全文获取类型
收费全文 | 2821篇 |
免费 | 60篇 |
国内免费 | 54篇 |
专业分类
化学 | 1968篇 |
晶体学 | 21篇 |
力学 | 56篇 |
数学 | 508篇 |
物理学 | 382篇 |
出版年
2021年 | 22篇 |
2017年 | 17篇 |
2016年 | 50篇 |
2015年 | 29篇 |
2014年 | 59篇 |
2013年 | 116篇 |
2012年 | 97篇 |
2011年 | 135篇 |
2010年 | 58篇 |
2009年 | 46篇 |
2008年 | 108篇 |
2007年 | 119篇 |
2006年 | 80篇 |
2005年 | 104篇 |
2004年 | 87篇 |
2003年 | 67篇 |
2002年 | 56篇 |
2001年 | 20篇 |
2000年 | 24篇 |
1999年 | 22篇 |
1998年 | 25篇 |
1997年 | 31篇 |
1996年 | 32篇 |
1995年 | 30篇 |
1994年 | 28篇 |
1992年 | 28篇 |
1991年 | 35篇 |
1990年 | 25篇 |
1989年 | 21篇 |
1988年 | 40篇 |
1987年 | 51篇 |
1986年 | 38篇 |
1985年 | 48篇 |
1984年 | 52篇 |
1983年 | 36篇 |
1982年 | 40篇 |
1981年 | 44篇 |
1980年 | 37篇 |
1979年 | 40篇 |
1978年 | 70篇 |
1977年 | 50篇 |
1976年 | 53篇 |
1975年 | 25篇 |
1974年 | 41篇 |
1973年 | 38篇 |
1972年 | 22篇 |
1971年 | 17篇 |
1970年 | 18篇 |
1885年 | 23篇 |
1884年 | 26篇 |
排序方式: 共有2935条查询结果,搜索用时 0 毫秒
11.
12.
In the paper we prove two inequalities involving Gelfand numbers of operators with values in a Hilbert space. The first inequality is a Rademacher version of the main result in [Pa-To-1] which relates the Gelfand numbers of an operator from a Banach spaceX intol
2
n
with a certain Rademacher average for the dual operator. The second inequality states that the Gelfand numbers of an operatoru froml
1
N
into a Hilbert space satisfy the inequality
相似文献
13.
Carl C. Cowen 《Integral Equations and Operator Theory》1988,11(2):151-160
If ? is an analytic function mapping the unit diskD into itself, the composition operatorC ? is the operator onH 2 given byC ?f=fo?. The structure of the composition operatorC ? is usually complex, even if the function ? is fairly simple. In this paper, we consider composition operators whose symbol ? is a linear fractional transformation mapping the disk into itself. That is, we will assume throughout that $$\varphi \left( z \right) = \frac{{az + b}}{{cz + d}}$$ for some complex numbersa, b, c, d such that ? maps the unit diskD into itself. For this restricted class of examples, we address some of the basic questions of interest to operator theorists, including the computation of the adjoint. 相似文献
14.
15.
L. Käubler W. Enghardt H. Prade P. Carlé L. O. Norlin K. -G. Rensfelt U. Rosengård 《Zeitschrift für Physik A Hadrons and Nuclei》1988,329(2):143-150
Using the reaction138Ba(α,2n)140Ce the magnetic moment of the 10 1 + isomer atE x =3714.7 keV in theN=82 nucleus140Ce has been determined by means of the TDPAD method toμ=+10.3(4)μ N . Measuredg-factors in140Ce are compared to calculations within the shell model with configuration mixing. For the 10 1 + isomer in140Ce the four proton configuration π(1g 7 2/2 ,2d 5 2/2 ) has been found to be dominant. From theg-factor measurement strong contributions of multiparticle excitations to thegp2d 3/2,π3s 1 2 or π1h 11 2 shells and admixtures of neutron excitations to the wave function of the 10 1 + state could be excluded. The strongE1γ-branch of the deexcitation of the 10 1 + isomer in140Ce can be explained by means of small admixtures of configurations which contain the outer subshell excitationsπ2f 7/2 andπ1h 9/2. On this basisE1 transitions experimentally observed in theN=82 nuclei140Ce,141Pr and145Eu may be understood. 相似文献
16.
Nanoscale organization of the pathogen receptor DC-SIGN mapped by single-molecule high-resolution fluorescence microscopy. 总被引:3,自引:0,他引:3
Bärbel I. de Bakker Dr. Frank de Lange Dr. Alessandra Cambi Dr. Jeroen P. Korterik Erik M. H. P. van Dijk Dr. Niek F. van Hulst Prof. Carl G. Figdor Prof. Maria F. Garcia‐Parajo Prof. 《Chemphyschem》2007,8(10):1473-1480
DC-SIGN, a C-type lectin exclusively expressed on dendritic cells (DCs), plays an important role in pathogen recognition by binding with high affinity to a large variety of microorganisms. Recent experimental evidence points to a direct relation between the function of DC-SIGN as a viral receptor and its spatial arrangement on the plasma membrane. We have investigated the nanoscale organization of fluorescently labeled DC-SIGN on intact isolated DCs by means of near-field scanning optical microscopy (NSOM) combined with single-molecule detection. Fluorescence spots of different intensity and size have been directly visualized by optical means with a spatial resolution of less than 100 nm. Intensity- and size-distribution histograms of the DC-SIGN fluorescent spots confirm that approximately 80 % of the receptors are organized in nanosized domains randomly distributed on the cell membrane. Intensity-size correlation analysis revealed remarkable heterogeneity in the molecular packing density of the domains. Furthermore, we have mapped the intermolecular organization within a dense cluster by means of sequential NSOM imaging combined with discrete single-molecule photobleaching. In this way we have determined the spatial coordinates of 13 different individual dyes, with a localization accuracy of 6 nm. Our experimental observations are all consistent with an arrangement of DC-SIGN designed to maximize its chances of binding to a wide range of microorganisms. Our data also illustrate the potential of NSOM as an ultrasensitive, high-resolution technique to probe nanometer-scale organization of molecules on the cell membrane. 相似文献
17.
18.
Iodine monofluorosulfate has been found to react with fluoroolefins in the absence of a solvent to give the corresponding iodo alkyl fluorosulfates by addition of ?l and ?OSO2F across the double bond. The observed products were ICF2CF2SO3F, CF3CFlCF2SO3F, and the isomer mixture ICF2CFClSO3F and ICFClCF2SO3F. Perfluorocyclobutene was unreactive. The iodine fluorosulfate used for this study was synthesized from the reactions of either I2 or RfI with ClSO3F, with both reactions being new routes to this compound. These iodo fluorocarbon fluorosulfates are novel compounds and were characterized by spectroscopy and by formation of the derivatives CF3CFICFO and ICF2CFO. 相似文献
19.
20.
By density functional methods we characterize the bonding and charge distribution in complexes of benzene with dearomatizing agents tpReCO(L), tpMoNO(L), and tpWNO(L), where tp = hydrido Tris (pyrazolyl)borate), for a range of ligands L. Our LSDA and B3LYP density functional calculations use the Spartan LACVP+ basis and pseudopotential on Re, Mo, and W and 6-31G* on light atoms. The binding energy is strongly dependent on the nature of the ligand L, being greatest for L = ammonia and N-methylimidazole and weakest for CH3NC and CO. We find a correlation between strength of binding and electron transfer from the dearomatizing agents toward benzene. For the most strongly bound systems we find substantial (up to 500 millielectrons) charge transfer towards benzene, while for the most weakly bound systems charge is withdrawn from benzene. Structural details illustrate the ability of Re, Mo, and W species to dearomatize complexed benzene, which is extensive for all but the most weakly bound species with L = MeNC and CO. Re and W dearomatizing agents, which are computed and observed to form stable complexes with benzene, may be economic alternatives to osmium dearomatizing agents. 相似文献
|