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71.
Maurice Courbage 《控制论与系统》2013,44(3-4):385-392
Time operator describes the lifetime of quantum irreversible processes on the level of statistical states. The existence, interpretation, and properties of time operator are discussed and the master equation is derived. Time operator exists also in other dynamical systems with mixing properties. Models of non-Markovian processes with long memory having a time operator are discussed. 相似文献
72.
Tomaz Kosmac David Maurice Thomas H. Courtney 《Journal of the American Ceramic Society》1993,76(9):2345-2352
The feasibility and kinetics of synthesizing various nickel sulfides by milling of elemental mixtures of Ni and S in a high-energy shaker mill have been investigated. The phases Ni3 S2 and the high-temperature polymorph of NiS are formed readily via such processing. In distinction, it requires prolonged milling to obtain Ni7 S6 ; NiS2 can only be obtained as a minor reaction product; and Ni3 S4 cannot be formed by milling for the conditions of this study. Structural evolution during synthesis and the kinetics of Ni3 S2 formation are investigated in depth. S coats the Ni particles and sulfide formation takes place at the interface of the elements after a certain degree of microstructural refinement due to the plastic deformation accompanying milling. Ni3 S2 forms rapidly at this stage. However, a stasis in the reaction is then observed. This is associated with NiS formation and a slight decrease in the amount of Ni3 S2 . The stasis is of approximately 5-min duration and is followed by a recurrence in the formation of Ni3 S2 and a disappearance of the NiS phase. The kinetics can be mimicked through a model of the mechanical alloying process. The model is able to predict the time dependence of the initial and later stages of Ni3 S2 formation and the effect of other parameters, such as mill atmosphere and use of premilled powder, on the reaction kinetics. The microstructures found in the intermediate to later stages of milling are similar to those associated with self-sustaining reactions. 相似文献
73.
Summary Thesnapshot object is an important tool for constructing wait-free asynchronous algorithms. We relate the snapshot object to thelattice agreement decision problem. It is shown that any algorithm for solving lattice agreement can be transformed into an implementation of a snapshot object. The overhead cost of this transformation is only a linear number of read and write operations on atomic single-writer multi-reader registers. The transformation uses an unbounded amount of shared memory. We present a deterministic algorithm for lattice agreement that usedO (log2
n) operations on 2-processorTest & Set registers, plusO (n) operations on atomic single-writer multi-reader registers. The shared objects are used by the algorithm in adynamic mode, that is, the identity of the processors that access each of the shared objects is determined dynamically during the execution of the algorithm. By a randomized implementation of 2-processorsTest & Set registers from atomic registers, this algorithm implies a randomized algorthm for lattice agreement that uses an expected number ofO (n) operations on (dynamic) atomic single-writer multi-reader registers. Combined with our transformation this yields implementations of atomic snapshots with the same complexity.Cambridge Research Laboratory, Digital Equipment Corporation
Hagit Attiya received the B.Sc. degreeiin Mathematics and Computer Science from the Hebrew University of Jerusalem, in 1981, the M.Sc. and Ph.D. degrees in Computer Science from the Hebrew University of Jerusalem, in 1983 and 1987, respectively. She is presently a senior lecturer at the departtment of Computer Science at the Technion, Israel Institute of Technology. Prior to this, she has been a post-doctoral research associate at the Laboratory for Computer Science at M.I.T. Her general research interests are distributed computation and theoretical computer science. More specific interests include fault-tolerance, timing-based and asynchronous algorithms.
Maurice Herlihy received the A.B. degree in Mathematics from Harvard University, and the M.S. and the Ph.D. degrees in Computer Science from M.I.T. From 1984 to 1989 he was a faculty member in the Computer Science Department at Carnegie Mellon University in Pittsburgh, PA. In 1989 he joined the research staff at the Digital Equipment Corporation's Cambridge Research Laboratory in Cambridge MA. Since 1994, he has been on the faculty at the Computer Science Department at Brown University. Dr. Herlihy's research interests encompass practical and theoretical aspects of distributed and concurrent computation.
Ophir achman received a B.A. in computer science from the Technion, Haifa, Israel in 1989 and M.Sc. in computer science from the Technion, Haifa, Israel, in 1992. He is now studying for a D.Sc. in computer science at the Technion. His currentarea of research is distributed computing, and in particular, asynchronous shared memory systems.This work appeared in preliminary form in proceedings ofthe 6th International Workshop on Distributed Algorithms [12]. This research was partially supported by grant No. 92-0233 from the United States-Israel Binational Science Foundation (BSF), Jerusalem, Technion V.P.R. funds — B. and G. Greenberg Research Fund (Ottawa), and the fund for the promotion of research in the TechnionPart of the work of this author was performed while visiting DEC Cambridge Research Laboratory 相似文献
74.
Xavier Maurice Anders Sandholm Nicolas Pronost Ronan Boulic Daniel Thalmann 《The Visual computer》2009,25(9):835-842
Today, to create and to simulate a virtual anatomical version of a subject is useful in the decision process of surgical treatments.
The muscular activity is one of the factors which can contribute to abnormal movements such as in spasticity or static contracture.
In this paper, we propose a numerical solution, based on the Finite Element (FE) method, able to estimate muscles deformations
during contraction. Organized around a finite element solver and a volumetric environment, this solution is made of all the
modeling and simulation processes from the discretization of the studied domain to the visualization of the results. The choices
of materials and properties of the FE model are also presented such as the hyperelasticity, the contention model based on
inter-meshes neighboring nodes pairing, and the estimation of nodal forces based on the subject-specific muscular forces and
action lines.
相似文献
Nicolas PronostEmail: |
75.
Flavio P. Junqueira Keith Marzullo Maurice Herlihy Lucia Draque Penso 《Distributed Computing》2010,23(2):135-149
Many replication protocols employ a threshold model when expressing failures they are able to tolerate. In this model, one assumes that no more than t out of n components can fail, which is a good representation when failures are independent and identically distributed (IID). In many real systems, however, failures are not IID, and a straightforward application of threshold protocols yields suboptimal results. Here, we examine the problem of transforming threshold protocols into survivor-set protocols tolerating dependent failures. Our main goal is to show the equivalence between the threshold model and the core/survivor set model. Toward this goal, we develop techniques to transform threshold protocols into survivor set ones. Our techniques do not require authentication, self-verification or encryption. Our results show in one case that we can transform a threshold protocol to a subset by spreading a number of processes across processors. This technique treats a given threshold algorithm as a black box, and consequently can transform any threshold algorithm. However, it has the disadvantage that the transformation is not possible for all sets of survivor sets. The second technique instead focuses on transforming voters: functions that evaluate to a value out of a set of tallied values in a replication protocol. Voters are an essential part of many fault-tolerant protocols, and we show a universal way of transforming them. With such a transformation we expect that a large number of protocols in the literature can be directly transformed with our technique. It is still an open problem, however, if the two models are equivalent, and our results constitute an important first step in this direction. 相似文献
76.
Daan Fierens Jan Ramon Maurice Bruynooghe Hendrik Blockeel 《Annals of Mathematics and Artificial Intelligence》2008,54(1-3):99-133
We discuss how to learn non-recursive directed probabilistic logical models from relational data. This problem has been tackled before by upgrading the structure-search algorithm initially proposed for Bayesian networks. In this paper we show how to upgrade another algorithm for learning Bayesian networks, namely ordering-search. For Bayesian networks, ordering-search was found to work better than structure-search. It is non-obvious that these results carry over to the relational case, however, since there ordering-search needs to be implemented quite differently. Hence, we perform an experimental comparison of these upgraded algorithms on four relational domains. We conclude that also in the relational case ordering-search is competitive with structure-search in terms of quality of the learned models, while ordering-search is significantly faster. 相似文献
77.
Ada A. Bacetty Maurice E. Snook Anthony E. Glenn James P. Noe Padmaja Nagabhyru Charles W. Bacon 《Journal of chemical ecology》2009,35(7):844-850
Tall fescue (Festuca arundinacea) forms a symbiotic relationship with the clavicipitalean fungal endophyte Neotyphodium coenophialum. Endophyte-infected grass is tolerant to nematode, but the factors responsible are unknown. One objective of this work was
to determine if root extracts of tall fescue effected chemoreceptor activity of Pratylenchus scribneri by using an in vitro chemoreception bioassay. Another objective was to determine if specific ergot alkaloids (ergovaline, ergotamine, a-ergocryptine,
ergonovine), and loline alkaloids, all produced by the fungal endophyte, altered chemotaxis with this bioassay. Methanolic
extract from roots altered chemotaxis activities in this nematode but only from roots of plants cultured 45 ≥ d, which repelled
nematodes. Extracts prepared from noninfected grasses were attractants. This assay indicated that the alkaloids were either
repellents or attractants. N-formylloline was an attractant at concentrations of 20 μg/ml and lower, while at higher concentrations
it was a repellent. Ergovaline, the major ergot alkaloid produced by the endophyte, was repellent at both high and low concentrations
and caused complete death of the nematodes. 相似文献
78.
Gerardo C Saucedo Pedro B Gonzlez Sergio M Revah Gustavo G Viniegra Maurice Raimbault 《Journal of the science of food and agriculture》1990,50(4):467-477
The major effect of Lactobacillus inoculation on laboratory cassava (Manihot esculenta Crantz) silage was a change from a heterofermentative pattern observed in natural silage to a homofermentation. Small amounts of starter culture (1% v/w) were required to produce a high level of lactic acid (> 28 g kg?1 DM) and to reach a pH of at least 4. The Gompertz model was used to evaluate the effect of inoculation level on the lactic formation based on kinetic criteria. Also an empirical pH lactic acid correlation was proposed to monitor the progress of ensiling, based solely on pH measurements. The simulation model may be used to improve guidelines for silo safety and to evaluate the effect of lactobacilli inoculants. 相似文献
79.
Julie Garvey David Newport Fereydoun Lakestani Maurice Whelan Shiju Joseph 《Microfluidics and nanofluidics》2008,5(1):77-87
This paper presents micro-interferometry as a measurement technique to extract temperature profiles and/or mass transfer gradients
rapidly and locally in micro-devices. Interferometry quantifies the phase change between two or more coherent light beams
induced by temperature and/or mass concentration. Previous work has shown that temporal noise is a limiting factor in microscale
applications. This paper examines phase stepping and heterodyne phase retrieval techniques with both CCD and CMOS cameras.
CMOS cameras are examined owing to the high speed at which images can be acquired which is particularly relevant to heterodyne
methods. It is found that heterodyne retrieval is five times better than phase stepping being limited to 0.01 rad or λ/628.
This is twice the theoretical limit of λ/1,000. The technique is demonstrated for mixing in a T-junction with a 500 μm square
channel and compared favourably to a theoretical prediction from the literature. Further issues regarding application to temperature
measurements are discussed. 相似文献
80.
荷兰DSM是世界最先进的化学和生物技术公司之一,它不仅是世界领先的制药业供应商,而且还是化工原料、农用化学品等领域的重要供应商之一.自1902年成立以来,就一直在荷兰林堡(Limburg)的经济和社会发展中扮演着重要的角色. 相似文献