全文获取类型
收费全文 | 1210篇 |
免费 | 32篇 |
国内免费 | 9篇 |
专业分类
化学 | 856篇 |
力学 | 10篇 |
数学 | 215篇 |
物理学 | 170篇 |
出版年
2022年 | 13篇 |
2021年 | 12篇 |
2020年 | 18篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 23篇 |
2013年 | 59篇 |
2012年 | 51篇 |
2011年 | 58篇 |
2010年 | 49篇 |
2009年 | 35篇 |
2008年 | 73篇 |
2007年 | 44篇 |
2006年 | 75篇 |
2005年 | 58篇 |
2004年 | 48篇 |
2003年 | 38篇 |
2002年 | 38篇 |
2001年 | 25篇 |
2000年 | 22篇 |
1999年 | 12篇 |
1998年 | 20篇 |
1997年 | 9篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 20篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1987年 | 16篇 |
1985年 | 23篇 |
1984年 | 22篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 14篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1973年 | 11篇 |
1969年 | 9篇 |
1965年 | 8篇 |
排序方式: 共有1251条查询结果,搜索用时 15 毫秒
971.
Lilla Makszin Pter Kustn Balzs Szirmay Csilla Pger Emerencia Mez Krisztina I. Kalcs Vera Pszthy Erzsbet Gyrgyi Ferenc Kilr Andrea Ludny Tams Kszegi 《Electrophoresis》2019,40(3):447-454
Perchloric acid (PCA) precipitation is a well‐known method for the separation of heavily glycosylated proteins and for reducing the masking effect of major serum proteins. The aim of this study is to characterize PCA‐soluble serum proteins in healthy individuals and in patients with systemic inflammatory diseases, such as Crohn's disease and sepsis. A PCA precipitation protocol was prepared and adapted to the analytical methods. After PCA treatment of the serum, the soluble proteins in the supernatant were analyzed by SDS‐PAGE and by microchip gel electrophoresis (MGE). Characteristic changes of the electrophoretic patterns of the PCA‐soluble fractions were observed. Four characteristic bands (at ~11, ~65, ~85, and ~120 kDa) with varying intensity were detected by MGE. The proportion of the ~65, ~85, and ~120 kDa bands were significantly higher in systemic inflammatory conditions than in healthy individuals (p < 0.001), and characteristic patterns were observed in patients with acute inflammation. The marked differences in the acid‐soluble protein patterns, which were observed in patients with ongoing systemic inflammation, might be a good indicator of inflammation. The MGE analysis is a fast screening and quantification method for the detection of characteristic changes among acid‐soluble serum proteins. 相似文献
972.
Beatrice Karg Swantje Mohr Klaus Weisz 《Angewandte Chemie (International ed. in English)》2019,58(32):11068-11071
The oligomer d(GCGTG3TCAG3TG3TG3ACGC) with short complementary flanking sequences at the 5′‐ and 3′‐ends was shown to fold into three different DNA G‐quadruplex species. In contrast, a corresponding oligomer that lacks base complementarity between the two overhang sequences folds into a single parallel G‐quadruplex. The three coexisting quadruplex structures were unambiguously identified and structurally characterized through detailed spectral comparisons with well‐defined G‐quadruplexes formed upon the deliberate incorporation of syn‐favoring 8‐bromoguanosine analogues into specific positions of the G‐core. Two (3+1) hybrid structures coexist with the parallel fold and feature a novel lateral–propeller–propeller loop architecture that has not yet been confirmed experimentally. Both hybrid quadruplexes adopt the same topology and only differ in their pattern of anti→syn transitions and tetrad stackings. 相似文献
973.
Attila Bajtai Gyula Lajk Gbor Nmeti Istvn Szatmri Ferenc Fülp Antal Pter Istvn Ilisz 《Journal of separation science》2019,42(17):2779-2787
New, pharmacologically interesting chiral amino compounds, namely, stereoisomers of α‐hydroxynaphthyl‐ß‐carboline, benz[d]azepine and benz[c]azepine analogs as well as N‐α‐hydroxynaphthylbenzyl‐substituted isoquinolines were enantioseparated by high‐performance liquid chromatographic and subcritical fluid chromatographic methods on polysaccharide‐based chiral stationary phases. Separation of the stereoisomers was optimized in both subcritical fluid chromatography and normal phase liquid chromatographic modes by investigating the effects of the composition of the bulk solvent, temperature, and the structures of the analytes and selectors. Both normal phase liquid chromatography and subcritical fluid chromatography exhibited satisfactory performance, albeit with somewhat different effectiveness in the separation of the stereoisomers studied. The optimized methods offer the possibility to apply preparative‐scale separations thereby enabling further pharmacological investigations of the enantiomers. 相似文献
974.
Generation of 220 mJ nanosecond pulses at a 10 Hz repetition rate with excellent beam quality in a diode-pumped Yb:YAG MOPA system 总被引:1,自引:0,他引:1
Wandt C Klingebiel S Siebold M Major Z Hein J Krausz F Karsch S 《Optics letters》2008,33(10):1111-1113
A novel all-diode-pumped master oscillator power amplifier system based on Yb:YAG crystal rods has been developed. It consists of a Q-switched oscillator delivering 3 mJ, 6.4 ns pulses at a 10 Hz repetition rate and an additional four-pass amplifier, which boosts the output energy to 220 mJ, while a close to TEM(00) beam quality could be observed. Additionally a simulation of the amplification was written that allows for further scaling considerations. 相似文献
975.
Noncompact SO(1,N) sigma-models are studied in terms of their large N expansion in a lattice formulation in dimensions d?2. Explicit results for the spin and current two-point functions as well as for the Binder cumulant are presented to next to leading order on a finite lattice. The dynamically generated gap is negative and serves as a coupling-dependent infrared regulator which vanishes in the limit of infinite lattice size. The cancellation of infrared divergences in invariant correlation functions in this limit is nontrivial and is in d=2 demonstrated by explicit computation for the above quantities. For the Binder cumulant the thermodynamic limit is finite and is given by 2/(N+1) in the order considered. Monte Carlo simulations suggest that the remainder is small or zero. The potential implications for “criticality” and “triviality” of the theories in the SO(1,N) invariant sector are discussed. 相似文献
976.
Ferenc Hegeds Csaba Hs Lszl Kullmann 《International Journal of Heat and Fluid Flow》2010,31(6):1040-1049
The standard approach to analyse the bubble motion is the well known Rayleigh–Plesset equation. When applying the toolbox of nonlinear dynamical systems to this problem several aspects of physical modelling are usually sacrificed. Particularly in vapour bubbles the heat transfer in the liquid domain has a significant effect on the bubble motion; therefore the nonlinear energy equation coupled with the Rayleigh–Plesset equation must be solved. The main aim of this paper is to find an efficient numerical method to transform the energy equation into an ODE system, which, after coupling with the Rayleigh–Plesset equation can be analysed with the help of bifurcation theory. Due to the strong nonlinearity and violent bubble motions the computational effort can be high, thus it is essential to reduce the size of the problem as much as possible. In the first part of the paper finite difference, Galerkin and spectral collocation methods are examined and compared in terms of efficiency. In the second part free and forced oscillations are analysed with an emphasis on the influence of heat transfer. In the case of forced oscillations the unstable branches of the amplification diagrams are also computed. 相似文献
977.
Ariel Michelman-Ribeiro Hacène Boukari Ralph Nossal Ferenc Horkay 《Macromolecular Symposia》2005,227(1):221-230
In this study, we demonstrate how the diffusion of probe particles in aqueous poly(vinyl alcohol) (PVA) solutions and gels is affected by: (i) the presence of cross-links, (ii) the cross-link density, (iii) the polymer concentration. We apply fluorescence correlation spectroscopy (FCS) to measure the diffusion time of a rhodamine-based fluorescent particle (TAMRA) and TAMRA-labeled dextran in PVA solutions and gels prepared at various polymer concentrations (1% to 8.6% w/v) and cross-link densities (1/400 to 1/50 cross-link monomers per PVA monomers). The measurements indicate that the probe particles are slowed down with increasing polymer concentration and with increasing cross-link density. Also, FCS can detect differences in the diffusion times measured in “fresh” and “aged” PVA solutions. We find that FCS provides a quantitative measure of network inhomogeneities. 相似文献
978.
A monitoring system has been developed to characterize the water quality of Lake Balaton. Sediment samples were collected in rivers and harbors around the lake and its catchment area. A modified four-step sequential leaching procedure was applied for determination of the distribution of elements. The fractions were: (1) exchangeable/bound to carbonate; (2) bound to Fe/Mn oxide; (3) bound to organic matter/sulfides; and (4) acid-soluble residue. Samples were taken in three seasons and the average concentration of the elements was calculated. Concentrations of elements were mostly well below the Hungarian standards set for soils and geochemical background values. Most of the elements were found in the acid-soluble residue and bound to organic matter/sulfide fractions, characterizing stable compounds in sediments. There was a difference on the elemental composition of sediments collected at rivers in the catchment area and harbors with relatively small boat traffic. Depending upon the nature of element and local pollution sources the concentration of Pb and Cu ions was found higher in sediments taken at harbors than that of small rivers. Generally, it can be stated that elemental concentration of sediments inside of the lake is smaller than at the catchment area, so the pollution from emission sources has not reached the lake yet. 相似文献
979.
Dietrich Braun Matthias Schacht Hartmut Elssser Ferenc Tüds 《Macromolecular rapid communications》1997,18(4):335-342
The free-radical terpolymerization of maleic anhydride (MSA), isobutyl vinyl ether (VIBE) and anethol (ANE) at 60°C is described. These three monomers do not homopolymerize under the conditions used. Binary copolymers are only obtained from MSA and one of the two investigated donor monomers, whereas the binary copolymerization of VIBE with ANE is not possible. In all terpolymers from these three non-homopolymerizable monomers the MSA content amounts to about 50 mol-%; VIBE is about twice as reactive as ANE. The terpolymerization can formally also be described under the assumption that two binary complexes (MSA/ANE (I) and MSA/VIBE (II)) are copolymerized. For this case the reactivity ratios rI = 0,9 and rII = 1,7 are obtained. 相似文献
980.
Ferenc Jo Jzsef Kovcs Attila Cs. Bnyei gnes Kath 《Angewandte Chemie (International ed. in English)》1998,37(7):969-970
The equilibribrium distribution of water-soluble ruthenium hydrides [HRuCl(tppms)3] and [H2Ru(tppms)4] (tppms = (3-sulfonatophenyl)diphenylphosphane) in the reaction with H2 is governed by the pH value. As a consequence, the selectivity in the hydrogenation of cinnamaldehyde for reaction at C=C or C=O can be completely inverted by changing the pH value (see drawing below). 相似文献