全文获取类型
收费全文 | 10832篇 |
免费 | 908篇 |
国内免费 | 430篇 |
专业分类
电工技术 | 480篇 |
综合类 | 446篇 |
化学工业 | 1752篇 |
金属工艺 | 612篇 |
机械仪表 | 699篇 |
建筑科学 | 603篇 |
矿业工程 | 237篇 |
能源动力 | 364篇 |
轻工业 | 554篇 |
水利工程 | 179篇 |
石油天然气 | 424篇 |
武器工业 | 34篇 |
无线电 | 1614篇 |
一般工业技术 | 1724篇 |
冶金工业 | 885篇 |
原子能技术 | 103篇 |
自动化技术 | 1460篇 |
出版年
2024年 | 44篇 |
2023年 | 157篇 |
2022年 | 285篇 |
2021年 | 410篇 |
2020年 | 339篇 |
2019年 | 323篇 |
2018年 | 327篇 |
2017年 | 312篇 |
2016年 | 309篇 |
2015年 | 410篇 |
2014年 | 492篇 |
2013年 | 698篇 |
2012年 | 647篇 |
2011年 | 712篇 |
2010年 | 579篇 |
2009年 | 603篇 |
2008年 | 540篇 |
2007年 | 524篇 |
2006年 | 482篇 |
2005年 | 441篇 |
2004年 | 304篇 |
2003年 | 303篇 |
2002年 | 280篇 |
2001年 | 271篇 |
2000年 | 239篇 |
1999年 | 273篇 |
1998年 | 291篇 |
1997年 | 226篇 |
1996年 | 188篇 |
1995年 | 167篇 |
1994年 | 139篇 |
1993年 | 108篇 |
1992年 | 97篇 |
1991年 | 83篇 |
1990年 | 62篇 |
1989年 | 67篇 |
1988年 | 58篇 |
1987年 | 43篇 |
1986年 | 35篇 |
1985年 | 39篇 |
1984年 | 29篇 |
1983年 | 20篇 |
1982年 | 35篇 |
1981年 | 26篇 |
1980年 | 17篇 |
1979年 | 14篇 |
1977年 | 20篇 |
1976年 | 19篇 |
1974年 | 19篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Xueru Chen Yin Zhang Dashui Yuan Wu Huang Jing Ding Hui Wan Wei-Lin Dai Guofeng Guan 《材料科学技术学报》2021,71(12):211-220
Porous g-C3N4 nanosheets (PCN) were prepared by the nickel-assisted one-step thermal polymerization method.Hydrogen (H2) which was produced by the reaction between nickel (Ni) foam and ammonia (NH3) defined the structure and properties of PCN.During the formation of PCN,the participation of H2 not only enhanced the spacing between layers but also boosted the specific surface area that more active sites were exposed.Additionally,H2 promoted pores formation in the nanosheets,which was beneficial to the transfer of photons through lamellar structure and improved the absorption efficiency of visible light.Remarkably,the obtained PCN possessed better Cr(Ⅵ) photocatalytic reduction efficiency than pure g-C3N4.The reaction rate constant (k) of PCN (0.013 min-1) was approximately twice that of bare g-C3N4 (0.007 min-1).Furthermore,the effects of original pH and concentration of Cr(Ⅵ)-containing solution on removal efficiency of Cr(Ⅵ) were explored.A possible photocatalytic mechanism was proposed based on the experiments of radical scavengers and photoelectrochemical characterizations. 相似文献
2.
Weigang Liang Beibei Wang Guofeng Shen Suzhen Cao Bertrand Mcswain Ning Qin Liyun Zhao Dongmei Yu Jicheng Gong Shanshan Zhao Yawei Zhang Xiaoli Duan 《Indoor air》2020,30(2):264-274
Stunting adversely affects physical and mental outcomes of children. It has not been examined whether household air pollution from solid fuel combustion is a risk factor for stunting in children. In a total of 41,439 children aged 6-17 across China, height was measured using a unified protocol. Multivariable linear regression models and logistic regression models were used to assess the associations of solid fuel use for cooking/heating with stunting in children. Adjusted for covariates, cooking/heating with solid fuel was significantly associated with a lower z-score for height for age and sex (β = −0.21 [−0.32 to −0.09] and −0.17 [−0.31 to −0.03], respectively) and an increased risk of stunting with an estimated ORs of 1.34 [1.07~1.68] and 1.37 [1.02~1.83], respectively. The risk of stunting associated with solid fuel use was statistically significant in high-age children. And the effect was greater on girls than on boys, though the difference was not statistically significant. Our study suggested that Chinese children living in households using solid fuel had a significantly higher risk of stunting than those living in households using cleaner fuel. 相似文献
3.
4.
5.
6.
Wei-Cheng Tang Yi-Che Su Yun-Shan Huang Ya-Tin Yu Hsin-Lung Chen I-Ming Chu 《应用聚合物科学杂志》2019,136(39):48003
While perfluoroalkyl acids (PFAAs), also known as C8s, are used extensively in textile repellent coatings, concerns have arisen for their carcinogenicity and hazardous effects on the environment. In this study, a novel water-based, nonfluoro, and nanobrush textile repelling agent was prepared by conventional sol–gel chemistry using amorphous fumed silica and n-octyltriethoxysilane as the starting materials. Minimal interaction between the designed repelling agent and marketed water-based resins was confirmed using linear viscosity region (LVR) analysis and asymmetric-flow field-flow fractionation (AF4), suggesting the self-stratification potential of the repelling agent. More specifically, the repelling agent exhibited excellent compatibility and self-stratifying ability with a force-emulsified acrylic-based resin, affording a water contact angle of 104.3° when incorporated at 7% solid content. Performance tests carried out on thermoplastic polyurethane (TPU) revealed excellent adhesion (100/100) of a final formulation, and a significant increase in water contact angle from 80.1° to 103.8° after treatment. In addition, the fouling area after the removal of a submerged sample from a mixture of slurry, polymer, and oil decreased from 48 to 1% when the repelling agent was added. Moreover, the sludge-fouling property remained unchanged after 1000 cycles of abrasion. These findings demonstrate the potential of the described nonfluoro, nanobrush repelling agent as an environmentally safe alternative for use with commercial resins, in turn realizing a fully water-based hydrophobic coating. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48003. 相似文献
7.
Chen Yonghong Chu Zhaorong Wei Yijun Liu Xingqin Meng Guangyao 《中国稀土学报(英文版)》2006,24(3):301-301
Pr0.6-x NdxCa0.4 FeO3-δ ( x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6) were synthesized using Pechini method. A number of studies were conducted concerning composition, specific area, crystalline structure and microstructure of the samples by means of FT-IR, BET, XRD TG-DTA and SEM. The results show that all the samples with different doping amounts of Pr^3+ and Nd^3+ on A-site are fine dispersed, and mean particle size less than 100 nm. The powders have good sinterability, and the relative density is 95% after sintered at 1200 ℃ for 2 h. It is found that all specimens are entirely single phase solid solutions with orthorhombic perovskite structure, the stable perovskitetype phase is formed completely after calcination at 900 ℃. 相似文献
8.
介绍了循环伏安法的产生背景、原理。应用该技术可以快速、方便地对润滑油中抗氧剂、总酸(碱)值进行测定,并且可以对不同厂家润滑油的抗氧剂包进行区别。该技术还可以有效地评价润滑油的使用寿命和设备工作状况。 相似文献
9.
10.
吸湿干爽性涤纶长丝的研制 总被引:1,自引:0,他引:1
采用德国吉玛公司直纺和日本东丽公司卷绕设备,探索差别化吸湿干爽性涤纶长丝的生产工艺。 相似文献