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51.
The three-component ionic microemulsion system consisting of AOT/water/decane shows an unusual phase behavior in the vicinity
of room temperature. The phase diagram in the temperature-volume fraction (of the dispersed phase) plane exhibits a lower
consolute critical point at about 40 degrees centigrades and 10% volume fraction. A percolation line, starting from the vicinity
of the critical point, cuts across the plane, extending to high volume fraction side at progressively lower temperatures.
In this paper we review the evidence that allows to interpret the phase behavior of our system in terms of interacting spherical
droplets. We also investigate the dynamics of droplets, below and approaching the critical point by dynamic light scattering.
The first cumulant and time evolution of the droplet density correlation function can be quantitatively calculated by assuming
the existence of polydispersed fractal clusters formed by the microemulsion droplets due to attraction. The relaxation phenomena
observed in an extensive set of measurements of electrical conductivity and permittivity close to percolation is also reviewed
and interpreted through the same cluster-forming mechanism, which reproduces the most relevant features of the frequency-dependent
complex dielectric constant of this system.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
52.
Uyguner CS Hellriegel C Otto W Larive CK 《Analytical and bioanalytical chemistry》2004,378(6):1579-1586
Humic substances are precursors of carcinogenic trihalomethanes (THMs) formed during disinfection by chlorination in water treatment processes. In an effort to understand the relationship between trihalomethane formation potential (THMFP) and physicochemical properties of humic substances, UV-visible absorbance, fluorescence in emission and synchronous scan modes, and NMR spectra were measured for several aquatic fulvic and humic acids. For comparison, a soil fulvic acid was also examined using these methods. The feasibility of the gradient modified spin-echo (GOSE) NMR experiment to selectively measure singlet resonances arising from isolated protons was examined. In addition, diffusion coefficients were measured for DMSO solutions of the fulvic acids using BPPLED and GOSE-edited pulse sequences. Although none of the methods tested produced results that correlated with THMFP, the GOSE intensities determined for different regions of the NMR spectra did reflect the relative abundance of different types of functional groups produced by lignin oxidation. In addition, the GOSE-edited diffusion results suggest that the isolated protons, those most reactive to chlorination, are more likely contained in the larger molecular weight fractions of fulvic acids. 相似文献
53.
采用循环伏安法,稳态法,计时电位法等研究了SO2在聚钴卟啉膜电极上的电化学氧化过程,并和SO2在贵金属电极上的行为进行了比较。 相似文献
54.
55.
Desulfurization of flue gas: SO(2) absorption by an ionic liquid 总被引:7,自引:0,他引:7
56.
The first investigation on catalytic asymmetric [2, 3]-sigmatrop-ic rearrangement of sulfur ylides generated from carbenoids andallenic phenyl sulfide was carried out. Up to 55% ee value wasobtained. 相似文献
57.
Danielle Giron S. Monnier M. Mutz P. Piechon T. Buser F. Stowasser K. Schulze M. Bellus 《Journal of Thermal Analysis and Calorimetry》2007,89(3):729-743
Adequate very sensitive quantification methods are needed for the development and are also now required for the monitoring
of undesirable solid form(s) as routine tests. The pre-requisite for quantitation are selectivity, sensitivity and most important
the purity of standards and their proper storage, what is a challenge for metastable forms.
Several analytical techniques are available such as X-ray diffraction, spectroscopy, thermal analysis and microcalorimetry.
The different steps of the validation of the analytical methods and problems to be solved are discussed. Examples illustrate
the different techniques and compare their possible advantages and limits. The relative standard deviation of measurements
should allow for checking the homogenization procedure of mixtures for calibration. The validation should be carried out following
ICH guidelines for validation of analytical methods. Comparison of different techniques in adequate concentration range add
confidence in the analytical results. 相似文献
58.
The sintering and the structure of clinkers, modified by the introduction of different ionic forms of sulfur and phosphorus
into the raw mix, were examined. One reference synthetic mixture and 25 modified mixtures were prepared by mixing the reference
sample with 0.5, 1.0, 1.5, 2.0 and 2.5%w/w of chemical grade CaSO4, CaS, Ca3(PO4)2, CaHPO4 and Ca(H2PO4)2. Free lime content in all samples was measured. The sintering reactions in samples were recorded by means of differential
thermal analysis. The texture of the clinkers was examined using a scanning electron microscope and EDX. It is concluded that,
despite of their relatively low doping concentration in the raw mix, P and S affect considerably its reactivity and the texture
of the clinker. The various ionic forms of the same element (SO4
2-, S2- for S, PO4
3-, HPO4
2- and H2PO4
- for P) exhibit a different and unequivocal effect on the reactivity of the synthetic raw mix and on the texture of the corresponding
clinkers. S (in both forms) and P (added as HPO4
2-) are mainly dissolved in the melt and they have a positive effect on the burnability of the raw mix. P (added as PO4
3- or H2PO4-) is preferentially accumulated in belite. In this case further stabilization of β-C2S occurs and the binding of the free lime is hindered.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
59.
Bradley D. Fahlman Andrew D. Daniels Gustavo E. Scuseria Andrew R. Barron 《Journal of Cluster Science》2002,13(4):587-599
Thermodynamic and mechanistic features of the chalcogen exchange reaction between [RGa(
3-Te)]4 and elemental sulfur or selenium have been studied employing density functional theory (DFT) calculations using the BL3YP basis set and Stuttgart pseudopotentials. For [MeGa(
3-E)]4 (E=S, Se, Te) the correlation between the calculated parameters and diffraction data for their isolable analogs is greater than 98%. Each step of the conversion of [MeGa(
3-Te)]4 to [MeGa(
3-E)]4 via [Me4Ga4(
3-Te)4–x
(
3-E)
x
] (E=S, Se) is predicted to occur as a series of isolated reactions. The entropy change for each chalcogen exchange is small in magnitude and corresponds to the degree of cage distortion within the cubane molecules. Calculations performed on [MeGa(
3-Te)]4...S8 and [MeGa(
3-Te)]4-S suggest that an increase in electrophilicity of the gallium next to a surface bound tellurium may result in nucleophilic cage opening for which intermediate structures are calculated. 相似文献
60.
A novel DBU-assisted carbonylation of amines with carbon monoxide and sulfur has been developed for the synthesis of S-alkyl thiocarbamates. In the presence of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), S-alkyl thiocarbamates are synthesized in excellent yields from amines, carbon monoxide, sulfur, and alkyl halides under mild conditions (1 atm, 20°C). In the absence of DBU, however, no formation of S-alkyl thiocarbamate is observed. The present DBU-assisted carbonylation can also be applied to new synthetic methods for benthiocarb and orthobencarb (herbicides) and carbamoyl chlorides. 相似文献