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141.
The high yield strength and elastic modulus of metallic glasses suggests they could perform an important role in structural applications. To produce materials with a high strength-to-weight ratio and excellent mechanical energy absorption, it is advantageous to form amorphous alloys as cellular solids. Using the elastic properties of slip cast amorphous Fe45Ni45Mo7B3 ribbons, a metallic glass honeycomb was manufactured with a unique manufacturing approach. First, prototypes were manufactured with a porosity of 97?pct, a cell wall thickness of 0.03?mm, and a cell size of 3?mm. Experimentally measured mechanical properties were reasonably similar to analytical models. This suggests that a three-times improvement in the yield strength along the out-of-plane direction is achievable when compared with crystalline aluminum honeycombs. An analytical model was developed to predict the relative density and the compressive stress (?? 3 * ) in the out-of-plane (X 3) direction of the ??teardrop?? cellular structure. The predictions are validated by initial experimental results and compare well with existing analytical models for hexagonal cellular materials. 相似文献
142.
In applications where the quadtree is used as an underlying object representation, a number of basic operations are implemented as a trace along the border of the object's region. A technique is presented that determines a way to shift any given scene (as well as its quadtree), so that the border of all the objects in the scene can be traversed in time proportional to the length of all the borders in the scene (or the number of blocks when the scene is represented as a quadtree). This determination is shown to be performed in time proportional to the length of all the borders in the scene. This allows the direct translation of a number of chain-code algorithms into quadtree algorithms without loss of asymptotic worst-case efficiency. This results in improved worst-case analyses of algorithms that convert chain codes into quadtrees and that perform connected component labeling of images represented as quadtrees.The support of the National Science Foundation under Grant IRI-88-02457 is gratefully acknowledged. 相似文献
143.
Michael J. Katchabaw Hanan L. Lutfiyya Michael A. Bauer 《Computer Communications》2005,28(18):53-2159
It is often difficult to ensure that every application in a computing environment receives the level of quality of service required by their users. In such cases, the demand for computing resources to do so simply exceeds the limited supply that is available. To ensure that at least some user applications meet quality of service requirements, service differentiation is one approach growing in popularity. In this approach, preferential service is given to selected applications, while others deemed less important suffer in comparison. Most work in this area bases service differentiation decisions on static information about the applications, such as the name and type of application, the owner of the application, execution time, and the host on which the application was executed. In this paper, we discuss a new approach to service differentiation that takes into consideration dynamic application usage information in service differentiation decisions. In doing so, we can make better or fairer service differentiation decisions that allow more users to enjoy higher levels of quality of service. This is accomplished by ensuring preferential service is given to applications whose users can actually benefit from the improved service, as opposed to those applications that are essentially ignored or in a state that renders them unusable. 相似文献
144.
Speeding up construction of PMR quadtree-based spatial indexes 总被引:5,自引:0,他引:5
Gisli R. Hjaltason Hanan Samet 《The VLDB Journal The International Journal on Very Large Data Bases》2002,11(2):109-137
Spatial indexes, such as those based on the quadtree, are important in spatial databases for efficient execution of queries
involving spatial constraints, especially when the queries involve spatial joins. In this paper we present a number of techniques
for speeding up the construction of quadtree-based spatial indexes, specifically the PMR quadtree, which can index arbitrary
spatial data. We assume a quadtree implementation using the “linear quadtree”, a disk-resident representation that stores
objects contained in the leaf nodes of the quadtree in a linear index (e.g., a B-tree) ordered based on a space-filling curve.
We present two complementary techniques: an improved insertion algorithm and a bulk-loading method. The bulk-loading method
can be extended to handle bulk-insertions into an existing PMR quadtree. We make some analytical observations about the I/O
cost and CPU cost of our PMR quadtree bulk-loading algorithm, and conduct an extensive empirical study of the techniques presented
in the paper. Our techniques are found to yield significant speedup compared to traditional quadtree building methods, even
when the size of a main memory buffer is very small compared to the size of the resulting quadtrees.
Edited by R. Sacks-Davis. Received: July 10, 2001 / Accepted: March 25, 2002 Published online: September 25, 2002 相似文献
145.
Hanan Luss 《IIE Transactions》1977,9(2):189-194
Inspection policy models deal with stochastically failing systems in which failures are detected by inspections only. In this paper we examine a model for a system which is inoperative during the inspection periods. This problem is important in situations where inspections demand a considerable amount of time, such as the inspection of production machines, inspection of communication systems, aircraft maintenance, etc. The costs incurred include the cost of inspections, the cost per time unit of unobserved breakdowns, and the cost of repairing (or replacing) the failed system. The objective is to minimize the expected total cost per time unit. Minimization of the system's unavailability is obtained as a special case by appropriate substitutions. 相似文献
146.
147.
Cross-linked chitosan sponges as controlled release drug carrier systems were developed. Tramadol hydrochloride, a centrally acting analgesic, was used as a model drug. The sponges were prepared by freeze-drying 1.25% and 2.5% (w/w) high and low M.wt. chitosan solutions, respectively, using glutaraldehyde as a cross-linking agent. The hardness of the prepared sponges was a function of glutaraldehyde concentration and volume where the optimum concentration that offered accepted sponge consistency was 5%. Below or above 5%, very soft or very hard and brittle sponges were obtained, respectively. The determined drug content in the prepared sponges was uniform and did not deviate markedly from the calculated amount. Scanning electron microscopy (SEM) was used to characterize the internal structures of the sponges. The SEM photos revealed that cross-linked high M.wt. chitosan sponges have larger size surface pores that form connections (channels) with the interior of the sponge than cross-linked low M.wt. ones. Moreover, crystals of the incorporated Tramadol hydrochloride were detected on the lamellae and within pores in both chitosan sponges. Differences in pore size and dissolution medium uptake capacity were crucial factors for the more delayed drug release from cross-linked low M.wt. chitosan sponges over high M.wt. ones at pH 7.4. Kinetic analysis of the release data using linear regression followed the Higuchi diffusion model over 12 hours. Setting storage conditions at room temperature under 80-92% relative humidity resulted in soft, elastic, and compressible sponges. 相似文献
148.
Using a distributed quadtree index in peer-to-peer networks 总被引:6,自引:0,他引:6
Egemen Tanin Aaron Harwood Hanan Samet 《The VLDB Journal The International Journal on Very Large Data Bases》2007,16(2):165-178
Peer-to-peer (P2P) networks have become a powerful means for online data exchange. Currently, users are primarily utilizing
these networks to perform exact-match queries and retrieve complete files. However, future more data intensive applications,
such as P2P auction networks, P2P job-search networks, P2P multiplayer games, will require the capability to respond to more
complex queries such as range queries involving numerous data types including those that have a spatial component. In this
paper, a distributed quadtree index that adapts the MX-CIF quadtree is described that enables more powerful accesses to data
in P2P networks. This index has been implemented for various prototype P2P applications and results of experiments are presented.
Our index is easy to use, scalable, and exhibits good load-balancing properties. Similar indices can be constructed for various
multidimensional data types with both spatial and non-spatial components. 相似文献
149.
Yasser Saleh Hanan Ahmed Wahba Hend Ahmed El-Hadaad Mohamed Al-Hemaly Tamer Fady Youssef 《Canadian Metallurgical Quarterly》2011,10(8)
Objective: Despite resection with curative intent, a majority of patients with gastric cancer will develop disease recurrence. Postoperative adjuvant chemo-radiotherapy increase the curability of surgery, prevent local recurrence and improve survival. Methods: Between December 2005 and February 2010, 33 patients were eligible for the study, 17 patients were randomly assigned for chemo-radiotherapy (GI) and 16 patients with surgery alone (GII). Patients in GI received chemotherapy (fluorouracil, 425 mg/m2/day, and leucovorin, 20 mg/m2/day, for 5 days) was initiated on day 1 and was followed by chemo-radiotherapy beginning 28 days after the start of the initial cycle of chemotherapy. Chemo-radiotherapy consisted of 4500 cGy of radiation at 180 cGy/day, five days/week for five weeks, with fluorouracil (400 mg/m2/day) and leucovorin (20 mg/m2/day) on the first four and the last four days of radiotherapy. One month after the completion of radiotherapy, two five-day cycles of fluorouracil (425 mg/m2/day) plus leucovorin (20 mg/m2/day) were given one month apart. Results: Grade 3 gastrointestinal toxicity was more common (23.2%) while grade 3 hematological toxicity were (5.8%). Both 3-year survival (53%) and disease free survival (41%) rates were higher in GI than in GII in which they were 43.7% and 31% respectively. Relapse rate was higher in GII (56.3%) than in GI (35.3%). Conclusion: The present study revealed that chemo-radiotherapy after gastric resection in patients with gastric adenocarcinoma improves survival and relapse rates with manageable toxicities. However, studies with larger number of patients are recommended to confirm our results. 相似文献