全文获取类型
收费全文 | 221828篇 |
免费 | 11703篇 |
国内免费 | 3521篇 |
专业分类
化学 | 135543篇 |
晶体学 | 3066篇 |
力学 | 10322篇 |
综合类 | 215篇 |
数学 | 24000篇 |
物理学 | 63906篇 |
出版年
2021年 | 2076篇 |
2020年 | 3285篇 |
2019年 | 5086篇 |
2018年 | 4614篇 |
2017年 | 4398篇 |
2016年 | 7736篇 |
2015年 | 5640篇 |
2014年 | 7352篇 |
2013年 | 11591篇 |
2012年 | 9108篇 |
2011年 | 9478篇 |
2010年 | 8993篇 |
2009年 | 9068篇 |
2008年 | 9369篇 |
2007年 | 8732篇 |
2006年 | 7707篇 |
2005年 | 7066篇 |
2004年 | 6639篇 |
2003年 | 6047篇 |
2002年 | 6865篇 |
2001年 | 6641篇 |
2000年 | 5172篇 |
1999年 | 3361篇 |
1998年 | 2791篇 |
1997年 | 2603篇 |
1996年 | 2374篇 |
1995年 | 2148篇 |
1994年 | 2095篇 |
1993年 | 2112篇 |
1992年 | 2140篇 |
1991年 | 2446篇 |
1990年 | 2366篇 |
1989年 | 2413篇 |
1988年 | 2301篇 |
1987年 | 2326篇 |
1986年 | 2148篇 |
1985年 | 2695篇 |
1984年 | 2689篇 |
1983年 | 2334篇 |
1982年 | 2379篇 |
1981年 | 2290篇 |
1980年 | 2082篇 |
1979年 | 2399篇 |
1978年 | 2556篇 |
1977年 | 2652篇 |
1976年 | 2732篇 |
1975年 | 2539篇 |
1974年 | 2474篇 |
1973年 | 2639篇 |
1972年 | 2156篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
953.
P L Melgarejo M Ternero I Gracia 《International journal of environmental analytical chemistry》1986,24(4):283-295
A study of the atmospheric pollution by suspended particulate lead in the city of Seville, Spain, was carried out during the period between March 1983 and February 1984. The results obtained from seven sampling stations allowed us to study the site to site variations; there are two locations with average annual concentrations higher than 2 micrograms X m-3. In one station, the meteorological and traffic effects and relationship with other traffic-related pollutants, were investigated. The regression analyses performed on the average monthly data have shown an inverse correlation with wind speed and temperature and a direct correlation with carbon monoxide and smoke concentrations, but no significant correlation was found with the lead deposition levels. 相似文献
954.
955.
Based on an analysis of the signal of an interferometric intensity autocorrelator, we demonstrate theoretically and experimentally a simple technique for retrieving the temporal distributions of the amplitude and phase of an ultrashort light pulse. Assuming that a phase-modulated wave packet has a Gaussian envelope, we derive an analytical expression for the autocorrelator signal in the cases of linear- and quadratic-chirp optical pulses. The experimental and theoretical results are in excellent agreement. In particular, we show that a linear chirp (quadratic phase modulation) can be measured with a good experimental accuracy of no worse than 10%. This yields the possibility of measuring the parameter k2, which describes the dispersion characteristics of a medium in the second order of the dispersion theory, with the same accuracy. Measuring a quadratic chirp by the proposed method is possible only if such a chirp is sufficiently large. 相似文献
956.
On the basis of the hydrodynamic equations for nonlinear elastic-gravity waves beneath a solid ice cover and their Hamiltonian representation, a three-wave kinetic equation for the time evolution of the wave spectrum is formulated. The properties of the kernel of the kinetic integral describing the nonlinear interactions between wave triplets are investigated. An algorithm for numerically calculating the kinetic integral is developed. The rate of nonlinear energy transfer over the wave spectrum is estimated quantitatively and its most important characteristics are found. 相似文献
957.
958.
I. L. Bataronov A. M. Roshchupkin 《Journal of Applied Mechanics and Technical Physics》1991,32(2):259-265
Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 127–134, March–April, 1991. 相似文献
959.
960.
This is a write-up on the foundation of the Sobolev Institute of Mathematics in 1957. 相似文献