全文获取类型
收费全文 | 16906篇 |
免费 | 1031篇 |
国内免费 | 1114篇 |
专业分类
电工技术 | 399篇 |
技术理论 | 1篇 |
综合类 | 979篇 |
化学工业 | 1117篇 |
金属工艺 | 397篇 |
机械仪表 | 1620篇 |
建筑科学 | 1193篇 |
矿业工程 | 239篇 |
能源动力 | 554篇 |
轻工业 | 269篇 |
水利工程 | 269篇 |
石油天然气 | 368篇 |
武器工业 | 106篇 |
无线电 | 1314篇 |
一般工业技术 | 723篇 |
冶金工业 | 377篇 |
原子能技术 | 122篇 |
自动化技术 | 9004篇 |
出版年
2024年 | 27篇 |
2023年 | 136篇 |
2022年 | 220篇 |
2021年 | 336篇 |
2020年 | 292篇 |
2019年 | 281篇 |
2018年 | 311篇 |
2017年 | 406篇 |
2016年 | 528篇 |
2015年 | 528篇 |
2014年 | 989篇 |
2013年 | 903篇 |
2012年 | 903篇 |
2011年 | 1340篇 |
2010年 | 902篇 |
2009年 | 932篇 |
2008年 | 1006篇 |
2007年 | 1181篇 |
2006年 | 1103篇 |
2005年 | 940篇 |
2004年 | 884篇 |
2003年 | 962篇 |
2002年 | 696篇 |
2001年 | 609篇 |
2000年 | 477篇 |
1999年 | 450篇 |
1998年 | 369篇 |
1997年 | 271篇 |
1996年 | 236篇 |
1995年 | 194篇 |
1994年 | 145篇 |
1993年 | 88篇 |
1992年 | 85篇 |
1991年 | 56篇 |
1990年 | 42篇 |
1989年 | 49篇 |
1988年 | 36篇 |
1987年 | 10篇 |
1986年 | 24篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1976年 | 4篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Enrico Tronci 《International Journal on Software Tools for Technology Transfer (STTT)》2006,8(4-5):355-358
In today’s competitive market designing of digital systems (hardware as well as software) faces tremendous challenges. In
fact, notwithstanding an ever decreasing project budget, time to market and product lifetime, designers are faced with an
ever increasing system complexity and customer expected quality. The above situation calls for better and better formal verification
techniques at all steps of the design flow. This special issue is devoted to publishing revised versions of contributions
first presented at the 12th Advanced Research Working Conference on Correct Hardware Design and Verification Methods (CHARME) held 21–24 October 2003 in L’Aquila, Italy. Authors of well regarded papers from CHARME’03 were invited to submit
to this special issue. All papers included here have been suitably extended and have undergone an independent round of reviewing. 相似文献
72.
Graham P. Gavin Garrett B. McGuinness Finbar Dolan M.S.J. Hashmi 《International Journal of Mechanical Sciences》2007,49(3):298-305
Therapeutic ultrasound angioplasty has been investigated, clinically, by a number of researchers and represents a potentially promising therapy for the treatment of atherosclerotic lesions. To date, there has been no detailed analysis of the effect of mechanical design parameters, such as wire geometry or damping characteristics, on wire waveguide performance. An apparatus capable of delivering therapeutic ultrasound down small diameter nickel–titanium (NiTi) wire waveguides is described. The output peak-to-peak (p–p) displacements at the distal tip of a 1.0 mm diameter waveguide were measured experimentally, by means of an optical microscope and image analysis software. The output was measured for a range of waveguide lengths from 118 to 303 mm. Wire waveguide distal tip displacements as high as 98 μm (p–p) at 23.5 kHz were measured. For the range of lengths tested, the experimental measurements show the critical relationship between the length of the waveguide and the output distal tip displacements. A finite element model that can predict the resonant frequencies and distal tip displacements of various wire waveguide geometries and configurations, including the effect of damping, is presented. This numerical model has been validated against the experimental displacement data obtained. This will be a valuable design tool for ensuring the safety and effectiveness of therapeutic ultrasound angioplasty procedures. 相似文献
73.
74.
Language-level support for object persistence frees programmers from having to confront a broad class of database issues from within their applications. By virtue of its metaobject protocol, CLOS is a language whose semantics can be tailored by individual programmers. We used the metaobject protocol to extend CLOS with support for object persistence. Our goal was to obtain a version of CLOS with persistence to which we could easily port a commercial geometric CAD modeling system. We describe the design and implementation of our persistence extension and highlight the strengths and weaknesses exhibited by the CLOS metaobject protocol during our experiment. For many aspects of the implementation we found that the metaobject protocol was ideal. In other cases we had to choose among paying a large performance penalty, extending the protocol, and bypassing the protocol by modifying the language implementation directly. 相似文献
75.
Gabriele Pannocchia Author Vitae Author Vitae Stephen J. Wright Author Vitae 《Automatica》2007,43(5):852-860
Partial enumeration (PE) is presented as a method for treating large, linear model predictive control applications that are out of reach with available MPC methods. PE uses both a table storage method and online optimization to achieve this goal. Versions of PE are shown to be closed-loop stable. PE is applied to an industrial example with more than 250 states, 32 inputs, and a 25-sample control horizon. The performance is less than 0.01% suboptimal, with average speedup factors in the range of 80-220, and worst-case speedups in the range of 4.9-39.2, compared to an existing MPC method. Small tables with only 25-200 entries were used to obtain this performance, while full enumeration is intractable for this example. 相似文献
76.
Oscar Díaz 《Data & Knowledge Engineering》1995,16(3):223-240
In semantic data models, abstract relationship (e.g. generalization, aggregation, etc.) semantics are defined, specifying how insertion, deletion and modification operations made at a higher level of abstraction can affect the objects abstracted over and vice versa. These semantics, also known as structural constraints, are expressed through so-called update rules. This perspective has been somewhat lost in most object-oriented systems, where user-defined relationships are supported as simple pointers and their semantics are embedded, distributed and replicated within the operations accessing these pointers. This paper inherits and extends the treatment of relationships found in semantic data models to behavioural object-oriented models by presenting an approach to uniformly capture the update rules for user-defined relationships. The stress is not on supporting relationships as first-class objects, but on describing their update rules (or operational semantics) through a set of constructors namely, reaction, anticipation, delegation and exception. The approach has been borne out by an implementation in an active object-oriented database system. 相似文献
77.
Isothermal melt spinning experiments have been conducted using two polyethylene melts of low density (LDPE) and high density
(HDPE) to produce steady state spinline profiles. The data revealed the threadline extensional viscosity exhibiting a contrasting
picture : extension thickening behavior for LDPE and extension thinning one for HDPE. A White-Metzner model having a strain
rate-dependent relaxation time was then found to be able to simulate this dichotomy in melt spinning fairly well: the fluids
whose relaxation times have smaller strain rate-dependence can fit LDPE data with extension thickening extensional viscosity
whereas the fluids whose relaxation times have larger strain rate-dependence can fit HDPE data with extension thinning extensional
viscosity. This dichotomous nature of viscoelastic fluids is also believed to be able to explain other similar contrasting
phenomena exhibited by polymer melts, such as vortex/no vortex in entry flows, cohesive/ductile fracture modes in extension,
and more/less stable draw resonance than Newtonian fluids. 相似文献
78.
In this study, current collecting efficiency of the micro tubular solid oxide fuel cell (SOFC) was estimated to determine optimum size of the micro tubular SOFC. Two models for collecting current from single terminal (ST) and double terminal (DT) of anode tube were proposed and used to calculate the current collecting efficiency as functions of anode thickness, tube length and operating temperature. It was shown that design of the cell geometry and current correcting method are significantly important to achieve high performance micro tubular SOFC stacks. The efficiency loss estimated from the DT model was about 2–4-fold lower than those of obtained from the ST model. The DT model was shown to be more effective for higher operating temperature and the tube length. 相似文献
79.
本文基于自回归滑动平均(ARMAX)控制模型的简要介绍,利用混合信号ISPFLASH微控制器技术,详细介绍了车辆行驶动态过程的空燃比自校正控制(STC)的硬件结构和软件配置及设计方法。 相似文献
80.
The research literature has seen a number of studies aimed at understanding customer attitudes towards banking technologies, and thereby providing implications for developmental planning and marketing. However, even though banking technologies have a significant amount of information systems (IS) component to them, there is a paucity of research that considers them from the IS perspective. In this paper, we fill this gap by considering three constructs, namely usefulness, ease of use and usage, that are all rooted in the IS literature. We study user’s perceptions of these constructs, as well as the relationships among them, for both online and telephone banking. 相似文献