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191.
Crystals of Co3(AsO4)2 were grown from the melt of a mixture of Co2As2O7 and As2O5. The crystals are isostructural with Mg3(AsO4)2 and are tetragonal with a = 6.858(2), c = 18.872(5) Å, Z = 6, and space group . A total of 1048 independent reflections were measured by diffractometer and used in the full-matrix refinement to a final R value of 0.069. The structure contains two distinct AsO4 groups. Two of the cobalt ions are octahedrally coordinated and a third occupies a site with four short and four long CoO distances. The crystal structure of Co3 (AsO4)2 is not based on the continuous three-dimensional closest packing of oxygen atoms. Nevertheless the number of oxygen atoms per cubic centimeter is 5.4 × 1022, which falls in the range of values for hexagonal and cubic closest packed structures. A better measure of the degree to which closest packing is achieved by a structure is suggested. It is based on an analysis of the polyhedra of oxygen atoms which surround each of the oxygen atoms in a structure and their relation to the polyhedra in ideally closest packed structures. In order to facilitate the analysis, polytopes of 11- and 12-vertex polyhedra were studied. A new decahexahedral 11-vertex polyhedron was found. 相似文献
192.
Some cationic five coordinate complexes of formula [Os(CO)(NO)L2A]PF6 (L = tertiary phosphine, A = an acetylene) have been prepared by reaction of the appropriate acetylene with [Os(CO)(NO)L2(acetone)]PF6; the variable temperature 1H NMR spectra of some of these indicate that the coordinated π-acetylene undergoes fluxional behaviour. 相似文献
193.
A.A. Koridze P.V. Petrovskii S.P. Gubin V.I. Sokolov A.I. Mokhov 《Journal of organometallic chemistry》1977,136(1):65-71
The 13C NMR spectra ofthe series of α,α’ -dideuterated ferrocenylcarbenium ions and their precursors, ferrocenylcarbinols as well as other ferrocene derivatives have been measured. The structures of ferrocenylcarbenium ions is discussed. 相似文献
194.
Zinc ions react with the surfactant ethylhexadecyldimethylammonium bromide (EHDABr) to form a surface active sublate which can be removed from aqueous chloride solutions by ion flotation. A typical ion flotation procedure involves passing air through a 235-ml solution containing 5 ppm Zn2+, 2.0 M HCl, and 2.5 × 10?3M EHDABr at a flow rate of 40 ml/min for 150 min. The procedure is simple and rapid. Cadmium, copper, lead, and nickel ions cause reductions of zinc flotation efficiencies of less than 2.5% under the experimental conditions. 相似文献
195.
De Bin ZHU Da XING Xian LI Lan ZHANG 《中国化学快报》2006,17(4):499-501
Current methods for single nucleotide polymorphism (SNP) analysis are time-consuming and complicated. We aimed at development of one-step real-time fluorescence mutant-allele-specific amplification (MASA) method for rapid SNP analysis. The method is a marriage of two technologies: MASA primers for target DNA and a double-stranded DNA-selective fluorescent dye, SYBR Green I. Genotypes are separated according to the different threshold cycles of the wild-type and mutant primers. K-rar oncogene was used as a target to validate the feasibility of the method. The experimental results showed that the different genotypes can be clearly discriminated by the assay. The real-time fluorescence MASA method will have an enormous potential for fast and reliable SNP analysis due to its simplicity and low cost. 相似文献
196.
A packed-column gas-chromatograph/mass-spectrometer (GC/MS), Hewlett-Packard 5982, was modified to accommodate fused silica capillary columns. The original GC/MS interface and chemical-ionization sample-line in the ion-source were changed to allow the end of a fused silica capillary column to enter the ion-chamber directly. For chemical-ionization operation, the reagent gas was brought into the MS through the direct-insertion probe port. The calibration compound was introduced through the electron-impact sample-inlet, which simplified the operation. The modified system yields higher sensitivity and more efficient separation, as well as simpler operation, without sacrificing any original instrument functions. 相似文献
197.
Molar excess volumes, VE, for pyridine (A) + α-picoline (B), + β-picoline (B) and + γ-picoline (B) and benzene (A) + toluene (B), + o-xylene (B) and + p-xylene (B) and carbon tetrachloride (A) + n-heptane (B) have been measured dilatometrically as a function of temperature and composition and have been utilized to study B—B and B—B—B interactions in the presence of A via the Mayer—McMillan approach. A model has also been presented to account for these B—B and B—B—B interactions. The VE data at 308.15 K have also been analysed in terms of the “graph theoretical” approach which describes the VE data well for all these mixtures at 308.15 K. The “graph theoretical” approach has further been extended to successfully evaluate VE data for a mixture at any temperature, T2, when the VE data at T1 are known. 相似文献
198.
A. A. Pasynskii I. L. Eremenko Yu. V. Rakitin B. Orazsakhatov V. M. Novotortsev O. G. Ellert V. T. Kalinnikov 《Journal of organometallic chemistry》1981,210(3):377-384
Isostructural heterotrinuclear complexes (C5H5CrSCMe3)2S · M(CO)5 (II–IV) were isolated from photochemical reactions between the antiferromagnetic complex (C5H5CrSCMe3)2S (I) (with the Cr---Cr bond 2.689 Å long and with the exchange parameter −2J = 430 cm−1) and metal hexacarbonyls, M(CO)6, where M is Cr, Mo, or W. According to the X-ray structural data on III and IV, complex I plays the role of an unusual antiferromagnetic ligand L bound to M through the sulphide bridge (M–S 2.58(2) Å). Its geometry remains practically unaffected by the complex formation (the Cr---Cr bond length in III and IV is 2.73(1) Å). The exchange parameter, −2J (410, 440 and 440 cm−1 in II to IV, respectively), also shifts only insignificantly from that of I, which probably means that indirect exchange via the sulphide bridge in I is of minor importance compared with the direct Cr---Cr exchange. The Cr---Cr bond length may thus be correlated with the observed overall exchange coupling. 相似文献
199.
The stabilities of the hydrated uranyl phosphates (UO2)3(PO4)2 · 4 H2O, UO2HPO4 · 4 H2O, and UO2(H2PO4) · 3 H2O have been reinvestigated. The compounds identified by thermal analysis have been prepared isothermally and characterized by their strongest X-ray reflections. During dehydration, oxygen was not evolved and the crystalline compounds (UO2)3(PO4)2, (UO2)2P2O7, UO2(PO3)2, and probably (UO2)3P4O)13 were found.
At still higher temperatures, the uranyl phosphates are reduced. The decomposition products lose phosphorus oxide above 1300–1400°C. The present results are summarized in a tentative pseudo-binary phase diagram UOx(x = 3 to 2)—UO2(PO3)2. 相似文献
200.
Twenty-two aromatic amines are determined by the diazotization-coupling spectrophotometric technique, using 8-amino-1-hydroxynaphthalene-3,6-disulphonic acid (H-acid) and N-(1-naphthyl) ethylenediamine (N-na) as coupling agents. The following are determined by both methods: 2-and 4-ethylaniline, 4-aminobenzonitrile, 3- and 4-aminoacetophenone, 4-aminobenzophenone, 4-iodoaniline, 2,5-dichloroaniline, 4-aminohippuric acid, 2-aminobenzyl alcohol, 3-aminobenzamide, sulphathiazole, 2-, 3- and 4-methoxyaniline and 2,4-, 3,4- and 3,5-dimethylaniline. It is possible to determine 2,3- and 2,5-dimethylaniline only by the H-acid method, but 2,6-dimethylaniline cannot be determined by either method. 2-Aminobenzamide can only be determined by the N-na method. In the application of the H-acid method to the methoxyanilines and dimethylanilines, the colour is developed by adding a large excess of sodium bicarbonate and H-acid. In the application of the N-na method to the ethylanilines, methoxyanilines and 2,4-, 3,4- and 3,5-dimethylanilines, the colour is developed by addition of a large excess of N-na reagent and allowing the solution to stand overnight. 相似文献