全文获取类型
收费全文 | 1806篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 30篇 |
金属工艺 | 4篇 |
机械仪表 | 7篇 |
建筑科学 | 9篇 |
矿业工程 | 12篇 |
能源动力 | 5篇 |
轻工业 | 17篇 |
水利工程 | 1篇 |
无线电 | 33篇 |
一般工业技术 | 32篇 |
冶金工业 | 1614篇 |
原子能技术 | 2篇 |
自动化技术 | 49篇 |
出版年
2022年 | 3篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2013年 | 20篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 9篇 |
2007年 | 11篇 |
2006年 | 6篇 |
2005年 | 9篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 57篇 |
1998年 | 451篇 |
1997年 | 295篇 |
1996年 | 199篇 |
1995年 | 108篇 |
1994年 | 84篇 |
1993年 | 99篇 |
1992年 | 11篇 |
1991年 | 26篇 |
1990年 | 26篇 |
1989年 | 17篇 |
1988年 | 19篇 |
1987年 | 12篇 |
1986年 | 17篇 |
1985年 | 25篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 17篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 57篇 |
1976年 | 89篇 |
1975年 | 6篇 |
1970年 | 2篇 |
1960年 | 1篇 |
1955年 | 1篇 |
1947年 | 1篇 |
1946年 | 1篇 |
排序方式: 共有1816条查询结果,搜索用时 15 毫秒
101.
H Chao ME Houston RS Hodges CM Kay BD Sykes MC Loewen PL Davies FD S?nnichsen 《Canadian Metallurgical Quarterly》1997,36(48):14652-14660
The most abundant isoform (HPLC-6) of type I antifreeze protein (AFP1) in winter flounder is a 37-amino-acid-long, alanine-rich, alpha-helical peptide, containing four Thr spaced 11 amino acids apart. It is generally assumed that HPLC-6 binds ice through a hydrogen-bonding match between the Thr and neighboring Asx residues to oxygens atoms on the {2021} plane of the ice lattice. The result is a lowering of the nonequilibrium freezing point below the melting point (thermal hysteresis). HPLC-6, and two variants in which the central two Thr were replaced with either Ser or Val, were synthesized. The Ser variant was virtually inactive, while only a minor loss of activity was observed in the Val variant. CD, ultracentrifugation, and NMR studies indicated no significant structural changes or aggregation of the variants compared to HPLC-6. These results call into question the role of hydrogen bonds and suggest a much more significant role for entropic effects and van der Waals interactions in binding AFP to ice. 相似文献
102.
103.
104.
105.
106.
107.
108.
109.
Elizabeth Hodges Snyder George A. O'Connor 《The Science of the total environment》2010,408(13):2726-2732
Triclocarban (TCC) is an antibacterial compound commonly detected in biosolids at parts-per-million concentrations. Approximately half of the biosolids produced in the United States are land-applied, resulting in a systematic release of TCC into the soil environment. The extent of biosolids-borne TCC environmental transport and potential human/ecological exposures will be greatly affected by its bioavailability and the rate of degradation in amended soils. To investigate these factors, radiolabeled TCC (14C-TCC) was incorporated into anaerobically digested biosolids, amended to two soils, and incubated under aerobic conditions. The evolution of 14CO2 (biodegradation) and changes in chemical extractability (bioavailability) was measured over time. Water extractable TCC over the study period was low and significantly decreased over the first 3 weeks of the study (from 14% to 4% in a fine sand soil and from 3 to < 1% in a silty clay loam soil). Mineralization (i.e. ultimate degradation), as measured by evolution of 14CO2, was < 4% over 7.5 months. Methanol extracts of the amended soils were analyzed by radiolabel thin-layer chromatography (RAD-TLC), but no intermediate degradation products were detected. Approximately 20% and 50% of the radioactivity in the amended fine sand and silty clay loam soils, respectively, was converted to bound residue as measured by solids combustion. These results indicate that biosolids-borne TCC becomes less bioavailable over time and biodegrades at a very slow rate. 相似文献
110.
Elizabeth Hodges Snyder George A. O'Connor 《The Science of the total environment》2010,408(13):2667-5552
Triclocarban (TCC) is an active ingredient in antibacterial bar soaps, a common constituent of domestic wastewater, and the subject of recent criticism by consumer advocate groups and academic researchers alike. Activated sludge treatment readily removes TCC from the liquid waste stream and concentrates the antimicrobial in the solid fraction, which is often processed to produce biosolids intended for land application. Greater than half of the biosolids generated in the US are land-applied, resulting in a systematic release of biosolids-borne TCC into the terrestrial and, potentially, the aquatic environment. Multiple data gaps in the TCC literature (including basic physicochemical properties and biosolids concentrations) prevent an accurate, quantitative risk assessment of biosolids-borne TCC. We utilized the USEPA Office of Prevention, Pesticides, and Toxic Substances (OPPTS) harmonized test guidelines to measure TCC solubility and log Kow values as 0.045 mg L−1 and 3.5, respectively. The measured physicochemical 2 properties differed from computer model predictions. The mean concentration of TCC in 23 biosolids representative of multiple sludge processing methods was 19 ± 11 mg kg−1. 相似文献