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981.
Cameron Nott Semih M. Ölçmen Charles L. Karr Luis C. Trevino 《Applied Intelligence》2007,26(3):251-265
This paper describes the use of artificial intelligence-based techniques for detecting and isolating sensor failures in a
turbojet engine. Specifically, three artificial intelligence (AI) techniques are employed: artificial neural networks (NNs),
statistical expectations, and Bayesian belief networks (BBNs). These techniques are combined into an overall system that is
capable of distinguishing between sensor failure and engine failure—a critical capability in the operation of turbojet engines.
The turbojet engine used in this study is an SR-30 developed by Turbine Technologies. Initially, NNs were designed and trained
to recognize sensor failure in the engine. The increased random noise output from failing sensors was used as the key indicator.
Next, a Bayesian statistical method was used to recognize sensor failure based on the bias error occurring in the sensors.
Finally, a BBN was developed to interpret the results of the NN and statistical evaluations. The BBN determines whether single
or multiple sensor failures signify engine failure, or whether sensor failures represent separate, unrelated incidences. The
BBN algorithm is also used to distinguish between bias and noise errors on sensors used to monitor turbojet performance. The
overall system is demonstrated to work equally well during start-up and main-stage operation of the engine. Results show that
the method can efficiently detect and isolate single or multiple sensor failures within this dynamic environment. 相似文献
982.
983.
Martin G. Jenke Christoph Schreiter Gyu Man Kim Horst Vogel Jürgen Brugger 《Microfluidics and nanofluidics》2007,3(2):189-194
We describe the fabrication and application of a bioanalytical chip, made of SU-8 photoresist, comprising integrated, high
aspect-ratio microfluidic channels, suitable to manipulate and investigate vesicles, cell fragments and biological cells.
A central micrometer-sized aperture allows electrical particle counting and planar membrane experiments, microfluids allow
(sub)micrometer-sized objects to be transported and addressed with different chemicals. Here we show how lipid vesicles are
positioned with micrometer precision within the micro-channels by means of pressure and electrophoretic movement. Our approach
is suited for controlling and investigating (bio)chemical synthesis and cellular signalling processes in ultrasmall individual
vesicles by electro-optical techniques. 相似文献
984.
Marcello Sammarra Jean-François Cordeau Gilbert Laporte M. Flavia Monaco 《Journal of Scheduling》2007,10(4-5):327-336
This paper proposes a tabu search heuristic for the Quay Crane Scheduling Problem (QCSP), the problem of scheduling a fixed number of quay cranes in order to load and unload containers into and from a ship.
The optimality criterion considered is the minimum completion time. Precedence and non-simultaneity constraints between tasks
are taken into account. The former originate from the different kind of operations that each crane has to perform; the latter
are needed in order to avoid interferences between the cranes. The QCSP is decomposed into a routing problem and a scheduling
problem. The routing problem is solved by a tabu search heuristic, while a local search technique is used to generate the
solution of the scheduling problem. This is done by minimizing the longest path length in a disjunctive graph. The effectiveness
of our algorithm is assessed by comparing it to a branch-and-cut algorithm and to a Greedy Randomized Adaptive Search Procedure
(GRASP). 相似文献
985.
François De Vieilleville Jacques-Olivier Lachaud Fabien Feschet 《Journal of Mathematical Imaging and Vision》2007,27(2):139-156
Discrete geometric estimators approach geometric quantities on digitized shapes without any knowledge of the continuous shape. A classical yet difficult problem is to show that an estimator asymptotically converges toward the true geometric quantity as the resolution increases. For estimators of local geometric quantities based on Digital Straight Segment (DSS) recognition this problem is closely linked to the asymptotic growth of maximal DSS for which we show bounds both about their number and sizes on Convex Digital Polygons. These results not only give better insights about digitized curves but indicate that curvature estimators based on local DSS recognition are not likely to converge. We indeed invalidate a conjecture which was essential in the only known convergence theorem of a discrete curvature estimator. The proof involves results from arithmetic properties of digital lines, digital convexity, combinatorics and continued fractions. 相似文献
986.
This paper introduces the notion of well-structured language. A well-structured language can be defined by a labelled well-structured transition system, equipped with an upward-closed set of accepting states. That peculiar class of transition systems has been extensively studied in the field of computer-aided verification, where it has direct an important applications. Petri nets, and their monotonic extensions (like Petri nets with non-blocking arcs or Petri nets with transfer arcs), for instance, are special subclasses of well-structured transition systems. We show that the class of well-structured languages enjoy several important closure properties. We propose several pumping lemmata that are applicable respectively to the whole class of well-structured languages and to the classes of languages recognized by Petri nets or Petri nets with non-blocking arcs. These pumping lemmata allow us to characterize the limits in the expressiveness of these classes of language. Furthermore, we exploit the pumping lemmata to strictly separate the expressive power of Petri nets, Petri nets with non-blocking arcs and Petri nets with transfer arcs. 相似文献
987.
This paper discusses code verification of Reynolds-Averaged Navier Stokes (RANS) solvers with the method of manufactured solutions
(MMS). Examples of manufactured solutions (MSs) for a two-dimensional, steady, wall-bounded, incompressible, turbulent flow
are presented including the specification of the turbulence quantities incorporated in several popular eddy-viscosity turbulence
models. A wall-function approach for the MMS is also described. The flexiblity and usefulness of the MS is illustrated with
calculations performed in three different exercises: the calculation of the flow field using the manufactured eddy-viscosity;
the calculation of the eddy-viscosity using the manufactured velocity field; the calculation of the complete flow field coupling
flow and turbulence variables. The results show that the numerical performance of the flow solvers is model dependent and
that the solution of the complete problem may exhibit different orders of accuracy than in the exercises with no coupling
between the flow and turbulence variables. 相似文献
988.
Bidell Markus P.; Ragen Julia K.; Broach Carl D.; Carrillo Elizabeth A. 《Canadian Metallurgical Quarterly》2007,1(3):204
With the ascension of the Internet as an information resource, Web sites are likely to be the first exposure applicants have to specific programs. The authors evaluated professional psychology program Web sites for ethnic and sexual orientation minority content, discovering that diversity content of Web sites was considerably less than in previously examined paper application materials. Clinical psychology programs were more likely to state a commitment to diversity training while counseling psychology programs were more likely to state a diversity minor/track. School psychology programs had the lowest diversity content on their Web pages. This article explores how graduate psychology program Web sites communicate multicultural information and offers recommendations on using the World Wide Web as a cost-effective tool to attract a diverse student body. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
989.
990.
Derval dos Santos Rosa Flávia Gaboardi Cristina das Graças Fassina Guedes Maria Regina Calil 《Journal of Materials Science》2007,42(19):8093-8100
Blends of poly(β-hydroxybutyrate) (PHB) and low density polyethylene (LDPE) were prepared in proportions of 100/0, 75/25,
50/50, 27/75 and 0/100 (PHB/LDPE wt.%), with and without oxidized polyethylene wax (OPW, 5 wt.%), and the mechanical, thermal
(differential scanning calorimetry and melting flow index, morphological (scanning electron microscopy) and biodegradation
(aging in simulated soil) properties were evaluated. The addition of OPW increased the tensile strength and Young’s modulus
but decreased the elongation at break of the blends. Similarly, OPW increased the T
g
of the pure LDPE and enhanced the melt flow index. Scanning electron microscopy showed that OPW reduced the phase separation
of LDPE and increased the biodegradation during aging in simulated soil. 相似文献