全文获取类型
收费全文 | 428386篇 |
免费 | 6044篇 |
国内免费 | 1670篇 |
专业分类
化学 | 233352篇 |
晶体学 | 6078篇 |
力学 | 18411篇 |
综合类 | 14篇 |
数学 | 50521篇 |
物理学 | 127724篇 |
出版年
2020年 | 2833篇 |
2019年 | 2812篇 |
2018年 | 2827篇 |
2017年 | 2755篇 |
2016年 | 5598篇 |
2015年 | 4661篇 |
2014年 | 6234篇 |
2013年 | 19471篇 |
2012年 | 15010篇 |
2011年 | 18753篇 |
2010年 | 11680篇 |
2009年 | 11762篇 |
2008年 | 17230篇 |
2007年 | 17565篇 |
2006年 | 16932篇 |
2005年 | 15469篇 |
2004年 | 13911篇 |
2003年 | 12240篇 |
2002年 | 11993篇 |
2001年 | 13669篇 |
2000年 | 10558篇 |
1999年 | 8281篇 |
1998年 | 6599篇 |
1997年 | 6449篇 |
1996年 | 6469篇 |
1995年 | 5904篇 |
1994年 | 5536篇 |
1993年 | 5282篇 |
1992年 | 5909篇 |
1991年 | 5772篇 |
1990年 | 5315篇 |
1989年 | 5173篇 |
1988年 | 5460篇 |
1987年 | 5072篇 |
1986年 | 4902篇 |
1985年 | 7154篇 |
1984年 | 7180篇 |
1983年 | 5844篇 |
1982年 | 6308篇 |
1981年 | 6251篇 |
1980年 | 6032篇 |
1979年 | 6107篇 |
1978年 | 6159篇 |
1977年 | 6107篇 |
1976年 | 6010篇 |
1975年 | 5891篇 |
1974年 | 5685篇 |
1973年 | 5913篇 |
1972年 | 3458篇 |
1971年 | 2470篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
192.
193.
194.
A. J. Parsons S. D. J. Inglethorpe D. J. Morgan A. C. Dunham 《Journal of Thermal Analysis and Calorimetry》1997,48(1):49-62
Using a system based on non-dispersive infrared (NDIR) detectors, evolved gas analysis (EGA) was able to identify and quantify the principal volatiles produced by heating powdered samples of UK brick clays. From these results, atmospheric emissions likely to result from brick production can be predicted. In addition, EGA results for extruded brick clay test pieces are significantly different from those of powdered samples. Within an extruded brick clay body, evolved gases are contained within a pore system and evolved gas-solid phase reactions also occur. This EGA study provides further evidence on the nature of firing reactions within brick clay bodies. The qualitative and quantitative influence of heating rate — a key process condition in brick manufacture — on gas release is also outlined.Dedicated to Dr. Robert Mackenzie on the occasion of his 75th birthday 相似文献
195.
196.
197.
R.C. Viscovini E.M. Telles A. Scalabrin D. Pereira 《Applied physics. B, Lasers and optics》1997,65(1):33-35
2 laser of wide tunability to pump 13CD3OD we could observe 10 new far infrared laser lines ranging from 109 μm to 472 μm. The lines were generated by pumping infrared
absorbing transitions of large offset appertaining to the C-O stretching Q-branch. All lines were characterised in wavelength,
polarisation, optimum pressure of operation and precise offset measurements.
Received: 17 September 1996/Revised version: 18 November 1996 相似文献
198.
F. A. van Goor S. V. Mitko V. N. Ochkin W. J. Witteman 《Journal of Russian Laser Research》1997,18(2):107-120
Experimental and theoretical results are presented on an XeF(C?A) blue-green laser driven by 5-kJ energy. The laser was pumped by a ferrite-induced discharge of 90 cm in length. The output energy of 0.22 J was obtained with a plane-parallel resonator. A program to simulate laser operation has been developed. Numerical results for a wide range of conditions are compared with experiments performed by us and by other authors. It is found that intracavity refractive losses limit laser operation for XeF pressures above 3 torr. The laser efficiency strongly depends on the discharge-to-cavity length ratio. Possible ways to increase the laser power and efficiency are discussed. 相似文献
199.
200.
The effect of iodine sorption on the free volume of polycarbonate is investigated by Positron Annihilation Lifetime method.
The observed results are interpreted in terms of the Charge Transfer Complex formation and precipitation of iodine at the
initial and final stages of sorption, respectively. At higher levels of sorption, changes in the second lifetime and its intensity
seem to suggest a conformational transformation, probably due to the net change in the amorphous-crystalline boundary regions
of the polymer matrix. The free volume cavities have been predominantly occupied by I-
3 species and the diffusion process obeys Fick’s law. An exponential type correlation has been observed between fractional
free volume and the diffusion coefficient.
Received: 13 June 1996/Accepted: 20 September 1996 相似文献