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991.
992.
Ch. Loppacher M. Bammerlin M. Guggisberg E. Meyer H.-J. Güntherodt R. Lüthi R. Schlittler J.K. Gimzewski 《Applied Physics A: Materials Science & Processing》2001,72(7):S105-S108
Combined STM/AFM experiments were performed on monolayer islands of Cu-TBPP molecules on Cu(100). Pulling of single molecules on the substrate was observed and the imaging parameters were compared to STM studies. Local frequency shift vs. distance curves reveal three types of curves, which can be related to the interaction of the tip above the Cu(100) substrate, the centre of the molecule and the leg of the molecule. The frequency vs. distance curves above the legs reveal two minima, which are associated with the bending of the legs above a certain threshold value. Quantitative analysis yields force values of about 0.4 nN. 相似文献
993.
A. G. Belov Yu. P. Gangrsky L. M. Melnikova V. Yu. Ponomarev N. Tsoneva Ch. Stoyanov A. Tonchev N. Balabanov 《Physics of Atomic Nuclei》2001,64(11):1901-1908
Isomeric ratios were measured for N=81 isotones (135Xe, 137Ba, 139Ce, 141Nd, 143Sm). In the experiment reported here, μ ν ≤3±10? J π=11/2? isomers were excited in (n, γ) and (γ, n) reactions and in the β + decay of 139Pr and 141Pm. In order to determine the reaction yields, use was made of the activation method involving measurement of the gamma-ray spectra of reaction products. It is found that, in the same reactions, isomeric ratios are different for isotones characterized by different atomic numbers Z. Isomeric ratios were calculated with the spectra of low-lying levels and radiative-transition probabilities established on the basis of the quasiparticle-phonon model. Good agreement between the experimental and calculated values of isomeric ratios is obtained for all isotopes invesigated here. The dependence of isomeric ratios on the atomic number Z of a nucleus is explained by the difference of reaction energies, which leads to different probabilities of excitation of activation levels through which the isomers being considered are populated. 相似文献
994.
M.N. Mineva M. Hellström M. Bernas J. Gerl H. Grawe M. Pfützner P.H. Regan M. Rejmund D. Rudolph F. Becker C.R. Bingham T. Enqvist B. Fogelberg H. Gausemel H. Geissel J. Genevey M. Górska R. Grzywacz K. Hauschild Z. Janas I. Kojouharov Y. Kopatch A. Korgul W. Korten J. Kurcewicz M. Lewitowicz R. Lucas H. Mach S. Mandal P. Mayet C. Mazzocchi J.A. Pinston Zs. Podolyàk H. Schaffner Ch. Schlegel K. Schmidt K. Sümmerer H.J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2001,11(1):9-13
Rapidity correlations in 800 GeV proton interactions with emulsion nuclei are investigated for different targets and multiplicity
regions. To study the energy dependence, the results have been compared with proton interactions at 200 GeV and 400 GeV. A
common feature of all the interactions is the existence of strong, short-range correlations. However, no dependence of cluster
parameters on primary energy or target mass is found. A marginal increase of correlation strength with multiplicity is observed.
Received: 30 March 2001 / Accepted: 18 September 2001 相似文献
995.
Mar'yana Lukachuk Birgit Heying Ute Ch. Rodewald Rainer Pttgen 《Heteroatom Chemistry》2005,16(5):364-368
The ternary indides Sc5 Ni2 In4 and Sc5 Rh2 In4 were synthesized by arc‐melting of the elements and subsequent annealing. A structural investigation by X‐ray powder and single crystal diffraction revealed: Lu5 Ni2 In4 type, Pbam, a = 1716.3(2), b = 755.1(1), c = 335.22(5) pm, wR2 = 0.0721, 844 F2 values for Sc5 Ni2 In4, and a = 1754.3(3), b = 765.0(1), c = 332.97(6) pm, wR2 = 0.0363, 1107 F2 values for Sc5 Rh2 In4 with 36 variables per refinement. Both structures can be described as intergrowths of distorted AlB2‐ and CsCl‐related slabs, where the transition metal (T) atoms have a trigonal prismatic and the indium atoms a distorted square prismatic coordination. The shortest interatomic distances occur for Sc T and T In. The crystal chemistry and chemical bonding in these intermetallics are briefly discussed. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:364–368, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20106 相似文献
996.
Johannis Ch. Simitzis Loukas Th. Zoumpoulakis Spiridon K. Soulis Leonidas N. Mendrinos 《Mikrochimica acta》2001,136(3-4):171-174
Unsaturated polyesters are synthesized by means of polyesterification, often with catalysts like strong acids, metal oxides
and metal-organic salts. Most often, the catalysts used cannot be separated from the bulk of the polyester. Also, some organic
or inorganic additives – called fillers – which are used with the polyester in order to decrease cost, affect the curing of
the polyester. In this work the effect of residual catalyst on the curing of unsaturated polyester is studied. Unsaturated
polyesters were prepared using propylene glycol with a 10% molar excess over stoichiometry and a mixture of dicarboxylic acids,
namely maleic acid (unsaturated) adipic acid (saturated) and phthalic anhydride (saturated) at a molar ratio 1:2:2. Lead dioxide,
p-toluenesulfonic acid and zinc acetate were used as catalysts, at 0.1% w/w. After the polyesterification, the polymers were
diluted with styrene at a proportion of 100:30 w/w. The resins were cured by using MEKP (methylethylketone peroxide) as initiator
and CoNp (cobalt naphthenate) as accelerator. Catalysts affect the final color of the polyester. The kinetics of curing of
the resins was studied by DSC analysis based on the exothermic peak due to the double bonds breaking to give crosslinked macromolecules.
The heat released ΔH is decreased by the presence of catalyst, while activation energy, the frequency factor and the order of reaction are increased. 相似文献
997.
J. Ch. Abbe 《Journal of Radioanalytical and Nuclear Chemistry》2001,249(3):565-567
Analyses of uranium and thorium by delayed neutron counting are described.The experimental system comprises an automatic pneumatic transfer system associatedwith a device made of twelve BF 3 neutron counters. Using homogeneous preparedsolutions of the samples, the analyses were based on a triple cycle each including60-second irradiation followed by 1-second cooling and 60-second counting.In these conditions, the limit of detection of uranium is about 0.3 µgwith a precision of measurement better than 10%. The contributions of possibleperturbations from 17 O(n,p)17 N reactions, followed by simultaneous –disintegration and neutron emission and from (n) reactions, have been studied. 相似文献
998.
B. Basnar J. Schnöller K. Föttinger G. Friedbacher U. Mayer H. Hoffmann L. Fabry 《Analytical and bioanalytical chemistry》2000,368(5):434-438
AFM imaging of the adsorption of self-assembled octadecylsiloxane (ODS) monolayers has been utilized for probing surface
properties of silicon wafers. It has been found that both growth rate of the organic films and island size of sub-monolayer
films are influenced by the doping level of the wafers as well as by the surface finishing step during wafer production. Generally,
higher doping levels led to lower adsorption rates and smaller islands. Variation of the sample pretreatment used for surface
finishing of similarly doped wafers led only to significant changes of the island size, but not of the surface coverage. The
results presented open up a valuable perspective for characterizing the surface homogeneity of silicon wafers which is an
important parameter for monitoring-wafers in semiconductor industry.
Received: 26 June 2000 / Revised: 26 July 2000 / Accepted: 1 August 2000 相似文献
999.
Vibrational circular dichroism (VCD) in the past two decades has developed into a powerful new structural tool. A concise
review of the applications of VCD to determine the structures of various biological molecules, namely peptides and proteins,
nucleic acids and carbohydrates, is provided.
Received: 31 August 1999 / Revised: 2 November 1999 / Accepted: 14 November 1999 相似文献
1000.
Fractions containing metallothioneins (MT’s), extracted from the liver cytosol of humans, were analysed to determine the complete distribution pattern of the metals copper, cadmium and zinc. Samples of cirrhotic livers which had come from organs removed during transplantation were examined for differences in the trace-element binding pattern. After the extraction of supernatants from the tissue samples, membrane ultrafiltration of the cytosolic solution was carried out to separate all high-molecular proteins with molecular weights >100 kDa. This procedure retains the metal content of the MT’s in its initial form, in contrast to the often-used heat treatment of samples, which changes the copper distribution significantly. The MT’s themself were isolated using size exclusion and anion exchange chromatography. Their metal content was determined simultaneously on-line by combination with an ICP-AES as element detector. Calibration of the procedure was performed by means of a column by-pass-injection of elemental standards into the separation system. The MT content in the samples was calculated using the determined metal concentrations and the generally accepted metal/protein ratios for Cu (12:1), Cd (7:1) and Zn (7:1). These values were compared with values resulting from a 109Cd-saturation-assay. When various liver samples of different pathogenesis were compared, the highest level of Cu-MT was found in primary biliary cirrhosis. 相似文献