全文获取类型
收费全文 | 5689篇 |
免费 | 1148篇 |
国内免费 | 1058篇 |
专业分类
化学 | 4064篇 |
晶体学 | 102篇 |
力学 | 427篇 |
综合类 | 189篇 |
数学 | 725篇 |
物理学 | 2388篇 |
出版年
2024年 | 8篇 |
2023年 | 105篇 |
2022年 | 150篇 |
2021年 | 215篇 |
2020年 | 248篇 |
2019年 | 222篇 |
2018年 | 212篇 |
2017年 | 214篇 |
2016年 | 270篇 |
2015年 | 294篇 |
2014年 | 373篇 |
2013年 | 469篇 |
2012年 | 486篇 |
2011年 | 487篇 |
2010年 | 386篇 |
2009年 | 352篇 |
2008年 | 433篇 |
2007年 | 406篇 |
2006年 | 351篇 |
2005年 | 302篇 |
2004年 | 221篇 |
2003年 | 196篇 |
2002年 | 179篇 |
2001年 | 164篇 |
2000年 | 193篇 |
1999年 | 171篇 |
1998年 | 111篇 |
1997年 | 122篇 |
1996年 | 89篇 |
1995年 | 94篇 |
1994年 | 65篇 |
1993年 | 63篇 |
1992年 | 50篇 |
1991年 | 45篇 |
1990年 | 32篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1971年 | 1篇 |
1968年 | 2篇 |
1964年 | 1篇 |
1961年 | 3篇 |
1959年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有7895条查询结果,搜索用时 125 毫秒
81.
The effects of ion implantation on ployacetylene films PA have been studied with Ar~+, Fe~+, C1~+, I~+, Na~+ and K~+ ions in the energy range of 15—30 keV. The changes of PA films in the electrical conductivity, due to chemical doping and ion implantation in relation to their structure and depth profiles of impurities, were measured through infrared (ATR/FTIK), Rutherford backscattering spectrometry (RBS) and the four probe technique. In all cases, ion implantation of active ions exhibits the same effects as chemical doping. The formation of p-n junction is observed at the interface of implanted region and chemical doped PA substrate. The mechanism of interaction process between ion beam and polymer is also discussed. 相似文献
82.
83.
84.
85.
86.
The synthesis of rod-coil diblock copolymers was achieved for the firsttime by TEMPO-mediated "living" free radical polymerization of styrene and 2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene(MPCS). The block architecture of the two diblockcopolymers thus prepared, MPCS-b-St(5400/2400) and MPCS-b-St(10800/8700), was con-firmed by GPC, DSC studies and the formation of multimolecular micelles. 相似文献
87.
Analysis of acyclovir by high performance capillary electrophoresis with on-column amperometric detection 总被引:1,自引:0,他引:1
The separation of acyclovir (ACV) by high performance capillary electrophoresis (HPCE) with on-column amperometric detection using alpha-amino-5-mercapto-3,4-dithiazole (AMD) as internal standard is described. The calibration line was linear in the range of 0.5-20 mg/L of ACV. The detection limit was 0.15 mg/L of ACV. Its recovery ranged from 98 to 101% with relative standard deviations (RSDs) from 1.9 to 3.2% (n = 5). This method was successfully used for determining ACV in some pharmaceuticals and human urine. Comparable results with HPCE with ultraviolet (UV) detection and amperometric detection were obtained. 相似文献
88.
Xiong JY Narayanan J Liu XY Chong TK Chen SB Chung TS 《The journal of physical chemistry. B》2005,109(12):5638-5643
Kinetics as well as the evolution of the agarose gel topology is discussed, and the agarose gelation mechanism is identified. Aqueous high melting (HM) agarose solution (0.5% w/v) is used as the model system. It is found that the gelation process can be clearly divided into three stages: induction stage, gelation stage, and pseudoequilibrium stage. The induction stage of the gelation mechanism is identified using an advanced rheological expansion system (ARES, Rheometric Scientific). When a quench rate as large as 30 deg C/min is applied, gelation seems to occur through a nucleation and growth mechanism with a well-defined induction time (time required for the formation of the critical nuclei which enable further growth). The relationship between the induction time and the driving force which is determined by the final setting temperature follows the 3D nucleation model. A schematic representation of the three stages of the gelation mechanism is given based on turbidity and rheological measurements. Aggregation of agarose chains is promoted in the polymer-rich phase and this effect is evident from the increasing mass/length ratio of the fiber bundles upon gelation. Continuously increasing pore size during gelation may be attributed to the coagulation of the local polymer-rich phase in order to achieve the global minimum of the free energy of the gelling system. The gel pore size determined using turbidity measurements has been verified by electrophoretic mobility measurements. 相似文献
89.
90.