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911.
The density profiles in a fluid interacting with the two identical solid walls of a closed long slit were calculated for wide ranges of the number of fluid molecules in the slit and temperature by employing a nonlocal density functional theory. Using argon as the sample fluid and considering the walls composed of solid carbon dioxide, it is shown that the density profile corresponding to the stable state of the fluid considerably changes its shape with increasing average density rho(av) of the fluid inside the slit. Temperature dependent critical values rho(sb1) and rho(sb2) of rho(av) were identified, such that for rho(sb1)相似文献
912.
It was recently suggested that the swelling of neutral multilipid bilayers upon addition of a salt can be simply explained only by the electrolyte screening of the van der Waals attractions, while assuming that the hydration force and the repulsion due to thermal undulations of membranes are unaffected by the salt. While we agree that the screening of the van der Waals interactions plays a role, we suggest that the increase in the hydration force upon addition of a salt has also to be taken into account. In a statistical model, which accounts for the membrane undulations, parameters could be found to explain the multibilayer swelling even when the van der Waals attraction is considered unaffected by the electrolyte screening. These results point out that the decrease by a factor of three of the Hamaker constant upon addition of a salt, suggested recently to be responsible for the swelling of neutral multilipid bilayers, is perhaps too large, and a smaller decrease in Hamaker constant, coupled with the above mentioned effects might explain the swelling. 相似文献
913.
Mandell DJ Chorny I Groban ES Wong SE Levine E Rapp CS Jacobson MP 《Journal of the American Chemical Society》2007,129(4):820-827
Post-translational phosphorylation plays a key role in regulating protein function. Here, we provide a quantitative assessment of the relative strengths of hydrogen bonds involving phosphorylated amino acid side chains (pSer, pAsp) with several common donors (Arg, Lys, and backbone amide groups). We utilize multiple levels of theory, consisting of explicit solvent molecular dynamics, implicit solvent molecular mechanics, and quantum mechanics with a self-consistent reaction field treatment of solvent. Because the approximately 6 pKa of phosphate suggests that -1 and -2 charged species may coexist at physiological pH, hydrogen bonds involving both protonated and deprotonated phosphates for all donor-acceptor pairs are considered. Multiple bonding geometries for the charged-charged interactions are also considered. Arg is shown to be capable of substantially stronger salt bridges with phosphorylated side chains than Lys. A pSer hydrogen-bond acceptor tends to form more stable interactions than a pAsp acceptor. The effect of phosphate protonation state on the strengths of the hydrogen bonds is remarkably subtle, with a more pronounced effect on pAsp than on pSer. 相似文献
914.
915.
Vlaisavljevich E Janka LP Ong KG Rajachar RM 《IEEE transactions on bio-medical engineering》2011,58(3):698-704
Interfacial fibrosis is known to dramatically decrease the lifespan, stability, and function of biomedical implants and bone-anchored prosthetics. Bioactive coatings aimed at mitigating fibrous adhesions are one of the approaches to alleviate the problem. In this paper, we are developing a bioactive coating based upon a magnetoelastic (ME) material that vibrates in response to an ac magnetic field. In order to establish these coatings for this purpose, the ME material was first rendered bioactive through the sequential addition of polyurethane and chitosan thin films. Indirect live/dead assays were performed showing increased cell viability for polyurethane and chitosan-coated sensors compared to the uncoated controls. Direct adhesion experiments were performed to test the response of fibroblasts cultured on static and vibrated ME materials. Results showed cells adherent to static but not vibrated coatings. Detached cells showed no viability loss compared to controls. The finding that submicrometer ME vibrations can prevent cell adhesion in vitro without inducing cell death suggests the potential of these coatings to effectively control interfacial fibrosis. Future work will address the effect of vibrations on cell morphology and local gene expression in vitro, as well as fibrous tissue formation in vivo. 相似文献
916.
We apply the modal coherence theory to evaluate the spatial mode structure of a 2×2 phase-coupled array of vertical cavity surface emitting lasers (VCSELs). The eigenmode structure is extracted for different pump currents by measuring the degree of spatial coherence of all VCSEL pairs in the array. The results reveal the impact of optical disorder and spatial hole burning on the modal discrimination. The approach is useful more generally for the evaluation of spatial mode content of other laser array. 相似文献
917.
Dr. Aldo Peschiulli Veerle Smout Dr. Thomas E. Storr Dr. Emily A. Mitchell Zdeněk Eliáš Prof. Dr. Wouter Herrebout Dr. Didier Berthelot Dr. Lieven Meerpoel Prof. Dr. Bert U. W. Maes 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(31):10378-10387
Transition‐metal‐catalyzed sp3 C? H activation has emerged as a powerful approach to functionalize saturated cyclic amines. Our group recently disclosed a direct catalytic arylation reaction of piperidines at the α position to the nitrogen atom. 1‐(Pyridin‐2‐yl)piperidine could be smoothly α‐arylated if treated with an arylboronic ester in the presence of a catalytic amount of [Ru3(CO)12] and one equivalent of 3‐ethyl‐3‐pentanol. A systematic study on the substrate and reagent scope of this transformation is disclosed in this paper. The effect of substitution on both the piperidine ring and the arylboronic ester has been investigated. Smaller (pyrrolidine) and larger (azepane) saturated ring systems, as well as benzoannulated derivatives, were found to be compatible substrates with the α‐arylation protocol. The successful use of a variety of heteroarylboronic esters as coupling partners further proved the power of this direct functionalization method. Mechanistic studies have allowed for a better understanding of the catalytic cycle of this remarkable transformation featuring an unprecedented direct transmetalation on a RuII? H species. 相似文献
918.
Shyuan Yang Brian R. Tull Nadia K. Pervez Limin Huang Eli S. Leland Daniel A. Steigart Stephen O'Brien Ioannis Kymissis 《Journal of Polymer Science.Polymer Physics》2013,51(1):35-38
Nanoparticle polymer composite capacitors have been examined for some time as a route to high performance, printable capacitors. One approach to creating these composites is to use a particle film together with vapor deposited polymers, which can yield high performance, but also forms a structurally asymmetric device. The performance of a nanoparticle (Ba, Sr)TiO3 (BST)/parylene‐C composite capacitor is compared to that of a nanoparticle BST capacitor without the polymer layer under both directions of bias. The composite device shows a five orders of magnitude improvement in the leakage current under positive bias of the bottom electrode relative to the pure‐particle device, and four orders of magnitude improvement when the top electrode is positively biased. The voltage tolerance of the device is also improved and asymmetric (44 V vs. 28 V in bottom and top positive bias, respectively). This study demonstrates the advantage of this class of composite device construction, but also shows that proper application of the device bias in this type of asymmetrical system can yield an additional benefit. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 相似文献
919.
Distribution and behavior of some radionuclides associated with the Trinity nuclear test 总被引:1,自引:0,他引:1
Jeremy J. Bellucci Christine Wallace Elizabeth C. Koeman Antonio Simonetti Peter C. Burns Jeremy Kieser Eli Port Terri Walczak 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):2049-2057
The activities of 133Ba, 137Cs, 152Eu, 154Eu, 155Eu, 239Pu, and 241Am were determined by gamma spectroscopy on the largest sample set (n = 49) of bulk trinitite to date. The range in activity for all isotopes is large. For example, the activity of 241Am (normalized to the time of detonation) ranges between 1 and 42 Bq/g. Comparison of activities for isotopes derived from the device, 241Am versus 137Cs, 155Eu, and 239Pu, indicate positive trends. Correlations were not observed between the activities of the soil-derived activation products 152Eu and 154Eu and the radioisotopes from the device. The calculated ratio of fission products (155Eu/137Cs) is 0.012 ± .006 (1σ, n = 3), which is lower than predicted for the thermal neutron-induced fission of 239Pu (~0.03). This discrepancy may be attributed to the spontaneous fission of the natural U tamper resulting in mixing between fission products from 239Pu and 235U. The spatial distribution of the trinitite samples relative to ground zero has been modeled based on the activity of 152Eu. The calculated distances do not correlate with any of the activities for the radioisotopes investigated here, and suggest a relatively homogeneous distribution. However, trinitite samples with the highest activities for 137Cs, 239Pu, and 241Am yield the shortest calculated distances of 50–60 m away from ground zero. 相似文献
920.
Maarten Goesten Dr. Eli Stavitski Dr. Evgeny A. Pidko Canan Gücüyener Bart Boshuizen Dr. Steven N. Ehrlich Prof. Emiel J. M. Hensen Prof. Freek Kapteijn Dr. Jorge Gascon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(24):7809-7816
We present an in situ small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) and quick‐scanning extended X‐ray absorption fine‐structure (QEXAFS) spectroscopy study on the crystallization of the metal–organic framework ZIF‐7. In combination with DFT calculations, the self‐assembly and growth of ZIF‐7 microrods together with the chemical function of the crystal growth modulator (diethylamine) are revealed at all relevant length scales, from the atomic to the full crystal size. 相似文献