全文获取类型
收费全文 | 652篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
化学 | 506篇 |
晶体学 | 6篇 |
力学 | 6篇 |
数学 | 100篇 |
物理学 | 52篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 8篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 16篇 |
2014年 | 15篇 |
2013年 | 30篇 |
2012年 | 31篇 |
2011年 | 43篇 |
2010年 | 25篇 |
2009年 | 25篇 |
2008年 | 40篇 |
2007年 | 38篇 |
2006年 | 32篇 |
2005年 | 37篇 |
2004年 | 26篇 |
2003年 | 27篇 |
2002年 | 33篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 18篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1973年 | 4篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有670条查询结果,搜索用时 15 毫秒
111.
112.
Peter Nockemann Dr. Ben Thijs Dr. Kyra Lunstroot Dr. Tatjana N. Parac‐Vogt Prof. Dr. Christiane Görller‐Walrand Prof. Dr. Koen Binnemans Prof. Dr. Kristof Van Hecke Dr. Luc Van Meervelt Prof. Dr. Sergey Nikitenko John Daniels Dr. Christoph Hennig Dr. Rik Van Deun Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(6):1449-1461
The dissolution process of metal complexes in ionic liquids was investigated by a multiple‐technique approach to reveal the solvate species of the metal in solution. The task‐specific ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]) is able to dissolve stoichiometric amounts of the oxides of the rare‐earth elements. The crystal structures of the compounds [Eu2(bet)8(H2O)4][Tf2N]6, [Eu2(bet)8(H2O)2][Tf2N]6?2H2O, and [Y2(bet)6(H2O)4][Tf2N]6 were found to consist of dimers. These rare‐earth complexes are well soluble in the ionic liquids [Hbet][Tf2N] and [C4mim][Tf2N] (C4mim=1‐butyl‐3‐methylimidazolium). The speciation of the metal complexes after dissolution in these ionic liquids was investigated by luminescence spectroscopy, 1H, 13C, and 89Y NMR spectroscopy, and by the synchrotron techniques EXAFS (extended X‐ray absorption fine structure) and HEXS (high‐energy X‐ray scattering). The combination of these complementary analytical techniques reveals that the cationic dimers decompose into monomers after dissolution of the complexes in the ionic liquids. Deeper insight into the solution processes of metal compounds is desirable for applications of ionic liquids in the field of electrochemistry, catalysis, and materials chemistry. 相似文献
113.
Stenger Fernanda Cristina Cechinel-Filho Valdir Meyre-Silva Christiane Bresolin Tania Mari Belle Rodrigues Clvis Antonio 《Chromatographia》2009,69(2):183-187
Chitosan was modified with lauroyl chloride to prepare a solid support for the application of matrix solid-phase dispersion (MSPD) for the extraction of flavonoids from the medicinal plant Aleurites moluccana. The laurylchitosan prepared by the homogenous and heterogeneous method, was characterized using analytical methods such as potentiometric titration and infrared spectroscopy. The hydrophobic properties were studied by naphthalene incorporation. The MSPD performance was evaluated by extraction of swertisin and 2″-O-rhamnosylswertisin from the leaves of A. moluccana. 相似文献
114.
Patrick Guertler Vijay Paul Christiane Albrecht Heinrich H. D. Meyer 《Analytical and bioanalytical chemistry》2009,393(6-7):1629-1638
To address food safety concerns of the public regarding the potential transfer of recombinant DNA (cry1Ab) and protein (Cry1Ab) into the milk of cows fed genetically modified maize (MON810), a highly specific and sensitive quantitative real-time PCR (qPCR) and an ELISA were developed for monitoring suspicious presence of novel DNA and Cry1Ab protein in bovine milk. The developed assays were validated according to the assay validation criteria specified in the European Commission Decision 2002/657/EC. The detection limit and detection capability of the qPCR and ELISA were 100 copies of cry1Ab μL?1 milk and 0.4 ng mL?1 Cry1Ab, respectively. Recovery rates of 84.9% (DNA) and 97% (protein) and low (<15%) imprecision revealed the reliable and accurate estimations. A specific qPCR amplification and use of a specific antibody in ELISA ascertained the high specificity of the assays. Using these assays for 90 milk samples collected from cows fed either transgenic (n?=?8) or non-transgenic (n?=?7) rations for 6 months, neither cry1Ab nor Cry1Ab protein were detected in any analyzed sample at the assay detection limits. Figure
Schematic formats for quantitative real-time PCR and ELISA for the quantification of cry1Ab DNA and Cry1Ab protein 相似文献
115.
Christiane Tretter 《Journal of Functional Analysis》2009,256(11):3806-3829
In this paper we establish a new analytic enclosure for the spectrum of unbounded linear operators A admitting a block operator matrix representation. For diagonally dominant and off-diagonally dominant block operator matrices, we show that the recently introduced quadratic numerical range W2(A) contains the eigenvalues of A and that the approximate point spectrum of A is contained in the closure of W2(A). This provides a new method to enclose the spectrum of unbounded block operator matrices by means of the non-convex set W2(A). Several examples illustrate that this spectral inclusion may be considerably tighter than the one by the usual numerical range or by perturbation theorems, both in the non-self-adjoint case and in the self-adjoint case. Applications to Dirac operators and to two-channel Hamiltonians are given. 相似文献
116.
Berchadsky Y Bernard-Henriet C Finet JP Lauricella R Marque SR Tordo P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(27):7084-7094
Persistent noncyclic phosphoranyl radicals have been prepared and observed by electron paramagnetic resonance (EPR) for the first time. They were obtained by UV-photolysis of a solution containing a bis(trialkylsilyl) peroxide (R = Me, Et) and a tris(trialkylsilyl) phosphite (R = Me, Et, iPr). EPR parameters (a(P) approximately 100 mT) are typical of phosphoranyl radicals exhibiting a trigonal-bipyramidal structure, with the odd electron in an equatorial site. Analysis of the pseudo-first-order decay shows that these phosphoranyl radicals decay by S(H)2 homolytic substitution on the bis(trialkylsilyl) peroxide and by loss of a trialkylsilyloxyl radical (alpha-scission reaction). Both the S(H)2 and alpha-scission reactions depend on the steric bulk of the alkyl groups, that is, the bulkier the alkyl group, the slower the S(H)2 and alpha-scission reactions. 相似文献
117.
This contribution presents an approach based on the material force method which allows to evaluate the fracture sensitivity of rubber material. In order to account for the rate–independent dissipation of filled elastomers subjected to low rates, an endochronic plasticity formulation is introduced. It is shown how configurational forces under consideration of material body forces correspond with the elastic and dissipative energy and how they can be related to energy release rates measured in test configurations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
118.
Stefanie Schnberger Christiane Rotter Konstantin Karaghiosoff 《Heteroatom Chemistry》2014,25(2):95-99
A new rare example of a synthetic route in solution to the hexathiohypodiphosphate anion P2S64− is presented. Starting from P4S3, Li2S, and elemental sulfur in pyridine, this reaction yields yellow block‐shaped crystals of [py2Li]4[P2S6] · 2 py ( 1 ). The molecular structure of this hitherto unknown compound was determined by single crystal X‐ray diffraction and reveals a heteronorbornane skeleton within the Li4P2S6 entity. 相似文献
119.
Makosch M Kartusch C Sá J Duarte RB van Bokhoven JA Kvashnina K Glatzel P Fernandes DL Nachtegaal M Kleymenov E Szlachetko J Neuhold B Hungerbühler K 《Physical chemistry chemical physics : PCCP》2012,14(7):2164-2170
An autoclave reactor was modified to perform simultaneously high energy resolution fluorescence detected X-ray absorption spectroscopy (HERFD XAS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy measurements without altering the reactor design. This operando cell allows one to follow changes in the electronic and geometric structure of the catalyst with HERFD XAS and relate them to the simultaneously detected activity and reaction species with ATR-FTIR formed during the reaction in the liquid phase. The capability of the cell is demonstrated by two studies. The first shows the reduction of Au/CeO(2) precursors in different solvents. The second shows that mainly Au(0) is present in the hydrogenation of nitrobenzene over Au/CeO(2). 相似文献
120.
We derive a new crossing criterion of hazard rates to identify a stochastic order relation between two random variables. We apply this crossing criterion in the context of life tables to derive stochastic ordering results among three families of fractional age assumptions: the family of linear force of mortality functions, the family of quadratic survival functions and the power family. Further, this criterion is used to derive tight bounds for functionals of future lifetimes that exhibit an increasing force of mortality with given one-year survival probabilities. Numerical examples illustrate our findings. 相似文献