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101.
Christian Liebchen Michael Schachtebeck Anita Schöbel Sebastian Stiller André Prigge 《Computers & Operations Research》2010,37(5):857-868
In the past, much research has been dedicated to compute optimum railway timetables. A typical objective has been the minimization of passenger waiting times. But only the planned nominal waiting times have been addressed, whereas delays as they occur in daily operations have been neglected. Delays have been rather treated mainly in an online context and solved as a separate optimization problem, called delay management.We provide the first computational study which aims at computing delay resistant periodic timetables. In particular we assess the delay resistance of a timetable by evaluating it subject to several delay scenarios to which optimum delay management will be applied.We arrive at computing delay resistant timetables by selecting a new objective function which we design to be somehow in the middle of the traditional simple timetabling objective and the sophisticated delay management objective. This is a slight extension of the concept of “light robustness” (LR) as it has been proposed by Fischetti and Monaci [2006. Robust optimization through branch-and-price. In: Proceedings of AIRO]. Moreover, in our application we are able to provide accurate interpretations for the ingredients of LR. We apply this new technique to real-world data of a part of the German railway network of Deutsche Bahn AG. Our computational results suggest that a significant decrease of passenger delays can be obtained at a relatively small price of robustness, i.e. by increasing the nominal travel times of the passengers. 相似文献
102.
Giorgos Sfikas Christophoros Nikou Nikolaos Galatsanos Christian Heinrich 《Journal of Mathematical Imaging and Vision》2010,36(2):91-110
Spatially varying mixture models are characterized by the dependence of their mixing proportions on location (contextual mixing proportions) and they have been widely used in image segmentation. In this work, Gauss-Markov random field (MRF) priors are employed
along with spatially varying mixture models to ensure the preservation of region boundaries in image segmentation. To preserve
region boundaries, two distinct models for a line process involved in the MRF prior are proposed. The first model considers
edge preservation by imposing a Bernoulli prior on the normally distributed local differences of the contextual mixing proportions. It is a discrete line process model whose parameters are computed by variational inference. The second model imposes Gamma
prior on the Student’s-t distributed local differences of the contextual mixing proportions. It is a continuous line process whose parameters are also automatically estimated by the Expectation-Maximization (EM) algorithm.
The proposed models are numerically evaluated and two important issues in image segmentation by mixture models are also investigated
and discussed: the constraints to be imposed on the contextual mixing proportions to be probability vectors and the MRF optimization
strategy in the frameworks of the standard and variational EM algorithm. 相似文献
103.
Christian Schuberth Peter Singerl Michael E. Gadringer Holger Arthaber Andreas Wiesbauer Gottfried Magerl 《国际射频与微波计算机辅助工程杂志》2010,20(4):446-457
This article presents a switched‐mode transmitter architecture using a current mode class‐D (CMCD) amplifier. To achieve high average efficiency for a modulated signal the envelope of the complex baseband signal is transformed into pulses such that the CMCD amplifier is operated either at its peak efficiency or completely switched off. The CMCD amplifier has been designed based on single‐tone active harmonic load‐pull measurements to achieve a power‐added efficiency (PAE) of 61.5% with 25 W output power at 900 MHz using LDMOS FETs. Removing the losses of the demodulation filter and of the amplifier a 10% higher efficiency than in an ideal class‐B amplifier can be obtained for burst‐mode operation with a peak‐to‐average power ratio of 10 dB. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. 相似文献
104.
Hop is a multi-tier programming language where the behavior of interacting servers and clients are expressed by a single program. Hop adheres to the standard web programming style where servers elaborate HTML pages containing JavaScript code. This JavaScript code responds locally to user’s interactions but also (following the so-called Ajax style) requests services from remote servers. These services bring back new HTML fragments containing additional JavaScript code replacing or modifying the state of the client. This paper presents a continuation-based denotational semantics for a sequential subset of Hop. Though restricted to a single server and a single client, this semantics takes into account the key feature of Hop namely that the server elaborates client code to be run in the client’s browser. This new client-code dynamically requests services from the server which, again, elaborate new client code to be run in the client’s browser. This semantics details the programming model advocated by Hop and provides a sound basis for future studies such as security of web applications and web continuations. 相似文献
105.
Claire M. Côte Chris J. Moran Christopher J. Hedemann Christian Koch 《Environmental Modelling & Software》2010,25(12):1664-1671
Concerns about the difficulties in securing water have led the Australian coal mining industry to seek innovative ways to improve its water management and to adopt novel strategies that will lead to less water being used and more water being reused. Simulation tools are essential to assess current water management performance and to predict the efficiency of potential strategies. As water systems on coal mines are complex and consist of various inter-connected elements, a systems approach was selected, which views mine site water management as a system that obtains water from various sources (surface, groundwater), provides sufficient water of suitable quality to the mining tasks (coal beneficiation, dust suppression, underground operations) and maintains environmental performance. In this paper, the model is described and its calibration is illustrated. The results of applying the model for the comparison of the water balances of 7 coal mines in the northern Bowen Basin (Queensland, Australia) are presented. The model is used to assess the impact of applying specific water management strategies. Results show that a simple systems model is an appropriate tool for assessing site performance, for providing guidance to improve performance through strategic planning, and for guiding adoption of site objectives. 相似文献
106.
Rajkumar Kannan Frederic Andres Christian Guetl 《Multimedia Tools and Applications》2010,46(2-3):545-572
A well-annotated dance media is an essential part of a nation’s identity, transcending cultural and language barriers. Many dance video archives suffer from problems concerning authoring and access, because of the complex spatio-temporal relationships that exist between the dancers in terms of movements of their body parts and the emotions expressed by them in a dance. This paper presents a system named DanVideo for semi-automatic authoring and access to dance archives. DanVideo provides methods of annotation and authoring and retrieval tools for choreographers, dancers, and students. We demonstrate how dance media can be semantically annotated and how this information can be used for the retrieval of the dance video semantics. In particular, DanVideo offers an MPEG-7 based semi-automatic authoring tool that takes dance video annotations generated by dance experts and produces MPEG-7 metadata. DanVideo also has a search engine that takes users’ queries and retrieves dance semantics from metadata arranged using tree-embedding technique and based on spatial, temporal and spatio-temporal features of dancers. The search engine also leverages a domain-specific ontology to process knowledge-based queries. We have assessed the dance-video queries and semantic annotations in terms of precision, recall, and fidelity. 相似文献
107.
One of congress’ goals for 2007 was for 80% of all tax and informational returns to be filed electronically. However, to date
that lofty goal has fallen well short. This research proposes a model of e-filing adoption. To test the model a survey is
administered to 260 participants. The instrument assesses citizen perceptions of trust, risk and optimism bias. Structural
equation modeling is used to evaluate the relationships between these three concepts and intention to use. The results indicate
that trust of the Internet, trust of the e-filer, perceived risk and optimism bias all have an impact on intention to use
e-filing. Implications for practice and research are discussed. 相似文献
108.
Making changes to software systems can prove costly and it remains a challenge to understand the factors that affect the costs
of software evolution. This study sought to identify such factors by investigating the effort expended by developers to perform
336 change tasks in two different software organizations. We quantitatively analyzed data from version control systems and
change trackers to identify factors that correlated with change effort. In-depth interviews with the developers about a subset
of the change tasks further refined the analysis. Two central quantitative results found that dispersion of changed code and
volatility of the requirements for the change task correlated with change effort. The analysis of the qualitative interviews
pointed to two important, underlying cost drivers: Difficulties in comprehending dispersed code and difficulties in anticipating
side effects of changes. This study demonstrates a novel method for combining qualitative and quantitative analysis to assess
cost drivers of software evolution. Given our findings, we propose improvements to practices and development tools to manage
and reduce the costs. 相似文献
109.
Dennis Heinson York Yannikos Frederik Franke Christian Winter Markus Schneider 《Datenschutz und Datensicherheit - DuD》2010,34(2):75-79
Der Einsatz von Informationstechnologie (IT) in Organisationen bietet viele M?glichkeiten des Missbrauchs. Besch?ftigte k?nnen
sich die besonderen Eigenschaften der IT zunutze machen, um sich etwa in gesch?ftssch?digender Weise Vorteile zu verschaffen.
Gleichzeitig erm?glicht IT aber auch, verbotene Handlungen aufzuspüren und zu belegen (IT-Forensik). Der Beitrag beschreibt
die technische Praxis von IT-forensischen Analysen und geht auf damit verbundene rechtliche Fragestellungen ein. 相似文献
110.
Jiang Wang Chunlei Liu Christian LeinenbachUlrich E. Klotz Peter J. UggowitzerJörg F. Löffler 《Calphad》2011,35(1):82-94
The Cu-Sn-Ti ternary system has been studied via experiments and thermodynamic modelling. In the experimental section, the composition of the alloys was selected based on the preliminary calculations and available literature data. Metallography, scanning electron microscopy and electron probe microanalysis were employed to analyse alloy samples prepared by arc-melting after annealing at 800 °C for 760 h. Solid phase relations at 800 °C were established. In contrast to earlier reports, the CuSn3Ti5 phase was interpreted as a binary intermetallic compound (Sn3Ti5) with extended Cu solubility. In the modelling section, three binary sub-systems were critically evaluated and updated according to the new experimental data and theoretical calculations reported in literature. According to their crystal structures and homogeneity ranges, appropriate sublattice models were proposed for SnTi3,SnTi2,Sn3Ti5 and Sn5Ti6. A set of self-consistent thermodynamic parameters for the Cu-Sn-Ti ternary system was obtained by considering the present experimental results and reported experimental information. The calculated results compare with the available experimental data to validate the present thermodynamic assessment. 相似文献