全文获取类型
收费全文 | 634篇 |
免费 | 47篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 13篇 |
综合类 | 42篇 |
化学工业 | 122篇 |
金属工艺 | 6篇 |
机械仪表 | 12篇 |
建筑科学 | 62篇 |
矿业工程 | 6篇 |
能源动力 | 11篇 |
轻工业 | 283篇 |
水利工程 | 2篇 |
石油天然气 | 22篇 |
武器工业 | 2篇 |
无线电 | 15篇 |
一般工业技术 | 46篇 |
冶金工业 | 1篇 |
自动化技术 | 58篇 |
出版年
2024年 | 4篇 |
2023年 | 18篇 |
2022年 | 41篇 |
2021年 | 56篇 |
2020年 | 36篇 |
2019年 | 36篇 |
2018年 | 20篇 |
2017年 | 19篇 |
2016年 | 15篇 |
2015年 | 23篇 |
2014年 | 42篇 |
2013年 | 24篇 |
2012年 | 38篇 |
2011年 | 56篇 |
2010年 | 28篇 |
2009年 | 42篇 |
2008年 | 25篇 |
2007年 | 36篇 |
2006年 | 22篇 |
2005年 | 24篇 |
2004年 | 21篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有703条查询结果,搜索用时 15 毫秒
31.
采用改进的主动轮廓模型算法,实现从蝴蝶兰花簇图像中提取单个花朵图像,为自动识别蝴蝶兰的生长状态奠定基础。首先利用改进的骨架算法和轮廓重生算法,生成蝴蝶兰花簇的初始轮廓;然后利用含有形状能量的主动轮廓模型进行轮廓的演化,使其更接近真实的蝴蝶兰花簇边缘,最后根据蝴蝶兰花蕊位置获得相应的蝴蝶兰花朵。实例验证和比对实验结果表明,该模型能够较好的分割和提取蝴蝶兰花簇中单个花朵,并具有较强的抗噪能力。利用该方法,可以较好的提取蝴蝶兰花簇中的单个花朵,与人工提取效果进行比对,正确率达到了91.5%。 相似文献
32.
目的:寻求合适工艺提取枇杷花叶中的总三萜酸、总黄酮、多糖,并研发枇杷花叶提取物压片糖果制备的最优配方工艺。方法:枇杷花、叶洗净烘干,用搅拌机粉碎、过筛,采用分步法提取花叶(1:1,g/g)中总三萜酸、总黄酮和多糖,以单因素实验法确定其合适的提取工艺参数;在单因素实验基础上,采用正交实验(L9(33))优化枇杷花叶提取物压片糖果的工艺配方。结果:总三萜酸提取的合适工艺为100%乙醇、料液比1:40(g/mL)、提取温度50 ℃、提取时间2 h,粗提物得率为1.6%;总黄酮提取的合适工艺为60%乙醇、料液比1:20(g/mL)、提取温度50 ℃、提取时间2 h,粗提物得率为17.9%;多糖水提的合适工艺为料液比1:15(g/mL)、提取温度80 ℃、提取时间2 h,粗提物得率为1.0%。枇杷花叶提取物压片糖果的最优配方为:枇杷花叶提取物(总三萜酸:总黄酮:多糖=2:18:1,g/g/g)0.2 g、填充剂(微晶纤维素:预胶化淀粉=1:1,g/g)7.5 g、调味剂(木糖醇:柠檬酸=50:1,g/g)5.0 g、硬脂酸镁1%。结论:文章所涉及的提取... 相似文献
33.
34.
在黑河流域的灰棕荒漠土上种植了耐旱牧草小冠花改土培肥效果明显,3年生小冠花与CK比较,0~20 cm土层中自然含水量增加73.93g kg-1、土壤贮水量增加67.17m3hm-2、>0.25mm团粒结构增加12.16%、总孔度增加10.94%、土壤容重降低0.29g cm-3;pH由8.15降到7.83,全盐含量降低1.72g kg-1,脱盐率达到58.70%;土壤有机质增加3.01g kg-1、速效N、P、K分别增加20.9 mg kg-1、5.7 mg kg-1、11.3 mg kg-1,CEC增加7.0 cmol kg-1。3年生小冠花平均株高85.4 cm,单株鲜重1074.2g,单株干重343.8g,鲜草产量72.5 t hm-2,干草产量23.2 t hm-2,产值0.93万元hm-2。 相似文献
35.
本文报道栽培吴茱萸[Evodia rutaecarpa(Juss.)Benth.]花和果实的发育形态学研究结果雌花的花程式为K_(5)C_5A_5(退化)G(5:5:2)。雌花各部分原基发生顺序是:花萼原基→花瓣原基→雄蕊原基→雌蕊群原基。一般为单性结实,无发育正常的种子。花各部分和果皮均具有油细胞和分泌腔。 相似文献
36.
劳伦斯在他的自传体小说<儿子与情人>中运用了大量象征.借助于隐晦的意象和象征性的语言,作者诠释了小说的内在主旨和人物复杂隐蔽的心理.文章着重探究"黑暗"和"花"的象征意义. 相似文献
37.
针对电力系统最优潮流计算的问题提出一种基于梯度蜂群混合算法GABC.利用梯度算法的快速寻优特性得到某一局部极值,然后采用蜂群算法的全局寻优能力跳出该局部极值,并经过反复交替迭代最终找到问题的最优解.通过对IEEE5节点系统的计算结果表明改进后的人工蜂群算法可较好的处理最优潮流约束条件,有效提高基本蜂群算法的全局寻优能力... 相似文献
38.
P.R. DRY M.L. LONGBOTTOM S. MCLOUGHLIN T.E. JOHNSON C. COLLINS 《Australian Journal of Grape and Wine Research》2010,16(S1):47-55
Background and Aims: Flowering and fruitset are principal determinants of grapevine yield. Poor fruitset is said to limit the yield of many varieties in most regions in Australia; however, there is a lack of knowledge of the reproductive performance of most varieties under Australian conditions.
Methods and Results: The reproductive performance of Vitis vinifera winegrape varieties – Cabernet Sauvignon, Chardonnay, Merlot, Nebbiolo, Pinot Noir, Sangiovese, Sauvignon Blanc, Shiraz, Tempranillo, and Zinfandel – was studied in four consecutive growing seasons (commencing in 2004/05) across a range of climatic regions from cool (Adelaide Hills) to warm (Adelaide Plains). Measures of reproductive performance included flower number per inflorescence, fruitset (%), berry number per bunch, coulure index (CI), and millerandage index (MI). Principal component analysis and agglomerative hierarchical classification were used to group the varieties into three classes of reproductive performance.
Conclusions: Certain varieties have a reputation of having 'poor fruitset' that has been inferred from relatively low berry number per bunch; however, for some of these varieties, it is 'low flower number per inflorescence' rather than 'poor fruitset' that is the cause of low berry number.
Significance of the Study: An improved understanding of the reproductive performance of winegrape varieties has been achieved. 相似文献
Methods and Results: The reproductive performance of Vitis vinifera winegrape varieties – Cabernet Sauvignon, Chardonnay, Merlot, Nebbiolo, Pinot Noir, Sangiovese, Sauvignon Blanc, Shiraz, Tempranillo, and Zinfandel – was studied in four consecutive growing seasons (commencing in 2004/05) across a range of climatic regions from cool (Adelaide Hills) to warm (Adelaide Plains). Measures of reproductive performance included flower number per inflorescence, fruitset (%), berry number per bunch, coulure index (CI), and millerandage index (MI). Principal component analysis and agglomerative hierarchical classification were used to group the varieties into three classes of reproductive performance.
Conclusions: Certain varieties have a reputation of having 'poor fruitset' that has been inferred from relatively low berry number per bunch; however, for some of these varieties, it is 'low flower number per inflorescence' rather than 'poor fruitset' that is the cause of low berry number.
Significance of the Study: An improved understanding of the reproductive performance of winegrape varieties has been achieved. 相似文献
39.
Nitrogen was supplied from two fast release sources, ammonium sulfate ((NH4)2SO4) and calcium nitrate (Ca(NO3)2) and a slow release source, isobutylidene diurea (IBDU) to boronia, a new flower crop native to Australia. At lower rates (25 kg per ha), N availability from different sources, as indicated by the leaf N concentration, did not differ within a month after application but three months after application, N availability was higher from IBDU than from (NH4)2SO4 or Ca(NO3)2. At 50 or 100 kg per ha, N availability was higher throughout the year from (NH4)2SO4 or Ca(NO3)2 than from IBDU, thereby allowing luxury consumption and causing toxicity. The flower yield increased with increasing N rates. Complete doses of all N rates which were applied early during the vegetative growth gave the highest yields and the same N rates applied in split doses at different phases of plant growth decreased the yields. In addition, high N availability during flowering (caused by a split dose) further decreased the yield. At all application times, IBDU gave the highest yield and the differences in yields with (NH4)2SO4 and Ca(NO3)2 were not significant. The leaf N concentration associated with maximum yield declined as the plant advanced towards flowering. 相似文献
40.
New improved metaheuristic approaches for optimum design of posttensioned axially symmetric cylindrical reinforced concrete walls 下载免费PDF全文
Two novel hybrid approaches are presented for optimum design of axially symmetric cylindrical walls subjected to posttensioning loads using metaheuristic algorithms such as harmony search (HS), flower pollination algorithm (FPA), and teaching learning based optimization (TLBO). The objective function of the optimization problem is to minimize the total cost of the wall subjected to constraints on the basis of sectional capacities (bending moment, shear force, and axial tension), ACI 318 (building code requirements for structural concrete) requirements and design variables such as wall thickness, compressive strength of concrete, location and intensities of posttensioning cables, size, and spacing of reinforcement. In the optimum design, the performance of the iterative population based metaheuristic algorithms, HS, FPA, and TLBO are compared and tested by taking wall thickness as discrete and continuous variable. In order to improve the efficiency on finding global optimum results, hybrid forms of the HS combined with FPA and TLBO are effective for the optimization problem. 相似文献