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991.
Jamil Hantash Alan Bartlett Georges Dénès Abdualhafeed Muntasar Philip Oldfield 《Hyperfine Interactions》2005,166(1-4):373-378
A new method of preparation of high performance fluoride ion conductor, BaSnF4, by water leaching of newly discovered barium tin(II) chloride fluorides, has been designed, and the materials have been studied and compared to the solid prepared by the usual dry method. The unit-cell parameters and crystallite dimensions were found to vary with the method of preparation. In addition, the crystallite dimensions were found to be highly anisotropic for the samples obtained by the wet method. The Mössbauer spectrum is made of a large tin(II) quadrupole doublet, and a broad tin(IV) oxide peak due to surface oxidation. The tin(II) spectrum is in agreement with covalently bonded tin(II) having a strongly stereoactive lone pair. An unusually high dependence of the quadrupole splitting at low temperatures was observed (5.8 times larger than for α-SnF2). 相似文献
992.
Pierre Dèbes 《manuscripta mathematica》1996,89(1):107-137
A classical tool for studying Hilbert's irreducibility theorem is Siegel's finiteness theorem forS-integral points on algebraic curves. We present a different approach based ons-integral points rather thanS-integral points. Given an integers>0, an elementt of a fieldK is said to bes-integral if the set of placesv ∈M
K for which |t|v > l is of cardinality ≤s (instead of contained inS for “S-integral”). We prove a general diophantine result fors-integral points (Th.1.4). This result, unlike Siegel's theorem, is effective and is valid more generally for fields with
the product formula. The main application to Hilbert's irreducibility theorem is a general criterion for a given Hilbert subset
to contain values of given rational functions (Th.2.1). This criterion gives rise to very concrete applications: several examples
are given (§2.5). Taking advantage of the effectiveness of our method, we can also produce elements of a given Hilbert subset
of a number field with explicitely bounded height (Cor.3.7). Other applications, including the case thatK is of characteristicp>0, will be given in forthcoming papers ([8], [9]). 相似文献
993.
994.
Nicolas Rivier 《Journal of mathematical chemistry》1993,13(1):1-14
Ground state and elementary excitations (tunnelling modes) in glass are obtained from an analysis of its symmetry, a local gauge invariance. The configuration of glass is represented as a discrete fiber bundle. The base space is a continuous random network, standard model of the structure of covalent glasses. The connection is determined naturally by the elasticity of the network. The bundle is non-trivial, the elastic connection is entangled in one of two ways. Sources of non-triviality are closed loops, threading through odd rings in the network. To restore gauge invariance, tunnelling must occur between the two possible configurations about an odd loop. Entanglement and elementary excitations are labelled by permutations of the covalent bonds incident on an atom.Work supported by the Herbette Foundation. 相似文献
995.
We prove smoothing estimates for Schrödinger equations it∂?+x∂(a(x)x∂?)=0 with a(x)∈BV, real and bounded from below. We then bootstrap these estimates to obtain optimal Strichartz and maximal function estimates, all of which turn out to be identical to the constant coefficient case. We also provide counterexamples showing a∈BV to be in a sense a minimal requirement. Finally, we provide an application to sharp well-posedness for a generalized Benjamin-Ono equation. 相似文献
996.
Samuel Boissière 《Mathematische Zeitschrift》2006,252(3):533-555
When the quotient of a symplectic vector space by the action of a finite subgroup of symplectic automorphisms admits as a
crepant projective resolution of singularities the Hilbert scheme of regular orbits of Nakamura, then there is a natural isomorphism
between the Grothendieck group of this resolution and the representation ring of the group, given by the Bridgeland-King-Reid
map. However, this isomorphism is not compatible with the ring structures. For the Hilbert scheme of points on the affine
plane, we study the multiplicative behavior of this map. 相似文献
997.
998.
Narjès Bellamine-Ben Saoud Gloria Mark 《Computational & Mathematical Organization Theory》2007,13(2):113-146
In this paper, we investigate how complexity theory can benefit collaboration by applying an agent-based computer simulation
approach to a new form of synchronous real-time collaborative engineering design. Fieldwork was conducted with a space mission
design team during their actual design sessions, to collect data on their group conversations, team interdependencies, and
error monitoring and recovery practices. Based on the fieldwork analysis, an agent-based simulator was constructed. The simulation
shows how error recovery and monitoring is affected by the number of small group, or sidebar, conversations, and consequent
noise in the room environment. This simulation shows that it is possible to create a virtual environment with cooperating
agents interacting in a dynamic environment. This simulation approach is useful for identifying the best scenarios and eliminating
potential catastrophic combinations of parameters and values, where error recovery and workload in collaborative engineering
design could be significantly impacted. This approach is also useful for defining strategies for integrating solutions into
organizations.
Narjès Bellamine-Ben Saoud is an Associate Professor at the University of Tunis and Researcher at RIADI-GDL Laboratory, Tunisia. After Computer Science
engineering diploma (1993) of the ENSEEIHT of Toulouse, France, she received her PhD (1996), on groupware design applied to
the study of cooperation within a space project, from the University of Toulouse I, France. Her main research interests concern
studying complex systems particularly by modeling and simulating collaborative and socio-technical systems; developing Computer
Supported Collaborative Learning in tunisian primary schools; and Software Engineering. Her current reserach projects include
modeling and simulation of emergency rescue activities for large-scale accidents, modeling of epidemics and study of malaria,
simulation of collabration artifacts.
Gloria Mark is an Associate Professor in the Department of Informatics, University of California, Irvine. Dr. Mark received her Ph.D.
in Psychology from Columbia University in 1991. Prior to UCI, she was a Research Scientist at the GMD, in Bonn, Germany, a
visiting research scientist at the Boeing Company, and a research scientist at the Electronic Data Systems Center for Advanced
Research. Dr. Mark’s research focuses on the design and evaluation of collaborative systems. Her current projects include
studying worklife in the network-centric organization, multi-tasking of information workers, nomad workers, and a work in
a large-scale medical collaboratory. Dr. Mark is widely published in the fields of CSCW and HCI, is currently the program
co-chair for the ACM CSCW’06 conference and is on the editorial board of Computer Supported Cooperative Work: The Journal
of Collaborative Computing, and e-Service Qu@rterly. 相似文献
999.
1000.
Béatrice Rivière Simon Shaw J.R. Whiteman 《Numerical Methods for Partial Differential Equations》2007,23(5):1149-1166
We consider the usual linear elastodynamics equations augmented with evolution equations for viscoelastic internal stresses. A fully discrete approximation is defined, based on a spatially symmetric or non‐symmetric interior penalty discontinuous Galerkin finite element method, and a displacement‐velocity centred difference time discretisation. An a priori error estimate is given but only the main ideas in the proof of the error estimate are reported here due to the large number of (mostly technical) estimates that are required. The full details are referenced to a technical report. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献