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171.
R. Dybkaer 《Accreditation and quality assurance》2003,8(2):46-52
The establishment of a reference examination system necessary for metrological traceability of the many types of sophisticated
examination result in laboratory medicine is a daunting task, which has been made mandatory by the EU Directive on in vitro
diagnostic medical devices and the requirements for accreditation. Following a definition of examinand and allowed examination
uncertainty, a dedicated calibration hierarchy is established from stated reference through alternating reference examination
procedures and calibrators providing a traceability chain from examination result to the reference, often a definition of
a measurement unit. The various types of possible calibration hierarchy are outlined in EN ISO Standards. Recent efforts by
national and international stakeholders to establish a global reference examination system have led to the creation of a Joint
Committee on Traceability in Laboratory Medicine with the International Committee for Weights and Measures, International
Bureau of Weights and Measures, International Federation of Clinical Chemistry and Laboratory Medicine, International Laboratory
Accreditation Cooperation, and World Health Organization as the principal promoters. This structure will identify reference
procedures, reference materials, and reference laboratories, and seek support for further prioritised and coordinated development
of the system.
Received: 1 August 2002 Accepted: 22 November 2002
Based on a lecture at an IUPAC Seminar, EC JRC Institute for Reference Materials and Measurements, Geel, BE, 2001–12–18
Correspondence to R. Dybkaer 相似文献
172.
173.
Two parallel sets of CNDO/2 calculations have been carried out for 1H-5-aminotetrazole (1), 2-methyl-5-aminotetrazole (2), 1,3-dimethyl-5-aminotetrazolium cation (3) and the tetrazolate anion (4). In one set, the molecular geometry was represented by a regular pentagon 1·33 Å on a side, and in the other the experimentally determined molecular geometries were used. The calculated electronic structures from the two sets of calculations are compared; both sets predict similar trends in variation of atomic charges and bond indices with structure. Where comparison is possible, these trends seem to be generally in agreement with expectations based on classical concepts such as resonance. It is noted that the relative magnitudes of σ-electron bond indices seem to parallel those of the π-electron bond indices in many cases, although the σ-bond indices show much smaller variation in absolute magnitude as compared with the π-bond indices. A brief discussion of the relative merits of various geometrical models is presented; it is suggested that, in order to combine the advantages of both approaches, standard and experimentally-determined geometries should be used side-by-side whenever possible. A procedure for speeding convergence by use of a damping factor is described. 相似文献
174.
Within the energy range 17 hv < 35 eV, the ionic species desorbed and their excitation spectra are reported. The only positive ion desorbed is H+. A model for the surface is suggested which explains the absence of OH+ desorption. The desorption mechanisms are discussed in terms of an energy analysis. 相似文献
175.
Computer-aided interpretation of 13C-n.m.r. and i.r. spectra of organic molecules (m.w. ? 500) is done by an artificial intelligence approach. The output of the proposed ASSIGNER system is a list of functional groups which are reasonable candidates for the final structural isomers. The procedure of finding possible functional groups and the main features of the filtering steps are outlined. One search is worked out in detail to demonstrate the capability of the system. 相似文献
176.
The efficiency of the genotyping process is determined by many simultaneous factors. In actual genotyping, a production run
is often preceded by small-scale experiments to find optimal conditions. We propose to use statistical analysis of production
run data as well, to gain insight into factors important for the outcome of genotyping. As an example, we show that analysis
of variance (ANOVA) applied to the first-pass results of a genetic study reveals important determinants of genotyping success.
The largest factor limiting genotyping appeared to be interindividual variation among DNA samples, explaining 20% of the variance,
and a smaller reaction volume, sizing failure, and differences among markers all explained ∼10%. Other potentially important
factors, such as sample position within the plate and reusing electrophoresis matrix, appeared to be of minor influence. About
55% of the total variance could be explained by systematic factors. These results show that ANOVA can provide valuable feedback
to improve genotyping efficiency. We propose to adjust genotype production runs using principles of experimental design in
order to maximize genotyping efficiency at little additional cost. 相似文献
177.
The structure and absolute configuration of lupinifolin, (2S) - 4′,5 - dihydroxy - 8 - (3? - methyl - 2? - butenyl) - 2″, 2″ - dimethylpyrano[5″.6″ - g]flavanone, and lupinifolinol, (2R,3R) - 8 - (3? - methyl - 2? - butenyl) - 3,4′,5 - trihydroxy - 2″,2″ - dimethylpyrano[5″.6″ - g]flavanone, have been deduced from spectroscopic and chemical evidence. 相似文献
178.
Powder samples of FexTiSe2 (0.00 ≤ x ≤ 0.50) have been prepared by direct reaction of high purity elements. Crystal parameters were determined by the Debye-Scherrer powder diffraction technique. Magnetic susceptibility measurements were made by the Faraday method in the temperature range 1.5–300 K and indicated magnetic odering for compositions with x > 0.03. The magnetic ordering temperature, Tm, was observed to move to higher temperature with increasing iron concentration. These results have been interpreted in terms of a spin-glass model for low iron concentrations (x < 0.2) and antiferromagnetism for high concentrations (x > 0.2). 相似文献
179.
Marina Patriarca Ferdinando Chiodo Marco Castelli Federica Corsetti Antonio Menditto 《Microchemical Journal》2005,79(1-2):337
The Me.Tos. Project, started in 1983 and still running, is an external quality assessment (EQA) scheme for laboratories performing specialized analyses in occupational and environmental laboratory medicine. Besides the organization of EQA exercises, initiatives for further education of the participants and the harmonization of EQA procedures at a European level are carried out. Participation in EQA schemes allows laboratories to comply with the international standards for the quality and competence of testing and clinical laboratories. The organization of the scheme includes the preparation of control materials, their distribution to the participants, according to strategies aimed to avoid identification of the samples, the statistical analysis of the results and the evaluation of laboratories' performance according to international guidelines and criteria set by the organizers. An overview of the scheme operation and the current performances of participants will be given. 相似文献
180.
Excimer laser (ArF) photolysis of diatomic and triatomic hydrides produces hydrogen atoms with translational energies in excess of 15000 cm?1 per atom. Subsequent collisions of these “hot” atoms with CO2 and N2O produces vibrationally excited molecules which can be detected by their characteristic infrared emission. 相似文献