全文获取类型
收费全文 | 540559篇 |
免费 | 4323篇 |
国内免费 | 1679篇 |
专业分类
化学 | 257710篇 |
晶体学 | 8158篇 |
力学 | 29942篇 |
综合类 | 17篇 |
数学 | 86895篇 |
物理学 | 163839篇 |
出版年
2021年 | 4301篇 |
2020年 | 4562篇 |
2019年 | 5300篇 |
2018年 | 17171篇 |
2017年 | 17131篇 |
2016年 | 16009篇 |
2015年 | 6441篇 |
2014年 | 9976篇 |
2013年 | 21927篇 |
2012年 | 20242篇 |
2011年 | 29739篇 |
2010年 | 20407篇 |
2009年 | 20938篇 |
2008年 | 24454篇 |
2007年 | 26311篇 |
2006年 | 16801篇 |
2005年 | 15713篇 |
2004年 | 15023篇 |
2003年 | 13968篇 |
2002年 | 13095篇 |
2001年 | 14344篇 |
2000年 | 10721篇 |
1999年 | 8209篇 |
1998年 | 6974篇 |
1997年 | 6840篇 |
1996年 | 6411篇 |
1995年 | 5562篇 |
1994年 | 5573篇 |
1993年 | 5368篇 |
1992年 | 5945篇 |
1991年 | 6247篇 |
1990年 | 5883篇 |
1989年 | 5907篇 |
1988年 | 5613篇 |
1987年 | 5744篇 |
1986年 | 5401篇 |
1985年 | 6838篇 |
1984年 | 6990篇 |
1983年 | 5804篇 |
1982年 | 5846篇 |
1981年 | 5623篇 |
1980年 | 5387篇 |
1979年 | 5928篇 |
1978年 | 5867篇 |
1977年 | 6033篇 |
1976年 | 6005篇 |
1975年 | 5669篇 |
1974年 | 5556篇 |
1973年 | 5681篇 |
1972年 | 4159篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
431.
432.
S. Piekarski 《Continuum Mechanics and Thermodynamics》1992,4(2):109-119
In this paper the explicit form of such systems of conservation laws, which imply an additional conservation law, is determined. It is shown that there are many classes of such systems besides the symmetric conservative ones. From the point of view of phenomenological thermodynamics, this result can be interpreted as a sort of integration of the constraints imposed by the second law of thermodynamics. 相似文献
433.
434.
435.
P. J. Skevington M. A. G. Halliwell M. H. Lyons S. J. Amin M. A. Z. Rejman-Greene G. J. Davies 《Journal of Crystal Growth》1992,120(1-4):328-332
InP/InGaAs multiple quantum well structures with up to 200 periods have been grown by CBE. These structures exhibit exceptional lateral uniformity, measured as ±1 Å in period, ±13 ppm in lattice mismatch and ±0.5 nm in wavelength across a 2 inch wafer. Good surface morphology, sharp interfaces and excellent growth control have all been demonstrated. 相似文献
436.
M.N. Kotby S.R. El-Sady S.E. Basiouny Y.A. Abou-Rass M.A. Hegazi 《Journal of voice》1991,5(4):316-320
The management of voice disorders may follow one of four approaches: surgical, pharmacological, technical aid, and/or voice therapy. The latter approach offers a wide variety of techniques, each based on certain theoretical beliefs. One of these techniques is the Smith Accent Method. The principles and goals of the Accent Method are presented. The results of its application are discussed. This technique proved effective for cases of functional voice disorders, vocal nodules, and some degrees of vocal fold paralysis. 相似文献
437.
V.I. Marakhonov N.A. Rogachev E.I. Terukov J.T. Ishkalov I.N. Trapeznikova 《Physica B: Condensed Matter》1991,170(1-4):571-573
Magnetron assisted silane decomposition (MASD) is proposed as a method for deposition of a-Si:H and its alloys. In this method a silane containing gas mixture is passed through the magnetron plasma near a target and decomposed there. The deposition rate in the case of the c-Si target is increased 3 times compared to magnetron sputtering and film properties are changed. a-SiSn:H is obtained with a Sn target. 相似文献
438.
439.
S. Z. Levendorskiî 《Siberian Mathematical Journal》1992,33(5):826-834
Rostov-on-Don. Translated fromSibirskiî Matematicheskiî Zhurnal, Vol. 33, No. 5, pp. 91–99, September–October, 1992. 相似文献
440.
A 480 L evacuable reaction chamber, equipped with FT-IR spectroscopy on-line and ion chromatography off-line, has been used to study the gas phase reaction between the nitrate radical, NO3, and the reduced organic sulphur compounds CH3CH2SH, (CH3CH2)2S, (CH3CH2)2S2, and CH3CH2SCH3 in air. The products CH3CH2SO3H, SO2, H2SO4, CH3CHO, and CH3CH2ONO2 were identified and quantified in the reactions of the first three compounds, CH3CH2SH, (CH3CH2)2S, and (CH3CH2)2S2. The reaction products were CH3CH2SO3H, CH3SO3H, SO2, H2SO4, CH3CHO, and CH2O in the reaction of CH3CH2SCH3. On the basis of identified reaction products and intermediates observed in the infrared spectra, mechanisms are proposed for the reactions between the NO3 radical and the four reduced organic sulphur compounds. The results of this study, together with those from previous experiments performed in this laboratory on CH3SCH3, CH3SH, and CH3SSCH3 lead to the conclusion that all these species, in the reaction with the NO3 radical, follow a similar degradation mechanism producing SO2, H2SO4, R? SO3H, R? CHO, and R? CH2ONO2, as the main reaction products. The inital step of the reaction of NO3 with R? S? R and R? S? H type (R = CH3, CH2CH3) reduced organic sulphur compounds was found to be H-atom abstraction, probably after the formation of an initial adduct. For the reaction between NO3 and R? S? S? R type compounds, evidence for an addition-decomposition reaction, as the initial steps, was obtained. R? S·, R? S(O)·, and R? S(O)2· appear to be formed as intermediates in all the reactions. © John Wiley & Sons, Inc. 相似文献