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排序方式: 共有508条查询结果,搜索用时 15 毫秒
81.
Ramanatham Vinodkumar Kotarkonda Rajagopal Nayakanti Devanna 《Journal of heterocyclic chemistry》2007,44(6):1521-1523
82.
A new, efficient, and highly diastereoselective synthesis of polycyclic indole derivatives through intramolecular imino Diels-Alder reaction of aminoanthraquinone with N-prenylated indole-2-carboxaldehydes in the presence of 20 mol % of triphenylphosphonium perchlorate (TPPP) is reported with extremely high cis selectivity in good yield. 相似文献
83.
Kinetics of oxidation of 24 S‐Arylmercaptoacetic acids (SAMA) by pyridinium chlorochromate (PCC) have been studied in acidmedium. The product of oxidation is the corresponding thiophenol. The rate data of meta‐ and para‐substituted acids have been correlated well with σI, σRo values and the meta‐compounds correlate well with F,R values. The reaction constants are negative and of smaller magnitudes. Further, the ortho‐substituted acids show a good correlation with triparametric equation involving Taft's σI and σRo and charton's steric parameter v. There is no considerable steric contribution to the total orthosubstituent effect. Based on these observations, the mechanism involving the formation of protonated arylsulfinylacetic acid intermediate, followed by an intramolecular rearrangement leading to the product thiophenol has been proposed. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 683–688, 1999 相似文献
84.
In this paper we report a time-delayed chameleon-like chaotic system which can belong to different families of chaotic attractors depending on the choices of parameters. Such a characteristic of self-excited and hidden chaotic flows in a simple 3D system with time delay has not been reported earlier. Dynamic analysis of the proposed time-delayed systems are analysed in time-delay space and parameter space. A novel adaptive modified functional projective lag synchronization algorithm is derived for synchronizing identical time-delayed chameleon systems with uncertain parameters. The proposed time-delayed systems and the synchronization algorithm with controllers and parameter estimates are then implemented in FPGA using hardware–software co-simulation and the results are presented. 相似文献
85.
86.
Gurusamy Rajagopal 《Tetrahedron》2009,65(24):4735-381
Nafion SAC-13 effectively activates hexamethyldisilazane (HMDS) for the efficient and selective silylation of alcohols. Primary, secondary, and tertiary alcohols and phenols are efficiently converted to their corresponding silylethers in short reaction times (4-8 min) with excellent yield at rt under solvent-free condition. Simple and clean reactions, high yield of the products and efficient recycling of the catalyst are the salient features of this methodology. 相似文献
87.
Over a large range of the pressure, one cannot ignore the fact that the viscosity grows significantly (even exponentially)
with increasing pressure. This paper concerns long-time and large-data existence results for a generalization of the Navier-Stokes
fluid whose viscosity depends on the shear rate and the pressure. The novelty of this result stems from the fact that we allow
the viscosity to be an unbounded function of pressure as it becomes infinite. In order to include a large class of viscosities
and in order to explain the main idea in as simple a manner as possible, we restrict ourselves to a discussion of the spatially
periodic problem.
K. R. Rajagopal thanks the National Science Foundation for its support. 相似文献
88.
Rajagopal S Meyer SC Goldman A Zhou M Ghosh I 《Journal of the American Chemical Society》2006,128(44):14356-14363
New approaches for identifying small molecules that specifically target protein surfaces as opposed to active site clefts are of much current interest. Toward this goal, we describe a three-step methodology: in step one, we target a protein of interest by directed evolution of a small beta-sheet scaffold; in step two, we identify residues on the scaffold that are implicated in binding; and in step three, we transfer the chemical information from the beta-sheet to a small molecule mimic. As a case study, we targeted the proteolytic enzyme thrombin, involved in blood coagulation, utilizing a library of beta-sheet epitopes displayed on phage that were previously selected for conservation of structure. We found that the thrombin-binding, beta-sheet displaying mini-proteins retained their structure and stability while inhibiting thrombin at low micromolar inhibition constants. A conserved dityrosine recognition motif separated by 9.2 A was found to be common among the mini-protein inhibitors and was further verified by alanine scanning. A molecule containing two tyrosine residues separated by a linker that matched the spacing on the beta-sheet scaffold inhibited thrombin, whereas a similar dityrosine molecule separated by a shorter 6 A linker could not. Moreover, kinetic analysis revealed that both the mini-protein as well as its minimalist mimic with only two functional residues exhibited noncompetitive inhibition of thrombin. Thus, this reductionist approach affords a simple methodology for transferring information from structured protein scaffolds to yield small molecule leads for targeting protein surfaces with novel mechanisms of action. 相似文献
89.
Rajagopal G Maruthamuthu S Mohanan S Palaniswamy N 《Colloids and surfaces. B, Biointerfaces》2006,51(2):107-111
Photocatalytic action of the commercial TiO2 was the subject of study on the destruction of the microbes within the biofilms. The TiO2 powder was characterized by X-ray diffraction (XRD) for identifying its type and the particle size was determined. The biofilm was allowed to form over TiO2 coatings over glass slides irradiated with polychromatic light for different time durations and distances. It indicates that a five-fold decrease in bacterial count due to the formation of H2O2 at TiO2/biofilm interface. The formation of H2O2 at the TiO2/biofilm interface is estimated and it does not destroy the entire bacterial population within the biofilm. Bacterial killing effect is supported by FT-IR analysis. 相似文献
90.
Oxo(salen)chromium(V) complexes, [(salen)CrVO]+, oxidize organic sulfides selectively to sulfoxides in high yield. This oxygenation reaction is catalyzed by ligand oxides (LO's), pyridine N-oxide, 4-picoline N-oxide, 4-phenyl pyridine N-oxide and triphenylphosphine oxide. The rate is accelerated by 10-20 times with an increase in yield of sulfoxide in less reaction time. This catalytic activity is highly sensitive to the nature of the substituent in the phenyl ring of ArSMe and in the 3- and 5-position of the salen ligand. The reaction constant (ρ) value obtained with the ligand oxide catalyzed reaction is low compared to the value in the absence of LO. The strong binding and catalytic activity of ligand oxides on the oxo(salen)chromium(V) ion oxygenation is explained in terms of binding constants and a mechanism involving the electrophilic attack of [(salen)CrVO]+-LO adduct on the sulfur centre of phenyl methyl sulfide. 相似文献