全文获取类型
收费全文 | 193821篇 |
免费 | 16012篇 |
国内免费 | 8776篇 |
专业分类
电工技术 | 11746篇 |
技术理论 | 13篇 |
综合类 | 11999篇 |
化学工业 | 30390篇 |
金属工艺 | 10624篇 |
机械仪表 | 11606篇 |
建筑科学 | 14110篇 |
矿业工程 | 5541篇 |
能源动力 | 5400篇 |
轻工业 | 12900篇 |
水利工程 | 3396篇 |
石油天然气 | 11068篇 |
武器工业 | 1435篇 |
无线电 | 22180篇 |
一般工业技术 | 22075篇 |
冶金工业 | 8945篇 |
原子能技术 | 2130篇 |
自动化技术 | 33051篇 |
出版年
2024年 | 913篇 |
2023年 | 3455篇 |
2022年 | 6479篇 |
2021年 | 8698篇 |
2020年 | 6557篇 |
2019年 | 5191篇 |
2018年 | 5880篇 |
2017年 | 6566篇 |
2016年 | 5845篇 |
2015年 | 7776篇 |
2014年 | 9808篇 |
2013年 | 11710篇 |
2012年 | 13350篇 |
2011年 | 16215篇 |
2010年 | 12446篇 |
2009年 | 11627篇 |
2008年 | 10825篇 |
2007年 | 9944篇 |
2006年 | 9995篇 |
2005年 | 8726篇 |
2004年 | 5954篇 |
2003年 | 5155篇 |
2002年 | 4367篇 |
2001年 | 3703篇 |
2000年 | 3634篇 |
1999年 | 4282篇 |
1998年 | 3622篇 |
1997年 | 3029篇 |
1996年 | 2823篇 |
1995年 | 2274篇 |
1994年 | 1833篇 |
1993年 | 1326篇 |
1992年 | 1080篇 |
1991年 | 804篇 |
1990年 | 591篇 |
1989年 | 482篇 |
1988年 | 386篇 |
1987年 | 259篇 |
1986年 | 228篇 |
1985年 | 138篇 |
1984年 | 140篇 |
1983年 | 98篇 |
1982年 | 92篇 |
1981年 | 75篇 |
1980年 | 63篇 |
1979年 | 30篇 |
1978年 | 25篇 |
1977年 | 24篇 |
1976年 | 26篇 |
1975年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
杨宇 《中国室内装饰装修天地》2006,(7):54-61
华风气象影视大楼总面积4万平方米,根据空间功能不同分为办公大楼和商务写字楼两部分,办公大楼是集演播室、制作机房、办公室为一体的九层综合性建筑。设计师杨宇在刚接触到这个项目的时候,面对的是一个既成事实的建筑。 相似文献
2.
Guangbin Yang 《Reliability, IEEE Transactions on》2002,51(3):288-293
ESS (environmental stress screening) has been extensively used to reduce infant mortality by precipitating defects. The existing ESS plans precipitate defects by stressing all products for specified durations. The plans usually require long screen durations to allow nearly all defective items to fail, and thus generate excessive aging effects on good items. For some products, failures are defined in terms of performance characteristics exceeding their critical values. This paper describes the principles of using degradation measurements of performance characteristics to screen the products. In an ESS, the performance characteristics of defective items degrade considerably faster than those of good ones, yielding a bimodal distribution of the characteristics. As screen duration increases, the 2 modes of the distribution shift apart. It is possible to find a tightened critical value to weed out the defective items before they fail. This paper, based on these principles, further designs the optimal 2-level screen plans which minimize a segment of life-cycle cost and which simultaneously meet the reliability requirement. The minimum cost is achieved by choosing optimal part-level and unit-level screen durations and tightened critical values of parts. A numerical example is followed by discussion. Because the ESS regime of this paper allows defective parts to be screened out before they fail, the developed optimal ESS plans can reduce life-cycle cost, shorten part-level screen duration, and alleviate aging effects on good products 相似文献
3.
Jian-Bo Yang 《国际自动化与计算杂志》2006,3(1):I0001-I0002
The UK-China Research Network on Intelligent Automation, Computing and Manufacturing has been established since September 2004 by grants from the Engineering and Physical Sciences Research Council (EPSRC) of the UK and the National Natural Science Foundation of China. The initiative of the network is motivated by the last visit of the UK Science Minister Lord Sainsbury to China to open the first UK-China Hi-Tech Forum and by the current EPSRC initiative to set up specific network programmes in collaboration with partners in China. 相似文献
4.
Poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐para‐phenylene vinylene] (MEH‐PPV)/silica nanoparticle hybrid films were prepared and characterised. Three kinds of materials were compared: parent MEH‐PPV, MEH‐PPV/silica (hybrid A films), and MEH‐PPV/coupling agent MSMA/silica (hybrid B films), in which MSMA is 3‐(trimethoxysilyl) propyl methacrylate. It was found that the hybrid B films could significantly prevent macrophase separation, as evidenced by scanning electron and fluorescence microscopy. Furthermore, the thermal characteristics of the hybrid films were largely improved in comparison with the parent MEH‐PPV. The UV‐visible absorption spectra suggested that the incorporation of MSMA‐modified silica into MEH‐PPV could confine the polymer chain between nanoparticles and thus increase the conjugation length. The photoluminescence (PL) studies also indicated enhancement of the PL intensity and quantum efficiency by incorporating just 2 wt% of MSMA‐modified silica into MEH‐PPV. However, hybrid A films did not show such enhancement of optoelectronic properties as the hybrid B films. The present study suggests the importance of the interface between the luminescent organic polymers and the inorganic silica on morphology and optoelectronic properties. Copyright © 2004 Society of Chemical Industry 相似文献
5.
本文评价了塑料闪烁片用作软β核素探测器时的计数效率、β谱、本底谱和康普顿电子谱的特征。文中强调:采用胶合光导剂构成的系统是一种新型探测器(软β核素内部样品塑料闪烁探测器)。本文提出内部样品固体探测器、胶合光导剂和胶合闪烁光导剂的新概念。 相似文献
6.
7.
On effective offloading services for resource-constrained mobile devices running heavier mobile internet applications 总被引:1,自引:0,他引:1
Kun Yang Shumao Ou Hsiao-Hwa Chen 《Communications Magazine, IEEE》2008,46(1):56-63
Rapid advances in wireless mobile network technologies and mobile handsets (MHs) facilitate ubiquitous infrastructure that can support a range of mobile services and applications in addition to conventional mobile Internet access. One recent trend is to effectively run desktop PC-oriented heavier applications on MHs. However, due to their miniature, portable size, MHs are resource-constrained and therefore, running these applications directly on an MH is not satisfactory given a user's expectations. To cope with this problem, this article proposes a novel offloading service that can seamlessly offload some of the tasks of a mobile application from an MH to nearby, resource-rich PCs (called surrogates). The system architecture and key components of the proposed offloading service are presented, prototyped, and evaluated. The results of experiments and simulations have demonstrated the effectiveness and efficiency of this offloading service for mobile applications. 相似文献
8.
Seyeong Choi Alouini M.-S. Qaraqe K.A. Hong-Chuan Yang 《Wireless Communications, IEEE Transactions on》2008,7(2):495-499
We propose and analyze new finger assignment techniques that are applicable for RAKE receivers in the soft handover (SHO) region. Specifically, extending the results for the case of two-base station (BS), we consider the multi-BS situation, attack the statistics of several correlated generalized selection combining (GSC) stages, and provide closed-form expressions for the statistics of the output signal-to-noise ratio (SNR). By investigating the tradeoff among the error performance, the average number of required path estimations/comparisons, and the SHO overhead, we show through numerical examples that the new schemes offer commensurate performance in comparison with more complicated GSC-based diversity systems while requiring a smaller estimation load and SHO overhead. 相似文献
9.
10.