全文获取类型
收费全文 | 1448篇 |
免费 | 43篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 98篇 |
综合类 | 4篇 |
化学工业 | 402篇 |
金属工艺 | 63篇 |
机械仪表 | 42篇 |
建筑科学 | 39篇 |
能源动力 | 57篇 |
轻工业 | 123篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
无线电 | 83篇 |
一般工业技术 | 294篇 |
冶金工业 | 116篇 |
原子能技术 | 38篇 |
自动化技术 | 135篇 |
出版年
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 35篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 31篇 |
2017年 | 19篇 |
2016年 | 33篇 |
2015年 | 27篇 |
2014年 | 53篇 |
2013年 | 88篇 |
2012年 | 73篇 |
2011年 | 117篇 |
2010年 | 64篇 |
2009年 | 78篇 |
2008年 | 87篇 |
2007年 | 78篇 |
2006年 | 52篇 |
2005年 | 64篇 |
2004年 | 60篇 |
2003年 | 46篇 |
2002年 | 35篇 |
2001年 | 41篇 |
2000年 | 21篇 |
1999年 | 25篇 |
1998年 | 36篇 |
1997年 | 33篇 |
1996年 | 20篇 |
1995年 | 18篇 |
1994年 | 26篇 |
1993年 | 23篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 15篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有1501条查询结果,搜索用时 15 毫秒
51.
Saka M Iijima K Nishida M Koma Y Hasegawa N Sato K Kato Y 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2008,49(3):160-167
The effects of processing and cooking on the levels of pesticide residues in soybean samples were investigated for 14 pesticides in pre-harvest samples. On soaking, the transfer ratios (%, total pesticide residue amount in product/that in soybean) of soaked soybean were greater than 60% for most of the pesticides investigated. The transfer ratio of soymilk ranged from 37% to 92%, and that of tofu ranged from 7% to 63%. The processing factor (Pf, the concentration (mg/kg) of pesticide in product/that in soybean) of tofu ranged from 0.026 to 0.28. These values varied among pesticides. There was a high correlation between the log P(ow) and the transfer ratio of tofu. The test described here should be useful to obtain the transfer ratios of pesticide residues in processing and/or cooking steps. 相似文献
52.
This article illustrates two types of organofunctionalized heterogeneous catalysts for variety of organic carbon–carbon bond-forming reactions, summarizing our previous reports and also presenting new data. Organic amines with an alkoxysilane moiety were immobilized on inorganic silica-alumina surfaces (SA-NR2) by simple silane-coupling reactions between the silica-alumina surface (SA) and the alkoxysilane. This SA-NR2 acted as acid–base bifunctional heterogeneous catalysts for carbon–carbon bond-forming reactions, such as cyano-ethoxycarbonylation, Michael reaction of nitriles, and nitro-aldol reaction. These reactions did not occur with either SA or homogeneous amine compounds. In addition, the mixture of SA and homogeneous amine showed low catalytic activity due to undesirable acid–base neutralization reaction. Achiral organic silane-coupling reagents with a variety of functional groups were also immobilized on a SiO2 surface that had been immobilized with chiral bis(oxazoline) (BOX), to which Cu ions were coordinated to make chiral Cu–BOX complexes on the SiO2 surface. The SiO2-supported Cu–BOX complex catalyst functionalized with achiral 3-methacryloxypropyltrimethoxysilane dramatically increased enantioselectivity in the asymmetric Diels–Alder reaction of cyclopentadiene and 3-acryloyl-2-oxazolidinone. The organofunctionalized catalysts showed much better performances for the C–C bond-forming reactions compared to the corresponding homogeneous systems. The heterogeneous catalysts thus obtained were characterized by solid-state 13C and 29Si MAS NMR, FT-IR, UV/vis, XAFS, ESR, XRF, and elemental analysis. 相似文献
53.
Seiichi Takami Yasuhiro Shirai Toyohiro Chikyow Yutaka Wakayama 《Thin solid films》2009,518(2):692-694
We have proposed the synthesis of organic molecular nanowires using porous alumina as a template. We also proposed the use of a magnetic field to control the molecular packing structure in the nanowires. In this paper, we developed the method to evaluate the electronic properties of the nanowire of a phthalocyanine derivative that was synthesized using porous alumina as a template. The developed method facilitates the study in the organic molecular nanowires that were synthesized using templates and helps their use in future electronic devices. 相似文献
54.
The composites of polyacrylates and eutectic metal alloy composed by Bi, In, and Sn were prepared by mixing the metal and polymer above the melting point of the metal alloy (80 °C) with a homogenizer. Two melting peaks, which were assigned as the melting peak of the original metal alloy and that of the interfacial phase of the metal alloy interacting with polyacrylates (70 °C) by differential scanning calorimetry. Metal particles with the diameter of about 100 nm which were stabilized by the interfacial interaction with polyacrylates were observed by transmission electron microscopy. The melting peak at 70 °C was assigned as the melting peak of these small particles. 相似文献
55.
Koh Matsumoto Kazutada Ikenaga Jun Yamamoto Kazuki Naito Yoshiki Yano Akinori Ubukata Hiroki Tokunaga Tadanobu Arimura Katsuaki Cho Toshiya Tabuchi Akira Yamaguchi Yasuhiro Harada Yuzaburo Ban Kousuke Uchiyama 《半导体学报》2011,32(1):21-23
Growth rate has a direct impact on the productivity of nitride LED production.Atmospheric pressure growth of GaN with a growth rate as high as 10μm/h and also Al0.1Ga0.9N growth of 1μm/h by using 4 inch by 11 production scale MOVPE are described.XRD of(002) and(102) direction was 200 arcsec and 250 arcsec, respectively.Impact of the growth rate on productivity is discussed. 相似文献
56.
57.
Hitoshi WADA Yasuhiro NISHISAKA Ryoichi ICHINO Masazumi OKIDO 《中国有色金属学会会刊》2009,19(4):791-794
The relatively uniform bismuth-copper film was electrodeposited between −15 and −20 mV in the sulfate electrolyte containing 4 mmol/L bismuth ion and 2 mmol/L copper ion. Only copper was electrodeposited at −5 mV. The dendritic bismuth-copper film was electrodeposited under −20 mV. The cathodic current became constant between −20 and −400 mV. Therefore, bismuth-copper electrodeposition changes from charge transfer controlling to diffusion controlling at −20 mV. On the other hand, the uniform bismuth-copper film was electrodeposited between −5 and −35 mV in the methanesulfonate electrolyte containing 4 mmol/L bismuth ion and 2 mmol/L copper ion. The dendritic bismuth-copper film was electrodeposited under −35 mV. The potential region for good electrodepositon in methanesulfonate electrolyte is wider than that in sulfate electrolyte. Therefore, it is easy to control electrodeposition conditions by using methanesulfonate electrolyte. 相似文献
58.
Kaoru Abe Yasuhiro Sakurai Akira Okuyama Kazuhiro Sasaki Kei Tawarada 《Journal of the science of food and agriculture》2009,89(6):1097-1100
BACKGROUND: The behavior of cadmium in ecosystems needs to be monitored because of the human toxicity of this heavy metal. The need recently arose for a simple and quick on‐site test for trace levels of Cd in food and environmental samples. In response, an immunochromatographic assay kit for detecting Cd was manufactured by Kansai Electric Power Co. of Japan. This kit uses the antigen–antibody complex reaction between the Cd–EDTA complex and an anti‐Cd–EDTA antibody and shows the results in terms of the degree of color developed on a test paper. We previously reported the successful use of this kit to determine Cd concentrations in brown rice. Here, we applied the kit to the determination of Cd concentrations in rice foliage and soil. RESULTS: Cadmium in rice foliage was not extracted successfully by the method used for brown rice. However, it was successfully extracted by 0.1 mol L?1 HCl solution at a rice foliage:HCl ratio of 1:20, and coexisting metals were removed sufficiently by the column treatment. The Cd concentrations determined by immunochromatographic assay were well correlated with the values obtained by acid decomposition and inductively coupled plasma mass spectrometry. The 0.1 mol L?1 HCl‐extractable Cd concentration in soil was also determined successfully with the kit. CONCLUSION: Approximate Cd concentrations in rice plants and 0.1 mol L?1 HCl‐extractable Cd concentrations in soil can be monitored easily and quickly by this method at locations where facilities for acid digestion and precision analysis are not available. Copyright © 2009 Society of Chemical Industry 相似文献
59.
Some approximate indexing schemes have been recently proposed in metric spaces which sort the objects in the database according to pseudo-scores. It is known that (1) some of them provide a very good trade-off between response time and accuracy, and (2) probability-based pseudo-scores can provide an optimal trade-off in range queries if the probabilities are correctly estimated. Based on these facts, we propose a probabilistic enhancement scheme which can be applied to any pseudo-score based scheme. Our scheme computes probability-based pseudo-scores using pseudo-scores obtained from a pseudo-score based scheme. In order to estimate the probability-based pseudo-scores, we use the object-specific parameters in logistic regression and learn the parameters using MAP (Maximum a Posteriori) estimation and the empirical Bayes method. We also propose a technique which speeds up learning the parameters using pseudo-scores. We applied our scheme to the two state-of-the-art schemes: the standard pivot-based scheme and the permutation-based scheme, and evaluated them using various kinds of datasets from the Metric Space Library. The results showed that our scheme outperformed the conventional schemes, with regard to both the number of distance computations and the CPU time, in all the datasets. 相似文献
60.