全文获取类型
收费全文 | 1863篇 |
免费 | 43篇 |
国内免费 | 8篇 |
专业分类
化学 | 1154篇 |
晶体学 | 12篇 |
力学 | 51篇 |
数学 | 249篇 |
物理学 | 448篇 |
出版年
2023年 | 8篇 |
2022年 | 26篇 |
2021年 | 46篇 |
2020年 | 28篇 |
2019年 | 27篇 |
2018年 | 28篇 |
2017年 | 19篇 |
2016年 | 59篇 |
2015年 | 52篇 |
2014年 | 47篇 |
2013年 | 93篇 |
2012年 | 98篇 |
2011年 | 128篇 |
2010年 | 88篇 |
2009年 | 74篇 |
2008年 | 127篇 |
2007年 | 113篇 |
2006年 | 124篇 |
2005年 | 99篇 |
2004年 | 93篇 |
2003年 | 79篇 |
2002年 | 62篇 |
2001年 | 30篇 |
2000年 | 22篇 |
1999年 | 25篇 |
1998年 | 25篇 |
1997年 | 23篇 |
1996年 | 26篇 |
1995年 | 18篇 |
1994年 | 18篇 |
1993年 | 6篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 7篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1970年 | 6篇 |
排序方式: 共有1914条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
G. Carelli N. Ioli A. Messina A. Moretti S. Schepis F. Strumia 《International Journal of Infrared and Millimeter Waves》1998,19(9):1191-1199
We measured the dependence of the reflectivity of InSb crystals upon temperature in the submillimeter region using monochromatic radiation from an optically pumped far infrared (FIR) laser. The measures allowed us to determine the value of the electron effective mass at low temperatures with radiations of different frequencies. Our measurements extend the results obtained recently on pure crystals with magneto-optical methods to the low temperatures region where only old measures were available. 相似文献
5.
Nicola Arcozzi Enrico Casadio Tarabusi Fausto Di Biase Massimo A. Picardello 《Transactions of the American Mathematical Society》2006,358(6):2781-2798
We establish a potential theoretic approach to the study of twist points in the boundary of simply connected planar domains.
6.
7.
J. C. S. Moraes E. M. Telles F. C. Cruz A. Scalabrin D. Pereira C. Garelli N. Ioli A. Moretti F. Strumia 《International Journal of Infrared and Millimeter Waves》1991,12(12):1475-1486
We report the discovery of 57 new fir laser lines from13CD3OH molecule optically pumped by a waveguide CO2 laser of 300 MHz tunability. For all lines, precise frequency offset measurements between the CO2 line center and the center of the absorbing13CD3OH line were performed using the transferred Lamb-Dip technique. We have also measured directly the frequency of seven FIR laser lines by heterodyning with already known laser lines. We present a complete list of all known laser lines (134) and frequency measurements (24) for this molecule.Work supported by CNPq, FAPESP, FAEP-Brasil, and CNR-Italia 相似文献
8.
Massimo Camarda Antonino La Magna Francesco La Via 《Journal of computational physics》2007,227(2):1075-1093
A modified Kinetic Lattice Monte Carlo model has been developed to predict growth rate regimes and defect formation in the case of the homo-epitaxial growth of close packed crystalline structures. The model is an improvement over standard Monte Carlo algorithms, which usually retain fixed atom positions and bond partners indicative of perfect crystal lattices. Indeed, we extend the concepts of Monte Carlo growth simulations on super-lattices containing additional sites (defect sites) with respect to those of the reference material. This extension implies a reconsideration of the energetic mapping, which is extensively presented, and allows to describe a complex phenomenology that is out of accessibility of standard stochastic approaches. Results obtained using the Kawasaki and the Bond-Counting rules for the transition probability of the Monte Carlo event are discussed in details. These results demonstrate how the defect types (local or extended), the formation mechanisms and the defect generation regimes can be characterized using our approach. 相似文献
9.
G. Carelli A. Di Siena N. Ioli A. Moretti G. Moruzzi F. Strumia 《International Journal of Infrared and Millimeter Waves》1994,15(4):619-633
We have measured the frequencies of four CH3OH far-infrared laser lines that were previously known only by wavelength measurement. Two of these lines turned out to be doublets, bringing the total number of measured lines to six. We can now confirm the assignments of five of them and definitely disprove the assignments proposed for the sixth.In particular we confirm the assignments for the four strong laser lines at 205 and 208 µm pumped by the 9-P(34) CO2 laser line. These lines share a common upper level in the first excited CO-stretch state, and terminate in the upper and lower levels of a hybrid state with J=5. Heterodyne frequency measurements and conventional microwave spectroscopy show that both lines are split into two components approximately 3.5 MHz apart. The origin of this further splitting is interpreted as a perturbed K-splitting.Work supported by Consiglio Nazionale delle Ricerche -Italia 相似文献
10.
G. Carelli N. Ioli A. Moretti D. Pereira F. Strumia R. Densing 《Applied physics. B, Lasers and optics》1988,45(2):97-100
FIR laser lines close to the N+
3
P
2–3
P
1 transition at 122 m can be used as a local oscillator for heterodyne detectors. The frequencies of some candidate laser lines from CH2F2,13CH3OH, CD3OD, and CD3OH have been measured and the output power of the most interesting lines has been optimized. 相似文献