全文获取类型
收费全文 | 143370篇 |
免费 | 16517篇 |
国内免费 | 8452篇 |
专业分类
化学 | 103108篇 |
晶体学 | 1859篇 |
力学 | 6619篇 |
综合类 | 520篇 |
数学 | 14984篇 |
物理学 | 41249篇 |
出版年
2023年 | 1023篇 |
2022年 | 2286篇 |
2021年 | 2654篇 |
2020年 | 3882篇 |
2019年 | 5309篇 |
2018年 | 4261篇 |
2017年 | 4009篇 |
2016年 | 7210篇 |
2015年 | 6349篇 |
2014年 | 7488篇 |
2013年 | 9740篇 |
2012年 | 9112篇 |
2011年 | 8739篇 |
2010年 | 7884篇 |
2009年 | 7798篇 |
2008年 | 7568篇 |
2007年 | 6680篇 |
2006年 | 5943篇 |
2005年 | 5407篇 |
2004年 | 4724篇 |
2003年 | 4211篇 |
2002年 | 5040篇 |
2001年 | 4161篇 |
2000年 | 3436篇 |
1999年 | 2183篇 |
1998年 | 1707篇 |
1997年 | 1478篇 |
1996年 | 1388篇 |
1995年 | 1169篇 |
1994年 | 1226篇 |
1993年 | 1173篇 |
1992年 | 1114篇 |
1991年 | 1163篇 |
1990年 | 1143篇 |
1989年 | 1076篇 |
1988年 | 935篇 |
1987年 | 935篇 |
1986年 | 900篇 |
1985年 | 933篇 |
1984年 | 919篇 |
1983年 | 826篇 |
1982年 | 804篇 |
1979年 | 801篇 |
1978年 | 812篇 |
1977年 | 806篇 |
1976年 | 920篇 |
1975年 | 812篇 |
1974年 | 845篇 |
1973年 | 847篇 |
1972年 | 752篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
991.
992.
993.
994.
995.
Peng Ping Wenshou Wang Xuesi Chen Xiabin Jing 《Journal of Polymer Science.Polymer Physics》2007,45(5):557-570
Poly(ε‐caprolactone)‐based segmented polyurethanes (PCLUs) were prepared from poly(ε‐caprolactone) diol, diisocyanates (DI), and 1,4‐butanediol. The DIs used were 4,4′‐diphenylmethane diisocyanate (MDI), 2,4‐toluenediisocyanate (TDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI). Differential scanning calorimetry, small‐angle X‐ray scattering, and dynamic mechanical analysis were employed to characterize the two‐phase structures of all PCLUs. It was found that HDI‐ and MDI‐based PCLUs had higher degree of microphase separation than did IPDI‐ and TDI‐based PCLUs, which was primarily due to the crystallization of HDI‐ and MDI‐based hard‐segments. As a result, the HDI‐based PCLU exhibited the highest recovery force up to 6 MPa and slowest stress relaxation with increasing temperature. Besides, it was found that the partial damage in hard‐segment domains during the sample deformation was responsible for the incomplete shape‐recovery of PCLUs after the first deformation, but the damage did not develop during the subsequent deformation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 557–570, 2007 相似文献
996.
Yu. G. Slizhov M. A. Gavrilenko 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(3):489-490
The separation of mixtures of phenols, alcohols, and alkylbenzenes by gas chromatography on adsorption layers of nickel and copper alizarinates was investigated. The thermodynamic parameters were calculated. It was shown that the sorbates differ in strength of interaction with the copper and nickel ions in their alizarin complexes. 相似文献
997.
Yu. V. Pokonova 《Russian Journal of Applied Chemistry》2007,80(11):1964-1968
Advantage of use residue from thermal cracking and products of its condensation as components of the mixture for manufacturing mechanically rigid (93%) granulated and ground carbon sorbents with extended volume of micropores (up to 0.27 cm3/cm3), showing enhanced sorption activity (E is up to 25.6 kJ mol?1) and high ability of separation various gas mixtures is demonstrated. As a carrier for medicine preparations these adsorbents show higher performance as compared with industrial samples. Solutions of the cracking residue can be used for impregnation of worked out zeolites for petroleum technology and for production of organomineral adsorbents with high adsorption capacity on extraction mercury from sewages. 相似文献
998.
Yu. G. Tselishchev 《Colloid Journal》2007,69(4):537-539
The capillary pressure in a liquid interlayer between two spherical particles is calculated as a function of their sizes and the wetting properties of the liquid. 相似文献
999.
Reaction of diethoxyphosphorylimine of methyl trifluoropyruvate with 1,3-C,N-and-N,N-binucleophiles led to a variety of N-phosphorylated fluorine-containing heterocycles, including the fused ones.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2176–2178, November, 2007. 相似文献
1000.
The crystallization behavior of miscible syndiotactic polystyrene (sPS) and atactic polystyrene (aPS) blends with different sPS/aPS weight ratios was investigated in supercritical CO2 by using Fourier‐transform infrared spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction. Supercritical CO2 and aPS exhibited different effects on the conformational change of sPS and competed with each other. Increasing the content of amorphous aPS in the blends made its effect on the conformational change of sPS gradually surpass that of supercritical CO2. Supercritical CO2 favored the formation of the helical conformation of sPS in lower temperature range and the all trans planar conformation in higher temperature range, instead of forming the latter one only in higher temperature range in ambient atmosphere. However, increasing aPS content in the blends pushed the range for forming the helical conformation to lower temperature and made the all trans planar conformation dominant in aPS/sPS 25/75 blend after treating in supercritical CO2 above 60 °C. The all trans planar zigzag conformation was more favorable than the helical conformation after mixing aPS in sPS in supercritical CO2. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1755–1764, 2007 相似文献