全文获取类型
收费全文 | 197157篇 |
免费 | 20191篇 |
国内免费 | 11671篇 |
专业分类
电工技术 | 15604篇 |
技术理论 | 6篇 |
综合类 | 15860篇 |
化学工业 | 28358篇 |
金属工艺 | 12160篇 |
机械仪表 | 13398篇 |
建筑科学 | 16499篇 |
矿业工程 | 6599篇 |
能源动力 | 5847篇 |
轻工业 | 14574篇 |
水利工程 | 4743篇 |
石油天然气 | 10293篇 |
武器工业 | 2213篇 |
无线电 | 23610篇 |
一般工业技术 | 20303篇 |
冶金工业 | 8253篇 |
原子能技术 | 2261篇 |
自动化技术 | 28438篇 |
出版年
2024年 | 956篇 |
2023年 | 3264篇 |
2022年 | 6393篇 |
2021年 | 8757篇 |
2020年 | 6687篇 |
2019年 | 5131篇 |
2018年 | 5800篇 |
2017年 | 6778篇 |
2016年 | 5935篇 |
2015年 | 8692篇 |
2014年 | 10939篇 |
2013年 | 13018篇 |
2012年 | 15022篇 |
2011年 | 15564篇 |
2010年 | 14424篇 |
2009年 | 13643篇 |
2008年 | 13374篇 |
2007年 | 12694篇 |
2006年 | 11755篇 |
2005年 | 9275篇 |
2004年 | 6400篇 |
2003年 | 5497篇 |
2002年 | 5230篇 |
2001年 | 4571篇 |
2000年 | 3821篇 |
1999年 | 3286篇 |
1998年 | 2270篇 |
1997年 | 1919篇 |
1996年 | 1756篇 |
1995年 | 1482篇 |
1994年 | 1185篇 |
1993年 | 776篇 |
1992年 | 615篇 |
1991年 | 460篇 |
1990年 | 359篇 |
1989年 | 308篇 |
1988年 | 225篇 |
1987年 | 149篇 |
1986年 | 138篇 |
1985年 | 63篇 |
1984年 | 60篇 |
1983年 | 40篇 |
1982年 | 48篇 |
1981年 | 52篇 |
1980年 | 48篇 |
1979年 | 26篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1959年 | 10篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Tao Li Zehui Du Nobumichi Tamura Mao Ye Saikumar Inguva Wei Lu Xierong Zeng Shanming Ke Haitao Huang 《Journal of the European Ceramic Society》2018,38(4):1488-1497
(1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this work, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25 °C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in x = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (TC), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient. 相似文献
102.
目的: 建立快速灵敏的LC-MS/MS法测定人血浆中阿莫西林浓度,并用于两种阿莫西林胶囊的一致性评价。方法: 采用岛津公司LCMS-8060型LC-MS/MS仪,以MRM模式测定阿莫西林(m/z 366.00/114.00)的浓度,d4-阿莫西林作内标(m/z 370.10/114.05),离子源为ESI源。色谱柱选用Waters ACQUITY BEH C18(2.1×50 mm,1.7 μm),梯度洗脱。血浆样本加入内标,经甲醇沉淀蛋白后取上清液进样检测。结果: 所建方法经验证,其线性、准确度、精密度、最低定量限、提取回收率、特异性、基质效应、稳定性等各项指标均符合CFDA的指导原则及最新核查标准要求,并较文献报道中的方法有处理简单、灵敏度高、色谱峰形好的优点。结论: 所建方法快速、灵敏,适用于人血浆中阿莫西林浓度的检测。用于一致性评价的样本实测,两种制剂生物等效。 相似文献
103.
Baizhan Li Chenqiu Du Hong Liu Wei Yu Jie Zheng Meilan Tan Zhenxing Jin Wenjie Li Jing Wu Lu Chen Runming Yao 《Indoor air》2019,29(2):308-319
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being. 相似文献
104.
Mingzhi Zhao Jianwei Cao Zhi Wang Guohua Li 《Journal of the European Ceramic Society》2019,39(7):2427-2435
The crystallization phenomena of spinel in CaO-MgO-Al2O3-SiO2-Fe2O3 glass have received much attention due to the particular role in preparation of glass-ceramic materials, which represent an effective option to manage hazardous waste. In this study, both preliminary spinel and secondary spinel were precipitated in the precursor glass. The formation of these spinel was meticulously assessed by a combination of X-ray diffractometry and scanning electron microscopy. The structure of the microenvironment in the precursor glass was characterized by Raman spectrums. These advanced techniques highlight the potential for one-step crystallization of the glass. The investigation, which focused on one-step crystallization, demonstrated the growth of pyroxene on spinel accompanying a migration of chromium. The results also show the microstructure of the obtained glass-ceramic was very dependent on the heat-treat temperature. This study not only unambiguously reveals the precipitation mechanisms of spinel but also provides more documentation for one-step crystallization in the glass-ceramics field. 相似文献
105.
106.
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
107.
社会经济的快速发展促进了科学技术水平的显著提升,社会生产生活各个领域当中对计算机网络的应用程度不断提升,当前,网络已经成为了人们日常生活与工作的重要组成部分。为此,加强对网络安全等因素影响研究就显得格外重要。网络环境关系着用户的使用质量,更加影响人们的工作效率,加强对网络安全技术的研究时解决相关问题的核心内容。本文针对网络安全威胁因素以及常见的网络安全技术进行了简要分析。 相似文献
108.
109.
Neural Processing Letters - The beta processes (BP) is a powerful nonparametric tool in feature learning, which is often used as the prior of Bernoulli process for choosing features from a feature... 相似文献
110.
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
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)