全文获取类型
收费全文 | 210652篇 |
免费 | 21518篇 |
国内免费 | 12562篇 |
专业分类
电工技术 | 16483篇 |
技术理论 | 7篇 |
综合类 | 17177篇 |
化学工业 | 30472篇 |
金属工艺 | 12485篇 |
机械仪表 | 14173篇 |
建筑科学 | 17631篇 |
矿业工程 | 6802篇 |
能源动力 | 6423篇 |
轻工业 | 15310篇 |
水利工程 | 4975篇 |
石油天然气 | 11193篇 |
武器工业 | 2331篇 |
无线电 | 25400篇 |
一般工业技术 | 22002篇 |
冶金工业 | 8628篇 |
原子能技术 | 2462篇 |
自动化技术 | 30778篇 |
出版年
2024年 | 1025篇 |
2023年 | 3370篇 |
2022年 | 6636篇 |
2021年 | 9118篇 |
2020年 | 6896篇 |
2019年 | 5440篇 |
2018年 | 6064篇 |
2017年 | 7191篇 |
2016年 | 6244篇 |
2015年 | 9052篇 |
2014年 | 11523篇 |
2013年 | 13644篇 |
2012年 | 15599篇 |
2011年 | 16426篇 |
2010年 | 15105篇 |
2009年 | 14231篇 |
2008年 | 14101篇 |
2007年 | 13356篇 |
2006年 | 12440篇 |
2005年 | 9854篇 |
2004年 | 6931篇 |
2003年 | 6274篇 |
2002年 | 6338篇 |
2001年 | 5567篇 |
2000年 | 4436篇 |
1999年 | 3873篇 |
1998年 | 2575篇 |
1997年 | 2134篇 |
1996年 | 2057篇 |
1995年 | 1692篇 |
1994年 | 1403篇 |
1993年 | 959篇 |
1992年 | 728篇 |
1991年 | 530篇 |
1990年 | 415篇 |
1989年 | 364篇 |
1988年 | 301篇 |
1987年 | 187篇 |
1986年 | 144篇 |
1985年 | 76篇 |
1984年 | 62篇 |
1983年 | 42篇 |
1982年 | 53篇 |
1981年 | 55篇 |
1980年 | 49篇 |
1979年 | 35篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1959年 | 10篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
设计了一种以STM32F103微控制器为控制核心,基于24位高精度模数转换器的钻孔深度测量仪器。利用弹性波回波测距原理,通过测量出钻孔中钻杆的长度,实现钻孔深度的快速、无损、准确的测量,主要用于井下瓦斯抽放钻孔、探放水钻孔等煤矿通防工作的施工验收。仪器小巧轻便,操作简单,单人即可完成测量工作,节约下井的人力物力,提高生产效率,最长测量长度可达250米,误差不超过1米。 相似文献
92.
93.
Multifunctional 3D Patternable Drug‐Embedded Nanocarrier‐Based Interfaces to Enhance Signal Recording and Reduce Neuron Degeneration in Neural Implantation 下载免费PDF全文
94.
针对机车走行部关键部位存在的风险及日常机车运用和检修存在的问题,进行了调查分析并提出预防对策,保证了机车走行部的运行安全。 相似文献
95.
Sumeng Wei Yuling Yang Xiao Feng Shanshan Li Lei Zhou Jingyu Wang Xiaozhi Tang 《International Journal of Food Science & Technology》2020,55(7):2691-2699
Structures and properties of myofibrillar protein gel prepared at different power (300–800 W) were evaluated. Amino acid analysis demonstrated that changes in microwave power did not alter primary structure of gel. However, an increase in microwave power could change higher structures of gel. As microwave power increased, α-helix content decreased and β-sheet content increased. Increased microwave power probably facilitated protein to unfold and expose the internal groups, causing surface hydrophobicity and the formation of disulphide bonds were enhanced, which indicated changes in tertiary and quaternary structures of protein. At 500 W, gel had the best ultrastructure where surface morphology, springiness and water holding capacity reached the optimum. Our findings suggested that microwave at an appropriate power (500 W) could change higher structures of myofibrillar protein gel to achieve desired processing and quality protein gel characteristics. 相似文献
96.
Yanlong Shi Xiaojuan Feng Haiyu Guan Jiahua Zhang Zhongai Hu 《International Journal of Hydrogen Energy》2021,46(12):8557-8566
Constructing high-efficient and nonprecious electrocatalysts is of primary importance for improving the efficiency of water splitting. Herein, a novel sunflower plate-like NiFe2O4/CoNi–S nanosheet heterostructure was fabricated via facile hydrothermal and electrodeposition methods. The as-fabricated NiFe2O4/CoNi–S heterostructure array exhibits remarkable bifunctional catalytic activity and stability toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. It presents a small overpotential of 219 mV and 149 mV for OER and HER, respectively, to produce a current density of 10 mA cm?2. More significantly, when the obtained electrodes are used as both the cathode and anode in an electrolyzer, a voltage of 1.57 V is gained at 10 mA cm?2, with superior stability for 72 h. Such outstanding properties are ascribed to: the 3D porous network structure, which exposes more active sites and accelerates mass transfer and gas bubble emission; the high conductivity of CoNi–S, which provides faster charge transport and thus promotes the electrocatalytic reaction of the composites; and the effective interface engineering between NiFe2O4 (excellent performance for OER) and CoNi–S (high activity for HER), which leads to a shorter transport pathway and thus expedites electron transfer. This work provides a new strategy for designing efficient and inexpensive electrocatalysts for water splitting. 相似文献
97.
Multibody System Dynamics - A recently developed index reduction method is applied to comparatively complicated underactuated mechanical systems in the context of inverse dynamics. The inverse... 相似文献
98.
为降低烟草中噁霉灵检测中的基质干扰,提高检测灵敏度和和稳定性,通过试验建立了以QuEChERS为样品前处理方法、液相色谱串联质谱仪为检测仪器的烟草中噁霉灵残留检测方法。样品加水浸润后,经丙酮提取、盐析试剂包除水、石墨化炭黑除杂后,采用Agilent ZORBAX 300SB-C8液相色谱柱(2.1 mm×100 mm,1.8 μm)分离,甲醇-水程序洗脱,ESI雾化,串联质谱MRM检测。结果发现,该方法在0.0025~0.0500 mg/L范围内线性良好,决定系数r2=0.9996,定量检测限1.06 μg/L,回收率在90.8%~92.0%之间,相对标准偏差为5.1%。运用该方法测定烟草中的噁霉灵,操作简单,检测精度高,满足CORESTA对烟草农残检测的要求。 相似文献
100.
To minimize the mass and increase the bearing failure load of composite doublelap bolted joints, a three-step optimization strategy including feasible region reduction,
optimization model decoupling and optimization was presented. In feasible region
reduction, the dimensions of the feasible design region were reduced by selecting dominant
design variables from numerous multilevel parameters by sensitivity analyses, and the
feasible regions of variables were reduced by influence mechanism analyses. In model
decoupling, the optimization model with a large number of variables was divided into
various sub-models with fewer variables by variance analysis. In the third step, the
optimization sub-models were solved one by one using a genetic algorithm, and the
modified characteristic curve method was adopted as the failure prediction method. Based
on the proposed optimization method, optimization of a double-lap single-bolt joint was
performed using the ANSYS® code. The results show that the bearing failure load increased
by 13.5% and that the mass decreased by 8.7% compared with those of the initial design of
the joint, which validated the effectiveness of the three-step optimization strategy. 相似文献