全文获取类型
收费全文 | 344297篇 |
免费 | 3288篇 |
国内免费 | 1076篇 |
专业分类
化学 | 185767篇 |
晶体学 | 5945篇 |
力学 | 14287篇 |
综合类 | 7篇 |
数学 | 36872篇 |
物理学 | 105783篇 |
出版年
2018年 | 3094篇 |
2017年 | 3125篇 |
2016年 | 5165篇 |
2015年 | 3395篇 |
2014年 | 5215篇 |
2013年 | 14718篇 |
2012年 | 10244篇 |
2011年 | 12584篇 |
2010年 | 8857篇 |
2009年 | 8799篇 |
2008年 | 11674篇 |
2007年 | 11692篇 |
2006年 | 11125篇 |
2005年 | 10122篇 |
2004年 | 9359篇 |
2003年 | 8403篇 |
2002年 | 8186篇 |
2001年 | 10121篇 |
2000年 | 7661篇 |
1999年 | 6047篇 |
1998年 | 4872篇 |
1997年 | 4815篇 |
1996年 | 4626篇 |
1995年 | 4307篇 |
1994年 | 4208篇 |
1993年 | 4049篇 |
1992年 | 4756篇 |
1991年 | 4567篇 |
1990年 | 4505篇 |
1989年 | 4481篇 |
1988年 | 4415篇 |
1987年 | 4448篇 |
1986年 | 4142篇 |
1985年 | 5577篇 |
1984年 | 5639篇 |
1983年 | 4791篇 |
1982年 | 5044篇 |
1981年 | 4845篇 |
1980年 | 4749篇 |
1979年 | 5018篇 |
1978年 | 5271篇 |
1977年 | 5087篇 |
1976年 | 5018篇 |
1975年 | 4832篇 |
1974年 | 4780篇 |
1973年 | 4966篇 |
1972年 | 3244篇 |
1971年 | 2702篇 |
1968年 | 3040篇 |
1967年 | 3179篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
K. Vinay Kumar Reddy B. Sreenivasa Reddy M. Sreenath Reddy Ch. Gopal Reddy P. Yadagiri Reddy K. Rama Reddy 《Radiation measurements》2003,36(1-6):419-423
Studies conducted by Atomic Minerals Directorate of Exploration and Research (AMD) of Hyderabad, India had established the presence of higher concentrations of uranium in Lambapur and Peddagattu areas of Nalgonda district, AP, India and it was estimated that it could be a viable source for commercial extraction. The envisaged extraction process involves dispersion of radioactive particulate matter into atmosphere. Environmental radioactive studies in and around proposed mining areas at this point of time will be extremely useful for establishing base line data before a large scale uranium extraction process comes into existence. To this end, Solid State Nuclear Track Detectors were installed to evaluate indoor radon and thoron concentration levels in the dwellings of the area. The geometric means of radon and thoron concentration levels were found to be (7.1±0.2)×101 and (6.7±0.3)×101 Bq/m3, respectively. Simultaneously, natural background radiation measurements were also made and these levels are found to vary from 770 to 3995 μGy/y in the spatial distribution. 相似文献
992.
Q. H. Liu W. H. Qi T. G. Liu Z. H. Zhu 《International Journal of Theoretical Physics》2003,42(4):783-791
Expectation values of physical quantities in a wave packet involving few stationary states in an infinite square well are calculated. Explicit results show that the expectation values in the classical limit go over to the corresponding classical quantity in the form of the arithmetic mean (in mathematical term, the Fejér's average) of the partial Fourier series converging to the classical quantity. The number of the stationary states is that of the partial Fourer series in the Fejér's average. The quantum uncertainty is then demonstrated to have a classical counterpart. 相似文献
993.
Analysis of a part of the meteorite which fell at Dergaon (India) on March 2, 16.40 local time (2001) is presented with the
help of FTIR, absorption and atomic spectra. The FTIR spectrum exhibits prominent absorption bands in the region 800–1100
cm−1, originating from the valence vibration of SiO4, a basic component of the silicate lattice. 相似文献
994.
995.
Vladimir B. Arion Alexey A. Nazarov Christian G. Hartinger Gerald Giester Bernhard K. Keppler 《应用有机金属化学》2003,17(9):723-724
For the unsymmetrical title compound, 1‐bromo‐1′‐[(2S)‐N‐(1‐hydroxy‐3‐methylbutane‐2‐yl)]‐ferroceneamide, two independent molecules were found in the asymmetric unit. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
996.
997.
H. Niino X. Ding R. Kurosaki A. Narazaki T. Sato Y. Kawaguchi 《Applied Physics A: Materials Science & Processing》2004,79(4-6):827-828
Laser-induced backside wet etching (LIBWE) of silica glass plates was performed to fabricate an imprinting template for hot embossing in polymer substrates such as polystyrene and silicone resin. Well-defined inverse surface-micropatterns of gratings and grid arrays on the substrates were produced by the hot embossing using a surface-structured silica glass as the template. These results indicate that the LIBWE method allows us to generate robust glass molding tools that exhibit the inverse shapes of the intended microstructures. PACS 52.38.Mf; 68.47.Mn; 81.05.Kf; 81.05.Lg; 83.50.Uv 相似文献
998.
An extended eigenvalue problem for collisionless electrostatic driftwaves in cylindrical and slab geometry is discussed and solved in local approximation. The fact of a minimum threshold for the ITG instability (ηi-mode) is used to get a unique concept for profile determination. 相似文献
999.
1000.