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991.
Two electrothermal atomic absorption techniques which provide linear working functions over wide concentration ranges, and are suitable for the determination of zinc and copper in aqueous and 10-fold diluted blood serum matrices are evaluated. The first technique is based on modification of the furnace tube to provide a significant decrease of the atomic absorption signal when microliter and larger volumes of sample are injected. The second technique involves a delivery system capable of dispensing micro- and submicroliter sample volumes to the furnace tube. The precision of the two techniques is about 98%. 相似文献
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996.
Activated aryl aroylcyclopropanes cyclise with Lewis acids under mild conditions to 1-aryltetralones. 相似文献
997.
The identification of a set of mutually exclusive and exhaustive propositions concerning the states of quantum systems is a corner stone of the information-theoretic foundations of quantum statistics; but the set which is conventionally adopted is in fact incomplete, and is customarily deduced from numerous misconceptions of basic quantum mechanical principles. This paper exposes and corrects these common misstatements. It then identifies a new set of quantum state propositions which is truly exhaustive and mutually exclusive, and which is compatible with the foundations of quantum theory.Work supported by a grant from Research Corporation. 相似文献
998.
This paper considers the vibration of a symmetrical system consisting of an infinite fluid loaded plate bearing a finite number of parallel stiffeners. The system is driven at the central stiffener by a travelling wave line force. Formal solutions for the equations of motion are found in terms of cosine transforms. Manipulation of the equations allows the problem to be reduced to the solution of a set of linear algebraic equations in the vibration amplitudes at the stiffeners. The coefficients in these equations depend in a simple way upon the stiffener parameters, and upon particular values of the cosine transform of a function which depends only on the plate and fluid parameters, and the stiffener positions. 相似文献
999.
William F Moss 《Journal of Mathematical Analysis and Applications》1980,78(2):574-587
Exitence of fundamental solutions is established for a class of degenerate or singular, second-order, linear elliptic partial differential equations. This class contains, for example, Tricomi's equation in the upper half-plane which arises in the study of aerodynamics; the equation of Weinstein's generalized axially symmetric potential theory which arises in the study of fluid dynamics and elasticity; and Schrödinger's equation with a singular potential which arises in quantum mechanics. 相似文献
1000.
A smog chamber and modeling study of the gas phase NOx–air photooxidation of toluene and the cresols
Roger Atkinson William P. L. Carter Karen R. Darnall Arthur M. Winer James N. Pitts 《国际化学动力学杂志》1980,12(11):779-836
An experimental and modeling study of irradiated toluene–NOx–air, toluene–benzaldehyde–NOx–air, and cresol–NOx–air mixtures at part-per-million concentrations has been carried out. These mixtures were irradiated at 303 ± 1 K in a 5800-liter Teflon-lined, evacuable environmental chamber, with temperature, humidity, light intensity, spectral distribution, and the concentrations of O3, NO, NO2, toluene, PAN, formaldehyde, benzaldehyde, o-cresol, m-nitrotoluene, and methyl nitrate beingmonitored as a function of time. For the toluene and toluene–benzaldehyde–NOx–air runs a variety of initial reactant concentrations were investigated. Cresol–NOx–air runs were observed to be much less reactive in terms of O3 formation and NO to NO2 conversion rates than toluene–NOx–air runs, with the relative reactivity of the cresol isomers being in the order meta » ortho > para. The addition of benzaldehyde to toluene–NOx–air mixtures decreased the reactivity, in agreement with previous studies. Alternative mechanistic pathways for the NOx photooxidations of aromaticsystems in general are discussed, and the effects of varying these mechanistic alternatives on the model predictions for the toluene and o-cresol–NOx–air systems are examined. Fits of the calculations to most of the experimental concentration–time profiles could be obtained to within the experimental uncertainty for two of the mechanistic options considered. In both cases it is assumed that (1) O2 adds to the OH–toluene adduct ~75% of the time forming, after a further addition of O2, a C7 bicyclic peroxy radical, and (2) this C7 bicyclic peroxy radical reacts with NO ~75% of the time to ultimately form α-dicarbonyls and conjugated γ-dicarbonyls (e.g., methylglyoxal + 2-butene-1,4-dial) and ~25% of the time to form organic nitrates. The major uncertainties in the mechanisms concern (1) the structure of the bicyclicperoxy intermediate, and (2) the γ-dicarbonyl photooxidation mechanism. Good fits to the o-cresol concentration–time profiles in the toluene–NOx runs are obtained if it is assumed that o7-cresol reacts rapidly with NO3 radicals. However, it is observed that the model underpredicts nitrotoluene yields by a factor of ~10, but this is in any case a minor product. It is concluded that further experimental work will be required toadequately validate the assumptions incorporated in the aromatic photooxidation mechanisms presented here. 相似文献