全文获取类型
收费全文 | 4804367篇 |
免费 | 317150篇 |
国内免费 | 182022篇 |
专业分类
电工技术 | 259321篇 |
技术理论 | 125篇 |
综合类 | 261485篇 |
化学工业 | 703108篇 |
金属工艺 | 230543篇 |
机械仪表 | 258167篇 |
建筑科学 | 268141篇 |
矿业工程 | 111356篇 |
能源动力 | 135123篇 |
轻工业 | 394981篇 |
水利工程 | 99986篇 |
石油天然气 | 141742篇 |
武器工业 | 35465篇 |
无线电 | 514439篇 |
一般工业技术 | 586521篇 |
冶金工业 | 564644篇 |
原子能技术 | 63679篇 |
自动化技术 | 674713篇 |
出版年
2023年 | 42761篇 |
2022年 | 101825篇 |
2021年 | 145219篇 |
2020年 | 104944篇 |
2019年 | 85654篇 |
2018年 | 102566篇 |
2017年 | 112639篇 |
2016年 | 103790篇 |
2015年 | 125477篇 |
2014年 | 171637篇 |
2013年 | 272182篇 |
2012年 | 280458篇 |
2011年 | 319252篇 |
2010年 | 286017篇 |
2009年 | 286358篇 |
2008年 | 292969篇 |
2007年 | 284388篇 |
2006年 | 258019篇 |
2005年 | 215241篇 |
2004年 | 153432篇 |
2003年 | 117898篇 |
2002年 | 110539篇 |
2001年 | 101597篇 |
2000年 | 98642篇 |
1999年 | 81337篇 |
1998年 | 142752篇 |
1997年 | 100708篇 |
1996年 | 85365篇 |
1995年 | 66880篇 |
1994年 | 58135篇 |
1993年 | 49877篇 |
1992年 | 33205篇 |
1991年 | 30005篇 |
1990年 | 29821篇 |
1989年 | 28888篇 |
1988年 | 26770篇 |
1987年 | 24360篇 |
1986年 | 23688篇 |
1985年 | 25471篇 |
1984年 | 22082篇 |
1983年 | 20278篇 |
1982年 | 19163篇 |
1981年 | 19529篇 |
1980年 | 18756篇 |
1979年 | 16821篇 |
1978年 | 16240篇 |
1977年 | 22926篇 |
1976年 | 33669篇 |
1975年 | 14036篇 |
1974年 | 13030篇 |
排序方式: 共有10000条查询结果,搜索用时 48 毫秒
211.
Prof. Andrea Baier Dr. Anne Kokel Dr. William Horton Ewa Gizińska Dr. Garima Pandey Prof. Ryszard Szyszka Prof. Béla Török Prof. Marianna Török 《ChemMedChem》2021,16(12):1927-1932
A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays. 相似文献
212.
目的:设计一款满足安全、卫生、操作便捷、结构性能稳定等要求的糖霜制品3D打印机.方法:打印机主要包括机械结构和控制系统,机械结构方面采用龙门架结构,并对传统的打印料罐进行改良.控制系统采用“工控机+运动控制卡”的模式.结果:该打印机可快速更换料罐(30s内),打印机成型速度快(≥5000mm/min),速度可调;成型精度控制在1mm 以内;成型件的强度、膨胀率和表面粗糙度指标均较好.自带光源的图像识别及处理系统能够识别产品形状、个数及完整性等.结论:改良后的料罐提高了半流体食品打印的卫生性、生产效率,且便于耗材的更换,能加工出复杂糖画模型以满足造型独特的个性化糖艺制品的需求. 相似文献
213.
Samani Saeideh Vadiati Meysam Azizi Farahnaz Zamani Efat Kisi Ozgur 《Water Resources Management》2022,36(10):3627-3647
Water Resources Management - Precise estimation of groundwater level (GWL) might be of great importance for attaining sustainable development goals and integrated water resources management.... 相似文献
214.
215.
This study deals with the anodisation of titanium grade 2 in 0.5-M sulphuric acid using a pulsed signal in a unipolar regime. The electrical parameters investigated are voltage, frequency and duty cycle. The use of duty cycles with a high percentage of anodic polarisation (90%), combined with high frequencies (1000 Hz) and the higher voltage tested (220 V), favoured the establishment of a plasma regime involving strong dielectric discharges, allowing the growth of thicker oxides but with rough architecture. The corrosion resistance of the formed film has been characterised by potentiodynamic tests in 0.5-M NaBr for localised corrosion resistance and by immersion tests in 10% v/v sulphuric acid solution for a uniform corrosion assessment. Current–time curves, visual observations and electron microscope analysis (scanning electron microscopy, energy-dispersive X-ray spectroscopy) were the tools selected to provide a correlation between technological parameters and oxide growth mechanism. For localised and uniform corrosion, anodisation at 220 V with a high level of anodic polarisation (90%) and frequency (1000 Hz) was verified to be particularly advantageous. 相似文献
216.
Multimedia Tools and Applications - Since Noar and Shamir introduced visual cryptography scheme (VCS), the cheating problem of VCS has absorbed much attention of scholars. The current researches on... 相似文献
217.
Nienke Visser Harm Jan Lourens Gerwin Huls Edwin Bremer Valerie R. Wiersma 《International journal of molecular sciences》2021,22(5)
Elevated activation of the autophagy pathway is currently thought to be one of the survival mechanisms allowing therapy-resistant cancer cells to escape elimination, including for cytarabine (AraC)-resistant acute myeloid leukemia (AML) patients. Consequently, the use of autophagy inhibitors such as chloroquine (CQ) is being explored for the re-sensitization of AraC-resistant cells. In our study, no difference in the activity of the autophagy pathway was detected when comparing AraC-Res AML cell lines to parental AraC-sensitive AML cell lines. Furthermore, treatment with autophagy inhibitors CQ, 3-Methyladenine (3-MA), and bafilomycin A1 (BafA1) did not re-sensitize AraC-Res AML cell lines to AraC treatment. However, in parental AraC-sensitive AML cells, treatment with AraC did activate autophagy and, correspondingly, combination of AraC with autophagy inhibitors strongly reduced cell viability. Notably, the combination of these drugs also yielded the highest level of cell death in a panel of patient-derived AML samples even though not being additive. Furthermore, there was no difference in the cytotoxic effect of autophagy inhibition during AraC treatment in matched de novo and relapse samples with differential sensitivity to AraC. Thus, inhibition of autophagy may improve AraC efficacy in AML patients, but does not seem warranted for the treatment of AML patients that have relapsed with AraC-resistant disease. 相似文献
218.
Manik Chandra Biswas Samit Chakraborty Abhishek Bhattacharjee Zaheeruddin Mohammed 《Advanced functional materials》2021,31(19):2100257
Shape memory materials (SMMs) in 3D printing (3DP) technology garnered much attention due to their ability to respond to external stimuli, which direct this technology toward an emerging area of research, “4D printing (4DP) technology.” In contrast to classical 3D printed objects, the fourth dimension, time, allows printed objects to undergo significant changes in shape, size, or color when subjected to external stimuli. Highly precise and calibrated 4D materials, which can perform together to achieve robust 4D objects, are in great demand in various fields such as military applications, space suits, robotic systems, apparel, healthcare, sports, etc. This review, for the first time, to the best of the authors’ knowledge, focuses on recent advances in SMMs (e.g., polymers, metals, etc.) based wearable smart textiles and fashion goods. This review integrates the basic overview of 3DP technology, fabrication methods, the transition of 3DP to 4DP, the chemistry behind the fundamental working principles of 4D printed objects, materials selection for smart textiles and fashion goods. The central part summarizes the effect of major external stimuli on 4D textile materials followed by the major applications. Lastly, prospects and challenges are discussed, so that future researchers can continue the progress of this technology. 相似文献
219.
人工智能的普及促进了语音交互技术的发展,语音传感器阵列作为智能语音交互的硬件前端,成为语音交互领域的前沿研究方向.矢量语音传声器自有的偶极子指向性、零点深度以及阵列体积小便于集成的特点特别符合语音交互技术对硬件设备的要求.基于此,通过采用两组矢量敏感单元"共点正交"形成矢量微阵列实现声源空间锐化波束指向,其不受瑞利限与空间采样率限制,与传统空间离散分布的声压麦克风阵列有着本质区别,是矢量微阵列的核心优势所在.矢量微阵列传声器弥补了现有双麦阵列的不足,具有更为广阔的应用前景,作为智能语音交互的硬件前端,对推动智能语音交互领域的发展具有重要意义. 相似文献
220.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration. 相似文献