全文获取类型
收费全文 | 6036篇 |
免费 | 373篇 |
国内免费 | 224篇 |
专业分类
电工技术 | 350篇 |
综合类 | 484篇 |
化学工业 | 139篇 |
金属工艺 | 154篇 |
机械仪表 | 429篇 |
建筑科学 | 131篇 |
矿业工程 | 64篇 |
能源动力 | 651篇 |
轻工业 | 277篇 |
水利工程 | 20篇 |
石油天然气 | 75篇 |
武器工业 | 31篇 |
无线电 | 2012篇 |
一般工业技术 | 151篇 |
冶金工业 | 44篇 |
原子能技术 | 30篇 |
自动化技术 | 1591篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 34篇 |
2021年 | 52篇 |
2020年 | 60篇 |
2019年 | 40篇 |
2018年 | 46篇 |
2017年 | 125篇 |
2016年 | 73篇 |
2015年 | 146篇 |
2014年 | 343篇 |
2013年 | 222篇 |
2012年 | 411篇 |
2011年 | 477篇 |
2010年 | 343篇 |
2009年 | 386篇 |
2008年 | 361篇 |
2007年 | 577篇 |
2006年 | 503篇 |
2005年 | 444篇 |
2004年 | 334篇 |
2003年 | 314篇 |
2002年 | 244篇 |
2001年 | 188篇 |
2000年 | 181篇 |
1999年 | 119篇 |
1998年 | 115篇 |
1997年 | 83篇 |
1996年 | 94篇 |
1995年 | 81篇 |
1994年 | 48篇 |
1993年 | 40篇 |
1992年 | 44篇 |
1991年 | 21篇 |
1990年 | 21篇 |
1989年 | 16篇 |
1988年 | 19篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1962年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有6633条查询结果,搜索用时 15 毫秒
1.
2.
目的以月柿提取物为原料,研究其对2,2-联苯基-1-苦基肼基(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基的清除能力,并测定其多酚类物质没食子酸的含量。方法检测波长为518 nm,反应时间为40 min条件下,以IC_(50)值(清除率为50%时,抗氧化剂的浓度值)作为抗氧化能力评价指标,并采用高效液相色谱法测定其没食子酸含量。结果月柿提取物对于DPPH自由基有良好的清除作用,其IC50值为0.1868 mg/mL,与常用抗氧化剂作用相当,且月柿提取物中没食子酸含量为1.65 g/kg。结论月柿提取物具有很强抗氧化活性,作为化妆品及功能性食品原料有广阔的开发前景。 相似文献
3.
During the last few decades, photothermal radiometry (PTR) has been greatly developed and widely applied in the field of nondestructive testing. However, the traditional PTR system employs an expensive lock-in amplifier to detect the weak photothermal signal, which leads to high cost and long test time. In this paper, a fast transmission PTR system based on sampling by using an internal computer sound card was developed to lower the system cost and shorter the test time. A piece of amorphous silicon (a:Si) thin film solar cells with artificial defects was prepared and tested by the system. The results show that the sharpened defects can be identified easily and quickly according to the significant peaks of the original infrared signal sampled by the internal computer sound card. Furthermore, more detailed defects can be investigated by processing the infrared signal. These validate the effectiveness of the proposed transmission PTR system as a low cost and efficient non-destructive test technique. 相似文献
4.
《Microelectronics Journal》2015,46(6):543-550
In many theories and applications, generalized models can give a good head start for further research where the implementation of new elements and/or boundary conditions could become quite complex. In this paper the development of a compact thermal model of an infrared sensor will be presented. This thermal model includes not only the thermal resistances and capacitances of the sensor structure itself but the radiative and convective thermal resistances to the ambience and between the sensor plate and the heat source (thermal transfer impedance) which is important when the heat source and the sensor are in close proximity. Limitations and the applicability of the proposed model are also discussed. We also aim to present how the proposed model can be used for other IR sensor structures as well. 相似文献
5.
This study proposes that a novel integrated circuit (IC) and system design for renewable energy inverters can harvest renewable energy to power direct current (DC) and alternating current (AC) loads. In addition, an intelligent synthesis and management tool is developed to design the proposed system and to judge the system’s operational maintenance decisions. Finally, a renewable energy inverter’s information is posted to an online system. Users can obtain the proposed system’s information at any time and place. The accurate and superior performance of the proposed IC and system is confirmed by computer simulations and experimental results. 相似文献
6.
为说明高压流动燃油温度对喷油量的影响,进行了高压共轨系统中燃油温度变化及其影响研究,建立了燃油不同的发热和热交换数学模型,构建了高压泵、共轨管和喷油器的燃油温度模型,运用液压流体仿真软件AMESim构建高压共轨系统燃油热仿真计算模型;结合试验数据,验证了高压共轨系统燃油热模型的有效性,分析了不同燃油初始温度下不同部件出口燃油温度的变化。在高压泵转速分别为400r/min和1 600r/min时,高压油泵出口温度增加幅度分别约为4.5℃和23.3℃;在共轨管压力从55MPa增大到140MPa时,共轨管出口的燃油温度仅在35℃~55℃之间变化;在共轨压力为140MPa时,喷孔出口温度变化范围在90℃~110℃之间。燃油温度20℃、40℃时的压力变化较小,燃油温度0℃、60℃时的压力变化较大;在低共轨压力时燃油温度引起的喷油量变化大,高共轨压力时燃油温度引起的喷油量变化小。 相似文献
7.
8.
全国竞技二打一扑克锦标赛是国家体育总局棋牌运动管理中心推出的新兴项目,比赛采用复式赛赛制,然而这种赛制存在无法杜绝线上比赛作弊的问题,为此提出用同等牌力赛制来代替复式赛制进行比赛的设想。本文主要针对如何判定和选取具有同等牌力的初始手牌进行研究,提出用等级难度评估指标来计算初始手牌的难度,初始手牌难度相近的牌认定为同等牌力,并给出了同等牌力的选取方法;为保证一副牌所得等级难度评估指标的可靠性,提出用多个不同水平的“二打一AI程序”来代替真人打牌产生牌谱的方法。实验证明了同等牌力生成方法的有效性,本文提出的同等牌力方法应用于比赛是可行的。 相似文献
9.
Delf-Magnus Kummerfeld Carsten A. Raabe Juergen Brosius Dingding Mo Boris V. Skryabin Timofey S. Rozhdestvensky 《International journal of molecular sciences》2021,22(7)
Prader-Willi syndrome (PWS) is a neurogenetic multifactorial disorder caused by the deletion or inactivation of paternally imprinted genes on human chromosome 15q11-q13. The affected homologous locus is on mouse chromosome 7C. The positional conservation and organization of genes including the imprinting pattern between mice and men implies similar physiological functions of this locus. Therefore, considerable efforts to recreate the pathogenesis of PWS have been accomplished in mouse models. We provide a summary of different mouse models that were generated for the analysis of PWS and discuss their impact on our current understanding of corresponding genes, their putative functions and the pathogenesis of PWS. Murine models of PWS unveiled the contribution of each affected gene to this multi-facetted disease, and also enabled the establishment of the minimal critical genomic region (PWScr) responsible for core symptoms, highlighting the importance of non-protein coding genes in the PWS locus. Although the underlying disease-causing mechanisms of PWS remain widely unresolved and existing mouse models do not fully capture the entire spectrum of the human PWS disorder, continuous improvements of genetically engineered mouse models have proven to be very powerful and valuable tools in PWS research. 相似文献
10.