全文获取类型
收费全文 | 7391篇 |
免费 | 848篇 |
国内免费 | 302篇 |
专业分类
电工技术 | 313篇 |
综合类 | 373篇 |
化学工业 | 2617篇 |
金属工艺 | 700篇 |
机械仪表 | 122篇 |
建筑科学 | 99篇 |
矿业工程 | 669篇 |
能源动力 | 73篇 |
轻工业 | 480篇 |
水利工程 | 17篇 |
石油天然气 | 135篇 |
武器工业 | 16篇 |
无线电 | 438篇 |
一般工业技术 | 962篇 |
冶金工业 | 1440篇 |
原子能技术 | 23篇 |
自动化技术 | 64篇 |
出版年
2024年 | 31篇 |
2023年 | 142篇 |
2022年 | 206篇 |
2021年 | 234篇 |
2020年 | 254篇 |
2019年 | 199篇 |
2018年 | 183篇 |
2017年 | 232篇 |
2016年 | 274篇 |
2015年 | 256篇 |
2014年 | 384篇 |
2013年 | 444篇 |
2012年 | 568篇 |
2011年 | 544篇 |
2010年 | 452篇 |
2009年 | 393篇 |
2008年 | 334篇 |
2007年 | 472篇 |
2006年 | 460篇 |
2005年 | 363篇 |
2004年 | 323篇 |
2003年 | 281篇 |
2002年 | 327篇 |
2001年 | 223篇 |
2000年 | 176篇 |
1999年 | 135篇 |
1998年 | 135篇 |
1997年 | 103篇 |
1996年 | 77篇 |
1995年 | 65篇 |
1994年 | 49篇 |
1993年 | 38篇 |
1992年 | 26篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1974年 | 3篇 |
排序方式: 共有8541条查询结果,搜索用时 15 毫秒
121.
采用盐雾试验测试了锌镀层钝化膜的耐蚀性,研究了硫脲对镀锌层硅酸盐钝化作用的影响。实验结果表明,在硅酸盐钝化液中加入一定量的硫脲,可以使镀锌层转化膜的耐蚀性增强,但当其浓度较低时却会降低转化膜的耐蚀性。 相似文献
122.
以2-氯吡啶为原料,在冰醋酸介质中,用双氧水氧化生成N-氧化-2-氯吡啶.N-氧化-2-氯吡啶与NaSH反应进行巯基化,再经制备钠盐,最终与ZnSO4螯合得到N-氧化-2-巯基吡啶锌盐.通过熔点、核磁氢谱及X射线单晶衍射对产物进行了表征及晶体结构分析.分析结果表明,该晶体属于单斜晶系,P21/C空间群,a=0.840 10(17)nm,b=1.018 4(2)nm,c=1.373 6(3)nm,α=90.00°,β=97.23(3)°,γ=90.00°,Dx=1.810 g/cm3,Z=4,F(000)=640,μ=2.453 mm-1.最终偏差因子分别为R=0.032 5,wR=0.072 8. 相似文献
123.
124.
介绍了氯化物镀锌液中硝酸根、铬酸根等阴离子,以及油污、光亮剂分解产物、表面活性剂等有机杂质的影响和去除方法。提出了减少有机杂质积累的若干措施,如坚持添加剂少加勤加的原则,控制好溶液组分(尤其是氯化钾和硼酸)和液温、pH等工艺条件,采用增溶性好的载体,以及研发新型光亮剂。 相似文献
125.
Behavior of arsenic in zinc electrowinning 总被引:1,自引:0,他引:1
126.
Emily Scheiermann Mary-Ann Puppa Lothar Rink Inga Wessels 《International journal of molecular sciences》2022,23(4)
Zinc has been suggested to play a role in carcinogenesis and tumor progression. Serum zinc levels of lung cancer patients are for example lower than in healthy individuals. The activation and expression of the epidermal growth factor receptor (EGFR), which plays a role in tumor biology, are presumably influenced by zinc. EGFR activation influences cell adhesion and immune escape. This study provides insights into the impacts of zinc on the EGFR activation and expression of downstream proteins such as E-cadherin and PD-L1 in the alveolar carcinoma cell line A549. To model chronic changes in zinc homeostasis, A549 cells were cultured in media with different zinc contents. EGFR surface expression of unstimulated and stimulated A549 cells was determined by flow cytometry. EGFR phosphorylation as well as the protein expression of E-cadherin and PD-L1 were analyzed by Western blot. In our hands, chronic zinc deficiency led to increased EGFR surface expression, decreased E-cadherin protein expression and increased PD-L1 protein expression. Zinc supplementation decreased EGFR surface expression and PD-L1 protein expression. In summary, zinc-deficient A549 cells may display a more malignant phenotype. Thus, future clinical research should further focus on the possible benefits of restoring disturbed zinc homeostasis, especially in lung cancer patients. 相似文献
127.
Magdalena Zibka Katarzyna Matysiak Katarzyna Walczak Marcin Gajek Katarzyna Cholewa-Kowalska 《International journal of molecular sciences》2022,23(4)
The aim of the work was to obtain hybrid coatings containing silver, copper, and zinc nanoparticles on the TiAlV medical alloy via a sol–gel process. The developed layers were designed to bring about a bactericidal and fungicidal effect, as well as for protection against surgical scratches during the implantation of implants used in veterinary medicine. In this work, the authors focused on evaluating the microstructure (SEM + EDS); the structure (XRD, FTIR); and the surface properties, such as wettability, free surface energy, and roughness of layers with various concentrations of metallic nanoparticles (2 and 5 mol %). Our results confirmed that the sol–gel method enables the easy manufacturing of hybrid layers endowed with different porosity values as well as various shapes and sizes of metallic nanoparticles. A higher concentration of nanoparticles was observed on the surface containing 5 mol % of metallic salts. The highest degree of homogeneity was obtained for the layers containing silver nanoparticles. In addition, the silver nanoparticles were round and had the smallest dimensions, even below 20 nm. The FTIR and XRD structural studies confirmed the presence of an organosilicon matrix containing all three types of the metallic particles. We conclude that the higher concentration of nanoparticles influenced the alloy surface parameters. 相似文献
128.
Alicja Tymczewska Bliss Ursula Furtado Jacek Nowaczyk Katarzyna Hrynkiewicz Aleksandra Szydowska-Czerniak 《International journal of molecular sciences》2022,23(5)
This study aimed to develop and characterize gelatin/polyvinyl alcohol (G/PVA) films loaded with black cumin cake extract (BCCE) and zinc oxide nanoparticles (ZnONPs). The BCCE was also applied for the green synthesis of ZnONPs with an average size of less than 100 nm. The active films were produced by a solvent-casting technique, and their physicochemical and antibacterial properties were investigated. Supplementation of G/PVA film in ZnONPs decreased the tensile strength (TS) from 2.97 MPa to 1.69 MPa. The addition of BCCE and ZnONPs increased the elongation at the break (EAB) of the enriched film by about 3%. The G/PVA/BCCE/ZnONPs film revealed the lowest water vapor permeability (WVP = 1.14 × 10−9 g·mm·Pa−1·h−1·mm−2) and the highest opacity (3.41 mm−1). The QUick, Easy, New, CHEap and Reproducible (QUENCHER) methodologies using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6- sulfonic acid) (ABTS) and cupric ion reducing antioxidant capacity (CUPRAC) were applied to measure antioxidant capacity (AC) of the prepared films. The incorporation of BCCE and ZnONPs into G/PVA films enhanced the AC by 8–144%. The films containing ZnONPs and a mixture of BCCE and ZnONPs inhibited the growth of three Gram-positive bacterial strains. These nanocomposite films with desired functional properties can be recommended to inhibit microbial spoilage and oxidative rancidity of packaged food. 相似文献
129.
针对氧化锌尾矿和废弃水渣等工业固废中有价锌难以回收的问题,以当地工业含锌固废为原料,利用碳热还原氧化法,制备了高纯氧化锌微粉。通过HSC Chemistry进行热力学计算和试验研究结合的方式,分析了含锌废渣中硅酸锌与碳还原反应的热力学过程。讨论了配碳量、焙烧温度、焙烧时间以及CaF2对硅酸锌还原过程锌产率的影响。结果表明,在以CaF2为催化剂时,1 000~1 100℃催化效果最显著。得出最佳工艺条件:在温度为1 100℃、保温时间40 min、碳含量20 wt%、CaF2添加5 wt%的条件下锌产率(氧化锌回收率)为97.44%。对挥发产物进行结构和成分分析,其物相为六方纤锌矿结构的氧化锌晶体,粒度大小2~4μm,纯度达到了99.47%。 相似文献
130.
本文对现有交换机机房配线架保安器的原理及性能进行了分析,并提出改进电路,通过多次试验,性能参数优于目前市场一般产品,且样品尺寸符合标准。 相似文献