全文获取类型
收费全文 | 180342篇 |
免费 | 15219篇 |
国内免费 | 7640篇 |
专业分类
电工技术 | 10742篇 |
技术理论 | 17篇 |
综合类 | 11859篇 |
化学工业 | 30629篇 |
金属工艺 | 9731篇 |
机械仪表 | 11009篇 |
建筑科学 | 14597篇 |
矿业工程 | 5094篇 |
能源动力 | 5277篇 |
轻工业 | 12528篇 |
水利工程 | 3310篇 |
石油天然气 | 10517篇 |
武器工业 | 1386篇 |
无线电 | 20940篇 |
一般工业技术 | 21771篇 |
冶金工业 | 8436篇 |
原子能技术 | 1936篇 |
自动化技术 | 23422篇 |
出版年
2024年 | 655篇 |
2023年 | 2879篇 |
2022年 | 5056篇 |
2021年 | 7338篇 |
2020年 | 5628篇 |
2019年 | 4616篇 |
2018年 | 5129篇 |
2017年 | 5704篇 |
2016年 | 5083篇 |
2015年 | 7038篇 |
2014年 | 8756篇 |
2013年 | 10371篇 |
2012年 | 11463篇 |
2011年 | 12363篇 |
2010年 | 10595篇 |
2009年 | 10116篇 |
2008年 | 9900篇 |
2007年 | 9354篇 |
2006年 | 9452篇 |
2005年 | 8256篇 |
2004年 | 5795篇 |
2003年 | 5094篇 |
2002年 | 4733篇 |
2001年 | 4277篇 |
2000年 | 4557篇 |
1999年 | 5022篇 |
1998年 | 4281篇 |
1997年 | 3577篇 |
1996年 | 3378篇 |
1995年 | 2892篇 |
1994年 | 2389篇 |
1993年 | 1695篇 |
1992年 | 1351篇 |
1991年 | 1020篇 |
1990年 | 807篇 |
1989年 | 713篇 |
1988年 | 552篇 |
1987年 | 369篇 |
1986年 | 247篇 |
1985年 | 160篇 |
1984年 | 109篇 |
1983年 | 78篇 |
1982年 | 104篇 |
1981年 | 67篇 |
1980年 | 60篇 |
1979年 | 23篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
为了给海面溢油污染识别检测提供理论基础,根据菲涅尔反射公式的偏振反射系数,结合偏振双向反射率因子和粗糙海面的概率密度分布函数,建立了完善的pBRDF模型,仿真在不同太阳入射角度、不同探测器观测角度以及不同海面风速风向等条件下海水和油膜的偏振反射分布函数。结果表明:海水和油膜太阳天顶角为53°和56°时P偏振反射率分别为1.0×10^-5和2.5×10^-5,S偏振反射率随着太阳天顶角的增加而增加;海面风速越大偏振反射率峰值越小;海面风向只改变pBRDF的空间位置;海水和油膜线偏振度空间分布有明显差异。搭建实验平台相机以40°拍摄时,得出海水和油膜的线偏振度分别在0.2~0.4, 0.5~0.7之间,同时表明利用偏振探测获取目标场景的偏振度和偏振角图可提高图像质量。 相似文献
132.
本文旨在改善某选厂硫精矿浓密机溢流跑浑问题,对生产现场进行勘察和分析,分析浓密机溢流跑浑的原因,并开展原矿配比和沉降试验研究。对采场原矿矿样和硫精矿矿浆进行系统的试验研究,分别采用不同沉降方案进行条件试验,考察絮凝剂种类、絮凝剂用量、pH调整剂用量、不同药剂之间的配比等条件对沉降的影响,确定合适的原矿配比及合理药剂制度,有效地控制金属在溢流中的损失,充分获取现有产品的蕴含价值。 相似文献
133.
134.
Simulating the psychological experience of human vision,a road extraction model based on the format tower is proposed to extract the road in the high resolution remote sensing image from the perspective of morphology.Firstly,based on the spectral and texture information,the suspected road targets are extracted by using segmentation technology.Then these targets are classified according to their reliability and extract the road targets for each category.Finally,three types of identified road information are verified and merged,and the continuous smooth road extraction results are obtained.Experiments on real high resolution images show that the results are consistent with the visual perception of the human eye,and the overall classification accuracy is higher,indicating that the algorithm is effective and feasible and has good use value. 相似文献
135.
Neural Computing and Applications - In this paper, an adaptive neural network (NN) output feedback control is investigated for incommensurate fractional-order permanent magnet synchronous motors... 相似文献
136.
137.
Dr. Hui Qiu Richard Caldwell Dr. Lesley Liu-Bujalski Dr. Andreas Goutopoulos Reinaldo Jones Justin Potnick Dr. Brian Sherer Dr. Andrew Bender Dr. Roland Grenningloh Dr. Daigen Xu Dr. Anna Gardberg Dr. Igor Mochalkin Dr. Theresa Johnson Dr. Ariele Viacava Follis Jared Head Dr. Federica Morandi 《ChemMedChem》2019,14(2):217-223
Bruton's tyrosine kinase (Btk) is an attractive target for the treatment of a wide array of B-cell malignancies and autoimmune diseases. Small-molecule covalent irreversible Btk inhibitors targeting Cys481 have been developed for the treatment of such diseases. In clinical trials, probe molecules are required in occupancy studies to measure the level of engagement of the protein by these covalent irreversible inhibitors. The result of this pharmacodynamic (PD) activity provides guidance for appropriate dosage selection to optimize inhibition of the drug target and correlation of target inhibition with disease treatment efficacy. This information is crucial for successful evaluation of drug candidates in clinical trials. Based on the pyridine carboxamide scaffold of a novel solvent-accessible pocket (SAP) series of covalent irreversible Btk inhibitors, we successfully developed a potent and selective affinity-based biotinylated probe 12 (2-[(4-{4-[5-(1-{5-[(3aS,4S,6aR)-2-oxo-hexahydro-1H-thieno[3,4-d]imidazol-4-yl]pentanamido}-3,6,9,12-tetraoxapentadecan-15-amido)pentanoyl]piperazine-1-carbonyl}phenyl)amino]-6-[1-(prop-2-enoyl)piperidin-4-yl]pyridine-3-carboxamide). Compound 12 has been used in Btk occupancy assays for preclinical studies to determine the therapeutic efficacy of Btk inhibition in two mouse lupus models driven by TLR7 activation and type I interferon. 相似文献
138.
Zhao Hongliang Lu Tingting Liu Fengqin Yin Pan Wang Sen 《JOM Journal of the Minerals, Metals and Materials Society》2019,71(5):1643-1649
JOM - The Isa/Ausmelt smelting technology with a top submerged lance (TSL) has been extensively used in copper smelting processes. However, the TSL is extremely vulnerable to damage and failure... 相似文献
139.
Identification of vivianite,an unusual blue pigment,in a sixteenth century painting and its implications
下载免费PDF全文
![点击此处可从《Color research and application》网站下载免费的PDF全文](/ch/ext_images/free.gif)
António João Cruz Erica Eires Luís Dias Teresa Desterro Carla Rego 《Color research and application》2018,43(2):177-183
Vivianite, a blue pigment employed in the past practically only in Northern and Central Europe, but with very limited use, was identified in an early sixteenth century painting, stylistically with Flemish features, from a church in Portugal. The identification of this iron phosphate mineral was made by SEM‐EDS based on the atomic ratio between phosphorus and iron in layers of blue paint (area analysis) and in particles of these same layers (spot analysis). This painting, about which there is no document to prove its authorship, becomes the first case, known in detail, of a sixteenth century painting containing vivianite. Moreover, this find and the presence of a chalk ground, also identified, strongly support the hypothesis of being a Flemish painting. 相似文献
140.
Isopimaric acid is a typical rosin compound and can account for 30% of the total mass of slash pine rosin. The molecular structure of isopimaric acid derivatives features an unsaturated double bond at the C13 position, opening up the possibility of their industrial polymerization. In this study, isopimaric acid (95.4%), methyl isopimarate (99.5%), and allyl isopimarate (95.1%) were prepared as highly pure monomers. New experimental results are presented and mechanisms based on the investigation of free-radical polymerization under UV irradiation are proposed. New rosin monomers for potential value-added utilization of woody biomass are also identified. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47817. 相似文献