全文获取类型
收费全文 | 326773篇 |
免费 | 26335篇 |
国内免费 | 13904篇 |
专业分类
电工技术 | 19178篇 |
技术理论 | 31篇 |
综合类 | 21444篇 |
化学工业 | 53953篇 |
金属工艺 | 19146篇 |
机械仪表 | 21487篇 |
建筑科学 | 26060篇 |
矿业工程 | 10629篇 |
能源动力 | 9313篇 |
轻工业 | 19406篇 |
水利工程 | 5764篇 |
石油天然气 | 21649篇 |
武器工业 | 2970篇 |
无线电 | 36459篇 |
一般工业技术 | 38019篇 |
冶金工业 | 16182篇 |
原子能技术 | 3432篇 |
自动化技术 | 41890篇 |
出版年
2024年 | 563篇 |
2023年 | 4868篇 |
2022年 | 7433篇 |
2021年 | 12320篇 |
2020年 | 9534篇 |
2019年 | 8007篇 |
2018年 | 9066篇 |
2017年 | 10329篇 |
2016年 | 9042篇 |
2015年 | 12880篇 |
2014年 | 15948篇 |
2013年 | 19194篇 |
2012年 | 20926篇 |
2011年 | 22785篇 |
2010年 | 20092篇 |
2009年 | 19147篇 |
2008年 | 18581篇 |
2007年 | 18092篇 |
2006年 | 18766篇 |
2005年 | 16405篇 |
2004年 | 10813篇 |
2003年 | 9502篇 |
2002年 | 8965篇 |
2001年 | 7930篇 |
2000年 | 8034篇 |
1999年 | 9030篇 |
1998年 | 7119篇 |
1997年 | 6022篇 |
1996年 | 5659篇 |
1995年 | 4693篇 |
1994年 | 3885篇 |
1993年 | 2755篇 |
1992年 | 2239篇 |
1991年 | 1646篇 |
1990年 | 1226篇 |
1989年 | 961篇 |
1988年 | 779篇 |
1987年 | 506篇 |
1986年 | 378篇 |
1985年 | 255篇 |
1984年 | 166篇 |
1983年 | 113篇 |
1982年 | 138篇 |
1981年 | 92篇 |
1980年 | 73篇 |
1979年 | 28篇 |
1978年 | 4篇 |
1973年 | 4篇 |
1959年 | 5篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 243 毫秒
991.
Sheng WANG Jun WANG Yingjie XU Weihong ZHANG Jihong ZHU 《Frontiers of Mechanical Engineering》2020,15(2):319-327
Frontiers of Mechanical Engineering - Lattice structures have numerous outstanding characteristics, such as light weight, high strength, excellent shock resistance, and highly efficient heat... 相似文献
992.
993.
Yue Gao Miao-miao Zhang Xiao-peng Guo Wen-jian Li Dong Lu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(5):1290-1297
Toxicity caused by the accumulation of butanol in fermentation media is an important factor limiting the concentration of butanol. There is currently no systematic research in place investigating the butanol tolerance mechanism of bacteria such as Clostridium acetobutylicum, which adapts to butanol stress and regulates its growth and metabolism. Here, research results related to the butanol tolerance of C. acetobutylicum are reviewed to understand the molecular basis of changes in butanol-tolerant strains. Organic solvent-tolerant bacteria play an important role in the fields of biofuel production, enzyme preparation and bioremediation. An analysis of limitations of the application of organic solvent-tolerant bacteria has revealed that future research should focus on combining the microbial tolerance phenotype with specific utilization to achieve an optimal balance between organic solvent tolerance and production. This review serves as a reference for the improvement and engineering of strains that tolerate organic solvents. © 2019 Society of Chemical Industry 相似文献
994.
995.
996.
荆山玉是湖北省保康县新发现的一个玉石品种,形成于大陆边缘—洋盆区过渡带的热水沉积环境,为晚震旦世—早寒武世灯影组的一种硅质角砾岩:原地震碎角砾岩,由角砾和胶结物二部分构成,角砾局部可拼接;角砾成分为早期硅质岩碎裂产物,胶结物除早期硅质岩碎裂产物外,还有少量后期充填的石英、铁质等,受角砾、胶结物颗粒大小、裂隙发育程度不同的影响,后期热液改造程度不同,角砾和胶结物化学成分存在一定的差异,色调与铁质有关。荆山玉的形成主要经历了三个阶段的演化:第一阶段,低温150~225℃、弱氧化—弱还原条件下热水成因的硅质岩形成;第二阶段,热力膨胀外力作用下,硅质岩局部原地震碎形成硅质角砾岩,热水温度243~340℃,富氧氧化—贫氧过渡环境,红褐色的Fe~(3+)在胶结物、裂隙中富集;第三阶段,热水温度116~127℃、缺氧还原条件,黄色的Fe~(2+)在胶结物、裂隙中富集。 相似文献
997.
Rong Zhang Hailong Hu Hai Chen Siqi Li Cheng Ying Shuai Huang Qingting Liu Xudong Fu Shengfei Hu Ching-Ping Wong 《应用聚合物科学杂志》2020,137(39):49186
Recently, thermal interface materials (TIMs) are in great demands for modern electronics. For mechanically mixed polymer composite TIMs, the thermal conductivity and the mechanical properties are generally lower than expected values due to the sharply increased viscosity and poor filler dispersion. This work shows that addition of a small amount of polyester-based hyperbranched polymer (HBP) avoided the trade-off in mechanically mixed ABS/hexagonal boron nitride (h-BN) composites. After adding 0.5 wt% HBP, the maximum h-BN content in the composites increased from 50 to 60 wt%. The out-of-plane, in-plane thermal conductivity, and tensile strength of ABS/h-BN with 50 wt% h-BN were 0.408, 0.517 W/mK, and 18 MPa, respectively, and were increased to 0.729, 0.847 W/mK, and 32 MPa by adding 0.5 wt% HBP, while 0.972, 1.12 W/mK, and 29.5 MPa were achieved for ABS/h-BN/HBP with 60 wt% h-BN. The morphological and rheological results proved that these enhancements are due to the improved h-BN dispersion by decreasing viscosity of composites during mixing. Theoretical modeling based on the modified effective medium theory confirmed such results and showed that the interfacial thermal resistance also decreased slightly. Thus, this work demonstrates a facile and scalable method for simultaneously improving the thermal conductivity and mechanical properties of thermoplastic-based TIMs. 相似文献
998.
Ming Chang Fangcheng Qiu Niannian Lan Tao Zhang Xin Guo Qingzhe Jin Ruijie Liu Xingguo Wang 《Lipids》2020,55(4):353-363
In China, Camellia oleifera oil (COO) is not only a common edible oil but also a traditional remedy widely applied to ameliorate a variety of illnesses associated with inflammation, such as mouth ulcers, thrush, eczema, etc. However, there has been a lack of relevant biological research on the anti-inflammatory capacity of COO, and the specific bioactive lipid phytochemicals contributing to the anti-inflammatory effect need further research. In this study, the RAW 264.7 macrophages model was used to investigate the anti-inflammatory capacity of COO. Our data showed that 33–200 μg/mL COO markedly inhibited the lipopolysaccharide lipopolysaccharide (LPS)-stimulated nitric oxide (NO.) secretion via the suppression of Nos2 and Cox-2 expression. The enzyme immunoassay confirmed that COO also exhibited a strong suppressive effect on the expression of proinflammatory cytokines such as Tnf-α and Il-6. To further explore the correlation between the anti-inflammatory effects and the lipid phytochemicals in COO, 10 samples were collected and screened for their chemical compositions. It was interestingly demonstrated that the polyphenol extracts of COO play a vital role in its anti-inflammatory properties. In addition, an oil-in-water (O/W) emulsion-based system was also developed to deliver the liposoluble COO into the cells, and the feasibility of this system was confirmed. Our research confirms the anti-inflammatory potential of COO and highlights that the main functional ingredient is polyphenol extracts. This may provide a scientific basis for the comprehensive utilization and development of COO and related functional foods. 相似文献
999.
ABSTRACT In this study, effect of calcium and gypsum on scheelite and fluorite was investigated using sodium oleate as collector. Micro-flotation and contact angle results showed that the adsorption of calcium could inhibit the hydrophobicity of scheelite and fluorite. Moreover, sulfate could enhance the inhibition. FT-IR results showed that calcium could be priori precipitated into calcium oleate and adsorb on mineral surface. The adsorption of calcium could increase the scheelite potential to IEP, while it showed limited effect on fluorite potential. However, the interaction of calcium on scheelite and fluorite in gypsum solution was more complex than that in calcium solution. 相似文献
1000.
Wang Yan Chao Yan Na Wang Ting Zhang Ting Fei Yao 《Russian Journal of Nondestructive Testing》2020,56(4):318-327
Russian Journal of Nondestructive Testing - To investigate the effect of basalt fiber on the fracturing process and damage mechanism of cement-based materials under axial compression, acoustic... 相似文献