全文获取类型
收费全文 | 21261篇 |
免费 | 2095篇 |
国内免费 | 925篇 |
专业分类
电工技术 | 1190篇 |
技术理论 | 5篇 |
综合类 | 1488篇 |
化学工业 | 3550篇 |
金属工艺 | 1202篇 |
机械仪表 | 1288篇 |
建筑科学 | 1571篇 |
矿业工程 | 607篇 |
能源动力 | 561篇 |
轻工业 | 2357篇 |
水利工程 | 346篇 |
石油天然气 | 1086篇 |
武器工业 | 137篇 |
无线电 | 2607篇 |
一般工业技术 | 2515篇 |
冶金工业 | 884篇 |
原子能技术 | 198篇 |
自动化技术 | 2689篇 |
出版年
2025年 | 12篇 |
2024年 | 508篇 |
2023年 | 505篇 |
2022年 | 784篇 |
2021年 | 1053篇 |
2020年 | 802篇 |
2019年 | 775篇 |
2018年 | 755篇 |
2017年 | 761篇 |
2016年 | 690篇 |
2015年 | 918篇 |
2014年 | 1086篇 |
2013年 | 1229篇 |
2012年 | 1381篇 |
2011年 | 1300篇 |
2010年 | 1167篇 |
2009年 | 1115篇 |
2008年 | 1052篇 |
2007年 | 993篇 |
2006年 | 977篇 |
2005年 | 809篇 |
2004年 | 597篇 |
2003年 | 757篇 |
2002年 | 972篇 |
2001年 | 758篇 |
2000年 | 541篇 |
1999年 | 468篇 |
1998年 | 277篇 |
1997年 | 235篇 |
1996年 | 225篇 |
1995年 | 180篇 |
1994年 | 138篇 |
1993年 | 118篇 |
1992年 | 82篇 |
1991年 | 67篇 |
1990年 | 59篇 |
1989年 | 37篇 |
1988年 | 29篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1959年 | 2篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
本文首先研究了相关性约束运动估值算法,然后提出了基于运动矢量插值的运动估值算法,实验表明新算法的预测性能明显比传统块匹配运动估值算法(BMA)好,而且预测图象的主观质量得到显著改善。 相似文献
33.
Zhao Yan Yu Han Liying Lin Ying Xue Chao Ma Wai Kit Ng Kam Sing Wong Kei May Lau 《光:科学与应用(英文版)》2021,(11):2143-2152
The deployment of photonic integrated circuits (PICs) necessitates an integration platform that is scalable, high-throughput, cost-effective, and power-efficien... 相似文献
34.
Runqiang Yu Bining Xue Jiaqi Liao Wanting Zhu Jiayuan Fu 《Fullerenes, Nanotubes and Carbon Nanostructures》2021,29(1):28-38
AbstractIn the present study, lanthanum modified carbon nanotubes (La-CNTs) were prepared by the impregnation method and used as adsorbents to remove oxytetracycline (OTC) from aquaculture wastewater. La-CNTs were characterized by SEM, EDS, XRD, BET analysis. The effects of adsorbent dosage, concentration of OTC, adsorption time, pH and interfering ions on the adsorption of OTC by La-CNTs were investigated. The optimum adsorbent dosage, OTC concentration, adsorption equilibrium time and pH for OTC adsorption by La-CNTs are 0.03?g, 20?mg/L, 180?min and 7, respectively. The outcome of the kinetics studies showed a significant linear correlation between the experimental results and the quasi-second-order kinetics model. As an adsorption isotherm model, the Langmuir model showed a very good consistency with the adsorption of OTC by La-CNTs, as the maximum adsorption quantity reached 117.23?mg/g. Through the thermodynamic analysis showed that the adsorption of OTC by La-CNTs was an endothermic process of entropy increase, which occurs spontaneously. The predominant forces promoting this adsorption were van der Waals force, π-π electron donor-acceptor interaction, and electrostatic interaction. 相似文献
35.
Scientometrics - Breakthrough research in scientific fields usually comes as a manifestation of major development and advancement. These advances build to an epiphany where new ways of thinking... 相似文献
36.
In this study, the mass attenuation coefficient of boron-containing ores in the Liaoning province of China was calculated using Win XCOM software to investigate the shielding effectiveness of these ores against gamma rays. The mass attenuation coefficients were also calculated using MCNP-4 B code and compared with Win XCOM results; consequently, a good consistency between the results of Win XCOM and MCNP-4 B was observed. Furthermore, the G-P fitting method was used to evaluate the values of exposure buildup factor(EBF) in the energy range of 0.015–15 Me V up to 40 mean free paths. Among the selected ores, boron-bearing iron concentrate ore(M3)was determined to be the best gamma ray shielding ore owing to its higher values of mass attenuation coefficient and equivalent atomic number and lower value of EBF.Moreover, American Evaluated Nuclear Data File(ENDF/B-VII) was used to analyze the shielding effectivenessagainst thermal neutrons. It was determined that Szaibelyite(M2) is the best thermal neutron shielding material.This study would be useful for demonstrating the potential of boron-containing ores for applications in the field of nuclear engineering and technology. 相似文献
37.
38.
经济全球化和"互联网+"时代的到来,对师范院校教育教学带来了机遇与挑战。文章从师范院校的教学改革目标出发,提出了师范院校教育教学改革的主要方向,即倡导平等的生态和谐理念、构建人文精神的课程体系和完善精准高效的质量保障系统,并从调整教学重心、转变教师角色、完善课程体系、强化人文精神、改善教学环境和健全质量保障系统六个方面探讨了改革的路径,希望为师范院校的发展提供借鉴。 相似文献
39.
Xue Liu Shiyao Cui Caiyun Dan Wenle Li Hongqing Xie Conghui Li Liangen Shi 《International journal of molecular sciences》2022,23(24)
Phellinus baumii, a fungus that grows on mulberry trees and is used in traditional Chinese medicine, exerts therapeutic effects against various diseases, including cancer. Polyphenols, generally considered to be antioxidants, have antitumor and proapoptotic effects. In this study, we identified the composition of Phellinus baumii polyphenol (PBP) and characterized its 17 chemical components by UPLC–ESI–QTOF–MS. Furthermore, to clarify the potential mechanism of PBP against Lung Cancer Cells, network pharmacology and experimental verification were combined. Molecular docking elucidated the binding conformation and mechanism of the primary active components (Osmundacetone and hispidin) to the core targets CASP3, PARP1 and TP53. In addition, potential molecular mechanisms of PBP predicted by network pharmacology analysis were validated in vitro. PBP significantly inhibited the human lung cancer A549 cells and showed typical apoptotic characteristics, without significant cytotoxicity to normal human embryonic kidney (HEK293) cells. Analysis using flow cytometry and western blot indicated that PBP caused apoptosis, cell cycle arrest, reactive oxygen species (ROS) accumulation, and mitochondrial membrane potential (MMP) depression in A549 cells to exercise its antitumor effects. These results reveal that PBP has great potential for use as an active ingredient for antitumor therapy. 相似文献
40.
Wang Yonggang Ma Xiaoyu Xue Yinghong Sun Hong Zhang Zhigang and Wang Qingyue 《半导体学报》2005,26(2):250-253
A novel high reflectivity type of semiconductor saturable absorption mirror grown by metal organic chemical vapor deposition is presented. Using the mirror as well as an end mirror,passively mode locked Yb∶YAB laser is realized,which produces a pulse as short as 305ps at 1.044μm.The pulse frequency is 375MHz;the output power is 45mW. 相似文献