全文获取类型
收费全文 | 13968篇 |
免费 | 1122篇 |
国内免费 | 508篇 |
专业分类
电工技术 | 72篇 |
技术理论 | 1篇 |
综合类 | 914篇 |
化学工业 | 2545篇 |
金属工艺 | 432篇 |
机械仪表 | 241篇 |
建筑科学 | 580篇 |
矿业工程 | 309篇 |
能源动力 | 409篇 |
轻工业 | 6865篇 |
水利工程 | 435篇 |
石油天然气 | 644篇 |
武器工业 | 26篇 |
无线电 | 274篇 |
一般工业技术 | 781篇 |
冶金工业 | 478篇 |
原子能技术 | 225篇 |
自动化技术 | 367篇 |
出版年
2024年 | 81篇 |
2023年 | 228篇 |
2022年 | 473篇 |
2021年 | 576篇 |
2020年 | 570篇 |
2019年 | 513篇 |
2018年 | 432篇 |
2017年 | 481篇 |
2016年 | 552篇 |
2015年 | 530篇 |
2014年 | 721篇 |
2013年 | 809篇 |
2012年 | 1054篇 |
2011年 | 1005篇 |
2010年 | 651篇 |
2009年 | 653篇 |
2008年 | 548篇 |
2007年 | 779篇 |
2006年 | 702篇 |
2005年 | 654篇 |
2004年 | 522篇 |
2003年 | 492篇 |
2002年 | 421篇 |
2001年 | 314篇 |
2000年 | 295篇 |
1999年 | 256篇 |
1998年 | 200篇 |
1997年 | 164篇 |
1996年 | 137篇 |
1995年 | 154篇 |
1994年 | 83篇 |
1993年 | 96篇 |
1992年 | 98篇 |
1991年 | 56篇 |
1990年 | 56篇 |
1989年 | 48篇 |
1988年 | 41篇 |
1987年 | 27篇 |
1986年 | 23篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
111.
112.
分析了粉料纯度及配料控制对炭阳极生产和炭阳极成品率的影响,结合中国铝业青海分公司的生产状况,从预焙阳极配料控制方面,就如何提高炭阳极成品率、保持生阳极生产工艺稳定进行论述。 相似文献
113.
大庆常压渣油催化裂解反应规律研究 总被引:9,自引:0,他引:9
采用小型固定流化床实验装置,以大庆常压渣油为原料,针对Ca-Al裂解催化剂,详细分析了催化裂解气体产品和液体产品的组成,考察了反应温度、剂油比、水油比和停留时间对裂解产物分布的影响。发现各操作条件对大庆常渣催化裂解产物分布具有不同程度的影响,其中反应温度的影响最大;随反应温度的升高,乙烯产率单调增加,而丙烯、丁烯和总低碳烯烃产率均存在一个最大值。在优化的操作条件下,乙烯质量产率可达25%,总低碳烯烃质量产率超过50%。 相似文献
114.
Yield stress measurements of gas/liquid/fibre suspensions, were conducted to examine the effect of gas concentration as well as fibre concentration. Obtaining a well mixed stable pulp suspension with gas was difficult. A transparent model system consisting of glass fibres submersed in refractive index matched liquid gave stable suspensions and had the additional advantage of allowing visual observations. The measurements were performed in a baffled shear tester and concentrations were in the range of 0–12.5% vol. gas and 8–14% wt. fibres. Results show that yield stress decreases with increasing gas fraction for constant fibre concentrations. Since the fibre concentration is defined in the liquid phase, the amount of fibres decreases with increasing gas concentration. This fact alone partly explains the decrease in yield stress, but the gas also has a direct impact on the decrease in yield stress. Further, as expected, the yield stress increases with increasing fibre concentrations when the gas fraction is kept constant. 相似文献
115.
Effects of N application and water supply on yield, oil content and N accumulation by canola, cultivar Marnoo, grown on a heavy clay soil in the Goulburn Murray Irrigation Region were investigated. Treatments were rainfed (Rf) or watered at a deficit of 50 mm (40–60 mm, I50) beginning in the spring. N treatments were 0, 50, 100 or 200 kg N ha–1 at sowing or as split applications of 20/80, and 50/50 kg N ha–1 at sowing and rosette, respectively.Yield (Yg) ranged from 170 to 520 g m–2. Irrigation and N increased yield in both years. Grain yields were increased by N application on the irrigated treatments when 100 or 200 kg N ha–1 was applied. Oil concentrations ranged from a maximum of 46.4% in treatment N0 to a minimum of 40.6% in treatment N200 and was inversely related to seed N concentration. Although fertilizer N decreased oil concentration, it increased the yield of oil.Nitrogen accumulation (Nb) limited yield of all treatments and was described by the equation, Yg = 806[1-EXP(–0.039*Nb)]. This implied a decrease in yield per unit of Nb at the higher rates of fertilizer addition with consequent increases in grain N concentration.The efficiency of water use in the production of grain (WUEg) and biomass (WUEb) were 7.5 and 23 kg ha–1 mm–1 respectively. Nitrogen additions increased WUEg and WUEb in both seasons. Maximum values of 8.9 (WUEg 1986) and 26.8 (WUEb 1987) were measured from treatment N200. These data suggest that the crops made efficient use of the applied water. 相似文献
116.
Henry?S.?Lam Andrew?ProctorEmail author 《Journal of the American Oil Chemists' Society》2003,80(6):563-567
The changes in milled rice FFA content and composition and in conjugated diene (CD) content and bacterial, yeast, and mold
counts were determined at 24, 37, and 50°C and 70% RH over 50 d. There was a rapid rate of FFA formation during the first
few days of storage, which was optimal at 37°C, but that slowed after 2, 4, and 5 d at 37, 24, and 50°C, respectively. There
was a second increase in FFA after about day 12 that increased with increasing temperature, indicating nonlipase hydrolysis.
Linoleic and oleic acids were the main components of the total FFA produced on the surface of milled rice. The pattern of
CD development followed that of FFA increase. Bacterial growth correlated with increased FFA levels after 12 d of storage,
suggesting that bacterial lipase rather than bran lipase may be responsible for rice lipid hydrolysis 相似文献
117.
短纤维直径对橡胶复合材料性能的影响 总被引:5,自引:0,他引:5
制备了 3种具有不同直径、相同长径比及其分布的涤纶短纤维增强氯丁橡胶基复合材料。对屈服强度及伸长率、断裂强度及伸长率以及撕裂强度等力学性能的研究发现 :在相同长径比及其分布情况下 ,与传统混合法则不同的是屈服强度和伸长率不相等 ,也不是只取决于短纤维的直径 ,而是受直径和长度的共同作用 ;在相同的纤维体积分数时 ,复合材料的断裂强度基本相同 ,而断裂形变和撕裂强度随纤维直径的减小而增大 相似文献
118.
119.
分析了PVC的拉伸过程,讨论了外力作用速度对PVC的影响.结果表明:PVC的拉伸屈服强度随外力作用速度的提高而提高,断裂伸长率却随之下降. 相似文献
120.