全文获取类型
收费全文 | 161482篇 |
免费 | 14080篇 |
国内免费 | 7677篇 |
专业分类
电工技术 | 10353篇 |
技术理论 | 11篇 |
综合类 | 12097篇 |
化学工业 | 26938篇 |
金属工艺 | 9572篇 |
机械仪表 | 10459篇 |
建筑科学 | 12533篇 |
矿业工程 | 4801篇 |
能源动力 | 4617篇 |
轻工业 | 11730篇 |
水利工程 | 3247篇 |
石油天然气 | 9352篇 |
武器工业 | 1387篇 |
无线电 | 17842篇 |
一般工业技术 | 18259篇 |
冶金工业 | 7318篇 |
原子能技术 | 1860篇 |
自动化技术 | 20863篇 |
出版年
2024年 | 552篇 |
2023年 | 2297篇 |
2022年 | 4242篇 |
2021年 | 6112篇 |
2020年 | 4616篇 |
2019年 | 3927篇 |
2018年 | 4301篇 |
2017年 | 4929篇 |
2016年 | 4276篇 |
2015年 | 6297篇 |
2014年 | 7781篇 |
2013年 | 9423篇 |
2012年 | 10751篇 |
2011年 | 11508篇 |
2010年 | 10401篇 |
2009年 | 10017篇 |
2008年 | 10018篇 |
2007年 | 9641篇 |
2006年 | 9676篇 |
2005年 | 8264篇 |
2004年 | 5863篇 |
2003年 | 4794篇 |
2002年 | 4470篇 |
2001年 | 4032篇 |
2000年 | 3961篇 |
1999年 | 3850篇 |
1998年 | 3138篇 |
1997年 | 2679篇 |
1996年 | 2426篇 |
1995年 | 2109篇 |
1994年 | 1732篇 |
1993年 | 1200篇 |
1992年 | 983篇 |
1991年 | 748篇 |
1990年 | 545篇 |
1989年 | 493篇 |
1988年 | 388篇 |
1987年 | 261篇 |
1986年 | 165篇 |
1985年 | 89篇 |
1984年 | 59篇 |
1983年 | 41篇 |
1982年 | 65篇 |
1981年 | 43篇 |
1980年 | 35篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1965年 | 3篇 |
1959年 | 10篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Yong Pan Chen Zhu Wen Bin Zeng Pei Fu Chi Chen Bao Ming Xu Zhong Feng Gao 《Chembiochem : a European journal of chemical biology》2021,22(24):3431-3436
Rapid and sensitive point-of-care testing (POCT) is an extremely critical mission in practical applications, especially for rigorous military medicine, home health care, and in the third world. Here, we report a visual POCT method for adenosine triphosphate (ATP) detection based on Taylor rising in the corner of quadratic geometries between two rod surfaces. We discuss the principle of Taylor rising, demonstrating that it is significantly influenced by contact angle, surface tension, and density of the sample, which are controlled by ATP-dependent rolling circle amplification (RCA). In the presence of ATP, RCA reaction effectively suppresses Taylor-rising behavior, due to the increased contact angle, density, and decreased surface tension. Without addition of ATP, untriggered RCA reaction is favorable for Taylor rising, resulting in a significant height. With this proposed method, visual sensitive detection of ATP without the aid of other instruments is realized with only a 5 μL droplet, which has good selectivity and a low detection limit (17 nM). Importantly, this visual method provides a promising POCT tool for user-friendly molecular diagnostics. 相似文献
93.
This paper discusses the compressive performance of perforated brick masonry after fire exposure. Compressive strength tests of the mortar, clay perforated brick, and perforated brick masonry specimens were performed in accordance with ISO834 fire tests of different durations. The temperature distribution of the masonry materials and specimens was simulated using the finite element software ABAQUS, with the thermal parameters of masonry materials recommended by European standard Eurocode 6 and related literature. The compressive strength reduction factors of mortar and clay perforated brick exposed to different fire durations were calculated via the layered method suggested by European standard Eurocode 1. In addition, the compressive strength reduction factors after cooldown were obtained from the experimental data of the masonry materials, and by considering further reductions in the compressive strength after cooling from high temperatures. Experimental data of the masonry specimens were compared with the numerical results obtained using the reduction factors proposed in this work. The comparison revealed an overall acceptable approximation. Thus, the method presented in this paper can be used to evaluate the residual capacity of masonry structures after fire. 相似文献
94.
95.
96.
通过文献计量方法从样本选取、研究动态分析、主题分布三方面对健康人力资本发展现状及热点问题进行总结.研究结果表明,自2004年开始该领域所属学科种类和期刊源日益丰富,并形成合著度较高的核心作者群体,健康人力资本研究成为人力资本领域的研究热点,健康人力资本与经济增长或收入的关系、健康人力资本指标体系的构建和居民健康人力资本收入效应的测算等问题都成为当前和未来的研究重点. 相似文献
97.
98.
Fei Xu Xiangli Shi Qingzhu Zhang Wenxing Wang 《International journal of molecular sciences》2015,16(8):18714-18731
The chlorothiophenoxy radicals (CTPRs) are key intermediate species in the formation of polychlorinated dibenzothiophenes/thianthrenes (PCDT/TAs). In this work, the formation of CTPRs from the complete series reactions of 19 chlorothiophenol (CTP) congeners with H and OH radicals were investigated theoretically by using the density functional theory (DFT) method. The profiles of the potential energy surface were constructed at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level. The rate constants were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) contribution at 600–1200 K. The present study indicates that the structural parameters, thermal data, and rate constants as well as the formation potential of CTPRs from CTPs are strongly dominated by the chlorine substitution at the ortho-position of CTPs. Comparison with the study of formation of chlorophenoxy radicals (CPRs) from chlorophenols (CPs) clearly shows that the thiophenoxyl-hydrogen abstraction from CTPs by H is more efficient than the phenoxyl-hydrogen abstraction from CPs by H, whereas the thiophenoxyl-hydrogen abstraction from CTPs by OH is less impactful than the phenoxyl-hydrogen abstraction from CPs by OH. Reactions of CTPs with H can occur more readily than that of CTPs with OH, which is opposite to the reactivity comparison of CPs with H and OH. 相似文献
99.
100.
This paper considers a novel distributed iterative learning consensus control algorithm based on neural networks for the control of heterogeneous nonlinear multiagent systems. The system's unknown nonlinear function is approximated by suitable neural networks; the approximation error is countered by a robust term in the control. Two types of control algorithms, both of which utilize distributed learning laws, are provided to achieve consensus. In the provided control algorithms, the desired reference is considered to be an unknown factor and then estimated using the associated learning laws. The consensus convergence is proven by the composite energy function method. A numerical simulation is ultimately presented to demonstrate the efficacy of the proposed control schemes. 相似文献