全文获取类型
收费全文 | 1894篇 |
免费 | 75篇 |
国内免费 | 3篇 |
学科分类
工业技术 | 1972篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 63篇 |
2021年 | 63篇 |
2020年 | 29篇 |
2019年 | 47篇 |
2018年 | 57篇 |
2017年 | 44篇 |
2016年 | 50篇 |
2015年 | 51篇 |
2014年 | 58篇 |
2013年 | 104篇 |
2012年 | 104篇 |
2011年 | 158篇 |
2010年 | 127篇 |
2009年 | 98篇 |
2008年 | 133篇 |
2007年 | 113篇 |
2006年 | 75篇 |
2005年 | 69篇 |
2004年 | 61篇 |
2003年 | 43篇 |
2002年 | 50篇 |
2001年 | 42篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 24篇 |
1997年 | 22篇 |
1996年 | 31篇 |
1995年 | 21篇 |
1994年 | 23篇 |
1993年 | 20篇 |
1992年 | 17篇 |
1991年 | 2篇 |
1990年 | 17篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1972条查询结果,搜索用时 15 毫秒
81.
Vanessa Rose Gretchen Rollwagen‐Bollens Stephen M. Bollens Julie Zimmerman 《河流研究与利用》2019,35(9):1478-1488
Dams, increasingly common in riverine systems worldwide, are particularly prevalent on the Columbia River (CR) in the United States. Hydroelectric projects, including both storage and run‐of‐river (i.e., minimal storage) structures, on the mainstem CR highly manage water flow, often by releasing water over (rather than through) dams as “spill.” To test the effects of run‐of‐river dam spill on microplankton abundance and composition, we sampled above and below two dams in the lower CR before and during spill conditions in spring 2016 and during and after spill conditions in late summer 2007. We tested the effects of location (i.e., above vs. below dams), spill condition (i.e., before, during, and after spill), and their interaction on microplankton abundance. Generally, diatoms were most abundant during springtime, whereas cyanobacteria were most abundant in late summer. Most taxa were not significantly different in abundance above and below dams, regardless of spill status; although cyanobacteria abundance was marginally higher below dams in summer 2007 (p = .04). Abundances of all taxa were significantly different between pre‐spill and spill periods in spring 2016, whereas only diatom and flagellate abundances were significantly different between spill and post‐spill periods in summer 2007. We conclude that spill conditions may influence microplankton abundance, but are not likely to affect microplankton communities on either side of run‐of‐river dams on the CR. This is important information for dam managers concerned about ecosystem impacts of spill. 相似文献
82.
The use of manufacturing system reconfiguration in conjunction with maintenance operations has not been previously reported in the literature. This research attempts to incorporate reconfiguration into Preventive Maintenance (PM) actions for improved system performance in terms of reduced total cost. This paper presents an Integrated Reconfiguration and Age-Based Maintenance (IRABM) policy and applies it to a parallel-serial manufacturing system. The expected total cost of implementing the IRABM policy is estimated and minimized through a simulation-based heuristic optimization procedure. Using this method, it is possible to systematically identify the conditions under which the integration of reconfiguration into maintenance is cost effective. In addition, numerical examples demonstrate that the manufacturing system could have a higher probability of fulfilling production requirements at a lower cost under the IRABM policy compared to the conventional age-based PM policy. The influences of the input parameters associated with reconfiguration, production, and reliability on the performance of IRABM policy also are studied. 相似文献
83.
Planar laser polarization spectroscopy has recently been used to image the hydroxyl radical in combustion for small intersection angles of pump and probe beams. We report an experimental configuration that allows planar laser polarization imaging for perpendicular intersection of pump and probe beams. We demonstrate what to our knowledge is the first planar laser polarization spectroscopy imaging at a 90 degree intersection of pump and probe beams for both linearly and circularly polarized pump beams. 相似文献
84.
Dark-capacitance transients in MIS tunnel diodes switched from accumulation to deep depletion depend on the interface state occupancy. This time dependent function is derived and its behavior described for electron emission and electron-hole pair generation with tunneling and thermally controlled occupancies. A new method of determining the tunneling relaxation time constant τT from the electron emission transient at low temperature is described. Measurements of MIS tunnel diodes with oxide thickness dox = 17 to 80 Å agree with theory and the resultant values of τT compare with previously reported results from photocapacitance[2]. 相似文献
85.
Magat Julie Ozenne Valéry Cedilnik Nicolas Naulin Jérôme Haliot Kylian Sermesant Maxime Gilbert Stephen H. Trew Mark Haissaguerre Michel Quesson Bruno Bernus Olivier 《Magma (New York, N.Y.)》2021,34(5):741-755
Magnetic Resonance Materials in Physics, Biology and Medicine - The aim of the study is to compare structure tensor imaging (STI) with diffusion tensor imaging (DTI) of the sheep heart... 相似文献
86.
Rachael Jaenke Federica Barzi Emma McMahon Jacqui Webster Julie Brimblecombe 《Critical reviews in food science and nutrition》2017,57(16):3357-3372
Food product reformulation is promoted as an effective strategy to reduce population salt intake and address the associated burden of chronic disease. Salt has a number of functions in food processing, including impacting upon physical and sensory properties. Manufacturers must ensure that reformulation of foods to reduce salt does not compromise consumer acceptability.The aim of this systematic review is to determine to what extent foods can be reduced in salt without detrimental effect on consumer acceptability.Fifty studies reported on salt reduction, replacement or compensation in processed meats, breads, cheeses, soups, and miscellaneous products. For each product category, levels of salt reduction were collapsed into four groups: <40%, 40–59%, 60–79% and ≥80%. Random effects meta-analyses conducted on salt-reduced products showed that salt could be reduced by approximately 40% in breads [mean change in acceptability for reduction <40% (?0.27, 95% confidence interval (CI) ?0.62, 0.08; p = 0.13)] and approximately 70% in processed meats [mean change in acceptability for reductions 60–69% (?0.18, 95% CI ?0.44, 0.07; p = 0.15)] without significantly impacting consumer acceptability. Results varied for other products.These results will support manufacturers to make greater reductions in salt when reformulating food products, which in turn will contribute to a healthier food supply. 相似文献
87.
Julie Babyar 《Drug development and industrial pharmacy》2018,44(11):1868-1870
Substandard, falsified, and counterfeit medications are a concern for the industry and for the public’s health. Data collection and research on these illegitimate drugs must continue to be a priority and common recommendations must be implemented immediately. The health of the public continues to be at risk, and as such global consensus and collaboration must be swift. Process improvements and policy decisions can support expert recommendations while technology and research continue to drive home change. Addressing counterfeit and substandard drugs is cost effective, feasible, and the right thing to do. 相似文献
88.
Christopher Peacock-McLaughlin Peter S. Wlyudka Tammie M. Johnson Julie W. Merten 《Urban Research & Practice》2018,11(3):193-199
This preliminary study assesses the relationship between active transportation, the built environment, and population perceived health in two comparable cities in the Southeastern United States at different stages of improving infrastructure for active commuting. Behavioral Risk Factor Surveillance Survey data from 2006 to 2012 were analyzed for Charlotte, NC, and Jacksonville, FL. The annual difference between the percentage of Charlotte respondents rating physical health as good compared to Jacksonville’s increased at a rate of 13% based on an exponential growth regression model (p = 0.02). Supportive urban and transportation policies aimed at facilitating healthy behaviors are associated with healthier communities. 相似文献
89.
90.