首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   340篇
  免费   2篇
电工技术   2篇
化学工业   82篇
金属工艺   2篇
机械仪表   2篇
建筑科学   8篇
能源动力   3篇
轻工业   166篇
石油天然气   1篇
无线电   1篇
一般工业技术   20篇
冶金工业   27篇
自动化技术   28篇
  2014年   3篇
  2013年   43篇
  2011年   6篇
  2008年   5篇
  2007年   4篇
  2006年   5篇
  2005年   6篇
  2004年   5篇
  2002年   5篇
  2001年   5篇
  1999年   5篇
  1997年   9篇
  1996年   4篇
  1995年   8篇
  1994年   6篇
  1993年   5篇
  1992年   5篇
  1991年   7篇
  1990年   7篇
  1989年   3篇
  1988年   6篇
  1987年   8篇
  1986年   11篇
  1985年   7篇
  1984年   5篇
  1983年   4篇
  1982年   4篇
  1980年   7篇
  1979年   3篇
  1978年   4篇
  1977年   8篇
  1976年   7篇
  1975年   5篇
  1974年   7篇
  1973年   6篇
  1972年   3篇
  1971年   5篇
  1970年   7篇
  1968年   19篇
  1967年   19篇
  1966年   6篇
  1965年   4篇
  1964年   2篇
  1963年   3篇
  1962年   2篇
  1961年   2篇
  1959年   6篇
  1956年   2篇
  1955年   3篇
  1944年   3篇
排序方式: 共有342条查询结果,搜索用时 718 毫秒
81.
82.
83.
ABSTRACT: A host of empirical studies have indicated that stadiums and arenas have no significant impact on metropolitan area income or employment. In light of this evidence, the continued proliferation of public investment in sports facilities begs the question: Is there some other justification for this spending, or are policymakers simply acting against the public interest (either irrationally, or in response to political‐economic influences)? A possibility that has not been fully explored is the notion that stadiums and teams generate tangible and intangible consumption benefits that could support some level of public investment. This research builds on a small foundation of literature that is moving discussion beyond the economic catalyst debate by providing an empirical measure of the consumption benefits that accrue to a region as the result of hosting a major league sports team. A contingent valuation survey is used to quantify the consumption benefits that would be associated with the relocation of a major league baseball team to Portland, Oregon. An empirical measure of the region's aggregate willingness to pay for the benefits associated with hosting a team is disaggregated into option and existence values, which can then be compared to any proposed level of public contribution to a new stadium. The findings indicate that consumption benefits would only support a capital investment of approximately $74 million; a figure far smaller than the typical stadium subsidy. The majority of projected benefits are associated with expected public goods and externalities, rather than anticipated attendance, indicating that an equitable financing plan should employ nonuser revenue sources. The level of projected benefits does not vary by locality within the metropolitan area, which argues for a regional cost‐sharing approach. The willingness of residents to pay for stadium construction is tempered by a concern about other pressing social needs in the Portland area and a reaction to the current tax climate.  相似文献   
84.
Both representational and self organizing approaches to language avoid in different ways the concept of symbol We argue that representationalism denies the particular aspects of a subjects embodiment while the self organizing paradigm refuses to address the utility of the concept of symbol and its evolutionary relationship with an environment We call for an inclusive approach that considers the syntactic semantic and pragmatic aspects of language We further offer a mathematical structure defined in terms of fuzzy set and evidence theories as a model of linguistic categories under this inclusive framework  相似文献   
85.
A hot stream of a very viscous fluid, such as a polymer, may be cooled in a heal exchanger consisting of multiple parallel passages. However, if a quite uniform temperature distribution is desired in the exit stream, the fluid flowing through each of the passages must be cooled to very nearly the same temperature. An analytical treatment of heat transfer and pressure drop in viscous flow between parallel plates during cooling reveals the operating conditions and passage geometry required to achieve this goal. Solution of the equation obtained depends only on the physical properties of the fluid and the cooler geometry. Non-Newtonian behavior of the fluid is approximated by a power-law function. A unique type of heat exchanger was designed on the basis of this analysis.  相似文献   
86.
能量桩是一种由地源热泵技术与桩基埋管换热器结合组成的经济高效节能减排技术。简要介绍了基于地源热泵技术的能量桩技术原理、桩型、埋管形式以及技术经济优势,总结了近年来国内外能量桩技术的研究现状及其工程应用,包括基于灌注桩的传热管埋管形式和基于预制桩的传热管埋管形式;指出了目前工程应用中存在的一些主要问题,并提出一种新型PCC能量桩技术及其施工工艺;最后简要分析了能量桩技术在国家节能减排工程中的应用前景,并提出有待进一步研究的方向。  相似文献   
87.
Repetitive construction processes exhibit improvement in production rate as repetitions increase. A learning curve can be developed for such construction processes that can improve the predictive accuracy for the early portions of project schedules. This paper discusses a method for incorporating learning development in a construction simulation model. The case study model represents the construction of a guide wall for a lock using a mobile cofferdam. The impact of including learning development on model results is reported as well as a sensitivity analysis.  相似文献   
88.
In this, the First part of a two part work, a general model of spatial organization is introduced. Following a brief synopsis of some of Spinoza's and Leibniz's views regarding natural structure, an extension of the Spinozian model is presented in which the attribute spatial extension is portrayed as a relational system that implicitly underlies the differentiation of sensible space into “modifications” (“natural systems”) and the latter's subdifferentiation into “modes” On the basis of this model, all instances of modal differentiation are understood to take place in a manner explained by this relational structure, the existence (but not the specific characteristics) of which is initially assumed. The nature of the structure is then deduced according to a “most-probable-state” kind of logic; next, it is demonstrated via simulation that the resulting aspatial model of internal relations has a corresponding spatial interpretation (and therefore, in theory, that sensible space structures can be supported by the particular rational ordering posed). The matter of how to apply the model to the study of real world systems is taken up last; discussion focuses on related aspects of the treatment of equilibrium and nonequilibrium systems and the recognition and measurement of modal structures.  相似文献   
89.
90.
Transmission electron microscopy was used to observe variations in composition in single crystals of Fe y Mn1– y O1+] x on a scale of 100 to 500 Å. Compositional fluctuations were resolved as lamellar-like striations oriented primarily in the [100] direction. Specimens had been equilibrated at 900°C in oxygen partial pressures within the monoxide phase region and then quenched to room temperature. A region of solid-solid immiscibility in the monoxide phase field is proposed. A different submicrostructure resulted from low-temperature decomposition (150°C) due to localized heating when samples were prepared by ion-bombardment thinning.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号