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21.
Hoong‐Kun Fun Qingli Hao Jiang Wu Xujie Yang Lude Lu Xin Wang Suchada Chantrapromma Ibrahim Abdul Razak Anwar Usman 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):m87-m88
In the structure of the title compound, [CuII(en)2][(EtO)2P(S)S]2 (en is ethylenediamine) or [Cu(C2H8N2)2](C4H10O2PS2)2, the Cu atom lies on a center of inversion and is coordinated in a slightly distorted square coordination geometry by four N atoms from two ethylenediamine molecules. The diethyl dithiophosphate moieties, (EtO)2P(S)S?, act as counter‐anions. 相似文献
22.
Phenols are converted to salicylaldehydes with paraformaldehyde, MgCl2-Et3N in THF, and subsequent treatment with methyl (triphenylphosphoranylidene)acetate gave the corresponding methyl ortho-hydroxycinnamate derivatives. The sequence is conveniently carried out as a one-pot procedure. 相似文献
23.
S. Jovanović B. Smodiš R. Jaćimović P. Vukotić P. Stegnar 《Journal of Radioanalytical and Nuclear Chemistry》1989,135(1):59-65
Neutron-flux behaviour during irradiation should be known when applying the ko-method of neutron activation analysis /NAA/. During two 100-hour operating periods of the TRIGA MARK II reactor, Ljubljana, the flux was measured by means of a197Au/n,/198Au monitor /E=411.8 keV/. Cadmium-covered irradiations were also performed to obtain the epithermal flux and thermal-to-epithermal flux ratio variations. Consistency was found between these results and the reactor operators' logbook record. 相似文献
24.
W. Bocian J. Jaźwiński O. Staszewska J. W. Wiench L. Stefaniak G. A. Webb 《Chemistry of Heterocyclic Compounds》1996,32(11-12):1358-1366
Multinuclear1H,13C,14N,15N, and17O NMR data are presented for some sydnones, isosydnones and isothiosydnones. The type of valence tautomerism shown in (Fig. 1) is not observed for the compounds studied. At high pH compounds2 and12 are found to undergo transformations. The more suitable NMR parameters are reported for establishing the structures of mesoionic compounds containing three heteroatoms in the five-membered conjugated ring. Someab initio GIAO calculations on a model structure of sydnones and related compounds have been performed. 相似文献
25.
F. Pérez-Giménez G. M. Antón-Fos F. J. García-March M. T. Salabert-Salvador R. A. Cercós-del-Pozo J. Jaén-Oltra 《Chromatographia》1995,41(3-4):167-174
Summary The possible relation existing between RF values obtained by thin-layer chromatography for a group of anilines with connectivity indices proposed by Kier and Hall has been studied. Using multivariable regression the corresponding connectivity functions, selected for their respective correlation coefficients, standard deviations, Snedecor's F and Student's t were obtained. Regression analysis of the connectivity functions gives a correct prediction of the experimental elution sequence for this group of substances on silica gel stationary phases and various mobile phases of different polarity. The corresponding random and stability studies of the different prediction models selected were carried out, showing good stability and null randomness in all cases. 相似文献
26.
Juan Primera Anwar Hasmy Thierry Woignier 《Journal of Sol-Gel Science and Technology》2003,26(1-3):671-675
We introduce a new numerical technique for the calculation of the pore size distribution in two-dimensional disordered systems. Our method is based on a triangulation technique which allows a closer measurement of pores surface without any morphological hypothesis.In this work, we focus our calculations in simulated gels. Such materials are modeled in two different conditions: by means of the Diffusion-Limited and Reaction-Limited Cluster-cluster Aggregation algorithms, DLCA and RLCA, respectively. In both situations, when the particles concentration decreases, the average pores size increases. The more compact cluster in RLCA, compared with DLCA, is consistent with the pore size distribution we have calculated. The simulated mean pore size is quantitatively in agreement with experimental data from literature. 相似文献
27.
Hong SB Lee SH Shin CH Woo AJ Alvarez LJ Zicovich-Wilson CM Camblor MA 《Journal of the American Chemical Society》2004,126(42):13742-13751
Here, we report that synthetic gallosilicate molecular sieves with the NAT topology and Si/Ga ratios close to but slightly higher than 1.50 undergo an in situ transformation under their crystallization conditions. The materials have been studied ex situ by using powder X-ray diffraction, elemental and thermal analyses, and multinuclear MAS NMR. The transformation is characterized by a change in the distribution of Si and Ga of the NAT framework, from a quite (but not completely) disordered phase to a very highly (but not completely) ordered one, accompanied by a change from tetragonal to orthorhombic symmetry. During most of the solution-mediated transformation, no noticeable signs of fresh precipitation, phase segregation, or changes in the chemical composition are detected. Intermediate materials show variations in the degree of Si-Ga ordering and orthorhombic distortion and are not physical mixtures of the disordered and ordered phases. Ab initio calculations strongly suggest a preferential siting of Si in the tetrahedral sites involved in a smaller number of 4-rings in the NAT topology (i.e., the low multiplicity site). The cost of violations of Loewenstein's rule has also been calculated. For this topology and chemical composition the preferential siting and Loewenstein's rule drive together the system to the ordered configuration. A Monte Carlo sampling procedure affords a reasonable model for the initial, mainly disordered state, which fits well within the experimental disorder-order series. 相似文献
28.
J. Adam A. Kuklík A. Špalek D. Venos M. Ja. Kuznecova 《Czechoslovak Journal of Physics》1978,28(8):857-864
Gamma-radiation from the reactions of 28 MeV and 26 MeV3He-ions on the209Bi target has been studied by means of Ge(Li) detectors. Individual observed prompt -ray transitions have been assigned to the corresponding reactions. The results of previous studies of the209At nucleus have been verified and completed. Two new levels at energies of 640 keV and 1270·5 keV have been introduced. Additionally, 15 new transitions have been observed which could belong to209At. The209At level structure is discussed in terms of nuclear models. 相似文献
29.
Anwar Usman Chandini R. Nayar P. A. Unnikrishnan P. B. Sreeja M. R. Prathapachandra Kurup Hoong‐Kun Fun 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):o724-o726
The title molecule, C13H13N3O3·H2O, is in the form of a monohydrated zwitterion. The tetrahydropyridinium ring adopts an envelope conformation and is nearly coplanar with the plane of the imidazoline ring. The water solvate molecule plays an important role as a bridge between zwitterions, forming molecular chains running along the c direction, which are interconnected by N—H?O hydrogen bonds into molecular ribbons. The crystal packing is further stabilized by another N—H?O and one O—H?N hydrogen bond, which interconnect the molecular ribbons. 相似文献
30.
A. Jeyabharathi M. N. Ponnuswamy S. Nanjundan Hoong‐Kun Fun Suchada Chantrapromma Anwar Usman Ibrahim Abdul Razak 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(1):o26-o28
Chalcones (α,β‐unsaturated ketones) are effective antitumour agents. It has been proved that having halogen or methoxy groups substituted in various positions of the phenyl ring enhances the activity of chalcones many times. The title compounds, C21H20O5 and C19H15BrO3, respectively, were chosen for crystallographic study in order to determine their structures and conformations. In both compounds, the keto group is in the s‐cis conformation and is almost planar. There are weak intramolecular interactions in both structures. 相似文献