全文获取类型
收费全文 | 288089篇 |
免费 | 22917篇 |
国内免费 | 14840篇 |
专业分类
电工技术 | 20040篇 |
技术理论 | 53篇 |
综合类 | 39209篇 |
化学工业 | 31505篇 |
金属工艺 | 10727篇 |
机械仪表 | 15904篇 |
建筑科学 | 40375篇 |
矿业工程 | 15901篇 |
能源动力 | 8951篇 |
轻工业 | 15930篇 |
水利工程 | 14889篇 |
石油天然气 | 13477篇 |
武器工业 | 2757篇 |
无线电 | 18842篇 |
一般工业技术 | 21252篇 |
冶金工业 | 16728篇 |
原子能技术 | 3227篇 |
自动化技术 | 36079篇 |
出版年
2024年 | 483篇 |
2023年 | 2590篇 |
2022年 | 4970篇 |
2021年 | 6633篇 |
2020年 | 6774篇 |
2019年 | 5595篇 |
2018年 | 5281篇 |
2017年 | 6454篇 |
2016年 | 7882篇 |
2015年 | 8799篇 |
2014年 | 16273篇 |
2013年 | 14907篇 |
2012年 | 19417篇 |
2011年 | 20803篇 |
2010年 | 16406篇 |
2009年 | 17004篇 |
2008年 | 15882篇 |
2007年 | 20679篇 |
2006年 | 19594篇 |
2005年 | 17077篇 |
2004年 | 14496篇 |
2003年 | 13078篇 |
2002年 | 10783篇 |
2001年 | 9130篇 |
2000年 | 7678篇 |
1999年 | 6262篇 |
1998年 | 4765篇 |
1997年 | 4152篇 |
1996年 | 3803篇 |
1995年 | 3244篇 |
1994年 | 2882篇 |
1993年 | 2123篇 |
1992年 | 1873篇 |
1991年 | 1399篇 |
1990年 | 1229篇 |
1989年 | 1088篇 |
1988年 | 883篇 |
1987年 | 583篇 |
1986年 | 430篇 |
1985年 | 372篇 |
1984年 | 353篇 |
1983年 | 247篇 |
1982年 | 228篇 |
1981年 | 177篇 |
1980年 | 140篇 |
1979年 | 114篇 |
1978年 | 62篇 |
1977年 | 78篇 |
1976年 | 56篇 |
1975年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
75.
近年来,我市因雷击而导致搅拌站系统瘫痪停产、影响工程进度的事件时有发生,在针对混凝土搅拌站配料秤的实际检定工作中,也常发现配料秤的称重传感器因雷击损坏而影响计量准确性。因此,对混凝土搅拌站防雷的研究具有重要意义。本文阐述了雷电对混凝土搅拌站的主要危害,分析了混凝土搅拌站常见的雷击原因及其防护措施,旨在引起生产方、安装方以及使用方对混凝土搅拌站防雷的共同重视。 相似文献
76.
77.
Lu Xu Baijun Liu Mingyao Zhang Yang Bai Jinming Zhang Jiayin Song 《Polymer Engineering and Science》2020,60(6):1194-1201
A series of methacrylate-acrylonitrile-butadiene-styrene (MABS) resins was prepared using bulk polymerization. The polarity of the continuous phase and the compatibility of two phases were changed by adjusting the methyl methacrylate (MMA) content, choosing values that were close to styrene-butadiene rubber solubility value. The possibility of controlling the microstructure of the MABS resin by changing the polarity of the components and the compatibility of two phases was assessed. The dynamic mechanical analysis shows that the compatibility of two phases varies with the MMA content. The morphological analysis shows that increasing MMA contents results in a gradual decrease in the sub-inclusion structure with a network skeleton of rubber particles, and that all the particles become solid rubber when the MMA content reaches 75%. The sub-inclusion structure reappears but does not have a network skeleton when the MMA content is 90%. The impact strength and morphological analysis indicate that the solid rubber particles and the sub-inclusion structure with a network skeleton provide excellent toughness, while the sub-inclusion structure without a network skeleton does not. In contrast, the transmittance of the ABS resin first increased and then decreased with increasing MMA content. 相似文献
78.
2002年12月国务院批复了《南水北调工程总体规划》,明确中线工程分两期建设。目前,一期工程已经通水。近年来,随着社会经济的快速发展,受水区的人口、生产规模、节水水平、人们对环境的要求都发生了变化,因此有必要根据新的情况对受水区的用水需求重新预测。分析了城市化发展和城镇用水变化的新形势,依据流域、区域水资源规划成果,提出了中线二期工程受水区需调水量,并与《南水北调中线工程规划》提出的二期需调水量进行对比,以供各方参考。 相似文献
79.
Dr. Tomasz Ratajczyk Prof. Dr. Gerd Buntkowsky Dr. Torsten Gutmann Dr. Bartłomiej Fedorczyk Dr. Adam Mames Dr. Mariusz Pietrzak Zuzanna Puzio Piotr Grzegorz Szkudlarek 《Chembiochem : a European journal of chemical biology》2021,22(5):855-860
The biorelevant PyFALGEA oligopeptide ligand, which is selective towards the epidermal growth factor receptor (EGFR), has been successfully employed as a substrate in magnetic resonance signal amplification by reversible exchange (SABRE) experiments. It is demonstrated that PyFALGEA and the iridium catalyst IMes form a PyFALGEA:IMes molecular complex. The interaction between PyFALGEA:IMes and H2 results in a ternary SABRE complex. Selective 1D EXSY experiments reveal that this complex is labile, which is an essential condition for successful hyperpolarization by SABRE. Polarization transfer from parahydrogen to PyFALGEA is observed leading to significant enhancement of the 1H NMR signals of PyFALGEA. Different iridium catalysts and peptides are inspected to discuss the influence of their molecular structures on the efficiency of hyperpolarization. It is observed that PyFALGEA oligopeptide hyperpolarization is more efficient when an iridium catalyst with a sterically less demanding NHC ligand system such as IMesBn is employed. Experiments with shorter analogues of PyFALGEA, that is, PyLGEA and PyEA, show that the bulky phenylalanine from the PyFALGEA oligopeptide causes steric hindrance in the SABRE complex, which hampers hyperpolarization with IMes. Finally, a single-scan 1H NMR SABRE experiment of PyFALGEA with IMesBn revealed a unique pattern of NMR lines in the hydride region, which can be treated as a fingerprint of this important oligopeptide. 相似文献
80.
Reliability based criteria are quite popular for optimal sensor network design. We present a modified definition of system reliability for sensor network design for two applications: reliable estimation of variables in a steady state linear flow process, and reliable fault detection and diagnosis for any process. Unlike the weakest-link based definition of system reliability in the literature, the proposed definition considers the entire system and is consistent with the reliability concept used in classical reliability literature. For each application, dual approaches for defining system reliability are proposed, and their analogy with the reliability problem in the classical reliability literature is established. Using examples and stochastic simulations, the advantage of using the proposed system reliability in contrast to the existing definition is illustrated. Part II of this series of articles presents methods for efficient generation of the system reliability function and its use in optimization-based approaches for designing optimal sensor networks. 相似文献