全文获取类型
收费全文 | 815篇 |
免费 | 36篇 |
国内免费 | 3篇 |
专业分类
化学 | 501篇 |
晶体学 | 38篇 |
力学 | 4篇 |
数学 | 82篇 |
物理学 | 229篇 |
出版年
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2017年 | 7篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 29篇 |
2013年 | 37篇 |
2012年 | 26篇 |
2011年 | 26篇 |
2010年 | 18篇 |
2009年 | 24篇 |
2008年 | 22篇 |
2007年 | 26篇 |
2006年 | 20篇 |
2005年 | 29篇 |
2004年 | 28篇 |
2003年 | 26篇 |
2002年 | 20篇 |
2001年 | 15篇 |
2000年 | 11篇 |
1999年 | 19篇 |
1998年 | 8篇 |
1997年 | 14篇 |
1996年 | 8篇 |
1995年 | 20篇 |
1994年 | 13篇 |
1993年 | 16篇 |
1992年 | 15篇 |
1991年 | 17篇 |
1990年 | 21篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 17篇 |
1977年 | 17篇 |
1976年 | 16篇 |
1975年 | 16篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1967年 | 7篇 |
1933年 | 5篇 |
排序方式: 共有854条查询结果,搜索用时 31 毫秒
61.
62.
T. Schröder W. Rudolph S. V. Govorkov I. L. Shumay 《Applied Physics A: Materials Science & Processing》1990,51(1):49-51
Primary steps of melting (disordering) of GaAs surface layers after femtosecond pulse excitation have been measured through second-harmonic generation in reflection. A numerical fit of the experimental data yield a characteristic time delay between excitation and lattice melting of about 75 fs. 相似文献
63.
64.
L. Knudsen U. Kreusler Giroud Hugo Schiff N. A. Rudolph Richard Schulze Ad. Blümcke N. A. Randolph Lothar Meyer Andreas Fock Victor Meyer Richard Anschütz und Aug Kekulé 《Fresenius' Journal of Analytical Chemistry》1886,25(1):382-394
Ohne Zusammenfassung 相似文献
65.
Wolfram W. Rudolph 《Journal of solution chemistry》2010,39(7):1039-1059
Measurements have been made of the Raman spectra of aqueous solutions of Be(ClO4)2, BeCl2, (NH4)2SO4 and BeSO4 to 50 cm−1. In some cases low concentrations (0.000770 mol⋅kg−1) have been used and two temperatures (23 and 40 °C) were studied. In BeSO4(aq), the ν
1-SO42-\mathrm{SO}_{4}^{2-} mode at 980 cm−1 broadens with increasing concentration and shifts to higher wavenumbers. At the same time, a band at 1014 cm−1 is detectable with this mode being assigned to [BeOSO3], an inner-sphere complex (ISC). Confirmation of this assignment is provided by the simultaneous appearance of stretching
bands for the Be2+-OSO32-\mathrm{Be}^{2+}\mbox{-}\mathrm{OSO}_{3}^{2-} bond of the complex at 240 cm−1 and for the BeO4 skeleton mode of the [(H2O)3BeOSO3] unit at 498 cm−1. The ISC concentration increases with higher temperatures. The similarity of the n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} Raman bands for BeSO4 in H2O and D2O is further strong evidence for formation of an ISC. After subtraction of the ISC component at 1014 cm−1, the n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} band in BeSO4(aq) showed systematic differences from that in (NH4)2SO4(aq). This is consistent with a n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} mode at 982.7 cm−1 that can be assigned to the occurrence of an outer-sphere complex ion (OSCs). These observations are shown to be in agreement
with results derived from previous relaxation measurements. Infrared spectroscopic data show features that are also consistent
with a beryllium sulfato complex such as the appearance of a broad and weak n1-SO42-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} mode at ∼1014 cm−1, normally infrared forbidden, and a broad and asymmetric n3-SO42-\nu_{3}\mbox{-}\mathrm{SO}_{4}^{2-} band contour which could be fitted with four band components (including n3-SO42-(aq)\nu_{3}\mbox{-}\mathrm{SO}_{4}^{2-}(\mathrm{aq})). The formation of ISCs in BeSO4(aq) is much more pronounced than in the similar MgSO4(aq) system studied recently. 相似文献
66.
The F(-), Cl(-), and Br(-) binding selectivity of bis(p-nitroanilide)s of dipicolinic and isophthalic acids was studied by using competitive electrospray mass spectrometry and UV-Visible spectroscopy. Both hosts prefer binding Cl(-) over either F(-) or Br(-). Host deprotonation was observed to some extent in all experiments in which the host was exposed to halide ions. When F(-) was present, host deprotonation was often the major process, whereas little deprotonation was observed by Cl(-) or Br(-), which preferred complexation. A solution of either host changed color when mixed with a F(-), H(2)PO(4)(-), di- or triphenylacetate solution. 相似文献
67.
This contribution deals with the modelling and simulation of curing phenomena in adhesively bonded piezo metal composites which consists of a piezoelectric module enclosed by an adhesive layer which in turn is surrounded by two metal sheets. A short survey on the neccessary experimental investigations to characterise the adhesive's material behaviour is given and important aspects on the corresponding phenomenological modelling approach are presented. Both steps take into account the curing reaction, changes of volume, like chemical shrinkage, and inelastic mechanical behaviour which is temperature and curing dependent. Finally, the simulation strategy for the modelling within a finite element environment is depicted. By this, residual stresses, secondary deformations and loads on the piezo modules can be predicted, which is exemplified by a comparative study verifying a novel manufacturing strategy. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
68.
Univariate Gonarov polynomials arose from the Gonarov interpolation problem in numerical analysis.They provide a natural basis of polynomials for working with u-parking functions,which are integer sequences whose order statistics are bounded by a given sequence u.In this paper,we study multivariate Gonarov polynomials,which form a basis of solutions for multivariate Gonarov interpolation problem.We present algebraic and analytic properties of multivariate Gonarov polynomials and establish a combinatorial relation with integer sequences.Explicitly,we prove that multivariate Gonarov polynomials enumerate k-tuples of integers sequences whose order statistics are bounded by certain weights along lattice paths in Nk.It leads to a higher-dimensional generalization of parking functions,for which many enumerative results can be derived from the theory of multivariate Gonarov polynomials. 相似文献
69.
Sebastien Graule Mark Rudolph Wenting Shen J. A. Gareth Williams Dr. Christophe Lescop Dr. Jochen Autschbach Prof. Jeanne Crassous Dr. Régis Réau Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(20):5976-6005
Aza[n]helicene phosphole derivatives have been prepared from aza[n]helicene diynes by the Fagan–Nugent route. Their photophysical properties (UV/Vis absorption and emission behavior) have been evaluated. Their behavior as P,N chelates towards coordination to PdII and CuI has been investigated: metal–bis(aza[n]helicene phosphole) assemblies are formed by a highly stereoselective coordination process, as demonstrated by X‐ray crystallography. An aza[6]helicene phosphole bearing an enantiopure helicene part has been obtained, which allows the preparation of enantiopure PdII and CuI complexes with original topologies and high molar rotation (MR) and circular dichroism (CD). The structure–property relationship established from the experimental data has been studied in detail by theoretical studies (TDDFT calculations of UV/Vis, CD, and MR). Aza[n]helicene phosphole derivatives show π conjugation extended over the entire molecule, and its influence on the MR of aza[6]helicene phosphole 5 c has been demonstrated. Finally, it has been shown that the nature of the metal (coordination geometry and electronic interaction) can have a great impact on the amplitude of the chiroptical properties in metal–bis(aza[n]helicene phosphole) assemblies. 相似文献
70.
Jan P. Weyrauch Dr. A. Stephen K. Hashmi Prof. Dr. Andreas Schuster Dipl.‐Chem. Tobias Hengst Dipl.‐Chem. Stefanie Schetter Anna Littmann Dipl.‐Chem. Matthias Rudolph Dr. Melissa Hamzic Dr. Jorge Visus Jan W. Bats Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(3):956-963
The substrate scope, the mechanistic aspects of the gold‐catalyzed oxazole synthesis, and substrates with different aliphatic, aromatic, and functional groups in the side chain were investigated. Even molecules with several propargyl amide groups could easily be converted, delivering di‐ and trioxazoles with interesting optical properties. Furthermore, the scope of the gold(I)‐catalyzed alkylidene synthesis was investigated. Further functionalizations of these isolable intermediates of the oxazole synthesis were developed and chelate ligands can be obtained. The use of Barluenga’s reagent offers a new and mild access to the synthetically valuable iodoalkylideneoxazoles from propargylic amides, this reagent being superior to other sources of halogens. 相似文献