全文获取类型
收费全文 | 6167篇 |
免费 | 694篇 |
国内免费 | 324篇 |
专业分类
电工技术 | 348篇 |
综合类 | 456篇 |
化学工业 | 1117篇 |
金属工艺 | 301篇 |
机械仪表 | 277篇 |
建筑科学 | 476篇 |
矿业工程 | 188篇 |
能源动力 | 178篇 |
轻工业 | 647篇 |
水利工程 | 138篇 |
石油天然气 | 295篇 |
武器工业 | 50篇 |
无线电 | 766篇 |
一般工业技术 | 814篇 |
冶金工业 | 243篇 |
原子能技术 | 50篇 |
自动化技术 | 841篇 |
出版年
2024年 | 30篇 |
2023年 | 149篇 |
2022年 | 280篇 |
2021年 | 415篇 |
2020年 | 301篇 |
2019年 | 255篇 |
2018年 | 282篇 |
2017年 | 330篇 |
2016年 | 260篇 |
2015年 | 307篇 |
2014年 | 322篇 |
2013年 | 456篇 |
2012年 | 424篇 |
2011年 | 398篇 |
2010年 | 326篇 |
2009年 | 303篇 |
2008年 | 331篇 |
2007年 | 239篇 |
2006年 | 218篇 |
2005年 | 185篇 |
2004年 | 148篇 |
2003年 | 188篇 |
2002年 | 242篇 |
2001年 | 221篇 |
2000年 | 120篇 |
1999年 | 85篇 |
1998年 | 56篇 |
1997年 | 53篇 |
1996年 | 49篇 |
1995年 | 45篇 |
1994年 | 30篇 |
1993年 | 30篇 |
1992年 | 18篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有7185条查询结果,搜索用时 0 毫秒
11.
12.
Platinum catalyst for CO oxidation has been studied for decades,due to its high activity and good stability.In this work,we prepared three different lantha num oxide or hydroxide supports(LaOx(OH)y),and deposited platinum(Pt) with 0.5 at% via an impregnation approach to synthesize Pt/LaOx(OH)y catalysts.However,we find that these catalysts perform a poor stability for the CO oxidation reaction.The fresh and used samples were comprehensively characterized by multiple techniques including power X-ray diffraction(XRD),X-ray absorption fine structure(XAFS),transmission electron microscopy(TEM),temperature-programmed reduction by carbon monoxide(CO-TPR) and thermogravimetric analysis(TGA),to demonstrate that the oxidized platinum atoms or clusters,without any component of Pt-Pt metallic bond,are highly dispersed on the surface of LaOx(OH)y.Furthermore,the as-formed lanthanum carbonate(La2O2CO3) during the exposure to ambient circumstances or in the reaction atmosphere of CO+O2,severely impair the reactivity of Pt/LaOx(OH)y.On the basis of the obtained experimental results,we have drawn a conclusion that the oxidized PtOx atoms or PtxOy clusters are the active species for CO oxidation,while the formation of lanthanum carbonate is the origin of deactivation on reactivity. 相似文献
13.
Zedong Zhao Minqiang Sun Tianqi Wu Jiajia Zhang Peng Wang Long Zhang Chongyang Yang Chengxin Peng Hongbin Lu 《纳微快报(英文)》2021,(8):40-55
Lithium- and manganese-rich (LMR) layered cath-ode materials hold the great promise in designing the next-genera-tion high energy density lithium ion batteries.... 相似文献
14.
目的 了解我国居民栀子食用情况,评估我国栀子食用人群栀子苷暴露水平及健康风险。方法 通过文献检索和专项监测收集我国栀子中栀子苷含量数据,结合2019—2022年我国食药物质消费量调查数据,采用简单分布方法和概率评估方法获得我国不同人群通过食用栀子的栀子苷暴露水平及健康风险。结果 我国9省栀子食用率为10.32%,每日食用量均值为0.36 g,高消费人群每日栀子食用量为1.48 g。简单分布评估显示,9省栀子食用人群的栀子苷每日平均暴露量为0.29 mg/kg·BW,高消费人群(P95)栀子苷暴露量为1.28 mg/kg·BW,9省栀子食用人群中有17.20%的居民通过食用栀子的栀子苷暴露量超过其每日可耐受摄入量(TDI,0.386 mg/kg·BW)。河南省食用人群每日平均暴露量最高,为0.54 mg/kg·BW。概率评估结果显示,我国14.70%的栀子食用人群栀子苷暴露量超过TDI,具有潜在健康风险。结论 我国栀子食用人群的栀子苷暴露风险总体较低,但部分高消费人群(P95)存在健康风险。 相似文献
15.
Yuanjie Li Jincheng Dai Zhongwei Si Kai Niu Chao Dong Jiaru Lin Sen Wang Yifei Yuan 《中国通信》2022,(3):70-87
Unsourced multiple access(UMA) is a multi-access technology for massive, low-power, uncoordinated, and unsourced Machine Type Communication(MTC) networks. It ensures transmission reliability under the premise of high energy efficiency.Based on the analysis of the 6G MTC key performance indicators(KPIs) and scenario characteristics,this paper summarizes its requirements for radio access networks. Following this, the existing multiple access models are analyzed under these standards to determine U... 相似文献
16.
双频激光干涉仪作为常用的精密光学非接触式测量设备,具有精度高、抗干扰能力强、灵活性好等优点。然而环境温度变化、机械振动等因素可能会影响其测量结果的准确性,并且影响程度会随着测量光程的增加而增大。针对基于双频激光干涉仪的大行程位移台测距系统,首先研究了位移台测距系统的测量原理,然后针对系统存在的各项误差进行了分析和补偿,最后,对系统进行综合误差补偿实验,短时间补偿量达到10-8 m量级,且时间越长补偿效果越好。该方法较现有的误差补偿方法更为完整,补偿量更大。 相似文献
17.
18.
Qiu-Ni Zhao Ya-Jie Zhang Zai-Hua Duan Si Wang Can Liu Ya-Dong Jiang Hui-Ling Tai 《稀有金属(英文版)》2021,(6):1459-1476
Ti3C2Tx,which is a novel two-dimensional (2D)material,has received enormous interest in the field of sensor technology due to its large surface area,excellent e... 相似文献
19.
Peng Liu Xinyue Wang Qian Yang Xiaolin Yan Yu Fan Si Zhang Yi Wei Min Huang Lingyan Jiang Lu Feng 《International journal of molecular sciences》2022,23(12)
Escherichia coli K1 is a leading cause of neonatal bacterial meningitis. Recruitment of neutrophils to the central nervous system (CNS) via local immune response plays a critical role in defense against E. coli K1 infection; however, the mechanism underlying this recruitment remains unclear. In this study, we report that microglia and astrocytes are activated in response to stimulation by E. coli K1 and/or E. coli K1-derived outer membrane vesicles (OMVs) and work collaboratively to drive neutrophil recruitment to the CNS. Microglial activation results in the release of the pro-inflammatory cytokine TNF-α, which activates astrocytes, resulting in the production of CXCL1, a chemokine critical for recruiting neutrophils. Mice lacking either microglia or TNF-α exhibit impaired production of CXCL1, impaired neutrophil recruitment, and an increased CNS bacterial burden. C-X-C chemokine receptor 2 (CXCR2)-expressing neutrophils primarily respond to CXCL1 released by astrocytes. This study provides further insights into how immune responses drive neutrophil recruitment to the brain to combat E. coli K1 infection. In addition, we show that direct recognition of E. coli K1 by microglia is prevented by the K1 capsule. This study also reveals that OMVs are sufficient to induce microglial activation. 相似文献
20.
The formation and distribution of dioxin-like polychlorinated biphenyls (dl-PCBs) during cooking was investigated. Concentrations of dl-PCBs in liquid residues, cooked beef, and oil fumes generated during heating were determined by isotope dilution HRGC/HRMS. Although the levels of dl-PCBs in well-done beef were lower compared with those of raw beef, relatively high concentrations of dl-PCBs were detected in the oil fumes produced during heating. This suggests that dl-PCBs in raw beef may have volatilized into the oil fumes during the cooking process. Sucralose and chloropropanols contained in raw materials may have resulted in increased dl-PCB concentrations and the level of toxic equivalents (TEQ) in the oil fumes produced under high temperature during cooking. Concentrations of dl-PCBs did not vary greatly in cooked beef, except when higher levels of chloropropanols were presented in the uncooked raw materials. Results indicate that sucralose and chloropropanols may promote the formation of dl-PCBs during the cooking process. The newly produced dl-PCBs from raw beef cooking were mainly present in oil fumes, which gave rise to high levels of TEQ in oil fumes. 相似文献