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111.
Beeskow-Strauch B Schicks JM Spangenberg E Erzinger J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(16):4376-4384
The sequestration of industrially emitted CO(2) in gas hydrate reservoirs has been recently discussed as an option to reduce atmospheric greenhouse gas. This CO(2) contains, despite much effort to clean it, traces of impurities such as SO(2) and NO(2) . Here, we present results of a pilot study on CO(2) hydrates contaminated with 1% SO(2) or 1% NO(2) and show the impact on hydrate formation and stability. Microscopic observations show similar hydrate formation rates, but an increase in hydrate stability in the presence of SO(2). Laser Raman spectroscopy indicates a strong enrichment of SO(2) in the liquid and hydrate phase and its incorporation in both large and small cages of the hydrate lattice. NO(2) is not verifiable by laser Raman spectroscopy, only the presence of nitrate ions could be confirmed. Differential scanning calorimetry analyses show that hydrate stability and dissociation enthalpy of mixed CO(2)-SO(2) hydrates increase, but that only negligible changes arise in the presence of NO(2) impurities. X-ray diffraction data reveal the formation of sI hydrate in all experiments. The conversion rates of ice+gas to hydrate increase in the presence of SO(2), but decrease in the presence of NO(2). After hydrate dissociation, SO(2) and NO(2) dissolved in water and form strong acids. 相似文献
112.
Bissinger P Braunschweig H Damme A Dewhurst RD Kupfer T Radacki K Wagner K 《Journal of the American Chemical Society》2011,133(47):19044-19047
A novel NHC adduct of a dihalodiborane(4), 1, is reduced by KC(8) with formation of the five-membered boracycle 2. The reaction most likely proceeds via C-H insertion of an intermediate NHC-stabilized free bora-borylene species. 相似文献
113.
Real-time PCR (qPCR) is the principal technique for the quantification of pathogen biomass in host tissue, yet no generic
methods exist for the determination of the limit of quantification (LOQ) and the limit of detection (LOD) in qPCR. We suggest
using the Youden index in the context of the receiver operating characteristic (ROC) curve analysis for this purpose. The
LOQ was defined as the amount of target DNA that maximizes the sum of sensitivity and specificity. The LOD was defined as
the lowest amount of target DNA that was amplified with a false-negative rate below a given threshold. We applied this concept
to qPCR assays for Fusarium verticillioides and Fusarium proliferatum DNA in maize kernels. Spiked matrix and field samples characterized by melting curve analysis of PCR products were used as
the source of true positives and true negatives. On the basis of the analysis of sensitivity and specificity of the assays,
we estimated the LOQ values as 0.11 pg of DNA for spiked matrix and 0.62 pg of DNA for field samples for F. verticillioides. The LOQ values for F. proliferatum were 0.03 pg for spiked matrix and 0.24 pg for field samples. The mean LOQ values correspond to approximately eight genomes
for F. verticillioides and three genomes for F. proliferatum. We demonstrated that the ROC analysis concept, developed for qualitative diagnostics, can be used for the determination
of performance parameters of quantitative PCR. 相似文献
114.
A series of trialkylphosphine-stabilized copper(I) phenylchalcogenolate complexes [(R(3)P)(m)(CuEPh)(n)] (R = Me, Et, (i)Pr, (t)Bu; E = S, Se, Te) has been prepared and structurally characterized by X-ray diffraction. Structures were found to be mono-, di-, tri-, tetra-, hexa-, hepta-, or decanuclear, depending mainly on size and amount of phosphine ligand. Several structural details were observed, including unusually long Cu-E bonds or secondary Cu-E connections, μ(4)-bridging, and planar bridging chalcogenolate ligands. Relatively rigid Cu-E-C angles were found to be of significant influence on the flexible molecular structures, especially for bridging chalcogenolate ligands, since in these cases a correlation results between the Cu-E-Cu angles and the inclination of the E-C bonds to their Cu-E-Cu planes. We further address some of these phenomena by means of density functional computations. 相似文献
115.
We have recently shown [Proc. Natl. Acad. Sci. U.S.A. 107, 4528 (2010)] that the discreteness and stochasticity of an electron transfer event on a resistively coupled nanoelectrode causes mesoscopic fluctuations in time of the electrode potential. These fluctuations give rise to a time-average faradaic current density substantially larger than in the macroscopic limit. The deviations result to a large extent from the potentiostatic control, which imposes a constraint on the evolution of the electrode potential that leads to non-normal distributions. The degree of freedom of the electrode potential requires a resistance between nanoelectrode and metallic support. In this article, we study the dependence of the mesoscopic stochastic dynamics on this resistance (assumed to be ohmic). We show that the enhancement of the reaction rate vanishes in both limits, zero and infinite resistance. The distribution of the electrode potential continuously transforms from a normal distribution at infinite resistance (the galvanostatic limit), through a more and more peaked distribution with increasingly important rare events to the deterministic behavior at zero resistance. 相似文献
116.
Holger Braunschweig Manuela Gross Katharina Kraft 《Journal of organometallic chemistry》2011,696(2):568-571
The paramagnetic ansa-niobocene [(Me2Si)2(η5-C5H4)2NbCl2] (1) was obtained from the reaction of Li2[(Me2Si)2(C5H4)2] with [NbCl4(thf)2]. Further treatment with Li[AlH4] yielded [(Me2Si)2(η5-C5H4)2NbH3] (3), which is prone to decomposition within a few days at room temperature both in solution and in the solid-state, thus affording primarily an insoluble black material. However, after heating or irradiation of a solution of 3 small quantities of the dimeric niobium hydride species, [(Me2Si)2{μ-(η1:η5-C5H3)}(η5-C5H4)NbH]2 (4), were isolated and characterized by X-ray diffraction. 相似文献
117.
Davenport JR Musa OM Paterson MJ Piepenbrock MO Fucke K Steed JW 《Chemical communications (Cambridge, England)》2011,47(35):9891-9893
A dimeric model compound gives structural insight into the mode of interaction of low dosage hydrate inhibitors with water. 相似文献
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