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961.
A. F. Schmidt A. A. Kurokhtina A. N. Svechkarev V. V. Smirnov A. Al-Halaiqa 《Kinetics and Catalysis》2010,51(1):113-118
The results of comparative kinetic experiments, homogeneity/heterogeneity testing data, and the relative substrate reactivity
data for the Suzuki and Heck reactions are consistent with the participation of heterogeneous forms of the catalyst (colloidal
palladium and larger palladium aggregates) in the Suzuki reaction. This is the reason why the Suzuki reaction occurs more
readily than the Heck reaction. The data obtained in this study indicate that these reactions differ in the nature of catalyst
deactivation processes. 相似文献
962.
Despite considerable improvements in the tolerance and efficacy of novel chemotherapeutic agents, the mortality of hematological malignancies is still high due to therapy relapse, which is associated with bad prognosis. Dietary polyphenolic compounds are of growing interest as an alternative approach, especially in cancer treatment, as they have been proven to be safe and display strong antioxidant properties. Here, we provide evidence that both resveratrol and curcumin possess huge potential for application as both chemopreventive agents and anticancer drugs and might represent promising candidates for future treatment of leukemia. Both polyphenols are currently being tested in clinical trials. We describe the underlying mechanisms, but also focus on possible limitations and how they might be overcome in future clinical use--either by chemically synthesized derivatives or special formulations that improve bioavailability and pharmacokinetics. 相似文献
963.
964.
965.
Tim De Meyer Davy Sinnaeve Bjorn Van Gasse Ernst-R Rietzschel Marc L. De Buyzere Michel R. Langlois Sofie Bekaert José C. Martins Wim Van Criekinge 《Analytical and bioanalytical chemistry》2010,398(4):1781-1790
Proton nuclear magnetic resonance (1H-NMR)-based metabolomics enables the high-resolution and high-throughput assessment of a broad spectrum of metabolites in
biofluids. Despite the straightforward character of the experimental methodology, the analysis of spectral profiles is rather
complex, particularly due to the requirement of numerous data preprocessing steps. Here, we evaluate how several of the most
common preprocessing procedures affect the subsequent univariate analyses of blood serum spectra, with a particular focus
on how the standard methods perform compared to more advanced examples. Carr–Purcell–Meiboom–Gill 1D 1H spectra were obtained for 240 serum samples from healthy subjects of the Asklepios study. We studied the impact of different
preprocessing steps—integral (standard method) and probabilistic quotient normalization; no, equidistant (standard), and adaptive-intelligent
binning; mean (standard) and maximum bin intensity data summation—on the resonance intensities of three different types of
metabolites: triglycerides, glucose, and creatinine. The effects were evaluated by correlating the differently preprocessed
NMR data with the independently measured metabolite concentrations. The analyses revealed that the standard methods performed
inferiorly and that a combination of probabilistic quotient normalization after adaptive-intelligent binning and maximum intensity
variable definition yielded the best overall results (triglycerides, R = 0.98; glucose, R = 0.76; creatinine, R = 0.70). Therefore, at least in the case of serum metabolomics, these or equivalent methods should be preferred above the
standard preprocessing methods, particularly for univariate analyses. Additional optimization of the normalization procedure
might further improve the analyses. 相似文献
966.
Su‐Kyung Lee Kyong‐Soon Shin Dr. Dong‐Youn Noh Prof. Dr. Olivier Jeannin Dr. Frédéric Barrière Dr. Jean‐François Bergamini Dr. Marc Fourmigué Dr. 《化学:亚洲杂志》2010,5(1):169-176
The redox‐active and chelating diphosphine, 3,4‐dimethyl‐3′,4′‐bis(diphenylphosphino)‐tetrathiafulvalene, denoted as P2 , is engaged in a series of platinum complexes, [(P2)Pt(dithiolene)], with different dithiolate ligands, such as 1,2‐benzenedithiolate (bdt), 1,3‐dithiole‐2‐thione‐4,5‐dithiolate (dmit), and 5,6‐dihydro‐1,4‐dithiin‐2,3‐dithiolate (dddt). The complexes are structurally characterized by X‐ray diffraction, together with a model compound derived from bis(diphenylphosphino)ethane, namely, [(dppe)Pt(dddt)] . Four successive reversible electron‐transfer processes are found for the [(P2)Pt(dddt)] complex, associated with the two covalently linked but electronically uncoupled electrophores, that is, the TTF core and the platinum dithiolene moiety. The assignments of the different redox processes to either one or the other electrophore is made thanks to the electrochemical properties of the model compound [(dppe)Pt(dddt)] lacking the TTF redox core, and with the help of theoretical calculations (DFT) to understand the nature and energy of the frontier orbitals of the [(P2)Pt(dithiolene)] complexes in their different oxidation states. The first oxidation of the highly electron‐rich [(P2)Pt(dddt)] complex can be unambiguously assigned to the redox process affecting the Pt(dddt) moiety rather than the TTF core, a rare example in the coordination chemistry of tetrathiafulvalenes acting as ligands. 相似文献
967.
Nfor BK Noverraz M Chilamkurthi S Verhaert PD van der Wielen LA Ottens M 《Journal of chromatography. A》2010,1217(44):6829-6850
The thermodynamic modeling of protein adsorption on mixed-mode adsorbents functionalized with ligands carrying both hydrophobic and electrostatic groups was undertaken. The developed mixed mode isotherm was fitted with protein adsorption data obtained for five different proteins on four different mixed mode adsorbents by 96-well microtitre plate high throughput batch experiments on a robotic workstation. The developed mixed mode isotherm was capable of describing the adsorption isotherms of all five proteins (having widely different molecular masses and iso-electric points) on the four mixed mode adsorbents and over a wide range of salt concentrations and solution pH, and provided a unique set of physically meaningful parameters for each resin-protein-pH combination. The model could capture the typically observed minimum in mixed mode protein adsorption and predict the precise salt concentration at which this minimum occurs. The possibility of predicting the salt concentration at which minimum protein binding occurs presents new opportunities for designing better elution strategies in mixed mode protein chromatography. Salt-protein interactions were shown to have important consequences on mixed mode protein adsorption when they occur. Finally, the mixed mode isotherm also gave very good fit with literature data of BSA adsorption on a different mixed mode adsorbent not examined in this study. Hence, the mixed mode isotherm formalism presented in this study can be used with any mixed mode adsorbent having the hydrophobic and electrostatic functional groups. It also provides the basis for detailed modeling and optimization of mixed mode chromatographic separation of proteins. 相似文献
968.
969.
Marc Ostermeier Dipl.‐Chem. Marie‐Anne Berlin Dipl.‐Chem. Robert M. Meudtner Dr. Serhiy Demeshko Dr. Franc Meyer Prof. Dr. Christian Limberg Prof. Dr. Stefan Hecht Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10202-10213
2,6‐Bis(1,2,3‐triazol‐4‐yl)pyridine (btp) ligands with substitution patterns ranging from strongly electron‐donating to strongly electron‐accepting groups, readily prepared by means of Cu‐catalyzed 1,3‐dipolar cycloaddition (the “click” reaction), were investigated with regard to their complexation behavior, and the properties of the resulting transition‐metal compounds were compared. Metal–btp complexes of 1:1 stoichiometry, that is, [Ru(btp)Cl2(dmso)] and [Zn(btp)Br2], could be isolated and were crystallographically characterized: they display octahedral and trigonal‐bipyramidal coordination geometries, respectively, and exhibit high aggregation tendencies due to efficient π–π stacking leading to low solubilities. Metal–btp complexes of 1:2 stoichiometry, that is, [Fe(btp)2]2+ and [Ru(btp)2]2+, could also be synthesized and their metal centers show the expected octahedral coordination spheres. The iron compounds exhibit quite a complex magnetic behavior in the solid state including spin crossover near room temperature, and hysteresis and locking into high‐spin states on tempering at 400 K, depending on the substituents on the btp ligands. Cyclic voltammetry studies of [Ru(btp)2]2+ reveal strong modulation of the oxidation potentials by more than 0.6 V and a clear linear correlation to the Hammett constant (σpara) of the substituent at the pyridine core. Isothermal titration calorimetry was used to measure the thermodynamics of the FeII–btp complexation process and enabled accurate determination of the complexation enthalpies, which display a linear relationship with the σpara values for the terminal phenyl substituents. Detailed NMR spectroscopic studies finally revealed that in the case of FeII complexation, dynamics are rapid for all investigated btp derivatives in acetonitrile, while replacing FeII by RuII or changing the solvent to dichloromethane effectively slows down ligand exchange. The results nicely demonstrate the utility of substituent parameters, originally developed for linear free‐energy relationships to explain reactivity in organic reactions, in coordination chemistry, and to illustrate the potential to custom‐design btp ligands and complexes thereof with predictable properties. The fast equilibration of the [Fe(btp)2]2+ complexes together with their tunable stability and interesting magnetic properties should enable the design of dynamic metallosupramolecular materials with advantageous properties. 相似文献
970.
The aim of this paper is to describe a method for identifying micro material parameters using only macroscopic experimental data. The FE2 method is used to model the behavior of the complex materials with heterogeneous micro-structure. The resulting least squares problem is minimized using gradient-based optimization algorithms, where the gradient information is derived analytically within the discretized scheme. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献