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91.
The refined grains in both as-cast Mg-10Y-1Zn-2Zr (WZ101?K, wt.%) and Mg-10Y-1Al (WA101, wt.%) alloys have been found to have superior thermal stability after solution treatment. Plate-shaped, but different polytypes of long-period stacking ordered (LPSO) phases distributed along grain boundaries are considered as the predominant inhibitors of grain growth. Based on the plate-shaped features of the LPSO phases, a modified Zener’s model is established and the predicted limiting grain sizes are in a good agreement with the experimental results. Therefore, this model has strong potential for designing advanced Mg-RE-based alloys with high strength and high creep resistance at high temperatures. 相似文献
92.
Jie Song Eunji Lee Byoung‐Ki Cho 《Journal of polymer science. Part A, Polymer chemistry》2013,51(2):446-456
A well‐defined (PEO‐PS)2‐PLA miktoarm terpolymer ( 1 ) was synthesized by stepwise click reactions of individually prepared poly(ethylene oxide) (PEO), polystyrene (PS, polymerized by atom transfer radical polymerization), and polylactide (PLA, polymerized by ring‐opening polymerization) blocks. As characterized by differential scanning calorimetry and small‐angle X‐ray scattering techniques, the terpolymer self‐assembled into a hexagonal columnar structure consisting of PLA/PEO cylindrical cores surrounded by PS chains. In contrast, the ion‐doped sample ( 1‐Li+ ) with lithium concentration per ethylene oxide = 0.2 exhibited a three‐phase lamellar structure, which was attributed to the microphase separation between PEO and PLA blocks and to the conformational stabilization of the longest PLA chain. The two‐phase columnar morphology before the ion doping was used to prepare a nanoporous material. PLA chains in the cylindrical core region were hydrolyzed by sodium hydroxide, producing nanopores with a pore diameter of about 14 nm. The resulted nanoporous material sank to the bottom in water, because of water‐compatible PEO chains on the walls. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
93.
《Comptes Rendus Physique》2013,14(6):447-450
One of the major emerging fields of research of the beginning of this century concerns living fluids. By “living fluids”, we mean two major categories of complex fluids: (i) fluids which are essential to life, like blood, and (ii) active fluids made of particles that are able to propel themselves in the suspending fluid by converting a form of their energy into mechanical motion. Studies on active fluids have known a considerable interest since the last decade. Blood might be viewed as an old topic, but the progresses in experimental techniques, analytical concepts and numerics, have contributed nowadays to a dramatic renewal of the interest in this field, with a great potential towards understanding physical and mechanical factors in cardiovascular diseases. These fields have considerably strengthened interdisciplinary research. The series of reviews of this dossier focus on the tremendous recent progress achieved in research on living fluids both from the experimental and theoretical points of views. These reviews present also the major open issues, making of this dossier a unique guide for future research in these fields. This project grew up thanks to the international summer school that we organized on the topic “living fluids” at the IES (Institut dʼétudes scientifiques) of Cargèse (Corsica) in 2012. 相似文献
94.
Pierrick Nun Violaine Pérez Monique Calmès Jean Martinez Frédéric Lamaty 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(12):3773-3779
The asymmetric alkylation of Schiff bases under basic conditions in a ball mill was performed. The starting Schiff bases of glycine were prepared beforehand by milling protected glycine hydrochloride and benzophenone imine, in the absence of solvent. The Schiff base was then reacted with a halogenated derivative in a ball mill in the presence of KOH. By adding a chiral ammonium salt derived from cinchonidine, the reaction proceeded asymmetrically under phase‐transfer catalysis conditions, giving excellent yields and enantiomeric excesses up to 75 %. Because an equimolar amount of starting material was used, purification was greatly simplified. 相似文献
95.
96.
97.
The anomalies of the second and third-order elastic constants have been considered for the phase transition of strontium titanate
within the framework of Landau’s theory. All the anomalies of the second-order elastic constants have been obtained in a single
formula using Kronecker delta functions and relations among them have been established. The real parts ofC*11 andC*44 decrease steeply across the transition temperature and thereafter flatly tend to their asymptotic values in the low temperature
phase agreeing qualitatively with experimental observations. We have also derived expressions for the third-order elastic
anomalies and discussed the temperature variation of the real part ofC*111. We have derived expressions for the attenuation of the longitudinal and transverse waves along certain simple symmetry directions
and have shown that there is nearly good agreement with experimental observations. 相似文献
98.
The three-component ionic microemulsion system consisting of AOT/water/decane shows an unusual phase behavior in the vicinity
of room temperature. The phase diagram in the temperature-volume fraction (of the dispersed phase) plane exhibits a lower
consolute critical point at about 40 degrees centigrades and 10% volume fraction. A percolation line, starting from the vicinity
of the critical point, cuts across the plane, extending to high volume fraction side at progressively lower temperatures.
In this paper we review the evidence that allows to interpret the phase behavior of our system in terms of interacting spherical
droplets. We also investigate the dynamics of droplets, below and approaching the critical point by dynamic light scattering.
The first cumulant and time evolution of the droplet density correlation function can be quantitatively calculated by assuming
the existence of polydispersed fractal clusters formed by the microemulsion droplets due to attraction. The relaxation phenomena
observed in an extensive set of measurements of electrical conductivity and permittivity close to percolation is also reviewed
and interpreted through the same cluster-forming mechanism, which reproduces the most relevant features of the frequency-dependent
complex dielectric constant of this system.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
99.
100.
The point-group and space-group symmetry of the controversial fluorite-based stoichiometric superlath phase of ø1 (CaZr4O9: Z=16), considered to be a coherently-intergrown subphase of lime-stabilized zirconia, is examined. Using convergent-beam and selected-area electron diffraction, it is determined that the space group of ø1 is C2/c, in apparent agreement with earlier studies utilizing other diffraction techniques. 相似文献