全文获取类型
收费全文 | 1480篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 151篇 |
金属工艺 | 133篇 |
机械仪表 | 19篇 |
建筑科学 | 33篇 |
能源动力 | 25篇 |
轻工业 | 184篇 |
水利工程 | 8篇 |
石油天然气 | 6篇 |
无线电 | 164篇 |
一般工业技术 | 175篇 |
冶金工业 | 441篇 |
原子能技术 | 15篇 |
自动化技术 | 145篇 |
出版年
2021年 | 20篇 |
2020年 | 8篇 |
2019年 | 18篇 |
2018年 | 23篇 |
2017年 | 13篇 |
2016年 | 24篇 |
2015年 | 11篇 |
2014年 | 22篇 |
2013年 | 63篇 |
2012年 | 37篇 |
2011年 | 54篇 |
2010年 | 42篇 |
2009年 | 49篇 |
2008年 | 68篇 |
2007年 | 70篇 |
2006年 | 49篇 |
2005年 | 39篇 |
2004年 | 30篇 |
2003年 | 24篇 |
2002年 | 25篇 |
2001年 | 27篇 |
2000年 | 26篇 |
1999年 | 29篇 |
1998年 | 123篇 |
1997年 | 75篇 |
1996年 | 49篇 |
1995年 | 37篇 |
1994年 | 31篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 24篇 |
1990年 | 10篇 |
1989年 | 20篇 |
1988年 | 34篇 |
1987年 | 11篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 15篇 |
1977年 | 18篇 |
1976年 | 28篇 |
1975年 | 9篇 |
1974年 | 11篇 |
1971年 | 7篇 |
1970年 | 5篇 |
排序方式: 共有1506条查询结果,搜索用时 140 毫秒
31.
Tucker Balch 《Autonomous Robots》2000,8(3):209-238
As research expands in multiagent intelligent systems, investigators need new tools for evaluating the artificial societies they study. It is impossible, for example, to correlate heterogeneity with performance in multiagent robotics without a quantitative metric of diversity. Currently diversity is evaluated on a bipolar scale with systems classified as either heterogeneous or homogeneous, depending on whether any of the agents differ. Unfortunately, this labeling doesn't tell us much about the extent of diversity in heterogeneous teams. How can it be determined if one system is more or less diverse than another? Heterogeneity must be evaluated on a continuous scale to enable substantive comparisons between systems. To enable these types of comparisons, we introduce: (1) a continuous measure of robot behavioral difference, and (2) hierarchic social entropy, an application of Shannon's information entropy metric to robotic groups that provides a continuous, quantitative measure of robot team diversity. The metric captures important components of the meaning of diversity, including the number and size of behavioral groups in a society and the extent to which agents differ. The utility of the metrics is demonstrated in the experimental evaluation of multirobot soccer and multirobot foraging teams. 相似文献
32.
Steve Whittaker Simon Tucker Kumutha Swampillai Rachel Laban 《Personal and Ubiquitous Computing》2008,12(3):197-221
Although many recent systems have been built to support Information Capture and Retrieval (ICR), these have not generally
been successful. This paper presents studies that evaluate two different hypotheses for this failure, firstly that systems
fail to address user needs and secondly that they provide only rudimentary support for ICR. Having first presented a taxonomy
of different systems built to support ICR, we then describe a study that attempts to identify user needs for ICR. On the basis
of that study we carried out two user-oriented evaluations. In the first, we carried out a task-based evaluation of a state-of-the-art
ICR system, finding that it failed to provide users with abstract ways to view meetings data, and did not present users with
information categories that they considered to be important. In a second study, we introduce a new method for comparative
evaluation of different techniques for accessing meetings data. The second study showed that simple interface techniques that
extracted key information from meetings were effective in allowing users to extract gist from meetings data. We conclude with
a discussion of outstanding issues and future directions for ICR research. 相似文献
33.
Khan Z Balch T Dellaert F 《IEEE transactions on pattern analysis and machine intelligence》2006,28(12):1960-1972
In several multitarget tracking applications, a target may return more than one measurement per target and interacting targets may return multiple merged measurements between targets. Existing algorithms for tracking and data association, initially applied to radar tracking, do not adequately address these types of measurements. Here, we introduce a probabilistic model for interacting targets that addresses both types of measurements simultaneously. We provide an algorithm for approximate inference in this model using a Markov chain Monte Carlo (MCMC)-based auxiliary variable particle filter. We Rao-Blackwellize the Markov chain to eliminate sampling over the continuous state space of the targets. A major contribution of this work is the use of sparse least squares updating and downdating techniques, which significantly reduce the computational cost per iteration of the Markov chain. Also, when combined with a simple heuristic, they enable the algorithm to correctly focus computation on interacting targets. We include experimental results on a challenging simulation sequence. We test the accuracy of the algorithm using two sensor modalities, video, and laser range data. We also show the algorithm exhibits real time performance on a conventional PC 相似文献
34.
At press time, the details of the Clinton administration's healthcare reform package were not yet public. Some information has been leaked, however, fueling speculation about the plan's exact points. Computers in Healthcare asked three board members of the College of Healthcare Information Management Executives what they thought the Clinton healthcare team should know about the information piece of the puzzle. 相似文献
35.
John S. Lew 《Theory of Computing Systems》1978,12(1):253-270
Denoting the nonnegative (resp. signed) integers byN (resp.Z) and the real numbers byR, letK R
m
andf: R
m
R. Thenf is astoring function (resp.packing function) onK wheneverf|(Z
m
K) is an injection into (resp. bijection onto)N. Unit translations gm of some P. Chowla [1961] polynomials are packing functions on the correspondingN
m
, and all compositions of these polynomials yield further packing functions on variousN
r
. We study this accessible family of packing functions, using standard properties ofordered trees to classify all those compositions, up to a simple equivalence, which define polynomial packing functions on eachN
m
. The numberc(m) of equivalence classes is an exponentially growing function for largem, whence the uniqueness conjecture of our prior two-dimensional work has no counterpart for largerm. We obtain the admissible degrees for composition polynomials inm variables; we describe the tre structures for all such polynomials with extremal degrees. Them-variable polynomials of least degree form a rather irregular numbera(m) of equivalence classes. Density considerations give some degree constraints on ageneral polynomial packing function whose domainK is the topological closure of a nonvoid open cone. 相似文献
36.
Youssef Bokhabrine Ralph Seulin Lew F. C. Lew Yan Voon Patrick Gorria Gouenou Girardin Miguel Gomez Daniel Jobard 《Machine Vision and Applications》2012,23(3):417-425
During industrial forging of hot metallic shells, it is necessary to regularly measure the dimensions of the parts, especially
the inner and outer diameters and the thickness of the walls. A forging sequence lasts 2 h or more during which the diameter
of the shell is regularly measured in order to decide when to stop the forging process. For better working conditions, for
the safety of the blacksmiths, and for a faster and more accurate measurement, we have developed a novel system based on two
commercially available time of flight laser scanners for the measurement of the diameters of hot cylindrical metallic shells
during the forging process. The advantages of using laser scanners are that they can be placed very far from the hot shell,
more than 15 m, while at the same time giving an accurate point cloud from which three-dimensional views of the shell can
be reconstructed and diameter measurements done. Moreover, more accurate measurement is achieved in less time with the laser
system than with the conventional method using a large ruler. The system has been successfully used to measure the diameters
of hot cylindrical metallic shells. 相似文献
37.
For small, portable devices, speech input has the advantages of low-cost and small hardware, can be used on the move or whilst
the eyes & hands are busy, and is natural and quick. Rather than rely on imperfect speech recognition we propose that information
entered as speech is kept as speech and suitable tools are provided to allow quick and easy access to the speech-as-data records.
This paper summarises our work on the technologies needed for these tools – for organising, browsing, searching and compressing
the stored speech. These technologies go a long way towards giving stored speech the characteristics of text without the associated
input problems.
Received: 5 March 2002 / Accepted: 1 September 2002
Nick Haddock Consultant
Acknowledgements The authors would like to thank the whole HP Labs Gryphon team for their valuable contributions to this work - Mike Collins
for the hierarchical chunking algorithm, Erik Geelhoed and David Frohlich for the users perspective, Richard Hull for starting
off the compression work, Steve Loughran for productisation, and Dave Reynolds for his consistent advice and support. We would
also like to thank our partners at Cambridge University, Steve Young and Tony Robinson, whose expertise and technology formed
the foundation for this work, as well as the efforts of Kate Knill on wordspotting, Carl Seymour on compression, James Christie
on recognition, and Robin Valenza whose brief excursion into the world of speech technology helped develop a simple and effective
summarisation technique. Finally we would like to thank the reviewers for their many helpful comments. 相似文献
38.
We have observed that during temperature-dependent four-terminal resistance measurement of monolayer graphene, the resistance exhibits anomalous rising and falling behavior at different temperature regions. At lower temperature region (2–200 K) the resistance decreases gradually, but when the temperature rise further it turn to a sudden increase, and after 280 K it resumes gradual decrease. The rising and falling resistance behavior is characteristic of semiconductor or metal property. Consequently, the resistance transition follows a phase of semiconductor–metal–semiconductor. However, when a perpendicular magnetic field is applied, the resistance shows reverse transition behavior which follows a sequence of metal–semiconductor–metal. The novel transition property is attributed to the competition between the disorder of lattice defects as a short-range scattering in monolayer graphene and the Landau levels interaction. Magneto-transport measurement reveals that the excitonic gap induced by magnetic field in the monolayer graphene show an anomalous thermally activated property. 相似文献
39.
Franz B. Spingler Adam Phillips Tobias Schuler Michael C. Tucker Adam Z. Weber 《International Journal of Hydrogen Energy》2017,42(19):13960-13969
Reducing mass-transport losses in polymer-electrolyte fuel cells (PEFCs) is essential to increase their power density and reduce overall stack cost. At the same time, cost also motivates the reduction in expensive precious-metal catalysts, which results in higher local transport losses in the catalyst layers. In this paper, we use a hydrogen-pump limiting-current setup to explore the gas-phase transport losses through PEFC catalyst layers and various gas-diffusion and microporous layers. It is shown that the effective diffusivity in the gas-diffusion layers is a strong function of liquid saturation. In addition, it is shown how the catalyst layer unexpectedly contributes significantly to the overall measured transport resistance. This is especially true for low catalyst loadings. It is also shown how the various losses can be separated into different mechanisms including diffusional processes and mass-dependent and independent ones, where the data suggests that a large part of the transport resistance in catalyst layers cannot be attributed to a gas-phase diffusional process. The technique is promising for deconvoluting transport losses in PEFCs. 相似文献
40.
Amorn Chaiyasat Sirinard Jearanai Lew P Christopher Md Nur Alam 《Polymer International》2019,68(1):102-109
A novel process for the production of superabsorbent materials (hydrogels) from bacterial cellulose (BC) was developed. Prior to crosslinking with a water‐soluble polyethylene glycol diacrylate (PEGDA), BC was first carboxymethylated and functionalized with glycidyl methacrylate. The degree of crosslinking influenced the swelling properties of the hydrogels. The use of greater amounts of PEGDA enhanced the formation of a thicker macromolecular network containing fewer capillary spaces in the crosslinked gel. The maximum water retention value of the hydrogels containing 2.5–3.5 mmol of carboxyl groups per gram of gel reached 125 g g?1 in distilled water, and 29 g g?1 in saline (0.9% NaCl solution). The highly porous hydrogel architecture with a pore size of 350–600 µm created a high specific surface area. This enables rapid mass penetration in superabsorbent applications. The superabsorbent hydrogels reached 80% of their maximum water absorption capacity in 30 min. © 2018 Society of Chemical Industry 相似文献