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911.
Schneider S Gerken M Haiges R Schroer T Boatz JA Dixon DA Grant DJ Christe KO 《Inorganic chemistry》2007,46(1):93-102
Only two silyldichloramines, (C6H5)3SiNCl2 and (CH3)3SiNCl2, have been reported in the literature. The synthesis of the former was successfully repeated, and its structure was established by single-crystal X-ray diffraction and vibrational spectroscopy. Attempts to prepare (CH3)3SiNCl2 were unsuccessful; however, a new trialkylsilyldichloramine, t-BuMe2Si-NCl2, was prepared and characterized by Raman and multinuclear NMR spectroscopy. The reaction of t-BuMe2SiNCl2 with (CH3)4NF in CHF3 solution at -78 degrees C, followed by removal of all volatile products at -30 degrees C, produced the expected t-BuMe2SiF byproduct and a white solid consisting of NCl3 absorbed on Me4NCl. The NCl3 could be reversibly desorbed from the substrate and was identified as a neat liquid at room temperature by Raman spectroscopy. The observed final reaction products are consistent with the formation of an unstable N(CH3)4+NCl2- intermediate which decomposes to N(CH3)4+Cl- and NCl molecules which can dimerize to N2Cl2. Theoretical calculations confirm that NCl2- can readily lose Cl- and that N2Cl2 also possesses a low barrier toward loss of N2 to give chlorine atoms and, thus, can account for the formation of NCl3. 相似文献
912.
Shengli Guo Ralf Hauptmann Serena Losi Piero Zanello Jörg J. Schneider 《Journal of Cluster Science》2007,18(1):237-251
The reaction of [{(η5-Me5C5)Co}2(μ-η6:η6-toluene)] with water under different conditions leads to formation of the clusters [{(η5-Me5C5)Co}3(μ3-O)2] (1), [{(η5-Me5C5)Co}4(μ3-OH)4] (2) and [{(η5-Me5C5)Co}3(μ3-OH)4]2Co (3), whereas its reaction with hydrogen sulfide leads to [{(η5-Me5C5)Co}3(μ3-S)4]Co(μ3-S)2[(η5-Me5C5)Co]2 · Et2O (4). 1, 2 and 4 were characterized by single crystal X-ray diffraction. 1 is composed of a central Co3O2 unit, with two O2- units in an apical postion. The three cobalt atoms form a regular triangle with Co–Co distances of 2.438(2) Å, and the two oxygen atoms are located in apical positions of the triangular arrangement. The pentamethylcyclopentadienyl (Cp*) ligands are terminally bonded to the Co atoms in a η5-fashion. The Co and O atoms of 2 form a cubane-type Co4O4 cluster, with η5-bonded Cp* ligands. The central unit of 3 consists of a Co7O8 double cubane framework. Two Co4O4 cluster sharing a common corner (Co atom). Each of the other six Co atoms of the double cubane bound terminally a Cp* ligand. 4 is composed of a [{(η5-Me5C5)Co }2(μ3-S)4](μ3-S)2[(η5-Me5C5)Co]2 and an ether molecule. 4 contains a central Co4S4 cubane-like unit. One of the four Co atoms is bonded via two μ3-S atoms to two additional (η5-Cp*Co) units. The other three Co atoms are η5-coordinated to a Cp* ligand. 相似文献
913.
Ralf Schuster Tobias Wähler Dr. Miroslav Kettner Dr. Friederike Agel Dr. Tanja Bauer Prof. Peter Wasserscheid Prof. Jörg Libuda 《ChemistryOpen》2021,10(2):141-152
Low-temperature synthesis in ionic liquids (ILs) offers an efficient route for the preparation of metal oxide nanomaterials with tailor-made properties in a water-free environment. In this work, we investigated the role of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [C4C1Pyr][NTf2] in the synthesis of cobalt oxide nanoparticles from the molecular precursor Co2(CO)8 with ozone. We performed a model study in ultra-clean, ultrahigh vacuum (UHV) conditions by infrared reflection absorption spectroscopy (IRAS) using Au(111) as a substrate. Exposure of the pure precursor to ozone at low temperatures results in the oxidation of the first layers, leading to the formation of a disordered CoxOy passivation layer. Similar protection to ozone is also achieved by deposition of an IL layer onto a precursor film prior to ozone exposure. With increasing temperature, the IL gets permeable for ozone and a cobalt oxide film forms at the IL/precursor interface. We show that the interaction with the IL mediates the oxidation and leads to a more densely packed CoxOy film compared to a direct oxidation of the precursor. 相似文献
914.
Dr. Mateja Klika Škopić Christian Gramse Dr. Rosario Oliva Sabrina Pospich Laura Neukirch Magiliny Manisegaran Prof. Dr. Stefan Raunser Prof. Dr. Roland Winter Prof. Dr. Ralf Weberskirch Dr. Andreas Brunschweiger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(39):10048-10057
The development of DNA-compatible reaction methodologies is a central theme to advance DNA-encoded screening library technology. Recently, we were able to show that sulfonic acid-functionalized block copolymer micelles facilitated Brønsted acid-promoted reactions such as the Povarov reaction on DNA-coupled starting materials with minimal DNA degradation. Here, the impact of polymer composition on micelle shape, and reaction conversion was investigated. A dozen sulfonic acid-functionalized block copolymers of different molar mass and composition were prepared by RAFT polymerization and were tested in the Povarov reaction, removal of the Boc protective group, and the Biginelli reaction. The results showed trends in the polymer structure-micellar catalytic activity relationship. For instance, micelles composed of block copolymers with shorter acrylate ester chains formed smaller particles and tended to provide faster reaction kinetics. Moreover, fluorescence quenching experiments as well as circular dichroism spectroscopy showed that DNA-oligomer-conjugates, although highly water-soluble, accumulated very effectively in the micellar compartments, which is a prerequisite for carrying out a DNA-encoded reaction in the presence of polymer micelles. 相似文献
915.
We construct a weak conditional expectation from the section C*-algebra of a Fell bundle over a unital inverse semigroup to its unit fibre. We use this to define the reduced C*-algebra of the Fell bundle. We study when the reduced C*-algebra for an inverse semigroup action on a groupoid by partial equivalences coincides with the reduced groupoid C*-algebra of the transformation groupoid, giving both positive results and counterexamples. 相似文献
916.
Characterization of hydro-mechanical processes in reservoir rocks is an essential issue for many geo investigations such as characterization of subsurface fluid flow or geothermal exploitation. For geothermal applications, the role of fractures as storage and transport components of a hydraulic system are highly important. In the present contribution we focus on investigating the effective Skempton coefficient of a damaged porous rock analyzing a modified Cryer problem, which provides a simple model of a porous rock containing a storage and transport pat. The effective Skempton coefficient is defined as the ratio of the increase in mean pore pressure induced by change in confining pressure for undrained boundary conditions. Using approaches from computational homogenization, we evaluate the confining pressure as the negative volume average of the total mean stress. Similarly, we compute the effective fluid pressure in terms of the volume-averaged fluid pressure in the rocks. We compare the numerical results to those from typical experiments and highlight the problems with the latter. The proposed concept for determination of an effective Skempton coefficient based on numerically evaluated volume averages helps to generate a better understanding of the process-inherent constituents. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
917.
Employing the nonperturbative numerical renormalization group method, we study the dynamics of the spin-boson model, which describes a two-level system coupled to a bosonic bath with a spectral density J(omega) proportional to omega(s). We show that, in contrast with the case of Ohmic damping, the delocalized phase of the sub-Ohmic model cannot be characterized by a single energy scale only, due to the presence of a nontrivial quantum phase transition. In the strongly sub-Ohmic regime, s<1, weakly damped coherent oscillations on short time scales are possible even in the localized phase--this is of crucial relevance, e.g., for qubits subject to electromagnetic noise. 相似文献
918.
We investigated the properties of an array of spherical microresonators used as a miniaturized high-resolution spectroscopic device. Sixteen spherical microspheres made from polymethyl methacrylate were placed on a microscope slide serving as an optical wave guide. Light of a tunable narrowband laser source was coupled into this slide so that an evanescent wave was excited on the topside of the slide, where the resonators were placed. This evanescent field generated a particular intensity pattern in the array that depended sensitively on the wavelength. After calibration, that pattern was recorded by a CCD camera and used to identify the wavelength with a resolution of R ~ lambda/Deltalambda = 7 x 10(4). 相似文献
919.
920.
Regtmeier J Grauwin S Eichhorn R Reimann P Anselmetti D Ros A 《Journal of separation science》2007,30(10):1461-1467
Recently, the counter intuitive migration phenomenon of absolute negative mobility (ANM) has been demonstrated to occur for colloidal particles in a suitably arranged post array within a microfluidic device [1]. This effect is based on the interplay of Brownian motion, nonlinear dynamics induced through microstructuring, and nonequilibrium driving, and results in a particle movement opposite to an applied static force. Simultaneously, the migration of a different particle species along the direction of the static force is possible [19], thus providing a new tool for particle sorting in microfluidic device format. The so far demonstrated maximum velocities for micrometer-sized spheres are slow, i. e., in the order of 10 nm per second. Here, we investigate numerically, how maximum ANM velocities can be significantly accelerated by a careful adjustment of the post size and shape. Based on this numerical analysis, a post design is developed and tested in a microfluidic device made of PDMS. The experiment reveals an order of magnitude increase in velocity. 相似文献