全文获取类型
收费全文 | 94225篇 |
免费 | 15650篇 |
国内免费 | 1468篇 |
专业分类
电工技术 | 2930篇 |
技术理论 | 4篇 |
综合类 | 2342篇 |
化学工业 | 26095篇 |
金属工艺 | 2587篇 |
机械仪表 | 3201篇 |
建筑科学 | 4310篇 |
矿业工程 | 1038篇 |
能源动力 | 2614篇 |
轻工业 | 11151篇 |
水利工程 | 1013篇 |
石油天然气 | 1346篇 |
武器工业 | 190篇 |
无线电 | 14319篇 |
一般工业技术 | 18483篇 |
冶金工业 | 7040篇 |
原子能技术 | 589篇 |
自动化技术 | 12091篇 |
出版年
2024年 | 146篇 |
2023年 | 618篇 |
2022年 | 1311篇 |
2021年 | 2018篇 |
2020年 | 2657篇 |
2019年 | 4161篇 |
2018年 | 4244篇 |
2017年 | 4600篇 |
2016年 | 4998篇 |
2015年 | 5238篇 |
2014年 | 5697篇 |
2013年 | 7794篇 |
2012年 | 5422篇 |
2011年 | 5641篇 |
2010年 | 5150篇 |
2009年 | 5116篇 |
2008年 | 4741篇 |
2007年 | 4424篇 |
2006年 | 3911篇 |
2005年 | 3218篇 |
2004年 | 3111篇 |
2003年 | 3407篇 |
2002年 | 3881篇 |
2001年 | 3314篇 |
2000年 | 2439篇 |
1999年 | 1676篇 |
1998年 | 2372篇 |
1997年 | 1602篇 |
1996年 | 1255篇 |
1995年 | 940篇 |
1994年 | 740篇 |
1993年 | 696篇 |
1992年 | 457篇 |
1991年 | 386篇 |
1990年 | 383篇 |
1989年 | 339篇 |
1988年 | 304篇 |
1987年 | 271篇 |
1986年 | 248篇 |
1985年 | 279篇 |
1984年 | 198篇 |
1983年 | 168篇 |
1982年 | 152篇 |
1981年 | 162篇 |
1980年 | 181篇 |
1979年 | 110篇 |
1978年 | 111篇 |
1977年 | 159篇 |
1976年 | 268篇 |
1975年 | 95篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Chang Tianle 《中国油气》2002,9(2)
China is likely to resume operation of its oil futures this year, according to reports from the media about a futures conference organized by the Shanghai Futures Exchange (SHFE) in late May. "As China has become an important oil producer and consumer,the demand for our own oil futures market emerges,which will help China oil-related enterprises hedge risks," said Li Ruisheng, vice president of PetroChina's refining and marketing company. 相似文献
102.
Mueller C. Sullivan C. Chang W. Hall D. Zino J. Rice R. 《Quantum Electronics, IEEE Journal of》1980,16(3):363-372
Calculated butt coupling efficiency between a GaAlAs double heterostructure laser and a single-mode LiNbO3 Ti-diffused optical waveguide is presented in this paper as a function of the transverse displacement, the angular alignment, the longitudinal separation between the laser and the waveguide end surfaces, the radiation field of the laser diode and its dependence on the laser diode structure, and the mode profile of the waveguide and its dependence on experimental diffusion parameters. The maximum efficiency is less than 40 percent because of the mismatch between the waveguide mode and the laser radiation, caused primarily by the experimental limitations in their structures. The effect of the reflection of the waveguide end surface on the laser oscillation has also been estimated. 相似文献
103.
A direct method for transient stability analysis of a multimachine power system is presented. Emphasis is placed on the detailed development and evaluation of the proposed method in transient stability assessment. An energy-type Lyapunov function, taking into account the effect of transfer conductance, is introduced first. The potential energy boundary surface method is then adopted to determine the critical energy value quickly. The main computational burden in the direct method lies in the reduction of the admittance matrices. In this paper, an efficient reduction technique incorporating the sparsity technique and compensation theory is developed. Finally, the proposed method was tested on the Taipower system, which is the only power system in Taiwan. The results obtained confirm the validity and accuracy of the proposed method, and hence demonstrate the superiority and potential of the direct method in real power system applications. 相似文献
104.
E-enforcement, or electronic enforcement, is the use of electronic tools in law enforcement. We shall distinguish between the first and second generations of e-enforcement. The first generation of e-enforcement tools provided means of "automated enforcement". This article is based on our research into the effects of two forms of second generation e-enforcement: the digital tachograph and 'Weigh in Motion' (WIM). The digital tachograph replaces the analog tachograph in all heavy goods vehicles within the European Union. The equipment registers drivers' driving and rest times. Weigh in Motion with Video (WIM-Vid) is a system involving sensors in the road and cameras, which detect and register overloading of heavy goods vehicles. The WIM-Vid system was developed and implemented in the Netherlands and is currently attracting international attention. We compare the situation prior to the introduction of these e-enforcement measures to the situation after the introduction of e-enforcement. 相似文献
105.
A new method to predict the critical heat flux (CHF) is proposed, based on the fuzzy clustering and artificial neural network. The fuzzy clustering classifies the experimental CHF data into a few data clusters (data groups) according to the data characteristics. After classification of the experimental data, the characteristics of the resulting clusters are discussed with emphasis on the distribution of the experimental conditions and physical mechanism. The CHF data in each group are trained in an artificial neural network to predict the CHF. The artificial neural network adjusts the weight so as to minimize the prediction error within the corresponding cluster. Application of the proposed method to the KAIST CHF data bank shows good prediction capability of the CHF, better than other existing methods. 相似文献
106.
Kuhn R. De Mori R. 《IEEE transactions on pattern analysis and machine intelligence》1995,17(5):449-460
This article describes a new method for building a natural language understanding (NLU) system, in which the system's rules are learnt automatically from training data. The method has been applied to design of a speech understanding (SU) system. Designers of such systems rely increasingly on robust matchers to perform the task of extracting meaning from one or several word sequence hypotheses generated by a speech recognizer. We describe a new data structure, the semantic classification tree (SCT), that learns semantic rules from training data and can be a building block for robust matchers for NLU tasks. By reducing the need for handcoding and debugging a large number of rules, this approach facilitates rapid construction of an NLU system. In the case of an SU system, the rules learned by an SCT are highly resistant to errors by the speaker or by the speech recognizer because they depend on a small number of words in each utterance. Our work shows that semantic rules can be learned automatically from training data, yielding successful NLU for a realistic application 相似文献
107.
A dedicated low-power CMOS transponder microchip is presented as part of a novel telemetry implant for biomedical applications. This mixed analog-digital circuit contains an identification code and collects information on physiological parameters, i.e., body temperature and physical activity, and on the status of the battery. To minimize the amount of data to be transmitted, a dedicated signal processing algorithm is embedded within its circuitry. All telemetry functions (encoding, modulation, generation of the carrier) are implemented on the integrated circuit. Emphasis is on a high degree of flexibility towards sensor inputs and internal data management, extreme miniaturization, and low-power consumption to allow a long implantation lifetime 相似文献
108.
Tahui Wang Chimoon Huang Chou P.C. Chung S.S.-S. Tse-En Chang 《Electron Devices, IEEE Transactions on》1994,41(9):1618-1622
A two-dimensional numerical simulation including a new interface state generation model has been developed to study the performance variation of a LDD MOSFET after a dc voltage stress. The spatial distribution of hot carrier induced interface states is calculated with a breaking silicon-hydrogen bond model. Mobility degradation and reduction of conduction charge due to interface traps are considered. A 0.6 μm LDD MOSFET was fabricated. The drain current degradation and the substrate current variation after a stress were characterized to compare the simulation. A reduction of the substrate current at Vg ≃0.5 Vd in a stressed device was observed from both the measurement and the simulation. Our study reveals that the reduction is attributed to a distance between a maximum channel electric field and generated interface states 相似文献
109.
Suk Lee Kyung Chang Lee Man Hyung Lee Harashima F. 《Industrial Electronics, IEEE Transactions on》2002,49(3):693-701
This paper focuses on a method to integrate mobile devices such as a mobile robot, automated guided vehicle, and unmanned container transporter to form an automated material handling system. In this paper, the stationary devices are connected via a Profibus network while the mobile devices are communicating via an IEEE 802.11 wireless LAN. In order to integrate these two networks, a protocol converter is developed on a PC platform that runs two interacting processes with shared internal buffers. The protocol converter performs a role of translator between two different protocols by converting the format of a data frame. In addition to this basic conversion function, the protocol converter has a virtual polling algorithm to reduce the uncertainty involved in accessing the wireless network. Finally, the integrated network. of Profibus and IEEE 802.11 is experimentally evaluated for its data latency and throughput, which shows the feasibility of the Profibus-IEEE 802.11 network for industrial applications involving mobile devices 相似文献
110.