首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7515篇
  免费   570篇
  国内免费   214篇
电工技术   417篇
技术理论   1篇
综合类   492篇
化学工业   1277篇
金属工艺   292篇
机械仪表   386篇
建筑科学   485篇
矿业工程   209篇
能源动力   205篇
轻工业   722篇
水利工程   127篇
石油天然气   450篇
武器工业   52篇
无线电   670篇
一般工业技术   902篇
冶金工业   631篇
原子能技术   49篇
自动化技术   932篇
  2024年   28篇
  2023年   115篇
  2022年   188篇
  2021年   280篇
  2020年   199篇
  2019年   183篇
  2018年   234篇
  2017年   250篇
  2016年   226篇
  2015年   270篇
  2014年   374篇
  2013年   476篇
  2012年   477篇
  2011年   518篇
  2010年   426篇
  2009年   395篇
  2008年   408篇
  2007年   386篇
  2006年   401篇
  2005年   299篇
  2004年   225篇
  2003年   204篇
  2002年   181篇
  2001年   199篇
  2000年   164篇
  1999年   177篇
  1998年   252篇
  1997年   178篇
  1996年   125篇
  1995年   102篇
  1994年   86篇
  1993年   61篇
  1992年   34篇
  1991年   26篇
  1990年   19篇
  1989年   19篇
  1988年   21篇
  1987年   12篇
  1986年   10篇
  1985年   7篇
  1984年   3篇
  1983年   10篇
  1982年   9篇
  1980年   3篇
  1979年   5篇
  1978年   3篇
  1977年   10篇
  1976年   11篇
  1975年   2篇
  1974年   3篇
排序方式: 共有8299条查询结果,搜索用时 0 毫秒
21.
22.
本文研究了TiO2掺入对CaO稳定ZrO2(简称CaSZ-NiCr)金属陶瓷烧结特性的影响,测定了CaSZ-NiCr-TiO2金属陶瓷烧结样品的密度和显微硬度,结果表明,TiO2的掺入能提高CaSZ-NICr金属陶瓷的烧结密度和显微硬度,对CaSZ-NiCr金属陶瓷有助烧结作用.金相观察表明,TiO3的掺入改变了NiCr相在金属陶瓷中的形貌,说明了NiCr与CaSZ的浸润性有一定的改善.XRD和EPMA分析结果显示,TiO2偏聚在NiCr金属相中,不影响CaSZ的稳定性.  相似文献   
23.
The rapidly increasing popularity of mobile devices has changed the methods with which people access various network services and increased network traffic markedly. Over the past few decades, network traffic identification has been a research hotspot in the field of network management and security monitoring. However, as more network services use encryption technology, network traffic identification faces many challenges. Although classic machine learning methods can solve many problems that cannot be solved by port- and payload-based methods, manually extract features that are frequently updated is time-consuming and labor-intensive. Deep learning has good automatic feature learning capabilities and is an ideal method for network traffic identification, particularly encrypted traffic identification; Existing recognition methods based on deep learning primarily use supervised learning methods and rely on many labeled samples. However, in real scenarios, labeled samples are often difficult to obtain. This paper adjusts the structure of the auxiliary classification generation adversarial network (ACGAN) so that it can use unlabeled samples for training, and use the wasserstein distance instead of the original cross entropy as the loss function to achieve semisupervised learning. Experimental results show that the identification accuracy of ISCX and USTC data sets using the proposed method yields markedly better performance when the number of labeled samples is small compared to that of convolutional neural network (CNN) based classifier.  相似文献   
24.
The Journal of Supercomputing - In this paper, we propose a parallel source separation system designed to extract heart and lung sounds from single-channel mixtures. The proposed system is based on...  相似文献   
25.
The explosive growth of Chinese electronic market has made it possible for companies to better understand consumers?? opinion towards their products in a timely fashion through their online reviews. This study proposes a framework for extracting knowledge from online reviews through text mining and econometric analysis. Specifically, we extract product features, detect topics, and identify determinants of customer satisfaction. An experiment on the online reviews from a Chinese leading B2C (Business-to-Customer) website demonstrated the feasibility of the proposed method. We also present some findings about the characteristics of Chinese reviewers.  相似文献   
26.
Oblivious signature-based envelope (OSBE) schemes have demonstrated their potential applications in the protection of users privacy and rights. In an OSBE protocol, an encrypted message can only be decrypted by the receiver who holds a valid signature on a public message, while the sender (encrypter) does not know whether the receiver has the signature or not. Our major contributions in this work lie in the following aspects. We improve the notion of OSBE so that a valid credential holder cannot share his/her credential with other users (i.e., all-or-nothing non-transferability). We clarify the relationship between one-round OSBE and identity-based encryption (IBE) and show that one-round OSBE and semantically secure IBE against the adaptively chosen identity attack (IND-ID-CPA) are equivalent, if the signature in the OSBE scheme is existentially unforgeable against adaptively chosen message attacks. We propose an oblivious access control scheme to protect user privacy without the aid of any zero-knowledge proof. Finally, we also highlight some other novel applications of OSBE, such as attributed-based encryption.  相似文献   
27.
Industrial effluents usually include multicomponent organic solutes. The optimum pH for adsorption of a specific industrial effluent on activated carbon should be determined experimentally because, in general, more than one mechanism is involved. A series of experiments was conducted to establish the influence of the initial hydrogen ion concentration on carbon adsorption of organic solutes. For these studies, powdered activated carbon was used, and the water systems studied included both single component pure organic compounds as well as multicomponent organic wastes. Results indicate that the pH effect upon the effectiveness of carbon adsorption mainly depends upon the nature of the adsorbed substance. In general, the degree of ionisation is the controlling factor for adsorption of ionic organic solutes on activated carbon. Adsorption reaches a maximum at the point of least ionisation of the adsorbate. As the organic compounds become more complex (i.e. longer hydrocarbon chains, higher molecular weights, increased branching), the electrical adsorption forces between activated carbon and ionic organic solutes will govern. Anionic surfactants meet with decreased electronegative repulsive forces at low pH levels, which increase the effectiveness of carbon adsorption. However, the adsorption of a cationic surfactant is increased by an increase in the electronegative carbon surface at high pH levels. When ionic organic solutes become much more complex, like a polymer, the effects of both ionisation and electrical adsorption forces become less important. Instead, the adsorption rate will be controlled by the extent of hydrolysis caused by the pH adjustment. For non-ionic organic solutes, chemical reaction(s) between the adsorbate and the added chemical (acid or base) for pH adjustment is an important controlling factor. Again, hydrolysis is responsible for the breakdown of larger size molecules to smaller sizes. Then an increase in adsorption rate with decreasing molecular weight of adsorbate is expected.  相似文献   
28.
塑料在包装领域有着广泛的应用,其中聚酯(PET)性能优良,应用领域不断扩大。介绍了塑料包装不断通现的新技术,以及塑料包装环保问题的几点思路。  相似文献   
29.
30.
As an effective approach for multi-input multi-output regression estimation problems, a multi-dimensional support vector regression (SVR), named M-SVR, is generally capable of obtaining better predictions than applying a conventional support vector machine (SVM) independently for each output dimension. However, although there are many generalization error bounds for conventional SVMs, all of them cannot be directly applied to M-SVR. In this paper, a new leave-one-out (LOO) error estimate for M-SVR is derived firstly through a virtual LOO cross-validation procedure. This LOO error estimate can be straightway calculated once a training process ended with less computational complexity than traditional LOO method. Based on this LOO estimate, a new model selection methods for M-SVR based on multi-objective optimization strategy is further proposed in this paper. Experiments on toy noisy function regression and practical engineering data set, that is, dynamic load identification on cylinder vibration system, are both conducted, demonstrating comparable results of the proposed method in terms of generalization performance and computational cost.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号