全文获取类型
收费全文 | 9665篇 |
免费 | 790篇 |
国内免费 | 501篇 |
专业分类
电工技术 | 1187篇 |
综合类 | 581篇 |
化学工业 | 2832篇 |
金属工艺 | 1370篇 |
机械仪表 | 362篇 |
建筑科学 | 102篇 |
矿业工程 | 145篇 |
能源动力 | 1064篇 |
轻工业 | 315篇 |
水利工程 | 29篇 |
石油天然气 | 108篇 |
武器工业 | 45篇 |
无线电 | 690篇 |
一般工业技术 | 1083篇 |
冶金工业 | 501篇 |
原子能技术 | 97篇 |
自动化技术 | 445篇 |
出版年
2024年 | 32篇 |
2023年 | 139篇 |
2022年 | 192篇 |
2021年 | 253篇 |
2020年 | 288篇 |
2019年 | 280篇 |
2018年 | 208篇 |
2017年 | 324篇 |
2016年 | 280篇 |
2015年 | 284篇 |
2014年 | 471篇 |
2013年 | 501篇 |
2012年 | 521篇 |
2011年 | 833篇 |
2010年 | 603篇 |
2009年 | 648篇 |
2008年 | 586篇 |
2007年 | 712篇 |
2006年 | 614篇 |
2005年 | 463篇 |
2004年 | 430篇 |
2003年 | 354篇 |
2002年 | 331篇 |
2001年 | 285篇 |
2000年 | 239篇 |
1999年 | 187篇 |
1998年 | 189篇 |
1997年 | 133篇 |
1996年 | 102篇 |
1995年 | 97篇 |
1994年 | 105篇 |
1993年 | 63篇 |
1992年 | 47篇 |
1991年 | 36篇 |
1990年 | 31篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1964年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
P Sarkar D Ghosh D Bhattacharya R Kataky SJ Setford SF White APF Turner 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(12):1389-1394
Allergen levels in indoor environments, leading to many diseases, eg asthma, rhinitis and conjunctivitis, affect a large and increasing fraction of the population. A quite effective and inexpensive method of a rough but very rapid overall assessment of total allergen level in the environment has been developed. The method involved estimation of protein in allergen extracts by screen‐printed electrodes using two different techniques. The biosensor comprised a rhodinised carbon working electrode, a silver/silver chloride reference electrode and a carbon counter electrode. In the first method the enzyme protease reacted with allergen protein to release amino acid, which produced hydrogen peroxide in the presence of amino acid oxidase. This was detected amperometrically. The second method used potassium bromide as electrolyte and the electrode was subjected to dual potential. Bromine, released due to electrolysis at higher potential, was consumed by the allergen protein at lower potential. In the first method, a unique technique was used to microencapsulate the enzyme protease and immobilise it on the surface of the electrode by in‐situ polymerisation to avoid contact with the amino acid oxidase. A total of seven allergens were tested and the results gave a good correlation with the standard protein measurement method. Environmental specimens from indoors, schools and workplaces can be evaluated for the aeroallergens produced by dust mites, animal hairs, cockroach debris, pollens, etc as a means of determining the exposure risk. Copyright © 2005 Society of Chemical Industry 相似文献
23.
在氯化铵-氨水(pH=11)支持电解质中用微银汞膜电极进行试验,锰、铁不干扰测定,用EDTA滴定氯化钙获得令人满意的结果。对三种样品进行分析,变异系数为0.08%—0.11%。该法快速准确,适用于氯化钙主要成份的测定。 相似文献
24.
In order to develop a basic electrode with low fume and good usability, a uew slag system has been designed after analyzing several basic electrode slag systems. Then in view of uniform design method, arranging the experiment points by it, the influenced laws of the uew system coating compouents on the arc stability had been searched. In the formula, niue coating compouents were taken as independent variables and they were divided into six levels in all twenty-four experiments. The arc stability was taken as function and taken down the data when welding and then put them into the computer to be processed statistically. The analysis results give the mathematical model and trend diagrams between independent variables and the function. They indicate that the effects of many coating compouents on the arc stability are in the mutual form. The mutual effects between CaCO3 and BaF2, BaF2 and BaCO3 , increases the arc stability separately. While the mutual effects between CaF2 and iron powder, the square item of iron powder itself decreases the arc stability separately. 相似文献
25.
Piyasak Chaumpluk Kagan Kerman Eiichi Tamiya 《Science and Technology of Advanced Materials》2007,8(4):323-330
Combinations of PCR-based amplification platform using 5′ thiolated and biotinylated specific primers, S1 nuclease-PCR products treatment, ferrocene-streptavidin (Fc-Stv)-magnetic binding for DNA accumulation, and screen printed gold electrode for the DNA allocation, were applied to Hoechst 33258-induced DNA aggregation and signals induction system for direct signals detection and DNA quantification in food samples. Thiolated and biotinylated at each 5′ terminus enabled DNA purification through S1 nuclease treatment for primers and non-specific DNA elimination and enabled DNA trapping with a ferrocene-streptavidin-magnetic system. This facilitated the accumulation of target DNAs at higher concentration, resulting in enhanced signals. After allocation of DNA on the surface of gold electrode via thiol binding, intensity of DNA signals through these treatments could be measured directly after being induced by Hoechst 33258. Wider amplitude changes in anodic current peaks between negative and positive samples (increasing from 3.70 to 10.10 μA) compared with those applied with no treatment combinations (decreasing from 3.92 to 1.23 μA) were observed. This enhancement of the signals allowed a greater efficiency of DNA quantification. When this combination was used for GMOs content estimation in reference samples, results revealed an improved accuracy from 66% to 96%. The combined biosensor system, although more costly than the standard Hoechst 33258/carbon electrode system, provided an alternative choice for DNA quantification, offering labor-free immobilization of probe onto electrode surface, easy test administration, and efficient semi-quantitative test without expensive instruments. 相似文献
26.
We have developed a diffusion-controlled size-selective method for sensing chloride ion in the presence of bromide ion, based on a thin, nanoporous, plasma-polymerized coating of hexamethyldisiloxane on an Ag/AgCl electrode. Sub-nanometer-sized pores responsible for a highly cross-linked polymer network in the plasma-polymerized coating allowed diffusion-controlled permeation of chloride ion while blocking the larger bromide ion. An electrode coating of thickness greater than 70 nm enabled chloride detection in the concentration range 1-10 mM in the presence of 0.63 mM bromide ion. Advantages of this approach are: (1) simple design compared with ionophore-based strategies and (2) compatibility with microfabrication and mass production processes. 相似文献
27.
28.
29.
人工接地装置设计方法分析 总被引:1,自引:0,他引:1
本文系统地论述了人工接地装置的设计方法,修正了现有文献中有关论述的缺点和错误,提出了通过迭代求解方程组来设计人工接地装置的新方法。 相似文献
30.
In the absence of a bulk diffusion effect, it is shown for the first time that the impedance spectra for the chlorine evolution reaction on a rotating thin ring electrode comprise three consecutive semicircles in the capacitive half of the complex plane. The first (highest frequency) semicircle is due to the charge-transfer resistance for chloride discharge and the simultaneous chlorine adsorption coupled to the double-layer capacitance. The second semicircle (around 5 Hz) is due to the adsorption and desorption of a chlorine intermediate. The third (lowest frequency, around 0.5 Hz) semicircle is due to the relaxation of surface oxygen species. The impedance data allow the steps of the overall reaction to be examined individually. On a Pt surface the rate of chloride discharge and simultaneous chlorine adsorption (the admittance of the first semicircle) is first order with respect to chloride concentration and has a potential-dependence close to 58 mV/decade. The rate of the adsorption and desorption process (the admittance of the second semicircle) is second order with respect to chloride concentration, and has a potential dependence close to 30 mV/decade. The time constant for the adsorption/desorption processes is ca 20 ms, independent of electrode potential in the range studied. These features are consistent with a mechanism in which a faster discharge reaction (Cl− Clad + e) is followed by a slower surface combination reaction (2Clad → Cl2), but inconsistent with mechanisms in which ion + atom desorption is predominant, the initial chloride discharge is slow, or a unipositively charged chlorine species is involved. 相似文献