全文获取类型
收费全文 | 32106篇 |
免费 | 3085篇 |
国内免费 | 1486篇 |
专业分类
电工技术 | 2275篇 |
技术理论 | 1篇 |
综合类 | 2005篇 |
化学工业 | 5451篇 |
金属工艺 | 1792篇 |
机械仪表 | 2020篇 |
建筑科学 | 2539篇 |
矿业工程 | 987篇 |
能源动力 | 876篇 |
轻工业 | 2408篇 |
水利工程 | 584篇 |
石油天然气 | 1666篇 |
武器工业 | 271篇 |
无线电 | 3947篇 |
一般工业技术 | 4092篇 |
冶金工业 | 1354篇 |
原子能技术 | 413篇 |
自动化技术 | 3996篇 |
出版年
2024年 | 179篇 |
2023年 | 649篇 |
2022年 | 1281篇 |
2021年 | 1530篇 |
2020年 | 1193篇 |
2019年 | 974篇 |
2018年 | 1080篇 |
2017年 | 1209篇 |
2016年 | 988篇 |
2015年 | 1373篇 |
2014年 | 1730篇 |
2013年 | 1897篇 |
2012年 | 2061篇 |
2011年 | 2133篇 |
2010年 | 1815篇 |
2009年 | 1820篇 |
2008年 | 1782篇 |
2007年 | 1566篇 |
2006年 | 1637篇 |
2005年 | 1332篇 |
2004年 | 873篇 |
2003年 | 885篇 |
2002年 | 829篇 |
2001年 | 732篇 |
2000年 | 742篇 |
1999年 | 790篇 |
1998年 | 639篇 |
1997年 | 551篇 |
1996年 | 476篇 |
1995年 | 432篇 |
1994年 | 322篇 |
1993年 | 247篇 |
1992年 | 227篇 |
1991年 | 145篇 |
1990年 | 126篇 |
1989年 | 115篇 |
1988年 | 83篇 |
1987年 | 52篇 |
1986年 | 30篇 |
1985年 | 35篇 |
1984年 | 18篇 |
1983年 | 21篇 |
1982年 | 23篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1975年 | 3篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
在含有0.3mol.L~(-1)HAC-NH_4AC(pH=5.8)和2.0×10~5mol.L~(-1)PV 溶液中,可得到铟(Ⅱ)-PV 配合物极谱波。峰电位在-0.69V(VS.SCE)处,其导数峰高与铟(Ⅲ)在0.020~0.400mg.L~(-1)范围内的浓度有良好的线性关系,最低检出限为0.005mg.L~(-1)。研究了该波的机理,证明是一种配合吸附波,并应用于轴承镀层中铟含量的测定。 相似文献
72.
为了明确鄂尔多斯盆地东南部长7油层组沉积体系类型和沉积相展布特征,总结其沉积演化规律,以沉积学的基本原理和方法为指导,综合运用地球化学、盆地分析等理论和方法,通过野外露头、钻井、测井等资料的综合分析,认为鄂尔多斯盆地东南部长7油层组主要发育三角洲和湖泊沉积体系,可进一步划分为3类亚相,其中以三角洲前缘和深湖2种亚相为主. 相似文献
73.
In this article, we solve the problem of global stabilization for a chain of integrators in the presence of input saturation and disturbances. A novel and elegant approach to solve this problem, in the absence of disturbances, was proposed by Teel (1992) using saturation functions and coordinate transformation. With Teel’s work as a foundation, many results have been proposed to improve the performance of controllers for a chain of integrators. Naturally, all such approaches also inherited the limitations of Teel’s approach. Most importantly, in the presence of uncertainties and disturbances, the transformation introduced in Teel (1992) would considerably shrink the region where the controller is unsaturated and, severely limit the level of uncertainties and disturbances which can be tolerated. In order to overcome these difficulties, a conceptually different approach which does not rely on the coordinate transformation is presented in this work. Specifically, modified saturation functions are directly applied to the tracking error of actual states as opposed to transformed fictitious states to develop a globally stable controller. The proposed controller is less conservative in terms of the level of uncertainties and disturbances which can be handled. In addition, arbitrarily good disturbance rejection in the unsaturated region can be achieved theoretically. Comparative simulation studies performed on a third order integrator chain verified the effectiveness of the proposed scheme. 相似文献
74.
基于遗传算法的并发谈判在电子商务应用中具有独特的优势,但已有的研究尚未考虑议题之间的相关性、动态权重的变化规则依赖于对手信息的获取,极大地限制了其使用价值.对此,提出议题分组的方法以解决议题的相关性问题,而议题权重的变化则采取从历史资源中发掘知识的方法进行动态调整.构建了基于遗传算法的关联性议题并发谈判模型,给出了模型的形式化描述、谈判算法设计和动态权重更新方案.通过对模型的实验和比较分析,证实了该方案能够更方便地满足用户谈判的多样性需求,解决谈判中议题关联性的问题,而且能够快速、有效地得出最优谈判结果. 相似文献
75.
A novel approach to characterise the model prediction errors using a Gaussian mixture model is proposed. The motivation for this work lies behind many data models that are developed through prediction error minimisation with the assumption of a normal noise distribution. When the noise is non-normal, which may often be the case in complicated data modelling scenarios, the model prediction errors may contain rich information, which can be further exploited for model refinement and improvement. The key contents presented in this paper include: choosing the relevant variables to form the error data, optimising the number of Gaussian components required for the error data modelling, and fitting the Gaussian mixture parameters using an expectation-maximisation algorithm. Application of the proposed method for further model improvement, within the framework of hybrid deterministic/stochastic modelling, is also discussed. Preliminary results on the real industrial Charpy impact energy data for heat-treated steels show its effectiveness for model error characterisation, and the potential for model performance improvement in terms of prediction accuracy as well as providing accurate prediction confidence intervals. 相似文献
76.
Electrical resistivity of Ni–Cr alloys containing 5.5, 11.3, 15.7, 16.8, 19.4, 22.0, 24.6, and 27.0 at % Cr has been measured as a function of the absolute temperatureT between 4 and 300 K. The sample with the Cr content of 22.0 at % exhibits a small minimum at about 10 K. No minimum has been observed in any other of the above samples, although an anomalousT dependence has been found in alloys containing 15.7, 16.8, and 19.4 at % Cr. The minimum has been discussed from the viewpoint of the Béal-Monod theory for the Kondo effect in concentrated systems and the mechanism by Greig and Rowlands based on aT-dependent decrease of the impurity electrical resistivity. It is concluded that the minimum in the Ni–Cr system is still a phenomenon which is not well understood at the present time. 相似文献
77.
78.
GuoliangChen XidongHui KefuYao HuaiyuHou XiongjunLiu MeilingWang GuangChen 《北京科技大学学报(英文版)》2005,12(2):143-150
The atomic configuration of chemical short-range order (CSRO) for the Zr-base metallic glasses was investigated by using nano-diffraction and high resolution transmission electronic microscopy (HRTEM) technology with a beam size of 0.5 rim. It is illustrated that the pattern of atomic configuration of CSRO might have various compound counterparts because of the chemical interaction of bonding atoms. Some atomic configuration of MCSRO is similar to the icosahedral structure with 10-fold symmetry of very weak spots. In deed, the nano-beam technology could clearly detect the evolution of atomic configuration in nanometer scale during the transformation from the metallic melt to the primary crystallization. The local atomic configuration of CSRO is also investigated by molecular dynamics simulation (MD) for the Zr2Ni compound in a wider temperature range. The CSRO in the melt could be pictorially demonstrated as distorted coordination polyhedron of the compound structure and/or the structure similar to cubo-octahedron analogs. The MD simulation illustrates that the atomic packing of long-range order disappears just above the melting point, but the chemical interaction of bonding atoms still exists that leads to form the various CSRO with the atomic configuration similar to stable or metastable unit cell of Zr2Ni compound. The icosahedral polyhedron became more abundance as the overheating temperature was raised. 相似文献
79.
一种高效的视图维护算法 总被引:7,自引:0,他引:7
通过选择性算法将增量式视图维护和视图自维护有效地融合在一起.同时它还利用相关性算法对不相关更新进行过滤,可以有效地降低消息总数和数据的通信量,从而大大提高视图维护的效率,具有现实的应用意义. 相似文献
80.
本文介绍室内平面绕流磨损试验结果和应用于真机的磨损预估,与刘家峡、葛洲坝机组实测磨损量核算结果差别不大。在此基础上对在建的小浪底机组做了估算,并提出了一些看法。 相似文献