全文获取类型
收费全文 | 1301篇 |
免费 | 97篇 |
国内免费 | 2篇 |
专业分类
化学 | 1057篇 |
力学 | 12篇 |
数学 | 85篇 |
物理学 | 246篇 |
出版年
2023年 | 15篇 |
2022年 | 37篇 |
2021年 | 48篇 |
2020年 | 44篇 |
2019年 | 50篇 |
2018年 | 22篇 |
2017年 | 21篇 |
2016年 | 68篇 |
2015年 | 61篇 |
2014年 | 59篇 |
2013年 | 73篇 |
2012年 | 98篇 |
2011年 | 119篇 |
2010年 | 73篇 |
2009年 | 37篇 |
2008年 | 69篇 |
2007年 | 87篇 |
2006年 | 59篇 |
2005年 | 53篇 |
2004年 | 33篇 |
2003年 | 39篇 |
2002年 | 35篇 |
2001年 | 29篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1997年 | 3篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1933年 | 3篇 |
1932年 | 4篇 |
1931年 | 3篇 |
排序方式: 共有1400条查询结果,搜索用时 15 毫秒
1.
Dr. Jordan Donat Mr. Patrick Dubourdeaux Dr. Martin Clémancey Dr. Julia Rendon Clara Gervasoni Mr. Morgan Barbier Jessica Barilone Dr. Jacques Pécaut Prof. Dr. Serge Gambarelli Prof. Dr. Pascale Maldivi Prof. Dr. Jean-Marc Latour 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202201875
Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two-electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor. 相似文献
2.
The Castelnuovo-Mumford regularity of a module gives a rough measure of its complexity. We bound the regularity of a module given a system of approximating modules whose regularities are known. Such approximations can arise naturally for modules constructed by inductive combinatorial means. We apply these methods to bound the regularity of ideals constructed as combinations of linear ideals and the module of derivations of a hyperplane arrangement as well as to give degree bounds for invariants of finite groups. 相似文献
3.
Jessica Strömbro Peter Gudmundson 《International Journal of Solids and Structures》2008,45(22-23):5765-5787
In this paper a simplified network model for mechano-sorptive creep is presented, which is a further development of an earlier paper [Strömbro, J., Gudmundson, P., 2008. Mechano-sorptive creep under compressive loading – a micromechanical model. International Journal of Solids and Structures 45 (9), 2420–2450.]. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys a constitutive law that is non-linear. Fibre kinks are included in order to capture experimental observations of larger mechano-sorptive effects in compression than in tension. Moisture dependent material parameters and anisotropy in the fibre distribution have been introduced. Theoretical predictions based on the model are compared to experimental results for an anisotropic paper both under tensile and compressive loading at varying moisture content and it is found that the important features in the experiments are captured by the model. Different kinds of drying conditions have also been examined. 相似文献
4.
It is shown that any local quantum field theory admits thermodynamical equilibrium states (KMS-states) for all positive temperatures provided it satisfies a nuclearity condition, proposed by Wichmann and one of the authors, which restricts the admissible number of local degrees of freedom.Dedicated to E. H. Wichmann on the occasion of his 60th birthday 相似文献
5.
Mathiazhagan C Molzon WR Cousins RD Konigsberg J Kubic J Melese P Rubin P Slater WE Wagner D Hart GW Kinnison WW Lee DM McKee RJ Milner EC Sanders GH Ziock HJ Arisaka K Knibbe P Urheim J Axelrod S Biery KA Irwin GM Lang K Margulies J Ouimette DA Ritchie JL Trang QH Wojcicki SG Auerbach LB Buchholz P Highland VL McFarlane WK Sivertz M Chapman MD Eckhause M Ginkel JF Hancock AD Joyce D Kane JR Kenney CJ Vulcan WF Welsh RE Whyley RJ Winter RG 《Physical review letters》1989,63(20):2181-2184
6.
This paper introduces a method of combining open and closed microchannels in a single component in a novel way which couples the benefits of both open and closed microfluidic systems and introduces interesting on-chip microfluidic behaviour. Fluid behaviour in such a component, based on continuous pressure driven flow and surface tension, is discussed in terms of cross sectional flow behaviour, robustness, flow-pressure performance, and its application to microfluidic interfacing. The closed-open-closed microchannel possesses the versatility of upstream and downstream closed microfluidics along with open fluidic direct access. The device has the advantage of eliminating gas bubbles present upstream when these enter the open channel section. The unique behaviour of this device opens the door to applications including direct liquid sample interfacing without the need for additional and bulky sample tubing. 相似文献
7.
Merkx M Kopp DA Sazinsky MH Blazyk JL Müller J Lippard SJ 《Angewandte Chemie (International ed. in English)》2001,40(15):2725
The cover picture shows in the background the whole cell of a methanotrophic bacterium on which are superimposed components of methane monooxygenase (the structure of the hydroxylase component (top), one of the two four-helix bundles that house the catalytic diiron centers (left)) and a schematic diagram of the catalytic cycle by which the enzyme converts dioxygen and methane into methanol and water. More about this unusual enzyme system is reported by Lippard et al. on p. 2782 ff. 相似文献
8.
S. Barlag H. Becker T. Böhringer M. Bosman V. Castillo V. Chabaud D. Buchholz C. Damerell C. Daum H. Dietl H. Fawcett S. Gill A. Gillman R. Gilmore T. Gooch L. Görlich P. Gras Z. Hajduk E. Higon B. D. Hyams D. P. Kelsey J. Kemmer R. Klanner U. Kötz S. Kwan B. Lücking G. Lütiens G. Lutz J. Malos W. Männer E. Neugebauer H. Palka M. Pepé J. Richardson G. De Rijk K. Rybicki H. J. Seebrunner U. Stierlin H. G. Tiecke M. Turala G. Waltermann S. Watts P. Weilhammer F. Wickens L. W. Wiggers A. Wylie T. Zeludziewicz ACCMOR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1987,37(1):17-23
We have measured the lifetimes of hadronically produced charged and neutralD mesons using silicon microstrip detectors and an active silicon target in the NA32 spectrometer at the CERN SPS. We obtainτ D± = (10.9± 1.5 1.9 )·10?13s andτ D (?)10 = (4.2±0.5)·10?13s based on 59 and 90 fully reconstructed decays respectively, giving a ratioτ D±/τ D (?)10 of 2.6 ±0.5. 相似文献
9.
Abramowicz H Belusevic R Blondel A Blümer H Böckmann P Brummel HD Buchholz P Burkhardt H Debu P Duda J Dydak F Falkenburg B Fiedler M Geiges R Geweniger C Grant AL Guyot C Hagelberg R Hepp V Hughes EW Kampschulte B Keilwerth H Kleinknecht K Knobloch J Krasny M Królikowski J Kurz N Lipniacka A Merlo J Müller E Para A Perez P Perrier F Pollman D Ranjard F Renk B Schuller J Taureg H Tittel K Turlay R Vallage B Wachsmuth H Wotschack J 《Physical review letters》1986,57(3):298-301
10.
It is shown that in a quantum field theory describing free, scalar particles with masses m
i
, i there exist locally normal equilibrium states with finite energy density for all temperature >0 if and only if
. This result lends support to the conjecture that the nuclearity criterion proposed by Buchholz and Wichmann is sensitive to the thermodynamical properties of field-theoretic models. 相似文献