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951.
Although terminal chalcogeno ligands are well known for the group 5 and 6 transition metals, they are highly unusual for the oxophilic group 4 metals and unknown so far for the lanthanides or actinides. Cs3UP2S8, is the first actinide compound containing a terminal M=S group. It was synthesized by reacting uranium metal, Cs2S, S, and P2S5 in a 4:1:8:3 ratio at 700 °C in an eutectic LiCl/CsCl mixture. The crystal structure was determined by single‐crystal X‐ray diffraction techniques. Cs3UP2S8 crystallizes in the rhombohedral space group R$\bar{3}$ [a = 15.5217(8) Å; c = 35.132(2) Å, V = 8305.0(8) Å3, Z = 18]. The crystal structure is based on a tetrahedral network type, wherein the uranium atoms are coordinated by a unusual sulfido moiety and thiophosphate groups in a pseudo‐tetrahedral fashion. The U=S distance of 2.635(3) Å observed in the sulfide moiety is approx. 0.2 Å shorter than the average U–S single bond length, indicating a double‐bond type character. 相似文献
952.
Surface treatment (ST) of carbon fibers (CF) leads to an enhancement in fiber‐matrix adhesion. However, it deteriorates the strength of a fiber which makes its reinforcing action less effective in a composite. These effects in opposite directions control the net strength of a composite, and hence, the treatment has to be judiciously applied, which would enhance the first factor and minimize the second one. Authors have recently reported on four effective techniques (using various doses) such as treatments with nanoparticles of Ytterbium fluoride (YbF3), cold remote nitrogen–oxygen plasma (CRNOP), γ‐ray irradiation and nitric acid oxidation. Amongst these methods, nitric acid oxidation is studied in depth in the literature, and γ‐ray irradiation is sparingly studied. However, nano‐YbF3 and CRNOP were first time reported in the literature by the authors. However, comparative aspects of all these methods were not addressed. In this paper, these aspects in details are discussed to lay down the right criteria for selection of a ST technique of CF to design the desired performance of a composite. The composites with polyetherimide and treated CF (including untreated) were developed and evaluated for various properties including tribological one. Treated CF based composites exhibited excellent mechanical and tribological properties (under harsh operative conditions with wear rates ≈ 1 × 10?15 m3/Nm and μ ≈ 0.09). It was concluded that for strength and tribo‐performance, different treatments and doses are to be employed. Overall nanosized‐YbF3 treatment of CF proved to be the most promising ST method. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
953.
The effects of ethanol on the thickness and ionization of adsorbed polymer layer on pigment were investigated. The results showed that the thickness of adsorbed polymer layer decreased with the increase of the ethanol concentration, and then the pigment particles aggregated when the concentration of ethanol is higher than 40%. The zeta potentials became more negative with the increasing of the ethanol concentration, and then changed reversely when the ethanol concentration was higher than 16%. The thickness and structure of adsorbed polymer layer on the particle determined the stability of pigment dispersion. 相似文献
954.
Based on the theory and application developments of polymer flooding on enhancing oil recovery, an improved mathematical model has been developed to simulate the mechanism of viscous-elastic polymer flooding. IMPES method has been presented to solve the polymer flooding model considering the viscosifying effect of elasticity, the effect of decreasing residual oil and the degradation of polymer molecules. The validation of the model is approved by an experiment. A simulation example was carried out using the developed numerical simulator. The enhanced oil recovery mechanism was discussed for viscous-elastic polymer flooding, and corresponding influencing factors were also studied. 相似文献
955.
A water-soluble derivative of chitosan, carboxymethylchitosan (CMCH), was mixed with alkyltrimethylammoniumbromides (CmTAB) and was studied on the adsorption at air/water interface using equilibrium and dynamic surface tension method. The effects of surfactant and polymer concentrations, surfactant chain length, as well as pH of solution were investigated. Addition of the surfactants remarkably promotes the polymer adsorption. Increasing any one of surfactant concentration, surfactant chain length, and pH will facilitate the adsorption of the mixture whereas little effects of polymer concentration were observed. The results are explained in terms of the interaction between CMCH and CmTAB under different conditions. 相似文献
956.
S. Yasin P. F. Luckham T. Iqbal M. Zafar 《Journal of Dispersion Science and Technology》2013,34(2):268-272
For making stable dispersions of graphitic carbon black (Monarch 700), the effectiveness of three dispersants/polymers (hypermer LP1, hypermer B246, and OLOA 11000) in xylene is investigated. Hypermer LP1 (polyhydroxystearic acid) is a homopolymer and hypermer B246 (PEG 30-dipolyhydroxystearate) is a polyhydroxystearic acid/polyethylene oxide/polyhydroxystearic acid ABA block copolymer, while OLOA 11000 (polyisobutylene succinimide) has a polar head group (polyamine) attached to a hydrocarbon chain (polyisobutylene). Well-dispersed graphitic carbon black dispersions were prepared using dispersants at optimum concentrations. Percolation threshold and rheological threshold were determined by analyzing the variations in electrical conductivity and elastic modulus with concentration of carbon black. Above threshold concentration, scaling law was applied to experimental data of rheology (dynamic measurements) and electrical conductivity measurements to evaluate quality of the system. Effectiveness of polymers was investigated on the basis of value of critical exponent (t and t′, respectively) in scaling power law. Hypermer LP1 was proved to be a poor dispersant for Monarch 700 dispersions while other two polymers were found to be effective stabilizers. 相似文献
957.
Redox-active polyelectrolyte-surfactant complexes (PSC) were prepared via the ionic self-assembly of sodium polyacrylate (PAAS) and ferrocenyl surfactant, n-alkyl (ferrocenylmethyl)ammonium bromide (Fcn, n = 8, 12, 16, where n is the carbon number of the alkyl chain), in solution. The obtained PAAS-Fcn complex exhibited crystalline and lamellar mesomorphous structure. Moreover, the ferrocenyl moieties formed H-aggregation in the solid complex as known from the blue shift in the ultraviolet-visible spectrum. Cyclic voltammogram (CV) measurements indicated that the reversibility of the electrode process became worse when the surfactant tail length increases because of the more ordered packing in the complex film formed by longer surfactant tails. The present results demonstrate that the electrochemical activity of the redox-active polyacrylate-ferrocenyl surfactant complex can be easily tuned by changing the surfactant tail length. Our work provides a simple and facile approach to the preparation of redox-active polymers with ordered mesomorphous structure by the ionic self-assembly. 相似文献
958.
Mohamed Nedjhioui Jean Paul Canselier Aicha Bensmaili 《Journal of Dispersion Science and Technology》2013,34(9):1333-1341
Aqueous solutions containing sodium dodecyl sulphate, xanthan gum, and salt were characterized by ionic conductivity, viscosity, and surface tension methods. A preliminary experimental study was performed to evaluate the effect of the mixture compositions on the surface behavior of the mixed polymer/surfactant systems under different solution conditions. An experimental design using response surface method (RSM) was then applied to assess factors interactions and empirical models regarding the physicochemical responses variables (i.e., conductivity, surface tension and viscosity). The main effects of the three independent factors: SDS concentration (x1), NaCl concentration (x2) and xanthan concentration (x3) were determined using in particular a D-optimal design. The results show an important effect of the factors on responses; they also indicate that the synergetic action of surfactant, electrolyte and biopolymer greatly influences these properties. Analysis of variance (ANOVA) showed high variance coefficient (R 2 ) values, thus, ensuring a satisfactory adjustment of the second-order regression model with the experimental data. 相似文献
959.
Naveen Kumar 《Journal of Dispersion Science and Technology》2013,34(11):1601-1606
Classical physical method has been applied in the present study of interaction between water soluble polymer with anionic dimeric and conventional anionic surfactants. Micellization activity of carboxylate-based anionic dimeric (CAD) as well as sodium dodecyl sulfate (SDS) surfactants in the presence of nonionic polymer, that is, polyvinylpyrrolidone (PVP), has been studied through conductometric and surface tensiometric measurements. From these methods the critical aggregation concentrations (CACs), critical micelle concentrations (CMCs), and the effective degree of counterion binding (β) were determined. For the evaluation of behavior of CAD toward the PVP various thermodynamic properties viz. standard Gibbs energy of micellization, standard enthalpy, and entropy of micellization of CAD/PVP mixed system have also been estimated and discussed. The results exhibit that anionic dimeric surfactant interacts strongly with PVP as compared to conventional surfactant. 相似文献
960.
Minghuan Shen Xiaohui Xu Yilin Wang Yajun Guo Minghong Fan Guorong Tan 《Journal of Dispersion Science and Technology》2013,34(8):1178-1182
The viscous properties, scanning electronic microscopy (SEM), and water/oil interfacial tension (IFT) of partially hydrolyzed polyacryamide (HPAM) and hydrophobically associating hydrolyzed polyacryamides modified with N‐dodecylacrylamide were studied with the objective of investigating the influence on destabilization of emulsions. As expected, the copolymers exhibit significant viscosity enhancing capacity and three‐dimensional network structures due to intermolecular hydrophobic associations, and also present high interfacial activities as the IFT decrease with increasing polymer concentration. As a result, the existences of copolymers increased both the viscosity of emulsions and the intensity of interfacial film, in which case slow down the diffusion of demulsifier molecules and enhance the stability of emulsions, finally, the separation of water from oil becomes more difficult. 相似文献