全文获取类型
收费全文 | 11493篇 |
免费 | 1369篇 |
国内免费 | 583篇 |
专业分类
化学 | 6647篇 |
晶体学 | 564篇 |
力学 | 147篇 |
综合类 | 40篇 |
数学 | 105篇 |
物理学 | 5942篇 |
出版年
2024年 | 10篇 |
2023年 | 116篇 |
2022年 | 153篇 |
2021年 | 172篇 |
2020年 | 239篇 |
2019年 | 226篇 |
2018年 | 231篇 |
2017年 | 232篇 |
2016年 | 425篇 |
2015年 | 371篇 |
2014年 | 479篇 |
2013年 | 1016篇 |
2012年 | 560篇 |
2011年 | 798篇 |
2010年 | 665篇 |
2009年 | 815篇 |
2008年 | 789篇 |
2007年 | 882篇 |
2006年 | 795篇 |
2005年 | 629篇 |
2004年 | 680篇 |
2003年 | 548篇 |
2002年 | 440篇 |
2001年 | 357篇 |
2000年 | 291篇 |
1999年 | 255篇 |
1998年 | 225篇 |
1997年 | 161篇 |
1996年 | 150篇 |
1995年 | 150篇 |
1994年 | 124篇 |
1993年 | 78篇 |
1992年 | 67篇 |
1991年 | 46篇 |
1990年 | 42篇 |
1989年 | 36篇 |
1988年 | 41篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 19篇 |
1984年 | 20篇 |
1983年 | 7篇 |
1982年 | 18篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Matthew M. Malwitz Paul D. Butler Lionel Porcar Drew P. Angelette Gudrun Schmidt 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):3102-3112
The influence of shear on viscoelastic solutions of poly(ethylene oxide) (PEO) and clay [montmorillonite, i.e., Cloisite NA+ (CNA)] was investigated with rheology and small-angle neutron scattering (SANS). The steady-state viscosity and SANS were used to measure the shear-induced orientation and relaxation of the polymer and clay platelets. Anisotropic scattering patterns developed at much lower shear rates than in pure clay solutions. The scattering anisotropy saturated at low shear rates, and the CNA clay platelets aligned with the flow, with the surface normal parallel to the gradient direction. The cessation of shear led to partial and slow randomization of the CNA platelets, whereas extremely fast relaxation was observed for laponite (LRD) platelets. These PEO–CNA networklike solutions were compared with previously reported PEO–LRD networks, and the differences and similarities, with respect to the shear orientation, relaxation, and polymer–clay interactions, were examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3102–3112, 2004 相似文献
133.
The three-dimensional structure of the calcite (104)-water interface has been determined with surface X-ray scattering. Nine crystal truncation rods (including specular and non-specular rods) were measured providing both vertical and lateral sensitivity to the interfacial structure. The results reveal that calcite is nearly ideally terminated with a single surface hydration layer that includes two inequivalent water molecules having distinct heights of 2.3 ± 0.1 and 3.5 ± 0.2 Å, each with a well-defined lateral registry with respect to the calcite surface. No additional layering of water is observed beyond this surface hydration layer. Small displacements in the outer two calcium carbonate layers were also observed. These results are compared with previous experimental and computational results. 相似文献
134.
135.
Renhe Chu Jichang Yan Suoyuan Lian Yuehong Wang Fucheng Yan Dawei Chen 《Solid State Communications》2004,130(12):789-792
The interesting shape (shuttle-like, sphere with needles, uniform particles) rutile titania were prepared by the hydrolysis of TiCl4 in high acidic aqueous solution in the absence or presence of PEG-1000. PEG-1000 acted as dispersant, which could control the shape and size of the precipitate of titania. As a result, shuttle-like nanocrystalline appeared and the aggregation was improved with the increase of the amount of acid and the decrease of the concentration of TiCl4 in the absence of PEG-1000. Uniform nanoparticles were obtained in the presence of PEG-1000 and the diameter of the particles decreased with increasing the amount of PEG-1000. This process simplification will lower production cost and make continuous process possible. The products were analyzed using X-ray diffractometer, transmission electron microscopy. 相似文献
136.
采用MOCVD技术在Al2O3(0001)衬底上生长了GaN薄膜,使用透射光谱、光致发光光谱和X射线双晶衍射三种技术测试了五类GaN薄膜样品,实验结果表明:GaN薄膜透射谱反映出的GaN质量与X射线双晶衍射测量的结果一致,即透射率越大,半高宽越小,结晶质量越好;而X射线双晶衍射峰半高宽最小的样品,其PL谱的带边峰却很弱,这说明PL谱反映样品的光学性能与X射线双晶衍射获得的结晶质量不存在简单的对应关系,同时还报导了一种特殊工艺生长的高阻GaN样品的RBS/沟道结果。 相似文献
137.
P. S. Goyal 《Pramana》2004,63(1):15-24
Inter University Consortium for Department of Atomic Energy Facilities (IUC-DAEF) is an autonomous institute of the University
Grants Commission and provides an interface between the university fraternity and the institutions of Department of Atomic
Energy. Mumbai Centre of IUC-DAEF promotes and supports the use of neutron facilities at Dhruva reactor by the university
scientists. To augment the existing neutron scattering facilities, IUC-DAEF has developed a neutron beam line at Dhruva reactor.
The present paper gives a brief survey of the activities and achievements of Mumbai Centre of IUC-DAEF. 相似文献
138.
The size, shape and surface topology have a strong influence on powders properties, such as: mechanical, optical, catalytic, etc. In addition, when particles have a nanometer size, the dispersion of these features plays an important role.There are a number of techniques, which could be used in order to characterize powders in terms of particle size and shape. However, due to the scale of analysis, well beyond the wavelength of visible light, most of them cannot be applied for investigations of nanopowders.In this paper, transmission electron microscopy (TEM) image analysis and X-ray methods are presented as promising and complementary techniques. An example of their application to ZrO2 nanopowder is shown. The advantages and limitations of each method are described. 相似文献
139.
140.