全文获取类型
收费全文 | 2567篇 |
免费 | 54篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 33篇 |
化学工业 | 339篇 |
金属工艺 | 31篇 |
机械仪表 | 21篇 |
建筑科学 | 39篇 |
矿业工程 | 2篇 |
能源动力 | 27篇 |
轻工业 | 255篇 |
水利工程 | 8篇 |
石油天然气 | 2篇 |
无线电 | 248篇 |
一般工业技术 | 373篇 |
冶金工业 | 954篇 |
原子能技术 | 33篇 |
自动化技术 | 258篇 |
出版年
2022年 | 29篇 |
2021年 | 35篇 |
2020年 | 21篇 |
2019年 | 25篇 |
2018年 | 36篇 |
2017年 | 32篇 |
2016年 | 35篇 |
2015年 | 23篇 |
2014年 | 39篇 |
2013年 | 116篇 |
2012年 | 62篇 |
2011年 | 84篇 |
2010年 | 57篇 |
2009年 | 72篇 |
2008年 | 81篇 |
2007年 | 51篇 |
2006年 | 71篇 |
2005年 | 66篇 |
2004年 | 37篇 |
2003年 | 49篇 |
2002年 | 42篇 |
2001年 | 54篇 |
2000年 | 42篇 |
1999年 | 60篇 |
1998年 | 233篇 |
1997年 | 160篇 |
1996年 | 114篇 |
1995年 | 76篇 |
1994年 | 69篇 |
1993年 | 81篇 |
1992年 | 54篇 |
1991年 | 25篇 |
1990年 | 32篇 |
1989年 | 30篇 |
1988年 | 37篇 |
1987年 | 33篇 |
1986年 | 32篇 |
1985年 | 35篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 28篇 |
1981年 | 22篇 |
1980年 | 21篇 |
1978年 | 24篇 |
1977年 | 24篇 |
1976年 | 46篇 |
1975年 | 29篇 |
1974年 | 16篇 |
1973年 | 16篇 |
1972年 | 15篇 |
排序方式: 共有2623条查询结果,搜索用时 15 毫秒
61.
62.
63.
We calculate the time-resolved flux of photons transmitted across an optically turbid slab containing a partially absorbing inclusion. An analytical expression is obtained for the flux at a detector positioned opposite a point source (at a distance equal to the thickness of the slab) when the center of the inclusion lies on the line connecting those points. The calculation employs a discrete-time lattice random-walk model of photon transport. The resulting expression is used to assess the affects of time resolution on the detectability of the inclusion. 相似文献
64.
Ulrich Schmatz Catherine Dubourdieu Oleg Lebedev Gerard Delabouglise Francois Weiss Jean-Pierre Senateur 《Journal of Low Temperature Physics》1996,105(5-6):1301-1306
Thin and thick YBCO Films have been grown by Aerosol Assisted as well as by thermal MOCVD. The Aerosol Assisted MOCVD technique allows the growth of YBCO films from a single liquid source at deposition rates of up to 10m/h.Transport measurements (I-V) on etched microbridges using a single pulse technique have been performed. The angular magnetic field dependence Jc() of the critical current density from Tc down to 50 K has been measured. Transport properties are reported and discussed with respect to the microstructural features as determined by X-ray diffraction and electron microscopy. 相似文献
65.
The SCOLE model is a coupled system consisting of a flexible beam (modelled as an Euler–Bernoulli equation) with one end clamped
and the other end linked to a rigid body. Its inputs are the force and the torque acting on the rigid body. It is well-known
that the SCOLE model is not exactly controllable with L
2 input signals in the natural energy state space H
c
, because the control operator is bounded from the input space
\mathbbC2{\mathbb{C}^2} to H
c
, and hence compact. We regard the velocity and the angular velocity of the rigid body as the output signals of this system.
Using the theory of coupled linear systems (one infinite-dimensional and one finite-dimensional) developed by us recently
in another paper, we show that the SCOLE model is well-posed, regular and exactly controllable in arbitrarily short time when
using a certain smoother state space X ì Hc{\mathcal{X}\subset H^c}. 相似文献
66.
Roland Schnaubelt George Weiss 《Mathematics of Control, Signals, and Systems (MCSS)》2010,21(4):265-301
We investigate two classes of time-varying well-posed linear systems. Starting from a time-invariant scattering-passive system,
each of the time-varying systems is constructed by introducing a time-dependent inner product on the state space and modifying
some of the generating operators. These classes of linear systems are motivated by physical examples such as the electromagnetic
field around a moving object. To prove the well-posedness of these systems, we use the Lax–Phillips semigroup induced by a
well-posed linear system, as in scattering theory. 相似文献
67.
We consider large volume job shop scheduling problems, in which there is a fixed number of machines, a bounded number of activities
per job, and a large number of jobs. In large volume job shops it makes sense to solve a fluid problem and to schedule the
jobs in such a way as to track the fluid solution. There have been several papers which used this idea to propose approximate
solutions which are asymptotically optimal as the volume increases. We survey some of these results here. In most of these
papers it is assumed that the problem consists of many identical copies of a fixed set of jobs. Our contribution in this paper
is to extend the results to the far more general situation in which the many jobs are all different. We propose a very simple
heuristic which can schedule such problems. We discuss asymptotic optimality of this heuristic, under a wide range of previously
unexplored situations. We provide a software package to explore the performance of our policy, and present extensive computational
evidence for its effectiveness. 相似文献
68.
Randy L. Hackbarth Audris Mockus John Douglas Palframan David M. Weiss 《Empirical Software Engineering》2010,15(3):219-249
To be relevant to the goals of an enterprise, an industrial software engineering research organization must identify problems
of interest to, and find solutions that have an impact on, the software development organizations within the company. Using
a systematic measurement program both to identify the problems and assess the impact of solutions is key to satisfying this
need. Avaya has had such a program in place for about seven years. Every year we produce an annual report known as the State
of Software in Avaya that describes software development trends throughout the company and that contains prioritized recommendations
for improving Avaya’s software development capabilities. We start by identifying the goals of the enterprise and use the goal-question-metric
approach to identify the measures to compute. The result is insight into the enterprise’s problems in software development,
recommendations for improving the development process, and problems that require research to solve. We will illustrate the
process with examples from the Software Technology Research Department in Avaya Labs whose purpose is to improve the state
of software development and know it. “Know it” means that improvement should be subjectively evident and objectively quantifiable.
“Know it” also means that one must be skilled at identifying the data sources, performing the appropriate analyses to answer
the questions of interest, and validating that the data are accurate and appropriate for the purpose. Examples will include
how and why we developed a measure of software quality that appeals to customers, how and why we are studying the effectiveness
of distributed software development, and how and why we are helping development organizations to adopt iterative development
methods. We will also discuss how we keep the company and the department apprised of the current strengths and weaknesses
of software development in Avaya through the publication of the annual State of Software in Avaya Report. Our purpose is both
to provide a model for assessment that others may emulate, based on seven years of experience, and to spotlight analyses and
conclusions that we feel are common to software development today. 相似文献
69.
Norman Weiss 《Robotics and Autonomous Systems》2009,57(10):982-995
One of the main tasks of mobile robotics is vision. Lighting independence, adaptivity and automated learning are still the main issues when it comes to applications. In this article, we present an image understanding system and its methods targeting automatic, lighting-independent and reliable color-based object recognition under real time conditions. Its application test bed is global vision robot soccer (i.e. FIRA MiroSot und RoboCup Small Size leagues) but it has many other applications in color-based supervision of moving objects. Under typical conditions, it learns the objects of recognition automatically, has zero setup time and tolerates environmental changes during run-time. 相似文献
70.
Christiane Jasmin Reinert‐Weiss Holger Baur Sheikh Abdullah Al Nusayer David Duhme Norbert Frühauf 《Journal of the Society for Information Display》2017,25(2):90-97
Conventional adaptive driving beam headlamps are limited in achieving still higher quantities of switchable pixels by the number of LEDs and movable elements needed. In this paper, it is shown that by integrating an active matrix liquid crystal display module, it is possible to realize fully adaptive high‐resolution headlights without mechanical elements and a finite number of LED with 30 k switchable pixels. 相似文献