全文获取类型
收费全文 | 2431篇 |
免费 | 293篇 |
国内免费 | 230篇 |
专业分类
化学 | 1641篇 |
晶体学 | 45篇 |
力学 | 132篇 |
综合类 | 31篇 |
数学 | 298篇 |
物理学 | 807篇 |
出版年
2024年 | 9篇 |
2023年 | 39篇 |
2022年 | 86篇 |
2021年 | 110篇 |
2020年 | 98篇 |
2019年 | 101篇 |
2018年 | 80篇 |
2017年 | 82篇 |
2016年 | 113篇 |
2015年 | 105篇 |
2014年 | 138篇 |
2013年 | 165篇 |
2012年 | 191篇 |
2011年 | 190篇 |
2010年 | 124篇 |
2009年 | 127篇 |
2008年 | 167篇 |
2007年 | 128篇 |
2006年 | 120篇 |
2005年 | 101篇 |
2004年 | 96篇 |
2003年 | 75篇 |
2002年 | 92篇 |
2001年 | 60篇 |
2000年 | 58篇 |
1999年 | 40篇 |
1998年 | 23篇 |
1997年 | 22篇 |
1996年 | 28篇 |
1995年 | 22篇 |
1994年 | 14篇 |
1993年 | 15篇 |
1992年 | 6篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1968年 | 6篇 |
排序方式: 共有2954条查询结果,搜索用时 15 毫秒
1.
2.
1689-nm diode lasers used in medical apparatus have been fabricated and characterized. The lasers had pnpn InP current confinement structure, and the active region consisted of 5 pairs of InGaAs quantum wells and InGaAsP barriers. 相似文献
3.
4.
YBa2Cu3O7-δ and Tl2Ba2CaCu2O8 thin films for microwave filters were synthesized by pulsed laser deposition and the two-step thalliation process. Substrate
quality requirements and the relation of thin film morphology, microstructure with microwave surface resistance were discussed. 相似文献
5.
6.
Guilin Wen Qing-Guo Wang Chong Lin Xu Han Guangyao Li 《Chaos, solitons, and fractals》2006,29(5):1142-1146
Synchronization under output feedback control with multiple random time delays is studied, using the paradigm in nonlinear physics—Chua’s circuit. Compared with other synchronization control methods, output feedback control with multiple random delay is superior for a realistic synchronization application to secure communications. Sufficient condition for global stability of delay-dependent synchronization is established based on the LMI technique. Numerical simulations fully support the analytical approach, in spite of the random delays. 相似文献
7.
8.
9.
Fukuji Higashi Chong Su Cho Hideo Kakinoki Osao Sumita 《Journal of polymer science. Part A, Polymer chemistry》1977,15(10):2303-2309
Semiconducting organic polymer was obtained by the modification of polyacrylamide (PAAm)–Cu++ chelate with iodine in acetone. Favorable conditions for preparing the chelate effective for the conduction were investigated. Surface resistivities were affected by the amounts of cupric salts and iodine, satisfactory results being given by about 25 wt % of the salts based on PAAm and more than 1 wt % of iodine on the chelate. The conductivity was also varied with the degree of neutralization of the chelate in solution, and optimal values were obtained by addition of about an equimolar amount of potassium hydroxide to cupric salts. Effective structures of the polymer chelate in solution were assumed on the basis of the visible and the NMR spectra and potentiometric titration. 相似文献
10.
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