全文获取类型
收费全文 | 49491篇 |
免费 | 4954篇 |
国内免费 | 5534篇 |
专业分类
化学 | 40551篇 |
晶体学 | 1005篇 |
力学 | 3022篇 |
综合类 | 284篇 |
数学 | 3783篇 |
物理学 | 11334篇 |
出版年
2024年 | 112篇 |
2023年 | 646篇 |
2022年 | 1478篇 |
2021年 | 1405篇 |
2020年 | 2029篇 |
2019年 | 1775篇 |
2018年 | 1504篇 |
2017年 | 1765篇 |
2016年 | 2177篇 |
2015年 | 2058篇 |
2014年 | 2404篇 |
2013年 | 3476篇 |
2012年 | 2915篇 |
2011年 | 3102篇 |
2010年 | 2584篇 |
2009年 | 3028篇 |
2008年 | 2980篇 |
2007年 | 3004篇 |
2006年 | 2721篇 |
2005年 | 2395篇 |
2004年 | 2399篇 |
2003年 | 1992篇 |
2002年 | 2083篇 |
2001年 | 1377篇 |
2000年 | 1116篇 |
1999年 | 903篇 |
1998年 | 819篇 |
1997年 | 668篇 |
1996年 | 694篇 |
1995年 | 611篇 |
1994年 | 580篇 |
1993年 | 415篇 |
1992年 | 426篇 |
1991年 | 294篇 |
1990年 | 223篇 |
1989年 | 213篇 |
1988年 | 195篇 |
1987年 | 155篇 |
1986年 | 129篇 |
1985年 | 103篇 |
1984年 | 109篇 |
1983年 | 52篇 |
1982年 | 93篇 |
1981年 | 118篇 |
1980年 | 126篇 |
1979年 | 131篇 |
1978年 | 103篇 |
1977年 | 79篇 |
1976年 | 71篇 |
1973年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
《Surface and interface analysis : SIA》2003,35(4):395-402
Two different types of plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices—extruded and injection moulded—were studied in the non‐sterilized condition and after 25 and 50 kGy of beta irradiation. The polymer surfaces were analysed by scanning electron microscopy (SEM) equipped with an x‐ray energy‐dispersive spectroscopy (XEDS) and by atomic force microscopy (AFM). The inner surface of two parts of a venous line showed a different morphology according to their original formulation (for extrusion or injection moulding process) and reacted differently on sterilization with beta irradiation. Moulded parts were affected only slightly by the radiation step, whereas the variations were bigger for the extruded parts. In order to gain the best performances for the medical devices studied, the utmost care must be taken in the sterilization step, which should be optimized as well as the other steps of the manufacturing process. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
62.
Akhlesh Lakhtakia 《Optik》2004,115(4):151-158
63.
The study of the angular distribution of slow particles during high energy hadron-nucleus interaction indicates that emission of slow particles takes place from a thermally non-equilibrated system. This evidence has come out from the presence of intermittency - a phenomenon that reveals a fractal structure and represents a self-similarity in the particle production process. Hence, this study highlights inadequacy of cascade-evaporation model and advocates the need of its refinement. 相似文献
64.
采用ICP-AES法对钛基复合材料中的合金元素镍、钕、铁的测定进行了研究,着重进行了基体元素及待测元素镍、钕、铁之间干扰试验及各元素在测定浓度范围内的线性相关性试验,进行了酸度试验,测定了钛基复合材料中3种元素的含量,得到了较好的精密度和准确度。方法简便、可靠,获得满意的分析结果。 相似文献
65.
H. Yamaguchi K. Kanisawa S. Miyashita Y. Hirayama 《Physica E: Low-dimensional Systems and Nanostructures》2004,23(3-4):285
We studied the structural, electrical, and mechanical properties of an InAs thin film grown on GaAs (1 1 1)A substrates by molecular beam epitaxy. In contrast to conventionally used (0 0 1) surfaces, where Stranski–Krastanov growth dominates the highly mismatched heteroepitaxy, layer-by-layer growth of InAs can be established. One of the largest advantages of this unique heteroepitaxial system is that it provides a two-dimensional electron gas system in the near-surface region without the problem of electron depletion. We review the fundamental properties and applications of this unique heteroepitaxial system. 相似文献
66.
E. A. El-Amri M. I. Al-Jarallah F. Abu-Jarad Fazal-ur-Rehman 《Radiation measurements》2003,36(1-6):453-456
The uniformity in radon exhalation rates for 46 tiles of granite, marble and ceramic used as construction materials were determined using “Can Technique” employing CR-39 nuclear track detectors (NTDs). On each tile, two sealed cans, each enclosing one NTD fixed at the center of the tile surface area covered by the can, were mounted at two different locations of each individual tiles. The track production rates on the NTDs representing radon exhalation rates were measured. The radon exhalation rates from the surface of individual tiles showed uniform exhalations within the calculated uncertainties of the measured values. This makes Can Technique an alternative simple method to measure radon exhalation rates. Calibration required to convert track production rates into radon exhalation rates for the used can and NTD was done using an active technique. The correlation between the measurements by the two techniques shows a good linear correlation coefficient (0.83). 相似文献
67.
Hyun Chul Choi Min Kyu Lee Hyun Joon Shin Seung Bin Kim 《Journal of Electron Spectroscopy and Related Phenomena》2003,130(1-3):85-96
To investigate the formation of a solid electrolyte interface (SEI) on the Li1+xV3O8 electrode surface in the thermodynamic stability range of the organic electrolyte, we applied scanning photoelectron microscopy (SPEM) to a pristine electrode and to an electrode after ten cycles. The F K-edge absorption spectrum of the cycled electrode showed that LiF forms on the electrode surface during the lithium insertion–extraction process in the Li1+xV3O8/Li cell. The photoelectron spectrum for the cycled electrode showed intense spectral features corresponding to Li 1s, F 2s, F 2p, and P 2p electron signals, whereas these spectral features were of negligible intensity for the pristine electrode. The above results give strong support for the formation of an SEI that consists of LiF and compounds containing phosphorus during operation of the battery. The SPEM images also revealed that the fluorine distribution on the surface of the cycled electrode was inhomogeneous. 相似文献
68.
ZHOU Ming-Xiua② YANG Chuna DENG Xiao-Yana YU Wei-Feib LI Jin-Shanb a 《结构化学》2006,25(6):647-652
1 INTRODUCTION Silicon and its alloy have been widely applied in such fields as electronic industry, high-temperature structural ceramics, etc. In addition, the researches on silicon and its relevant materials greatly promote the rapid development of modern optics and infor- mation technology. Therefore, more and more at- tention is focused on the structure of silicon, oxide of silicon and the interfaces between silicon and metal or nonmetal. As an ideal passive film on the Si surface, S… 相似文献
69.
70.
Dinesh Topwal U. Manju Sugata Ray S. Raj D. D. Sarma S. R. Krishnakumar M. Bertolo S. La Rosa G. Cautero 《Journal of Chemical Sciences》2006,118(1):87-92
Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function
of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of
such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish
that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is
responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with
composition fluctuations of the type Sr2Fe1+x
Mo1-x
O6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献