全文获取类型
收费全文 | 15883篇 |
免费 | 1866篇 |
国内免费 | 1499篇 |
专业分类
电工技术 | 1505篇 |
技术理论 | 5篇 |
综合类 | 1828篇 |
化学工业 | 482篇 |
金属工艺 | 286篇 |
机械仪表 | 906篇 |
建筑科学 | 555篇 |
矿业工程 | 385篇 |
能源动力 | 254篇 |
轻工业 | 238篇 |
水利工程 | 222篇 |
石油天然气 | 375篇 |
武器工业 | 178篇 |
无线电 | 2043篇 |
一般工业技术 | 815篇 |
冶金工业 | 296篇 |
原子能技术 | 100篇 |
自动化技术 | 8775篇 |
出版年
2024年 | 18篇 |
2023年 | 100篇 |
2022年 | 173篇 |
2021年 | 220篇 |
2020年 | 305篇 |
2019年 | 315篇 |
2018年 | 291篇 |
2017年 | 352篇 |
2016年 | 414篇 |
2015年 | 558篇 |
2014年 | 822篇 |
2013年 | 933篇 |
2012年 | 1007篇 |
2011年 | 1192篇 |
2010年 | 924篇 |
2009年 | 1069篇 |
2008年 | 1197篇 |
2007年 | 1386篇 |
2006年 | 1278篇 |
2005年 | 1107篇 |
2004年 | 904篇 |
2003年 | 761篇 |
2002年 | 640篇 |
2001年 | 548篇 |
2000年 | 459篇 |
1999年 | 374篇 |
1998年 | 299篇 |
1997年 | 286篇 |
1996年 | 258篇 |
1995年 | 210篇 |
1994年 | 195篇 |
1993年 | 143篇 |
1992年 | 116篇 |
1991年 | 94篇 |
1990年 | 60篇 |
1989年 | 48篇 |
1988年 | 39篇 |
1987年 | 27篇 |
1986年 | 26篇 |
1985年 | 23篇 |
1984年 | 11篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1973年 | 3篇 |
1957年 | 3篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Improving the transient response of power generation systems using automation control in a precise manner is the key issue. We design a fuzzy proportional integral derivative (PID) controller using Matlab and programmable logic controllers (PLCs) for a set point voltage control problem in the automatic voltage regulator (AVR) system. The controller objective is to maintain the terminal voltage all the time under any loads and operational conditions by attaining to the desired range via the regulation of the generator exciter voltage. The main voltage control system uses PLCs to implement the AVR action. The proposed fuzzy controller combines the genetic algorithm (GA), radial-basis function network (RBF-NN) identification and fuzzy logic control to determine the optimal PID controller parameters in AVR system. The RBF tuning for various operating conditions is further employed to develop the rule base of the Sugeno fuzzy system. The fuzzy PID controller (GNFPID) is further designed to transfer in PLCs (STEP 75.5) for implementing the AVR system with improved system response. An inherent interaction between two generator terminal voltage control and excitation current is revealed. The GNFPID controller configures the control signal based on interaction and there by reduces the voltage error and the oscillation in the terminal voltage control process. We achieve an excellent voltage control performance by testing the proposed fuzzy PID controller on a practical AVR system in synchronous generator for improve the transient response. 相似文献
32.
The intermittent wind power in isolated hybrid distributed generation (IHDG) may cause serious problems associated with frequency (f) and power (P) fluctuation. Energy storage devices such as battery, super capacitor, and superconducting magnetic energy storage (SMES) may be used to reduce these fluctuations associated with f and P. This paper presents a study of IHDG power system for improving both f and P deviation profiles with the help of SMES. The studied IHDG power system is consisted of wind turbine generator and diesel engine generator. Both f and P control problems of the studied power system model are addressed in presence or absence of SMES. Fuzzy logic based proportional–integral–derivative (PID) controller with SMES is used for the purpose of minimization of f and P deviations. The different tunable parameters of the PID controller and those of the SMES are tuned by a novel quasi-oppositional harmony search algorithm. Performance study of the IHDG power system model is carried out under different perturbation conditions. The results demonstrate minimum f and P deviations may be achieved by using the proposed fuzzy logic based PID controller along with SMES. 相似文献
33.
Power transformers are protected by different relays that operate independently. Malfunction of each relay has a major role in reducing the reliability of the protection system. In order to mitigate the main drawbacks of the power transformer relays, an overall protection scheme is presented in this paper. This scheme proposes a novel multi criterion algorithm using decision-making based on fuzzy logic. In this paper the outputs of restricted earth fault relay and a directional check unit, are combined with the output of the differential protection relay. Therefore, problems that are pertaining to independent operation of each relay have been mitigated and the relays cover protection blind spots of each other. The improved power transformer protection (IPTP) scheme enhances the sensitivity and reliability of the power transformer protection. Extensive simulations are used to measure the effectiveness and merit of the proposed IPTP relay. The above efforts result in a multi criteria approach for protection of power transformers. 相似文献
34.
《Soils and Foundations》2019,59(5):1313-1323
On the basis of the yield criterion of Matsuoka and Nakai (1974), novel elasto-plastic solutions are obtained for the cavity expansion problem in an anisotropic medium. The solutions are formulated by employing a small-strain analysis in an elastic zone and a large-strain analysis in a plastic zone around the cavity in a soil mass. In light of the initial condition, the plastic radius and the stress in the plastic zone are derived by incorporating the large-strain analysis, the influence of stress anisotropy (K0) and the non-associated flow rule, and two fundamental solutions for the cavity expansion problem under undrained and drained conditions are presented in an anisotropic soil mass. Finally, a comparison with the previous results is performed for verification. 相似文献
35.
Jongwoo Kim Eun Hee Park Young Soon Park Kyung Hee Chun Lynn L. Wiles 《Information Systems Journal》2022,32(1):164-191
Regulations, such as the Health Insurance Portability and Accountability Act (HIPAA), establish standards to protect patients' medical records from security breaches. Insiders' prosocial misbehaviour within healthcare organisations can cause significant damage to relevant stakeholders. Such behaviour without malicious intention needs to be better understood and carefully managed from the perspective of prosocial behaviour. For this study, a research model was developed that includes the factors influencing student nurses' intention to disclose patient health information. The model was empirically tested with nursing students in South Korea with a scenario-based experiment. We find that both altruistic (impact on others) and egoistic (impact on the self) motivations are significantly important in raising situational empathy. On the other hand, an egoistic motivation (impact on the self) significantly affects people's perception of their responsibility, which mediates the relationship between situational empathy and prosocial intention to disclose. The implications of our findings are discussed. 相似文献
36.
This paper presents a highly efficient ternary flash ADC, designed using the innovative gate-overlap tunnel FET (GOTFET) at the 45 nm technology node. The proposed GOTFETs have on-state currents Ion more than double, while the off-state currents Ioff remaining at least an order of magnitude lower than the corresponding values of the standard 45 nm CMOS technology with the same width. Replacing MOSFETs with the proposed GOTFETs significantly reduces the static power consumption and improves performance. However, the higher Ion increases the dynamic power as well. To minimize the dynamic power, we propose a novel complementary GOTFET (CGOT) based comparator design. In addition to the inherent advantages of the GOTFET technology, the proposed design further reduces the dynamic power, such that the final power delay product (PDP) is merely 6.3% of the PDP in conventional CMOS comparator design. In addition to the novelty related to the innovative GOTFET devices, there are at least two-fold circuit-level novelty reported in this work. Firstly, we propose a novel CGOT based comparator circuit design, which, in addition to the advantages of GOTFET, further reduces the dynamic power such that the PDP is less than 1/3rd of the original PDP of the conventional comparator designed with GOTFETs. Secondly, the proposed CGOT based ADC requires only 48 transistors to encode the comparator outputs into the 2-bit ternary output, which is 30% lower than the 70 transistors necessary for the 2-bit CMOS based ternary flash ADC designs reported earlier in the literature. We propose an efficient 2-bit ternary flash ADC with a resolution of 50 mV and input quantized to 9 levels. Subsequently, we benchmark the performance of the proposed CGOT ternary flash ADC with the same ADC circuit implemented using the standard 45 nm CMOS technology library, all corresponding devices having the same width. We demonstrate that in addition to the superior performance than the corresponding CMOS ADC, the proposed CGOT ADC design consumes significantly lower power. The overall PDP of the proposed CGOT ADC is merely 6.3% of the PDP in corresponding CMOS design. 相似文献
38.
In the current article, the influence of three different doses of gamma-rays on the thermally assisted crystal growth in a novel ternary chalcogenide glassy Se78Te20Sn2 semiconductor has been reported in terms of the re-crystallization. The iso-conversional kinetic approach is used in the present study. The variation of crystal growth rate with temperature obeys the Arrhenius relation for all the doses of gamma-rays irradiation. Further analysis confirms that pre-factor K0 of crystal growth rate and the corresponding energy ΔE involved in thermally governed crystallization follows Meyer-Neldel compensation rule (MNCR). Further, we have observed a linear correlation i.e., Further Meyer-Neldel compensation rule (FMNCR) between Meyer-Neldel pre-factor K00 and Meyer-Neldel energy kT0. The observed correlations between these significant parameters (MNCR between K0 & ΔE and FMNCR between K00 & kT0) may open a new gateway for revealing the external effects on crystal growth rate during the iso-conversional analysis of crystallization kinetics. 相似文献
39.
目的研究智能网联汽车手机APP中控制模块的视觉设计与应用,强化视觉设计过程的合理性,为智能汽车HMI设计实践工作提供启示与借鉴。方法首先从用户体验的角度分析APP控制模块存在的视觉设计问题,主要是视觉结构单一、视觉层级混乱、视觉特征缺失,再从行为逻辑的角度思考视觉设计方法,"由面及点"地提出控制模块的视觉设计思路,并结合设计应用案例论证其可行性。结果从合理视觉布局、明确视觉层级和提炼视觉语言的角度提出APP控制模块的视觉设计思路。结论智能网联汽车APP控制模块的视觉设计应该重视行为逻辑的影响。从任务角度思考视觉布局、从行为逻辑的角度思考视觉层级、从行为特征的角度思考视觉语言,提高视觉设计工作的合理性,减少与交互设计工作脱节的现象,强化控制求助的高效性和安全性。 相似文献
40.
Identifying and Verifying Vulnerabilities through PLC Network Protocol and Memory Structure Analysis
Joo-Chan Lee Hyun-Pyo Choi Jang-Hoon Kim Jun-Won Kim Da-Un Jung Ji-Ho Shin Jung-Taek Seo 《计算机、材料和连续体(英文)》2020,65(1):53-67
Cyberattacks on the Industrial Control System (ICS) have recently been
increasing, made more intelligent by advancing technologies. As such, cybersecurity for
such systems is attracting attention. As a core element of control devices, the
Programmable Logic Controller (PLC) in an ICS carries out on-site control over the ICS. A
cyberattack on the PLC will cause damages on the overall ICS, with Stuxnet and Duqu as
the most representative cases. Thus, cybersecurity for PLCs is considered essential, and
many researchers carry out a variety of analyses on the vulnerabilities of PLCs as part of
preemptive efforts against attacks. In this study, a vulnerability analysis was conducted on
the XGB PLC. Security vulnerabilities were identified by analyzing the network protocols
and memory structure of PLCs and were utilized to launch replay attack, memory
modulation attack, and FTP/Web service account theft for the verification of the results.
Based on the results, the attacks were proven to be able to cause the PLC to malfunction
and disable it, and the identified vulnerabilities were defined. 相似文献