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121.
122.
Kassandra Cendejas Hope E. Parker Dennis Molina Rajib Choudhury 《Journal of inclusion phenomena and macrocyclic chemistry》2017,89(1-2):199-205
In this study, we have examined supramolecular self-assembly process of a hydrophobic guest with a water-soluble host known by the trivial name octa acid (OA). Two octa acids form a capsular assembly only in presence of a nonpolar guest(s). Size and shape of the guest control the stoichiometry of the capsular complex. Here, all atom molecular dynamics simulation has been utilized to investigate complex formation mechanisms of a nonpolar guest (nonylbenzene) with two OA cavitands. Nonylbenzene was encapsulated into the nonpolar cavity of OA capsule owing to solvophobic interactions. Upon encapsulation it was twisted and bent due to lack of free space within the capsule. These unusual forms obtained from the simulation study were in accord with experimental findings. The post-complexation attributes of the guest were regulated by the available free space within the OA and favorable non-covalent interactions between the guest and the walls of the OA capsule. In the identical simulation condition two OA cavitands did not form a capsule without a guest, thus indicating requirement of a guest during the self-assembly of OA cavitands. 相似文献
123.
The effect of sound on the flow around plates with semicircular or square leading edges and square trailing edges located in a low turbulence open jet has been studied. In all circumstances the length of the leading edge separation bubbles associated with square leading edge plates was found to oscillate. When sound was applied to the flow around these plates, the leading edge shear layers reattached closer to the leading edge and the oscillations in bubble length occurred at the applied sound frequency, generating patches of concentrated vorticity in the boundary layers. These vorticity patches moved downstream near the plate surface and then beyond the trailing edge to form vortex cores in a street with a Strouhal number equal to the applied sound value. Sometimes these vortex streets are unstable and break down into streets with Strouhal numbers approaching those observed without sound. These effects of sound were not observed in the flow around plates with semicircular leading edges. Without sound, square leading edge plates of intermediate length did not shed regular vortex streets. 相似文献
124.
The structure of the flow behind wings with finite span (3D) is significantly more complex than the flow behind infinite span (2D) wings. It has been shown that the presence of wingtip vortices behind finite span wings significantly modifies the geometry of the wake flow. It is felt that this modification alters the dynamics of interaction between leading and trailing edge vorticity in a manner that affects the ability of 2D flapping wings to produce thrust. A model of the mean flow skeleton has been proposed from qualitative flow visualization experiments. An unambiguous quantitative representation of the actual flow is required for comparison to the proposed model. To accomplish this the full 3D 3C velocity is required in the volume behind the 3D flapping wing. It is proposed to use stereoscopic multigrid digital particle image velocimetry (SMDPIV) measurements to investigate this unsteady oscillatory flow. This paper reports preliminary SMDPIV measurements along the plane of a symmetrical NACA-profile wing at a Strouhal number of 0.35. Phase averaged measurements are used to investigate the complex flow topology and the influence of the forcing flow on the evolution of the large scale structure of a jet-flow. This paper focuses on optimizing the SMDPIV experimental methodology applied to liquid flows. By refining the 2D 3C technique, the 3D topology of the flow can be investigated with a high degree of accuracy and repeatability. Preliminary results show that the flow is characterized by two pairs of coherent structures of positive and negative vorticity. The arrangement of these structures in the flow is controlled by the motion of the wing. Vorticity of opposite rotation is shed at the extreme heave and pitch positions of the aerofoil to set up a thrust indicative vortex street in support of the suggested topological model. 相似文献
125.
Experimental and theoretical studies of edge effects in rectangular composite strips under tension are discussed. The objective of the study was to investigate the effect of various parameters, including reinforcement material, fiber orientation and the structure of the reinforcement, on the various quantities which are observed in the vicinity of free edges in multidirectionally reinforced laminates. Of particular interest was the confirmation of theoretical results related to differences in response of graphite- and boron-reinforced laminates. Experiments consisted of moiré measurements of surface-displacement patterns which were compared with theoretical predictions, and examination of failure levels. The experiments were carried out on AVCO 5505 boron and Whitaker 5206 MODMOR II graphite-reinforced angle-ply laminates in which both stacking sequence and fiber orientation were varied parametrically. Moiré techniques were developed which allowed observation of displacements on both the wide surface and along the narrow edge of 1 in.-wide × 16-ply-thick (.085 in.-.105 in.) laminates. 相似文献
126.
Convergent Synthesis of 2H-Chromenes - a Formal [3+3] Cycloaddition by a One-pot, Three-Step Cascade
In cases in which the palladium-catalyzed coupling of a bromoquinone with a vinyl stannane affords a vinyl quinone that enolizes, the resulting ortho-quinone methide undergoes an oxa-6π electrocyclization. Enolization is promoted by the presence of a polar additive. The net conversion is a formal [3+3] cycloaddition that gives 2H-chromenes. Because the first two steps of the cascade are catalyzed, the overall conversion is an example of multicatalysis. Yields for the optimized, one-pot protocol are dramatically improved over the conventional stepwise process. 相似文献
127.
Ensembles of engineered cardiac tissues for physiological and pharmacological study: heart on a chip
Traditionally, muscle physiology experiments require multiple tissue samples to obtain morphometric, electrophysiological, and contractility data. Furthermore, these experiments are commonly completed one at a time on cover slips of single cells, isotropic monolayers, or in isolated muscle strips. In all of these cases, variability of the samples hinders quantitative comparisons among experimental groups. Here, we report the design of a "heart on a chip" that exploits muscular thin film technology--biohybrid constructs of an engineered, anisotropic ventricular myocardium on an elastomeric thin film--to measure contractility, combined with a quantification of action potential propagation, and cytoskeletal architecture in multiple tissues in the same experiment. We report techniques for real-time data collection and analysis during pharmacological intervention. The chip is an efficient means of measuring structure-function relationships in constructs that replicate the hierarchical tissue architectures of laminar cardiac muscle. 相似文献
128.
The first total synthesis of (-)-arabilin, a Streptomyces metabolite that inhibits hormone activation of the androgen receptor, has been completed. The key step, a [1,7]-hydrogen shift, establishes the enol ether-containing skipped-tetraene substructure. This nonenzymatic pericyclic reaction is considered to be biomimetic. 相似文献
129.
Oscar Salas-Solano Kunnel Babu SungAe Suhr Park Xinfeng Zhang Li Zhang Zoran Sosic Boris Boumajny Ming Zeng Kuang-Chuan Cheng Angelia Reed-Bogan Stacey Cummins-Bitz David A. Michels Monica Parker Paulina Bonasia Mingfang Hong Steven Cook Margaret Ruesch David Lamb Dora Bolyan Steffen Kiessig Darren Allender Brian Nunnally 《Chromatographia》2011,73(11-12):1137-1144
Interlaboratory comparisons are essential to bringing emerging technologies into biopharmaceutical industry practice and regulatory acceptance. As a result, an international team including 12 laboratories from 10 independent biopharmaceutical companies in the United States and Switzerland was formed to evaluate the precision and robustness of capillary isoelectric focusing (CIEF) to assess the charge heterogeneity of monoclonal antibodies. The different laboratories determined the apparent pI and the relative distribution of the charge isoforms of a representative monoclonal antibody (rMAb) sample using the same CIEF method. Statistical evaluation of the data was performed to determine within and between-laboratory consistencies and outlying information. The apparent pI data generated for each charge variant peak showed very good precision between laboratories with percentage of RSD values of ??0.5%. Similarly, the percentage of RSD for the rMAb charge variants percent peak area values are ??4.4% across different laboratories with different analysts using different lots of ampholytes and multiple instruments. Taken together, these results validate the appropriate use of CIEF in the biopharmaceutical industry in support of regulatory submissions. 相似文献
130.
Rose RA Greaves SJ Oliver TA Clark IP Greetham GM Parker AW Towrie M Orr-Ewing AJ 《The Journal of chemical physics》2011,134(24):244503
The dynamics of reactions of CN radicals with cyclohexane, d(12)-cyclohexane, and tetramethylsilane have been studied in solutions of chloroform, dichloromethane, and the deuterated variants of these solvents using ultraviolet photolysis of ICN to initiate a reaction. The H(D)-atom abstraction reactions produce HCN (DCN) that is probed in absorption with sub-picosecond time resolution using ~500 cm(-1) bandwidth infrared (IR) pulses in the spectral regions corresponding to C-H (or C-D) and C≡N stretching mode fundamental and hot bands. Equivalent IR spectra were obtained for the reactions of CN radicals with the pure solvents. In all cases, the reaction products are formed at early times with a strong propensity for vibrational excitation of the C-H (or C-D) stretching (v(3)) and H-C-N (D-C-N) bending (v(2)) modes, and for DCN products there is also evidence of vibrational excitation of the v(1) mode, which involves stretching of the C≡N bond. The vibrationally excited products relax to the ground vibrational level of HCN (DCN) with time constants of ~130-270 ps (depending on molecule and solvent), and the majority of the HCN (DCN) in this ground level is formed by vibrational relaxation, instead of directly from the chemical reaction. The time-dependence of reactive production of HCN (DCN) and vibrational relaxation is analysed using a vibrationally quantum-state specific kinetic model. The experimental outcomes are indicative of dynamics of exothermic reactions over an energy surface with an early transition state. Although the presence of the chlorinated solvent may reduce the extent of vibrational excitation of the nascent products, the early-time chemical reaction dynamics in these liquid solvents are deduced to be very similar to those for isolated collisions in the gas phase. The transient IR spectra show additional spectroscopic absorption features centered at 2037 cm(-1) and 2065 cm(-1) (in CHCl(3)) that are assigned, respectively, to CN-solvent complexes and recombination of I atoms with CN radicals to form INC molecules. These products build up rapidly, with respective time constants of 8-26 and 11-22 ps. A further, slower rise in the INC absorption signal (with time constant >500 ps) is attributed to diffusive recombination after escape from the initial solvent cage and accounts for more than 2/3 of the observed INC. 相似文献