全文获取类型
收费全文 | 222599篇 |
免费 | 20266篇 |
国内免费 | 9540篇 |
专业分类
电工技术 | 14142篇 |
技术理论 | 30篇 |
综合类 | 22688篇 |
化学工业 | 27082篇 |
金属工艺 | 9691篇 |
机械仪表 | 12075篇 |
建筑科学 | 31242篇 |
矿业工程 | 12712篇 |
能源动力 | 8277篇 |
轻工业 | 16200篇 |
水利工程 | 10612篇 |
石油天然气 | 11968篇 |
武器工业 | 3227篇 |
无线电 | 14530篇 |
一般工业技术 | 16428篇 |
冶金工业 | 11474篇 |
原子能技术 | 1684篇 |
自动化技术 | 28343篇 |
出版年
2024年 | 422篇 |
2023年 | 2753篇 |
2022年 | 5059篇 |
2021年 | 7231篇 |
2020年 | 6963篇 |
2019年 | 5202篇 |
2018年 | 4899篇 |
2017年 | 6126篇 |
2016年 | 7731篇 |
2015年 | 8391篇 |
2014年 | 15318篇 |
2013年 | 13445篇 |
2012年 | 16150篇 |
2011年 | 17977篇 |
2010年 | 13240篇 |
2009年 | 13381篇 |
2008年 | 12307篇 |
2007年 | 14953篇 |
2006年 | 13616篇 |
2005年 | 11949篇 |
2004年 | 9936篇 |
2003年 | 8646篇 |
2002年 | 7071篇 |
2001年 | 5838篇 |
2000年 | 4879篇 |
1999年 | 3856篇 |
1998年 | 2743篇 |
1997年 | 2352篇 |
1996年 | 1950篇 |
1995年 | 1668篇 |
1994年 | 1403篇 |
1993年 | 999篇 |
1992年 | 793篇 |
1991年 | 572篇 |
1990年 | 494篇 |
1989年 | 461篇 |
1988年 | 246篇 |
1987年 | 192篇 |
1986年 | 171篇 |
1985年 | 198篇 |
1984年 | 152篇 |
1983年 | 126篇 |
1982年 | 69篇 |
1981年 | 94篇 |
1980年 | 88篇 |
1979年 | 41篇 |
1978年 | 23篇 |
1977年 | 24篇 |
1975年 | 19篇 |
1959年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The symmetrical and asymmetrical electrodes made of Mg were studied in 0.1-M NaCl electrolyte adjusted at pH 12. The statistical and wavelet methods were employed for analyzing the electrochemical current noise (ECN) signals. The asymmetric configuration was used for electrochemical detection of filiform corrosion on Mg electrode. The real time scale of the dominant transients of the asymmetric electrodes was detected on the basis of the maximum peak in the SDPS plots. The SDPS values of the real time scale crystals of the ECN signals resulting from asymmetrical electrodes increased with the increase in immersion time due to the onset of filiform corrosion. 相似文献
102.
We propose a general framework to study the relationship between the price of a painting and its color‐related attributes. To this end we focus on four key aspects: dominant colors, features of the color palette, color harmony, and color emotions. We demonstrate the usefulness of this approach with an example based on Mark Rothko's post‐1950 paintings (the “rectangular” series), and auction data from the 1994 to 2018 period. We identify two distinct price‐color regimes in Rothko's market: (a) [1994‐2005], a period in which prices are explained mainly by the growing popularity of the artist regardless of the color attributes of the paintings sold; and (b) [2006‐2018], a period in which color‐related attributes explain most of the prices. Furthermore, we find that in this second period, the dominant colors and the diversity of the color palette, are by far the most relevant attributes that influence the price; color harmony and color emotions hold almost no explanatory power during this period. Finally, we propose a new metric based on the Herfindahl Index to describe color diversity; this metric seems to be promising at characterizing the effect of the color palette on the price of a painting. 相似文献
103.
目的 从秩序与非秩序理论出发,研究文创产品卡通形象的设计方法.方法 对秩序与非秩序理论的视觉机制和创制理论进行梳理,结合实例,阐述了其与文创产品卡通形象设计之间的联系,分析文创产品卡通形象中的秩序与非秩序的表现形式,提出基于秩序与非秩序理论文创产品卡通形象设计的主要原则,归纳出一套基于秩序与非秩序理论的文创产品卡通形象设计流程与方法,指导设计实践,并验证这些理论方法在设计实践中有效性与可行性.结论 通过对秩序与非秩序理论的研究,文创产品卡通形象设计时应注意提高辨识度、亲和力和便于衍生设计的原则.探索基于秩序与非秩序理论的设计流程与方法,按照界定主题、主体形象设计、主体形象拓展、衍生品应用四个环节开展整体方案设计,为文创产品卡通形象设计提供新的思路与方法. 相似文献
104.
Lightweight ciphers are increasingly employed in cryptography because of the high demand for secure data transmission in wireless sensor network, embedded devices, and Internet of Things. The PRESENT algorithm as an ultra-lightweight block cipher provides better solution for secure hardware cryptography with low power consumption and minimum resource. This study generates the key using key rotation and substitution method, which contains key rotation, key switching, and binary-coded decimal-based key generation used in image encryption. The key rotation and substitution-based PRESENT architecture is proposed to increase security level for data stream and randomness in cipher through providing high resistance to attacks. Lookup table is used to design the key scheduling module, thus reducing the area of architecture. Field-programmable gate array (FPGA) performances are evaluated for the proposed and conventional methods. In Virtex 6 device, the proposed key rotation and substitution PRESENT architecture occupied 72 lookup tables, 65 flip flops, and 35 slices which are comparably less to the existing architecture. 相似文献
105.
油品具有两个基本的物理特性,第一个是挥发性,第二个是易燃性。这些物理特性使得油品在运输过程中的能耗现象非常常见,有时候还会引发安全事故。为了让油品在运输过程里面的能耗得到更加有效的控制,就应该对油品消耗管理体系加以改进,使能源能耗控制管理模式的层次不断提升。此外还要对水电气能源进行多层次管理,从而提升企业整体效益并实现节约能源的目标。本文主要对油品运输中优品损耗的精细化管理措施加以研究。 相似文献
106.
The mitogen-activated protein kinase (MAPK) cascades have been validated playing critical roles in diverse aspects of plant biology, from growth and developmental regulation, biotic and abiotic stress responses, to phytohormone signal transduction or responses. A classical MAPK cascade consists of a MAPK kinase kinase (MAPKKK), a MAPK kinase (MAPKK), and a MAPK. From the 75 MAPKKKs, eight MAPKKs, and 15 MAPKs of rice, a number of them have been functionally deciphered. Here, we update recent advances in knowledge of the roles of rice MAPK cascades, including their components and complicated action modes, their diversified functions controlling rice growth and developmental responses, coordinating resistance to biotic and abiotic stress, and conducting phytohormone signal transduction. Moreover, we summarize several complete MAPK cascades that harbor OsMAPKKK-OsMAPKK-OsMAPK, their interaction with different upstream components and their phosphorylation of diverse downstream substrates to fulfill their multiple roles. Furthermore, we state a comparison of networks of rice MAPK cascades from signal transduction crosstalk to the precise selection of downstream substrates. Additionally, we discuss putative concerns for elucidating the underlying molecular mechanisms and molecular functions of rice MAPK cascades in the future. 相似文献
107.
Hiromi Eba Yuki Masuzoe Toru Sugihara Hayao Yagi Tian Liu 《International Journal of Hydrogen Energy》2021,46(18):10642-10652
Ammonia generation was studied in the reaction between water and nitrogen-containing iron at 323 K and atmospheric pressure. Similar to metallic Fe, the interstitial compound Fe3N reduced water through Fe oxidation to produce hydrogen gas, while the N combined with atomic hydrogen to produce ammonia as a byproduct. The addition of carbon dioxide to this system accelerated the reaction with concomitant consumption of carbon dioxide. The promoted ammonia production upon addition of carbon dioxide can be attributed to the generation of atomic hydrogen from the redox reaction of carbonic acid and Fe, as well as removal of used Fe from the reaction system through the formation of a soluble carbonato complex. When carbonate was added to the reaction system, the production rates of ammonia and hydrogen increased further. The results here confirmed that ammonia can be synthesized from iron nitride under mild conditions by utilizing carbon dioxide. 相似文献
108.
文章将重点阐述消防监督检查中对火灾隐患的认定,并从实际角度出发,充分的考虑可能存在的问题,具体问题具体分析,制定相应的解决对策,以保证消防监督检查工作能够顺利的开展. 相似文献
109.
根据水泥烧成热耗的组成,降低高温设备表面散热是降低水泥烧成热耗的重要途径之一,而减少高温窑炉墙壁的热传导可有效降低设备的表面散热。本文在介绍无机内保温涂层隔热原理的基础上,对保温涂层的应用效果进行了对比研究,通过在传统耐火隔热材料的基础上增加新型无机内保温涂层,可有效降低高温设备外表面温度,减少水泥生产中的散热损失,达到节能降耗的目的。 相似文献
110.
Ionela-Dorina Dumbrava Calin-Cristian Cormos 《International Journal of Hydrogen Energy》2021,46(45):23149-23163
Hydrogen production by biogas conversion represent a promising solution for reduction of fossil CO2 emissions. In this work, a detailed techno-economic analysis was performed for decarbonized hydrogen production based on biogas conversion using calcium and chemical looping cycles. All evaluated concepts generate 100,000 Nm3/h high purity hydrogen. As reference cases, the biogas steam reforming design without decarbonization and with CO2 capture by gas-liquid chemical absorption were also considered. The results show that iron-based chemical looping design has higher energy efficiency compared with the gas-liquid absorption case by 2.3 net percentage points as well as a superior carbon capture rate (99% vs. 65%). The calcium looping case shows a lower efficiency than chemical scrubbing, with about 2.5 net percentage points, but the carbon capture rate is higher (95% vs. 65%). The hydrogen production cost increases with decarbonization, the calcium looping shows the most favourable situation (37.14 €/MWh) compared to the non-capture steam reforming case (33 €/MWh) and MDEA and iron looping cases (about 42 €/MWh). The calcium looping case has the lowest CO2 avoidance cost (10 €/t) followed by iron looping (20 €/t) and MDEA (31 €/t) cases. 相似文献