全文获取类型
收费全文 | 7557篇 |
免费 | 601篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 121篇 |
综合类 | 2篇 |
化学工业 | 1934篇 |
金属工艺 | 275篇 |
机械仪表 | 452篇 |
建筑科学 | 159篇 |
矿业工程 | 1篇 |
能源动力 | 370篇 |
轻工业 | 658篇 |
水利工程 | 22篇 |
石油天然气 | 5篇 |
无线电 | 1389篇 |
一般工业技术 | 1637篇 |
冶金工业 | 351篇 |
原子能技术 | 114篇 |
自动化技术 | 683篇 |
出版年
2024年 | 3篇 |
2023年 | 84篇 |
2022年 | 95篇 |
2021年 | 202篇 |
2020年 | 175篇 |
2019年 | 191篇 |
2018年 | 242篇 |
2017年 | 288篇 |
2016年 | 284篇 |
2015年 | 254篇 |
2014年 | 355篇 |
2013年 | 538篇 |
2012年 | 531篇 |
2011年 | 691篇 |
2010年 | 440篇 |
2009年 | 479篇 |
2008年 | 389篇 |
2007年 | 316篇 |
2006年 | 314篇 |
2005年 | 265篇 |
2004年 | 244篇 |
2003年 | 240篇 |
2002年 | 192篇 |
2001年 | 192篇 |
2000年 | 156篇 |
1999年 | 125篇 |
1998年 | 185篇 |
1997年 | 113篇 |
1996年 | 102篇 |
1995年 | 75篇 |
1994年 | 66篇 |
1993年 | 38篇 |
1992年 | 39篇 |
1991年 | 41篇 |
1990年 | 31篇 |
1989年 | 30篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 23篇 |
1985年 | 22篇 |
1984年 | 18篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有8173条查询结果,搜索用时 93 毫秒
61.
Sil-Gu Mun Jung-Hyung Moon Ki-Man Choi Jin-Serk Baik Chang-Hee Lee 《Photonics Technology Letters, IEEE》2007,19(21):1729-1731
We propose and demonstrate a wavelength-division-multiplexed passive optical network by employing double-contact Fabry-Perot laser diodes (F-P LDs) without a seed light injection. To avoid the high mode partition noise at low frequency, we use a binary phase-shift keying as a modulation format at a low relative intensity noise window. An error-free transmission is achieved by compensating a lasing envelope shift due to temperature variation with the double-contact F-P LD. 相似文献
62.
明眸晧齿,笑容爽朗,脸部轮廓分明。看到袁泉,马上会有清冽甘甜的感觉,一如她的名字,仿佛夏日里活力天然的一泓清泉。从《春天的狂想》到娃哈哈广告中的美丽少女,袁泉给人的印象一直是青春、健康而甜美的,举手投足,一颦一笑,洋溢着独有的耀眼活力。不久前,这位活力闰女更是担任了“中国女性健康白皮书系列活动”的形象大使。作为宣传女性健康的代言人,袁泉呼吁,要让更多的女性认识到:健康的身体才是美丽人生的根基。[编者按] 相似文献
63.
Jeongbae Kim Hee Youl Kwak Dong Won Lee 《Journal of Mechanical Science and Technology》2007,21(12):2159-2167
In this study, we highlighted differences in the standards used in performance tests of solar collectors. We analyzed testing
results for different types of solar collectors to determine the effects of the collector area and mass flow rate, which were
not necessarily consistent across all tests. Our analysis showed that the factor,F′ (τα), including collector efficiency factor (F′), could be correlated with the flow rate or area regardless of the collector type. Moreover, the collector loss coefficient
(F′U
L
) per flow rate or area for an evacuated collector was less that of a flat-plate collector; this was also correlated with
the flow rate or area, regardless of the type of evacuated collector. As a result of this analysis, we propose a modified
heat loss coefficient that includes the effects of all parameters that can be considered in a performance test and show that
this coefficient could better describe the thermal characteristics of various types of solar collectors. 相似文献
64.
Wu Li Yann-Hang Lee Wei-Tek Tsai Jingjing Xu Young-Sung Son Jun-Hee Park Kyung-Duk Moon 《Service Oriented Computing and Applications》2012,6(1):65-79
A smart home usually has a variety of devices or home appliance, instead of designing software for a specific home, this paper
proposes a service-oriented framework with a set of ontology systems to support service and device publishing, discovery of
devices and their services, composition of control software using existing control services that wrap devices, deployment,
and execution of the composed service in an computing environment, monitoring the execution, and recovery from device failure.
The ontology systems specify semantic information about devices, services, and workflows used in various smart home, and users
can compose and recompose services for their specific needs. New devices, workflows, and services can be added into ontology.
Most of the steps in this process can be automated including code generation. For example, service composition will be carried
out in three steps: abstract workflow design, function construction, and device discovery, and different codes can be generated
for different computing platforms such as Java and Open Services Gateway initiative environments. In this way, a variety of
smart home can be constructed rapidly using the framework by discovery and composition using existing services and workflows.
This paper illustrates this framework using a media control example to illustrate the ontology, discovery, composition, deployment,
execution, monitoring, and recovery. 相似文献
65.
Moon Ho Lee Jong Oh Park Yasuhiko Yasuda 《Multidimensional Systems and Signal Processing》1990,1(4):389-398
in this paper, simple 1-D and 2-D systolic array for realizing the discrete cosine transform (DCT) based on the discrete Fourier transform (DFT) fo an input sequence are presented. The proposed arrays are obtained by a simple modified DFT (MDFT) and an inverse DFT (IDFT) version of the Goertzel algorithm combined with Kung's approach. The 1-D array requiresN cells, one multiplier and takesN clock cycles to produce a completeN-point DCT. The 2-D array takes N clock cycles, faster than the 1-D array, but the area complexity is larger. A continuous flow of input data is allowed and no idle time is required between the input sequences. 相似文献
66.
Jeong Won Kim Hee Won Kang Dong-Hwan Hwang Sang Jeong Lee 《International Journal of Control, Automation and Systems》2012,10(3):529-535
A signal tracking method of GNSS receivers for spinning vehicles is proposed in order to eliminate the influence of spinning to the GNSS signal of a vehicle. In the proposed method, a rotation tracking loop is added into the carrier tracking loop of a conventional GNSS receiver. The proposed method was verified through computer simulations and an experiment for live GPS signals. The results show that the proposed method gives an accurate tracking performance. 相似文献
67.
Sung Kyung Hong Sang Cheol Leev Jae Won Han Young-sun Ryuh 《International Journal of Control, Automation and Systems》2012,10(5):1000-1004
To achieve the goal of low-cost MEMS gyros for the precise self-localization of mobile robots, this paper presents a simple, yet effective method to minimize drifts on the heading angle by combining measurements from a gyro with measurements from wheel encoders (odometry). The main idea of the proposed approach is to estimate the accuracy of both sensors as a function of the actual maneuver being carried out, and then the output of both sensors are fused by the complementary filter taking into account the maneuvering conditions. The proposed method is applied to a mobile robot and the experimental data demonstrate the effectiveness of this approach. 相似文献
68.
69.
70.
Yeonsil Moon Changmok Lim Yeahoon Kim Won-Jin Moon 《International journal of molecular sciences》2021,22(6)
The role of the blood–brain barrier (BBB) breakdown has been recognized as being important in Alzheimer’s disease pathogenesis. We aimed to evaluate whether regional BBB integrity differed according to sex and whether differences in BBB integrity changed as a consequence of aging or cognitive decline, using dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI). In total, 75 participants with normal cognition (NC) or mild cognitive impairment (MCI) underwent cognitive assessments and MRI examination including DCE-MRI. Regional Ktrans was calculated in cortical regions and the Patlak permeability model was used to calculate BBB permeability (Ktrans, min−1). Females had a lower median Ktrans in the cingulate and occipital cortices. In the “older old” group, sex differences in Ktrans were only observed in the occipital cortex. In the MCI group, sex differences in Ktrans were only observed in the occipital cortex. Age was the only predictor of cognitive assessment scores in the male MCI group; however, educational years and Ktrans in the occipital cortex could predict cognitive scores in the female MCI group. Our study revealed that females may have better BBB integrity in cingulate and occipital cortices. We also found that sex-related differences in BBB integrity are attenuated with aging or cognitive decline. 相似文献