全文获取类型
收费全文 | 974篇 |
免费 | 17篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 12篇 |
综合类 | 28篇 |
化学工业 | 202篇 |
金属工艺 | 16篇 |
机械仪表 | 29篇 |
建筑科学 | 77篇 |
矿业工程 | 18篇 |
能源动力 | 81篇 |
轻工业 | 109篇 |
水利工程 | 3篇 |
石油天然气 | 16篇 |
无线电 | 79篇 |
一般工业技术 | 263篇 |
冶金工业 | 41篇 |
原子能技术 | 10篇 |
自动化技术 | 16篇 |
出版年
2023年 | 8篇 |
2022年 | 14篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 16篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 26篇 |
2013年 | 46篇 |
2012年 | 54篇 |
2011年 | 90篇 |
2010年 | 47篇 |
2009年 | 81篇 |
2008年 | 64篇 |
2007年 | 79篇 |
2006年 | 62篇 |
2005年 | 46篇 |
2004年 | 47篇 |
2003年 | 45篇 |
2002年 | 26篇 |
2001年 | 18篇 |
2000年 | 34篇 |
1999年 | 26篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 7篇 |
1994年 | 14篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有1000条查询结果,搜索用时 15 毫秒
81.
Hong Seok Lee Armando RastelliTae Whan Kim Hong Lee ParkOliver G. Schmidt 《Thin solid films》2011,519(19):6554-6556
Microphotoluminescence (μ-PL) measurements were carried out to investigate the optical properties of single Cd0.6Zn0.4Te/ZnTe quantum dots (QDs) grown on Si (001) substrate by using molecular beam epitaxy. The high quality of single Cd0.6Zn0.4Te/ZnTe QDs is witnessed by resolution-limited emission, negligible background and absence of measurable spectral jitter or blinking. Polarization-dependent and power-dependent μ-PL spectroscopy measurements were performed to identify the exciton, the biexciton, and the charged exciton in the emission spectra of single QDs. Furthermore a weak linearly polarized line is observed on the low energy side of the neutral exciton and is ascribed to dark exciton recombination. 相似文献
82.
A sensitivity analysis was conducted on an in vitro gastrointestinal digestion test (i) to investigate the influence of a low variation of gastric juice pH on the bioaccessibility of Cd and Pb in smelter-contaminated soils (FB, using the unified bioaccessibility method UBM) and fractions of metals that may be transported across the intestinal epithelium (FA, using the diffusive gradient in thin film technique), and (ii) to provide a better understanding of the significance of pH in health risk assessment through ingestion of soil by children. The risk of metal exposure to children (hazard quotient, HQ) was determined for conditions that represent a worst-case scenario (i.e., ingestion rate of 200 mg day− 1) using three separate calculations of metal daily intake: estimated daily intake (EDI), bioaccessible EDI (EDI-FB), and oral bioavailable EDI (EDI-FA). The increasing pH from 1.2 to 1.7 resulted in: (i) no significant variation in Cd-FB in the gastric phase but a decrease in the gastrointestinal phase; (ii) a decrease in soluble Pb in the gastric phase and a significant variation in Pb-FB in the gastrointestinal phase; (iii) a significant decrease in Cd-FA and no variation in Pb-FA; (iv) no change in EDI-FB and EDI-FA HQs for Cd; (v) a significant decrease in EDI-FB HQs and no significant variation in EDI-FA HQ for Pb. In the analytical conditions, these results show that risk to children decreases when the bioavailability of Pb in soils is taken into account and that the studied pH values do not affect the EDI-FA HQs. The present results provide evidence that the inclusion of bioavailability analysis during health risk assessment could provide a more realistic estimate of Cd and Pb exposure, and opens a wide field of practical research on this topic (e.g., in contaminated site management). 相似文献
83.
84.
以幼龄鲫鱼 (carassiusauratus)为研究对象 ,研究在镉离子低浓度 ( 0 .0 1mg/l)暴露下 ,其肝脏中抗氧化系统 (过氧化氢酶 (CAT) ,超氧化物歧化酶 (SOD) ,谷胱甘肽还原硫转移酶 (GST)的活性 ) ,随暴露时间 ( 0天 ,1天 ,2天 ,4天 ,8天 ,2 0天 ,3 2天 ,5 0天 )的变化趋势。在本实验中 ,SOD活性始终被抑制 ,而CAT和GST活性则先被激活后被抑制。GST活性在第一天时就达到最大值 ,而CAT则在前四天不断被激活 ,然后又被显著抑制。这三种酶对镉暴露的敏感性顺序为SOD >GST >CAT。其中SOD最为敏感 ,是一种很有前途的水生生态系统中镉离子的生物标志物 相似文献
85.
Direct determination of copper,lead and cadmium in aniseed spirits by electrothermal atomic absorption spectrometry 总被引:1,自引:0,他引:1
J.M. Jurado M.J. Martín F. Pablos A. Moreda-Piñeiro P. Bermejo-Barrera 《Food chemistry》2007,101(3):1296-1304
Direct determination of copper, lead and cadmium by electrothermal atomic absorption spectrometry in aniseed spirits was proposed. The methods were validated by studying quality parameters such as trueness, precision, linearity and sensitivity. Recoveries ranging between 96% and 104% were obtained from spiked samples at several concentration levels. Repeatability was less than 5% and intermediate precision was less than 8%. The procedure is fast and shows limits of detection of 0.6, 0.7 and 0.04 μg l−1 for Cu, Pb and Cd, respectively. Samples were just diluted in a water/ethanol/nitric acid mixture. Cu was present at higher concentrations, with values in the range 6–473 μg l−1. Minor levels of Pb and Cd were present with concentrations of less than 6 and 1.4 μg l−1, respectively. 相似文献
86.
目的 抽测2018-2020年北京市售蟹类中镉含量并进行评价,为蟹类的质量安全性评价提供基础数据.方法 采用随机采样的方法,采集北京市售常见蟹类,采用原子吸收光谱法对蟹中的镉含量进行检测;采用靶标危害系数法(THQ)评估人体每日通过蟹类摄入重金属所带来的健康风险.结果 2018-2020年共采集蟹类样品83份,重金属镉... 相似文献
87.
88.
载镉废啤酒酵母中金属镉的回收 总被引:2,自引:0,他引:2
以水洗废啤酒酵母为吸附剂,对废水中镉离子进行生物吸附及固液分离后,获得载镉废啤酒酵母。采用焙烧-酸浸-置换法回收"载镉菌体上的镉",在700℃焙烧24 h,菌渣中镉富集比为31.72,烧渣经15 g/L的硫酸、温度85℃条件下,浸出2 h,再用锌粒置换,得海绵镉,镉总回收率在98%以上。 相似文献
89.
碲锌镉晶片的机械化学磨抛分析 总被引:1,自引:0,他引:1
对<111>方向的三块碲锌镉晶片进行了不同的机械磨抛、化学机械抛光、化学抛光,在相同的测量条件下用三维形貌干涉仪进行表面监测.比较了碲锌镉晶片不同的磨抛方法对碲锌镉晶片表面机械损伤的情况,开展了碲锌镉晶片不同的磨抛方法对损伤的去除程度的对比实验,进行了碲锌镉晶片表面粗糙度及平整度实现的研究. 相似文献
90.
Lifei Xi Winnie Xiu Wen Tan Kee Sze Chua Chris Boothroyd Yeng Ming Lam 《Thin solid films》2009,517(23):6430-2525
Cadmium sulphide (CdS) nanowires with a monodisperse diameter of 3.6 nm and an aspect ratio of 10–170 were successfully synthesized using a simple and reproducible hot coordinating solvents method. The morphology and optical properties of the CdS nanocrystals were investigated using transmission electron microscopy (TEM), high-resolution TEM (HRTEM) ultraviolet–visible (UV–Vis) absorption spectroscopy and photoluminescence (PL) spectroscopy. It was found that using a long alkyl chain phosphonic acid-octadecylphosphonic acid (ODPA) causes a low diffusion rate and low reactivity which help to control the morphology of the nanocrystals. The timing of the injection process was also found to have critical effect on the morphology of the nanocrystals. Sharp peaks in both the UV–Vis absorption and PL spectra indicate that the size distribution of the diameter is nearly monodisperse. The photovoltaic properties of photovoltaic devices made with a blend of our nanowires and poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) were also investigated. Devices made with the nanowires were found to have double the Isc observed in devices made with lower aspect ratio CdS nanorods. The possible reason of low photocurrent and high Voc is maybe due to the presence of ligand in the nanocrystals. 相似文献