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911.
Zheng X Aniol K Armstrong DS Averett TD Bertozzi W Binet S Burtin E Busato E Butuceanu C Calarco J Camsonne A Cates GD Chai Z Chen JP Choi S Chudakov E Cusanno F Leo RD Deur A Dieterich S Dutta D Finn JM Frullani S Gao H Gao J Garibaldi F Gilad S Gilman R Gomez J Hansen JO Higinbotham DW Hinton W Horn T De Jager CW Jiang X Kaufman L Kelly J Korsch W Kramer K LeRose J Lhuillier D Liyanage N Margaziotis DJ Marie F Markowitz P McCormick K Meziani ZE Michaels R Moffit B Nanda S Neyret D Phillips SK 《Physical review letters》2004,92(1):012004
We have measured the neutron spin asymmetry A(n)(1) with high precision at three kinematics in the deep inelastic region at x=0.33, 0.47, and 0.60, and Q(2)=2.7, 3.5, and 4.8 (GeV/c)(2), respectively. Our results unambiguously show, for the first time, that A(n)(1) crosses zero around x=0.47 and becomes significantly positive at x=0.60. Combined with the world proton data, polarized quark distributions were extracted. Our results, in general, agree with relativistic constituent quark models and with perturbative quantum chromodynamics (PQCD) analyses based on the earlier data. However they deviate from PQCD predictions based on hadron helicity conservation. 相似文献
912.
Schaldach CM Bourcier WL Paul PH Wilson WD 《Langmuir : the ACS journal of surfaces and colloids》2004,20(24):10744-10750
We have developed a method of calculation of the dielectrophoretic force on a nanoparticle in a fluid environment where variations in the electric field and electric field gradients are on the same nanoscale as the particle. The Boundary Element Dielectrophoretic Force (BEDF) method involves constructing a solvent-accessible or molecular surface surrounding the particle, calculating the normal component of the electric field at the surface boundary elements, and then solving a system of linear equations for the induced surface polarization charge on each element. Different surface elements of the molecule may experience quite different polarizing electric fields, unlike the situation in the point dipole approximation. A single 100-A-radius ring test configuration is employed to facilitate comparison with the well-known point dipole approximation (PDA). We find remarkable agreement between the forces calculated by the BEDF and PDA methods for a 1 A polarizable sphere. However, for larger particles, the differences between the methods become qualitative as well as quantitative; the character of the force changes from attractive at the origin of the ring for a 50-A sphere, to repulsive for a 75-A sphere. Equally dramatic differences are found in a more complex electrical environment involving two sets of 10 rings. 相似文献
913.
Katritzky AR Hayden AE Kirichenko K Pelphrey P Ji Y 《The Journal of organic chemistry》2004,69(15):5108-5111
Reactions of secondary amides 2a-i with 1-chloro-1H-benzotriazole and triphenylphosphine give imidoylbenzotriazoles 3a-i. The treatment of 3a,b,e,g with silyl enol ethers 5a,b in the presence of potassium tert-butoxide provides a new general approach to enaminoketones 6a-h. 相似文献
914.
Rendle PM Seger A Rodrigues J Oldham NJ Bott RR Jones JB Cowan MM Davis BG 《Journal of the American Chemical Society》2004,126(15):4750-4751
The continuing ability of bacteria to resist current antibiotic treatments highlights the need for alternative strategies for inhibiting their pathogenicity. Bacterial attachment is a major factor in infectivity and virulence. This key binding phase of bacteria to any potential host is mediated by adhesin proteins and so these present an attractive therapeutic target for antiinfective blocking strategies. However, the natural ligands to adhesins are large, typically complex molecules that are difficult to mimic with small molecules. We describe here a method that creates precise synthetic mimics of glycoproteins that are designed to bind adhesins. By using protein-degrading enzymes as the basis for these mimics we have created large-molecule protein ligands that inhibit aggregation of pathogenic bacteria at levels greater than a million-fold higher than small-molecule inhibitors of adhesins. 相似文献
915.
Reaction of 2,6-diphenylphenol (HOC(6)H(3)Ph(2)-2,6) with (n)BuLi, NaH, KH, or Rb or Cs metal in benzene gives the solvent-free complexes [M(OAr)]x in excellent yield. The complex [Rb(OC(6)H(3)Ph(2)-2,6)](x)() exhibits a ladderlike structure in the solid state with triply bridging oxygen atoms and Rb-O distances of 2.743(3), 2.930(2), and 2.973(2) A. The Rb cations interact with the pi-electron cloud of the arene moieties, giving rise to a high Rb coordination number. The cesium-containing congener forms a layered, columnlike structure consisting of [Cs(2)(mu(2)-OAr)(2)] units, with nearly identical Cs-O distances of 2.945(2) and 2.947(2) A. The individual layers are held together solely by Cs-arene pi-interactions. 相似文献
916.
Turner LE Thorn MG Fanwick PE Rothwell IP 《Chemical communications (Cambridge, England)》2003,(9):1034-1035
The 2-(inden-3-yl)phenoxide ligand can be resolved at both tetrahedral and octahedral Group 4 metal centers using chiral binaphthoxide ligands. 相似文献
917.
Titanium centers supported by aryloxide ligation mediate the tricyclization of a dienyne via intramolecular insertion of an olefin into the titanium-vinyl bond of a titanacyclopent-2-ene. 相似文献
918.
Regiodependent luminescence quenching of biotinylated N-sulfonyl-acridinium-9-carboxamides by avidin
[reaction: see text] Biotin was conjugated to chemiluminescent N-sulfonylacridinium-9-carboxamides at the N-10 or 9-position carboxamide. Upon binding to avidin, the light output of the N-10 derivative (8) was quenched up to 92% upon triggering with basic peroxide, while the 9-position carboxamide conjugate (9) was quenched only 33%. The utility of this effect was demonstrated in a model homogeneous chemiluminescence assay. 相似文献
919.
Phillip Greenberg 《Studies in Applied Mathematics》1972,51(4):415-416
920.