全文获取类型
收费全文 | 1164篇 |
免费 | 95篇 |
国内免费 | 5篇 |
专业分类
化学 | 881篇 |
晶体学 | 15篇 |
力学 | 18篇 |
数学 | 132篇 |
物理学 | 218篇 |
出版年
2023年 | 29篇 |
2022年 | 33篇 |
2021年 | 47篇 |
2020年 | 63篇 |
2019年 | 61篇 |
2018年 | 23篇 |
2017年 | 30篇 |
2016年 | 53篇 |
2015年 | 63篇 |
2014年 | 46篇 |
2013年 | 58篇 |
2012年 | 73篇 |
2011年 | 81篇 |
2010年 | 40篇 |
2009年 | 45篇 |
2008年 | 46篇 |
2007年 | 47篇 |
2006年 | 49篇 |
2005年 | 25篇 |
2004年 | 20篇 |
2003年 | 19篇 |
2002年 | 20篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 14篇 |
1998年 | 14篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1977年 | 15篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1937年 | 5篇 |
排序方式: 共有1264条查询结果,搜索用时 15 毫秒
101.
Litvinyuk IV Légaré F Dooley PW Villeneuve DM Corkum PB Zanghellini J Pegarkov A Fabian C Brabec T 《Physical review letters》2005,94(3):033003
Shakeup of a two-electron system is investigated in the strong infrared laser field limit, both theoretically and experimentally. During tunnel ionization the electron shakes up a second electron to an excited bound state. Theoretically, a complete analytical theory of shakeup in intense laser fields is developed. We predict that shakeup produces one excited sigma(u) D(+)(2) state in approximately 10(5) ionization events. Shakeup is measured experimentally by using the molecular clock provided by the internuclear motion. The number of measured events is found to be in excellent agreement with theory. 相似文献
102.
It is proved that a Banach space X is a subspace of a weaklycompactly generated Banach space if and only if, for every >0,X can be covered by a countable collection of bounded closedconvex symmetric sets where the weak* closure in X** of eachof them lies within the distance from X. A new short functional-analyticproof of the known result that a continuous image of an Eberleincompact is Eberlein is given as a corollary. 相似文献
103.
Fabian Jachmann 《Solid State Communications》2007,142(4):212-216
In a thin film of superconducting Y Ba2Cu3O7 the impact of surface acoustic waves (SAWs) traveling on the piezoelectric substrate is investigated. A pronounced interaction between the ultrasonic waves and the vortex system in the type II superconductor is observed. The occurrence of a SAW-induced dc voltage perpendicular to the sound path is interpreted as dragging of vortices by the piezoacoustic SAW, which acts as a conveyor for the flux quanta. The antisymmetry of this voltage with respect to the magnetic field directly evidences the induced, directed flux motion. This dynamic manipulation of vortices can be seen as an important step towards flux-based electronic devices. 相似文献
104.
Ahmed Al‐Harrasi Dr. Fabian Pfrengle Dipl.‐Chem. Vladimir Prisyazhnyuk Dr. Shahla Yekta Dr. Peter Koóš Dr. Hans‐Ulrich Reissig Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11632-11641
1,3‐Dioxolanyl‐substituted 1,2‐oxazines, such as syn‐ 1 and anti‐ 1 , rearrange under Lewis acidic conditions to provide bicyclic products 2 – 5 . Subsequent reductive transformations afforded enantiopure 3‐aminopyran derivatives such as 7 and 9 or their protected diastereomers 16 and 18 , which can be regarded as carbohydrate mimetics. An alternative sequence of transformations including selective oxidation of the primary hydroxyl groups in 21 and 24 led to two protected β‐amino acid derivatives with carbohydrate‐like backbone (sugar amino acids). Treatment of bicyclic ester 23 with samarium diiodide cleaved the N? O bond and furnished the unusual β‐lactam 27 in excellent yield. Alternatively, γ‐amino acid derivative 29 was efficiently prepared in a few steps. Fairly simple transformations gave azides 32 and 35 or alkyne 30 which are suitable substrates for the construction of oligosaccharide mimetics such as 34 by copper iodide catalyzed cycloadditions. With this report we demonstrate that enantiopure rearrangement products 2 – 5 are protected precursors of a variety of polyfunctionalized pyran derivatives with great potential for chemical biology. 相似文献
105.
A. R. Godfrey C. M. Williams E. Dudley R. P. Newton P. Willshaw A. Mikhail L. Bastin A. G. Brenton 《Rapid communications in mass spectrometry : RCM》2009,23(19):3194-3204
Historically, structural elucidation of unknown analytes by mass spectrometry alone has involved tandem mass spectrometry experiments using electron ionization. Most target molecules for bioanalysis in the metabolome are unsuitable for detection by this previous methodology. Recent publications have used high‐resolution accurate mass analysis using an LTQ‐Orbitrap with the more modern approach of electrospray ionization to identify new metabolites of known metabolic pathways. We have investigated the use of this methodology to build accurate mass fragmentation maps for the structural elucidation of unknown compounds. This has included the development and validation of a novel multi‐dimensional LC/MS/MS methodology to identify known uremic analytes in a clinical hemodialysate sample. Good inter‐ and intra‐day reproducibility of both chromatographic stages with a high degree of mass accuracy and precision was achieved with the multi‐dimensional liquid chromatography/tandem mass spectrometry (LC/MS/MS) system. Fragmentation maps were generated most successfully using collision‐induced dissociation (CID) as, unlike high‐energy CID (HCD), ions formed by this technique could be fragmented further. Structural elucidation is more challenging for large analytes >270 Da and distinguishing between isomers where their initial fragmentation pattern is insufficiently different. For small molecules (<200 Da), where fragmentation data may be obtained without loss of signal intensity, complete structures can be proposed from just the accurate mass fragmentation data. This methodology has led to the discovery of a selection of known uremic analytes and two completely novel moieties with chemical structural assignments made. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
106.
107.
L. Nyulászi T. Pasinszki J. Réffy T. Veszprémi J. Fabian W. Thiel 《Structural chemistry》1990,1(4):367-370
The Hel UPS spectra of acetamidine, perimidine, and four 2-substituted perimidine derivatives have been recorded and interpreted using ab initio and MNDO quantum-chemical calculations. A large interaction between the naphthalene and amidine fragment was concluded from the lowest ionization energy. The color-determining band of these compounds is strongly affected by the intramolecular charge-transfer transitions, which are of low energy because of the low ionization energy of the perimidine moiety. 相似文献
108.
109.
110.
Fabian H. Gaioli Edgardo T. Garcia Alvarez Diego G. Arbo 《International Journal of Theoretical Physics》1999,38(1):183-198
This paper generalizes some previous resultspresented in Gaioli et al. [Int. J. Theor. Phys. 36,2167 (1997)]. We evaluate the autocorrelation functionof the stochastic acceleration and study the asymptotic evolution of the mean occupation number of aharmonic oscillator playing the role of a Brownianparticle. We also analyze some deviations from the Bosepopulation at low temperatures and compare it with the deviations from the exponential decay lawof an unstable quantum system. 相似文献