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971.
The scope and limitation of the asymmetric nucleophilic aromatic substitution reaction of alpha-substituted 1,3-dicarbonyl compounds and activated aromatic systems catalyzed by N-benzyl-O-benzoylcinchoninium or cinchonidinium salts are presented. Several novel O-benzoylcinchona alkaloid derived salts have been prepared and evaluated as catalysts in this reaction, which can proceed with enantioselectivites up to 96% ee. Various 1,3-dicarbonyl compounds and activated aromatic systems are evaluated for the aromatic nucleophilic substitution reaction, and it has been found that the yield and enantioselectivity are very dependent on the substrate and reagent. The scope of the functionalization of the products to, e.g., spiro-oxoindole, a ring-opening reaction of 1,3 alpha,alpha-disubstituted dicarbonyl compounds with several nucleophiles, and the diastereoselective reduction of the keto functionality in the optically active S(N)Ar product are reported. 相似文献
972.
1,3-Dihydro[1,2,5]thiadiazolo[3,4-b]pyrazine-2,2-dioxides are obtained in a good yield from the reaction of 2,3-diamino pyrazines with sulfamide under microwave conditions. 相似文献
973.
Renzo Ruzziconi Prof. Sara Spizzichino Lodovico Lunazzi Prof. Andrea Mazzanti Dr. Manfred Schlosser Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(11):2645-2652
Someone who says “A” should be prepared to also say “B” : In contrast to cyclohexane model‐based A values, biphenyl model‐derived B values are powerful tools to quantify steric repulsion in and conformational behavior of ortho‐substituted aromatic compounds.
974.
Rodriguez-Mozaz S Lopez de Alda MJ Barceló D 《Analytical and bioanalytical chemistry》2006,386(4):1025-1041
Recent advances in the development and application of biosensors for environmental analysis and monitoring are reviewed in
this article. Several examples of biosensors developed for relevant environmental pollutants and parameters are briefly overviewed.
Special attention is paid to the application of biosensors to real environmental samples, taking into consideration aspects
such as sample pretreatment, matrix effects and validation of biosensor measurements. Current trends in biosensor development
are also considered and commented on in this work. In this context, nanotechnology, miniaturisation, multi-sensor array development
and, especially, biotechnology arise as fast-growing areas that will have a marked influence on the development of new biosensing
strategies in the near future. 相似文献
975.
Darr JP Crowther AC Loomis RA Ray SE McCoy AB 《The journal of physical chemistry. A》2007,111(51):13387-13396
The dependence of the long-range interactions between molecular hydrogen and iodine monochloride on the geometry between the molecules is investigated. Laser-induced fluorescence and action spectroscopy experiments have identified multiple conformers of the o,p-H2...I35,37Cl(X,v' '=0) van der Waals complexes. A conformer with the hydrogen molecule localized at the iodine end of the dihalogen, most likely with C2v symmetry, is significantly more stable than an asymmetric conformer with the hydrogen localized in the well oriented orthogonally to the I-Cl bond axis, D0' ' = 186.4(3) cm-1 versus 82.8(3) 相似文献
976.
Using labelled formulae, a cut-free sequent calculus for intuitionistic propositional logic is presented, together with an easy cut-admissibility proof; both extend to cover, in a uniform fashion, all intermediate logics characterised by frames satisfying conditions expressible by one or more geometric implications. Each of these logics is embedded by the G?del–McKinsey–Tarski translation into an extension of S4. Faithfulness of the embedding is proved in a simple and general way by constructive proof-theoretic methods, without appeal to semantics other than in the explanation of the rules. 相似文献
977.
Matthias Bartelmann Elena Kozlikin Robert Lilow Carsten Littek Felix Fabis Ivan Kostyuk Celia Viermann Lavinia Heisenberg Sara Konrad Daniel Geiss 《Annalen der Physik》2019,531(11)
Kinetic field theory (KFT) is a statistical field theory for an ensemble of classical point particles in or out of equilibrium. Its application to cosmological structure formation is reviewed. Beginning with the construction of a generating functional, it is described in detail how the theory needs to be adapted to an expanding spatial background and the homogeneous and isotropic, correlated initial conditions for cosmic structures. Based on the generating functional, three approaches are developed to nonlinear cosmic structures, which rest either on expanding an interaction operator, averaging the interaction term, or resumming perturbation terms. An analytic, parameter‐free equation for the nonlinear cosmic power spectrum is presented. It is explained how density profiles of bound structures and velocity power spectra can be derived from the theory. It is clarified how KFT relates to the BBGKY hierarchy. Kinetic field theory is then applied to fluids, reformulating KFT in terms of macroscopic quantities. The resulting resummation scheme is used to describe mixtures of gas and dark matter. Finally, it is discussed how KFT can be combined with modified theories of gravity. As an example for a noncosmological application, results are shown on the spatial correlation function of cold Rydberg atoms derived from KFT. 相似文献
978.
Isomerizations of azo, imine, and alkene groups using light are highly tunable. As such, photoswitches based on these functional groups have become critical components of many responsive molecules and materials. This mini‐review describes recent work focused on controlling various properties of double bond‐based molecular switches, including speed of switching, thermal stability, and wavelength required to initiate switching. Methods used to control structure and function vary, but commonly involve careful probing of the electronic, photochemical, and steric profiles of the molecular switches. Successes and avenues for further investigation will be discussed. 相似文献
979.
Sara Haghshenas Kashani Amir Landarani‐Isfahani Majid Moghadam Shahram Tangestaninejad Valiollah Mirkhani Iraj Mohammadpoor‐Baltork 《应用有机金属化学》2018,32(9)
In this paper, we present the synthesis of Au nanoparticles supported on nanosilica thiol based dendrimer, nSTDP. The catalyst was prepared by reduction of HAuCl4 with NaBH4 in the presence of nSTDP. The resulting Aunp–nSTDP materials were characterized by FT–IR and UV–vis spectroscopic methods, SEM, TEM, TGA, XPS and ICP analyses. The characterization of the catalyst showed that Au nanoparticles with the size of 2–6 nm are homogeneously distributed on the nSTDP dendrimer with a catalyst loading of about 0.19 mmol/g of catalyst. The Aunp–nSTDP catalyst was used in the oxidation of alcohols with tert–butyl hydroperoxide (TBHP) as oxidant. The influence of vital reaction parameters such as solvent, oxidant and amount of catalyst on the oxidation of alcohols was investigated. These reactions were best performed in an acetonitrile/water mixture (3:2) in the presence of 0.76 mol% of the catalyst on the basis of the Au content at 80 °C under atmospheric pressure of air to afford the desired products in high yields (80–93% for benzyl alcohols). The Aunp–nSTDP catalyst exhibited a high selectivity toward the corresponding aldehyde and ketone (up to 100%). Reusabiliy and stability tests demonstrated that the Aunp–nSTDP catalyst can be recycled with a negligible loss of its activity. Also this catalytic exhibited a good chemoselectivity in the oxidation of alcohols. 相似文献
980.
Nafise Modanlou Juibari Sara Tarighi 《Journal of Thermal Analysis and Calorimetry》2018,133(3):1317-1326
MnCo2O4 spinel nanoparticles (NPs) have been prepared using Aloe vera gel solution. The characterization of prepared spinel was performed applying Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron spectroscope, scanning electron microscope and dynamic light scattering. The results manifested that the prepared nanoparticles were mainly spherical plus minor agglomeration with average size distribution between 35 and 60 nm. The catalytic activity of the prepared nanoparticles upon thermal degradation of ammonium perchlorate (AP) was evaluated applying differential scanning calorimetry and thermogravimetry instruments. MnCo2O4 nanoparticles increased the released heat of AP from 450 to 1480 J g?1 and decreased the decomposition temperature from 420 to 293 °C. The kinetic parameters obtained from Kissinger methods showed that the activation energy of AP thermal decomposition in the presence of MnCo2O4 NPs considerably decreased. Also, a mechanism has been proposed in the presence of catalyst for the process of thermal decomposition of AP. 相似文献