全文获取类型
收费全文 | 5733篇 |
免费 | 835篇 |
国内免费 | 213篇 |
专业分类
化学 | 1008篇 |
晶体学 | 7篇 |
力学 | 171篇 |
综合类 | 107篇 |
数学 | 571篇 |
物理学 | 1074篇 |
无线电 | 3843篇 |
出版年
2024年 | 33篇 |
2023年 | 195篇 |
2022年 | 231篇 |
2021年 | 449篇 |
2020年 | 352篇 |
2019年 | 263篇 |
2018年 | 194篇 |
2017年 | 273篇 |
2016年 | 344篇 |
2015年 | 302篇 |
2014年 | 467篇 |
2013年 | 336篇 |
2012年 | 387篇 |
2011年 | 411篇 |
2010年 | 295篇 |
2009年 | 273篇 |
2008年 | 337篇 |
2007年 | 295篇 |
2006年 | 274篇 |
2005年 | 222篇 |
2004年 | 162篇 |
2003年 | 141篇 |
2002年 | 75篇 |
2001年 | 79篇 |
2000年 | 71篇 |
1999年 | 54篇 |
1998年 | 47篇 |
1997年 | 39篇 |
1996年 | 44篇 |
1995年 | 32篇 |
1994年 | 12篇 |
1993年 | 24篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1967年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有6781条查询结果,搜索用时 703 毫秒
41.
文章讨论的基于“替换法”的汉字信息加、解密实现技术,改变了传统的汉字加密结果,使加密后的密文仍是可以识别和再利用的汉字,发送者可以在任何可编辑汉字的通讯设备上发送和接收密文,确保中文信息传输过程中的安全性。加、解密算法实现的代码语言为VFP6.0。 相似文献
42.
43.
随着社会的进步和科学技术的迅猛发展,对洗净技术的要求也越来越高。清洗方式多种多样,但最主要的是突出在喷射清洗和超声波清洗两大方面,应用于全国各行各业,并且也得到了明显进步。 相似文献
44.
In this paper we construct the linear support vector machine (SVM) based on the nonlinear rescaling (NR) methodology (see
[Polyak in Math Program 54:177–222, 1992; Polyak in Math Program Ser A 92:197–235, 2002; Polyak and Teboulle in Math Program
76:265–284, 1997] and references therein). The formulation of the linear SVM based on the NR method leads to an algorithm
which reduces the number of support vectors without compromising the classification performance compared to the linear soft-margin
SVM formulation. The NR algorithm computes both the primal and the dual approximation at each step. The dual variables associated
with the given data-set provide important information about each data point and play the key role in selecting the set of
support vectors. Experimental results on ten benchmark classification problems show that the NR formulation is feasible. The
quality of discrimination, in most instances, is comparable to the linear soft-margin SVM while the number of support vectors
in several instances were substantially reduced. 相似文献
45.
46.
介绍龙门铣床的直流调速控制系统的改造方案,根据龙门铣床工作台运动过程及原直流电机的容量来选择交流电机和变频器并对变频器的功能进行设定。 相似文献
47.
盘带机是纺织织带成品分卷设备,需要使用到收放卷控制。本文基于台达变频器在盘带机上的应用案例,论述盘带机自动化系统设计调试过程以及遇到的问题分析。 相似文献
48.
Evgenia Adamopoulou Konstantinos Demestichas Panagiotis Demestichas Michael Theologou 《International Journal of Communication Systems》2008,21(3):311-330
Cognitive radio systems dynamically reconfigure the algorithms and parameters they use, in order to adapt to the changing environment conditions. However, reaching proper reconfiguration decisions presupposes a way of knowing, with high enough assurance, the capabilities of the alternate configurations, especially in terms of achievable transmission capacity and coverage. The present paper addresses this problem, firstly, by specifying a complete process for extracting estimations of the capabilities of candidate configurations, in terms of transmission capacity and coverage, and, secondly, by enhancing these estimations with the employment of a machine learning technique. The technique is based on the use of Bayesian Networks, in conjunction with an effective learning and adaptation strategy, and aims at extracting and exploiting knowledge and experience, in order to reach robust (i.e. stable and reliable) estimations of the configurations' capabilities. Comprehensive results of the proposed method are presented, in order to validate its functionality. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
49.
50.
Support vector machine (SVM), developed by Vapnik et al., is a new and promising technique for classification and regression and has been proved to be competitive with the best available learning machines in many applications. However, the classification speed of SVM is substantially slower than that of other techniques with similar generalization ability. A new type SVM named projected SVM (PSVM), which is a combination of feature vector selection (FVS) method and linear SVM (LSVM), is proposed in present paper. In PSVM, the FVS method is first used to select a relevant subset (feature vectors, FVs) from the training data, and then both the training data and the test data are projected into the subspace constructed by FVs, and finally linear SVM(LSVM) is applied to classify the projected data. The time required by PSVM to calculate the class of new samples is proportional to the count of FVs. In most cases, the count of FVs is smaller than that of support vectors (SVs), and therefore PSVM is faster than SVM in running. Compared with other speeding-up techniques of SVM, PSVM is proved to possess not only speeding-up ability but also de-noising ability for high-noised data, and is found to be of potential use in mechanical fault pattern recognition. 相似文献