全文获取类型
收费全文 | 4008篇 |
免费 | 33篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 15篇 |
综合类 | 2篇 |
化学工业 | 267篇 |
金属工艺 | 27篇 |
机械仪表 | 59篇 |
建筑科学 | 95篇 |
矿业工程 | 8篇 |
能源动力 | 47篇 |
轻工业 | 184篇 |
水利工程 | 17篇 |
石油天然气 | 6篇 |
无线电 | 159篇 |
一般工业技术 | 327篇 |
冶金工业 | 2626篇 |
原子能技术 | 29篇 |
自动化技术 | 175篇 |
出版年
2021年 | 13篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 15篇 |
2017年 | 23篇 |
2016年 | 16篇 |
2015年 | 16篇 |
2014年 | 28篇 |
2013年 | 97篇 |
2012年 | 56篇 |
2011年 | 61篇 |
2010年 | 46篇 |
2009年 | 43篇 |
2008年 | 58篇 |
2007年 | 57篇 |
2006年 | 47篇 |
2005年 | 52篇 |
2004年 | 48篇 |
2003年 | 31篇 |
2002年 | 53篇 |
2001年 | 45篇 |
2000年 | 36篇 |
1999年 | 117篇 |
1998年 | 793篇 |
1997年 | 455篇 |
1996年 | 280篇 |
1995年 | 153篇 |
1994年 | 143篇 |
1993年 | 179篇 |
1992年 | 44篇 |
1991年 | 63篇 |
1990年 | 57篇 |
1989年 | 65篇 |
1988年 | 63篇 |
1987年 | 67篇 |
1986年 | 64篇 |
1985年 | 45篇 |
1984年 | 35篇 |
1983年 | 33篇 |
1982年 | 25篇 |
1981年 | 43篇 |
1980年 | 27篇 |
1979年 | 23篇 |
1978年 | 26篇 |
1977年 | 78篇 |
1976年 | 152篇 |
1975年 | 24篇 |
1974年 | 21篇 |
1973年 | 17篇 |
1972年 | 9篇 |
排序方式: 共有4043条查询结果,搜索用时 5 毫秒
991.
992.
Business interests and agendas have been amongst the most influential drivers in the restructuring of the UK planning system over the past 30 years. Yet questions regarding the nature of business and business agendas and the power and influence of business interests have been somewhat under-developed in recent planning theory. In this paper we adopt a distinctive approach to theorizing business interest representation and business–state relations based on a strategic-relational approach. This seeks to establish an explicit focus on the dynamics of business–state relations, a standpoint of particular salience to planning and planning theory. It also offers distinctive theoretical perspectives regarding questions of business power and the evaluation of business influence, as well as informing contemporary debates around the engagement of business in planning processes. These insights hold significant potential in extending understanding of governance dynamics and the realities of planning politics and practice. 相似文献
993.
Andrew Post T.Blaine Hoshizaki Michael D. Gilchrist Susan Brien Michael Cusimano Shawn Marshall 《Accident; analysis and prevention》2015
Traumatic brain injury (TBI) continues to be a leading cause of morbidity and mortality throughout the world. Research has been undertaken in order to better understand the characteristics of the injury event and measure the risk of injury to develop more effective environmental, technological, and clinical management strategies. This research used methods that have limited applications to predicting human responses. This limits the current understanding of the mechanisms of TBI in humans. As a result, the purpose of this research was to examine the characteristics of impact and dynamic response that leads to a high risk of sustaining a TBI in a human population. Twenty TBI events collected from hospital reports and eyewitness accounts were reconstructed in the laboratory using a combination of computational mechanics models and Hybrid III anthropometric dummy systems. All cases were falls, with an average impact velocity of approximately 4.0 m/s onto hard impact surfaces. The results of the methodology were consistent with current TBI research, describing TBI to occur in the range of 335–445 g linear accelerations and 23.7–51.2 krad/s2 angular accelerations. More significantly, this research demonstrated that lower responses in the antero-posterior direction can cause TBI, with lateral impact responses requiring larger magnitudes for the same types of brain lesions. This suggests an increased likelihood of sustaining TBI for impacts to the front or back of the head, a result that has implications affecting current understanding of the mechanisms of TBI and associated threshold parameters. 相似文献
994.
Web-based engagement is increasingly popular because of its perceived ability to increase access to the planning process with less effort than traditional methods. Currently, the utility of these approaches for meeting the needs of all members of a community is unclear. This research tests whether web-based engagement can forward equitable planning outcomes by examining proposed bikeshare station locations collected via a web-application; operationalizing equity as equal access to bikeshare station locations across all populations. Results indicate that solely relying upon online outreach would lead to an inequitable distribution of station locations. Suggested station locations are negatively-correlated with increased minority populations and positively-correlated with an increased mix of employment and housing. As such, we determine that while online outreach is a convenient and efficient means of collecting vast amounts of information, on its own it is not well-suited to planning applications in which access-equity is a primary concern. 相似文献
995.
Clifford A. Marshall 《Rocks & Minerals》2013,88(7-8):298-300
996.
Mungas Dan; Reed Bruce R.; Marshall Sarah C.; González Hector M. 《Canadian Metallurgical Quarterly》2000,14(2):209
Item response theory (IRT) methods were used to develop a neuropsychological test battery with matched English and Spanish language forms. Candidate items for 12 scales measuring core neuropsychological abilities were generated and administered to 200 community-dwelling elderly participants tested in Spanish and 208 tested in English. IRT methods were used to eliminate linguistically biased items and refine scales to assess broad ability ranges. Reasonably good psychometric matching of scales was achieved within and across English and Spanish language forms. All scales were sensitive to cognitive impairment as measured by the Mini-Mental State Examination (MMSE), with highly similar relationships between scale scores and MMSE across English and Spanish groups. The outcome supports the use of IRT methods in cross-cultural and multilingual test development and indicates that this strategy has potential for future neuropsychological test development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
997.
Elena S. George Skye Marshall Hannah L Mayr Gina L. Trakman Oana A. Tatucu-Babet Annie-Claude M. Lassemillante 《Critical reviews in food science and nutrition》2019,59(17):2772-2795
AbstractThe polyphenol fraction of extra-virgin olive oil may be partly responsible for its cardioprotective effects. The aim of this systematic review and meta-analysis was to evaluate the effect of high versus low polyphenol olive oil on cardiovascular disease (CVD) risk factors in clinical trials. In accordance with PRISMA guidelines, CINAHL, PubMed, Embase and Cochrane databases were systematically searched for relevant studies. Randomized controlled trials that investigated markers of CVD risk (e.g. outcomes related to cholesterol, inflammation, oxidative stress) were included. Risk of bias was assessed using the Jadad scale. A meta-analysis was conducted using clinical trial data with available CVD risk outcomes. Twenty-six studies were included. Compared to low polyphenol olive oil, high polyphenol olive oil significantly improved measures of malondialdehyde (MD: ?0.07µmol/L [95%CI: ?0.12, ?0.02µmol/L]; I2: 88%; p?=?0.004), oxidized LDL (SMD: ?0.44 [95%CI: ?0.78, ?0.10µmol/L]; I2: 41%; P?=?0.01), total cholesterol (MD 4.5 mg/dL [95%CI: ?6.54, ?2.39 mg/dL]; p<0.0001) and HDL cholesterol (MD 2.37 mg/dL [95%CI: 0.41, 5.04 mg/dL]; p?=?0.02). Subgroup analyses and individual studies reported additional improvements in inflammatory markers and blood pressure. Most studies were rated as having low-to-moderate risk of bias. High polyphenol oils confer some CVD-risk reduction benefits; however, further studies with longer duration and in non-Mediterranean populations are required. 相似文献
998.
999.
Transverse Thermal Conductivity of Thin C/SiC Composites Fabricated by Slurry Infiltration and Pyrolysis 总被引:1,自引:0,他引:1
Min Z. Berbon Donald R. Dietrich David B. Marshall D. P. H. Hasselman 《Journal of the American Ceramic Society》2001,84(10):2229-2234
Thin C/SiC composites were fabricated by infiltrating a woven carbon fiber fabric with a slurry of SiC powder and polymer precursor for SiC, followed by heat treatment for pyrolysis. The effects of heat treatment parameters on the crystallization of the polymer-derived SiC, the composite microstructure, and the transverse thermal properties were assessed. Whereas composites heat-treated at 1000°C were crack-free and nearly fully dense, composites that were subjected to further multiple reinfiltration and heat treatment cycles at 1600°C developed porosity and cracking. However, the transverse thermal conductivity was increased significantly by the higher-temperature heat treatment, to values higher than that of a composite with a chemical-vapor-infiltration SiC matrix and the same fiber reinforcement. 相似文献
1000.
Eric L. Johnson Tami S. Clabough Christopher A. Peery David H. Bennett Theodore C. Bjornn Christopher C. Caudill Marshall C. Richmond 《河流研究与利用》2007,23(9):963-978
Gas bubble disease (GBD) has been recognized as a potential problem for fishes in the Columbia River basin. GBD results from exposure to gas supersaturated water created by discharge over dam spillways. Spill creates a downstream plume of water with high total dissolved gas supersaturation (TDGS) that may be positioned along either shore or mid‐channel, depending on dam operations. We obtained spatial data on fish migration paths and migration depths for adult spring and summer Chinook salmon, Oncorhynchus tshawytscha, during 2000. Migration paths were compared to output from a two‐dimensional (2‐dimensional) hydrodynamic and dissolved gas model to estimate the potential for GBD expression and to test for behavioural avoidance of the high TDGS plume. We observed salmon swam sufficiently deep in the water column to receive complete hydrostatic compensation 95.9% of the time spent in the Bonneville Dam tailrace and 88.1% of the time in the Ice Harbor Dam tailrace. The majority of depth uncompensated exposure occurred at TDGS levels >115%. Adult Chinook salmon tended to migrate near the shoreline and they tended to remain in relatively deep water. Adults moved into the high dissolved‐gas plume as often as they moved out of it downstream of Bonneville Dam, providing no evidence that adults moved laterally to avoid areas with elevated dissolved gas levels. When water depths decreased due to reduced river discharge, adults tended to migrate in the deeper navigation channel downstream from Ice Harbor Dam. The strong influence of dam operations on the position of the high‐TDGS plume and shoreline‐orientation behaviours of adults suggest that exposure of adult salmonids to high‐TDGS conditions may be minimized using operational conditions that direct the spilled water mid‐channel. Our approach illustrates the potential for combined field and modelling efforts to estimate the fine‐scale environmental conditions encountered by fishes in natural and regulated rivers. Published in 2007 by John Wiley & Sons, Ltd. 相似文献