全文获取类型
收费全文 | 36076篇 |
免费 | 4118篇 |
国内免费 | 2735篇 |
专业分类
电工技术 | 3316篇 |
技术理论 | 1篇 |
综合类 | 4021篇 |
化学工业 | 1833篇 |
金属工艺 | 1218篇 |
机械仪表 | 2704篇 |
建筑科学 | 1801篇 |
矿业工程 | 955篇 |
能源动力 | 589篇 |
轻工业 | 2915篇 |
水利工程 | 757篇 |
石油天然气 | 1289篇 |
武器工业 | 395篇 |
无线电 | 4274篇 |
一般工业技术 | 1625篇 |
冶金工业 | 817篇 |
原子能技术 | 271篇 |
自动化技术 | 14148篇 |
出版年
2024年 | 81篇 |
2023年 | 363篇 |
2022年 | 791篇 |
2021年 | 915篇 |
2020年 | 981篇 |
2019年 | 816篇 |
2018年 | 760篇 |
2017年 | 962篇 |
2016年 | 1136篇 |
2015年 | 1424篇 |
2014年 | 2214篇 |
2013年 | 1959篇 |
2012年 | 2688篇 |
2011年 | 2991篇 |
2010年 | 2324篇 |
2009年 | 2273篇 |
2008年 | 2483篇 |
2007年 | 3007篇 |
2006年 | 2601篇 |
2005年 | 2290篇 |
2004年 | 1863篇 |
2003年 | 1756篇 |
2002年 | 1338篇 |
2001年 | 1114篇 |
2000年 | 865篇 |
1999年 | 602篇 |
1998年 | 454篇 |
1997年 | 364篇 |
1996年 | 304篇 |
1995年 | 267篇 |
1994年 | 211篇 |
1993年 | 169篇 |
1992年 | 115篇 |
1991年 | 82篇 |
1990年 | 54篇 |
1989年 | 62篇 |
1988年 | 48篇 |
1987年 | 35篇 |
1986年 | 20篇 |
1985年 | 19篇 |
1984年 | 20篇 |
1983年 | 32篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1959年 | 3篇 |
1956年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
资源型产业发展为推进国家经济增长和工业化进程提供了重要保障。为深入了解资源型产业的研究情况,以CNKI数据库为数据源,搜集2000—2020年关于资源型产业的核心及以上期刊论文,利用CiteSpace软件从发文作者与研究机构分布、关键词共现网络和时区图谱等方面,绘制知识图谱,进行可视化分析。研究发现:资源型产业领域的研究成果愈加丰富,但研究群体间联系合作较少,且现有的合作研究主要集中在所处地域资源富集和具有学科优势的研究机构及学者;资源型产业领域的研究热点可概括为产业发展、资源型城市、产业集群、产业结构、产业链和产业集聚等方面;针对资源型产业领域未来可从资源型产业相关理论研究、创新发展模式和可持续发展等方面深入展开。 相似文献
3.
Software is a central component in the modern world and vastly affects the environment’s sustainability. The demand for energy and resource requirements is rising when producing hardware and software units. Literature study reveals that many studies focused on green hardware; however, limited efforts were made in the greenness of software products. Green software products are necessary to solve the issues and problems related to the long-term use of software, especially from a sustainability perspective. Without a proper mechanism for measuring the greenness of a particular software product executed in a specific environment, the mentioned benefits will not be attained. Currently, there are not enough works to address this problem, and the green status of software products is uncertain and unsure. This paper aims to identify the green measurements based on sustainable dimensions in a software product. The second objective is to reveal the relationships between the elements and measurements through empirical study. The study is conducted in two phases. The first phase is the theoretical phase, where the main components, measurements and practices that influence the sustainability of a software product are identified. The second phase is the empirical study that involved 103 respondents in Malaysia investigating current practices of green software in the industrial environment and further identifying the main sustainability dimensions and measurements and their impact on achieving green software products. This study has revealed seven green measurements of software product: Productivity, Usability, Cost Reduction, Employee Support, Energy Efficiency, Resource Efficiency and Tool Support. The relationships are statistically significant, with a significance level of less than 0.01 (p = 0.000). Thus, the hypothesised relationships were all accepted. The contributions of this study revolve around the research perspectives of the measurements to attain a green software product. 相似文献
4.
5.
M.S. AlBuriahi H.H. Hegazy Faisal Alresheedi I.O. Olarinoye H. Algarni H.O. Tekin H.A. Saudi 《Ceramics International》2021,47(5):5951-5958
This research article aims to study the effect of CdO addition on the radiation shielding characteristics of boro-tellurite glasses in the composition of 50B2O3 - (50-x) TeO2- xCdO, where x = 0, 10, 20, 30, 40 and 50 mol%. These glasses were exposed to gamma radiation and the transmitted gamma photons were evaluated for energies varying from 15 keV to 15 MeV using Geant4 simulation toolkit. The number of transmitted photons was then used to characterize the gamma shielding for the studied glasses in terms of linear/mass attenuation coefficients, MFP, Zeff, and HVL. The simulation outcomes were theoretically confirmed by using Phy-X software. The beta (electron) shielding characterization of the involved glasses was also investigated by determining the projectile range and stopping power using ESTAR software. Additionally, the fast neutron shielding characterization of the glasses was achieved by evaluating removal cross-section (ΣR). The results reveal that the CdO has a small influence on the shielding performance of the boro-tellurite glasses against gamma, beta, and neutron radiations. The shielding performance of the boro-tellurite glasses was compared with that of common shielding materials in terms of MFP. It can be concluded that the boro-tellurite glasses regardless of the concentration of CdO content have promising shielding performance to be used for radiation applications. 相似文献
6.
7.
Edge Computing is one of the radically evolving systems through generations as it is able to effectively meet the data saving standards of consumers, providers and the workers. Requisition for Edge Computing based items have been increasing tremendously. Apart from the advantages it holds, there remain lots of objections and restrictions, which hinders it from accomplishing the need of consumers all around the world. Some of the limitations are constraints on computing and hardware, functions and accessibility, remote administration and connectivity. There is also a backlog in security due to its inability to create a trust between devices involved in encryption and decryption. This is because security of data greatly depends upon faster encryption and decryption in order to transfer it. In addition, its devices are considerably exposed to side channel attacks, including Power Analysis attacks that are capable of overturning the process. Constrained space and the ability of it is one of the most challenging tasks. To prevail over from this issue we are proposing a Cryptographic Lightweight Encryption Algorithm with Dimensionality Reduction in Edge Computing. The t-Distributed Stochastic Neighbor Embedding is one of the efficient dimensionality reduction technique that greatly decreases the size of the non-linear data. The three dimensional image data obtained from the system, which are connected with it, are dimensionally reduced, and then lightweight encryption algorithm is employed. Hence, the security backlog can be solved effectively using this method. 相似文献
8.
现有文献针对计及转子变流器(RSC)控制的双馈感应风电机组(DFIG)定子短路电流解析表达,将定子磁链当作一阶直流衰减分量或忽略功率外环控制。基于DFIG电压、磁链和RSC控制方程,得到定子电流关于定子电压和定子功率的传递函数,提出定子电流的精确解析表达式。基于RSC内、外环PI参数关系,推导直流分量衰减时间常数和角频率关于PI参数的表达式。分析了RSC内外环PI参数对定子电流直流衰减分量的影响。仿真结果验证了解析表达式的准确性,为PI参数选取和保护装置测量、整定提供依据。 相似文献
9.
Mohammad Shafiur Rahman Kutaila Al-Farsi Salha Saleh Al-Maskari 《International Journal of Food Properties》2018,21(1):849-856
Variability and sensitivity of a portable electronic nose (32 sensors) was assessed by considering different variables for measurement (i.e., reference, standard, first and second purges, sample draw time, waiting time for the volatiles released in the headspace, and mass of sample or headspace volume of the jar containing sample). In this study, dried date-pits were used a model sample. The highest stability was achieved when both reference and standard (i.e., dried date-pits, no heating treatment) were used before test sample measurement. Higher sample draw time more than 10 s significantly decreased the stability, whereas optimum second purge was observed at 50 s. Optimum time to generate volatile was observed as 24 h. A sample of 100 g increased the signal intensity compared to the 50 g sample for the 60°C and 100°C treated samples, while an opposite trend was observed for the 150°C treated sample. Finally, the responses of volatile components in date-pits heated at different temperatures (60°C, 100°C, and 150°C) were measured using the optimum operating conditions. Principal component analysis explored the relationships between the volatile features and classified date-pits heated at different temperatures. The results showed that an electronic nose was able to classify date-pits based on their volatile components generated by different degrees of heating (93.3% accuracy). 相似文献
10.
基于太赫兹光谱的人参和西洋参鉴别 总被引:1,自引:0,他引:1
为了快速区分人参和西洋参,依据两者所含的人参皂苷在太赫兹波段具有不同指纹光谱,提出了一种基于人参皂苷的太赫兹光谱鉴别人参和西洋参的方法。采用MATLAB软件识别人参和西洋参的太赫兹光谱,同时根据太赫兹光谱特征并通过标准的主成分分析(PCA)区分出人参、西洋参。实验结果表明,基于太赫兹光谱的主成分分析可精确区分出人参、西洋参,并且还可以应用于其他类似物质的区分中。 相似文献