全文获取类型
收费全文 | 425篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 247篇 |
晶体学 | 4篇 |
力学 | 13篇 |
数学 | 101篇 |
物理学 | 79篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 12篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 19篇 |
2015年 | 13篇 |
2014年 | 22篇 |
2013年 | 20篇 |
2012年 | 28篇 |
2011年 | 33篇 |
2010年 | 20篇 |
2009年 | 22篇 |
2008年 | 24篇 |
2007年 | 23篇 |
2006年 | 28篇 |
2005年 | 21篇 |
2004年 | 25篇 |
2003年 | 23篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1965年 | 1篇 |
1962年 | 2篇 |
排序方式: 共有444条查询结果,搜索用时 31 毫秒
131.
Hans-Dieter Martin Franz-Josef Mais Bernhard Mayer Hans-Jürgen Hecht Mirko Hekman Alois Steigel 《Monatshefte für Chemie / Chemical Monthly》1983,114(10):1145-1147
Cycloaddition of diphenylnitrile ylide to dicyanocyclobutene and of a mesoionic oxazolium-5-olate to isopropylidenecyclobutenone yields dihydroazepine derivatives by cleavage of the strained internal σ-bonds in the primarily formed bicyclic adducts. 相似文献
132.
133.
In continuous slab casting, the liquid steel is introduced into the mould via a submergered entry nozzle. This nozzle usually has two opposed orifices on its side walls, generating two diametrically opposed turbulent jets that are declined about 20° to the horizontal axis. These jets interact with the surrounding walls of the mould, which leads to an unstable flow situation and a self induced oscillation of the jets. Although both mould and nozzle geometry have two perpendicular symmetry planes, the oscillations are asymmetric. The fluid flow inside the mold is calculated with a 3D finite volume solver using turbulence models based on Reynolds-averaging. The massflow of the jets and the mould extensions are varied, and the numerical results are partially compared with PIV-measurements at a 1:1 scaled watermodel of the mould. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
134.
On bipartite graphs with small number of laplacian eigenvalues greater than two and three 总被引:2,自引:0,他引:2
Miroslav Petrovi Ivan Gutman Mirko Lepovi Bojana Mileki 《Linear and Multilinear Algebra》2000,47(3):205-215
All connected bipartite graphs with exactly two Laplacian eigenvalues greater than two are determined. Besides, all connected bipartite graphs with exactly one Laplacian eigenvalue greater than three are determined. 相似文献
135.
Caterina Brandmayr Mirko Wagner Tobias Brückl Daniel Globisch David Pearson Andrea Christa Kneuttinger Veronika Reiter Antje Hienzsch Susanne Koch Ines Thoma Peter Thumbs Stylianos Michalakis Markus Müller Martin Biel Thomas Carell 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(44):11324-11328
136.
This work reports on a novel, hybrid solid-state membrane based on sulfated titania nanoparticles stabilized by a polyvinylidene fluoride–hexafluoropropylene copolymer. A fast solvent-casting technique was adopted as a valid alternative to a fully dry, hot-pressing preparation procedure. Self-standing, flexible membranes with high proton conductivity were obtained. 相似文献
137.
M. Chem. Caterina Brandmayr Dipl.‐Chem. Mirko Wagner Dr. Tobias Brückl Dr. Daniel Globisch Dr. David Pearson M. Sc. Andrea Christa Kneuttinger Dipl.‐Chem. Veronika Reiter Dr. Antje Hienzsch Dipl.‐Biol. Susanne Koch M. Sc. Ines Thoma Dipl.‐Chem. Peter Thumbs Dr. Stylianos Michalakis Dr. Markus Müller Prof. Dr. Martin Biel Prof. Dr. Thomas Carell 《Angewandte Chemie (International ed. in English)》2012,51(44):11162-11165
138.
Rita Traversi Silvia Becagli Emiliano Castellano Ombretta Largiuni Alessio Migliori Mirko Severi 《International journal of environmental analytical chemistry》2013,93(6-7):457-470
The chemical analysis of shallow firn cores sampled in coastal and plateau areas in Northern Victoria Land and along a transect from Talos Dome to Dome C (East Antarctica, Pacific Ocean sector) allowed a global view of spatial and temporal changes in chemical composition of snow depositions over the last 100 years. Variations in concentration of primary (sea spray) and secondary (biogenic emission, atmospheric inputs) source markers were observed and discussed as a function of distance from the sea and altitude. In the stations characterized by relatively high snow accumulation rates, the sub-sampling resolution was sufficient to obtain a stratigraphic dating by using the periodical variations of seasonal markers. In these stations, a subdivision in “summer” and “winter” samples was carried out in order to study the seasonal changes of the contributions of the measured compounds to the snow composition as elevation and distance from the sea increase. Some evidence of post-depositional effects which are able to change the original deposition of chloride and nitrate, was observed at stations with low accumulation rates. The reliability of the depth/concentration profile of these substances for reconstructing past deposition was also discussed. 相似文献
139.
Mirko Boezio 《Brazilian Journal of Physics》2014,44(5):441-449
Cosmic rays are a sample of solar, galactic, and extragalactic matter. Their origin, acceleration mechanisms, and subsequent propagation toward Earth have intrigued scientists since their discovery. These issues can be studied via analysis of the energy spectra and composition of cosmic rays. Protons are the most abundant component of the cosmic radiation, and many experiments have been dedicated to the accurate measurement of their spectra. Complementary information is provided by electrons, which comprise about 1 % of the cosmic radiation. Because of their low mass, electrons experience severe energy losses through synchrotron emission in the galactic magnetic field and inverse Compton scattering of radiation fields. Electrons therefore provide information on the local galactic environment that is not accessible from the study of the cosmic ray nuclei. Antiparticles, namely antiprotons and positrons, are produced in the interaction between cosmic ray nuclei and the interstellar matter. They are therefore intimately linked to the propagation mechanisms of the parent nuclei. Novel sources of primary cosmic ray antiparticles of either astrophysical (e.g., positrons from pulsars) or exotic origin (e.g., annihilation of dark matter particles) may exist. The nature of dark matter is one of the most prominent open questions in science today. An observation of positrons from pulsars would open a new observation window on these sources. Several experiments equipped with state-of-the art detector systems have recently presented results on the energy spectra of electrons, protons, and their antiparticles with a significant improvement in statistics and better control of systematics. The status of the field will be reviewed, with a focus on these recent scientific results. 相似文献
140.
The filtration of airborne nanoparticles is an important control technique as the environmental, health, and safety impacts of nanomaterials grow. A review of the literature shows that significant progress has been made on airborne nanoparticle filtration in the academic field in the recent years. We summarize the filtration mechanisms of fibrous and membrane filters; the air flow resistance and filter media figure of merit are discussed. Our review focuses on the air filtration test methods and instrumentation necessary to implement them; recent experimental studies are summarized accordingly. Two methods using monodisperse and polydisperse challenging aerosols, respectively, are discussed in detail. Our survey shows that the commercial instruments are already available for generating a large amount of nanoparticles, sizing, and quantifying them accurately. The commercial self-contained filter test systems provide the possibility of measurement for particles down to 15 nm. Current international standards dealing with efficiency test for filters and filter media focus on measurement of the minimum efficiency at the most penetrating particle size. The available knowledge and instruments provide a solid base for development of test methods to determine the effectiveness of filtration media against airborne nanoparticles down to single-digit nanometer range. 相似文献