全文获取类型
收费全文 | 53443篇 |
免费 | 3497篇 |
国内免费 | 2211篇 |
专业分类
化学 | 30471篇 |
晶体学 | 852篇 |
力学 | 2615篇 |
综合类 | 105篇 |
数学 | 5371篇 |
物理学 | 19737篇 |
出版年
2023年 | 458篇 |
2022年 | 761篇 |
2021年 | 976篇 |
2020年 | 1043篇 |
2019年 | 1025篇 |
2018年 | 1139篇 |
2017年 | 1005篇 |
2016年 | 1542篇 |
2015年 | 1215篇 |
2014年 | 1685篇 |
2013年 | 2821篇 |
2012年 | 3030篇 |
2011年 | 3309篇 |
2010年 | 2357篇 |
2009年 | 2292篇 |
2008年 | 2579篇 |
2007年 | 2497篇 |
2006年 | 2293篇 |
2005年 | 2024篇 |
2004年 | 1725篇 |
2003年 | 1489篇 |
2002年 | 1427篇 |
2001年 | 1724篇 |
2000年 | 1309篇 |
1999年 | 1207篇 |
1998年 | 948篇 |
1997年 | 907篇 |
1996年 | 823篇 |
1995年 | 743篇 |
1994年 | 664篇 |
1993年 | 586篇 |
1992年 | 615篇 |
1991年 | 599篇 |
1990年 | 610篇 |
1989年 | 530篇 |
1988年 | 520篇 |
1987年 | 481篇 |
1986年 | 432篇 |
1985年 | 498篇 |
1984年 | 499篇 |
1983年 | 372篇 |
1982年 | 411篇 |
1981年 | 393篇 |
1980年 | 327篇 |
1979年 | 402篇 |
1978年 | 378篇 |
1977年 | 397篇 |
1976年 | 391篇 |
1975年 | 342篇 |
1973年 | 340篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
微模塑法制备PMMA/SiO2二氧化硅杂化材料微结构 总被引:1,自引:0,他引:1
以摩尔比为 1∶1的甲基丙烯酸甲酯 (MMA)、甲基丙烯酸 (3 三乙氧基硅烷基 )丙酯 (ESMA)单体、0 .2 %(单体总量的质量分数 )的偶氮二异丁腈AIBN引发剂和四氢呋喃 (THF)溶剂 ,及 2 0 % (总质量分数 )的正硅酸乙酯TEOS合成出PMMA/SiO2 有机 无机杂化的杂化溶胶 .将溶胶在洗净的普通光学玻璃基片表面甩膜 .利用软刻蚀中的微模塑法 ,把有机硅弹性印章复制有精细图纹一面轻放在杂化溶胶膜上进行微模塑 ,外加 1N压力于12 0℃下处理 2h使溶胶凝胶化 .印章剥离后在基片表面就形成了PMMA/SiO2 有机 无机杂化材料的微图纹结构 .从微图纹的光学显微镜照片可以看出微模塑方法制备杂化材料复制的图纹精细度高 ,操作简单易行 ,是一类比较理想的微细图纹结构加工的方法 . 相似文献
122.
123.
We study condensation of ethanol-hexanol vapour by numerical solution of kinetic equations. The number of droplets formed
in unit volume is computed within self-consistent classical model. It is shown that formation of ethanol-rich droplets prevails
at the initial stage of nucleation process, but in the stationary state formation of droplets near the saddle point (on cluster
formation energy surface) plays the dominant role.
Presented at the 6th Joint Seminar “Development of Materials Science in Research and Education”, Karlštejn, Czech Republic,
17–19 September 1996.
This work was supported by Grant No. A1010615 of the Grant Agency of the Academy of Sciences of the Czech Republic. 相似文献
124.
1.RecentlytherearesomegoodliteraturesconcerningtheuniquenesoflimitcyclesforgeneralizedLiénardsystemsx=φ(y)-F(x),y=-g(x),(F(x)... 相似文献
125.
126.
127.
The purpose of this paper is to give the Reid ``Roundabout Theorem' for quadratic functionals with general boundary conditions.
In particular, we describe the so-called coupled point and regularity condition introduced in [16] in terms of Riccati equation
solutions.
Accepted 27 February 1996 相似文献
128.
129.
Some of the motivations for as well as the main points of the quantization of the Nappi-Witten string in the light-cone gauge are reviewed. 相似文献
130.
Benjamin S. Hsiao Rong-Ming Ho Stephen Z. D. Cheng 《Journal of Polymer Science.Polymer Physics》1995,33(17):2439-2447
Unique crystallization and melting behavior in poly(aryl ether ketone ketone) containing alternated terephthalic and isophthalic moieties were studied by time-resolved synchrotron x-ray methods. Recently, this material has been shown to exhibit three polymorphs (forms I, II, and III). In this work, we further investigated their distinctive thermal properties and found that form I is the dominating and the most thermally stable phase while form II is favored by fast nucleation conditions and is the least stable phase. On the other hand, form III represents a minor intermediate phase that usually coexists with form I and can be transferred from form II and to form I. Structural and morphological changes in form I have been followed by simultaneous wide-angle x-ray diffraction (WAXD)/small-angle x-ray scattering (SAXS) measurements during cold- or melt-crystallization and subsequent melting. In all cases, a larger dimensional change was found in the crystallographic a-axis than the b-axis during heating and cooling. This may be due to the greater lateral stress variation with respect to temperature along the a direction of the primary lamellae which is induced by either the formation of secondary lamellae or the preferential chain-folding direction in poly(aryl ether ketone ketone)s. During the phase transitions of form II ← III in the cold-crystallized specimen and form III ← I in the melt-crystallized samples, lamellar variables (long period, lamellar thickness, and invariant) obtained from SAXS remain almost constant. This indicates that the density distribution in the long spacing is independent of the melting in form II or III. For melt-crystallization, the corresponding changes in unit-cell dimensions and lamellar morphology during the annealing-induced low endotherm are most consistent with the argument that these changes are due to the melting of thin lamellar population. © 1995 John Wiley & Sons, Inc. 相似文献