全文获取类型
收费全文 | 1356篇 |
免费 | 40篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 14篇 |
综合类 | 9篇 |
化学工业 | 171篇 |
金属工艺 | 113篇 |
机械仪表 | 28篇 |
建筑科学 | 63篇 |
矿业工程 | 9篇 |
能源动力 | 18篇 |
轻工业 | 146篇 |
水利工程 | 4篇 |
石油天然气 | 8篇 |
无线电 | 156篇 |
一般工业技术 | 197篇 |
冶金工业 | 179篇 |
原子能技术 | 6篇 |
自动化技术 | 278篇 |
出版年
2022年 | 6篇 |
2021年 | 14篇 |
2020年 | 11篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 27篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 34篇 |
2013年 | 79篇 |
2012年 | 52篇 |
2011年 | 73篇 |
2010年 | 65篇 |
2009年 | 74篇 |
2008年 | 86篇 |
2007年 | 80篇 |
2006年 | 78篇 |
2005年 | 75篇 |
2004年 | 54篇 |
2003年 | 67篇 |
2002年 | 55篇 |
2001年 | 24篇 |
2000年 | 23篇 |
1999年 | 27篇 |
1998年 | 24篇 |
1997年 | 24篇 |
1996年 | 31篇 |
1995年 | 39篇 |
1994年 | 19篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1970年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有1399条查询结果,搜索用时 15 毫秒
111.
This bench-scale study investigated the passage of particle-associated bacteriophage through a dual-media (anthracite-sand) filter over a complete filter cycle and the effect on subsequent ultraviolet (UV) disinfection. Two model viruses, bacteriophages MS2 and T4, were considered. The water matrix was de-chlorinated tap water with either kaolin or Aldrich humic acid (AHA) added and coagulated with alum to form floc before filtration. The turbidity of the influent flocculated water was 6.4+/-1.5 NTU. Influent and filter effluent turbidity and particle counts were measured as well as headloss across the filter media. Filter effluent samples were collected for phage enumeration during three filter cycle stages: (i) filter ripening; (ii) stable operation; and (iii) end of filter cycle. Stable filter operation was defined according to a filter effluent turbidity goal of <0.3 NTU. Influent and filter effluent samples were subsequently exposed to UV light (254 nm) at 40 mJ/cm(2) using a low pressure UV collimated beam. The study found statistically significant differences (alpha=0.05) in the quantity of particle-associated phage present in the filter effluent during the three stages of filtration. There was reduced UV disinfection efficiency due to the presence of particle-associated phage in the filter effluent in trials with bacteriophage MS2 and humic acid floc. Unfiltered influent water samples also resulted in reduced UV inactivation of phage relative to particle-free control conditions for both phages. Trends in filter effluent turbidity corresponded with breakthrough of particle-associated phage in the filter effluent. The results therefore suggest that maintenance of optimum filtration conditions upstream of UV disinfection is a critical barrier to particle-associated viruses. 相似文献
112.
Herd-years of Israeli-Holsteins were stratified into three groups by two criteria: mean annualized milk yield [365 (total lactations yield/calving interval)] and mean persistency, estimated as the ratio of daily milk production at the 5th mo postpartum to daily production during the postpartum peak period. The latter was taken as an indication of the relative environmental stress on the cow. Primi- and multiparous cows were analyzed separately. Genetic parameters were estimated for annualized milk and fat production at each production and persistency group. Heritabilities increased with a rise in production for both primiparous and multiparous cows, but the effect was greater for multiparous cows. Even though persistency and production were correlated, no clear trends were evident for stratification by persistency; thus, a relationship between stress and heritability was not established. Genetic correlations among stratification groups were between .7 and .9 for persistency and between .6 and .86 for production; thus, sire x environmental interaction was greater for production than for persistency stratification. Production in a given year can be used as a criterion for selecting herds to test progeny of young sires in the following year. 相似文献
113.
A small commercially available laboratory mill was found to be suitable to dehull small batches of sorghum grain. The device used one grinding plate and an agitating dimpled plate and took about 1 min to adequately dehull the grain. At the completion of dehulling period decorticated grain was collected directly in a sample holder. Data from various cultivars, grain sizes and types of grain were reproducible. It only required 10 s to clear the device between samples. 相似文献
114.
115.
Pandanus conoideus fruit contained 19.4% by dry weight of red fat. Major fatty acids contained in the fat were oleic (67.6% of the total fatty acids), palmitic (18.7%) and linoleic (7.6%) acids. The fat had an unusually high level of free fatty acid (90.0%) which may have resulted from the action of fat splitting enzymes. 相似文献
116.
117.
Z. Grubač M. Metikoš-Huković R. Babić I. Škugor Rončević M. Petravić R. Peter 《Materials science & engineering. C, Materials for biological applications》2013,33(4):2152-2158
Mg and Mg-alloys are promising materials for biodegradable implants. In order to slowdown the Mg-alloy (AZ91D) degradation and enhance its biocompatibility, the alloy surface was modified with alkylphosphonate self-assembling films. The binding configuration and the structural organization of alkylphosphonate monolayers on the Mg-alloy surface were investigated using contact angle measurements, FTIR, and XPS. Combination of FTIR and XPS data indicated the presence of several different bonding modes (mono-, di-, and tri dentate) of phosphonate head groups with the alloy surface. The existence of well organized and ordered self-assembled alkylphosphonate monolayers with good barrier protecting properties in a physiological solution is a key step in the development of biocompatible Mg-alloy implants. 相似文献
118.
Golsa Samii-Saket Jeffrey G. Boersma Gary R. Ablett Duane E. Falk Ron Fletcher Istvan Rajcan 《Journal of the American Oil Chemists' Society》2011,88(11):1795-1798
Development of high oil soybeans would reduce the cost of soybean oil production for biodiesel or edible oil applications.
An accurate determination of soybean seed oil concentration is essential especially when developing superior cultivars with
increased seed oil content. The objective of this study was to develop an oil measurement method for single seeds using NMR
spectrometry. An NMR spectrometer was calibrated using commercial cooking oil. Fifteen cultivars of known mean oil content
were used to evaluate the calibration curves. The calibration curves developed had a correlation coefficient of 0.99. It was
found that soybean and corn oil gave identical results over the calibrated interval. 相似文献
119.
Ilya Frisman Ron Orbach Dror Seliktar Havazelet Bianco-Peled 《Journal of materials science. Materials in medicine》2010,21(1):73-80
Controllable bio-synthetic polymeric hydrogels made from fibrinogen-poly(ethylene glycol) adducts have been successfully employed in tissue engineering. The structural consequences of PEG conjugation to fibrinogen (i.e., PEGylation) in such a hydrogel network are not fully understood. The current investigation details the structural alterations caused to the reduced fibrinogen polypeptides by the covalent attachment of linear or branched PEG chains. The structure of PEGylated fibrinogen polypeptides were comprehensively characterized using small angle X-ray scattering, light scattering, and cryo-transmission electron microscopy. These characterizations concur that the bio-synthetic hybrids self-assemble into elongated objects, having a protein core of about 50 Å in diameter decorated with multiple PEG chains. Conjugates with branched PEG chains were shorter, and have lower average molecular weight compared to conjugates with linear chains. The diameter of the protein core of both samples was similar, suggesting a tail-to-head aggregation of the PEGylated fibrinogen polypeptide. A more complete understanding of this unique structural arrangement can provide further insight into the full extent of biofunctional accessibility in a biomaterial that combines the advantages of synthetic polymers with bioactive proteins. 相似文献
120.
Because digital media management and distribution technologies face some of the same challenges that e-Science aims to address, this technology is a viable solution to meet the broadcasting domain's rigorous demands. 相似文献