全文获取类型
收费全文 | 109638篇 |
免费 | 7498篇 |
国内免费 | 4350篇 |
专业分类
电工技术 | 5865篇 |
技术理论 | 3篇 |
综合类 | 6069篇 |
化学工业 | 14723篇 |
金属工艺 | 4254篇 |
机械仪表 | 5470篇 |
建筑科学 | 6119篇 |
矿业工程 | 2164篇 |
能源动力 | 2446篇 |
轻工业 | 6547篇 |
水利工程 | 2017篇 |
石油天然气 | 3058篇 |
武器工业 | 927篇 |
无线电 | 9896篇 |
一般工业技术 | 11113篇 |
冶金工业 | 24106篇 |
原子能技术 | 1118篇 |
自动化技术 | 15591篇 |
出版年
2024年 | 296篇 |
2023年 | 1034篇 |
2022年 | 1757篇 |
2021年 | 2500篇 |
2020年 | 1896篇 |
2019年 | 1613篇 |
2018年 | 2141篇 |
2017年 | 2650篇 |
2016年 | 2857篇 |
2015年 | 3519篇 |
2014年 | 3724篇 |
2013年 | 4559篇 |
2012年 | 6719篇 |
2011年 | 7313篇 |
2010年 | 5281篇 |
2009年 | 5244篇 |
2008年 | 5066篇 |
2007年 | 4860篇 |
2006年 | 4667篇 |
2005年 | 6839篇 |
2004年 | 5106篇 |
2003年 | 4373篇 |
2002年 | 3200篇 |
2001年 | 2815篇 |
2000年 | 2061篇 |
1999年 | 2087篇 |
1998年 | 7222篇 |
1997年 | 4708篇 |
1996年 | 3321篇 |
1995年 | 2157篇 |
1994年 | 1595篇 |
1993年 | 1524篇 |
1992年 | 601篇 |
1991年 | 559篇 |
1990年 | 522篇 |
1989年 | 447篇 |
1988年 | 426篇 |
1987年 | 285篇 |
1986年 | 270篇 |
1985年 | 230篇 |
1984年 | 92篇 |
1983年 | 93篇 |
1982年 | 153篇 |
1981年 | 198篇 |
1980年 | 207篇 |
1979年 | 69篇 |
1978年 | 102篇 |
1977年 | 612篇 |
1976年 | 1326篇 |
1975年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
21.
Guo-Yu Li Ya-Xin Zheng Fu-Zhou Sun Jian Huang Meng-Meng Lou Jing-Kai Gu Jin-Hui Wang 《International journal of molecular sciences》2015,16(9):22190-22204
This study aimed at investigating the possible mechanisms of hepatic protective activity of Cichorium intybus L. (chicory) in acute liver injury. Pathological observation, reactive oxygen species (ROS) detection and measurements of biochemical indexes on mouse models proved hepatic protective effect of Cichorium intybus L. Identification of active compounds in Cichorium intybus L. was executed through several methods including ultra performance liquid chromatography/time of flight mass spectrometry (UPLC-TOF-MS). Similarity ensemble approach (SEA) docking, molecular modeling, molecular docking, and molecular dynamics (MD) simulation were applied in this study to explore possible mechanisms of the hepato-protective potential of Cichorium intybus L. We then analyzed the chemical composition of Cichorium intybus L., and found their key targets. Furthermore, in vitro cytological examination and western blot were used for validating the efficacy of the selected compounds. In silico analysis and western blot together demonstrated that selected compound 10 in Cichorium intybus L. targeted Akt-1 in hepatocytes. Besides, compound 13 targeted both caspase-1 and Akt-1. These small compounds may ameliorate liver injury by acting on their targets, which are related to apoptosis or autophagy. The conclusions above may shed light on the complex molecular mechanisms of Cichorium intybus L. acting on hepatocytes and ameliorating liver injury. 相似文献
22.
23.
为了避免回收单一钕铁硼废料中有价元素带来的操作复杂和资源浪费等问题,本研究采用共沉淀法共沉淀出钕铁硼废料中的有价元素Me(Nd,Pr,Co,Fe),制备可用于生产再生钕铁硼的原料;根据质量守恒和同时平衡原理,采用MATLAB软件建立Me(Nd,Pr,Co,Fe)-OH--NH3热力学模型,绘制lg[Me]-p H曲线模拟共沉淀工艺,并根据模拟结果确立了共沉淀工艺;模拟和实验的结果表明:根据lg[Me]-p H模拟结果可以确立一步共沉淀法的p H:6~10,Fe3+比Fe2+更易于沉淀完全;在上述条件下获得的共沉淀粉末主相均为Nd,Pr,Co,Fe的化合物,且有价元素的百分比含量均大于99.4%;其中,当p H值在8左右时回收率最高,在该条件下金属元素Me(Nd,Pr,Co,Fe)的沉淀效率分别为:98.7%,99.9%,93.6%,99.9%。该结果也表明共沉淀法工艺不仅高效,而且所制备的共沉淀粉末可以满足制备二次钕铁硼的需要。 相似文献
24.
25.
Xiaohui Hu Li Cheng Yan Hong Zhaofeng Li Caiming Li Zhengbiao Gu 《International Journal of Food Science & Technology》2021,56(8):4149-4158
Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%. 相似文献
26.
Wireless Personal Communications - The purpose of this study is to construct a structural equation model of shared bicycle added psychological factors proceeding from the theory of planned... 相似文献
27.
28.
Initialization speed is one of the most important factors in network real time kinematic (NRTK) performance. Owing to the low correlation among the error s 相似文献
30.
Manjin Kim Qinfen Gu Tanveer Hussain Yahia Ali Trevor B. Abbott Kazuhiro Nogita 《International Journal of Hydrogen Energy》2021,46(53):27096-27106
With superior properties of Mg such as high hydrogen storage capacity (7.6 wt% H/MgH2), low price, and low density, Mg has been widely studied as a promising candidate for solid-state hydrogen storage systems. However, a harsh activation procedure, slow hydrogenation/dehydrogenation process, and a high temperature for dehydrogenation prevent the use of Mg-based metal hydrides for practical applications. For these reasons, Mg-based alloys for hydrogen storage systems are generally alloyed with other elements to improve hydrogen sorption properties. In this article, we have added Na to cast Mg–La alloys and achieved a significant improvement in hydrogen absorption kinetics during the first activation cycle. The role of Na in Mg–La has been discussed based on the findings from microstructural observations, crystallography, and first principles calculations based on density functional theory. From our results in this study, we have found that the Na doped surface of Mg–La alloy systems have a lower adsorption energy for H2 compared to Na-free surfaces which facilitates adsorption and dissociation of hydrogen molecules leading to improvement of absorption kinetic. The effect of Na on the microstructure of these alloys, such as eutectic refinement and a density of twins is not highly correlated with absorption kinetics. 相似文献