全文获取类型
收费全文 | 323篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 247篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 50篇 |
物理学 | 40篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 15篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 1篇 |
2016年 | 18篇 |
2015年 | 15篇 |
2014年 | 12篇 |
2013年 | 24篇 |
2012年 | 35篇 |
2011年 | 31篇 |
2010年 | 14篇 |
2009年 | 10篇 |
2008年 | 16篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 14篇 |
2004年 | 18篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有342条查询结果,搜索用时 15 毫秒
61.
62.
Bianca Satco 《Nonlinear Analysis: Theory, Methods & Applications》2012,75(1):260-269
The aim of this paper is to obtain an existence result for impulsive differential inclusions of first order with boundary conditions in Hilbert spaces under a hypothesis of integrability in the Henstock-Lebesgue sense for the multifunction on the right-hand side. The proof is based on the assumption that there exists a solution tube for the inclusion taken under consideration (this novel concept which generalizes the extensively used notions of upper and lower solution was adapted to the present setting). Finally, a compactness property is proved. 相似文献
63.
Dr. Kathrin Junge Konstanze Möller Bianca Wendt Shoubhik Das Dr. Dirk Gördes Prof. Dr. Kerstin Thurow Prof. Dr. Matthias Beller 《化学:亚洲杂志》2012,7(2):314-320
The combination of ZnEt2 and chiral pyridinebisoxazoline (pybox) or pyridinebisimidazoline (pybim) ligands catalyzed the asymmetric hydrosilylation of aryl, alkyl, cyclic, heterocyclic, and aliphatic ketones. Under mild conditions, high yields and good enantioselectivities were achieved. ESI measurements allowed for the characterization of the active catalyst. 相似文献
64.
Dr. Andre Sutrisno Dr. Victor V. Terskikh Qi Shi Zhengwei Song Prof. Jinxiang Dong San Yuan Ding Prof. Wei Wang Bianca R. Provost Dr. Thomas D. Daff Prof. Tom K. Woo Prof. Yining Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(39):12251-12259
Metal–organic frameworks (MOFs) are an extremely important class of porous materials with many applications. The metal centers in many important MOFs are zinc cations. However, their Zn environments have not been characterized directly by 67Zn solid‐state NMR (SSNMR) spectroscopy. This is because 67Zn (I=5/2) is unreceptive with many unfavorable NMR characteristics, leading to very low sensitivity. In this work, we report, for the first time, a 67Zn natural abundance SSNMR spectroscopic study of several representative zeolitic imidazolate frameworks (ZIFs) and MOFs at an ultrahigh magnetic field of 21.1 T. Our work demonstrates that 67Zn magic‐angle spinning (MAS) NMR spectra are highly sensitive to the local Zn environment and can differentiate non‐equivalent Zn sites. The 67Zn NMR parameters can be predicted by theoretical calculations. Through the study of MOF‐5 desolvation, we show that with the aid of computational modeling, 67Zn NMR spectroscopy can provide valuable structural information on the MOF systems with structures that are not well described. Using ZIF‐8 as an example, we further demonstrate that 67Zn NMR spectroscopy is highly sensitive to the guest molecules present inside the cavities. Our work also shows that a combination of 67Zn NMR data and molecular dynamics simulation can reveal detailed information on the distribution and the dynamics of the guest species. The present work establishes 67Zn SSNMR spectroscopy as a new tool complementary to X‐ray diffraction for solving outstanding structural problems and for determining the structures of many new MOFs yet to come. 相似文献
65.
The synthesis of a novel series of N-based heterocyclic salts using a simple and efficient N-alkylation of 1,2-bis(4-pyridyl)ethane with reactive halides is reported. These compounds can be transformed into the corresponding pyridinium methylides by addition of a base. The former exhibit an unstable absorption bands at 395–410 nm. The structures of the salts were fully characterized by UV–vis, IR, NMR and MS spectroscopy and elemental analysis. The pK values of selected compounds were also determined and the acid–basic equilibrium was investigated by UV–vis spectrophotometry. The thermal stability of all species was determined by thermogravimetric analysis. 相似文献
66.
Brauch S Henze M Osswald B Naumann K Wessjohann LA van Berkel SS Westermann B 《Organic & biomolecular chemistry》2012,10(5):958-965
Protein profiling probes are important tools for studying the composition of the proteome and as such have contributed greatly to the understanding of various complex biological processes in higher organisms. For this purpose the application of fluorescently labeled activity or affinity probes is highly desirable. Especially for in vivo detection of low abundant target proteins, otherwise difficult to analyse by standard blotting techniques, fluorescently labeled profiling probes are of high value. Here, a one-pot protocol for the synthesis of activated fluorescent labels (i.e. azide, alkynyl or NHS), based on the Ugi-4-component reaction (Ugi-4CR), is presented. As a result of the peptoidic structure formed, the fluorescent properties of the products are pH insensitive. Moreover, the applicability of these probes, as exemplified by the labeling of model protein BSA, will be discussed. 相似文献
67.
de Souza TP Chaimovich H Fahr A Schweitzer B Agostinho Neto A Cuccovia IM 《Journal of colloid and interface science》2012,371(1):62-72
Interfacial concentrations of chloride and bromide ions, with Li(+), Na(+), K(+), Rb(+), Cs(+), trimethylammonium (TMA(+)), Ca(2+), and Mg(2+) as counterions, were determined by chemical trapping in micelles formed by two zwitterionic surfactants, namely N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and hexadecylphosphorylcholine (HDPC) micelles. Appropriate standard curves for the chemical trapping method were obtained by measuring the product yields of chloride and bromide salts with 2,4,6-trimethyl-benzenediazonium (BF(4)) in the presence of low molecular analogs (N,N,N-trimethyl-propane sulfonate and methyl-phosphorylcholine) of the employed surfactants. The experimentally determined values for the local Br(-) (Cl(-)) concentrations were modeled by fully integrated non-linear Poisson Boltzmann equations. The best fits to all experimental data were obtained by considering that ions at the interface are not fixed at an adsorption site but are free to move in the interfacial plane. In addition, the calculation of ion distribution allowed the estimation of the degree of ion coverage by using standard chemical potential differences accounting for ion specificity. 相似文献
68.
Carlo Bianca 《Nonlinear Analysis: Real World Applications》2012,13(6):2593-2608
This paper is concerned with the derivation of a new discrete general framework of the kinetic theory, suitable for the modeling of complex systems under the action of an external force field and constrained to kept constant the mass or density, and the kinetic or activation energy. The resulting model relies on the interactions of single individuals within the population and is expressed by means of nonlinear ordinary or partial integro-differential equations. The global in time existence and uniqueness of the solution to the relative Cauchy problem are proved for which the density and the energy of the solution are preserved. A critical analysis, proposed in the last part of the paper, outlines suitable applications and research perspectives. 相似文献
69.
M. Gaydon M. Raffel C. Willert M. Rosengarten J. Kompenhans 《Experiments in fluids》1997,23(4):331-334
The technical aspects of a photographic stereo camera for three-dimensional particle image velocimetry are described herein.
The hybrid concept of the camera combines advantages of the angular displacement and the translation method. The camera uses
two CCD sensors in order to adjust the lens distances and angles to meet the Scheimpflug criterion and two coupled rotating
mirrors for image shifting. An application to a jet flow with an exit velocity of 33 m/s demonstrates the succesfull optimization
of the recording process.
Received: 27 September 1996/Accepted: 6 March 1997 相似文献
70.
Alessandro D’Aprano Bianca Sesta Noemi Proietti Vincenzo Mauro 《Journal of solution chemistry》1997,26(6):649-662
Conductivity measurements, focused on the counterion binding of lithium perfluorononanoate (LiPFN) micelles in pure water
and in the presence of poly(vinyl pyrrolidone) (PVP), have been carried out. An abrupt decrease of the conductance of the
LiPFN in pure water, due to the self aggregation of anions and to dynamic linkage of cations on the micellar surface, has
been found. Analysis of the conductometric data indicates that about 50% of the stoichiometric concentration of Li+ interacts with the head groups of the perfluorinated anions involved in micellar assembly. Conductometric data of LiPFN-water-PVP
systems reveals a favorable influence of the PVP on the micellization process modulated by the concentration and by the molecular
weight of the polymer. Analysis of these data shows that in presence of PVP the degree of binding of lithium ion to the micellar
assemblies linked to the polymer is smaller than in pure water. By increasing the amount of surfactant in solution up to the
concentration where the polymer becomes saturated by LiPFN micelles, the binding of lithium ion in the system becomes slightly
greater than that observed in LiPFN-water system. This finding can be interpreted in terms of additional binding of lithium
ion to the polymer chains. Conductivity measurements carried out on LiClO4 and KClO4 in water + PVP support this interpretation. 相似文献