全文获取类型
收费全文 | 36379篇 |
免费 | 4297篇 |
国内免费 | 2725篇 |
专业分类
电工技术 | 2722篇 |
综合类 | 3018篇 |
化学工业 | 1750篇 |
金属工艺 | 784篇 |
机械仪表 | 4155篇 |
建筑科学 | 699篇 |
矿业工程 | 1011篇 |
能源动力 | 585篇 |
轻工业 | 825篇 |
水利工程 | 290篇 |
石油天然气 | 393篇 |
武器工业 | 440篇 |
无线电 | 8225篇 |
一般工业技术 | 2760篇 |
冶金工业 | 356篇 |
原子能技术 | 110篇 |
自动化技术 | 15278篇 |
出版年
2024年 | 161篇 |
2023年 | 496篇 |
2022年 | 802篇 |
2021年 | 975篇 |
2020年 | 1018篇 |
2019年 | 962篇 |
2018年 | 902篇 |
2017年 | 1630篇 |
2016年 | 1747篇 |
2015年 | 2108篇 |
2014年 | 2855篇 |
2013年 | 2454篇 |
2012年 | 3136篇 |
2011年 | 3343篇 |
2010年 | 2277篇 |
2009年 | 2482篇 |
2008年 | 2393篇 |
2007年 | 2545篇 |
2006年 | 2046篇 |
2005年 | 1450篇 |
2004年 | 1170篇 |
2003年 | 1214篇 |
2002年 | 1052篇 |
2001年 | 972篇 |
2000年 | 746篇 |
1999年 | 567篇 |
1998年 | 393篇 |
1997年 | 505篇 |
1996年 | 262篇 |
1995年 | 197篇 |
1994年 | 157篇 |
1993年 | 105篇 |
1992年 | 84篇 |
1991年 | 75篇 |
1990年 | 48篇 |
1989年 | 24篇 |
1988年 | 20篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
传感器采用的28 μm厚的4层结构PVDF压电薄膜制成,传感器表面电极形状的制作采用剪切加丙酮腐蚀的方法,保证了传感器有一定的非金属化的边缘。对于电极的引出是将传感器上、下电极面引脚错开,引出电极比较容易做到穿透式,采用压接端子压接和空心小铆钉铆接两种方法。 相似文献
132.
133.
根据已知镍基合金成分和γ′相成分,运用分层宽容多目标优化法,分别计算了γ相成分及γ′相含量.优化测算过程的实现是通过建立使杠杆定律等式两端数值差最小和两相共格错配度最小的目标函数,并通过设置γ′相含量和基体相成分取值范围的约束条件而实现的.验证了该方法的可行性和准确性. 相似文献
134.
Humidity Sensor Characteristics of Woodceramics 总被引:9,自引:0,他引:9
Kiyokazu Kasai Kiyotaka Shibata Koji Saito Toshihiro Okabe 《Journal of Porous Materials》1997,4(4):277-280
The humidity sensor characteristics of Woodceramics were investigated. The Woodceramics used in this experiment were prepared at 650–900°C. The size of specimens selected was 1 × 1 × 10 mm . One was used as-cut and the other was polished. Above 700°C, the resistance of the specimen was below 50 and the decrease of resistance with increasing relative humidity was small. The specimen prepared at 650°C had a resistance of about 1 k. The resistance of as-cut specimens decreased with increase in relative humidity, but that of the polished specimen did not change significantly. The difference between as-cut and polished samples was explained by the differences in surface micro-structure. 相似文献
135.
Upon the application of amperometric biosensor to the biological fluid, ascorbic acid interferes the amperometric determination of analytes, because the oxidative potential of ascorbic acid is lower than that of electro active substances such as H2O2 produced by the enzymatic reaction. In this study we propose a method to block ascorbic acid based on the electrostatic interaction with self-assembled monolayer (SAM) and its application of the surface modified electrode to biosensor. In order to form SAM on the gold electrode with carboxyl group, 7-carboxy-heptanethiol (7-CHT) was used. The 7-CHT modified electrode did not show anodic response to ascorbic acid, but oxidized phenanthroline cobalt complex [Co(phen)32+], which can be used as a mediator of biosensor. Thus, the 7CHT-modified electrode was applied to biosensor mediated with Co(phen)32+. Fructose dehydrogenase (FDH) was immobilized to the 7-CHT modified electrode. Fructose was determined selectively with the FDH/7-CHT modified electrode at the range of 0.2-2 mM. 相似文献
136.
极限电流型氧传感器的实验研究 总被引:3,自引:0,他引:3
本实验用8mol%Y_2O_3-ZrO_2固体电解质制成了极限电流型氧传感器,并测定了氧在0.23~28.70mol%,温度在550~800℃范围时,传感器的输出特性,观察到该传感器有较好的稳定性和电压电流特性曲线。实验验证了极限电流值与氧摩尔分数和温度的关系。 相似文献
137.
提出一种从RBF神经网络隐含层的输出信息出发,通过PLS快速剪枝法,一次性剪去多余节点,生成最优规模的数学解析模型的方法。并用该方法建立了某化工企业精对苯二甲酸(PTA)晶体平均粒径的软测量模型,针对实际对象进行仿真研究,结果表明,该方法计算速度快,建立的模型精度高,适合实际工程应用的需求。 相似文献
138.
Rakesh?Kumar?MahajanEmail author Inderpreet?Kaur Mandeep?Singh?Bakshi 《Journal of surfactants and detergents》2004,7(2):131-134
Poly(vinyl chloride) (PVC) membrane electrodes to determine monomer concentrations of tetradecyltrimethylammonium ion (TTA+) and hexadecylpyridinium ion (HPy+) based on neutral ion-pair carrier complexes of tetradecyltrimethylammonium dodecyl sulfate (TTA+-DS−) and hexadecylpyridinium dodecyl sulfate (HPy+-DS−), respectively, are reported here. The electrodes exhibit a Nernstian slope of 59 mV per decade for TTA+ and a sub-Nernstian slope of 34.5 mV per decade for HPy+ ions. The TTA+ ion-selective electrode (ISE) and the HPy+-ISE can determine the monomer units down to concentrations as low as 4.0×10−4M and 1.66×10−5 M, respectively. The effect of various additives, such as the anionic polyelectrolyte sodium dextran sulfate and macrocyclic
β-cyclodextrin, on the surface activity exhibited by the cationic surfactants TTA+-DS− and HPy+-DS−, in the presence of background concentrations of NaCl was also examined with surfactant-selective sensors. The Gibbs free
energy of micelle formation (ΔG
m
) of both surfactants in the presence of various additives was calculated and found to be less favorable with respect to an
increase in the amount of additives due to less availability of cationic surfactant monomer units. The ion-pair complexes
TTA+-DS− and HPy+-DS− were found to behave as selective carrier compounds in PVC membranes in determining the concentration of monomer units of
both TTA+ and HPy+, respectively. The proposed sensors worked well at a fairly acidic pH of 1–6.5 with response time of 60 s. The sensors responded
well to the surfactant ions even in the presence of additives at lower concentration. The lifetime of the sensors is 3 mon. 相似文献
139.
140.
Wiener模型结构能有效地表征系统的动态和静态特性, 因此这里首先基于这一结构建立软测量模型, 利用动态与静态子模型分别建立辅助变量与主导变量间的动态与静态关系, 并说明该软测量模型的可行性, 给出模型具体表达式. 其次, 针对所提模型, 提出分步辨识方式获得最优模型参数, 说明其可行性. 再次, 为了减少计算和实现模型在线更新, 这里提出参数辨识递推算法, 并给出软测量模型参数的收敛性结论. 通过实例仿真, 可以看出本文提出模型的可行性, 以及分步辨识方式与递推算法的有效性. 相似文献