全文获取类型
收费全文 | 2051篇 |
免费 | 8篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 6篇 |
综合类 | 4篇 |
化学工业 | 52篇 |
金属工艺 | 5篇 |
机械仪表 | 14篇 |
建筑科学 | 22篇 |
能源动力 | 15篇 |
轻工业 | 30篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 36篇 |
一般工业技术 | 85篇 |
冶金工业 | 1663篇 |
原子能技术 | 7篇 |
自动化技术 | 122篇 |
出版年
2021年 | 5篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 24篇 |
2012年 | 11篇 |
2011年 | 11篇 |
2010年 | 16篇 |
2009年 | 18篇 |
2008年 | 19篇 |
2007年 | 23篇 |
2006年 | 18篇 |
2005年 | 13篇 |
2004年 | 22篇 |
2003年 | 18篇 |
2002年 | 10篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 49篇 |
1998年 | 449篇 |
1997年 | 248篇 |
1996年 | 211篇 |
1995年 | 99篇 |
1994年 | 99篇 |
1993年 | 106篇 |
1992年 | 15篇 |
1991年 | 22篇 |
1990年 | 22篇 |
1989年 | 35篇 |
1988年 | 28篇 |
1987年 | 31篇 |
1986年 | 21篇 |
1985年 | 27篇 |
1984年 | 7篇 |
1983年 | 22篇 |
1982年 | 10篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 50篇 |
1976年 | 141篇 |
1975年 | 5篇 |
1973年 | 9篇 |
1972年 | 5篇 |
1970年 | 7篇 |
1969年 | 7篇 |
排序方式: 共有2065条查询结果,搜索用时 15 毫秒
81.
This study presents a novel application of marine geoelectromagnetic technique, in an attempt to delineate freshwater extension of the coastal sub-aquifers beneath the SE Mediterranean Sea, along central Israel. The novel marine Ex-Bz time domain electromagnetic (TDEM) geophysical method was applied, demonstrating high sensitivity to the presence of sub-seafloor electrically resistive structures up to several kilometers offshore (shallow marine environment). The study included 19 marine measurements located offshore between Ashdod in the south to Tel-Aviv in the north, where a previous onshore study detected fresh groundwater below seawater intrusion at the coast line. The offshore measurements were conducted to distances of up to 3 km from the shoreline. It was found that the lower sub-aquifer contains fresh groundwater (resistivity >10 Ω-m) to a distance of 2.8 km offshore along the 30 km strip, and is probably constrained by lateral geo-facial changes. 相似文献
82.
DN Maiorov ER Wilton E Badoer D Petrie GA Head SC Malpas 《Canadian Metallurgical Quarterly》1999,815(2):227-236
OBJECT: This study is a retrospective analysis of clinical data obtained in 28 patients affected by obstructive hydrocephalus who presented with signs of midbrain dysfunction during episodes of shunt malfunction. METHODS: All patients presented with an upward gaze palsy, sometimes associated with other signs of oculomotor dysfunction. In seven cases the ocular signs remained isolated and resolved rapidly after shunt revision. In 21 cases the ocular signs were variably associated with other clinical manifestations such as pyramidal and extrapyramidal deficits, memory disturbances, mutism, or alterations in consciousness. Resolution of these symptoms after shunt revision was usually slow. In four cases a transient paradoxical aggravation was observed at the time of shunt revision. In 11 cases ventriculocistemostomy allowed resolution of the symptoms and withdrawal of the shunt. Simultaneous supratentorial and infratentorial intracranial pressure recordings performed in seven of the patients showed a pressure gradient between the supratentorial and infratentorial compartments, with a higher supratentorial pressure before shunt revision. Inversion of this pressure gradient was observed after shunt revision and resolution of the gradient was observed in one case after third ventriculostomy. In six recent cases, a focal midbrain hyperintensity was evidenced on T2-weighted magnetic resonance imaging sequences at the time of shunt malfunction. This rapidly resolved after the patient underwent third ventriculostomy. CONCLUSIONS: It is probable that in obstructive hydrocephalus, at the time of shunt malfunction, the development of a transtentorial pressure gradient could initially induce a functional impairment of the upper midbrain, inducing upward gaze palsy. The persistence of the gradient could lead to a global dysfunction of the upper midbrain. Third ventriculostomy contributes to equalization of cerebrospinal fluid pressure across the tentorium by restoring free communication between the infratentorial and supratentorial compartments, resulting in resolution of the patient's clinical symptoms. 相似文献
83.
Constraints and AI planning 总被引:1,自引:0,他引:1
Nareyek A. Freuder E.C. Fourer R. Giunchiglia E. Goldman R.P. Kautz H. Rintanen J. Tate A. 《Intelligent Systems, IEEE》2005,20(2):62-72
Tackling real-world planning problems often requires considering various types of constraints, which can range from simple numerical comparators to complex resources. This article provides an overview of techniques to deal with such constraints by expressing planning within general constraint-solving frameworks. Our goal here is to explore the interplay of constraints and planning, highlighting the differences between propositional satisfiability (SAT), integer programming (IP), and constraint programming (CP), and discuss their potential in expressing and solving AI planning problems. 相似文献
84.
Jerry Goldman Steve Renals Steven Bird Franciska de Jong Marcello Federico Carl Fleischhauer Mark Kornbluh Lori Lamel Douglas W. Oard Claire Stewart Richard Wright 《International Journal on Digital Libraries》2005,5(4):287-298
Spoken-word audio collections cover many domains, including radio and television broadcasts, oral narratives, governmental proceedings, lectures, and telephone conversations. The collection, access, and preservation of such data is stimulated by political, economic, cultural, and educational needs. This paper outlines the major issues in the field, reviews the current state of technology, examines the rapidly changing policy issues relating to privacy and copyright, and presents issues relating to the collection and preservation of spoken audio content . 相似文献
85.
86.
Goldman C.V. Rosenschein J.S. 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2002,32(1):135-148
Problems approached by multi-agent systems are typically complex. It is usually difficult to know at system design stage how many agents need to be in the system, what each agent's role is, and how the agents should interact to get optimal performance out of the group. The aim of the testbed presented here is to investigate which kinds of multi-agent systems could be developed to solve ranges of problems, avoiding the need to reorganize the agents from scratch for each task. The agent organization process explored here is based on the agents' knowledge, and not on their tasks. This opens up a new approach for distributed artificial intelligence designers to have their domain organized before the allocation of tasks among agents. These kinds of organizations should be more robust for solving different problems related to the same knowledge. We define information oriented domains for that purpose. An evolutionary approach to the design of a multi-agent system is suggested. Our model is based on a cellular automaton whose rules of dynamics induce the formation of an organization of agents. Patterns of organization obtained empirically are presented. Our knowledge-based organization approach is analyzed both from theoretical and practical perspectives 相似文献
87.
David A. Conner Ph.D. P.E. Gary J. Grimes Ph.D. Jay Goldman D.SC. P.E. 《Journal of Systems Integration》2000,10(1):81-94
For telemedicine to reach its potential in the Internet2 environment,significant progress must be made in a number of areas. The emergingtelecommunications will include the Internet2 between medicalinstitutions and emerging broadband loop and wireless technologiesfor interconnections to homes. Within the technical environment,problems that must be addressed include the development of robotic-controlled,remote-monitoring devices unique to the various medical specialties;the encoding, transmission, and decoding of raw data specificto the specialized needs of various medical application areas;and the reduction of data for storage and retrieval in patientrecords. Institutionally, human factor and information accessissues with respect to physicians, patients, and non-physicianhealthcare providers must be addressed; healthcare insuranceprovider policies, government regulation, and state licensinglaws must be adapted for a new paradigm of healthcare delivery;and the philosophy of capital investment for the delivery ofhealthcare must be revised.Many current practiceswill be supplanted by home healthcare alternatives, the use ofpatient-initiated preventive healthcare initiatives, and remote-clinicactivity. These applications will result in central record archivingsystems; the need for encryption schemes, virus protection, andvandalism protection; extensive, additional connectivity betweenhealthcare providers and professionals; and new commercial playersin the healthcare arena.The hot applicationareas will include women's health, children's health, healthcarefor senior citizens, home healthcare, well-patient monitoring,and early-detection of medical problems. 相似文献
88.
Bell S Goldman VM Bistrian BR Arnold AH Ostroff G Forse RA 《Critical reviews in food science and nutrition》1999,39(2):189-202
Heart disease is the leading cause of death in the U.S. One way to reduce the risk of developing the disease is to lower serum cholesterol levels by making dietary changes. In addition to reducing intake of total fat, saturated fat, and dietary cholesterol, serum cholesterol can be further reduced by added fiber, especially from sources rich in beta-glucan. In this review, two sources of beta-glucan are described; one source is oats and the other yeast. Their chemical structures and physical properties are compared, and their effect on serum lipid levels is described. Oat beta-glucans are found in various breakfast cereals and snacks. Usually, several servings of these products are required to meet the Food and Drug Administration's claim of reducing the risk of heart disease. The yeast-derived fiber is a more concentrated source of beta-glucan than the oat product. It is currently being tested in a wide variety of food products. 相似文献
89.
90.
Laboratory investigation of the mass stability of sampling cassettes from inhalable aerosol samplers
A study was conducted to evaluate the mass stability of the materials used in the construction of samplers with internal cassettes for the gravimetric measurement of inhalable aerosol exposures. The internal cassettes from IOM samplers were studied. Results indicate that the mass stability of filters is uniform, but the mass stability of the cassette material may dramatically affect the results of the measurement. Cassettes constructed from plastic exhibited drastic shifts in mass depending on the environmental conditions of their storage. Under room humidity, the plastic cassettes absorbed 1 to 2 mg of water over several days. When these cassettes were placed in a desiccator, they lost mass consistently but did not approach a stable mass. Studies repeated with cassettes made of stainless steel showed negligible mass variability. Based on this study, the use of stainless steel cassettes is recommended for gravimetric determinations of aerosol exposure, although field blanks may in some cases be used for correction of data from plastic cassettes. This study shows the need to evaluate the mass stability of the cassette material of any sampling device where an internal cassette is weighed together with the filter. 相似文献