全文获取类型
收费全文 | 7537篇 |
免费 | 535篇 |
国内免费 | 276篇 |
专业分类
电工技术 | 472篇 |
技术理论 | 2篇 |
综合类 | 1291篇 |
化学工业 | 562篇 |
金属工艺 | 241篇 |
机械仪表 | 152篇 |
建筑科学 | 1420篇 |
矿业工程 | 398篇 |
能源动力 | 396篇 |
轻工业 | 227篇 |
水利工程 | 339篇 |
石油天然气 | 330篇 |
武器工业 | 345篇 |
无线电 | 567篇 |
一般工业技术 | 449篇 |
冶金工业 | 529篇 |
原子能技术 | 44篇 |
自动化技术 | 584篇 |
出版年
2024年 | 7篇 |
2023年 | 49篇 |
2022年 | 101篇 |
2021年 | 147篇 |
2020年 | 136篇 |
2019年 | 161篇 |
2018年 | 127篇 |
2017年 | 139篇 |
2016年 | 182篇 |
2015年 | 209篇 |
2014年 | 479篇 |
2013年 | 398篇 |
2012年 | 493篇 |
2011年 | 575篇 |
2010年 | 469篇 |
2009年 | 446篇 |
2008年 | 467篇 |
2007年 | 663篇 |
2006年 | 531篇 |
2005年 | 422篇 |
2004年 | 335篇 |
2003年 | 351篇 |
2002年 | 292篇 |
2001年 | 214篇 |
2000年 | 180篇 |
1999年 | 160篇 |
1998年 | 104篇 |
1997年 | 72篇 |
1996年 | 90篇 |
1995年 | 59篇 |
1994年 | 54篇 |
1993年 | 34篇 |
1992年 | 36篇 |
1991年 | 29篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1966年 | 4篇 |
1965年 | 7篇 |
1963年 | 6篇 |
1960年 | 5篇 |
1959年 | 3篇 |
1958年 | 4篇 |
1955年 | 3篇 |
1954年 | 5篇 |
排序方式: 共有8348条查询结果,搜索用时 150 毫秒
11.
《The Electricity Journal》2020,33(7):106816
Using mean value theorem for integrals we show that the well-known LCOE definition is incorrect. 相似文献
12.
The paper is mainly to explore the automated music composition experiences for the students in the high grades of elementary school who are unfamiliar with the professional music theory. The proposed Automated Composition for Music Education (ACME) software was developed to help the students to compose the rhythm and melody themselves, while chord configuration and arrangement are automatically generated. Subsequently, sixth-year students of a non-experimental school were recruited to use the software for the completion of its development. Analysis of learning effectiveness at the reaction level, analysis of learning-level learning effectiveness, correlation analysis of the reaction- and learning-levels learning effectiveness has been performed with a significant result. The correlations between each component of learning effectiveness at the reaction and learning levels were also found. Finally the students in the experimental group using the ACME teaching materials showed a better learning effectiveness at both reaction level and learning level, than those of the students in the comparison group. 相似文献
13.
In this article, the silver-plated polyamide fabrics (SPPAFs) with high electroconductibility and shielding effectiveness were fabricated by using in situ reduction of polydopamine and chemical silvering. The effects of SPPAFs dopamine (C8H11O2N) and silver nitrate (AgNO3) concentration on surface resistivity and electromagnetic interference shielding effectiveness were studied. The results showed that the surface resistivity of SPPAFs can reach a minimum value of 0.06 ± 0.014 Ω cm−1, when C8H11O2N concentration is 4 g L−1 and the AgNO3 concentration is 120 g L−1. The shielding effectiveness of SPPAFs in the wide frequency range of 10–3000 MHz increases with the increase in the concentration of AgNO3, and increases first and stabilizes afterward with increasing C8H11O2N concentration. When the concentration of C8H11O2N and AgNO3 is 3 and 120 g L−1, respectively, mean shielding effectiveness values in the low-, medium-, and high-frequency bands are 71.3, 73.8, and 76.1 dB, respectively. Moreover, the mean shielding effectiveness values is 83.79 dB in the frequency range of 1.2–2.3 GHz. The dominant shielding mechanism of SPPAFs is the reflected electromagnetic waves and the absorption shielding effectiveness is less than 2 dB. The average electromagnetic shielding values of SPPAFs are above 67 dB after 16 weeks of storage, when C8H11O2N concentration is 4 g L−1 and the AgNO3 concentration is 80 and 100 g L−1. The prepared SPPAFs show promising applications in military textiles and smart wearable clothing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48227. 相似文献
14.
Cryptocurrencies have brought many innovations and discussions to economic life. Digital assets, which are very popular by investors, are frequently used for many purposes such as store of value, exchange, and speculation. It creates a research area that intentions cryptocurrency experts prioritize in crypto investments. In this paper, therefore, the fuzzy Full Consistency Method-Bonferroni (FUCOM-F’B) model is conducted to determine the priorities of drivers for investing in cryptocurrencies. The selected twenty-three drivers are classified based on five aspects, including functionality, financial, legal infrastructure, technology, and security. Based on the findings, “strong electronic encryption” and “use of digital signature” are the most significant drivers for preferring a cryptocurrency. A validation check is performed to verify the reliability, usefulness, and stability of the proposed approach. Further, the introduced approach allows taking the ambiguities and subjectivity into account which exist in the decision-making procedure. The suggested framework can be a helpful decision support tool for regulators, policymakers, practitioners, and cryptocurrency investors. 相似文献
15.
Kelly Yujie Wang Yuan Wen Tsz Leung Yip Meifeng Luo 《International Transactions in Operational Research》2020,27(5):2658-2682
As nonrecourse project finance (rather than financing on a sovereign basis) is becoming more prevalent worldwide, financing institutions have to collaborate more closely with firms to optimize capacity‐investment and financing decisions. Under this background, this paper presents a stylized Stackelberg games model, taking into account the firm's capacity investment as well as the bank's interest rate and funding ratio decisions. Consortium structures between bank and firm are formalized into five modes based on industry practice, namely, the integrated consortium, pure shareholder funding, bank as leader, full coordination, and bank as follower. The optimality and equilibrium of each of the five modes are analytically derived, and their existence and uniqueness are demonstrated. Valuable economic insights are obtained through both modeling analysis and numerical experiments, with the main findings including the following: (i) a lack of bank financing leads to insufficient capacity investment and poor consortium performance; (ii) interest rate and funding ratio play important but different roles in the bank's risk management; (iii) the bank's proactivity in leading and coordinating the consortium is critical for the two parties’ overall performance; and (iv) if the bank is the follower, the firm's capacity decision is irrelevant to the bank's loan contract, and the consortium cannot be coordinated to the first‐best level of performance. 相似文献
16.
Knowledge transfer offices (KTOs) are required to adopt a comprehensive approach to managing a broad set of channels of university–industry collaboration, including collaborative research, business services, exchange of human resources and informal relations within a regional innovation system. The perspectives of firms and academic researchers, the main stakeholders of KTOs, are useful complements to assess KTO activity. The goal of this article is to study the effectiveness that these stakeholders attribute to KTOs. Based on survey data collected in the Spanish region of Andalusia, the article explores stakeholders’ perceptions and determinants. The results show that the level of engagement in a diversified range of activities and the importance attributed to knowledge transfer in the strategy of both research groups and firms are the best predictors of the perceived effectiveness of KTOs. The article also underlines specific differences between the two types of stakeholders. 相似文献
17.
An increase in the average herd size on Australian dairy farms has also increased the labor and animal management pressure on farmers, thus potentially encouraging the adoption of precision technologies for enhanced management control. A survey was undertaken in 2015 in Australia to identify the relationship between herd size, current precision technology adoption, and perception of the future of precision technologies. Additionally, differences between farmers and service providers in relation to perception of future precision technology adoption were also investigated. Responses from 199 dairy farmers, and 102 service providers, were collected between May and August 2015 via an anonymous Internet-based questionnaire. Of the 199 dairy farmer responses, 10.4% corresponded to farms that had fewer than 150 cows, 37.7% had 151 to 300 cows, 35.5% had 301 to 500 cows; 6.0% had 501 to 700 cows, and 10.4% had more than 701 cows. The results showed that farmers with more than 500 cows adopted between 2 and 5 times more specific precision technologies, such as automatic cup removers, automatic milk plant wash systems, electronic cow identification systems and herd management software, when compared with smaller farms. Only minor differences were detected in perception of the future of precision technologies between either herd size or farmers and service providers. In particular, service providers expected a higher adoption of automatic milking and walk over weighing systems than farmers. Currently, the adoption of precision technology has mostly been of the type that reduces labor needs; however, respondents indicated that by 2025 adoption of data capturing technology for monitoring farm system parameters would be increased. 相似文献
18.
在实物期权理论框架下,基于Black-Schole采矿权评估模型,提出了计量国际环境不确定性的方法以及将其纳入评估模型的途径,以此优化完善海外采矿权评估; 通过一实例验证了本文所述方法的可行性,并依据评估结果进一步分析了投资策略,最后对所提方法的可靠性进行了检验。研究结果显示: ① 采矿权价值来自于矿业权人对矿产资源的开采加工及具有灵活经营的权利,国际环境的不确定变化影响采矿权价值及投资策略。② 矿产品价格升高、价格波动率增加、驻在国矿业行业环境和国家环境变异程度的增加、矿山服务年限的增加,均提高了海外采矿权价值; 但矿产品价格下降、矿山服务年限减少将降低采矿权价值。③ 当矿产品价格持续处于低位时,项目应尽早建设或放弃; 而当价格处于增长或高位时,项目可适当推迟建设。④ 老挝矿业行业环境的变异程度大于该国国家环境的变异程度,前往老挝投资的矿企应重点关注该国涉及矿业投资的法律法规及政策,重点防范行业风险。⑤ 本文所提海外采矿权评估方法是可行、可靠的,具有一定实践意义。 相似文献
19.
阐述了熔模铸造铸件出现砂眼缺陷的特征与出现的部位,分析了砂眼缺陷产生的内、外部原因并提出了相应的对策。结果表明,砂眼是由于型壳内、外部的型砂和/或耐火材料进入型腔形成的,尽量减少影响型壳质量的人为因素,提高型壳质量是防止铸件砂眼最有效的措施。 相似文献
20.
随着生态环境意识的加强和环保治理力度的提升,平板玻璃窑炉烟气氮氧化物治理已经全面落实。而由于平板显示基板玻璃窑炉烟气性质的独特性,其脱硝技术路线的选择也取决于不同地区氮氧化物排放浓度的限值差异。详细介绍了选择性催化还原法(SCR)、选择性非催化还原法(SNCR)和逆向流选择性催化还原法(CSCR)三种脱硝技术并对比了三者之间在脱硝效率、反应温度、初始投资、全生命周期成本的差异。同时,对未来的发展应用进行了展望。 相似文献