全文获取类型
收费全文 | 15747篇 |
免费 | 1099篇 |
国内免费 | 721篇 |
专业分类
电工技术 | 451篇 |
综合类 | 681篇 |
化学工业 | 1968篇 |
金属工艺 | 1472篇 |
机械仪表 | 896篇 |
建筑科学 | 1803篇 |
矿业工程 | 442篇 |
能源动力 | 402篇 |
轻工业 | 351篇 |
水利工程 | 171篇 |
石油天然气 | 303篇 |
武器工业 | 104篇 |
无线电 | 1736篇 |
一般工业技术 | 1697篇 |
冶金工业 | 415篇 |
原子能技术 | 146篇 |
自动化技术 | 4529篇 |
出版年
2024年 | 28篇 |
2023年 | 178篇 |
2022年 | 302篇 |
2021年 | 378篇 |
2020年 | 354篇 |
2019年 | 362篇 |
2018年 | 336篇 |
2017年 | 454篇 |
2016年 | 546篇 |
2015年 | 523篇 |
2014年 | 916篇 |
2013年 | 1030篇 |
2012年 | 947篇 |
2011年 | 1220篇 |
2010年 | 842篇 |
2009年 | 970篇 |
2008年 | 864篇 |
2007年 | 1041篇 |
2006年 | 1040篇 |
2005年 | 801篇 |
2004年 | 712篇 |
2003年 | 620篇 |
2002年 | 514篇 |
2001年 | 372篇 |
2000年 | 348篇 |
1999年 | 319篇 |
1998年 | 241篇 |
1997年 | 205篇 |
1996年 | 189篇 |
1995年 | 169篇 |
1994年 | 121篇 |
1993年 | 100篇 |
1992年 | 81篇 |
1991年 | 72篇 |
1990年 | 48篇 |
1989年 | 47篇 |
1988年 | 42篇 |
1987年 | 25篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 21篇 |
1983年 | 25篇 |
1982年 | 15篇 |
1981年 | 24篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 19篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
通过正交试验研究了各工艺量数以钢/铝合金液固相复合性能的影响,最佳工艺条件为铝合金液体温度790℃,钢板表面处理为酸洗+钢刷+5%的氟钛酸钾助焊剂,复合压力为39.2MPa,组织观察表面界面脆性化合物的形成是导致结合强度降低的一个重要因素。 相似文献
52.
Howard S. Manwaring 《Neural computing & applications》1994,2(3):168-178
A comparison is made between backpropagation and general regression neural networks for the prediction of parts per billion lead concentration when used to process data obtained from digested curry powder by the electrochemical analysis method of differential pulse, anodic stripping at a thin film mercury electrode (TFME). Two data sets are used, one requiring the net to classify an unknown analytical data vector into one of a number of previously learnt concentrations, and one requiring the net to predict the probable concentration of an unknown sample by interpolation of the already learnt concentrations. For both of these data sets the general regression neural network is shown to train faster and to provide results superior to those obtained by backpropagation. 相似文献
53.
分片汇接的网状网结构是江苏省本地电话网的基本框架,而汇接局和连接汇接局的传输系统则是网路规划与通信建设的重点。 相似文献
54.
A novel successive learning algorithm based on a Test Feature Classifier is proposed for efficient handling of sequentially provided training data. The fundamental characteristics of the successive learning are considered. In the learning, after recognition of a set of unknown data by a classifier, they are fed into the classifier in order to obtain a modified performance. An efficient algorithm is proposed for the incremental definition of prime tests which are irreducible combinations of features and capable of classifying training patterns into correct classes. Four strategies for addition of training patterns are investigated with respect to their precision and performance using real pattern data. A real-world problem of classification of defects on wafer images has been dealt with by the proposed classifier, obtaining excellent performance even through efficient addition strategies. 相似文献
55.
Mohammad Ziabari Vahid Mottaghitalab Scott T. McGovern A. K. Haghi 《Nanoscale research letters》2007,2(12):597-600
In this paper, a new image analysis based method for electrospun nanofiber diameter measurement has been presented. The method
was tested by a simulated image with known characteristics and a real web. Mean (M) and standard deviation (STD) of fiber
diameter obtained using this method for the simulated image were 15.02 and 4.80 pixels respectively, compared to the true
values of 15.35 and 4.47 pixels. For the real web, applying the method resulted in M and STD of 324 and 50.4 nm which are
extremely close to the values of 319 and 42 nm obtained using manual method. The results show that this approach is successful
in making fast, accurate automated measurements of electrospun fiber diameters. 相似文献
56.
Yong-Jik KimJames H. Anderson 《Information Processing Letters》2002,84(1):47-55
A simple code transformation is presented that reduces the space complexity of Yang and Anderson's local-spin mutual exclusion algorithm. In both the original and the transformed algorithm, only atomic read and write instructions are used; each process generates Θ(logN) remote memory references per lock request, where N is the number of processes. The transformed algorithm uses Θ(N) distinct variables, which is clearly optimal. 相似文献
57.
Colin Hines 《Energy Policy》1985,13(2):188-189
This communication illustrates the work of the London Energy and Employment Network. LEEN has the twin aims of promoting a rational energy policy for London and, in the process, generating much needed employment. In cooperation with Hackney, one of Britain's poorest boroughs, LEEN organized Hackney's Cold War — a series of initiatives showing the practical measures, informational back-up and funding sources necessary for a local energy policy. LEEN intends to repeat this project in other London Boroughs, with the eventual aim of helping to persuade central government to adopt a more comprehensive approach to energy conservation nationally. 相似文献
58.
Gregory S. Ho Chen Huang Emily A. Carter 《Current Opinion in Solid State & Materials Science》2007,11(5-6):57-61
Orbital-free density functional theory (OF-DFT) can be made to scale linearly with sample size, allowing thousands of atoms to be treated explicitly with quantum mechanics. State-of-the-art kinetic energy density functionals and ion–electron pseudopotentials are used to obtain accurate structural property predictions for nanoparticles, nanowires, extended surfaces, and nanoindentation of simple metals. 相似文献
59.
In recent years, the Asia-Pacific region has experienced several financial setbacks, including speculative attacks in 1998 and the SARS outbreak in 2003. Financial stresses of this nature are unanticipated, and not all of the dangers can be predicted by the examination of market information and macroeconomic indicators. The Early Warning System (EWS) that has been adopted by the International Monetary Fund may not be able to predict future financial crises for all possible scenarios, because shocks come in many different forms. To supplement the EWS, this paper proposes a data mining framework to measure the resilience of an economy. The resilience framework does not predict a crisis, but rather assesses the current state of health of an economy and its ability to withstand a financial shock should one occur. The framework is based on a feedback system consisting of two stages. The first stage assigns a resilience score to each economy based on a fuzzy logic scoring scheme that is built on the ambiguous reasoning of experts. The second stage uses the classification tree approach to estimate thresholds for each economic indicator, and examines the quality of the fuzzy score. The result from the second stage is then passed back to the first stage as feedback. The final result is obtained when the feedback system reaches its equilibrium state. The proposed resilience framework is applied to the external-sector and the public-sector economies of several countries to illustrate its applicability. 相似文献
60.
一种协调的科技文献分类方法 总被引:1,自引:0,他引:1
科技文献之间的相互引证关系反映了一种科学交流活动,显示了科学文献之间(甚至是学科之间)的内在联系,而通过追溯文献之间的这种关系,可以改善和提高传统的基于内容的科技文献的分类的方法。论文利用有相互引证关系,有同引关系,以及有耦合关系的两篇文献一般是属于同一类的这一特点,提出了文献之间的引用相似度,同引相似度,耦合相似度这三个概念,再利用这三个概念生成了文献之间的“结构相似度”,并将它用于K-NN分类法中得出一种基于结构的分类法。最后,论文将这种基于结构的分类法和基于内容的NaveBayes分类法结合起来提出了一种新的协调分类法。 相似文献