全文获取类型
收费全文 | 252篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 48篇 |
金属工艺 | 1篇 |
机械仪表 | 2篇 |
建筑科学 | 5篇 |
能源动力 | 6篇 |
轻工业 | 13篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 31篇 |
一般工业技术 | 26篇 |
冶金工业 | 42篇 |
自动化技术 | 81篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 7篇 |
2013年 | 14篇 |
2012年 | 9篇 |
2011年 | 10篇 |
2010年 | 5篇 |
2009年 | 16篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 12篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有263条查询结果,搜索用时 15 毫秒
181.
The effects of solution ionic strength on the collision efficiency (alpha) distribution of a Sphingomonas sp. were investigated using multiple sand columns of varying lengths and analyzing the bacteria clean-bed breakthrough concentrations using a distributed colloid filtration theory (D-CFT). Five different probability density functions (PDFs) were investigated and all accurately replicated the lab-scale experimental data, whereas a single alpha value could not. The alpha distribution shifted toward smaller values with decreasing ionic strength and the PDF parameters were strongly correlated to the Debye length, indicating that electrostatic interactions had a direct impact on the alpha distribution. The results indicate that while ionic strength has a large impact on bacterial transport distances for a concentration reduction of a few orders of magnitude, as occurs at the laboratory scale, due to the distributed nature of the collision efficiency, it has a minor effect on predicted transport distances required to achieve concentration reductions on the order of 10(6), which occurs at the field scale. Because of this, bacterial inactivation (e.g., death), rather than physically removing the bacteria from solution via filtration, is likely the key process impacting the transport of viable bacteria at the field scale. Overall, for systems with a distributed alpha, the results indicate that ionic strength has a strong influence on the transport of bacteria at the lab-scale (centimeters to one meter), both ionic strength and bacterial inactivation are important at the meso-scale (tens of meters), and inactivation becomes the dominant mechanism for reducing the transport of viable bacteria at the field scale (hundreds of meters). 相似文献
182.
We report the fabrication and characterization of uniformly sized nanopore arrays, integrated into an optical detection system for high-throughput DNA sequencing applications. Nanopore arrays were fabricated using focused ion beam milling, followed by?TiO(2) coating using atomic layer deposition. The?TiO(2) layer decreases the initial pore diameter down to the sub-10?nm range, compatible with the requirements for nanopore-based sequencing using optical readout. We find that the?TiO(2) layers produce a lower photoluminescence background as compared with the more widely used Al(2)O(3) coatings. The functionality of the nanopore array was demonstrated by the simultaneous optical detection of DNA-quantum dot conjugates, which were electro-kinetically driven through the nanopores. Our optical scheme employs total internal reflection fluorescence microscopy to illuminate a wide area of the?TiO(2)-coated membrane. A highly parallel system for observing DNA capture events in a uniformly sized 6?×?6 nanopore array was experimentally realized. 相似文献
183.
Ludwig A Leviatan Y 《Journal of the Optical Society of America. A, Optics, image science, and vision》2004,21(7):1334-1343
A novel method derived from the source-model technique is presented to solve the problem of scattering of an electromagnetic plane wave by a two-dimensional photonic crystal slab that contains an arbitrary defect (perturbation). In this method, the electromagnetic fields in the perturbed problem are expressed in terms of the field due to the periodic currents obtained from a solution of the corresponding unperturbed problem plus the field due to yet-to-be-determined correction current sources placed in the vicinity of the perturbation. Appropriate error measures are suggested, and a few representative structures are presented and analyzed to demonstrate the versatility of the proposed method and to provide physical insight into waveguiding and defect coupling mechanisms typical of finite-thickness photonic crystal slabs. 相似文献
184.
Alon?AltmanEmail author Ya'Acov?Peterzil Yoad?Winter 《Journal of Logic, Language and Information》2005,14(4):445-455
We give a complete characterization of the class of upward monotone generalized quantifiers Q1 and Q2 over countable domains that satisfy the scheme Q1 x Q2 y φ → Q2 y Q1 x φ. This generalizes the characterization of such quantifiers over finite domains, according to which the scheme holds iff Q1 is ∃ or Q2 is ∀ (excluding trivial cases). Our result shows that in infinite domains, there are more general types of quantifiers that
support these entailments. 相似文献
185.
Noga Alon Haim Kaplan Michael Krivelevich Dahlia Malkhi Julien Stern 《Information and Computation》2002,174(2):203
In this paper, we provide a method to safely store a document in perhaps the most challenging settings, a highly decentralized replicated storage system where up to half of the storage servers may incur arbitrary failures, including alterations to data stored in them. Using an error correcting code (ECC), e.g., a Reed–Solomon code, one can take n pieces of a document, replace each piece with another piece of size larger by a factor of
such that it is possible to recover the original set even when up to t of the larger pieces are altered. For t close to n/2 the space blowup factor of this scheme is close to n, and the overhead of an ECC such as the Reed–Solomon code degenerates to that of a trivial replication code. We show a technique to reduce this large space overhead for high values of t. Our scheme blows up each piece by a factor slightly larger than two using an erasure code which makes it possible to recover the original set using n/2−O(n/d) of the pieces, where d≈80 is a fixed constant. Then we attach to each piece O(d log n/log d) additional bits to make it possible to identify a large enough set of unmodified pieces, with negligible error probability, assuming that at least half the pieces are unmodified and with low complexity. For values of t close to n/2 we achieve a large asymptotic space reduction over the best possible space blowup of any ECC in deterministic setting. Our approach makes use of a d-regular expander graph to compute the bits required for the identification of n/2−O(n/d) good pieces. 相似文献
186.
Alon Shamir 《中国电子商情》2007,(4):44-45
移动电话采用GPS
最新的市场预测显示,GPS是移动电话的下一个热门功能。移动电话制造商、服务提供商和用户都在不断地关注着移动电话可采用的新功能。GPS能够实现各种热门服务,如:导航、交通信息、游戏、家庭成员或朋友的定位等等。[第一段] 相似文献
187.
Poly(ferrocenylene-methylmethylene) (PFMM) was prepared and subsequently crosslinked by the aid of either 1,1'-bis(α-hydroxyethyl)ferrocene or polyfunctional ferrocene polymers, containing reactive-CH2OH or-CH(CH3)OH groups. The thermal behavior of both the primary polymer and the thermoset was investigated. The solubility parameter of PFMM was determined and the degree of crosslinking was studied by solvent swelling and sol fraction measurements. Various thermosetting structural composites were prepared and subjected to mechanical testing. 相似文献
188.
Learning to match ontologies on the Semantic Web 总被引:19,自引:0,他引:19
AnHai?DoanEmail author Jayant?Madhavan Robin?Dhamankar Pedro?Domingos Alon?Halevy 《The VLDB Journal The International Journal on Very Large Data Bases》2003,12(4):303-319
On the Semantic Web, data will inevitably come from many different ontologies, and information processing across ontologies is not possible without knowing the semantic mappings between them. Manually finding such mappings is tedious, error-prone, and clearly not possible on the Web scale. Hence the development of tools to assist in the ontology mapping process is crucial to the success of the Semantic Web. We describe GLUE, a system that employs machine learning techniques to find such mappings. Given two ontologies, for each concept in one ontology GLUE finds the most similar concept in the other ontology. We give well-founded probabilistic definitions to several practical similarity measures and show that GLUE can work with all of them. Another key feature of GLUE is that it uses multiple learning strategies, each of which exploits well a different type of information either in the data instances or in the taxonomic structure of the ontologies. To further improve matching accuracy, we extend GLUE to incorporate commonsense knowledge and domain constraints into the matching process. Our approach is thus distinguished in that it works with a variety of well-defined similarity notions and that it efficiently incorporates multiple types of knowledge. We describe a set of experiments on several real-world domains and show that GLUE proposes highly accurate semantic mappings. Finally, we extend GLUE to find complex mappings between ontologies and describe experiments that show the promise of the approach.Received: 16 December 2002, Accepted: 16 April 2003, Published online: 17 September 2003Edited by: Edited by B.V. Atluri, A. Joshi, and Y. Yesha 相似文献
189.
3 patients with giant lipomas located in unusual anatomic locations are described. All 3 cases had clinical features similar to those of the malignant counterpart, liposarcoma. All were operated on and the tumors removed. Follow-up ranged from 12 years, with no recurrence during that period. The treatment of choice for these lesions is surgical removal and long-term follow-up. 相似文献
190.
Nachman Paster Alon Pushinsky Mazal Menasherov Ilan Chet 《Journal of the science of food and agriculture》1992,58(4):589-591
Aspergillus ochraceus and A flavus were grown on synthetic media (SM) supplemented with 50 or 200 ml litre?1 SM on which A niger had been grown previously ( ‘A niger medium’ = ANM). Controls included SM acidified to pH 6.0 or 4.4, SM diluted with 50 or 200 ml litre?1 water, and diluted-acidified SM. For both fungi, higher growth inhibition was recorded on ANM-containing SM than in the controls. Aflatoxin formation was markedly inhibited on SM to which 20 ml litre?1 ANM extract (in methanol/chloroform, 2:1 v) had been added, although the growth of A flavus on that medium was almost the same as that in the control. It is concluded that the inhibitory effect of A niger on the growth of fungi should not be attributed merely to pH reduction, but also, mainly, to metabolites produced by the fungus in the growth medium, even at early stages of its growth. 相似文献