全文获取类型
收费全文 | 12387篇 |
免费 | 1036篇 |
国内免费 | 1202篇 |
专业分类
化学 | 8612篇 |
晶体学 | 250篇 |
力学 | 527篇 |
综合类 | 101篇 |
数学 | 1347篇 |
物理学 | 3788篇 |
出版年
2024年 | 13篇 |
2023年 | 74篇 |
2022年 | 318篇 |
2021年 | 348篇 |
2020年 | 299篇 |
2019年 | 282篇 |
2018年 | 296篇 |
2017年 | 296篇 |
2016年 | 378篇 |
2015年 | 428篇 |
2014年 | 517篇 |
2013年 | 854篇 |
2012年 | 983篇 |
2011年 | 1094篇 |
2010年 | 760篇 |
2009年 | 668篇 |
2008年 | 929篇 |
2007年 | 847篇 |
2006年 | 761篇 |
2005年 | 722篇 |
2004年 | 595篇 |
2003年 | 444篇 |
2002年 | 463篇 |
2001年 | 379篇 |
2000年 | 358篇 |
1999年 | 221篇 |
1998年 | 104篇 |
1997年 | 115篇 |
1996年 | 134篇 |
1995年 | 118篇 |
1994年 | 119篇 |
1993年 | 83篇 |
1992年 | 78篇 |
1991年 | 61篇 |
1990年 | 65篇 |
1989年 | 57篇 |
1988年 | 36篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 33篇 |
1984年 | 27篇 |
1983年 | 25篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 20篇 |
1979年 | 19篇 |
1978年 | 20篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1975年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Green MM Park JW Sato T Teramoto A Lifson S Selinger RL Selinger JV 《Angewandte Chemie (International ed. in English)》1999,38(21):3138-3154
Cooperative phenomena, described by one-dimensional statistical physical methods, are observed between the enantiomeric characteristics of monomeric materials and the polymers they produce. The effect of minute energies associated with this amplified chirality, although currently not interpretable, can be easily measured. Nonlinear relationships between enantiomeric excess or enantiomeric content and polymer properties may offer the possibility of developing chiral catalysts and chiral chromatographic materials in which the burden of large enantiomeric excess or content may be considerably alleviated. New approaches to information and sensor technology may become possible. 相似文献
962.
The structure preserving rank reduction problem arises in many important applications. The singular value decomposition (SVD), while giving the closest low rank approximation to a given matrix in matrix L
2 norm and Frobenius norm, may not be appropriate for these applications since it does not preserve the given structure. We present a new method for structure preserving low rank approximation of a matrix, which is based on Structured Total Least Norm (STLN). The STLN is an efficient method for obtaining an approximate solution to an overdetermined linear system AX B, preserving the given linear structure in the perturbation [E F] such that (A + E)X = B + F. The approximate solution can be obtained to minimize the perturbation [E F] in the L
p norm, where p = 1, 2, or . An algorithm is described for Hankel structure preserving low rank approximation using STLN with L
p norm. Computational results are presented, which show performances of the STLN based method for L
1 and L
2 norms for reduced rank approximation for Hankel matrices. 相似文献
963.
红外光谱法快速测定润滑油添加剂 总被引:6,自引:0,他引:6
利用PE-FTIR红外光谱仪及PE公司“Quant”计算机软件,测定润滑油添加剂单剂与复合剂含量,实际测定了15W/40SE、15/30 SE/CD、15/W40CD、15W/30CC油品试样。测量范围为0.2% ̄90%,测定相对误差小于10%。 相似文献
964.
冻干过程中升华界面温度测量方法的研究 总被引:1,自引:0,他引:1
压力测温技术是基于在平衡状态下,冰晶温度与其饱和蒸汽压为单值函数这一基本规律,在升华干燥过程中,突然中断从冻干室流向冷阱的水蒸汽流,通过测量冻干室内压力回升情况去推算升华界面温度的一种非接触式测温方法。与热电偶或热敏电阻测温相比,压力测温技术即不破坏冻干样品的结构,又能够较为准确地反应出移动升华界面的温度,并能判断升华干燥过程终点。文中分析了升华界面温度测量的意义与困难,建立了压力测温技术的数学模型与分析方法,并通过实验研究了压力测温技术。 相似文献
965.
Tae Oan Ahn Jung Ho Kim Han Mo Jeong Sang Won Lee Lee Soon Park 《Journal of Polymer Science.Polymer Physics》1994,32(1):21-28
The compatibilizing effect of polyarylate-polystyrene (PAR-PS) block copolymer prepared from macroazo initiator was examined in polyarylate/polystyrene blends from the view-points of morphology, density, and thermal, mechanical, and rheological properties. PARPS block copolymer enhanced the mutual dissolution of the homopolymers. Reduced dispersed-domain size and increased density showed the efficiency of the block copolymer as a compatibilizing agent. Results from mechanical and rheological properties could also be explained by the compatibilizing effect of PAR-PS block copolymer in the blends. © 1994 John Wiley & Sons, Inc. 相似文献
966.
Policies and criteria for the accreditation of testing laboratories in Korea are reviewed according to the laws and regulations within the organizational framework. According to the Weights and Measures Act, the administrator of Korean Industrial Advancement Administration (KIAA) may accredit qualified testing laboratories in Korea. Criteria, procedures, and surveillance of accredited laboratories are specified in the Enforcement Regulation of the Weights and Measures Act drawn up by the Ministry of Trade, Industry, and Energy. Further detailed accreditation criteria and processes are prescribed in the Operation Guideline for the Accreditation of Testing Laboratories prepared by the KIAA. The Korean Laboratory Accreditation Scheme (KOLAS) of the KIAA is the authorized representative institution for the accreditation of testing laboratories in compliance with the ISO Guides 25/58 and the Operation Guideline for the Accreditation of Testing Laboratories. Finally, the current status of accredited laboratories in Korea is briefly described. 相似文献
967.
Ohne Zusammenfassung 相似文献
968.
Randall C. McFarlane Park M. Reilly Kenneth F. O'driscoll 《Journal of polymer science. Part A, Polymer chemistry》1980,18(1):251-257
Six recently proposed methods for analyzing copolymerization composition data have been compared to a nonlinear least-squares analysis to ascertain the precision of the six methods in determining reactivity ratios. Data used were simulated for five hypothetical monomer pairs with three different types of experiment design and contained error structures similar to those observed experimentally. The results of the comparisons suggest that retrospective analyses of existing copolymerization data should only be done with a nonlinear least-squares analysis. For new data, the design of experiments is of great importance, and when done properly allows the use of some of the linear least-squares methods of analysis. 相似文献
969.
970.