全文获取类型
收费全文 | 347篇 |
免费 | 3篇 |
国内免费 | 3篇 |
专业分类
化学 | 150篇 |
力学 | 6篇 |
数学 | 74篇 |
物理学 | 123篇 |
出版年
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 14篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 11篇 |
2012年 | 19篇 |
2011年 | 23篇 |
2010年 | 5篇 |
2009年 | 13篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 19篇 |
2005年 | 15篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 7篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1955年 | 1篇 |
1926年 | 1篇 |
1922年 | 2篇 |
排序方式: 共有353条查询结果,搜索用时 15 毫秒
101.
Despoina Vrantza Panagiotis Kaloudis Leondios Leondiadis Thanasis Gimisis GeorgiosC. Vougioukalakis Michael Orfanopoulos Didier Gasparutto Jean Cadet Susana Encinas Cecilia Paris MiguelA. Miranda 《Helvetica chimica acta》2006,89(10):2371-2386
The photochemistry of N‐hydroxypyridine‐2(1H)‐thione (NHPT), inserted as a photolabile modifier at the 6‐position of 2′‐deoxyguanosine or guanosine, has been evaluated. In particular, 6‐[(1‐oxidopyridin‐2‐yl)sulfanyl]‐ ( 1a ) and 6‐[(pyridin‐2‐yl)sulfanyl]‐2′,6‐dideoxyguanosine ( 2a ), novel photolabile derivatives of the natural nucleosides, were synthesized and characterized. The observed photolysis products of 1a in organic solvents could only be rationalized by assuming a rapid equilibrium with the corresponding 6‐[(2‐thioxopyridin‐1(2H)‐yl)oxy] analogue 3a (Scheme 5). Transient spectroscopy of 1a indicated a strong triplet‐excited state suitable for triplet → triplet energy transfer or singlet‐oxygen generation. The NHPT function was stable enough for (slightly modified) automated solid‐phase oligonucleotide synthesis. The utility of the above compounds is discussed, as well as their potential use in photosensitization of reactive oxygen species in DNA. 相似文献
102.
Wise CA Paris M Morar B Wang W Kalaydjieva L Bittles AH 《Rapid communications in mass spectrometry : RCM》2003,17(11):1195-1202
Analysis of single nucleotide polymorphisms (SNPs) has become an increasingly important area of research, with numerous applications in medical genetics, population genetics, forensic science, and agricultural biotechnology. Large-scale SNP analyses require the development of methodologies that are economical, flexible, accurate and capable of automation. Primer extension in conjunction with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is currently emerging as a potential method for high-throughput SNP genotyping. We have evaluated a number of published primer extension methods and refined a simple and robust protocol to analyze human autosomal disease-causing mutations and population genetic markers on the Y-chromosome. Twelve different variant sites were examined, and homozygotes, heterozygotes and hemizygotes were accurately typed. A 100% concordance was observed between SNP genotypes obtained using the MALDI-TOFMS technique and alternative genotyping methods, such as restriction fragment length polymorphism (RFLP) assays and denaturing high-performance liquid chromatography (DHPLC). Since multiple polymorphisms can be detected in single reactions, the method provides a cost-effective approach for SNP analysis. The protocol is also extremely flexible (able to accommodate new markers) and can be adapted to a number of platforms without the use of commercial kits. 相似文献
103.
E.C. Paris J.W.M. Espinosa S. de Lazaro R.C. Lima M.R. Joya P.S. Pizani E.R. Leite A.G. Souza J.A. Varela E. Longo 《Chemical physics》2007
Er3+ ions were added to the PbTiO3 network using the polymeric precursor method to characterize the order–disorder transformation found in this material by means of experimental and theoretical approach. The disordered and ordered material structures were studied by photoluminescence measurements, X-ray diffraction (XRD) and UV–visible spectroscopy. The Er3+ ions served as a marker to identify the structural short-range order beginning in the PbTiO3 matrix. From photoluminescence results it was concluded that disordered PbTiO3 powders have a certain short range order in the network that are undetected by XRD measurements. The electronic structures were calculated by the ab initio periodic method in DFT level with the non-local B3LYP hybrid approximation for the Ti atom site interpretation using density of states (DOS) results. This analysis enabled understanding that Ti atom sphere coordination can create possible states for radioactive return and trap of electron–holes pair. 相似文献
104.
West C Cilpa G Gaudin K Chaminade P Lesellier E;Groupe de chimie Analytique de Paris Sud 《Journal of chromatography. A》2005,1087(1-2):77-85
Interactions of solutes on porous graphitic carbon (PGC) with non-aqueous mobile phases are studied by the linear solvation energy relationship (LSER). Studies have been carried out with eight binary mixtures composed of a weak solvent (acetonitrile or methanol) and a strong solvent (tetrahydrofuran, n-butanol, CH2Cl2, 1,1,2-trichloro-2,2,1-trifluoroethane). The systematic analysis of a set of test compounds was performed for each solvent mixture in isocratic mode (50:50). The results were compared to those obtained on PGC with hydro-organic liquids and supercritical fluids. They were then correlated with the observed retention behaviour of lipid compounds, more particularly ceramides. 相似文献
105.
F. Becker W. Korten F. Hannachi P. Paris N. Buforn C. Chandler M. Houry H. Hübel A. Jansen Y. Le Coz C.F. Liang A. Lopez-Martens R. Lucas E. Mergel P. H. G. Schönwasser C. Theisen 《The European Physical Journal A - Hadrons and Nuclei》1999,4(2):103-105
The atomic nucleus 74Kr has been investigated using combined conversion-electron (CE) and γ-ray spectroscopy. In order to confirm the existence
of the expected low-lying isomeric 0+
2 state, the possibility of an electric-monopole (E0) decay to the ground state was examined. The observation of an E0 transition
at 508 keV allowed the determination of the mixing between coexisting prolate and oblate shapes.
Received: 16 November 1998 相似文献
106.
We revisit Mach—Zehnder interferometry using a suitable phase-space analysis and present a rigorous optimization of the sensitivity
in realistic condition, i.e., for Gaussian input states, and taking into account nonunit quantum efficiency in the detection
stage. The working regime of the interferometer is optimized at fixed input energy versus the squeezing phases and amplitudes
as well as the distribution of squeezing in the two input signals. For ideal detection we find the known result that the squeezing
resource allows to beat the shot-noise limit. For nonunit detection efficiency, we show that for fixed input energy one can
always optimize the squeezing fraction in order to enhance the sensitivity with respect to the case of no squeezing, even
in cases when one cannot go beyond the shot-noise limit.
The text was submitted by the authors in English. 相似文献
107.
108.
The synthesis of the γ-trimethylsilyldibutylallylstannane grafted on an insoluble macroporous polymer is reported. This bimetallic reagent was treated with aldehydes in the presence of indium trichloride to afford in good yields both symmetrical and unsymmetrical cis-2,6-disubstituted dihydropyrans, practically uncontaminated with organotin residues (less than 20 ppm). The potential for regeneration and reuse of this supported bimetallic reagent is pointed out. 相似文献
109.
A. R.?RossiEmail author M. G.A.?Paris 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,32(2):223-226
A method based on Maximum-Entropy (ME) principle to
infer photon distribution from on/off measurements
performed with few and low values of quantum
efficiency is addressed. The method consists of two steps: at
first some moments of the photon distribution are retrieved from
on/off statistics using Maximum-Likelihood estimation, then
ME principle is applied to infer the quantum state and, in turn,
the photon distribution. Results from simulated experiments on
coherent and number states are presented. 相似文献
110.
Single carbon fibers are deformed in bending by forming loops with varying radius. Position-resolved x-ray diffraction patterns from the bent fibers are collected from the tension to the compression region with a synchrotron radiation nanobeam of 100 nm size from a waveguide structure. A strain redistribution with a shift of the neutral axis is observed. A significant increase of the misorientation of the graphene sheets in the compression region shows that intense buckling of the nanosized carbon crystallites is the physical origin of different tensile and compressive properties. 相似文献