全文获取类型
收费全文 | 9736篇 |
免费 | 1615篇 |
国内免费 | 1233篇 |
专业分类
化学 | 7515篇 |
晶体学 | 112篇 |
力学 | 482篇 |
综合类 | 118篇 |
数学 | 1023篇 |
物理学 | 3334篇 |
出版年
2024年 | 12篇 |
2023年 | 143篇 |
2022年 | 311篇 |
2021年 | 271篇 |
2020年 | 369篇 |
2019年 | 396篇 |
2018年 | 300篇 |
2017年 | 266篇 |
2016年 | 498篇 |
2015年 | 479篇 |
2014年 | 567篇 |
2013年 | 748篇 |
2012年 | 807篇 |
2011年 | 778篇 |
2010年 | 648篇 |
2009年 | 609篇 |
2008年 | 737篇 |
2007年 | 631篇 |
2006年 | 580篇 |
2005年 | 533篇 |
2004年 | 419篇 |
2003年 | 358篇 |
2002年 | 358篇 |
2001年 | 324篇 |
2000年 | 219篇 |
1999年 | 197篇 |
1998年 | 133篇 |
1997年 | 116篇 |
1996年 | 115篇 |
1995年 | 82篇 |
1994年 | 87篇 |
1993年 | 74篇 |
1992年 | 61篇 |
1991年 | 76篇 |
1990年 | 56篇 |
1989年 | 43篇 |
1988年 | 26篇 |
1987年 | 25篇 |
1986年 | 25篇 |
1985年 | 32篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1979年 | 4篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1966年 | 2篇 |
1936年 | 2篇 |
1935年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Ying‐Ling Liu Chuan‐Shao Wu Yie‐Shun Chiu Wen‐Hsuan Ho 《Journal of polymer science. Part A, Polymer chemistry》2003,41(15):2354-2367
A novel epoxy system was developed through the in situ curing of bisphenol A type epoxy and 4,4′‐diaminodiphenylmethane with the sol–gel reaction of a phosphorus‐containing trimethoxysilane (DOPO–GPTMS), which was prepared from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with 3‐glycidoxypropyltrimethoxysilane (GPTMS). The preparation of DOPO–GPTMS was confirmed with Fourier transform infrared, 1H and 31P NMR, and elemental analysis. The resulting organic–inorganic hybrid epoxy resins exhibited a high glass‐transition temperature (167 °C), good thermal stability over 320 °C, and a high limited oxygen index of 28.5. The synergism of phosphorus and silicon on flame retardance was observed. Moreover, the kinetics of the thermal oxidative degradation of the hybrid epoxy resins were studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2354–2367, 2003 相似文献
82.
本讨论一类一阶线性脉冲时滞微分不等式和方程解的振动性质,获得了此类不等式免最终正解或最终负解以及方穆所有解振动的新的充分条件。 相似文献
83.
84.
85.
86.
87.
Mei‐Jiau Huang 《国际流体数值方法杂志》2005,48(5):521-539
The technique of splitting a fat vortex element (with a core width larger than some threshold) into some thin ones in order to fix the convergence problem of the core‐spreading vortex methods is convenient and efficient. In particular, it keeps the method purely Lagrangian. In the present investigation, the splitting process is further viewed as part of the physical diffusion process. A new splitting method in which several weaker child vortices surround a thinned but still strong parent vortex is proposed. It is found that because of the survival of the parent vortex, the error arising from the splitting events can be largely reduced. The computational amount on the other hand is kept reasonably large by merging similar and close‐by vortices. The merging scheme designed herein not only involves fewer restrictions but also allows merging vortices of opposite rotations through the viewpoint of remeshing. The validity and accuracy of these techniques, proposed particularly for simulations undergoing lots of splitting and merging events, are verified by successfully simulating the interactions between two Burgers vortices under an external straining field. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
88.
Tumor cells transduced with herpes simplex virus thymidine kinase gene have been intensively applied to the field of positron emission tomography via imaging of its substrate. As a pilot synthesis approach, a facile preparation of 5‐[125I] iodoarabinosyl uridine starting from commercially available uridine is reported herein. 相似文献
89.
Hydroxyapatite coating on porous silicon substrate obtained by precipitation process 总被引:2,自引:0,他引:2
Chen Shaoqiang Zhu Ziqiang Zhu Jianzhong Zhang Jian Shi Yanling Yu Ke Wang Weiming Wang Xiaohua Feng Xiao Luo Laiqiang Shao Li 《Applied Surface Science》2004,230(1-4):418-424
Hydroxyapatite Ca10(PO4)6(OH)2 (HAP) is known as a bioactive and biocompatible material, HAP coatings were used to improve the biocompatible of substrate by many researcher, In this work, HAP thin films on porous silicon (PS) substrates have been prepared by aqueous precipitation method with rapid thermal annealing (RTA) processes. The HAP films had been prepared under the annealing temperature ranging from 300 to 1000 °C. By the measurement of X-ray diffraction (XRD), it was found that for the crystallinity optimization, the heat-treatment at 850–950 °C for 1 h would be favorable. Atomic force microscopy (AFM) and scanning electron microscope (SEM) measurements reveal a dense and smooth surface of the HAP film, and tightly adherence of the coating on porous silicon substrate after sintered. Thus, by this method, porous silicon could be increased its bioactivity and so that could be used in the biomedical area. 相似文献
90.
We report a new approach for the self-assembly of cuboid micro-parts onto Si substrates to construct three-dimensional microstructures. To perform assembly, the Si substrates are prepared with a deep cavity array as binding sites. An aggregate composed of hundreds of uniformly aligned micro-parts is formed at the C10F18-H2O interface. The micro-parts are arranged by passing the substrate through the aggregate of micro-parts, thus the micro-parts are left on the substrate, and then the substrate is vibrated ultrasonically in the solution, making it possible for the micro-parts to fall into the cavities on the substrate. Finally the substrate is pulled out of the solution after assembly. This technique could give a high yield of up to 70%, providing a new method for micro-assembly. 相似文献