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101.
S Rajasekar 《Pramana》1992,39(5):509-520
The influence of time-dependent periodic optical drive in the Fabry-Perot interferometer system has been investigated using
a theoretical model equation. A variety of features such as different routes to chaos, multiperiodic oscillations, coexistence
of multiple attractors and mode-locking with devil’s staircase are found to occur for a certain range of parametric values. 相似文献
102.
The research was conducted to know the effect of amikacin administrations to the concentration of drug in reptile. The 16 sanca batik snakes (Broghammerus reticulatus) were adapted then divided into four groups of which each was administered5 mg · kg–1 body weight of amikacin by posterior and anterior intravenous and intramuscular injection, respectively. The blood collection was done by cardio-puncture to each group at minute 1, 60 and 24, 48 h after drug injection and the drug concentration was analysed by High Performance Liquid Chromatography. The result showed that the drug by i.v. or i.m. administration routes (t1,t48) from posterior region had higher concentrations (81.90 ± 23.1) mg · mL–1, (17.23 ± 5.29) mg · mL–1) compared to the anterior injection (P < 0.01). The other concentration comparisons between regions resulted in no significant difference. 相似文献
103.
104.
The purpose of this review is to showcase the present capabilities of ambient sampling and ionisation technologies for the analysis of polymers and polymer additives by mass spectrometry (MS) while simultaneously highlighting their advantages and limitations in a critical fashion. To qualify as an ambient ionisation technique, the method must be able to probe the surface of solid or liquid samples while operating in an open environment, allowing a variety of sample sizes, shapes, and substrate materials to be analysed. The main sections of this review will be guided by the underlying principle governing the desorption/extraction step of the analysis; liquid extraction, laser ablation, or thermal desorption, and the major component investigated, either the polymer itself or exogenous compounds (additives and contaminants) present within or on the polymer substrate. The review will conclude by summarising some of the challenges these technologies still face and possible directions that would further enhance the utility of ambient ionisation mass spectrometry as a tool for polymer analysis. 相似文献
105.
Mario Llano-RestrepoAuthor Vitae Y. Mauricio Muñoz-MuñozAuthor Vitae 《Fluid Phase Equilibria》2011,307(1):45-57
Due to the economics of the ethylene market and the subsidized production of fermentation-based ethanol in some countries, use of the ethylene hydration process to make ethanol has been steadily declining. The economics of this process might improve by combining the reaction and separation in a reactive distillation column, whose conceptual design requires a study of the combined chemical and phase equilibrium (CPE) of the reacting system. In this work, the Peng-Robinson-Stryjek-Vera equation of state was combined with the UNIQUAC activity coefficient model through the Wong-Sandler (WS) mixing rules in order to correlate the available experimental data for the vapor-liquid equilibria (VLE) of the ethylene-water, ethylene-ethanol, and ethanol-water binary systems at 200 °C. The interaction energies of the UNIQUAC model and the binary interaction coefficient of the WS mixing rules were used as the fitting parameters. From the optimum values of these parameters, both the VLE and the combined CPE of the ethylene-water-ethanol ternary system were predicted at 200 °C and various pressures. At this temperature, the catalytic activity of a H-pentasil zeolite has already been reported to exhibit a maximum for ethylene hydration, and also the experimentally measured two-phase region of the ternary system is sufficiently wide. By means of the reactive flash method, the chemical equilibrium compositions of the liquid and vapor phases were determined for several pressures, and the equilibrium conversion and the vapor fraction were calculated as functions of the ethylene to water feed mole ratio. It turns out that the vapor-liquid mixed-phase hydration of ethylene achieves equilibrium conversions much higher than those computed for a vapor-phase reaction that would hypothetically occur at the same conditions of pressure and feed mole ratio. It was found that the reactive phase diagram of the ternary system exhibits a critical point at 200 °C and 155 atm. 相似文献
106.
Yi-Qiang Tang 《Journal of organometallic chemistry》2011,696(13):2576-9483
Palladium(II)-N-heterocyclic carbene complex 1 derived from proline has been proved to be a highly effective catalyst in the Suzuki-Miyaura coupling reaction of aryl iodides and bromides with arylboronic acids in water at room temperature. The reactions are tolerant towards various functional groups in the substrates. Moreover, the complex 1-catalyzed medium-scale (10.0 mmol) Suzuki-Miyaura reactions were also carried out and it was found that the complex was also effective enough in these cases. 相似文献
107.
108.
Synthetic hydrogels can be used as scaffolds that not only favor endothelial cells(ECs) proliferation but also manipulate the behaviors and functions of the ECs.In this review paper,the effect of chemical structure,Young’s modulus (E) and zeta potential(ξ) of synthetic hydrogel scaffolds on static cell behaviors,including cell morphology,proliferation, cytoskeleton structure and focal adhesion,and on dynamic cell behaviors,including migration velocity and morphology oscillation,as well as on EC function such as anti-platelet adhesion,are reported.It was found that negatively charged hydrogels,poly(2-acrylamido-2-methylpropanesulfonic sodium)(PNaAMPS) and poly(sodium p-styrene sulphonate) (PNaSS),can directly promote cell proliferation,with no need of surface modification by any cell-adhesive proteins or peptides at the environment of serum-containing medium.In addition,the Young’s modulus(E) and zeta potential(ξ) of hydrogel scaffolds are quantitatively tuned by copolymer hydrogels,poly(NaAMPS-co-DMAAm) and poly(NaSS-co-DMAAm), in which the two kinds of negatively charged monomers NaAMPS and NaSS are copolymerized with neutral monomer,N,N-dimethylacrylamide(DMAAm).It was found that the critical zeta potential of hydrogels manipulating EC morphology,proliferation,and motility isξcritical= -20.83 mV andξcritical= -14.0 mV for poly(NaAMPS-co-DMAAm) and poly(NaSS-co-DMAAm),respectively.The above mentioned EC behaviors well correlate with the adsorption of fibronectin, a kind of cell-adhesive protein,on the hydrogel surfaces.Furthermore,adhered platelets on the EC monolayers cultured on the hydrogel scaffolds obviously decreases with an increase of the Young’s modulus(E) of the hydrogels,especially when E>60 kPa.Glycocalyx assay and gene expression of ECs demonstrate that the anti-platelet adhesion well correlates with the EC-specific glycocalyx.The above investigation suggests that understanding the relationship between physic-chemical properties of synthetic hydrogels and cell responses is essential to design optimal soft and wet scaffolds for tissue engineering. 相似文献
109.
110.
John M. Brown 《Angewandte Chemie (International ed. in English)》1987,26(3):190-203
Stereochemical control is a major concern in the application of homogeneous catalysis to organic chemistry. In this context, the directed hydrogenation of olefins employing cationic rhodium or iridium catalysts has considerable potential, for very high selectivity can be attained under mild reaction conditions. The only requirement is a polar functional group in proximity to the double-bond which remains bound to the metal during the catalytic cycle and thereby controls the Stereochemical course of hydrogen delivery through the constraints of chelation. The substituent is most frequently a hydroxy group OH but can also be an ester, amide or carbamate group; other groups remain to be scrutinized. In cyclic compounds, directed hydrogenation can lead to face-selectivity, and the polar substituent may be in the β-, γ-, or δ-position to the double-bond. Acyclic stereoselection ensues with β- or γ-substituents in appropriate compounds, and the configuration of reduced product is predictable on the basis of simple rules. The application of optically active rhodium complexes leads to useful kinetic resolution procedures. 相似文献