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排序方式: 共有236条查询结果,搜索用时 31 毫秒
51.
Froula DH Igumenshchev IV Michel DT Edgell DH Follett R Glebov VY Goncharov VN Kwiatkowski J Marshall FJ Radha PB Seka W Sorce C Stagnitto S Stoeckl C Sangster TC 《Physical review letters》2012,108(12):125003
A series of experiments to determine the optimum laser-beam radius by balancing the reduction of cross-beam energy transfer (CBET) with increased illumination nonuniformities shows that the hydrodynamic efficiency is increased by ~35%, which leads to a factor of 2.6 increase in the neutron yield when the laser-spot size is reduced by 20%. Over this range, the absorption is measured to increase by 15%, resulting in a 17% increase in the implosion velocity and a 10% earlier bang time. When reducing the ratio of laser-spot size to a target radius below 0.8, the rms amplitudes of the nonuniformities imposed by the smaller laser spots are measured at a convergence ratio of 2.5 to exceed 8 μm and the neutron yield saturates despite increasing absorbed energy, implosion velocity, and decreasing bang time. The results agree well with hydrodynamic simulations that include both nonlocal and CBET models. 相似文献
52.
Luo J Wang H Zhong F Kwiatkowski J Xu LW Lu Y 《Chemical communications (Cambridge, England)》2012,48(39):4707-4709
The first Mannich reaction employing phthalides using a quinidine-based multifunctional catalyst has been developed. The reported method led to the synthesis of 3,3-disubstituted phthalide derivatives in excellent yields, with good diastereo- and enantioselectivities. Convenient synthesis of chiral isoquinolinones and isoquinolines has also been demonstrated. 相似文献
53.
Two quantum-mechanical models are proposed to described a shift of tautomeric equilibrium as a result of electronic excitation and change of environment. According to the first n PD MEP model which is used to estimate the relative solvation effect on the stability of tautomers in an excited state, the calculation of the interaction energy between a solvent (simulated by a set of n point dipoles, n PD) and an excited solute molecule is based on the molecular electrostatic potential (MEP) of the corresponding excited state. In the second n PDQ model, a solvent represented by a set of n point dipoles and quadrupoles (n PDQ) modifies the solute's hamiltonian via an electrostatic interaction contribution. Comparing the results of the calculation for isolated and solvated tautomers, the n PDQ model is used to estimate the influence of electronic excitation on the change of relative stability of tautomers existing in a solution. An application of both models to 2- and 4-oxopyridine predicts a shift of the tautomeric equilibria in their excited states in accordance with experimental evidence. 相似文献
54.
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57.
A. J. Barcz J. M. Baranowski S. Kwiatkowski 《Applied Physics A: Materials Science & Processing》1995,61(3):321-324
The effects of interaction between a thick In layer and heat-treated GaAs at 570°C are studied with Scanning Electron Microscopy (SEM), Secondary Ion Mass Spectrometry (SIMS), Rutherford Backscattering Spectrometry (RBS), X-Ray Diffraction (XRD) and Nomarski microscopy. It is shown that, besides the well-known InGaAs crystallites which epitaxially grow upon dissolution of the substrate, an array of In-rich dendrites is observed whose density correlates with the density of the crystal dislocations. The driving force for In to protrude along the dislocations to eventually form In(Ga)As spikes is apparently excess arsenic reported to be present in the vicinity of the individual dislocations. It is postulated that the existing data concerning the coefficient of classical diffusion of In in GaAs may be overestimated by a factor of 106. 相似文献
58.
A very simple electrostatic model of solvation in which the solvent molecules are represented by point dipoles has been applied to simulate the hydration effect on molecular systems within the CNDO/2 method. The limitations of the model compared to the previous approaches as well as its feasible application to the study of tautomeric equilibria of cytosine and adenine in aqueous solution are discussed. 相似文献
59.
Fernández P Durand JS Pérez-Conde C Paniagua G 《Analytical and bioanalytical chemistry》2003,375(8):1020-1023
This paper reports a new flow-through fluoroimmunosensor, the function of which is based on antibodies immobilized on an inmunoreactor of controlled-pore glass (CPG), for determination of digoxin, used in the treatment of congestive heart failure and artery disease. The immunosensor has a detection limit of 1.20 microg L(-1) and provides high reproducibility (RSD=4.5% for a concentration of 0.0025 mg L(-1), and RSD=6.7% for 0.01 mg L(-1)). The optimum working concentration range was found to be 1.2 x 10(-3)-4.0 x 10(-2) mg L(-1). The lifetime of the immunosensor was about 50 immunoassays; if stored unused its lifetime can be extended to three months. A sample speed of about 10-12 samples per hour can be attained. Possible interference from substances with structures similar to digoxin (morphine, heroin, tebaine, codeine, pentazocine and narcotine) was investigated. No cross-reactivity was seen at the highest digoxin: interferent ratio studied (1:100). The proposed fluoroimmunosensor was successfully used to determine digoxin concentrations in human serum samples. 相似文献
60.
Edmund Kwiatkowski Marek Kwiatkowski Aleksandra Olechnowicz Giuliano Bandoli 《Journal of chemical crystallography》1993,23(6):473-480
The Schiffbases 1,9-bis(2-pyrrolyl)-2,5,8-triazanona-1,8-diene (H2L1), 1,10-bis(2-pyrrolyl)-2,5,9-triazaundeca-l,9-diene (H2L2), and 1,11-bis(2-pyrrolyl)-6-methyl-2,6,10-triazaundeca-l,10-diene (H2L4) react with copper(II) nitrate or nickel(II) perchlorate in the presence of triethylamine to give new complexes [Cu(HL1,2,4)]NO3 and [Ni(HL1,2,4)]ClO4. The crystal structures of [Cu(HL2)]NO3 and [Ni(HL2)]CIO4 have been determined from single crystal diffractometer data and refined to finalR factors of 5.09 and 5.3%, respectively. Crystallographic data: [Cu(HL2)]NO3: monoclinic,P21/c,a=10.036(2),b=14.500(2),c=13.317(2) Å,=108.14(1)°,Z=4, andd
c
=11.427 Mg m–3; [Ni(HL2)]ClO4: monoclinic,P21/n,a=10.578(3),b=13.953(3),c=12.394(4) Å,=93.78(2)°,Z=4, andd
c
=1.549 Mg m–3. In both the structures the potentially pentadentate ligand (HL2)– acts as a tetradentate one leaving one pyrrole group uncoordinated. Interesting is the metal dependent sequence of the three chelate rings. While the Ni (II) ion coordinates the (HL2)– ligand to form a 5-5-6-membered ring system, the ring arrangement in the copper complex is of the 5-6-5 type. 相似文献