全文获取类型
收费全文 | 8196篇 |
免费 | 317篇 |
国内免费 | 920篇 |
专业分类
化学 | 7059篇 |
晶体学 | 129篇 |
力学 | 257篇 |
综合类 | 4篇 |
数学 | 50篇 |
物理学 | 1934篇 |
出版年
2024年 | 18篇 |
2023年 | 385篇 |
2022年 | 149篇 |
2021年 | 155篇 |
2020年 | 198篇 |
2019年 | 205篇 |
2018年 | 170篇 |
2017年 | 219篇 |
2016年 | 328篇 |
2015年 | 258篇 |
2014年 | 300篇 |
2013年 | 442篇 |
2012年 | 609篇 |
2011年 | 573篇 |
2010年 | 423篇 |
2009年 | 600篇 |
2008年 | 453篇 |
2007年 | 535篇 |
2006年 | 450篇 |
2005年 | 342篇 |
2004年 | 327篇 |
2003年 | 213篇 |
2002年 | 154篇 |
2001年 | 182篇 |
2000年 | 149篇 |
1999年 | 150篇 |
1998年 | 154篇 |
1997年 | 119篇 |
1996年 | 104篇 |
1995年 | 104篇 |
1994年 | 93篇 |
1993年 | 88篇 |
1992年 | 66篇 |
1991年 | 78篇 |
1990年 | 59篇 |
1989年 | 36篇 |
1988年 | 62篇 |
1987年 | 42篇 |
1986年 | 52篇 |
1985年 | 53篇 |
1984年 | 63篇 |
1983年 | 38篇 |
1982年 | 68篇 |
1981年 | 42篇 |
1980年 | 37篇 |
1979年 | 43篇 |
1978年 | 13篇 |
1976年 | 5篇 |
1975年 | 16篇 |
1973年 | 5篇 |
排序方式: 共有9433条查询结果,搜索用时 78 毫秒
61.
A new series of acrylates with the same mesogens containing thioester as bridge-bondwere synthesized, and the acrylates were characterized by H~1 NMR, IR and MS. Thepolymers were obtained by radical polymerization using AIBN as initiator. The monomersand polymers exhibit thermotropic-enantiotropic liquid crystalline behavior. 相似文献
62.
4-(2-氨基噻唑)-间苯二酚为柱前衍化剂液相色谱/电化学检测Fe、Co、Ni格日勒,李惠梅,李南强,汪尔康(中国科学院长春应用化学研究所电分析化学开放实验室,北京大学化学系,长春,130022)关键词液相色谱,Fe,Co,Ni,4-(2-氨基噻唑)... 相似文献
63.
贮氢合金材料电化学与表面性能的研究进展①杨勇李骏林祖赓(厦门大学化学系,固体表面物理化学国家重点实验室,厦门361005)八十年代后期以来,人们对地球的环境保护提出了更高的要求,而便携式电器(如移动电话,摄像机与笔记本电脑等)对电池的需求也大量增加... 相似文献
64.
S. M. A. Shibli V. S. Dilimon V. S. Saji 《Journal of Solid State Electrochemistry》2007,11(2):201-208
It has been recently proved that RuO2 can act as an effective surface activator of aluminum alloy sacrificial anodes. TiO2 has the property of stabilizing RuO2 coating and resisting biofouling on metal surfaces. Hence, a mixed oxide catalytic coating of TiO2 and RuO2 can enhance the galvanic performance of aluminum alloy sacrificial anodes and resists biofouling on the anode surface. In the present work RuO2–TiO2 mixed oxide was coated on aluminum alloy sacrificial anodes. The large and uniform porous nature of the coating was found to facilitate efficient ion diffusion. The coating was found to persist on the anode even after 3 months of galvanic exposure. The anode having an optimum combination of the mixed oxide had 70% TiO2 as the major component in the coating. The catalytic coating significantly improved the performance of the anodes to a large extent. 相似文献
65.
Cheng-Fang Ou 《European Polymer Journal》2002,38(3):467-473
The crystallization characteristics of polypropylene (PP) and low ethylene content PP copolymers with and without nucleating agents were studied by differential scanning calorimetry (DSC). PP and PP copolymers was blended with three different kinds of co[poly(butylene terephthalate-p-oxybenzoate)] copolyesters, designated B28, B46, and B64, with the copolyester level varying from 5 to 15 wt.%. All samples were prepared by solution blending in hot xylene solvent at 50 °C. The crystallization behavior of samples was then studied by DSC. The results indicate that these three copolyesters accelerate the crystallization rate of PP and PP copolymers in a manner similar to that of a nucleating agent. The acceleration of crystallization rate was most pronounced in these blend systems with a maximum level at 5 wt.% of B28. The observed changes in crystallization behavior are explained by the effect of the composition and the amount of copolyester in the blends. 相似文献
66.
The diffraction peak broadening induced by hydrogen absorption-desorption cycling has been analyzed in four different Laves phase compounds with the C14 and C15 structures. The broadening is due to strain most probably originating from dislocations generated at the interface between the α and β hydride phases in connection with the cell volume difference between the two phases. It has been shown that it is strongly compound dependent. In the case of the C14 structure, the broadening is large and isotropic, and the latter can be related to the isotropy of the elastic constants of the metallic phase. The broadening is less for the compounds with the C15 structure, which can be related to a possibly softer lattice. Better ageing properties after long-term cycling are predicted for this crystal structure. 相似文献
67.
Carlo Mazzocchia Akim Kaddouri Giovanni Modica Roberto Nannicini Guido Audisio Costantino Barbieri Fabio Bertini 《Journal of Analytical and Applied Pyrolysis》2003,70(2):263-276
Pyrolysis of hardware components wastes consisting mainly in computers and television components was performed under nitrogen. The degradation products were separated in three fractions, solid, liquid and gaseous. Analyses of the three phases were carried out using gas chromatography (GC), mass spectrometry (MS), thermal analysis and infrared spectroscopy. The energetic content of the gas phase and the economic value of the liquid phase were also determined. The gas fraction produced was rich in light hydrocarbons and hydrogen. Consequently, its calorific value was high and widely sufficient to make the pyrolysis process self-sustained. The main products of the liquid phase were phenol and isopropylphenol (ca. 50–80 wt.%). The presence of Br-based compounds, deriving from the flame retardant employed in hardware components, were also detected. A controlled combustion of the solid phase permitted to obtain the glass fibres unaltered, which can be recycled. 相似文献
68.
TS分子筛催化性能研究Ⅰ.TS-2分子筛催化1,2-丙二醇液相氧化反应的研究①伏再辉尹笃林(湖南师范大学精细催化合成研究所,长沙410081)关键词TS-2分子筛1,2-丙二醇氧化催化氧化自1983年Taramasso[1]首次合成具有ZSM-5结构... 相似文献
69.
Summary The novel theoretical scheme IMOMM, integrating ab initio and molecular mechanics contributions in a single geometry optimization process, is applied to the structural determination of different [OsO4(NR3)] (NR3 = bulky chiral alkaloid derivative) species closely related to active catalysts for the asymmetric dihydroxylation of olefins. Computed values compare in a satisfactory way with available X-ray data, the relationship between the Os-N distance and the nature of the NR3, ligand being properly reproduced. The computational scheme allows the separate quantification of electronic and steric effects, as well as the identification of the specific steric repulsions responsible for the difference. 相似文献
70.