 1905篇 |
2006年 | 1792篇 |
2005年 | 1417篇 |
2004年 | 1200篇 |
2003年 | 1044篇 |
2002年 | 782篇 |
2001年 | 635篇 |
2000年 | 594篇 |
1999年 | 533篇 |
1998年 | 454篇 |
1997年 | 416篇 |
1996年 | 335篇 |
1995年 | 288篇 |
1994年 | 207篇 |
1993年 | 199篇 |
1992年 | 160篇 |
1991年 | 126篇 |
1990年 | 74篇 |
1989年 | 61篇 |
1988年 | 118篇 |
1987年 | 53篇 |
1986年 | 34篇 |
1985年 | 34篇 |
1984年 | 33篇 |
1982年 | 30篇 |
1981年 | 29篇 |
1980年 | 22篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1974年 | 12篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
用射频等离子体方法在玻璃基底上制备的类金刚石(DLC)薄膜,采用离子注入法掺氮,并对掺氮DLC薄膜紫外(UV)辐照前后的性能变化进行了研究。研究结果表明:随氮离子注入剂量及UV辐照时间的增加,位于2 930cm-1附近的SP
3C-H吸收峰明显变小,而位于1 580cm-1附近的SP2C-H吸收峰则明显增强,薄膜的电阻率明显呈下降趋势;随UV辐照时间的增加,位于1 078cm-1附近的Si-O-Si键数量及位于786cm-1附近的Si-C键数量明显增加。即氮离子注入和UV辐照明显改变了DLC薄膜的结构与特性。 相似文献
62.
Vincent Maurice 《Surface science》2005,581(1):88-104
STM, STS, LEED and XPS data for crystalline θ-Al2O3 and non-crystalline Al2O3 ultra-thin films grown on NiAl(0 0 1) at 1025 K and exposed to water vapour at low pressure (1 × 10−7-1 × 10−5 mbar) and room temperature are reported. Water dissociation is observed at low pressure. This reactivity is assigned to the presence of a high density of coordinatively unsaturated cationic sites at the surface of the oxide film. The hydroxyl/hydroxide groups cannot be directly identify by their XPS binding energy, which is interpreted as resulting from the high BE positions of the oxide anions (O1s signal at 532.5-532.8 eV). However the XPS intensities give evidence of an uptake of oxygen accompanied by an increase of the surface coverage by Al3+ cations, and a decrease of the concentration in metallic Al at the alloy interface. A value of ∼2 for the oxygen to aluminium ions surface concentration ratio indicates the formation of an oxy-hydroxide (AlOxOHy with x + y ∼ 2) hydroxylation product. STM and LEED show the amorphisation and roughening of the oxide film. At P(H2O) = 1 × 10−7 mbar, only the surface of the oxide film is modified, with formation of nodules of ∼2 nm lateral size covering homogeneously the surface. STS shows that essentially the valence band is modified with an increase of the density of states at the band edge. With increasing pressure, hydroxylation is amplified, leading to an increased coverage of the alloy by oxy-hydroxide products and to the formation of larger nodules (∼7 nm) of amorphous oxy-hydroxide. Roughening and loss of the nanostructure indicate a propagation of the reaction that modifies the bulk structure of the oxide film. Amorphisation can be reverted to crystallization by annealing under UHV at 1025 K when the surface of the oxide film has been modified, but not when the bulk structure has been modified. 相似文献
63.
64.
A complete study of the spectrum of a finite-dimensional Bose operator is carried out in the paper. The cases in which the
spectrum is discrete or continuous are studied.
Translated fromMatematicheskie Zametki, Vol. 61, No. 6, pp. 835–854, June, 1997.
Translated by A. M. Chebotarev 相似文献
65.
The dehydration of molybdic acid, MoO3---H2O, was studied by thermal analysis, X-ray diffractometry and FTIR spectroscopy. The results show that an intermediate phase, MoO3-2/3H2O is formed at 216 °C and the monoclinic form of MoO3 is grown above 350 °C. The mechanism of dehydration and structural rearrangement were confirmed by the features of the infrared spectra showing formation of corner-shared MoO6 octahedra. 相似文献
66.
67.
Contaminant uranium poses unique problems for decontamination of former weapons processing and nuclear power facilities, as well as chemical plants, waste storage sites and former mining facilities. In addition, dealing with the possibility of intentional (i.e., a terrorist act) or accidental release of radioactive material in a populated area requires an accurate understanding of the nature of the association of such material with structural surfaces. These surfaces must also be considered in the context of repeated contamination, and the importance of atmospheric exposure, interaction with other possible contaminants, and corrosion or surface degradation due to such exposure must be taken into account. Complementary spectroscopic techniques, especially surface spectroscopies, are essential in developing models for the interaction of contaminants with surfaces and interfaces. In this review (which also presents new data on uranium association with corroding steel surfaces), we collect models of this association as determined by spectroscopic techniques, assess the important considerations in the development of more accurate models, and address some of the questions which remain. 相似文献
68.
Bart M. J. M. Suijkerbuijk Duncan M. Tooke Anthony L. Spek Gerard van Koten Robertus J. M. Klein Gebbink Prof. Dr. 《无机化学与普通化学杂志》2007,633(15):2649-2653
A tin(IV) porphyrin was combined with two axial NCN‐pincer platinum(II) fragments by utilizing the oxophilicity of the apical positions on the tin atom and the acidic nature of the NCN‐pincer platinum derived benzoic acid. The solid‐state structure determined by X‐ray crystallography revealed some close contacts between the pincer complexes and the meso‐p‐tolyl subsitutents of the porphyrin. It was shown by 1H NMR spectroscopy that these close contacts were not present in solution and that this compound can potentially act as a novel building block for supramolecular architectures. 相似文献
69.
Editorial: Metal-Enhanced Fluorescence 总被引:1,自引:0,他引:1
70.