全文获取类型
收费全文 | 995篇 |
免费 | 3篇 |
专业分类
化学 | 723篇 |
晶体学 | 1篇 |
力学 | 39篇 |
数学 | 154篇 |
物理学 | 81篇 |
出版年
2023年 | 9篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 29篇 |
2019年 | 18篇 |
2018年 | 15篇 |
2017年 | 12篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 45篇 |
2012年 | 89篇 |
2011年 | 87篇 |
2010年 | 35篇 |
2009年 | 15篇 |
2008年 | 66篇 |
2007年 | 87篇 |
2006年 | 84篇 |
2005年 | 77篇 |
2004年 | 65篇 |
2003年 | 53篇 |
2002年 | 37篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有998条查询结果,搜索用时 15 毫秒
201.
Burns CA Boily JF Crawford RJ Harding IH 《Journal of colloid and interface science》2004,278(2):291-298
An experimental investigation of Cd(II) sorption onto two Australian coals was carried out in 0.1 M NaNO3 at 298.2 K. The initial concentration of Cd(II) was varied from 0.133 to 2.000 mmol/g in a series of batch adsorption experiments with an initial coal concentration of 3.75 g/L of Loy Yang (brown) or of Collie (sub-bituminous) coals in the p[H+] range 2-8. Adsorption edges were typical of metal ion adsorption onto negatively charged organic substrates, starting at p[H+] approximately 3 and increasing with increasing pH. The largest measured Cd(II) uptake capacities from these experiments were of 1.2 mmol/g for Loy Yang and 0.7 mmol/g for Collie coals. This difference is ascribed to the larger concentrations of carboxyl groups in Loy Yang coal (2.78 mmol/g) compared to Collie coal (1.34 mmol/g). An adsorption isotherm for Loy Yang coal at p[H+] 6 was collected up to a surface loading of 1.7 mmol/g of adsorbed Cd(II). These experiments also revealed a release of about 1.5-1.6 protons per adsorbed Cd(II). Zeta potentials of Loy Yang coal suspensions were not affected by Cd(II) adsorption, suggesting that the coal particles efficiently neutralize the charge of Cd(II). Collie coal, on the other hand, exhibited a zeta potential increase that may indicate a modification of the surface potentials of the coal particles. Cd(II) uptake data obtained from both batch experiments and proton balance data have been combined with p[H+] stat data for the same experimentally covered Cd(II)/coal ratios to model adsorption using the NICA-Donnan model. The modeling results suggest that both coals possess identical affinities and reaction stoichiometries. Loy Yang coal, however, possessed a narrower distribution of affinities. 相似文献
202.
Jean-François Brice Re´mi Leveque Pierre Steinmetz 《Journal of solid state chemistry》1981,38(1):19-25
The doping of CaF2?xHx hydridefluorides by aliovalent ions is studied, the aim being the preparation of materials of improved ionic conductivity. It is shown that doping by monovalent Na+ ions is possible. Three hydrogen-rich phases, formulated NayCa1?y(F2?xHx)1?y/2 have been studied. Their conductivity is mainly ionic, but, compared with the same doping in CaF2, the conductivity enhancement is low. This result is interpreted from energetic and structural considerations. 相似文献
203.
Campidelli S Deschenaux R Eckert JF Guillon D Nierengarten JF 《Chemical communications (Cambridge, England)》2002,(6):656-657
Functionalization of C60-oligophenylenevinylene derivatives with a cyanobiphenyl-terminated dendromesogen leads to new donor-acceptor systems with liquid-crystalline properties. 相似文献
204.
Lincker F Bourgun P Masson P Didier P Guidoni L Bigot JY Nicoud JF Donnio B Guillon D 《Organic letters》2005,7(8):1505-1508
[reaction: see text] The synthesis and photonic and liquid-crystalline properties of a novel oligo biphenylene vinylene (OBV) chromophore with an extended pi-electron system are reported; the compound exhibits high fluorescence, a large two-photon absorption cross-section, and two- and three-dimensional liquid-crystalline mesophases. 相似文献
205.
Marie-Chantal Bach Francois Crasnier Jean-François Labarre Claude Leibovici 《Journal of Molecular Structure》1973,16(1):89-97
The optimized geometries and theoretical data from conformational analysis cf borazane and its perfluoro derivatives are investigated within the framework of the CNDO/2 approximation. The effect that fluorination has on the geometrical and electronic parameters of the investigated series of compounds is pointed out and the authors offer an explanation for the anomalous behaviour of H3N.BF3. Furthermore, it is shown that the assumption of tetragonal hybridization for the N and B atoms of any borazane is incorrect if the F3N molecule is used as the Lewis base. 相似文献
206.
Jean-François Côté Dany Brouillette Jacques E. Desnoyers Jean-François Rouleau Jean-Marie St-Arnaud Gérald Perron 《Journal of solution chemistry》1996,25(12):1163-1173
The dielectric constants of 1,2-dimethoxyethane, acetonitrile, -butyrolactone, and propylene carbonate were determined from capacitance measurements extrapolated to infinite frequency; ln are reported as a function of pressure up to 80 MPa at 15, 25, 35, 45°C and as a function of temperature in the range 10 to 50°C at 0.10133 MPa. The variation of ln with temperature or pressure can be expressed by a second order polynomial expression. The isothermal compressibilities of the solvents were determined at 25°C from sound velocities, densities, and heat capacities. A simple correlation can be established between ln /P and for most aprotic solvent. 相似文献
207.
Alain Klaebe Antonio Carrelhas Jean-François Brazier Douraid Houalla Robert Wolf 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):61-76
Abstract The purpose of this paper is to show that optical rotation is a convenient method for studying the intramolecular stereolability in pentacoordinated species, particularly phosphorus derivatives. In chemistry, it is difficult to present a completely new idea and we will deal with this topic under several headings. 相似文献
208.
Dr. Yuriy Sakhno Alice Battistella Dr. Alberto Mezzetti Prof. Maguy Jaber Dr. Thomas Georgelin Prof. Laurent Michot Prof. Jean-François Lambert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(5):1275-1285
Evidence for the formation of linear oligopeptides with nonrandom sequences from mixtures of amino acids coadsorbed on silica and submitted to a simple thermal activation is presented. The amino acid couples (glutamic acid+leucine) and (aspartic acid+valine) were deposited on a fumed silica and submitted to a single heating step at moderate temperature. The evolution of the systems was characterized by X-ray diffraction, infrared spectroscopy, thermosgravimetric analysis, HPLC, and electrospray ionization mass spectrometry (ESI-MS). Evidence for the formation of amide bonds was found in all systems studied. While the products of single amino acids activation on silica could be considered as evolutionary dead ends, (glutamic acid+leucine) and, at to some extent, (aspartic acid+valine) gave rise to the high yield formation of linear peptides up to the hexamers. Oligopeptides of such length have not been observed before in surface polymerization scenarios (unless the amino acids had been deposited by chemical vapor deposition, which is not realistic in a prebiotic environment). Furthermore, not all possible amino acid sequences were present in the activation products, which is indicative of polymerization selectivity. These results are promising for origins of life studies because they suggest the emergence of nonrandom biopolymers in a simple prebiotic scenario. 相似文献
209.
Jean-François Bertazzon 《Comptes Rendus Mathematique》2012,350(13-14):699-702
B. Host and B. Kra (2005) [5] have introduced the characteristic factors for studying “cubic ergodic means”. These factors allow one to resolve, in particular, multiple recurrence problems introduced by H. Furstenberg (1977) [4]. We show here that the continuity of the projection of the system in its characteristic factors characterises cubic means. 相似文献
210.
Aurélie Jolivet Ronan Fablet Jean-François Bardeau Hélène de Pontual 《Analytical and bioanalytical chemistry》2013,405(14):4787-4798
The high spatial resolution analysis of the mineral and organic composition of otoliths using Raman micro-spectrometry involves rigorous protocols for sample preparation previously established for microchemistry and trace elements analyses. These protocols often include otolith embedding in chemically neutral resin (i.e., resins which do not contain, in detectable concentration, elements usually sought in the otoliths). Such embedding may however induce organic contamination. In this paper, Raman micro-spectrometry reveals the presence of organic contamination onto the surface obtained from the use of epoxy resin, specifically Araldite. This contamination level varies depending on otolith structures. Core and checks, known as structural discontinuities, exhibit the most important level of contaminations. Our results suggest that otolith embedding with resin affects the organic matrix of the otolith, probably through an infiltration of the resin in the crystalline structure. The interpretation of chemical otolith signatures, especially Raman otolith signatures, and stable isotope analyses should then be revised in light of these results. In this respect, we propose a method for the correction of Raman otolith signatures for contamination effects. 相似文献