全文获取类型
收费全文 | 55209篇 |
免费 | 6054篇 |
国内免费 | 4414篇 |
专业分类
电工技术 | 4650篇 |
技术理论 | 18篇 |
综合类 | 7429篇 |
化学工业 | 1548篇 |
金属工艺 | 616篇 |
机械仪表 | 3031篇 |
建筑科学 | 4214篇 |
矿业工程 | 1497篇 |
能源动力 | 802篇 |
轻工业 | 976篇 |
水利工程 | 1370篇 |
石油天然气 | 917篇 |
武器工业 | 1034篇 |
无线电 | 8143篇 |
一般工业技术 | 3275篇 |
冶金工业 | 1919篇 |
原子能技术 | 139篇 |
自动化技术 | 24099篇 |
出版年
2024年 | 119篇 |
2023年 | 599篇 |
2022年 | 1182篇 |
2021年 | 1487篇 |
2020年 | 1598篇 |
2019年 | 1171篇 |
2018年 | 1088篇 |
2017年 | 1463篇 |
2016年 | 1751篇 |
2015年 | 2079篇 |
2014年 | 3909篇 |
2013年 | 3515篇 |
2012年 | 4326篇 |
2011年 | 4562篇 |
2010年 | 3633篇 |
2009年 | 3781篇 |
2008年 | 4034篇 |
2007年 | 4297篇 |
2006年 | 3896篇 |
2005年 | 3427篇 |
2004年 | 2937篇 |
2003年 | 2559篇 |
2002年 | 1805篇 |
2001年 | 1538篇 |
2000年 | 1184篇 |
1999年 | 820篇 |
1998年 | 566篇 |
1997年 | 456篇 |
1996年 | 347篇 |
1995年 | 292篇 |
1994年 | 253篇 |
1993年 | 196篇 |
1992年 | 134篇 |
1991年 | 105篇 |
1990年 | 73篇 |
1989年 | 73篇 |
1988年 | 66篇 |
1987年 | 32篇 |
1986年 | 33篇 |
1985年 | 34篇 |
1984年 | 44篇 |
1983年 | 36篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 17篇 |
1977年 | 8篇 |
1965年 | 11篇 |
1964年 | 14篇 |
1961年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
11.
Massive Open Online Courses (MOOCs) are becoming an essential source of information for both students and teachers. Noticeably, MOOCs have to adapt to the fast development of new technologies; they also have to satisfy the current generation of online students. The current MOOCs’ Management Systems, such as Coursera, Udacity, edX, etc., use content management platforms where content are organized in a hierarchical structure. We envision a new generation of MOOCs that support interpretability with formal semantics by using the SemanticWeb and the online social networks. Semantic technologies support more flexible information management than that offered by the current MOOCs’ platforms. Annotated information about courses, video lectures, assignments, students, teachers, etc., can be composed from heterogeneous sources, including contributions from the communities in the forum space. These annotations, combined with legacy data, build foundations for more efficient information discovery in MOOCs’ platforms. In this article we review various Collaborative Semantic Filtering technologies for building Semantic MOOCs’ management system, then, we present a prototype of a semantic middle-sized platform implemented at Western Kentucky University that answers these aforementioned requirements. 相似文献
12.
This paper introduces a simultaneous process optimization and heat integration approach, which can be used directly with the rigorous models in process simulators. In this approach, the overall process is optimized utilizing external derivative-free optimizers, which interact directly with the process simulation. The heat integration subproblem is formulated as an LP model and solved simultaneously during optimization of the flowsheet to update the minimum utility and heat exchanger area targets. A piecewise linear approximation for the composite curve is applied to obtain more accurate heat integration results. This paper describes the application of this simultaneous approach for three cases: a recycle process, a separation process and a power plant with carbon capture. Case study results indicate that this simultaneous approach is relatively easy to implement and achieves higher profit and lower operating cost and, in the case of the power plant example, higher net efficiency than the sequential approach. 相似文献
13.
14.
This paper describes algorithms that use demand-side management to address large-scale integration of wind power. In particular, demand response (DR) is used to manage wind power intermittency by shifting the time that electrical power system loads occur in response to real-time prices and wind availability. An economic dispatch with transmission, DR capacity and operational constraints is used to model the operation of a transmission constrained system with a high penetration of wind power. This optimization model is used to determine the optimal sizing and distribution of DR given a fixed budget for customer incentives and the installation of enabling technology. We demonstrate the effectiveness of the operational model based on a simple PJM 5-bus system and an IEEE 118-bus system. Simulation results show that transmission constraints have a greater effect on sizing of DR capacity than the location of wind power, which means that buses electrically close to congested lines tend to have higher incentives to deploy DR resources than other buses. The second part of the work examines optimal siting of technology that enables DR based on the frequency of DR based load changes, which are generally a function of the network location. 相似文献
15.
To realize joint optimization of spatial diversity and equalization combining in the intersymbol interference (ISI) channel, an iterative equalization combining algorithm is proposed. The proposed algorithm uses the coefficients of Turbo equalization to calculate the combination weights without estimating the signal to noise ratio in each diversity branch. The equalized symbols from different diversity branches are combined, and the extrinsic information output from the decoder is fed back to the equalizers, so as to exchange soft information between the equalizers and the decoder. The performance of the proposed algorithm is analyzed using the extrinsic information transfer (EXIT) chart and verified by simulations. Results show that our approach fully exploits time domain information from the multipath channel and spatial domain information from multi receiving antennas, which efficiently improve the performance of the receiver in the severe ISI channel. 相似文献
17.
Health information technology (IT) is a promising way to achieve safer medication management in the delivery of healthcare. However, human factors/ergonomics dictates that in order to make the complex, cognitive work of healthcare delivery safer, health IT must properly support human cognition. This means, for example, that new health IT must reduce, not increase, workload during safety-critical tasks. The present study was the first to quantitatively assess the short- and long-term impact of bar coded medication administration (BCMA) IT on nurses' mental workload as well as on perceived medication safety. One-hundred seventy registered nurses across 3 dissimilar clinical units at an academic, freestanding pediatric hospital in the Midwest US participated in surveys administered before, 3 months after, and 12 months after the hospital implemented BCMA. Nurses rated their external mental workload (interruptions, divided attention, being rushed) and internal mental workload (concentration, mental effort) during medication administration tasks as well as the likelihood of each of three medication safety events: medication administration errors, medication errors on the clinical unit, and clinical unit-level adverse drug events. Clinical unit differences were assessed. Findings generally confirmed the hypothesis that external but not internal mental workload was associated with the perceived likelihood of a medication safety event. Comparisons of mental workload from pre- to post-BCMA revealed statistically significant changes in the critical care unit only. Medication safety appeared to improve over the long term in the hematology/oncology unit only. In the critical care and medical/surgical units, medication safety exhibited short-term improvements that were eliminated over time. Changes in mental workload and medication safety, two classically microergonomic constructs, were deeply embedded in macroergonomic phenomena. These included the fit between the BCMA system and the nature of nursing work, the process of BCMA implementation, and BCMA interactions with concurrent changes occurring in the hospital. Findings raise questions about achieving sustainable performance improvement with health IT as well as the balance between micro- and macroergonomic approaches to studying technology change.Relevance to industryDesigners must consider how technology changes cognitive work, including mental workload. Hospitals and other implementers of technology must ensure that new technology fits its users, their tasks, and the context of use, which may entail tailoring implementation, for example, to specific clinical units. Evaluators must look over time to assess both changes in cognitive work and implementation issues. Healthcare practitioners must also recognize that new technology means a complex transformation to an already complex sociotechnical system, which calls for a macroergonomic approach to design and analysis. 相似文献
18.
本文对运营商信息安全集中管控架构演进和信息安全管控策略面临的问题进行了深入分析,提出了信息安全集中管控架构的演进方向建议及对信息安全监控策略工作优化的若干意见。 相似文献
19.
Bin Zhang Xuesong Jiang Fei Shen Xueming He Yong Fang Qiuhui Hu 《International Journal of Food Science & Technology》2021,56(6):2588-2595
This work intends to develop an online experimental system for screening of deoxynivalenol (DON) contamination in whole wheat meals by visible/near-infrared (Vis/NIR) spectroscopy and computer vision coupling technology. Spectral and image information of samples with various DON levels was collected at speed of 0.15 m s−1 on a conveyor belt. The two-type data were then integrated and subjected to chemometric analysis. Discriminant analysis showed that samples could be classified by setting 1000 μg kg−1 as the cut-off value. The best correct classified rate obtained in prediction was 93.55% based on fusion of spectral and image features, with reduced prediction uncertainty as compared to single feature. However, quantification of DON by quantitative analysis was not successful due to poor model performance. These results indicate that, although not accurate enough to provide conclusive result, this coupling technology could be adopted for rapid screening of DON contamination in cereals and feeds during processing. 相似文献