全文获取类型
收费全文 | 30832篇 |
免费 | 208篇 |
国内免费 | 280篇 |
专业分类
化学 | 12012篇 |
晶体学 | 269篇 |
力学 | 1422篇 |
综合类 | 12篇 |
数学 | 9181篇 |
物理学 | 8424篇 |
出版年
2023年 | 42篇 |
2021年 | 76篇 |
2020年 | 121篇 |
2019年 | 97篇 |
2018年 | 1240篇 |
2017年 | 1476篇 |
2016年 | 784篇 |
2015年 | 599篇 |
2014年 | 526篇 |
2013年 | 737篇 |
2012年 | 3287篇 |
2011年 | 2534篇 |
2010年 | 1870篇 |
2009年 | 1593篇 |
2008年 | 686篇 |
2007年 | 718篇 |
2006年 | 718篇 |
2005年 | 4506篇 |
2004年 | 3982篇 |
2003年 | 2360篇 |
2002年 | 522篇 |
2001年 | 296篇 |
2000年 | 115篇 |
1999年 | 178篇 |
1998年 | 125篇 |
1997年 | 72篇 |
1996年 | 64篇 |
1995年 | 47篇 |
1994年 | 56篇 |
1993年 | 47篇 |
1992年 | 191篇 |
1991年 | 168篇 |
1990年 | 149篇 |
1989年 | 120篇 |
1988年 | 113篇 |
1987年 | 70篇 |
1986年 | 60篇 |
1985年 | 52篇 |
1984年 | 45篇 |
1983年 | 37篇 |
1979年 | 37篇 |
1976年 | 89篇 |
1975年 | 47篇 |
1974年 | 45篇 |
1973年 | 58篇 |
1972年 | 42篇 |
1970年 | 38篇 |
1969年 | 38篇 |
1968年 | 42篇 |
1966年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
Miroslav Veverka Peter ?imon Ján Lokaj Eva Veverková 《Monatshefte für Chemie / Chemical Monthly》2012,10(4):65-71
Abstract
Crystals of the α-form of imatinib mesylate with various habits (e.g., polyhedral-like and plate-like) were prepared from various organic solvents (e.g., butyl lactate, 4-methyl-2-pentanone, 2-methyl-2-butanol, 2-isopropoxyethanol, propyl ether) by several precipitation methods. The methods provide imatinib mesylate in a non-needle-shaped crystalline α-form. The crystal modification was identified by hot-stage microscopy, scanning electron microscopy, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRPD). The analyses by DSC, IR, and XRPD indicate that imatinib mesylate crystals with various habits have the same crystal structure. The plate-like habit has been also observed in the system where the organic solvent acts as a precipitant. 相似文献993.
994.
Dorota Majda Wac?aw Makowski Maria Mańko 《Journal of Thermal Analysis and Calorimetry》2012,109(2):663-669
Thermoporosimetry, i.e., DSC measurements of melting point depression of water and heptane confined in mesopores, has been used for determination the pore size distribution of several mesoporous silicas synthesized with the use of micelle templates. Porosity of these materials was additionally characterized by low-temperature nitrogen adsorption and quasi-equilibrated thermodesorption of nonane. The pore size distributions obtained using the water thermoporosimetry were similar to those determined using the other methods, but the pore size values found for the narrow pore materials were underestimated by ca 1?nm. Too large pore sizes obtained for the wide pore silica from heptane thermoporosimetry were attributed to nonlinear dependence of the melting point depression on the reciprocal of the pore size. 相似文献
995.
996.
997.
Xing Zhao Gary Shultis Ryan Hurley Michael Sutton William Fourney Uli Leiste Xiaomin Deng 《Experimental Mechanics》2014,54(4):539-555
Small scale models representing key vehicle structural elements, including both floorboards and bottom-mounted, downward V-shape hulls in various configurations, have been manufactured and subjected to a range of buried blast loading conditions. By varying surface stand-off distance and depth of burial for several hull and structure configurations, the input-scaled response of aluminum full-scale vehicle floorboards has been quantified using high speed stereo-vision. Specifically, the maximum vertical acceleration on the floorboard and the corresponding Head Injury Criterion (HIC15) are quantified as metrics to assess the severity of the blast event. Results show standard V-shaped hulls provide essential blast mitigation, with reductions in floorboard measurements up to 47X in maximum acceleration and HIC15. Though variations in protective hull geometry provide modest reductions in the severity of a floorboard blast event, results also show that personnel on typical floorboard structures during blast loading events will incur unacceptable shock loading conditions, resulting in either serious or fatal injury. A more appropriate design scenario would be to consider situations that employ frame-mounted passenger seating to reduce the potential for injury. A second set of experiments will be presented in Part II that focuses on frame motions and accelerations when steel frames and steel structures are employed with various frame connections and coatings for frame blast mitigation. 相似文献
998.
999.
We construct a representation of the infinite dimensional complex Clifford algebra on the Hilbert space of square-integrable
complex-valued functions on the Cantor set, which we show to be equivalent to the classical Fock representation. 相似文献
1000.