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11.
L.L. Carvalho 《European Polymer Journal》2006,42(10):2589-2595
Samples of a methacrylic side-chain azopolymer were synthesized by a radical copolymerization of methyl-methacrylate with the methacrylic derivative of the commercial dye Disperse Red-13 (DR13). Copolymers with different molecular weight were obtained by varying the reaction time and the concentration of initiator. Samples with molecular weight averages (Mw) from 3 to 8 × 104 g/mol and 1.4-1.7 polydispersity were obtained. The glass transition temperature of the samples increased linearly from the lower to the highest molecular weight. Optical quality cast films were prepared for all samples and photoinduced birefringence was successfully carried out in all samples as well as surface relief gratings could be inscribed in the cast films. 相似文献
12.
A. Abras A. A. G. Campos A. V. de Carvalho L. O. Ladeira 《Applied Physics A: Materials Science & Processing》1986,41(3):185-189
Iron-boride layers on low-carbon steel were produced by thermochemical diffusion process. The surface interaction products: Fe2B, FeB, FeBx (x>1) and a solid solution of iron in boron were identified by surface Mössbauer spectroscopy (CEMS and XMS). Samples of original and boronized steel were subjected to corrosion process by immersion in HCl (0.1 N) solution for 150 h. While the steel sample was strongly corroded, none corrosion product was found on the boronized sample surface. However, significant changes in relative percentages of the various iron boride phases were detected. Also, samples of original and boronized steel were subjected to oxidation process by heat-treatment in air at 300°C for 8 h and 500°C for 4 h. At 300°C, while bulk Fe3O4 and -Fe2O3 were formed on the steel surface, none iron oxide was detected on the boronized surface. At 500° C, while only pure bulk -Fe2O3 was detected on the steel surface, a particle size distribution of-Fe2O3, with particle size of about 100 Å, was probably formed on the boronized surface, as evidenced by CEMS. 相似文献
13.
Maíra A. Carvalho Joo Bosco P. Da Silva Marcelo Z. Hernandes 《International journal of quantum chemistry》2005,102(4):379-386
The molecular electrostatic potential (MEP) of the indole molecule was calculated in a three‐dimensional grid in which the molecule was centered at the origin. To evaluate the dependence of MEP on the type of calculation, semiempirical, ab initio, and density functional theory methods with different basis sets were employed. The data matrix generated by these calculations was analyzed by principal component analysis (PCA). The appearance of outliers and the effect of wavefunction modifications such as the introduction of electron correlations and diffuse functions were highlighted by the use of PCA. The spatial localization of such effects around the molecule was possible from the loadings values associated with the graphical analysis of the grid points. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
14.
Gallium chloride is easily extracted from 6M HCl by comminuted polyether-type polyurethane foam. After the extraction step, the gallium absorbed by the PU foam can be quantitatively determined by X-ray fluorescence. A procedure for the direct determination of gallium absorbed by PU foam by XRFS is thus described. Gallium is determined at levels as low as 60 ng/ml (C(L)), with a calibration sensitivity of 424 cps ml/mug, within a linear range 0.1-2.30 mug/ml. The procedure investigated was successfully applied to determination of gallium in aluminum alloys, bauxite and industrial residue samples. 相似文献
15.
C. G. L. Canellas S. M. F. Carvalho E. F. O. De Jesus M. J. Anjos R. T. Lopes 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(3):631-634
Summary Major and trace elements were determined in serum of patients with chronic myelogenous leukemia (CML) using total reflection
X-ray fluorescence induced by synchrotron radiation (SRTXRF). CML affects 1 to 2 people per 100,000 and accounts for 7-20%
cases of leukemia. It was possible to determine the concentrations of the following elements: P, S, Cl, K, Ca, Cr, Mn, Fe,
Ni, Cu, Zn, Br and Rb. Using analysis of variance (ANOVA) it was observed that the contents of the P, S, Ca, Cr, Mn, Fe, Cu
and Rb elements differed significantly at a = 0.05 between groups of healthy subjects and CML patients and also genders (males
and females). 相似文献
16.
The purpose of this study is to investigate the influence of nickel, which is an alloying element in commonly used metallic biomaterials, on the biomaterials mineralization process. An electrochemical method was developed to quantify this metal ion in osteoblast-like cell culture medium (OST) by performing adsorptive cathodic stripping voltammetry (CSV) with dimethylglyoxime (DMG) at a mercury film microelectrode (MFM). The optimized analytical conditions and the square-wave CSV parameters for the analysis are: DMG concentration: 5.00 × 10−4 mol L−1; ammonium chloride buffer: 0.10 mol L−1 (pH 9.2); frequency: 50 Hz, amplitude 20 mV; step: 2 mV; adsorption time: 10 s, deposition potential: −0.70 V and reduction potential: −1.20 V. The limit of detection was 7.70 × 10−9 mol L−1 for an adsorption time of 10 s. The results achieved by CSV using the MFM were compared to those obtained by atomic absorption spectrometry (AAS) to ensure the reliability of the electrochemical method. The mineralization process was evaluated by biochemical and histochemical assays. 相似文献
17.
R. M. Parr A. Fajgelj R. Dekner H. Vera Ruiz F. P. Carvalho P. P. Povinec 《Analytical and bioanalytical chemistry》1998,360(3-4):287-290
For many years the International Atomic Energy Agency (IAEA) has been promoting analytical quality assurance and quality control in its Member States with emphasis on measurands that are amenable to analysis by nuclear and related techniques, i.e. radionuclides, trace elements, and stable isotopes. This paper reviews briefly the rationale for some of these activities, particularly in relation to the needs of participants in developing countries arising out of co-ordinated research programmes, technical co-operation projects and global and regional networks. Emphasis is given to biological and environmental reference materials with a matrix of natural origin. Also described are some activities arising out of the requirements of ISO-25 and other relevant international quality standards. 相似文献
18.
Immobilization of protein on ferromagnetic Dacron 总被引:1,自引:0,他引:1
A. M. A. Carneiro LeÃo E. A. Oliveira L. B. Carvalho 《Applied biochemistry and biotechnology》1991,31(1):53-58
Ferromagnetic Dacron (polyethyleneterephthalate) is proposed as a matrix to immobilize proteins covalently. Dacron in powder was magnetized by reacting ferrous (Fe+2) and ferric (Fe+3) ions with its hydrazide form at pH 8.3. Ferromagnetic hydrazide Dacron was converted to ferromagnetic azide Dacron and amyloglucosidase (E.C. 3.2.1.3) was covalently bound through the latter group. The catalytic property of the enzyme was preserved (8% of the specific activity estimated for the soluble enzyme) and all the magnetic amyloglucosidase Dacron derivative was recovered by using a magnetic field. No activity was detected in the supernatant. 相似文献
19.
Alpha emitters from uranium mining in the environment 总被引:1,自引:0,他引:1
Uranium mining and milling activities usually generate an enhancement of radionuclide concentrations in the environment that
may cause increased radiological exposure to mankind. For risk assessment and radiological protection of man and environment
in these areas, usually, it is needed to implement radiological surveillance of water, soils, agricultural products, aerosols,
and mining waste discharges as well. Radionuclides to be monitored in priority are alpha-emitting nuclides of the uranium
natural series. Radioactivity analysis of materials from uranium mining areas of Portugal shows departure from secular radioactive
equilibrium amongst uranium series radionuclides, thus rendering invalid the assumption of equilibrium and requiring the actual
determination of each radionuclide. Radionuclide measurements performed with high resolution alphaspectrometry, as reported
herein, produce accurate results on specific radionuclides that are essential in computing radiation doses to critical groups
of the population. 相似文献
20.
Abstract— Although the lex gene has been described until recently as being required for lysogenic induction, both our work and the work of others have reported Λ prophage induction in some lexA mutants. However, the characteristics of the process were not defined. We describe UV induction of prophage in a lexA1 mutant at a slightly lower level and requiring 2 times longer than the wild type. As demonstrated in some work, in cells treated with low levels of rifampicin (RIF) no new synthesis of RecA protein is needed for the prophage induction although the onset of lysis is delayed. We suggest that the lysogenic induction in lexA cells is due to the same mechanism that induces prophage in the wild type cells treated with RIF. That is, the induction is due to the cleavage of Λ represser by the basal RecA protease in the DNA-single-strand gap, since RecA protease and monomer represser both have high affinity for this type of DNA. So, LexA protein need not be cleaved for the prophage induction.
No Weigle-reactivation (WR) was detected in the lex mutant even after a long post-irradiation incubation, suggesting that unlike prophage induction, WR requires LexA protein cleavage. 相似文献
No Weigle-reactivation (WR) was detected in the lex mutant even after a long post-irradiation incubation, suggesting that unlike prophage induction, WR requires LexA protein cleavage. 相似文献