全文获取类型
收费全文 | 541篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
化学 | 430篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 70篇 |
物理学 | 43篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 13篇 |
2015年 | 15篇 |
2014年 | 12篇 |
2013年 | 29篇 |
2012年 | 20篇 |
2011年 | 46篇 |
2010年 | 23篇 |
2009年 | 21篇 |
2008年 | 32篇 |
2007年 | 25篇 |
2006年 | 24篇 |
2005年 | 22篇 |
2004年 | 18篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 18篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1978年 | 2篇 |
1974年 | 4篇 |
1970年 | 6篇 |
1968年 | 2篇 |
1914年 | 1篇 |
1913年 | 3篇 |
1911年 | 1篇 |
1909年 | 1篇 |
排序方式: 共有555条查询结果,搜索用时 15 毫秒
91.
Norbert Kuhn Riad Fawzi Martin Grathwohl Heike Kotowski Manfred Steimann 《无机化学与普通化学杂志》1998,624(12):1937-1939
Synthesis and Coordination of 2-Acetylimino-1,3-dimethylimidazoline. The Crystal Structure of [Cu4I4(C7H11N3O)2] 2-Acetylimino–1,3-dimethylimidazoline ( 2 , ImNAc) obtained from 1,3-dimethyl-2-iminoimidazoline ( 1 ) and acetyl chloride forms with CuI the stepped cubane type complex [Cu4I4(ImNAc)2] ( 3 ); the X-ray structure of 3 is reported. 相似文献
92.
Observation time-dependent self-diffusion coefficients can be used to obtain microstructural information of porous media. This paper presents two different kinds of Monte Carlo simulations of the self diffusion process of fluids like water in porous systems, a lattice-free method and a lattice-based method. The results for simple porous media model geometries agree well with each other and with published analytical as well as semi-analytical equations. The use of these equations, which are important for the interpretation of Pulsed Field Gradient-Nuclear Magnetic Resonance (PFG-NMR) time-dependent diffusion data with respect to properties of porous media, is discussed. 相似文献
93.
Spiral surface growth is well understood in the limit where motion of the spiral ridge is controlled by the local supersaturation of adatoms in its surrounding. In liquid epitaxial growth, however, spirals can form governed by both, transport of heat as well as solute. We propose for the first time a two-scale model of epitaxial growth which takes into account all of these transport processes. This new model assumes a separation of length scales for the transport of heat compared to that of the solutal field. It allows for the first time numerical simulations of extended surface regions by at the same time taking into account microstructure evolution and microstructure interaction. We apply this model successfully to extend the scaling relation for the step spacing given by the BCF theory [Phil. Trans. R. Soc. London, Ser. A 243, 299 (1951)] to microstructure evolution governed by heat and solute diffusion. Further applications to understand the mechanisms and consequences of spiral interaction at epitaxial surfaces, in particular the resulting morphology transitions, are discussed. 相似文献
94.
95.
Initially motivated by the commercial need for cheaper and environmentally friendly luminescent materials for application in fluorescent lamps and cathode ray tubes, the search for new matrices for optically active species has penetrated a scope far beyond “classical” solid-state materials. Porous matrices with voids ranging from the nano-to the microscale have become the subject of recent investigations. Crystalline, amorphous, organomorphous, nanosized matrices and matrices, which are amorphous on the atomic level but have a translational superstructure on the microscale (zeolites, sol-gel materials, polymers, nanoparticles and photonic crystals), are addressed. The optical technologies covered in this research range from mercury free discharge lamps, plasma displays, organic and polymeric light emitting diodes, and novel laser materials to biophotonics and the new generation of white emitting AlGaN solid-state light emitting diodes (LEDs). Due to their specific properties (e.g., high quantum yields, narrow line emission), rare-earth ions are indispensable components of these approaches, be it in the nanoscaling zeolites, sol-gel matrices, or as the active component in optically functional polymers. Optical properties of hybrid materials composed of either rare-earth ions as such, their complexes, or nanoparticles in these matrices, with potential application in the fields mentioned, will form the scope of the present report. 相似文献
96.
97.
The monosulfoxide of cis-dialkylmercaptoethylene and the β-alkylmercapto acrylnitrile deliver on deprotonation with tert.-butyllithium almost exclusively α-deprotonated species. According to reactions with electrophiles these functionally substituted vinyllithium derivatives are configurationally labile. 相似文献
98.
H. Läpple H. Todt H. Späth A. Schub F. Isenbart T. Talmon H. -D. Heike P. Schaltegger H. Wiggert G. Gallus T. Gal 《Mathematical Methods of Operations Research》1974,18(6):B256-B263
Ohne Zusammenfassung 相似文献
99.
Becker G Brombach H Horner ST Niecke E Schwarz W Streubel R Würthwein EU 《Inorganic chemistry》2005,44(9):3080-3086
2-Isopropyl(trimethylsilyl)amino-1lambda3-phosphaalkyne 1 reacts with potassium tert-butoxide to form potassium 1-isopropyl-1-aza-3lambda3-phospha-3-allenide (2). This compound was structurally characterized as the corresponding 18-crown-6 ether complex 3. The molecular structure of 1 was also determined in order to compare the bonding situation in the anion and the neutral lambda3-phosphaalkyne. Compound 3 contains a nitrogen-carbon-phosphorus group for which the parameters were shown by X-ray structural analysis and quantum chemical calculations to lie between the extrema N-C[triple bond]P and N=C=P, suggesting reactivity typical of an ambident anion. This is indeed the case, as subsequent reaction of 2 with chlorotrimethylsilane at nitrogen regenerates the lambda3-phosphaalkyne 1; with chlorotriphenylsilane the new derivative 4 is formed. In contrast, chlorotrimethylstannane reacts at phosphorus, giving the 1-aza-3lambda3-phosphaallene isopropyliminomethylidene(trimethylstannyl)phosphane 5. 相似文献
100.