全文获取类型
收费全文 | 53574篇 |
免费 | 13616篇 |
国内免费 | 226篇 |
专业分类
电工技术 | 1140篇 |
技术理论 | 1篇 |
综合类 | 280篇 |
化学工业 | 20094篇 |
金属工艺 | 1017篇 |
机械仪表 | 1500篇 |
建筑科学 | 2209篇 |
矿业工程 | 105篇 |
能源动力 | 1326篇 |
轻工业 | 8373篇 |
水利工程 | 376篇 |
石油天然气 | 297篇 |
武器工业 | 47篇 |
无线电 | 8492篇 |
一般工业技术 | 13834篇 |
冶金工业 | 2311篇 |
原子能技术 | 209篇 |
自动化技术 | 5805篇 |
出版年
2024年 | 36篇 |
2023年 | 191篇 |
2022年 | 364篇 |
2021年 | 754篇 |
2020年 | 1759篇 |
2019年 | 3454篇 |
2018年 | 3406篇 |
2017年 | 3797篇 |
2016年 | 4229篇 |
2015年 | 4287篇 |
2014年 | 4423篇 |
2013年 | 5850篇 |
2012年 | 3552篇 |
2011年 | 3453篇 |
2010年 | 3408篇 |
2009年 | 3251篇 |
2008年 | 2811篇 |
2007年 | 2489篇 |
2006年 | 2189篇 |
2005年 | 1825篇 |
2004年 | 1741篇 |
2003年 | 1657篇 |
2002年 | 1584篇 |
2001年 | 1367篇 |
2000年 | 1301篇 |
1999年 | 743篇 |
1998年 | 623篇 |
1997年 | 472篇 |
1996年 | 294篇 |
1995年 | 213篇 |
1994年 | 214篇 |
1993年 | 215篇 |
1992年 | 141篇 |
1991年 | 114篇 |
1990年 | 115篇 |
1989年 | 108篇 |
1988年 | 77篇 |
1987年 | 71篇 |
1986年 | 67篇 |
1985年 | 90篇 |
1984年 | 76篇 |
1983年 | 48篇 |
1982年 | 44篇 |
1981年 | 45篇 |
1980年 | 49篇 |
1979年 | 41篇 |
1977年 | 61篇 |
1976年 | 89篇 |
1975年 | 40篇 |
1973年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
91.
Robotic synthesis is making possible the synthesis of large, systematically designed sets of compounds. We analyze a 512-compound set that is a 2(9) full factorial experimental design using a recursive partitioning algorithm, FIRM, and a high-dimension visualization tool, TempleMVV. These techniques are used to quickly and easily identify the main trends in the data set and also identify unusual observations. We show that analytical and visualization methods can be used synergistically to analyze a large, complex, high-dimensional data set. We also show that a fractional factorial design of 128 compounds would give essentially the same information. 相似文献
92.
93.
AF Minnick MJ Roberts WB Young RM Kleinpell RJ Marcantonio 《Canadian Metallurgical Quarterly》1997,35(4):399-409
OBJECTIVES: Market forces make it essential to know what policies and actions influence patients' reports of hospital services. No studies have examined the role of patient characteristics, labor quality and staff characteristics, nonlabor resources, managerial practices, and employee attitudes within a single investigation. METHODS: The authors collected, simultaneously, data about labor, management and service processes, nonlabor resources, and employee attitudes on 117 nonintensive medical-surgical inpatient units in 17 hospitals selected from a pool of 69 institutions within a metropolitan area by a stratified random sample. Of the 2,595 patients who agreed to participate, 2,051 (79%) completed telephone interviews regarding their experiences with physical care, education, and pain management services within 26 days of hospital discharge. RESULTS: A significant amount of variation in patients' service reports was explained (adjusted R2 = 0.41 physical care, 0.35 pain management, 0.44 education). Although the predictors varied for each service report, patient characteristics, especially those related to personal resources, had a large explanatory role. A labor assignment pattern that could explain why earlier studies found labor quality and staff characteristics to have only a weak role in the prediction of patients' service reports was noted. CONCLUSIONS: The results related to patient characteristics may indicate opportunities to improve care by confronting service design strategies that erroneously rely on a homogeneous patient population. Measurement challenges identified by this study must be addressed to determine the role of labor quantity and staff characteristics. 相似文献
94.
Richard D. Dick William L. Fourney Deborah J. Goodings Chaun‐Ping Lin Leonhard E. Bernold 《Canadian Metallurgical Quarterly》1992,5(1):59-69
The utilization of explosives for excavation on the lunar surface is under serious consideration as a part of the design for construction of temporary and permanent bases. An excavation research program has shown that small‐scale explosives blasting in a lunar‐soil simulant will greatly reduce the digging forces required for scoop and dragline excavators. Some crater‐blasting parameters were determined for the lunar soil simulant at one Earth gravity and at 10 Earth gravities using a centrifuge. The size of the craters produced at 10 Earth gs matched those formed at one earth g by scaling according to the weight of the explosive. These data can be applied to explosive‐excavation problems such as habitat construction, burial of nuclear power sources, and the rapid construction of shelters remote from the main base to shield against solar‐flare activity. 相似文献
95.
J. Weise Dr.‐Ing. O. Yezerska M. Busse M. Haesche V. Zanetti‐Bueckmann M. Schmitt 《Materialwissenschaft und Werkstofftechnik》2007,38(11):901-906
Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated. 相似文献
96.
We define the very rich language of composed conditionals on a three‐valued logic and use this language as the communication tool between man and machine. Communication takes place for three reasons: knowledge acquisition, query, and response. Learning, thinking, and answering questions are of a pure information theoretical nature. The pivot of this knowledge processing concept is the amount of information (bit) we receive if a conditional becomes true. We follow an axiomatic approach to information theory rather than the classical probabilistic approach of Shannon; information comes first, and then comes probability. In the light of this philosophy, query and response experience new interpretations. Both, acquisition and response are realized by maximizing entropy and minimizing relative entropy, respectively. The iterative solution of these mathematical optimization problems gives new insights into the adaptation of prior knowledge to new information. Our expert system shell SPIRIT supports this kind of knowledge processing, which will be established by suitable examples. © 2003 Wiley Periodicals, Inc. 相似文献
97.
Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
98.
99.
100.
Research in CASE environments has focused on two kinds of integration: tool and object. A higher level of integration, process integration, which represents development activities explicitly in a software process model to guide and coordinate development and to integrate tools and objects, is proposed. Process integration uses software process models (SPMs) a process driver, a tool set, and interfaces for both developers and managers to form the backbone of a process-driven CASE environment. The developer's interface, a working environment that lets developers enact an SPM, and the manager's interface which gives managers and analysts the tools to define, monitor, and control the SPMs that developers are working on concurrently are discussed. The Softman environment experiment, an implementation of process-driven CASE environments with existing CASE environments, is reviewed 相似文献