全文获取类型
收费全文 | 147611篇 |
免费 | 16962篇 |
国内免费 | 10906篇 |
专业分类
电工技术 | 12556篇 |
技术理论 | 3篇 |
综合类 | 13294篇 |
化学工业 | 19925篇 |
金属工艺 | 9764篇 |
机械仪表 | 10399篇 |
建筑科学 | 11657篇 |
矿业工程 | 5085篇 |
能源动力 | 4234篇 |
轻工业 | 12799篇 |
水利工程 | 4442篇 |
石油天然气 | 6655篇 |
武器工业 | 2039篇 |
无线电 | 17358篇 |
一般工业技术 | 14211篇 |
冶金工业 | 5787篇 |
原子能技术 | 2725篇 |
自动化技术 | 22546篇 |
出版年
2024年 | 323篇 |
2023年 | 2091篇 |
2022年 | 4475篇 |
2021年 | 6286篇 |
2020年 | 4656篇 |
2019年 | 3625篇 |
2018年 | 3885篇 |
2017年 | 4405篇 |
2016年 | 4145篇 |
2015年 | 6341篇 |
2014年 | 8114篇 |
2013年 | 9447篇 |
2012年 | 11550篇 |
2011年 | 12562篇 |
2010年 | 11985篇 |
2009年 | 11631篇 |
2008年 | 11658篇 |
2007年 | 11323篇 |
2006年 | 10229篇 |
2005年 | 8260篇 |
2004年 | 6073篇 |
2003年 | 4553篇 |
2002年 | 4383篇 |
2001年 | 3925篇 |
2000年 | 2972篇 |
1999年 | 1785篇 |
1998年 | 927篇 |
1997年 | 800篇 |
1996年 | 658篇 |
1995年 | 547篇 |
1994年 | 413篇 |
1993年 | 329篇 |
1992年 | 220篇 |
1991年 | 176篇 |
1990年 | 137篇 |
1989年 | 139篇 |
1988年 | 77篇 |
1987年 | 65篇 |
1986年 | 69篇 |
1985年 | 21篇 |
1984年 | 23篇 |
1983年 | 36篇 |
1982年 | 19篇 |
1981年 | 31篇 |
1980年 | 25篇 |
1979年 | 16篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1959年 | 22篇 |
1951年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
The substitution of coal blending with sawdust had been widely investigated for metallurgical coke production. In this paper, the physiochemical structures of the semicoke derived from sawdust/coals blends co-coking were characterized by several analytical techniques including FTIR-ATR, XPS, NMR, OM, and SEM. Meanwhile, the influence of the sawdust on the physicochemical properties of the sawdust/coals blends were also investigated. Results indicated that partial substitution of coal blending with sawdust benefited from the formation of colloid and optical anisotropy due to the positive synergetic effect, whereas high proportion of sawdust (>10 wt%) inhibited the agglomeration of semi-coke. On the other hand, the semicoke consisted primarily of aromatic carbons replaced by the oxygen linked to carbons and aliphatic carbons when the coal blending was replaced by high proportion of sawdust, causing a less polyaromatic graphite-like structure formation in the semicoke. 相似文献
33.
Junjie Fu Chaolan Liu Li Li Jun Liu Yu Tie Xueping Wen Qikai Zhao Zongwei Qiao Zheming An Jia Zheng 《International Journal of Food Science & Technology》2022,57(5):2918-2931
Weak acids inhibit the growth of probiotics, such as Saccharomyces boulardii. We explored the tolerance of S. boulardii to different weak acids. S. boulardii had better fermentation ability under lactic acid conditions compared with acetic and butyric acid conditions; however, the budding of S. boulardii was significantly stronger than that of Saccharomyces cerevisiae under acetic acid conditions. Although the surface structure of S. boulardii was destroyed, it produced more daughter cells. S. boulardii metabolites were also significantly different from S. cerevisiae under acidic stress. The growth of S. boulardii under weak acid conditions differed significantly from that of S. cerevisiae. S. boulardii-mediated fingerprints under weak acid conditions were identified as latent biomarkers, related to fructose and mannose metabolism, tricarboxylic acid cycle, and the glycolysis pathway. Identified biomarkers will aid in the genetic engineering of S. boulardii and other Saccharomyces strains for improved acid resistance and biomass yield. 相似文献
34.
为深入了解云南澜沧江流域不同茶区晒青茶的品质差异,选取比较澜沧、双江2个茶区的24个乡镇晒青茶样,采用感官审评与品质理化成分检测,分析不同茶区晒青茶主要理化成分和感官品质方面存在的差异。结果表明:澜沧、双江2个茶区晒青茶的茶多酚平均值分别为24.43%、23.18%;游离氨基酸平均值分别为2.72%、3.97%;咖啡碱平均值分别为4.90%、4.48%;水浸出物平均值分别为45.67%、44.29%;酚氨比均值分别为9.40、6.07。澜沧、双江2个茶区不同产地的晒青茶茶多酚、游离氨基酸、咖啡碱、水浸出物和酚氨比之间存在一定差异。不同的内含化学成分,使各茶区的晒青茶感官品质明显不同。澜沧茶区的晒青茶滋味整体较醇和、稍涩,部分稍带花香与焦味;双江茶区的晒青茶整体滋味较浓醇、微涩带苦,部分平和。 相似文献
35.
37.
[目的]建立10%精草铵膦铵盐可溶液剂的超高效液相色谱-三重四级杆质谱(UPLC-MS/MS)定量分析方法。[方法]使用Zorbax SB-C18色谱柱,流动相为0.1%甲酸水-乙腈,流速为0.3 m L/min,在多反应监测(MRM)模式下进行正离子扫描,测定样品中精草铵膦的含量。[结果]在0.005~0.5 mg/L的质量浓度范围内,方法线性相关性良好,相关系数R2为0.9996,标准偏差为0.056,变异系数为0.56%,加标回收率在97.82%~100.84%之间。[结论]该方法操作简便、准确度和精密度高,适用于10%精草铵膦铵盐可溶液剂的定量分析。 相似文献
38.
39.
Qing Li Jun Wang Jie Ma Meng Ni Fan Yang Peng Liu Kuo Yang Lee Hsing-I Hsiang Deyuan Shen Dingyuan Tang 《Journal of the American Ceramic Society》2022,105(5):3375-3381
High-efficiency Yb:Y2O3 laser ceramics were fabricated using the vacuum-sintering plus hot isostatic pressing (HIP) without sintering additives. High-purity well-dispersed nanocrystalline Yb:Y2O3 powder was synthesized using a modified co-precipitation method in-house. The green bodies were first vacuum sintered at a temperature as low as 1430°C and then HIPed at 1450°C. Finally, the samples were air annealed at 800°C for 10 h. Although no sintering aids were used, full density of the samples with excellent optical homogeneity and an inline transmission of 80% at 400 nm could be obtained. Moreover, photodarkening phenomenon was not detected in the ceramics. Preliminary laser experiment with the fabricated ceramics in a two-mirror cavity has demonstrated 32 W continuous-wave (CW) output at ∼1077 nm with an optical-to-optical conversion efficiency of 58.2%. To the best of our knowledge, this is so far the highest CW output power and optical-to-optical conversion efficiency achieved with the Yb3+-doped sesquioxide ceramics in a simple two-mirror cavity. 相似文献