全文获取类型
收费全文 | 543篇 |
免费 | 30篇 |
国内免费 | 1篇 |
专业分类
化学 | 422篇 |
晶体学 | 11篇 |
力学 | 7篇 |
数学 | 74篇 |
物理学 | 60篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 26篇 |
2021年 | 23篇 |
2020年 | 27篇 |
2019年 | 32篇 |
2018年 | 20篇 |
2017年 | 19篇 |
2016年 | 38篇 |
2015年 | 19篇 |
2014年 | 20篇 |
2013年 | 56篇 |
2012年 | 47篇 |
2011年 | 33篇 |
2010年 | 29篇 |
2009年 | 18篇 |
2008年 | 18篇 |
2007年 | 40篇 |
2006年 | 13篇 |
2005年 | 16篇 |
2004年 | 18篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有574条查询结果,搜索用时 62 毫秒
141.
Fatma Arslan Martin Behrendt Werner Ernst Eberhard Finckh Gunther Greb Friedrich Gumbmann Martin Haller Stefan Hofmann Ralf Karschnick Matthias Klein Wolfgang Kretschmer Jochen Mackiol Gerhard Morgenroth Christian Pagels Markus Schleicher 《Angewandte Chemie (International ed. in English)》1995,34(2):183-186
142.
Reaction of ethyl 2‐diazo‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carboxylate 1 with 3‐iminobutyronitrile 2 gave the hydrazone derivative 3 . The reactivity of the latter product toward a variety of chemical reagents as well as the biological activity of the newly synthesized products were studied. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:403–412, 2000 相似文献
143.
Cemil Aydoğan Fatma Yılmaz Duygu Çimen Lokman Uzun Adil Denizli 《Electrophoresis》2013,34(13):1908-1914
A new type of polymethacrylate‐based monolithic column with chiral stationary phase was prepared for the enantioseparation of aromatic amino acids, namely d ,l ‐phenylalanine, d ,l ‐tyrosine, and d ,l ‐tryptophan by CEC. The monolithic column was prepared by in situ polymerization of butyl methacrylate (BMA), N‐methacryloyl‐l ‐histidine methyl ester (MAH), and ethylene dimethacrylate (EDMA) in the presence of porogens. The porogen mixture included DMF and phosphate buffer. MAH was used as a chiral selector. FTIR spectrum of the polymethacrylate‐based monolith showed that MAH was incorporated into the polymeric structure via in situ polymerization. Some experimental parameters including pH, concentration of the mobile phase, and MAH concentration with regard to the chiral CEC separation were investigated. Single enantiomers and enantiomer mixtures of the amino acids were separately injected into the monolithic column. It was observed that l ‐enantiomers of aromatic amino acids migrated before d ‐enantiomers. The reversal enantiomer migration order for tryptophan was observed upon changing of pH. Using the chiral monolithic column (100 μm id and 375 μm od), the best chiral separation was performed in 35:65% ACN/phosphate buffer (pH 8.0, 10 mM) with an applied voltage of 12 kV in CEC. SEM images showed that the chiral monolithic column has a continuous polymeric skeleton and large through‐pore structure. 相似文献
144.
Fatma Djouani Yaël Israëli Lawrence Frezet Agns Rivaton Roger A. Lessard Michle Bolte 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1317-1325
The photochemical behavior of dichromated poly(vinyl alcohol) films has been analyzed upon exposure at 365 nm in relationship with the performances of holograms recorded in such photosensitive materials. The evolution of both involved species, poly(vinyl alcohol) and chromium, has been quantified by the implementation of an innovative approach. This approach combines the monitoring of the structural modification of the polymeric matrix and the fate of the various chromium species. For the first time, it has been established that chromium(V) not only is an indicator of the hologram quality, as previously assessed, but also appears to be responsible for the crosslinking implied in the hologram formation. Actually, the crosslinking has been proved to proceed through coordination bonds around chromium(V), which acts as a bridge between the polymeric chains. The role played by the ammonium cations in the hologram quality has also been elucidated. The improvement brought by ammonium dichromate with respect to potassium dichromate involves amide groups resulting from poly(vinyl alcohol) phototransformation. These groups provide additional chelating sites for chromium(V), leading to an increase in the matrix crosslinking. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1317–1325, 2006 相似文献
145.
Fatma Altunbulak 《Journal of Pure and Applied Algebra》2007,208(1):15-28
We give an alternative proof to a theorem of Carlson [J.F. Carlson, Cohomology and induction from elementary abelian subgroups, Quart. J. Math. 51 (2000) 169-181] which states that if G is a finite group and k is a field of characteristic p, then any kG-module is a direct summand of a module which has a filtration whose sections are induced from elementary abelian p-subgroups of G. We also prove two new theorems which are closely related to Carlson’s theorem. 相似文献
146.
Fatma Fakhfakh 《Journal of Mathematical Analysis and Applications》2008,347(1):235-242
In the present paper we investigate the stability of closed densely defined semi-Browder operators under operator perturbations that belong to a perturbation class related to compact operators. Furthermore, we apply the obtained results to give a characterization and to study the stability of Browder's essential approximate point spectrum and Browder's essential defect spectrum. 相似文献
147.
Evidence is presented which demonstrates that 13C-NMR. spectroscopy can be used with confidence in evaluating the configuration of R1R2CHOH centers at C(6) and C(8) of iridoid glucosides. 相似文献
148.
149.
Wajdi Michael Zoghaib Carlo Carboni Fatma A. Kashoub Juhaina S. Al-Rushidi Buthaina Y. Al-Jabri Aysha S. Al-Alawi 《Molecular Crystals and Liquid Crystals》2018,666(1):54-64
The synthesis and characterization of a series of five chiral fluorinated low molar mass (bifurcated tail) organosiloxane materials is presented. The mesogenic moiety is similar to that in the TSiKN65F mesogen reported by Naciri et al., which displays a de Vries-type SmA* phase. The one parameter varied across the series reported herein is the length of the alkyl chain linking the mesogen's core to the bifurcated siloxane tail. One of the five materials displays a de Vries SmC* phase upon cooling from SmA*. 相似文献
150.
A simple, efficient, and ecofriendly one-pot method has been reported for the synthesis of polyhydroquinolines in excellent yield using nucleophilic heterocyclic carbene as catalyst. The generalized approach is the Hantzsch four-component reaction of aromatic aldehyde, ethyl acetoacetate, cyclic 1,3-diketone, and ammonium acetate. 相似文献