全文获取类型
收费全文 | 1444篇 |
免费 | 53篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 223篇 |
金属工艺 | 4篇 |
机械仪表 | 33篇 |
建筑科学 | 56篇 |
矿业工程 | 4篇 |
能源动力 | 21篇 |
轻工业 | 118篇 |
水利工程 | 19篇 |
石油天然气 | 3篇 |
无线电 | 152篇 |
一般工业技术 | 253篇 |
冶金工业 | 423篇 |
原子能技术 | 9篇 |
自动化技术 | 169篇 |
出版年
2023年 | 12篇 |
2022年 | 11篇 |
2021年 | 21篇 |
2020年 | 15篇 |
2019年 | 23篇 |
2018年 | 19篇 |
2017年 | 29篇 |
2016年 | 22篇 |
2015年 | 14篇 |
2014年 | 21篇 |
2013年 | 72篇 |
2012年 | 43篇 |
2011年 | 58篇 |
2010年 | 44篇 |
2009年 | 32篇 |
2008年 | 58篇 |
2007年 | 56篇 |
2006年 | 43篇 |
2005年 | 36篇 |
2004年 | 44篇 |
2003年 | 44篇 |
2002年 | 25篇 |
2001年 | 38篇 |
2000年 | 41篇 |
1999年 | 44篇 |
1998年 | 96篇 |
1997年 | 72篇 |
1996年 | 45篇 |
1995年 | 36篇 |
1994年 | 24篇 |
1993年 | 41篇 |
1992年 | 30篇 |
1991年 | 13篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 21篇 |
1987年 | 12篇 |
1986年 | 21篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 19篇 |
1977年 | 16篇 |
1976年 | 19篇 |
1975年 | 6篇 |
1974年 | 9篇 |
排序方式: 共有1499条查询结果,搜索用时 15 毫秒
51.
Getting off on the right foot: Subjective value versus economic value in predicting longitudinal job outcomes from job offer negotiations. 总被引:1,自引:0,他引:1
Curhan Jared R.; Elfenbein Hillary Anger; Kilduff Gavin J. 《Canadian Metallurgical Quarterly》2009,94(2):524
Although negotiation experiences can affect a negotiator's ensuing attitudes and behavior, little is known about their long-term consequences. Using a longitudinal survey design, the authors tested the degree to which economic and subjective value achieved in job offer negotiations predicts employees' subsequent job attitudes and intentions concerning turnover. Results indicate that subjective value predicts greater compensation satisfaction and job satisfaction and lower turnover intention measured 1 year later. Surprisingly, the economic outcomes that negotiators achieved had no apparent effects on these factors. Implications, limitations, and future directions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
52.
B. Elhweg I.W. Burns Y.M.J. Chew P.J. Martin A.B. Russell D.I. Wilson 《Food and Bioproducts Processing》2009,87(4):266-272
We have analysed sets of capillary rheometry data (0.3 s?1 ≤ γapp ≤ 360 s?1) for a commercial ice cream as it flowed from a freezer on an industrial flow line. Pressure drop measurements were used and particular attention was paid to viscous dissipation effects. A semi-analytical model presented by Bird in 1955 indicated that over one third of the data points were subject to local wall heating, which was consistent with available temperature measurements. The filtered data were used to construct a viscosity function which, when implemented in a detailed CFD simulation of the flow, predicted the observed flow curve behaviour. The results demonstrate that viscous dissipation can be significant in ice cream and that interpretation of this behaviour in terms of wall slip is erroneous. 相似文献
53.
Establishing Environmental Water Requirements for the Murray–Darling Basin,Australia's Largest Developed River System 下载免费PDF全文
J. L. Swirepik I. C. Burns F. J. Dyer I. A. Neave M. G. O'Brien G. M. Pryde R. M. Thompson 《河流研究与利用》2016,32(6):1153-1165
There is a global need for management of river flows to be informed by science to protect and restore biodiversity and ecological function while maintaining water supply for human needs. However, a lack of data at large scales presents a substantial challenge to developing a scientifically robust approach to flow management that can be applied at a basin and valley scale. In most large systems, only a small number of aquatic ecosystems have been well enough studied to reliably describe their environmental water requirements. The umbrella environmental asset (UEA) approach uses environmental water requirements developed for information‐rich areas to represent the water requirements of a broader river reach or valley. We illustrate this approach in the Murray–Darling Basin (MDB) in eastern Australia, which was recently subject to a substantial revision of water management arrangements. The MDB is more than 1 million km2 with 18 main river valleys and many thousands of aquatic ecosystems. Detailed eco‐hydrologic assessments of environmental water requirements that focused on the overbank, bankfull and fresh components of the flow regime were undertaken at a total of 24 UEA sites across the MDB. Flow needs (e.g. flow magnitude, duration, frequency and timing) were established for each UEA to meet the needs of key ecosystem components (e.g. vegetation, birds and fish). Those flow needs were then combined with other analyses to determine sustainable diversion limits across the basin. The UEA approach to identifying environmental water requirements is a robust, science‐based and fit‐for‐purpose approach to determining water requirements for large river basins in the absence of complete ecological knowledge. © 2015 The Authors. River Research and Applications published by John Wiley & Sons, Ltd. 相似文献
54.
Lyndsay A. Cartwright Sue Hayes Douglas C. Tozer Dan Clayton Mary-Ann Burns Dena Lewis Noah Gaetz Namrata Shrestha 《Journal of Great Lakes research》2021,47(2):273-282
Beneficial use impairments (BUIs) under the Great Lakes Water Quality Agreement identify environmental issues requiring remedial action within the Great Lakes Areas of Concern (AOCs). We conducted this study to support the assessment of the wildlife component of BUI 3: degradation of fish and wildlife populations. We compared bird and amphibian (frogs and toads) data from the Toronto and Region Conservation Authority’s Terrestrial Long-term Monitoring Program in the Toronto and Region AOC to an adjacent, but otherwise similar, reference watershed, Duffins Creek. Twelve of 13 targets were met within the AOC for forest bird, wetland bird, meadow bird and amphibian populations based on averages of mean annual values at sites within the AOC that were within two standard deviations of averages at sites in the Duffins Creek reference watershed between 2008 and 2017. Even though wildlife populations within the AOC were within the normal range of variability expected from a reference watershed, they were often at lower levels than within the Duffins Creek reference watershed. In addition, forest bird and amphibian populations were negatively affected by urbanization within the AOC and meadow bird indices declined. We conclude that while wildlife populations within the AOC currently meet targets for BUI 3, they continue to be negatively impacted by numerous stressors that are primarily related to past and ongoing urbanization. Thus, continued restoration of wildlife habitat and protection of existing habitat within the AOC is highly recommended. 相似文献
55.
In order to examine the behavior of incompatible blends of polystyrene and polybutadiene, the glass transition temperature, the melting point, and the specific heat increment at the glass transition temperature for atactic polystyrene (a-PS), isotactic polystyrene (i-PS), polybutadiene (PBD), and blends of a-PS/PBD and i-PS/PBD were determined by use of a differential scanning calorimeter. Blends were prepared by solution casting, freeze-drying, and milling. Weight fractions of polystyrene in the blends ranged from 0.95 to 0.05. The glass transition temperature of polystyrene changed with weight fraction in the blends, and with blending preparation methods; the glass transition temperature of polybutadiene remained essentially unchanged. The specific heat increment at the glass transition temperature of PBD decreases linearly with increasing proportions of PS in the PS/PBD blend for the broad and narrow molecular weight distribution polybutadience polymers, whereas the specific heat increment for PS did not decrease with increasing proportions of PBD in the PS/PBD blend. These results suggest that the polybutadiene dissolves more in the polystyrene phase than does the polystyrene in the polybutadiene phase. 相似文献
56.
Tristan F. Burns Kraft Barbara M. Schmidt G.G. Yousef Christopher T.G. Knight Muriel Cuendet Young-Hwa Kang John M. Pezzuto David S. Seigler Mary Ann Lila 《Journal of food science》2005,70(3):S159-S166
ABSTRACT: Wild lowbush blueberry fruit extract was fractionated using vacuum chromatography and analyzed for chemopreventive potential using bioassays that test the ability of compounds to inhibit the initiation, promotion, and progression stages of carcinogenesis. A fraction containing phytosterols was active against the initiation stage (quinone reductase assay). However, more polar compounds were inhibitors of later stages of carcinogenesis; a fraction containing flavan-3-ols and fractions containing mainly anthocyanins, phenolic acids, flavan-3-ols, and some proanthocyanidin dimers demonstrated activity against the promotion stage (cyclooxygenase and ornithine decarboxylase assays, respectively), and a proanthocyanidin-rich fraction demonstrated antiproliferation activity (inhibition of cancerous murine hepatocyte proliferation is associated with the progression stage). These results indicate that lowbush blueberries contain a range of compounds that have bioactivity against multiple stages of carcinogenesis, and different types of phenolic compounds are active at different stages. 相似文献
57.
Molt induction in lobsters (Homarus americanus) by intramuscular injection of ecdysterone triacetate
The principal component of the successful, molt-inducing ecdysterone acetate mixture was established as ecdysterone triacetate and shown to have the same activity as the acetate mixture. The triacetate induced ecdysis in male lobsters collected in winter and summer and in female lobsters collected in winter. Intramuscular injections of triacetate in ethanol were as effective as those with oil emulsions. 相似文献
58.
S.L. Gelsinger A.J. Heinrichs C.M. Jones R.J. Van Saun D.R. Wolfgang C.M. Burns H.R. Lysczek 《Journal of dairy science》2014
Ultraviolet light is being employed for bacterial inactivation in milk for calves; however, limited evidence is available to support the claim that UV light effectively inactivates bacteria found in milk. Thus, the objective of this observational study was to investigate the efficacy of on-farm UV light treatment in reducing bacteria populations in waste milk used for feeding calves. Samples of nonsaleable milk were collected from 9 Pennsylvania herds, twice daily for 15 d, both before and after UV light treatment (n = 60 samples per farm), and analyzed for standard plate count, coliforms, noncoliform, gram-negative bacteria, environmental and contagious streptococci, coagulase-negative staphylococci, Streptococcus agalactiae, Staphylococcus aureus count, and total solids percentage, and log reduction and percentage log reduction were calculated. Data were analyzed using the mixed procedure in SAS. In all bacteria types, samples collected after UV treatment contained significantly fewer bacteria compared with samples collected before UV treatment. Weighted least squares means for log reduction (percentage log reduction) were 1.34 (29%), 1.27 (58%), 1.48 (53%), 1.85 (55%), 1.37 (72%), 1.92 (63%), 1.07 (33%), and 1.67 (82%) for standard plate count, coliforms, noncoliform, gram-negative bacteria, environmental and contagious streptococci, Strep. agalactiae, coagulase-negative staphylococci, and Staph. aureus, respectively. A percentage log reduction greater than 50% was achieved in 6 of 8 bacteria types, and 43 and 94% of samples collected after UV treatment met recommended bacterial standards for milk for feeding calves. Based on these results, UV light treatment may be effective for some, but not all bacteria types found in nonsaleable waste milk. Thus, farmers should take into account the bacteria types that may need to be reduced when considering the purchase of a UV-treatment system. 相似文献
59.
60.
A novel scheme for performing infrared multiphoton dissociation (IRMPD) is presented in which a hollow fiber waveguide (HFWG) is used to transmit IR radiation into the ion storage region of a mass spectrometer. Efficient dissociation of oligonucleotide and protein ions is demonstrated on an ESI-FTICR instrument in which IRMPD is performed in the external ion reservoir and on a quadrupole ion trap. Using a simple optical scheme consisting of a single focusing lens and an x, y translator, the 10.6-microm IR laser beam, initially 3.5 mm in diameter, is focused into the vacuum-sealed HFWG. The small internal diameter and the high transfer efficiency of the waveguide allow IR radiation of high power density to be employed for IRMPD. In studies performed on a quadrupole ion trap, a 500-microm-i.d. waveguide was used as a medium to transmit IR radiation directly through a 700-microm orifice in the ring electrode. Efficient IRMPD of both a 12-mer oligonucleotide and the protein melittin were performed at laser powers of 0.5 and 3.2 W, respectively. 相似文献