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411.
Chronic Obstructive Pulmonary Diseases (COPDs) constitute a social problem of widespread interest. These diseases increase slowly and constantly. Air pollution and its impact on public health continually repropose certain absolute priorities, such as the pin-pointing of strategies to control the pollution sources, the planning of observational studies and the epidemic control. This work shows that a climate marked by always windy weather and low humidity and with low chemical pollutant concentrations (Pietracupa; Molise, Italy) is connected to smaller prevalence of COPDs in comparison with big cities like Rome. Living in non-polluted areas, the benefits of a healthy climate in terms of an improvement in breathing and bronchial hyperactivity reduction, may only in part be backed up by epidemic evidence; however, they are a solid base on which to build definite research projects which can effectively validate it even from an experimental point of view supported by statistics.  相似文献   
412.
Purpose of this scientific research is the physic and chemical characterization of two historical wax manufactures, made at the end of XIX century by Francesco Bianchi, a papal engraver. The chemical and analytical investigation was necessary to complete and to confirm the restorer's work. The IR Spectroscopy, X-Ray and GC-MS, the best technique to characterise wax, allowed us to obtain the following results. The two manufactures were made with commercial beeswax: in fact, the relative chromatograms showed unchanged peaks about esters of palmitic acid with C24 to C32 alcohol molecules; using standard beeswax we determined the same amount of hydrocarbons present in the wax manufactures. We found several hydrocarbons in these beeswax materials so that it is reasonable to think about successive modifications. ZnO (white zinc), a pigment, was added, probably due to its colour and covering capacity. Sb2S3, Anthimoniun vermilion, a red-orange pigment, was added to these manufactures to give them a soft pink-orange colour. By all used techniques we determined some modifications in the original beeswax; surely they were made to get a more malleable, mouldable, and then more able to be modelled wax.  相似文献   
413.
The many-body perturbation theory is reformulated within the dielectric function method presented in the preceding paper [12]. The self-energy effects are explicitly considered. These corrections turn out to be important and are calculated to the same level of approximation as the corresponding local-field terms. The method is at the moment applicable to π-electron systems within the zero differential overlap approximation. Explicit calculations of the excitation energies for the benzene molecule, using different parametrizations, are presented. Comparison is made with the results obtained in the random phase approximation (RPA ) and other schemes.  相似文献   
414.
We consider a class of second-order uniformly elliptic operators with unbounded coefficients in . Using a Bernstein approach we provide several uniform estimates for the semigroup generated by the realization of the operator in the space of all bounded and continuous or Hölder continuous functions in . As a consequence, we obtain optimal Schauder estimates for the solution to both the elliptic equation (0$">) and the nonhomogeneous Dirichlet Cauchy problem . Then, we prove two different kinds of pointwise estimates of that can be used to prove a Liouville-type theorem. Finally, we provide sharp estimates of the semigroup in weighted -spaces related to the invariant measure associated with the semigroup.

  相似文献   

415.
The first examples of core–shell porous molecular crystals are described. The physical properties of the core–shell crystals, such as surface hydrophobicity, CO2 /CH4 selectivity, are controlled by the chemical composition of the shell. This shows that porous core–shell molecular crystals can exhibit synergistic properties that out‐perform materials built from the individual, constituent molecules.  相似文献   
416.
To reduce the risk of disruption of lifeline systems during the emergency following an earthquake (or any other disaster) preventive interventions on the existing concerned facilities are necessary, but often hindered by the limitation of the available economic resources. In this paper, procedures for the optimal allocation of these resources are presented, with special reference to the case of road networks. It is assumed that the bridges are the only vulnerable elements, and an example of application on a specific network is developed in detail. In the first part of the paper, optimization with respect to several alternative objective functions is dealt with, while in the second part multi-objective optimization is tackled. The results obtained are compared and discussed.Dedicated to Haresh Shah on the occasion of his retirement from Stanford University.  相似文献   
417.
Several unsaturated natural terpenes have been easily converted, in good yields, into the corresponding enantiomerically pure β-azidoselenides by addition of the electrophilic selenium reagent PhSeOTf in the presence of sodium azide. These reactions are stereospecific anti additions, which occur with a Markovnikov orientation. Examples of the synthetic importance of these β-azidoselenides are also reported.  相似文献   
418.
Ultraviolet-visible spectra of flower extracts of the Hibiscus rosa-sinensys L. var. regius maximus species have been measured between 240.02 and 747.97 nm at pH values ranging from 1.1 to 13.0. Deconvolution of these spectra using the Parallel Factor Analysis (PARAFAC) model permitted the study of anthocyanin systems without isolation and purification of the individual species. Seven species were identified: flavilium cation, carbinol, quinoidal base, and E and Z-chacone and their ionized forms. The concentration changes of flavilium cation, quinoidal basen, and E and Z ionized chalcones were determined as function of pH at the different wavelengths. The flavilium cation, quinoidal base, and ionized E-clacone are involved in tho stage kinetic processes, a fast one followed by a slower one. Ionized Z-chalcone obeys a simple first-order processes. The spectral profiles recovered by PARAFAC model are in excellent agreement with bands of experimental spectra reported in the literature for the individual species measured at specific pH values. These results complement those obtained using chemical and simple mathematical techniques and demonstrate how chemometric methods can resolve problems for complex systems.  相似文献   
419.
The molecular structure and ring distortions of nitrobenzene have been determined by gas-phase electron diffraction and ab initio molecular orbital (MO) calculations as well as from the structures of six derivatives studied by X-ray crystallography. The experimental value of the ring angle at the ipso position is = 123.4 ± 0.3° in the free molecule; this is about 1.5° less than the hitherto reported values. Regression analysis of the ring angles in the six derivatives studied by X-ray crystallography yields = 122.7(1)° for nitrobenzene in a crystalline environment. The small difference in the two values of a is interpreted as an effect of intermolecular interactions in the crystal. The value produced by the MO calculations, = 122.3° at the 6–31G* (5D) level, is smaller than either of the experimental results. As regards the ring angles at the meta and para positions, the three techniques of structure determination consistently indicate that these are larger than 120° by a few tenths of a degree. Other important geometrical parameters from the electron diffraction study are r g (C-C) = 1.399 ± 0.003 Å,r g (C-N) = 1.486 ± 0.004 Å,r g (N-O) = 1.223 ± 0.003 Å, and A sO-N-O = 125.3 ± 0.2°. X-ray diffraction experiments on 3,5-dimethyl-4-nitrobenzoic acid and 3,5-dimethylbenzoic acid and ab initio MO calculations provide solid evidence that the geometry of nitrobenzene is little affected when the nitrogroup is twisted by 90° out of the planar equilibrium conformation. This indicates that the extent of -electron transfer from the benzene ring to the nitro group is small. The barrier to rotation is estimated to be 17 ± 4 kJ mol–1 from the electron diffraction data.  相似文献   
420.
The Earth is an open thermodynamic system, that remains in a steady state far from the equilibrium, through energy and matter exchanges with the surrounding environment. These natural constraints, which prevent the system from maximizing its entropy, are threatened by human action and our ecosystem needs urgent protection. In this viewpoint the environmental certification was born, according to international standards ISO 14001, ISO 14040, and European Regulation EMAS. These are voluntary adhesions to a program of environmental protection by companies, administrations and organizations which, starting from the respect of the existing environmental laws and regulations, decide to further improve their environmental performance. To obtain and maintain certification of a system is necessary to apply some indicators to evaluate its environmental performance and to demonstrate its progressive improvement. Here we propose to use for this purpose the thermodynamic indicators produced from energy analysis by Odum. The case study is Montalcino city (Italy) and energy indicators are used to evaluate environmental performance of this system where exist different activities, from agricultural productions, to tourism. Results show that energy analysis could become a valid standard monitoring method for environmental certification, especially in consideration of its wide application field.  相似文献   
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