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   5334篇
  免费   154篇
  国内免费   14篇
电工技术   78篇
综合类   17篇
化学工业   1192篇
金属工艺   139篇
机械仪表   230篇
建筑科学   165篇
矿业工程   21篇
能源动力   838篇
轻工业   303篇
水利工程   41篇
石油天然气   87篇
无线电   429篇
一般工业技术   844篇
冶金工业   128篇
原子能技术   38篇
自动化技术   952篇
  2024年   6篇
  2023年   99篇
  2022年   78篇
  2021年   139篇
  2020年   165篇
  2019年   219篇
  2018年   191篇
  2017年   342篇
  2016年   447篇
  2015年   355篇
  2014年   494篇
  2013年   499篇
  2012年   313篇
  2011年   282篇
  2010年   213篇
  2009年   238篇
  2008年   93篇
  2007年   130篇
  2006年   138篇
  2005年   90篇
  2004年   63篇
  2003年   56篇
  2002年   77篇
  2001年   79篇
  2000年   52篇
  1999年   122篇
  1998年   42篇
  1997年   42篇
  1996年   41篇
  1995年   42篇
  1994年   34篇
  1993年   30篇
  1992年   14篇
  1991年   11篇
  1990年   15篇
  1989年   12篇
  1988年   30篇
  1987年   39篇
  1986年   48篇
  1985年   33篇
  1984年   21篇
  1983年   16篇
  1982年   12篇
  1981年   8篇
  1979年   9篇
  1978年   4篇
  1977年   7篇
  1976年   4篇
  1975年   2篇
  1974年   2篇
排序方式: 共有5502条查询结果,搜索用时 15 毫秒
81.
Entering non-alphabetic text for languages such as Japanese and Chinese into a computer typically consists of typing Roman character-based phonemes and selecting the intended Japanese or Chinese character from a list of homophonic candidates. This paper presents a study of four candidate display styles. Three of them, Vertical, Horizontal, and Compact-Horizontal, are used in commercial products. The fourth style, Matrix, is novel. The candidate display style is studied in conjunction with various manual selection devices including Mouse, Numeric Keys, Spacebar, Cursor Key, and Numeric Keypad. Results show that a great deal of time is taken to choose the correct character in both Chinese and Japanese input. The candidate display style affects both input efficiency and subjective preference. Results also show that the Compact-Horizontal display style outperforms other display styles with a normal keyboard but the Matrix display style is the most efficient when used with a Numeric Keypad due to stimulus–response compatibility and the movement efficiency of such a design.  相似文献   
82.
In this paper, a processor allocation mechanism for NoC-based chip multiprocessors is presented. Processor allocation is a well-known problem in parallel computer systems and aims to allocate the processing nodes of a multiprocessor to different tasks of an input application at run time. The proposed mechanism targets optimizing the on-chip communication power/latency and relies on two procedures: processor allocation and task migration. Allocation is done by a fast heuristic algorithm to allocate the free processors to the tasks of an incoming application when a new application begins execution. The task-migration algorithm is activated when some application completes execution and frees up the allocated resources. Task migration uses the recently deallocated processors and tries to rearrange the current tasks in order to find a better mapping for them. The proposed method can also capture the dynamic traffic pattern of the network and perform task migration based on the current communication demands of the tasks. Consequently, task migration adapts the task mapping to the current network status. We adopt a non-contiguous processor allocation strategy in which the tasks of the input application are allowed to be mapped onto disjoint regions (groups of processors) of the network. We then use virtual point-to-point circuits, a state-of-the-art fast on-chip connection designed for network-on-chips, to virtually connect the disjoint regions and make the communication latency/power closer to the values offered by contiguous allocation schemes. The experimental results show considerable improvement over existing allocation mechanisms.  相似文献   
83.
A Web service-based system never fulfills a user's goal unless a failure recovery approach exists. It is inevitable that several Web services may either perish or fail before or during transactions. The completion of a composite process relies on the smooth execution of all constituent Web services. A mediator acts as an intermediary between providers and consumers to monitor the execution of these services. If a service fails, the mediator has to recover the whole composite process or else jeopardize achieving the intended goals. The atomic replacement of a perished Web service usually does not apply because the process of locating a matched Web service is unreliable. Even the system cannot depend on the replacement of the dead service with a com- posite service. In this paper, we propose an automatic renova- tion plan for failure recovery of composite semantic services based on an approach of subdigraph replacement. A replacement subdigraph is posed in lieu of an original subdigraph, which includes the failed service. The replacement is done in two separate phases, ofltine and online, to make the recovery faster. The ofitine phase foresees all possible subdigraphs, pre-calculates them, and ranks several possible replacements. The online phase compensates the unwanted effects and executes the replacement subdigraph in lieu of the original subdigraph. We have evaluated our approach during an experiment and have found that we could recover more than half of the simulated failures. These achievements show a significant improvement compared to current approaches  相似文献   
84.
Snake robots are mostly designed based on single mode locomotion. However, single mode gait most likely could not work effectively when the robot is subject to an unstructured working environment with different measures of terrain complexity. As a solution, mixed mode locomotion is proposed in this paper by synchronizing two types of gaits known as serpentine and wriggler gaits used for non-constricted and narrow space environments, respectively, but for straight line locomotion only. A gait transition algorithm is developed to efficiently change the gait from one to another. This study includes the investigation on kinematics analysis followed by dynamics analysis while considering related structural constraints for both gaits. The approach utilizes the speed of the serpentine gait for open area locomotion and exploits the narrow space access capability of the wriggler gait. Hence, it can increase motion flexibility in view of the fact that the robot is able to change its mode of locomotion according to the working environment.  相似文献   
85.
The breast clinic in the university Hospital Kuala Lumpur was started in August 1993 to cater for the increasing number of women seeking treatment for breast complaints. A four-month survey carried out from January to April 1994 found that Chinese women are more "breast conscious" than Malay and Indian women. The majority of patients were in the reproductive age group. Benign breast diseases form the majority of cases of breast diseases seen. The pick-up rate for new cases of breast cancer was 3.1%. Fine needle aspiration biopsy had a 100% sensitivity during the four-month study, and was a quick method of obtaining a diagnosis.  相似文献   
86.
This study modelled the rational factors that predict fake news sharing behaviour. It also tested the moderating role of social media literacy skills. The focus was on social media users in Nigeria. An online survey was conducted to gather the responses from participants across Nigerian geopolitical zones. Structural equation modelling (SEM) Smart PLS 3.6 was used to analyse the data. We found that information sharing, the news finds me perception, trust in social media and status-seeking lead to fake news sharing among social media users in Nigeria. Specifically, trust in social media and status-seeking had a greater effect on fake news sharing behaviour. We also found that social media literacy skills significantly moderate the relationship between information sharing, status-seeking, the news finds me perception, trust in social media and fake news sharing in such a way that the effects/relationships are stronger among those with low social media literacy skills. This outcome contributes to theory and practice which was highlighted in the concluding aspect of this study.  相似文献   
87.
Wireless Personal Communications - The Internet of Things (IoT) is a concept that has attracted significant attention since the emergence of wireless technology. The knowledge diffusion of IoT...  相似文献   
88.
In this letter, a titanium aluminum carbide (Ti3AlC2) coated D-shaped fiber is proposed and demonstrated as a new saturable absorber (SA) for Q-switched laser pulse generation. In preparing the SA, the Ti3AlC2 powder is dispersed in liquid polyvinyl alcohol (PVA) before the solution is dropped and left to dry onto a polished surface of D-shape fiber. The SA is added to an erbium-doped fiber laser (EDFL) cavity to modulate the cavity loss for Q-switching. The Q-switched laser is obtained at 1 561 nm. The pulse width of the pulses can be varied between 7.4 µs and 5.1 µs with a corresponding repetition rate range from 41.26 kHz to 54.35 kHz, when the pump power is increased from 42.2 mW to 71.5 mW. At 71.5 mW pump, the pulse energy is obtained at 70.3 nJ. The signal-to-noise ratio (SNR) of the fundamental frequency is recorded at 67 dB, which indicates the stability of the laser.  相似文献   
89.
It is very important in engineering design and integrity assessment of pipeline to accurately predict its failure pressure, especially for the pipeline with mechanical damages. This paper numerically investigates the failure pressure of medium and high strength pipelines with scratched dent which is on the outer surface of the pipe. Pipe materials of two different grades are chosen in the analysis which represent medium and high strength steel, respectively. Failure pressure of an intact pipeline with fixed ends is derived analytically. On the basis of the maximum plastic strain failure criterion put forward by previous scholars, failure pressure of finite element models containing dent and scratch defects is determined. Parametric studies are carried out to obtain the influencing rule of the dimensions of dent and scratch. The effects of scratch length and depth on failure pressure with various dent depths are obtained. Finally, a formula is fitted for predicting the failure pressure of pipelines with scratched dents on the basis of finite element results. Compared to burst test data from literature, the proposed formula is proved to be reasonable.  相似文献   
90.
In this study, larvicidal activity of silver nanoparticles (AgNPs) synthesised using apple extract against fourth instar larvae of Aedes aegypti was determined. As a result, the AgNPs showed moderate larvicidal effects against Ae. aegypti larvae (LC50  = 15.76 ppm and LC90  = 27.7 ppm). In addition, comparison of larvicidal activity performance of AgNPs at high concentration prepared using two different methods showed that Ae. aegypti larvae was fully eliminated within the duration of 2.5 h. From X‐ray diffraction, the AgNP crystallites were found to exhibit face centred cubic structure. The average size of these AgNPs as estimated by particle size distribution was in the range of 50–120 nm. The absorption maxima of the synthesised Ag showed characteristic Ag surface plasmon resonance peak. This green synthesis provides an economic, eco‐friendly and clean synthesis route to Ag.Inspec keywords: silver, nanofabrication, X‐ray diffraction, zoology, particle size, nanoparticles, biomedical materials, nanomedicineOther keywords: time 2.5 h, size 50 nm to 120 nm, silver nanoparticle, larvicidal property, instar larvae, Aedes aegypti, larvicidal effect, larvicidal activity performance, X‐ray diffraction, nanoparticle particle size distribution, absorption maxima, silver surface plasmon resonance peak  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