全文获取类型
收费全文 | 19522篇 |
免费 | 1674篇 |
国内免费 | 5086篇 |
专业分类
化学 | 20433篇 |
晶体学 | 437篇 |
力学 | 538篇 |
综合类 | 156篇 |
数学 | 1682篇 |
物理学 | 3036篇 |
出版年
2024年 | 39篇 |
2023年 | 453篇 |
2022年 | 298篇 |
2021年 | 528篇 |
2020年 | 649篇 |
2019年 | 510篇 |
2018年 | 508篇 |
2017年 | 593篇 |
2016年 | 706篇 |
2015年 | 591篇 |
2014年 | 845篇 |
2013年 | 1401篇 |
2012年 | 1835篇 |
2011年 | 1084篇 |
2010年 | 882篇 |
2009年 | 1208篇 |
2008年 | 1355篇 |
2007年 | 1445篇 |
2006年 | 1308篇 |
2005年 | 1252篇 |
2004年 | 1161篇 |
2003年 | 948篇 |
2002年 | 849篇 |
2001年 | 679篇 |
2000年 | 644篇 |
1999年 | 594篇 |
1998年 | 538篇 |
1997年 | 480篇 |
1996年 | 443篇 |
1995年 | 414篇 |
1994年 | 372篇 |
1993年 | 283篇 |
1992年 | 336篇 |
1991年 | 238篇 |
1990年 | 190篇 |
1989年 | 133篇 |
1988年 | 105篇 |
1987年 | 71篇 |
1986年 | 76篇 |
1985年 | 60篇 |
1984年 | 46篇 |
1983年 | 25篇 |
1982年 | 29篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1975年 | 16篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
81.
82.
By using the tools of statistical physics and recent investigations of the scaling properties of different complex networks,
the structural and evolving properties of the Chinese railway network (CRN) is studied. It has been verified that the CRN
has the same small-world properties of the Indian railway network (IRN). According to the class of small-world networks, we
believe the CRN is a single scale. In addition, a novel result is obtained. Measurements on the CRN indicate that the rate
at which nodes acquire links depends on the node’s degree and follows a power law.
相似文献
83.
Jiangen Huang Guiqin Zhang Yuanhe Huang Decai Fang Deqing Zhang 《Journal of magnetism and magnetic materials》2006
A one-dimensional (1D) silver (I) complex of nitronyl nitroxide with fairly strong antiferromagnetic interaction, in which the metal ions are diamagnetic, is investigated by means of the ab initio crystal orbital method based on the density functional theory. The calculated values of the magnetic coupling constant (J) are close to the experimental measured J value in the periodic system. The magneto-structural correlation reveals that the existence of an antiferromagnetic coupling pathway along nitronyl nitroxide units via silver (I) ion in this system. The spin population distribution also shows the existence of spin delocalization along the ONCNO–Ag–ONCNO, which affords a rational interpretation for the antiferromagnetic interaction mechanism. 相似文献
84.
液态泡沫结构及其稳定性 总被引:2,自引:0,他引:2
液态泡沫由大量气泡密集堆积在少量的表面活性剂溶液中形成,是具有高度自组织结构的典型的软物质.文章从泡沫物理学角度简要介绍了液态泡沫的结构特征和稳定性方面的研究. 相似文献
85.
Iron alloys and aluminum were nitrogen implanted in a controlled oxygen atmosphere and the role of hydrogen on the surface etching mechanisms studied. The surface composition was analyzed by in situ photoemission electron spectroscopy (XPS). In iron alloys, hydrogen strongly etches oxygen, improving nitrogen retention on the surface. On the other hand, hydrogen removes nitrogen from aluminum surfaces, with a deleterious effect on the nitriding effectiveness. The oxygen removal in iron alloys is associated with the catalytic effect of electrons in d-orbitals and the nitrogen removal in aluminum is associated with a steric effect. 相似文献
86.
Praveen K. Tandon Gayatri Sumita Sahgal Manish Srivastava Santosh B. Singh 《应用有机金属化学》2007,21(3):135-138
Catalytic activities of three transition metals, as iridium (III) chloride, rhodium (III) chloride and palladium (II) chloride, were compared in the oxidation of six aromatic aldehydes (benzaldehyde, p‐chloro benzaldehyde, p‐nitro benzaldehyde, m‐nitro benzaldehyde, p‐methoxy benzaldehyde and cinnamaldehyde), two hydrocarbons (viz. (anthracene and phenanthrene)) and one aromatic and one cyclic alcohol (cyclohexanol and benzyl alcohol) by 50% H2O2. The presence of traces (substrate: catalyst ratio equal to 1:62500 to 1:1961) of the chlorides of iridium(III), rhodium(III) and palladium(II) catalyze these oxidations, resulting in good to excellent yields. It was observed that in most of the cases palladium(II) chloride is the most efficient catalyst. Conditions for the highest and most economical yields were obtained. Deviation from the optimum conditions decreases the yields. Oxidation in aromatic aldehydes is selective at the aldehydeic group only and other groups remain unaffected. This new, simple and economical method, which is environmentally safe, also requires less time. Reactive species of catalysts, existing in the reaction mixture are also discussed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
87.
In this paper we develop the fundamental elements and results of a new theory of regular functions of one quaternionic variable. The theory we describe follows a classical idea of Cullen, but we use a more geometric formulation to show that it is possible to build a rather complete theory. Our theory allows us to extend some important results for polynomials in the quaternionic variable to the case of power series. 相似文献
88.
89.
L.B.Magalas 《物理学进展》2006,26(3):258-276
本文广泛地收集了有关内耗,力学谱,超声衰减方面的专著及会议文集。反映了20世纪在此领域的英文,俄文出版的书籍。也列出了历次国际会议及前苏联,乌克兰,中国的国内会议。文中包括了点缺陷,电,声子,位错,晶界,电畴等诸方面在内的内耗与力学谱工作。 相似文献
90.