全文获取类型
收费全文 | 615篇 |
免费 | 53篇 |
国内免费 | 46篇 |
专业分类
电工技术 | 12篇 |
综合类 | 36篇 |
化学工业 | 31篇 |
金属工艺 | 2篇 |
机械仪表 | 16篇 |
建筑科学 | 29篇 |
矿业工程 | 5篇 |
能源动力 | 9篇 |
轻工业 | 19篇 |
水利工程 | 33篇 |
石油天然气 | 4篇 |
武器工业 | 4篇 |
无线电 | 46篇 |
一般工业技术 | 27篇 |
冶金工业 | 34篇 |
原子能技术 | 1篇 |
自动化技术 | 406篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 15篇 |
2016年 | 11篇 |
2015年 | 20篇 |
2014年 | 29篇 |
2013年 | 33篇 |
2012年 | 36篇 |
2011年 | 45篇 |
2010年 | 26篇 |
2009年 | 38篇 |
2008年 | 44篇 |
2007年 | 43篇 |
2006年 | 61篇 |
2005年 | 37篇 |
2004年 | 22篇 |
2003年 | 32篇 |
2002年 | 20篇 |
2001年 | 20篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 18篇 |
1997年 | 15篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1975年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有714条查询结果,搜索用时 15 毫秒
61.
A universal method to prepare proton exchange membrane (PEM) with semi-interpenetrating polymer network (semi-IPN) via a versatile crosslinker 1,3-benzenedisulfonyl azide (1,3-BDSA) is proposed. Sulfonyl azide groups can react with any polymer with carbon-hydrogen bonds via hydrogen abstraction. Polyvinylidene fluoride (PVDF) and perfluorosulfonic acid (PFSA) polymer are selected as two precursors for semi-IPN. When 1,3-BDSA is heated to a sufficiently high temperature it can form the nitrene and connect with PVDF via hydrogen abstraction reaction, recombination, or CH-bond insertion. The crosslinking structure of PVDF is formed, and semi-IPN is constructed in the presence of PFSA at the same time. The mechanical properties, degree of crosslinking, water uptake, and proton conductivity of semi-IPN membranes are investigated. Compared with pure PFSA membrane, the mechanical properties and the dimensional stability of the semi-IPN membranes are improved significantly. The tensile strength of the composite membrane (27.2 MPa) is much higher than that of PFSA membrane (10.1 MPa). The maximum power density of the composite membrane can reach 382 mW cm−2 at 940 mA cm−2. Sulfonyl azide based crosslinkers can be used to prepare semi-IPN or IPN PEMs from any paired polymers with carbon–hydrogen bonds. 相似文献
62.
Antoine Debuigne Marie HurtgenChristophe Detrembleur Christine JérômeChristopher Barner-Kowollik Thomas Junkers 《Progress in Polymer Science》2012,37(7):1004-1030
The current review focuses on the relevance and practical benefit of interpolymer radical coupling methods. The latter are developing rapidly and constitute a perfectly complementary macromolecular engineering toolbox to the controlled radical polymerization techniques (CRP). Indeed, all structures formed by CRP are likely to be prone to radical coupling reactions, which multiply the available synthetic possibilities. Basically, the coupling systems can be divided in two main categories. The first one, including the atom transfer radical coupling (ATRC), silane radical atom abstraction (SRAA) and cobalt-mediated radical coupling (CMRC), relies on the recombination of macroradicals produced from a dormant species. The second one, including atom transfer nitroxide radical coupling (ATNRC), single electron transfer nitroxide radical coupling (SETNRC), enhanced spin capturing polymerization (ESCP) and nitrone/nitroso mediated radical coupling (NMRC), makes use of a radical scavenger in order to promote the conjugation of the polymer chains. More than a compilation of macromolecular engineering achievements, the present review additionally aims to emphasize the particularities, synthetic potential and present limitations of each system. 相似文献
63.
Environment-related authorisations are a relevant issue for environmental management. They require a considerable effort by the authorities, and this might result in substantial delays for the citizens. Implementing those authorisation processes by means of e-government services would improve efficiency and, consequently, citizen satisfaction. Environment-related authorisations usually require a variety of geospatial information, and have to deal with administrative areas which do not match physical and ecological ones. They also have to integrate heterogeneous information in different formats, data models and languages, and provided by distinct organisations, even from different countries. This paper discusses how Spatial Data Infrastructures (SDIs) can deal with these problems in the environmental domain, while improving the level of service provision in terms of e-government applications. This is even more relevant within the European Union where there is a legal mandate to establish an SDI to support environmental policies and activities with an impact on the environment. As a proof-of-concept, an application to request and manage water abstraction authorisations, based on an SDI, is demonstrated. This application is part of SDIGER, a cross-border inter-administration SDI to support the water framework directive information access for the Adour–Garonne and Ebro River basins, that was a pilot project for the EU INSPIRE Directive. The introduction of this transactional e-government service modifies the administrative process of granting authorisations: it allows to re-use the effort in data capture made by the applicants in their requests, facilitates the submission of more feasible applications and reduces the workload of the office staff. 相似文献
64.
Hierarchical mesh segmentation based on fitting primitives 总被引:11,自引:0,他引:11
In this paper, we describe a hierarchical face clustering algorithm for triangle meshes based on fitting primitives belonging
to an arbitrary set. The method proposed is completely automatic, and generates a binary tree of clusters, each of which is
fitted by one of the primitives employed. Initially, each triangle represents a single cluster; at every iteration, all the
pairs of adjacent clusters are considered, and the one that can be better approximated by one of the primitives forms a new
single cluster. The approximation error is evaluated using the same metric for all the primitives, so that it makes sense
to choose which is the most suitable primitive to approximate the set of triangles in a cluster.
Based on this approach, we have implemented a prototype that uses planes, spheres and cylinders, and have experimented that
for meshes made of 100 K faces, the whole binary tree of clusters can be built in about 8 s on a standard PC.
The framework described here has natural application in reverse engineering processes, but it has also been tested for surface
denoising, feature recovery and character skinning. 相似文献
65.
Sagar Chaki Edmund Clarke Joël Ouaknine Natasha Sharygina Nishant Sinha 《Formal Aspects of Computing》2005,17(4):461-483
We present a framework for model checking concurrent software systems which incorporates both states and events. Contrary
to other state/event approaches, our work also integrates two powerful verification techniques, counterexample-guided abstraction
refinement and compositional reasoning. Our specification language is a state/event extension of linear temporal logic, and
allows us to express many properties of software in a concise and intuitive manner. We show how standard automata-theoretic
LTL model checking algorithms can be ported to our framework at no extra cost, enabling us to directly benefit from the large
body of research on efficient LTL verification.
We also present an algorithm to detect deadlocks in concurrent message-passing programs. Deadlock- freedom is not only an
important and desirable property in its own right, but is also a prerequisite for the soundness of our model checking algorithm.
Even though deadlock is inherently non-compositional and is not preserved by classical abstractions, our iterative algorithm
employs both (non-standard) abstractions and compositional reasoning to alleviate the state-space explosion problem. The resulting
framework differs in key respects from other instances of the counterexample-guided abstraction refinement paradigm found
in the literature.
We have implemented this work in the magic verification tool for concurrent C programs and performed tests on a broad set
of benchmarks. Our experiments show that this new approach not only eases the writing of specifications, but also yields important
gains both in space and in time during verification. In certain cases, we even encountered specifications that could not be
verified using traditional pure event-based or state-based approaches, but became tractable within our state/event framework.
We also recorded substantial reductions in time and memory consumption when performing deadlock-freedom checks with our new
abstractions. Finally, we report two bugs (including a deadlock) in the source code of Micro-C/OS versions 2.0 and 2.7, which
we discovered during our experiments.
This research was sponsored by the National Science Foundation (NSF) under grants no. CCR-9803774 and CCR-0121547, the Office
of Naval Research (ONR) and the Naval Research Laboratory (NRL) under contract no. N00014-01-1-0796, the Army Research Office
(ARO) under contract no. DAAD19-01-1-0485, and was conducted as part of the Predictable Assembly from Certifiable Components
(PACC) project at the Software Engineering Institute (SEI).
This article combines and builds upon the papers (CCO+04) and (CCOS04).
Received December 2004
Revised July 2005
Accepted July 2005 by Eerke A. Boiten, John Derrick, Graeme Smith and Ian Hayes 相似文献
66.
彭泽华 《数字社区&智能家居》2006,(11)
视频摘要是对视频内容的一个简短的小结。本文介绍的视频摘要的基本概念、视频摘要的分类,并重点介绍了每一类视频摘要实现的关键技术。最后对目前的视频摘要技术作了小结,并展望了今后的发展方向。 相似文献
67.
Murray Stokely Sagar Chaki Joël Ouaknine 《Electronic Notes in Theoretical Computer Science》2006,157(1):77
In this paper we investigate how formal software verification systems can be improved by utilising parallel assignment in weakest precondition computations.We begin with an introduction to modern software verification systems. Specifically, we review the method in which software abstractions are built using counterexample-guided abstraction refinement (CEGAR). The classical NP-complete parallel assignment problem is first posed, and then an additional restriction is added to create a special case in which the problem is tractable with an O(n2) algorithm. The parallel assignment problem is then discussed in the context of weakest precondition computations. In this special situation where statements can be assumed to execute truly concurrently, we show that any sequence of simple assignment statements without function calls can be transformed into an equivalent parallel assignment block.Results of compressing assignment statements into a parallel form with this algorithm are presented for a wide variety of software applications. The proposed algorithms were implemented in the ComFoRT reasoning framework [J. Ivers and N. Sharygina. Overview of ComFoRT: A model checking reasoning framework. Technical Report CMU/SEI-2004-TN-018, Carnegie Mellon Software Engineering Institute, 2004] and used to measure the improvement in the verification of real software systems. This improvement in time proved to be significant for many classes of software. 相似文献
68.
对地产海鱼加工下脚料之一——鱼白中核酸的提取方法、产品纯度测定和组分鉴定方法进行了一些探索。结果显示,DNA粗产物得率为4.62%,DNA质量分数为4.77%。RNA粗产物得率为1.98%,RNA质量分数为4.06%,提取方法基本可行。 相似文献
69.
本文报导了三-三苯基膦氧化钴(I)与过量的异硫氰酸苯酯反应,依据快原子轰击质谱(FAB-MS),证实生成物的结构为四员钴杂环配合物。该配合物不稳定,容易脱硫,生成苯基异腈钴(Ⅱ)配合物。 相似文献
70.
介绍了新型硬件描述语言VHDL的发展及特点;分析了该语言中的3大结构模型,即性能状态、定时、结构化模型;讨论了贯穿语言始终的2个核心-进程和信号;给出了几例具体的电路描述实例。 相似文献