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181.
Anjam Khursheed 《Optik》2009,120(6):280-288
This paper presents the design of a multi-beam charged particle instrument that simultaneously focuses electrons, gallium, oxygen and cesium ions onto the same sample. In addition, the instrument has provision to capture the spectra of both secondary electrons and ions in parallel. The mass spectrometer part of the instrument is expected to detect and identify secondary ion species across the entire range of the periodic table, and also record a portion of their emitted energy spectrum. The electron energy spectrometer part of the instrument is designed to acquire the entire range of scattered electrons, from the low-energy secondary electrons through to the elastic backscattered electrons. 相似文献
182.
We present a new method for resolving combinatorial ambiguities that arise in multi-particle decay chains at hadron colliders where the assignment of visible particles to the different decay chains has ambiguities. Our method, based on selection cuts favoring high transverse momentum and low invariant mass pairings, is shown to be significantly superior to the more traditional hemisphere method for a large class of decay chains, producing an increase in signal retention of up to a factor of 2. This new method can thus greatly reduce the combinatorial ambiguities of decay chain assignments. 相似文献
183.
Summary The combination affinity chromatography-mass spectrometry can be drastically improved by introducing a reversed phase column
prior to the mass spectrometric detection. The interactions of the macrocyclic antibiotic vancomycin with oligopeptides were
used to illustrate the performance of the technique. A library of 36 peptides was successfully screened and the active compounds
identified by electrospray MS(n). The strong affinity of compounds ending with (D)-alanine and with (D)-alanine or an aromatic (D)-amino acid in the penultimate
position with vancomycin was confirmed. 相似文献
184.
M. Mukherjee D. Beck K. Blaum G. Bollen J. Dilling S. George F. Herfurth A. Herlert A. Kellerbauer H. -J. Kluge S. Schwarz L. Schweikhard C. Yazidjian 《The European Physical Journal A - Hadrons and Nuclei》2008,35(1):1-29
ISOLTRAP is a Penning trap mass spectrometer for high-precision mass measurements on short-lived nuclides installed at the
on-line isotope separator ISOLDE at CERN. The masses of close to 300 radionuclides have been determined up to now. The applicability
of Penning trap mass spectrometry to mass measurements of exotic nuclei has been extended considerably at ISOLTRAP by improving
and developing this double Penning trap mass spectrometer over the past two decades. The accurate determination of nuclear
binding energies far from stability includes nuclei that are produced at rates less than 100 ions/s and with half-lives well
below 100ms. The mass-resolving power reaches 107 corresponding to 10keV for medium heavy nuclei and the uncertainty of the resulting mass values has been pushed down to below
10-8. The article describes technical developments achieved since 1996 and the present performance of ISOLTRAP. 相似文献
185.
A series of derivatisation reactions between p-t-butyl calix[4]arene and ethyl bromoacetate were carried out in order to prepare 1,3 diester substituted calix[4]arene. Mass spectral data, obtained from direct injection of samples, indicated that the reactions were rich in the desired product. Since the ultra violet (UV) spectra of the desired product and possible impurities are very similar, liquid chromatography (LC) chromatographic data seemed to corroborate these results. However, when on-line LC-UV-MS was carried out and each LC peak subjected to MS analysis as it eluted, a very different picture emerged. It was found that many of these reactions actually contained high levels of the monoester product which, having less affinity for sodium in the MS, is therefore seriously underestimated in any direct injection assay. LC-diode array detection (DAD) methods were also used to help successfully identify and characterise the compounds being formed in these complex reactions. The overall results obtained in this paper allowed the optimal reaction conditions to be determined for this reaction. LC-MS analysis of the chromatographic peaks also identified the presence of two isomers of the diester substituted calix[4]arene (1,3 and 1,2 diesters). The combination of LC and UV/MS detection is required for accurate analysis of the products of such reactions. 相似文献
186.
187.
本文研究了环状膦酸酯的合成方法,通过三种方法合成了十五个具有各种烷基结构的六元和七元环膦酸酯,并对这十五个化合物质谱作了分析和归纳,得出了一些有助于鉴定这类膦酸酯的质谱特征。 相似文献
188.
189.
Rat-mouse and mouse-mouse hybridoma cell lines were used for formation of monoclonal antibodies (MAbs) in microcapsules of
different sizes. Microcapsules were made of poly L-lysine-alginate hydrogel membranes. The effects of extracapsule liquid
film, intra-capsule and transmembrane transfer limitations of nutrients/products on system’s performance were investigated.
An agitation speed of 45 rpm (4 cm/s tip speed) was found to be optimal in spinner flasks to overcome liquid film resistances
around capsules. Capsule sizes need to be reduced to smaller than 350 ε in order to eliminate intracapsule transfer limitations
with a typical initial viable cell concentration of 0.5x105 viable cells/mL capsule. Double coating of capsules to improve strength of capsules resulted in higher transmembrane transfer
resistances. 相似文献
190.
Electron induced desorption of hydrogen on polycrystalline platinum has been studied in continuation of former work. The results
remain consistent with a supposed adsorption model implying that electron induced H+ emission is restricted to hydrogen adsorbed only at particular sites occupying not more than 1 per cent coverage. These sites
are ascribed to characteristic and stable surface impurities which are not influenced by the improved target treatment applied.
Depletion of sites by sputter cleaning is cancelled by recovery during annealing. The highest observed H+ yield (all available sites filled with hydrogen) is 2 · 10−5 ions per electron. The total cross section for desorption by electron impact is 2 · 10−17 cm2. Complex interaction phenomena between the electrons and the hydrogen covered platinum surface have been observed. 相似文献