全文获取类型
收费全文 | 71236篇 |
免费 | 10467篇 |
国内免费 | 1406篇 |
专业分类
化学 | 60356篇 |
晶体学 | 487篇 |
力学 | 1240篇 |
综合类 | 1篇 |
数学 | 8210篇 |
物理学 | 12815篇 |
出版年
2023年 | 208篇 |
2021年 | 443篇 |
2020年 | 1695篇 |
2019年 | 2900篇 |
2018年 | 1412篇 |
2017年 | 1049篇 |
2016年 | 4224篇 |
2015年 | 4218篇 |
2014年 | 4234篇 |
2013年 | 5917篇 |
2012年 | 4357篇 |
2011年 | 3947篇 |
2010年 | 3674篇 |
2009年 | 3491篇 |
2008年 | 4067篇 |
2007年 | 3402篇 |
2006年 | 2936篇 |
2005年 | 2973篇 |
2004年 | 2493篇 |
2003年 | 2222篇 |
2002年 | 2836篇 |
2001年 | 2083篇 |
2000年 | 1924篇 |
1999年 | 801篇 |
1998年 | 447篇 |
1997年 | 433篇 |
1996年 | 532篇 |
1995年 | 476篇 |
1994年 | 489篇 |
1993年 | 566篇 |
1992年 | 472篇 |
1991年 | 357篇 |
1990年 | 394篇 |
1989年 | 324篇 |
1988年 | 342篇 |
1987年 | 334篇 |
1986年 | 311篇 |
1985年 | 496篇 |
1984年 | 473篇 |
1983年 | 435篇 |
1982年 | 442篇 |
1981年 | 446篇 |
1980年 | 429篇 |
1979年 | 377篇 |
1978年 | 419篇 |
1977年 | 402篇 |
1976年 | 349篇 |
1975年 | 330篇 |
1974年 | 318篇 |
1973年 | 318篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
Demixing during film casting of blends of polystyrene, polymethylmethacrylate, and a symmetric diblock copolymer of styrene and methylmethacrylate is discussed. The concentration fluctuations in the homogeneous solutions were calculated in mean field approximation. The structures in the homogeneous and demixed solutions and in the dry films were measured by small-angle x-ray scattering, and the morphologies of the dry films were characterized by transmission electron microscopy. The structure of the dry blends is evidently already pre-formed in solution. 相似文献
56.
J. Maul I. Strachnov S. Karpuk P. Bernhard A. Oelsner G. Schönhense G. Huber 《Applied Physics A: Materials Science & Processing》2006,82(1):43-47
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De 相似文献
57.
58.
59.
Wolfram Bremser Roland Becker Heinrich Kipphardt Petra Lehnik-Habrink Ulrich Panne Antje Töpfer 《Accreditation and quality assurance》2006,11(10):489-495
ISO Guide 35 deals with RM stability issues and scrutinizes the evaluation of stability testing results under the assumption that either there is no trend at all (a rather rare situation), or any observed deterministic change is insignificant and thus can be neglected. However, market demands for reliable reference materials are obviously not limited to stable or at least seemingly stable materials. In many analytical applications, analytes and measurands under consideration are known, or at least suspected, to be unstable on time scales that may vary widely from measurand to measurand. The Federal Institute for Materials Research and Testing (BAM) has developed (and successfully uses) an integrated approach in its certification practice. The approach is based on an initial stability study and subsequent post-certification monitoring. Data evaluation is model-based and takes advantage of all information collected in the stability testing scheme(s). It thus allows one to deal with any kind of instability observed, to assess limiting time intervals at any stress condition in the range tested, to estimate a final expiry date for materials with detected instabilities or the maximum admissible re-testing interval for seemingly stable materials, and to assess maximum admissible stress loads during delivery of the material to the customer. The article describes (and exemplifies) typical study layout, the model selection, and the integrated data assessment. 相似文献
60.
Abstract Under a suitable ellipticity condition, we show that classical SG-pseudodifferential operators of nonnegative order possess
complex powers. We show that the powers are again classical and derive an explicit formula for all homogeneous components.
Keywords: Complex power, Weighted symbols, Noncompact manifolds 相似文献