全文获取类型
收费全文 | 6908篇 |
免费 | 340篇 |
国内免费 | 169篇 |
专业分类
电工技术 | 694篇 |
综合类 | 358篇 |
化学工业 | 528篇 |
金属工艺 | 381篇 |
机械仪表 | 626篇 |
建筑科学 | 206篇 |
矿业工程 | 120篇 |
能源动力 | 134篇 |
轻工业 | 236篇 |
水利工程 | 21篇 |
石油天然气 | 77篇 |
武器工业 | 75篇 |
无线电 | 1196篇 |
一般工业技术 | 620篇 |
冶金工业 | 198篇 |
原子能技术 | 258篇 |
自动化技术 | 1689篇 |
出版年
2024年 | 9篇 |
2023年 | 32篇 |
2022年 | 79篇 |
2021年 | 96篇 |
2020年 | 91篇 |
2019年 | 65篇 |
2018年 | 64篇 |
2017年 | 145篇 |
2016年 | 172篇 |
2015年 | 243篇 |
2014年 | 444篇 |
2013年 | 380篇 |
2012年 | 484篇 |
2011年 | 731篇 |
2010年 | 609篇 |
2009年 | 702篇 |
2008年 | 538篇 |
2007年 | 496篇 |
2006年 | 479篇 |
2005年 | 365篇 |
2004年 | 226篇 |
2003年 | 202篇 |
2002年 | 153篇 |
2001年 | 125篇 |
2000年 | 86篇 |
1999年 | 82篇 |
1998年 | 53篇 |
1997年 | 41篇 |
1996年 | 43篇 |
1995年 | 32篇 |
1994年 | 25篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1974年 | 3篇 |
1968年 | 2篇 |
1960年 | 2篇 |
1958年 | 3篇 |
1957年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有7417条查询结果,搜索用时 15 毫秒
51.
张彭程 《计算机光盘软件与应用》2012,(2):72+78
本论文介绍了以TMS320F2812为核心的智能变送器的硬件及软件设计,从测试以及通信功能两个方面介绍了智能变送器的实验方案。 相似文献
52.
Synthesis and electrochemical properties of Al-doped LiVPO4F cathode materials for lithium-ion batteries 总被引:1,自引:0,他引:1
ZHONG Shengkui YIN Zhoulan WANG Zhixing CHEN Qiyuan 《稀有金属(英文版)》2007,26(5):445-449
Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction (CTR) process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction (XRD),scanning electron microscopy (SEM),and electrochemical measurements. XRD studies show that the Al-doped LiVPO4F has the same triclinic structure (space group p-↑1 ) as the undoped LiVPO4F. The SEM images exhibit that the particle size of Al-doped LiVPO4F is smaller than that of the undoped LiVPO4F and that the smallest particle size is only about 1 μm. The Al-doped LiVPO4F was evaluated as a cathode material for secondary lithium batteries,and exhibited an improved reversibility and cycleability,which may be attributed to the addition of Al^3+ ion by stabilizing the triclinic structure. 相似文献
53.
范燕 《常州信息职业技术学院学报》2021,(2):29-32
本系统以STM32F103RCT6单片机为核心控制芯片,可以一键自动测量容器内液体的重量和液位参数,并显示测量数据、判别液体种类。使用激光与浮板进行液位测量;使用压力传感器与24位AD转化模块HX711进行高精度的重量测量;利用pH值传感器、光电传感器、导电率传感器获得液体不同的物理特性,区分液体种类。系统模块构成主要包括单片机系统模块、电源模块、激光测距模块、称重模块、传感器模块、OLED显示模块和按键模块,具有多功能、测量准确、反应速度快的特点。 相似文献
54.
Shuzhen Liu Guoyan An Qing Cao Tong Li Xinyu Jia Lei Lei 《International journal of molecular sciences》2021,22(11)
Increasing numbers of miRNAs have been observed as oncogenes or tumor suppressors in colorectal cancer (CRC). It was recently reported that hsa-miR-106b-5p (miR-106b) promoted CRC cell migration and invasion. However, there were also studies showing contradictory results. Therefore, in the present study, we further explore the role of miR-106b and its downstream networks in the carcinogenesis of CRC. We observed that the expression of miR-106b is significantly increased in Pan-Cancer and CRC tissues compared with normal tissues from The Cancer Genome Atlas (TCGA) database. Furthermore, we used Transwell, Cell Counting Kit-8, and colony formation assays to clarify that miR-106b promotes the migratory, invasive, and proliferative abilities of CRC cells. For the first time, we systematically screened the target mRNAs and lncRNAs of miR-106b using TCGA database and the bioinformatics algorithms. Dual-luciferase reporter assay confirmed that NR2F2-AS1 and PLEKHO2 are the direct targets of miR-106b. Furthermore, NR2F2-AS1 acts as a competing endogenous RNA (ceRNA) to regulate PLEKHO2 expression by sponging miR-106b. The results of Gene set enrichment analysis (GSEA) and Western blot indicated that they play important roles in CRC progression by regulating MAPK pathway. Thus, miR-106b/NR2F2-AS1/PLEKHO2/MAPK signaling axis may suggest the potential usage in CRC treatment. 相似文献
55.
SF_6因优异的电气特性广泛应用于电器绝缘设备中,但其产生的温室效应对大气环境具有极大损害。近年来,C_5F_(10)O作为一种环保型SF_6潜在替代气体受到国内外科研工作者的关注。为进一步探究C_5F_(10)O/干燥空气与C_5F_(10)O/N_2的绝缘特性,文中利用气体绝缘性能测试平台,对不同气压、不同C_5F_(10)O分压下的2种混合气体在准均匀电场下进行工频击穿试验。实验结果表明,C_5F_(10)O混合气体绝缘强度随气体压强的增大而增大;提高C_5F_(10)O分压亦可提高两类缓冲气体的绝缘强度,且对N_2绝缘强度提升相对值大于干燥空气。从绝缘强度考虑,适当增大C_5F_(10)O混合气体气压和C_5F_(10)O分压,C_5F_(10)O/干燥空气比C_5F_(10)O/N_2混合气体更具潜力替代室内中低压设备中的SF_6。 相似文献
56.
57.
58.
59.
Abstract. We propose the quasi‐maximum likelihood method to estimate the parameters of an RCA(1) process, i.e. a random coefficient autoregressive time series of order 1. The strong consistency and the asymptotic normality of the estimators are derived under optimal conditions. 相似文献
60.
Vapor pressures were determined for several polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) at 75-275 °C, extending the available literature data to more relevant temperature regions and providing the first experimental data for 2,3,7-trichlorodibenzo-p-dioxin (2,3,7-TriCD). A modification of the effusion technique, based upon controlling the diffusion of the target compound and subsequent high resolution gas chromatography/low resolution mass spectrometry (HRGC/LRMS) analysis, was proven comparable to other accepted methods for determining the vapor pressures of semi-volatile organic compounds (SVOCs). Vapor pressures for octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) were in excellent agreement with those reported in literature. The application of the current method for the vapor pressure determinations of eight polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/PCDFs) in the extended temperature range (up to 275 °C) is reported. The extension of the vapor pressures to such temperatures, unprecedented for the PCDDs/Fs, is important for vapor-particle partitioning modeling in regions relevant to PCDD/F formation and control. Estimates for the melting temperatures and enthalpies of sublimation and vaporization are also reported, the latter for which no experimentally determined values have been found in the literature. The use of the method to deliver reproducible, trace concentrations (ppt-ppb) of targets was applied to the calibration of the jet-REMPI/TOFMS as an online detector for low chlorinated PCDDs/Fs. 相似文献