全文获取类型
收费全文 | 27841篇 |
免费 | 2403篇 |
国内免费 | 1341篇 |
专业分类
电工技术 | 934篇 |
技术理论 | 24篇 |
综合类 | 3276篇 |
化学工业 | 2052篇 |
金属工艺 | 267篇 |
机械仪表 | 332篇 |
建筑科学 | 11792篇 |
矿业工程 | 648篇 |
能源动力 | 972篇 |
轻工业 | 495篇 |
水利工程 | 1741篇 |
石油天然气 | 210篇 |
武器工业 | 39篇 |
无线电 | 2337篇 |
一般工业技术 | 2384篇 |
冶金工业 | 881篇 |
原子能技术 | 515篇 |
自动化技术 | 2686篇 |
出版年
2024年 | 109篇 |
2023年 | 454篇 |
2022年 | 741篇 |
2021年 | 1020篇 |
2020年 | 953篇 |
2019年 | 849篇 |
2018年 | 658篇 |
2017年 | 975篇 |
2016年 | 961篇 |
2015年 | 897篇 |
2014年 | 2108篇 |
2013年 | 2231篇 |
2012年 | 1833篇 |
2011年 | 2179篇 |
2010年 | 1842篇 |
2009年 | 1786篇 |
2008年 | 1727篇 |
2007年 | 1739篇 |
2006年 | 1655篇 |
2005年 | 1249篇 |
2004年 | 1059篇 |
2003年 | 837篇 |
2002年 | 762篇 |
2001年 | 637篇 |
2000年 | 468篇 |
1999年 | 296篇 |
1998年 | 228篇 |
1997年 | 220篇 |
1996年 | 139篇 |
1995年 | 135篇 |
1994年 | 119篇 |
1993年 | 94篇 |
1992年 | 90篇 |
1991年 | 57篇 |
1990年 | 58篇 |
1989年 | 81篇 |
1988年 | 53篇 |
1987年 | 27篇 |
1986年 | 26篇 |
1985年 | 35篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 29篇 |
1981年 | 25篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1964年 | 6篇 |
1959年 | 7篇 |
1957年 | 9篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 953 毫秒
61.
揭示了城市环境的基本性质的基本特征,研究了城市环境对人的心理影响和生理影响。指出城市环境建设不公要满足人的物质需要,还要满足人的精神需要。 相似文献
62.
63.
64.
Open window buses without air-conditioning are a major mode of urban and inter-city transport in most countries. High occupancy
combined with hot and humid conditions makes travel in these buses quite uncomfortable. In this study air flow through a bus
has been studied that could be the basis for low cost and eco-friendly methods of increasing passenger comfort and possibly
reduce drag. The aerodynamics of such a road vehicle has not been studied as previous investigations have been confined to
vehicles with closed windows that present a smooth exterior to air flow. Using a 1:25 scaled Perspex model of an urban bus
in Delhi, flow visualization was performed in a water channel. The Reynolds numbers were one-tenth of a real bus moving at
10 m/s. Smoke and tuft visualizations were also performed on an urban bus at 40 km/h. Numerical simulations were performed
at the actual Reynolds number. Even though there were Reynolds number differences, the broad features were similar. Air enters
the bus from the rear windows, moves to the front (relative to the bus) and exits from the front windows. Inside air velocity
relative to the bus is about one-tenth of the free-stream velocity. The flow is highly three-dimensional and unsteady. 相似文献
65.
Hermann Knoflacher 《Sadhana》2007,32(4):293-307
Technological determinism has become a kind of religion for many people since it appears to offer solutions for societal problems
as never before in history. Transport is one of the fascinating technology branches developed during the last 200 years. Effortless
movement over long distances has become possible for car users as long as cheap fossil energy is available. However, the effect
of fast transport on urban structures and society was not taken into account when developing these technical means. Technologists
and economists have used indicators for expected benefits of these fast transport modes without taking into account the real
system effects on society and urban structures. Plausible assumptions and hopes instead of scientific understanding of the
complex system are used in practice. In contradiction to widely held beliefs of transportation planners, there is actually
no growth of mobility if counted in number of trips per person per day, no time saving by increasing speed in the system,
and no real freedom of modal choice. Modal choice is dependent on physical and other structures, the artificial environment
built by urban planners, transport experts and political decisions. The core hypothesis of traditional urban and transport
planning ‘growth of mobility’, ‘travel time saving by increasing speed’ and ‘freedom of modal choice’ are myths and do not
exist in the real urban and transport system. This is the reason why urban planning and transport planning based on traditional
non-scientific assumptions is creating continuously not only more transport problems, but also environmental and social as
well as economic problems all over the world, where these principals are applied. Urban transport planning in Europe, understanding
the transport system and the solutions are presented in this paper. 相似文献
66.
城市化进程中的小城镇交通初探 总被引:4,自引:0,他引:4
通过对小城镇城市结构、路网结构、交通结构和交通管理特征进行详细分析,得出小城镇交通问题症结所在,并初步提出小城镇交通规划和交通治理的对策。 相似文献
67.
No authorship indicated 《Canadian Metallurgical Quarterly》2003,58(11):897a
Announces that Phyllis A. Katz has won the Award for Distinguished Senior Career Contributions to the Public Interest. The award is presented for the honoree's research on the origins and development of both racial and gender attitudes and her contributions to psychology in the public interest within the American Psychological Association. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
68.
Bedload Transport in Alluvial Channels 总被引:1,自引:0,他引:1
Miguel Bravo-Espinosa W. R. Osterkamp Vicente L. Lopes 《Canadian Metallurgical Quarterly》2003,129(10):783-795
Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams. 相似文献
69.
Faith Myles S.; Fontaine Kevin R.; Baskin Monica L.; Allison David B. 《Canadian Metallurgical Quarterly》2007,133(2):205
The authors reviewed the evidential basis of three environmental approaches to reducing population obesity: What are the effects of (a) taxing or subsidizing foods, (b) manipulating the ease of food access, and (c) restricting access to certain foods? A narrative review evaluated evidence using National Heart, Lung, and Blood Institute criteria. There was strong evidence that subsidization influences food purchases, but not necessarily food consumption or body weight. Ease of food access may influence food purchases, and possibly food intake and body weight. Data on restriction were lacking. More studies are needed to justify that altering these macro-environmental variables will necessarily reduce population obesity. A proposed conceptual model posits that the steps through environmental interventions may exert intended and unintended influences on body weight and obesity prevalence. Contemplated policy changes should weigh scientific evidence with social judgments and values concerning changes to the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.
Ahluwalia Jasjit S.; Nollen Nicole; Kaur Harsohena; James Aimee S.; Mayo Matthew S.; Resnicow Ken 《Canadian Metallurgical Quarterly》2007,26(2):214
Objectives: Examine the effectiveness of an intervention to increase fruits and vegetables (FV) consumption among smokers. Design: Cluster-randomized trial of 20 public housing developments; 10 randomly assigned to an FV intervention and 10 to a smoking cessation intervention. Main outcome measures: Usual (past 7 days) and past 30 days change in daily FV intake at 8 weeks and 6 months postbaseline. Results: Greater increases were seen in the FV group. At Week 8 and Month 6, the FV group had consumed 1.58 (p = .001) and 0.78 (p = .04), respectively, more daily FV servings in the past 7 days than the cessation group. At the same time points, the FV group had consumed 3.61 (p = .01) and 3.93 (p = .01), respectively, more FV servings in the past 30 days than the cessation group. Completing more motivational interviewing sessions (p = .02) and trying more recipes (p = .02) led to significantly greater increases at Month 6 among FV participants. Conclusions: Motivational interviewing counseling and lifestyle modification through trying out healthy recipes may be effective in helping a high-risk population increase their FV intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献