全文获取类型
收费全文 | 1668篇 |
免费 | 112篇 |
国内免费 | 145篇 |
专业分类
化学 | 1300篇 |
晶体学 | 41篇 |
力学 | 94篇 |
综合类 | 9篇 |
数学 | 19篇 |
物理学 | 462篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 30篇 |
2021年 | 47篇 |
2020年 | 57篇 |
2019年 | 51篇 |
2018年 | 45篇 |
2017年 | 60篇 |
2016年 | 54篇 |
2015年 | 66篇 |
2014年 | 98篇 |
2013年 | 136篇 |
2012年 | 77篇 |
2011年 | 147篇 |
2010年 | 67篇 |
2009年 | 94篇 |
2008年 | 78篇 |
2007年 | 116篇 |
2006年 | 85篇 |
2005年 | 82篇 |
2004年 | 67篇 |
2003年 | 67篇 |
2002年 | 71篇 |
2001年 | 38篇 |
2000年 | 32篇 |
1999年 | 50篇 |
1998年 | 26篇 |
1997年 | 25篇 |
1996年 | 27篇 |
1995年 | 26篇 |
1994年 | 24篇 |
1993年 | 10篇 |
1992年 | 19篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有1925条查询结果,搜索用时 31 毫秒
161.
162.
163.
Hidenori Okuzaki Takui Takahashi Yusuke Hara Hu Yan 《Journal of Polymer Science.Polymer Physics》2008,46(3):305-310
Unlike conventional electrospun polymer fibers deposited on a target electrode as a randomly oriented mesh, poly(p‐xylenetetrahydrothiophenium chloride) was electrospun into centimeters‐long yarns vertically on the surface of the electrode but parallel to the electric field. The diameter of the yarn was strongly affected by the concentration, spinning rate, and viscosity of the polymer solution, but less dependent on the applied voltage. The subsequent carbonization of thus‐electrospun yarns at 600–1000 °C resulted in uniaxially aligned carbon nanofibers with average diameters of 127–184 nm. On the basis of Raman spectra, the graphitic crystallite size and the molar fraction of graphite were estimated to be 1.2–1.4 and 0.21–0.24 nm, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 305–310, 2008 相似文献
164.
Muhammad M. R. Qureshi Chao Zhu Chao-Hsin Lin Liang-Shih Fan 《中国颗粒学报》2006,4(3):147-152
A three-dimensional simulation study is performed for investigating the hydrodynamic behaviors of a cross-flow liquid nitrogen spray injected into an air-fluidized catalytic cracking (FCC) riser of rectangular cross-section. Rectangular nozzles with a fixed aspect ratio but different fan angles are used for the spray feeding. While our numerical simulation reveals a generic three-phase flow structure with strong three-phase interactions under rapid vaporization of sprays, this paper tends to focus on the study of the effect of nozzle fan angle on the spray coverage as well as vapor flux distribution by spray vaporization inside the riser flow. The gas-solid (air-FCC) flow is simulated using the multi-fluid method while the evaporating sprays (liquid nitrogen) are calculated using the Lagrangian trajectory method, with a strong two-way coupling between the Eulerian gas-solid flow and the Lagrangian trajectories of spray. Our simulation shows that the spray coverage is basically dominated by the spray fan angle. The spray fan angle has a very minor effect on spray penetration. The spray vaporization flux per unit area of spray coverage is highly non-linearly distributed along the spray penetration. The convection of gas-solid flow in a riser leads to a significant downward deviation of vapor generated by droplet vaporization, causing a strong recirculating wake region in the immediate downstream area of the spray. 相似文献
165.
A. A. Volodin P. V. Fursikov Yu. A. Kasumov I. I. Khodos B. P. Tarasov 《Russian Chemical Bulletin》2005,54(10):2281-2285
Carbon nanofibers were synthesized by the pyrolysis of ethylene and methane on hydrides of intermetallides LaNinHx (n = 2, 3, 5; x = 0.1–4). The influence of parameters of the synthesis (temperature and the ratio of gases in an Ar: H2: C2H4 (CH4) mixture) on the structure of nanofibers thus formed was studied. Hydrides of nickel intermetallides are more efficient catalytic
systems than metallic nickel.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2210–2214, October, 2005. 相似文献
166.
A sonic spray ionization (SSI) interface for liquid chromatography-mass spectrometry (LC-MS) analysis was optimized for analysis of 2-[(1R)-3-[bis(1-methylethyl)amino]-1-phenylpropyl]-4-methyl-phenol (tolterodine), used as a model drug substance, and the influence of different parameter settings was evaluated using factorial design. A comparison between SSI and electrospray ionization (ESI) was made for tolterodine, tolterodine metabolites, and a set of steroids.SSI was found to give slightly poorer repeatability and broader peaks for tolterodine compared to ESI. However, there was no significant difference in chromatographic peak shape, and the repeatability using SSI was similar to that obtained using ESI if a ratio (area of tolterodine/area of metabolite) was used. In this study, the sensitivity was higher using SSI. For the analysis of pregnanolone, less water loss was obtained using SSI, probably due to less energy being transferred to the analyte upon ionization. 相似文献
167.
Zhu Wang Lingfeng Zhu Guobao Zhang Gensuo Zhao Yan Zhu Linkai Chang 《Journal of Thermal Analysis and Calorimetry》1997,49(3):1509-1512
The thermal pyrolysis of carboxymethyl hydroxypropyl sesbania gum and hydroxypropyl sesbania gum in air and nitrogen atmospheres were studied in order to establish the thermal stability of carboxymethyl hydroxypropyl sesbania gum. The results indicate that the stability of carboxymethyl hydroxypropyl sesbania gum against pyrolysis is higher than that of hydroxypropyl sesbania gum. The main state of carboxymethyl hydroxypropyl sesbania gum and hydroxypropyl sesbania gum can be assigned as random noncrystalline.We express our thanks to Dr. Yaxiong Xie for his help in this work. 相似文献
168.
本文在实验室条件下对赤峰的两种褐煤进行了煤热解气化实验研究,考察了气化室温度和流化状态等实验条件变化对煤气产率,组分的影响,得到了具体条件下的煤气化综合过程实验数据。 相似文献
169.
170.