全文获取类型
收费全文 | 1907篇 |
免费 | 60篇 |
国内免费 | 21篇 |
专业分类
化学 | 1190篇 |
晶体学 | 5篇 |
力学 | 79篇 |
数学 | 151篇 |
物理学 | 563篇 |
出版年
2023年 | 11篇 |
2022年 | 25篇 |
2021年 | 45篇 |
2020年 | 39篇 |
2019年 | 23篇 |
2018年 | 32篇 |
2017年 | 20篇 |
2016年 | 54篇 |
2015年 | 34篇 |
2014年 | 46篇 |
2013年 | 90篇 |
2012年 | 61篇 |
2011年 | 100篇 |
2010年 | 75篇 |
2009年 | 63篇 |
2008年 | 85篇 |
2007年 | 80篇 |
2006年 | 90篇 |
2005年 | 75篇 |
2004年 | 63篇 |
2003年 | 71篇 |
2002年 | 54篇 |
2001年 | 57篇 |
2000年 | 56篇 |
1999年 | 50篇 |
1998年 | 23篇 |
1997年 | 22篇 |
1996年 | 32篇 |
1995年 | 28篇 |
1994年 | 38篇 |
1993年 | 40篇 |
1992年 | 33篇 |
1991年 | 23篇 |
1990年 | 13篇 |
1989年 | 20篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 17篇 |
1975年 | 15篇 |
1973年 | 11篇 |
排序方式: 共有1988条查询结果,搜索用时 15 毫秒
91.
J. Lí nares M. V. P Rez R. E. La Fuente X. Prieto C. Montero L. Gato J. I. Rodriguez C. G mez-Reino 《Fiber and Integrated Optics》1993,12(3):231-245
An experimental analysis of graded-index (GRIN) planar waveguides produced by ion exchange in soda-lime glass is presented. This study is based on a recent model describing nonlinear diffusion. Likewise the modal coupling between planar waveguides, produced in the same substrate, is analyzed in order to design efficient integrated optical components. Finally, waveguiding structures induced by Kerr effect in glass are proposed and analyzed. 相似文献
92.
Herranz J Pastor I Castejon F de La Luna E Garcia-Cortes I Barth CJ Ascasibar E Sanchez J Tribaldos V 《Physical review letters》2000,85(22):4715-4718
Fine structures are found in the TJ-II stellarator electron temperature and density profiles, when they are measured using a high spatial resolution Thomson scattering system. These structures consist of peaks and valleys superimposed to a smooth average. Some irregularities remain in an ensemble average of discharges with similar macroscopic parameters such as line density, central temperature, and plasma current. They are found in all the magnetic configurations explored in plasmas heated by electron cyclotron waves. Their characteristics are shown and their possible origin is discussed. 相似文献
93.
94.
A Mukherjee M Dasgupta DJ Hinde CR Morton AC Berriman RD Butt JO Newton H Timmers 《Pramana》2001,57(1):195-198
Fusion cross-sections for the 7Li + 12C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy
evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their
contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections
due to the breakup of 7Li may not be significant for 7Li + 12C reaction at energies around the barrier. 相似文献
95.
96.
M. Papa G. Cardella A. Di Pietro S. L. Li A. Musumarra G. Pappalardo F. Rizzo A. De Rosa G. Inglima M. La Commara D. Pierroutsakou M. Romoli 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(2):205-212
The properties of the strong fluctuations observed in the excitation functions of Dissipative Binary Heavy Ion Collisions (DBHIC) have been studied for the system28Si+28Si in the energy range 150 MeV ≤E lab ≤ 156 MeV with 150 keV step laboratory incident energy, by angular distributions and excitation functions measurements. Experimental results are compared to the the recently developed Partially Overlapping Molecular Level Model (POMLM). The parameters of the model have been determined with reasonable accuracy by describing all the quantities characterizing the fluctuations in the excitation functions i.e.: Average Angular Distributions, Energy Autocorrelation Functions, Variances, Angular Correlation Coefficients. The results of the analysis strongly support the idea of a process proceeding through the formation of an highly excited “nuclear molecule”. Experimental data collected at the most forward angles show the effects of strong excitation of a few final channels. 相似文献
97.
T. Idehara T. Saito H. Mori H. Tsuchiya La Agusu S. Mitsudo 《International Journal of Infrared and Millimeter Waves》2008,29(2):131-141
Long pulse operation up to 1 msec of a high frequency gyrotron with a pulse magnet has been successfully carried out in a
frequency range including 1 THz. In the experiments, the timing of an electron beam pulse injection is adjusted at the top
of the magnetic field pulse, where the variation of field intensity is negligible. The operation cavity modes seem to be TE1, 12 and TE4,12 at the second harmonics. The corresponding frequencies are 903 GHz and 1,013 GHz, respectively. Additionally several features
of radiation measurement results of the gyrotron are described and brief considerations are presented. 相似文献
98.
De La Rosa Nathaly Kristiansson Per Nilsson E. J. Charlotta Ros Linus Pallon Jan Skogby Henrik 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(1):253-259
Journal of Radioanalytical and Nuclear Chemistry - Proton-induced reaction (p,α) is one type of nuclear reaction analysis (NRA) suitable especially for light element quantification.... 相似文献
99.
AbstractHigh performance and high temperature polymers are a class of polymeric materials exhibiting high thermal stability and their resistance to fire makes them valuable assets for many applications. Those applications include as typical examples high temperature gas separation membranes, automotive and aerospace industry as well as the construction industry. The high performance polymers have been synthesized since the early 1960s, and have developed rapidly over the past few decades. Most high performance polymers comprise a highly aromatic backbone, linear chains, and strong inter-chain interactions. This review deals mostly with commercial polymeric materials. Studies regarding their thermal behavior, degradation mechanism and their reaction to fire have been synthetically combined in order to bring out potential insight concerning the effect of the thermal decomposition and thermal behavior on the fire properties of those polymers. 相似文献
100.
da Silva Pedro Rafael Sena Laís Cristina Santana Silva Rubens Pedro Lorena de Santana Danielle Cristine Almeida Silva de Santana Fernando José Malagueño 《Analytical and bioanalytical chemistry》2019,411(16):3447-3461
Analytical and Bioanalytical Chemistry - This study aimed to determine simultaneously five major street cocaine adulterants (caffeine, lidocaine, phenacetin, diltiazem, and hydroxyzine) in human... 相似文献