全文获取类型
收费全文 | 3640篇 |
免费 | 189篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 49篇 |
综合类 | 35篇 |
化学工业 | 1109篇 |
金属工艺 | 86篇 |
机械仪表 | 65篇 |
建筑科学 | 274篇 |
矿业工程 | 7篇 |
能源动力 | 71篇 |
轻工业 | 387篇 |
水利工程 | 18篇 |
石油天然气 | 5篇 |
无线电 | 214篇 |
一般工业技术 | 706篇 |
冶金工业 | 190篇 |
原子能技术 | 35篇 |
自动化技术 | 583篇 |
出版年
2023年 | 49篇 |
2022年 | 86篇 |
2021年 | 131篇 |
2020年 | 67篇 |
2019年 | 86篇 |
2018年 | 91篇 |
2017年 | 73篇 |
2016年 | 108篇 |
2015年 | 107篇 |
2014年 | 141篇 |
2013年 | 171篇 |
2012年 | 194篇 |
2011年 | 273篇 |
2010年 | 202篇 |
2009年 | 189篇 |
2008年 | 177篇 |
2007年 | 156篇 |
2006年 | 151篇 |
2005年 | 126篇 |
2004年 | 112篇 |
2003年 | 79篇 |
2002年 | 96篇 |
2001年 | 74篇 |
2000年 | 70篇 |
1999年 | 68篇 |
1998年 | 62篇 |
1997年 | 57篇 |
1996年 | 35篇 |
1995年 | 48篇 |
1994年 | 44篇 |
1993年 | 29篇 |
1992年 | 30篇 |
1991年 | 36篇 |
1990年 | 29篇 |
1989年 | 30篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 16篇 |
1984年 | 27篇 |
1983年 | 16篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1978年 | 26篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1975年 | 10篇 |
1974年 | 22篇 |
1969年 | 12篇 |
1968年 | 10篇 |
排序方式: 共有3834条查询结果,搜索用时 15 毫秒
71.
Kyriakos Anastasakis Behzad Bordbar Geri Georg Indrakshi Ray 《Software and Systems Modeling》2010,9(1):69-86
The Unified Modeling Language (UML) is the de facto language used in the industry for software specifications. Once an application
has been specified, Model Driven Architecture (MDA) techniques can be applied to generate code from such specifications. Since
implementing a system based on a faulty design requires additional cost and effort, it is important to analyse the UML models
at earlier stages of the software development lifecycle. This paper focuses on utilizing MDA techniques to deal with the analysis
of UML models and identify design faults within a specification. Specifically, we show how UML models can be automatically
transformed into Alloy which, in turn, can be automatically analysed by the Alloy Analyzer. The proposed approach relies on
MDA techniques to transform UML models to Alloy. This paper reports on the challenges of the model transformation from UML
class diagrams and OCL to Alloy. Those issues are caused by fundamental differences in the design philosophy of UML and Alloy.
To facilitate better the representation of Alloy concepts in the UML, the paper draws on the lessons learnt and presents a
UML profile for Alloy. 相似文献
72.
Jörg Becker Daniel F. Beverungen Ralf Knackstedt 《Information Systems and E-Business Management》2010,8(1):33-66
Confronted with decreasing margins and a rising customer demand for integrated solutions, manufacturing companies integrate
complementary services into their portfolio. Offering value bundles (consisting of services and physical goods) takes place
in integrated product–service systems, spanning the coordinated design and delivery of services and physical goods for customers.
Conceptual Modeling is an established approach to support and guide such efforts. Using a framework for the design and delivery
of value bundles as an analytical lens, this study evaluates the current support of reference models and modeling languages
for setting up conceptual models for an integrated design and delivery of value bundles. Consecutively, designing modeling
languages and reference models to fit the requirements of conceptual models in product–service systems are presented as upcoming
challenges in Service Research. To guide further research, first steps are proposed by exemplarily integrating reference models
and modeling languages stemming from the service and manufacturing domains. 相似文献
73.
A two-layer architecture for dynamic real-time optimization (or nonlinear modelpredictive control (NMPC) with an economic objective) is presented, where the solution of the dynamic optimization problem is computed on two time-scales. On the upper layer, a rigorous optimization problem is solved with an economic objective function at a slow time-scale, which captures slow trends in process uncertainties. On the lower layer, a fast neighboring-extremal controller is tracking the trajectory in order to deal with fast disturbances acting on the process. Compared to a single-layer architecture, the two-layer architecture is able to address control systems with complex models leading to high computational load, since the rigorous optimization problem can be solved at a slower rate than the process sampling time. Furthermore, solving a new rigorous optimization problem is not necessary at each sampling time if the process has rather slow dynamics compared to the disturbance dynamics. The two-layer control strategy is illustrated with a simulated case study of an industrial polymerization process. 相似文献
74.
Luis M. Torres Ramiro Torres Ralf Borndörfer Marc E. Pfetsch 《International Transactions in Operational Research》2011,18(4):455-472
We discuss an optimization model for the line planning problem in public transport in order to minimize operation costs while guaranteeing a certain level of quality of service, in terms of available transport capacity. We analyze the computational complexity of this problem for tree network topologies as well as several categories of line operations that are important for the Quito Trolebús system. In practice, these instances can be solved quite well, and significant optimization potentials can be demonstrated. 相似文献
75.
Wjatscheslaw Missal Jaroslaw KitaEberhard Wappler Frieder GoraAnnette Kipka Thomas BartnitzekFranz Bechtold Dirk SchabbelBeate Pawlowski Ralf Moos 《Sensors and actuators. A, Physical》2011,172(1):21-26
A miniaturized ceramic differential scanning calorimeter (MC-DSC) with integrated oven and crucible is presented. Despite its small size of only 11 mm × 39 mm × 1.5 mm, all functions of a conventional DSC apparatus are integrated in this novel device - including the oven. The MC-DSC is fully manufactured in thick-film and green glass ceramic tape-based low temperature co-fired ceramics (LTCC) technology. Therefore, production costs are considered to be low. Initial results using indium as a sample material show a good dynamic performance of the MC-DSC. Full width at half maximum of the melting peak is 2.4 °C (sample mass approx. 11 mg, heating rate approx. 50 °C/min). Repeatability of the indium melting point is within ±0.02 °C. The melting peak area increases linearly with the sample mass up to at least 26 mg. Simulations of a strongly simplified finite element model of the MC-DSC are in a good agreement with measurement results allowing a model-based prediction of its basic characteristics. 相似文献
76.
Daniela SchönauerAuthor VitaeIna SichertAuthor Vitae Ralf MoosAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(1):199-205
Urea-SCR systems (selective catalytic reduction) are required to meet future NOx emission standards of heavy-duty and light-duty vehicles. It is a key factor to control the SCR systems and to monitor the catalysts’ functionalities to achieve low emissions. The novel idea of this study is to apply commercially available SCR catalyst materials based on vanadia-doped tungsten-titania as gas sensing films for impedimetric thick-film exhaust gas sensor devices. The dependence of the impedance on the surrounding gas atmosphere, especially on the concentrations of NH3 and NO2, is investigated, as well as cross interferences from other components of the exhaust. The sensors provide a good NH3 sensitivity at 500 °C. The sensor behavior is explained in light of the literature combining the fields of catalysts and semiconducting gas sensors. 相似文献
77.
Physically Guided Animation of Trees 总被引:2,自引:0,他引:2
This paper presents a new method to animate the interaction of a tree with wind both realistically and in real time. The main idea is to combine statistical observations with physical properties in two major parts of tree animation. First, the interaction of a single branch with the forces applied to it is approximated by a novel efficient two step nonlinear deformation method, allowing arbitrary continuous deformations and circumventing the need to segment a branch to model its deformation behavior. Second, the interaction of wind with the dynamic system representing a tree is statistically modeled. By precomputing the response function of branches to turbulent wind in frequency space, the motion of a branch can be synthesized efficiently by sampling a 2D motion texture.
Using a hierarchical form of vertex displacement, both methods can be combined in a single vertex shader, fully leveraging the power of modern GPUs to realistically animate thousands of branches and ten thousands of leaves at practically no cost. 相似文献
Using a hierarchical form of vertex displacement, both methods can be combined in a single vertex shader, fully leveraging the power of modern GPUs to realistically animate thousands of branches and ten thousands of leaves at practically no cost. 相似文献
78.
Thomas Neumann Matthias Bender Sebastian Michel Ralf Schenkel Peter Triantafillou Gerhard Weikum 《Distributed and Parallel Databases》2009,26(1):3-27
Top-k query processing is a fundamental building block for efficient ranking in a large number of applications. Efficiency is a
central issue, especially for distributed settings, when the data is spread across different nodes in a network. This paper
introduces novel optimization methods for top-k aggregation queries in such distributed environments. The optimizations can be applied to all algorithms that fall into the
frameworks of the prior TPUT and KLEE methods. The optimizations address three degrees of freedom: 1) hierarchically grouping
input lists into top-k operator trees and optimizing the tree structure, 2) computing data-adaptive scan depths for different input sources, and
3) data-adaptive sampling of a small subset of input sources in scenarios with hundreds or thousands of query-relevant network
nodes. All optimizations are based on a statistical cost model that utilizes local synopses, e.g., in the form of histograms,
efficiently computed convolutions, and estimators based on order statistics. The paper presents comprehensive experiments,
with three different real-life datasets and using the ns-2 network simulator for a packet-level simulation of a large Internet-style
network. 相似文献
79.
Geno-mathematical identification of the multi-layer perceptron 总被引:1,自引:0,他引:1
Ralf Östermark 《Neural computing & applications》2009,18(4):331-344
In this paper, we will focus on the use of the three-layer backpropagation network in vector-valued time series estimation
problems. The neural network provides a framework for noncomplex calculations to solve the estimation problem, yet the search
for optimal or even feasible neural networks for stochastic processes is both time consuming and uncertain. The backpropagation
algorithm—written in strict ANSI C—has been implemented as a standalone support library for the genetic hybrid algorithm (GHA)
running on any sequential or parallel main frame computer. In order to cope with ill-conditioned time series problems, we
extended the original backpropagation algorithm to a K nearest neighbors algorithm (K-NARX), where the number K is determined genetically along with a set of key parameters. In the K-NARX algorithm, the terminal solution at instant t can be used as a starting point for the next t, which tends to stabilize the optimization process when dealing with autocorrelated time series vectors. This possibility
has proved to be especially useful in difficult time series problems. Following the prevailing research directions, we use
a genetic algorithm to determine optimal parameterizations for the network, including the lag structure for the nonlinear
vector time series system, the net structure with one or two hidden layers and the corresponding number of nodes, type of
activation function (currently the standard logistic sigmoid, a bipolar transformation, the hyperbolic tangent, an exponential
function and the sine function), the type of minimization algorithm, the number K of nearest neighbors in the K-NARX procedure, the initial value of the Levenberg–Marquardt damping parameter and the value of the neural learning (stabilization)
coefficient α. We have focused on a flexible structure allowing addition of, e.g., new minimization algorithms and activation
functions in the future. We demonstrate the power of the genetically trimmed K-NARX algorithm on a representative data set. 相似文献
80.
Achim Küpper Moritz Diehl Johannes P. Schlöder Hans Georg Bock Sebastian Engell 《Journal of Process Control》2009,19(5):785-802
In this paper, a moving horizon state and parameter estimation scheme for chromatographic simulated moving bed SMB processes is proposed. The simultaneous state and parameter estimation is based on a high-order nonlinear SMB model which incorporates rigorous models of the chromatographic columns and the discrete shiftings of the inlet and outlet ports. The estimation is performed using sparse measurement information: the concentrations of the components are only measured at the two outlet ports (which are periodically switched from one column to the next) and at one fixed location between two columns. The goal is to reconstruct the full state of the system, i.e. the concentration profiles along all columns, and to identify critical model parameters reliably such that the estimated model can be used in the context of online optimizing control. The state estimation scheme is based upon a deterministic model within the prediction horizon, state noise is only present in the state and the parameters prior to and at the beginning of the horizon. By solving the optimization problem with a multiple-shooting method and applying a real-time iteration scheme, the computation times are such that the scheme can be applied online. Numerical simulations of a validated model for a separation problem with nonlinear isotherms of the Langmuir type demonstrate the efficiency of the algorithm. 相似文献