全文获取类型
收费全文 | 1709篇 |
免费 | 53篇 |
国内免费 | 79篇 |
专业分类
电工技术 | 21篇 |
综合类 | 70篇 |
化学工业 | 451篇 |
金属工艺 | 101篇 |
机械仪表 | 68篇 |
建筑科学 | 99篇 |
矿业工程 | 87篇 |
能源动力 | 132篇 |
轻工业 | 44篇 |
水利工程 | 10篇 |
石油天然气 | 37篇 |
无线电 | 64篇 |
一般工业技术 | 134篇 |
冶金工业 | 154篇 |
原子能技术 | 38篇 |
自动化技术 | 331篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 30篇 |
2021年 | 43篇 |
2020年 | 36篇 |
2019年 | 32篇 |
2018年 | 32篇 |
2017年 | 38篇 |
2016年 | 44篇 |
2015年 | 52篇 |
2014年 | 85篇 |
2013年 | 115篇 |
2012年 | 95篇 |
2011年 | 144篇 |
2010年 | 108篇 |
2009年 | 102篇 |
2008年 | 89篇 |
2007年 | 92篇 |
2006年 | 87篇 |
2005年 | 73篇 |
2004年 | 47篇 |
2003年 | 67篇 |
2002年 | 46篇 |
2001年 | 38篇 |
2000年 | 35篇 |
1999年 | 46篇 |
1998年 | 32篇 |
1997年 | 42篇 |
1996年 | 27篇 |
1995年 | 31篇 |
1994年 | 27篇 |
1993年 | 16篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有1841条查询结果,搜索用时 15 毫秒
31.
研究开发了冷固结含碳铁矿球团的还原工艺,它与环形转底炉相结合,形成快速直接还原新工艺,生产金属此球团,具有一系列优点,如:设备简单,生产效率高、能耗低等等。 相似文献
32.
33.
The Double‐Edged Sword: The Effects of Journalists' Social Media Activities on Audience Perceptions of Journalists and Their News Products 下载免费PDF全文
Jayeon Lee 《Journal of Computer-Mediated Communication》2015,20(3):312-329
As social media become popular news platforms, journalists and news organizations have been keen to capitalize on their potential to build and maintain audiences. However, little is known about the extent to which these efforts may have adverse implications. Based on normative theories, the present study investigates the influence of journalists' social media activities (specifically, self‐disclosure and interaction with other users) on audience perceptions of journalists. An experiment (N = 267) revealed that: Although both journalists' self‐disclosure and interaction positively influenced audience perceptions of the journalists in the personal dimension, interaction negatively influenced audience perceptions in the professional dimension; and the perceptions transferred to perceptions of news products, thereby mediating the relationship between journalists' social media activities and audience news perceptions. 相似文献
34.
众所周知,研究未知膜蛋白的类型可对基础研究和药物发现提供有用的线索。在后基因组时代,伴随着蛋白质序列数量的剧增,用实验方法确定膜蛋白类型太过昂贵和费时。因此,研究出一种能够自动发现可能的膜蛋白的计算方法变得很重要。鉴于这种情况,曾有人采用DC(Dipeptide Composition)方法表示蛋白质序列并取得了很好的预测结果。然而,采用这种表示方法得到的特征维数很高,冗余很大,使得预测系统十分复杂。为了解决这个问题,本文采用非线性降维算法KPCA(Kernel Principle component analysis),通过从高维的DC(Dipeptide Composition)特征空间中提取出低维的重要特征来简化该系统,采用K-NN(K-nearest neighbor)分类器从约简后的低维特征中预测膜蛋白类型。实验结果表明,使用KPCA方法预测膜蛋白类型非常有效。 相似文献
35.
We propose and study the Maximum Constrained Agreement Subtree (MCAST) problem, which is a variant of the classical Maximum
Agreement Subtree (MAST) problem. Our problem allows users to apply their domain knowledge to control the construction of
the agreement subtrees in order to get better results. We show that the MCAST problem can be reduced to the MAST problem in
linear time and thus we have algorithms for MCAST with running times matching the fastest known algorithms for MAST.
A preliminary version of this paper appears in the Proceedings of the Fifth Workshop on Algorithms in Bioinformatics (WABI 2005).
Research of H.F. Ting is supported in part by Hong Kong RGC Grant HKU-7172/06E. 相似文献
36.
传统的Isomap算法仅侧重于当前数据的分析,不能提供由高维空间到低维空间的快速直接映射,因此无法用于特征提取和高维数据检索.针对这一问题,文中提出一种基于Isornap的快速数据检索算法.该算法能够快速得到新样本的低维嵌入坐标,并基于此坐标检索与输入样本最相似的参考样本.在典型测试集上的实验结果表明,该算法在实现新样本到低维流形快速映射的同时,能较好保留样本的近邻关系. 相似文献
37.
Debra L. Cook Moti Yung Angelos D. Keromytis 《International Journal of Information Security》2009,8(3):211-231
We introduce the concept of an elastic block cipher which refers to stretching the supported block size of a block cipher to any length up to twice the original block size while
incurring a computational workload that is proportional to the block size. Our method uses the round function of an existing
block cipher as a black box and inserts it into a substitution- permutation network. Our method is designed to enable us to
form a reduction between the elastic and the original versions of the cipher. Using this reduction, we prove that the elastic
version of a cipher is secure against key-recovery attacks if the original cipher is secure against such attacks. We note
that while reduction-based proofs of security are a cornerstone of cryptographic analysis, they are typical when complete
components are used as sub-components in a larger design. We are not aware of the use of such techniques in the case of concrete
block cipher designs. We demonstrate the general applicability of the elastic block cipher method by constructing examples
from existing block ciphers: AES, Camellia, MISTY1, and RC6. We compare the performance of the elastic versions to that of
the original versions and evaluate the elastic versions using statistical tests measuring the randomness of the ciphertext.
We also use our examples to demonstrate the concept of a generic key schedule for block ciphers.
相似文献
Angelos D. KeromytisEmail: |
38.
Ivan Lanese 《Theoretical computer science》2010,411(19):1928-6611
In wireless systems, the communication mechanism combines features of broadcast, synchrony, and asynchrony. We develop an operational semantics for a calculus of wireless systems. We present different Reduction Semantics and a Labelled Transition Semantics and prove correspondence results between them. Finally, we apply CWS to the modelling of the Alternating Bit Protocol, and prove a simple correctness result as an example of the kind of properties that can be formalized in this framework.A major goal of the semantics is to describe the forms of interference among the activities of processes that are peculiar of wireless systems. Such interference occurs when a location is simultaneously reached by two transmissions. The Reduction Semantics differ on how information about the active transmissions is managed.We use the calculus to describe and analyse a few properties of a version of the Alternating Bit Protocol. 相似文献
39.
In order to conveniently analyze stability of uncertain multiple input-delayed closed-loop systems and successfully synthesize passive controllers for a general class of uncertain multiple input-delayed systems with disturbance, the so-called reduction method is applied to the multiple input-delayed systems with parametric uncertainties. A feedback controller associated with the system state and the past control action is designed to guarantee the passivity of the closed-loop systems for all admissible uncertainties. The theoretical findings are illustrated and verified with one numerical example. 相似文献
40.