首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   64514篇
  免费   8598篇
  国内免费   4002篇
电工技术   5887篇
技术理论   5篇
综合类   5273篇
化学工业   8985篇
金属工艺   3778篇
机械仪表   4618篇
建筑科学   5421篇
矿业工程   2395篇
能源动力   1954篇
轻工业   4829篇
水利工程   1621篇
石油天然气   3195篇
武器工业   993篇
无线电   8046篇
一般工业技术   6242篇
冶金工业   2700篇
原子能技术   977篇
自动化技术   10195篇
  2025年   7篇
  2024年   1222篇
  2023年   1403篇
  2022年   2559篇
  2021年   3477篇
  2020年   2544篇
  2019年   1892篇
  2018年   2097篇
  2017年   2347篇
  2016年   2122篇
  2015年   3105篇
  2014年   3738篇
  2013年   4354篇
  2012年   5206篇
  2011年   5386篇
  2010年   4865篇
  2009年   4657篇
  2008年   4523篇
  2007年   4028篇
  2006年   3772篇
  2005年   3186篇
  2004年   2095篇
  2003年   1391篇
  2002年   1312篇
  2001年   1124篇
  2000年   1030篇
  1999年   840篇
  1998年   488篇
  1997年   444篇
  1996年   413篇
  1995年   364篇
  1994年   244篇
  1993年   198篇
  1992年   178篇
  1991年   105篇
  1990年   93篇
  1989年   62篇
  1988年   56篇
  1987年   37篇
  1986年   36篇
  1985年   14篇
  1984年   11篇
  1983年   9篇
  1982年   14篇
  1981年   14篇
  1980年   16篇
  1979年   4篇
  1978年   4篇
  1959年   9篇
  1951年   5篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Cadmium (Cd) is a potential pathogenic factor in the urinary system that is associated with various kidney diseases. Microplastics (MPs), comprising of plastic particles less than 5 mm in diameter, are a major carrier of contaminants. We applied 10 mg/L particle 5 μm MPs and 50 mg/L CdCl2 in water for three months in vivo assay to assess the damaging effects of MPs and Cd exposure on the kidney. In vivo tests showed that MPs exacerbated Cd-induced kidney injury. In addition, the involvement of oxidative stress, autophagy, apoptosis, and fibrosis in the damaging effects of MPs and Cd on mouse kidneys were investigated. The results showed that MPs aggravated Cd-induced kidney injury by enhancing oxidative stress, autophagy, apoptosis, and fibrosis. These findings provide new insights into the toxic effects of MPs on the mouse kidney.  相似文献   
62.
The relationship between Parkinson’s disease (PD), the second-most common neurodegenerative disease after Alzheimer’s disease, and palmitoylation, a post-translational lipid modification, is not well understood. In this study, to better understand the role of protein palmitoylation in PD and the pathways altered in this disease, we analyzed the differential palmitoyl proteome (palmitome) in the cerebral cortex of PD patients compared to controls (n = 4 per group). Data-mining of the cortical palmitome from PD patients and controls allowed us to: (i) detect a set of 150 proteins with altered palmitoylation in PD subjects in comparison with controls; (ii) describe the biological pathways and targets predicted to be altered by these palmitoylation changes; and (iii) depict the overlap between the differential palmitome identified in our study with protein interactomes of the PD-linked proteins α-synuclein, LRRK2, DJ-1, PINK1, GBA and UCHL1. In summary, we partially characterized the altered palmitome in the cortex of PD patients, which is predicted to impact cytoskeleton, mitochondrial and fibrinogen functions, as well as cell survival. Our study suggests that protein palmitoylation could have a role in the pathophysiology of PD, and that comprehensive palmitoyl-proteomics offers a powerful approach for elucidating novel cellular pathways modulated in this neurodegenerative disease.  相似文献   
63.
Herein, a novel approach used to enhance the conversion of electrochemical CO2 reduction (CO2R), as well as the capacity to produce C2 products, is reported. A copper oxide catalyst supported by graphite phase carbon nitride (CuO/g-C3N4) was prepared using a one-step hydrothermal method and exhibited a better performance than pure copper oxide nanosheets (CuO NSs) and spherical copper oxide particles (CuO SPs). The Faradaic efficiency reached 64.7% for all the C2 products, specifically 37.0% for C2H4, with a good durability at −1.0 V vs. RHE. The results suggest that the interaction between CuO and the two-dimensional g-C3N4 planes promoted CO2 adsorption, its activation and C-C coupling. This work offers a practical method that can be used to enhance the activity of electrochemical CO2R and the selectivity of C2 products through synergistic effects.  相似文献   
64.
Imidazolium-based ionic liquids are wildly used in natural product adsorption and purification. In this work, one typical polymeric ionic liquid (PIL) was synthesized by using L-proline as the anion, which exhibited excellent adsorption capacity toward tea polyphenol epigallocatechin gallate (EGCG). The adsorption conditions were optimized with the response surface method (RSM). Under the optimum conditions, the adsorption capacity of the PIL for EGCG can reach as high as 552 mg/g. Dynamics and isothermal research shows that the adsorption process of EGCG by the PIL particularly meets the quasi-second-order kinetic equation and monolayer adsorption mechanism. According to thermodynamic parameter analysis, the adsorption process is endothermic and spontaneous. The results of theoretical calculation by molecular docking also demonstrated the interaction mechanisms between EGCG and the ionic liquid. Considering the wide application of imidazolium-based ionic liquids in component adsorption and purification, the present study can not only be extended to other similar experimental mechanism validation, but also be representative for guiding the synthesis of PIL and optimization of adsorption conditions.  相似文献   
65.
66.
The development of tissue clearing technologies allows 3D imaging of whole tissues and organs, especially in studies of the central nervous system innervated throughout the body. Although the three-dimensional imaging of solvent-cleared organs (3DISCO) method provides a powerful clearing capacity and high transparency, the rapid quenching of endogenous fluorescence and peroxide removal process decreases its practicability. This study provides a modified method named tDISCO to solve these limitations. The tDISCO protocol can preserve AAV-transduced endogenous EGFP fluorescence for months and achieve high transparency in a fast and simple clearing process. In addition to the brain, tDISCO was applied to other organs and even hard bone tissue. tDISCO also enabled us to visualize the long projection neurons and axons with high resolution. This method provides a fast and simple clearing protocol for 3D visualization of the AAV- transduced long projection neurons throughout the brain and spinal cord.  相似文献   
67.
68.
To reveal the mechanisms underlying root adaptation to drought stress, we isolated and characterized an Arabidopsis mutant, dig5 (drought inhibition of lateral root growth 5), which exhibited increased sensitivity to the phytohormone abscisic acid (ABA) for the inhibition of lateral root growth. The dig5 mutant also had fewer lateral roots under normal conditions and the aerial parts were yellowish with a lower level of chlorophylls. The mutant seedlings also displayed phenotypes indicative of impaired auxin transport, such as abnormal root curling, leaf venation defects, absence of apical hook formation, and reduced hypocotyl elongation in darkness. Auxin transport assays with [3H]-labeled indole acetic acid (IAA) confirmed that dig5 roots were impaired in polar auxin transport. Map-based cloning and complementation assays indicated that the DIG5 locus encodes a chloroplast-localized tRNA adenosine deaminase arginine (TADA) that is involved in chloroplast protein translation. The levels of flavonoids, which are naturally occurring auxin transport inhibitors in plants, were significantly higher in dig5 roots than in the wild type roots. Further investigation showed that flavonoid biosynthetic genes were upregulated in dig5. Introduction of the flavonoid biosynthetic mutation transparent testa 4 (tt4) into dig5 restored the lateral root growth of dig5. Our study uncovers an important role of DIG5/TADA in retrogradely controlling flavonoid biosynthesis and lateral root development. We suggest that the DIG5-related signaling pathways, triggered likely by drought-induced chlorophyll breakdown and leaf senescence, may potentially help the plants to adapt to drought stress through optimizing the root system architecture.  相似文献   
69.
为了定量研究降雨时分流制雨水管网滞留污染物占总污染物的比例,对某研究区域雨水管网中的滞留污染物定期取样检测,并根据研究区域的基础数据建立SWMM模型。同时,提出了一种雨水管网滞留污染物的计算方法,即以检测到的雨水管网污染物浓度及充满度计算滞留污染物质量。将滞留污染物数据输入SWMM模型中,分析对比有无滞留污染物的管网排放口污染物浓度的变化情况。模拟结果表明,在1年一遇的降雨条件下,雨水系统内的滞留污染物对COD、NH3-N、TP总污染负荷的贡献率分别为43. 30%、92. 75%、58. 83%,雨水管网滞留污染物占雨水管网总污染物的比例较大。  相似文献   
70.
流量装置中换向器检定方法的研究   总被引:2,自引:0,他引:2  
孟涛  王池  陈晓铭 《计量学报》2008,29(5):420-422
换向器是液体流量装置的重要组成部分及不确定度来源.双流量计法是一种新的换向器检定方法,使用两台串联流量计对换向器进行检定.通过实验示例,叙述了该方法的试验方法、数据处理及不确定度分析.该方法克服了传统方法检定换向器存在的一些问题,减少了由于流量计自身波动对测量结果所造成的影响,提高了测量结果的可靠性.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号