全文获取类型
收费全文 | 5709篇 |
免费 | 219篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 75篇 |
综合类 | 4篇 |
化学工业 | 1362篇 |
金属工艺 | 91篇 |
机械仪表 | 137篇 |
建筑科学 | 246篇 |
矿业工程 | 8篇 |
能源动力 | 246篇 |
轻工业 | 414篇 |
水利工程 | 34篇 |
石油天然气 | 19篇 |
无线电 | 680篇 |
一般工业技术 | 981篇 |
冶金工业 | 609篇 |
原子能技术 | 67篇 |
自动化技术 | 965篇 |
出版年
2023年 | 23篇 |
2022年 | 71篇 |
2021年 | 120篇 |
2020年 | 74篇 |
2019年 | 100篇 |
2018年 | 117篇 |
2017年 | 143篇 |
2016年 | 159篇 |
2015年 | 108篇 |
2014年 | 155篇 |
2013年 | 318篇 |
2012年 | 248篇 |
2011年 | 303篇 |
2010年 | 250篇 |
2009年 | 247篇 |
2008年 | 229篇 |
2007年 | 239篇 |
2006年 | 242篇 |
2005年 | 177篇 |
2004年 | 185篇 |
2003年 | 153篇 |
2002年 | 153篇 |
2001年 | 113篇 |
2000年 | 109篇 |
1999年 | 89篇 |
1998年 | 180篇 |
1997年 | 148篇 |
1996年 | 123篇 |
1995年 | 121篇 |
1994年 | 106篇 |
1993年 | 94篇 |
1992年 | 63篇 |
1991年 | 47篇 |
1990年 | 56篇 |
1989年 | 51篇 |
1988年 | 50篇 |
1987年 | 47篇 |
1986年 | 29篇 |
1985年 | 82篇 |
1984年 | 58篇 |
1983年 | 56篇 |
1982年 | 51篇 |
1981年 | 83篇 |
1980年 | 48篇 |
1979年 | 52篇 |
1977年 | 39篇 |
1976年 | 46篇 |
1975年 | 41篇 |
1974年 | 31篇 |
1973年 | 26篇 |
排序方式: 共有5938条查询结果,搜索用时 15 毫秒
151.
Masoud Baghelani Habib Badri Ghavifekr Afshin Ebrahimi 《Microsystem Technologies》2011,17(10-11):1599-1609
One of the most encumbering issues in RF MEMS resonators is spurious modes. The problem of spurious modes becomes more critical, when the ring type resonators are used. In the ring shape anchored contour mode disk resonator, for achieving a low serial resistance, the inner radius of the disk must be increased. This causes the spurious modes to become too close to the desired mode and degrade the operation of the resonator. In this work, spurious modes of before-mentioned device are introduced and their characteristics are evaluated by exact analytical approach. Based on those analytical approaches, we introduce two techniques for spurious mode suppression. The first technique is based on exciting the desired mode by proper electrode engineering and hence is an electrical approach. The second technique is reconfiguring of the anchor from a continuous ring to crossed ring segments and locating the segments on the phase discriminating lines to increase the insertion loss for spurious modes and decrease the losses for the fundamental mode. The final harmonic analysis verifies that the proposed techniques result a resonator with a pure frequency spectrum and spurious modes excluded over a very wide frequency range. 相似文献
152.
Souleiman Naciri Naoufel Cheikhrouhou Michel Pouly Jean-Charles Binggeli Rémy Glardon 《Expert systems with applications》2011,38(2):1203-1212
Nowadays, all product life cycle processes are investigated deeply in order to get an advantage over competitors. To support these processes, several software applications are available. However, this wide range of heterogeneous applications leads to a large variety of hardware and operating systems, data management software, data models, schemas, and data semantics that hinder the information sharing process. To tackle this problem, Hitachi Company has developed a modeling language called Generic Product Model (GPM) in addition to several translators from native formats to GPM for storing, sharing and visualizing product data in a single data warehouse. In order to broaden the range of application data able to be stored and shared using the GPM data warehouse, this paper presents a methodology and a translator that allow management data to be included in a GPM data warehouse. Given the fact that most management data are stored in Enterprise Resource Planning (ERP) software, and that the latter allows extraction of database contents into Excel files, we propose a translator that handles Enterprise Resource Planning management data that are already extracted into Excel Format.The proposed framework enables data management contained in flat Excel Files to be translated into structured GPM data. Translation methodologies are given for the translation of mass production and customized product data through two case studies, one in the computer retail sector and the other in the extrusion machine industry. 相似文献
153.
Peer-to-peer (P2P) networks are beginning to form the infrastructure of future applications. Computers are organized in P2P overlay networks to facilitate search queries with reasonable cost. So, scalability is a major aim in design of P2P networks. In this paper, to obtain a high factor of scalability, we partition network search space using a consistent static shared upper ontology. We name our approach semantic partition tree (SPT). All resources and queries are annotated using the upper ontology and queries are semantically routed in the overlay network. Also, each node indexes addresses of other nodes that possess contents expressible by the concept it maintains. So, our approach can be conceived as an ontology-based distributed hash table (DHT). Also, we introduce a lookup service for the network which is very scalable and independent of the network size and just depends on depth of the ontology tree. Further, we introduce a broadcast algorithm on the network. We present worst case analysis of both lookup and broadcast algorithms and measure their performance using simulation. The results show that our scheme is highly scalable and can be used in real P2P applications. 相似文献
154.
This paper describes an efficient Web page detection approach based on restricting the similarity computations between two
versions of a given Web page to the nodes with the same HTML tag type. Before performing the similarity computations, the
HTML Web page is transformed into an XML-like structure in which a node corresponds to an open-closed HTML tag. Analytical
expressions and supporting experimental results are used to quantify the improvements that are made when comparing the proposed
approach to the traditional one, which computes the similarities across all nodes of both pages. It is shown that the improvements
are highly dependent on the diversity of tags in the page. That is, the more diverse the page is (i.e., contains mixed content
of text, images, links, etc.), the greater the improvements are, while the more uniform it is, the lesser they are. 相似文献
155.
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
156.
Interlayer cooling potential in vertically integrated packages 总被引:2,自引:1,他引:1
T. Brunschwiler B. Michel H. Rothuizen U. Kloter B. Wunderle H. Oppermann H. Reichl 《Microsystem Technologies》2009,15(1):57-74
The heat-removal capability of area-interconnect-compatible interlayer cooling in vertically integrated, high-performance chip stacks was characterized with de-ionized water as coolant. Correlation-based predictions and computational fluid dynamic modeling of cross-flow heat-removal structures show that the coolant temperature increase due to sensible heat absorption limits the cooling performance at hydraulic diameters ≤200 μm. An experimental investigation with uniform and double-side heat flux at Reynolds numbers ≤1,000 and heat transfer areas of 1 cm2 was carried out to identify the most efficient interlayer heat-removal structure. The following structures were tested: parallel plate, microchannel, pin fin, and their combinations with pins using in-line and staggered configurations with round and drop-like shapes at pitches ranging from 50 to 200 μm and fluid structure heights of 100–200 μm. A hydrodynamic flow regime transition responsible for a local junction temperature minimum was observed for pin fin in-line structures. The experimental data was extrapolated to predict maximal heat flux in chip stacks having a 4-cm2 heat transfer area. The performance of interlayer cooling strongly depends on this parameter, and drops from >200 W/cm2 at 1 cm2 and >50 μm interconnect pitch to <100 W/cm2 at 4 cm2. From experimental data, friction factor and Nusselt number correlations were derived for pin fin in-line and staggered structures. 相似文献
157.
Optimal assembly plan generation: a simplifying approach 总被引:3,自引:0,他引:3
The main difficulty in the overall process of optimal assembly plan generation is the great number of different ways to assemble
a product (typically thousands of solutions). This problem confines the application of most existing automated planning methods
to products composed of only a limited number of components. The presented method of assembly plan generation belongs to the
approach called “disassembly” and is founded on a new representation of the assembly process, with introduction of a new concept,
the equivalence of binary trees. This representation allows to generate the minimal list of all non-redundant (really different) assembly plans. Plan generation is directed by assembly operation constraints and plan-level performance
criteria. The method was tested for various assembly applications and compared to other generation approaches. Results show
a great reduction in the combinatorial explosion of the number of plans. Therefore, this simplifying approach of assembly
sequence modeling allows to handle more complex products with a large number of parts. 相似文献
158.
159.
160.
Zeming Lu Fusaomi Nagata Keigo Watanabe Maki K. Habib 《Artificial Life and Robotics》2017,22(3):374-379
With the progress of electronics technology, the development of civilian UAV (unmanned aerial vehicle) applications becomes possible. In addition, smartphones have rapidly gained popularity and become very important due to the simple operability and mobility. Hence, there is a need to have an easy and flexible way to control a UAV using such technology. In this study, a remote controller using an iOS device is developed for a quadrotor to enable remote control with easy operations. Four basic programs for obtaining compass information, controlling a gimbal, autopilot function for return, and video preview function are developed and implemented for an iOS device. The basic functionalities of the programs are evaluated and confirmed through experiments using a quadrotor and an iOS device. 相似文献