全文获取类型
收费全文 | 3859篇 |
免费 | 116篇 |
国内免费 | 59篇 |
专业分类
电工技术 | 171篇 |
综合类 | 172篇 |
化学工业 | 665篇 |
金属工艺 | 93篇 |
机械仪表 | 122篇 |
建筑科学 | 69篇 |
矿业工程 | 52篇 |
能源动力 | 952篇 |
轻工业 | 194篇 |
水利工程 | 13篇 |
石油天然气 | 726篇 |
武器工业 | 11篇 |
无线电 | 90篇 |
一般工业技术 | 175篇 |
冶金工业 | 205篇 |
原子能技术 | 149篇 |
自动化技术 | 175篇 |
出版年
2023年 | 57篇 |
2022年 | 98篇 |
2021年 | 146篇 |
2020年 | 121篇 |
2019年 | 122篇 |
2018年 | 97篇 |
2017年 | 102篇 |
2016年 | 81篇 |
2015年 | 75篇 |
2014年 | 225篇 |
2013年 | 186篇 |
2012年 | 202篇 |
2011年 | 290篇 |
2010年 | 208篇 |
2009年 | 198篇 |
2008年 | 195篇 |
2007年 | 217篇 |
2006年 | 178篇 |
2005年 | 142篇 |
2004年 | 153篇 |
2003年 | 154篇 |
2002年 | 111篇 |
2001年 | 111篇 |
2000年 | 97篇 |
1999年 | 78篇 |
1998年 | 61篇 |
1997年 | 45篇 |
1996年 | 50篇 |
1995年 | 48篇 |
1994年 | 37篇 |
1993年 | 27篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1985年 | 5篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1964年 | 11篇 |
1963年 | 3篇 |
1961年 | 3篇 |
1960年 | 2篇 |
1959年 | 2篇 |
1958年 | 4篇 |
1956年 | 3篇 |
排序方式: 共有4034条查询结果,搜索用时 15 毫秒
41.
新型清洁压裂液的实验室合成 总被引:4,自引:0,他引:4
研制出一种新型的双子季铵盐表面活性剂———N,N-双十八烷基-N,N,N,N-四醇乙基-二溴乙二铵(Gemini-OHAB),对用Gemini-OHAB及其它辅剂配制的新型压裂液体系性能进行了研究。结果表明:该体系具有良好的粘弹性、悬砂性能、低温溶解性以及抗温稳定性能;而且由于双子季铵盐表面活性剂中引入了醇乙基,该新型压裂液体系解决了传统季铵盐类清洁压裂液体系的低温不溶性及高生物毒性,也克服了甜菜碱类清洁压裂液体系抗温性能低的缺点,具有良好的市场应用前景。 相似文献
42.
介绍了蒸汽锅炉水位控制系统中如何应用一个加法器,实现当主汽流量变化较大时,给水流量跟踪主汽流量来达到控制汽包水位目的的一种控制方法。 相似文献
43.
汽轮机转子热应力在线计算灰色数学模型 总被引:6,自引:1,他引:5
热应力计算中边界条件、物性参数和初始条件等模型输入参数的灰色特性,使得以近似点值为输入得到的计算结果缺乏准确性依据和度量,该文提出的灰色数学模型,用区间数代替近似点值建立灰色数学模型,得出热应力在线计算值的灰色描述,可以更好地符合工程计算需要。文中针对模型应用的复杂程度,以汽轮机转子为对象,对单纯灰边界问题给出了简单的端点计算法及其依据;对复合灰边界灰物性问题建立了差分格式的数学模型,应用区间高斯迭代算法,结合模型结构特点推导了简易的基于内包含不等式的算法,并且给出两种算法的数值算例对比。 相似文献
44.
曙—区超稠油间歇蒸汽吞吐技术探讨 总被引:3,自引:1,他引:2
针对曙-区超稠油井进入高周期后产量递减,成本上升的矛盾,提出用间歇吞吐技术改善高周期蒸汽吞吐效果,通过对吞吐机理和现场实际资料统计的分析。对这项技术实施的条件及效果进行了探讨。结果表明,该项技术在高周期井实施效果较好。具有较好的推广前景。 相似文献
45.
There have been extensive attempts in recent years to perform spatial equilibrium analysis of commodity markets, particularly that of energy. Most of these attempts have been based on linear programming transportation models, and more recently quadratic programming models. Unfortunately, neither of these modelling approaches can deal with the case of multi-commodity analysis with non-symmetric regression coefficients. In this paper, we overcome this problem by employing the linear complementarity programming model. In addition, we show how the model can be applied to coal and gas energy flows within a single region. Future potential applications of the model are also implied. 相似文献
46.
汽轮机自动控制系统的可靠性预测 总被引:2,自引:0,他引:2
本文提出了汽轮机自动控制系统可靠性的预测方法,给出了汽轮机自动控制系统的可靠
性框图、子系统部件严重的失效模式、系统可用度的预测公式和可靠性预测实例. 相似文献
47.
Wenlu Song Rui Huang Hao Guo Chunguang Yin Chuanling Wang Jun Cheng Weijuan Yang 《中国化学工程学报》2021,37(9):114-120
Steam pretreatment was employed to disrupt microalgal cells for lipids extraction.Effects of steam pre-treatment on microstructure of microalgal cells were investigated through scanning electron microscopy(SEM) and transmission electron microscopy (TEM).Effect of treatment on lipid extraction was also stud-ied.Microalgal cell walls were distorted after steam pretreatment due to the hydrolysis of organic macro-molecules contained in cell wall.Maximum curvature was increased from 1.88 × 10-6 m-1 to 1.43 × 10-7 m-1 after treatment with the steam at 130 ℃.The fractal dimension of microalgal cells increased from 1.25 to 1.30 after pretreatment for 15 min,and further increased to 1.47 when the pre-treatment time was increased to 60 min.Increased steam pretreatment temperature and time enhanced the hydrolysis of organic macromolecules,and finally destroyed microalgal cell walls at pretreatment temperature of 130 ℃ and pretreatment time of 60 min.Lipid extracted from wet microalgal was signif-icantly increased (2.1-fold) after pretreatment. 相似文献
48.
Synergistic Effect of PVDF-Coated PCL-TCP Scaffolds and Pulsed Electromagnetic Field on Osteogenesis
Yibing Dong Luvita Suryani Xinran Zhou Padmalosini Muthukumaran Moumita Rakshit Fengrui Yang Feng Wen Ammar Mansoor Hassanbhai Kaushik Parida Daniel T. Simon Donata Iandolo Pooi See Lee Kee Woei Ng Swee Hin Teoh 《International journal of molecular sciences》2021,22(12)
Bone exhibits piezoelectric properties. Thus, electrical stimulations such as pulsed electromagnetic fields (PEMFs) and stimuli-responsive piezoelectric properties of scaffolds have been investigated separately to evaluate their efficacy in supporting osteogenesis. However, current understanding of cells responding under the combined influence of PEMF and piezoelectric properties in scaffolds is still lacking. Therefore, in this study, we fabricated piezoelectric scaffolds by functionalization of polycaprolactone-tricalcium phosphate (PCL-TCP) films with a polyvinylidene fluoride (PVDF) coating that is self-polarized by a modified breath-figure technique. The osteoinductive properties of these PVDF-coated PCL-TCP films on MC3T3-E1 cells were studied under the stimulation of PEMF. Piezoelectric and ferroelectric characterization demonstrated that scaffolds with piezoelectric coefficient d33 = −1.2 pC/N were obtained at a powder dissolution temperature of 100 °C and coating relative humidity (RH) of 56%. DNA quantification showed that cell proliferation was significantly enhanced by PEMF as low as 0.6 mT and 50 Hz. Hydroxyapatite staining showed that cell mineralization was significantly enhanced by incorporation of PVDF coating. Gene expression study showed that the combination of PEMF and PVDF coating promoted late osteogenic gene expression marker most significantly. Collectively, our results suggest that the synergistic effects of PEMF and piezoelectric scaffolds on osteogenesis provide a promising alternative strategy for electrically augmented osteoinduction. The piezoelectric response of PVDF by PEMF, which could provide mechanical strain, is particularly interesting as it could deliver local mechanical stimulation to osteogenic cells using PEMF. 相似文献
49.
通过对国外电液锤技术的引述,介绍了目前国内电液锤技术的发展与应用状况,并展望了电液锤发展前景。 相似文献
50.