全文获取类型
收费全文 | 3940篇 |
免费 | 76篇 |
国内免费 | 33篇 |
专业分类
化学 | 2631篇 |
晶体学 | 31篇 |
力学 | 202篇 |
数学 | 656篇 |
物理学 | 529篇 |
出版年
2021年 | 30篇 |
2020年 | 33篇 |
2019年 | 25篇 |
2018年 | 41篇 |
2017年 | 24篇 |
2016年 | 74篇 |
2015年 | 56篇 |
2014年 | 66篇 |
2013年 | 212篇 |
2012年 | 126篇 |
2011年 | 186篇 |
2010年 | 105篇 |
2009年 | 104篇 |
2008年 | 151篇 |
2007年 | 161篇 |
2006年 | 165篇 |
2005年 | 182篇 |
2004年 | 193篇 |
2003年 | 185篇 |
2002年 | 172篇 |
2001年 | 78篇 |
2000年 | 85篇 |
1999年 | 49篇 |
1998年 | 42篇 |
1997年 | 46篇 |
1996年 | 67篇 |
1995年 | 54篇 |
1994年 | 55篇 |
1993年 | 53篇 |
1992年 | 45篇 |
1991年 | 46篇 |
1990年 | 45篇 |
1989年 | 47篇 |
1988年 | 43篇 |
1987年 | 39篇 |
1986年 | 38篇 |
1985年 | 63篇 |
1984年 | 71篇 |
1983年 | 57篇 |
1982年 | 68篇 |
1981年 | 61篇 |
1980年 | 73篇 |
1979年 | 66篇 |
1978年 | 56篇 |
1977年 | 51篇 |
1976年 | 43篇 |
1975年 | 48篇 |
1974年 | 57篇 |
1973年 | 38篇 |
1972年 | 34篇 |
排序方式: 共有4049条查询结果,搜索用时 15 毫秒
1.
Mathieu Boiret Anna de Juan Nathalie Gorretta Yves-Michel Ginot Jean-Michel Roger 《Analytica chimica acta》2015
Raman chemical imaging provides chemical and spatial information about pharmaceutical drug product. By using resolution methods on acquired spectra, the objective is to calculate pure spectra and distribution maps of image compounds. With multivariate curve resolution-alternating least squares, constraints are used to improve the performance of the resolution and to decrease the ambiguity linked to the final solution. Non negativity and spatial local rank constraints have been identified as the most powerful constraints to be used. 相似文献
2.
3.
4.
5.
Aric Opdahl Roger A. Phillips Gabor A. Somorjai 《Journal of Polymer Science.Polymer Physics》2004,42(3):421-432
The surface compositions and morphologies of melt‐quenched blends of isotactic polypropylene (iPP) with aspecific poly(ethylene‐co‐propylene) rubber (aEPR) were characterized by atomic force microscopy, optical microscopy, and X‐ray photoelectron spectroscopy. The surface morphologies and compositions formed in the melt are frozen‐in by crystallization of the iPP component and, depending on the processing conditions, are enriched in iPP or aEPR or contain a phase‐separated mix of iPP and aEPR. Enrichment of iPP is observed for blends melted in open air, in agreement with earlier work showing the high surface activity of atactic polypropylene at open interfaces. Surface segregation of iPP is suppressed at confined interfaces. Blends melt‐pressed between hydrophilic and hydrophobic substrates have phase‐separated iPP and aEPR domains present at the surface, which grow in size as the melt time increases. Surface enrichment of aEPR is observed after exposing melt‐pressed blends to n‐hexane vapor, which preferentially solvates aEPR and draws it to the surface. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 421–432, 2004 相似文献
6.
The phase behavior of binary blends of poly(ether ether ketone) (PEEK), sulfonated PEEK, and sulfamidated PEEK with aromatic polyimides is reported. PEEK was determined to be immiscible with a poly(amide imide) (TORLON 4000T). Blends of sulfonated and sulfamidated PEEK with this poly(amide imide), however, are reported here to be miscible in all proportions. Blends of sulfonated PEEK and a poly(ether imide) (ULTEM 1000) are also reported to be miscible. Spectroscopic investigations of the intermolecular interactions suggest that formation of electron donoracceptor complexes between the sulfonated/sulfamidated phenylene rings of the PEEKs and the n-phenylene units of the polyimides are responsible for this miscibility. © 1993 John Wiley & Sons, Inc. 相似文献
7.
Roger Alberto 《Journal of organometallic chemistry》2007,692(6):1179-1186
This article will emphasize the particular role of organometallic radiopharmaceutical chemistry, namely the need for syntheses from water and the emerging implications for other (bio)organometallic fields. After some basic insights into the different directions of bioorganometallic chemistry, some facets of the [M(CO)3]+ (M = Tc, Re) moiety are reviewed and discussed in the respective context. The mechanism for the synthesis of [M(OH2)3(CO)3]+ which is still little understood, will be touched. The formation of additional M-C bonds is exemplified with cyclopentadienyl chemistry, the potential impact on targeted molecular imaging with the labelling of amino acids and the reactivity towards essential biomolecules such as guanine is shown. Future perspectives and implications for organometallic radiopharmaceutical chemistry will close this article. 相似文献
8.
9.
Roger Bielawski 《Proceedings of the American Mathematical Society》2004,132(9):2679-2682
We prove existence and regularity of entire solutions to Monge-Ampère equations invariant under an irreducible action of a compact Lie group.
10.