全文获取类型
收费全文 | 17130篇 |
免费 | 1524篇 |
国内免费 | 1147篇 |
专业分类
电工技术 | 605篇 |
综合类 | 900篇 |
化学工业 | 6148篇 |
金属工艺 | 1376篇 |
机械仪表 | 559篇 |
建筑科学 | 342篇 |
矿业工程 | 192篇 |
能源动力 | 478篇 |
轻工业 | 979篇 |
水利工程 | 67篇 |
石油天然气 | 1272篇 |
武器工业 | 162篇 |
无线电 | 1921篇 |
一般工业技术 | 1413篇 |
冶金工业 | 823篇 |
原子能技术 | 439篇 |
自动化技术 | 2125篇 |
出版年
2024年 | 109篇 |
2023年 | 407篇 |
2022年 | 920篇 |
2021年 | 997篇 |
2020年 | 732篇 |
2019年 | 482篇 |
2018年 | 390篇 |
2017年 | 506篇 |
2016年 | 577篇 |
2015年 | 567篇 |
2014年 | 764篇 |
2013年 | 932篇 |
2012年 | 948篇 |
2011年 | 1321篇 |
2010年 | 896篇 |
2009年 | 1028篇 |
2008年 | 924篇 |
2007年 | 1006篇 |
2006年 | 967篇 |
2005年 | 777篇 |
2004年 | 598篇 |
2003年 | 567篇 |
2002年 | 522篇 |
2001年 | 500篇 |
2000年 | 436篇 |
1999年 | 386篇 |
1998年 | 280篇 |
1997年 | 228篇 |
1996年 | 185篇 |
1995年 | 163篇 |
1994年 | 134篇 |
1993年 | 120篇 |
1992年 | 108篇 |
1991年 | 73篇 |
1990年 | 67篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 29篇 |
1986年 | 14篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1974年 | 4篇 |
1959年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
将5G无线通信基站安装在电力线杆塔上,可以通过电力线路杆塔共享促进5G网络建设,实现电力企业和通信公司的互利共赢。重点讨论了5G基站的新架构,分析了把基站应用到电力杆塔上应考虑的供电、接地、安装等问题,并给出了相应的解决方案。 相似文献
72.
The calculations of total energy, band structure, and electronic density of states and Mulliken population analysis of β-LaNi5 Hx (5≤x≤8) were performed by adopting the method of total energy based on the density functional theory. The augmented plane wave function was selected as the basis set in combination with ultra-soft pseudo-potential technology. The influence of the amount of H absorbed in alloys was discussed in terms of geometry, electronic structure and thermodynamic derived from calculated results. The results show that the amount of H absorbed and the preferred site occupation of the absorbed hydrogen atoms were controlled by the position of Hbands and the energy gap between H-bands and conduction bands. The β-phase hydrides of LaNi5 are most stable when hydrogen atom capacity coating in the range of 6 - 7. 相似文献
73.
Muhammad Khurram Tufail Niaz Ahmad Le Yang Lei Zhou Muhammad Adnan Naseer Renjie Chen Wen Yang 《中国化学工程学报》2021,39(11):16-36
The development of an inorganic electrochemical stable solid-state electrolyte is essentially responsible for future state-of-the-art all-solid-state lithium batteries (ASSLBs). Because of their advantages in safety, working temperature, high energy density, and packaging, ASSLBs can develop an ideal energy storage system for modern electric vehicles (EVs). A solid electrolyte (SE) model must have an economical synthesis approach, exhibit electrochemical and chemical stability, high ionic conductivity, and low interfacial resistance. Owing to its highest conductivity of 17 mS·cm-1, and deformability, the sulfide-based Li7P3S11 solid electrolyte is a promising contender for the high-performance bulk type of ASSLBs. Herein, we present a current glimpse of the progress of synthetic procedures, structural aspects, and ionic conductivity improvement strategies. Structural elucidation and mechanistic approaches have been extensively discussed by using various characterization techniques. The chemical stability of Li7P3S11 could be enhanced via oxide doping, and hard and soft acid/base (HSAB) concepts are also discussed. The issues to be undertaken for designing the ideal solid electrolytes, interfacial challenges, and high energy density have been discoursed. This review aims to provide a bird's eye view of the recent development of Li7P3S11-based solid-state electrolyte applications and explore the strategies for designing new solid electrolytes with a target-oriented approach to enhance the efficiency of high energy density all-solid-state lithium batteries. 相似文献
74.
Luis O. Soto-Rojas B. Berenice Campa-Crdoba Charles R. Harrington Andrs Salas-Casas Mario Hernandes-Alejandro Ignacio Villanueva-Fierro Marely Bravo-Muoz Linda Garcs-Ramírez Fidel De La Cruz-Lpez Miguel ngel Ontiveros-Torres Goar Gevorkian Mar Pacheco-Herrero Jos Luna-Muoz 《International journal of molecular sciences》2021,22(7)
Alzheimer’s disease (AD) is a neurodegenerative disease, characterized histopathologically by intra-neuronal tau-related lesions and by the accumulation of amyloid β-peptide (Aβ) in the brain parenchyma and around cerebral blood vessels. According to the vascular hypothesis of AD, an alteration in the neurovascular unit (NVU) could lead to Aβ vascular accumulation and promote neuronal dysfunction, accelerating neurodegeneration and dementia. To date, the effects of insoluble vascular Aβ deposits on the NVU and the blood–brain barrier (BBB) are unknown. In this study, we analyze different Aβ species and their association with the cells that make up the NVU. We evaluated post-mortem AD brain tissue. Multiple immunofluorescence assays were performed against different species of Aβ and the main elements that constitute the NVU. Our results showed that there are insoluble vascular deposits of both full-length and truncated Aβ species. Besides, insoluble aggregates are associated with a decrease in the phenotype of the cellular components that constitute the NVU and with BBB disruption. This approach could help identify new therapeutic targets against key molecules and receptors in the NVU that can prevent the accumulation of vascular fibrillar Aβ in AD. 相似文献
75.
Evaluation of Floxuridine Oligonucleotide Conjugates Carrying Potential Enhancers of Cellular Uptake
Anna Avi Anna Clua Maria Jos Bleda Ramon Eritja Carme Fbrega 《International journal of molecular sciences》2021,22(11)
Conjugation of small molecules such as lipids or receptor ligands to anti-cancer drugs has been used to improve their pharmacological properties. In this work, we studied the biological effects of several small-molecule enhancers into a short oligonucleotide made of five floxuridine units. Specifically, we studied adding cholesterol, palmitic acid, polyethyleneglycol (PEG 1000), folic acid and triantennary N-acetylgalactosamine (GalNAc) as potential enhancers of cellular uptake. As expected, all these molecules increased the internalization efficiency with different degrees depending on the cell line. The conjugates showed antiproliferative activity due to their metabolic activation by nuclease degradation generating floxuridine monophosphate. The cytotoxicity and apoptosis assays showed an increase in the anti-cancer activity of the conjugates related to the floxuridine oligomer, but this effect did not correlate with the internalization results. Palmitic and folic acid conjugates provide the highest antiproliferative activity without having the highest internalization results. On the contrary, cholesterol oligomers that were the best-internalized oligomers had poor antiproliferative activity, even worse than the unmodified floxuridine oligomer. Especially relevant is the effect induced by palmitic and folic acid derivatives generating the most active drugs. These results are of special interest for delivering other therapeutic oligonucleotides. 相似文献
76.
Yurii S. Borovikov Daria D. Andreeva Stanislava V. Avrova Vladimir V. Sirenko Armen O. Simonyan Charles S. Redwood Olga E. Karpicheva 《International journal of molecular sciences》2021,22(12)
Point mutations in the genes encoding the skeletal muscle isoforms of tropomyosin can cause a range of muscle diseases. The amino acid substitution of Arg for Pro residue in the 90th position (R90P) in γ-tropomyosin (Tpm3.12) is associated with congenital fiber type disproportion and muscle weakness. The molecular mechanisms underlying muscle dysfunction in this disease remain unclear. Here, we observed that this mutation causes an abnormally high Ca2+-sensitivity of myofilaments in vitro and in muscle fibers. To determine the critical conformational changes that myosin, actin, and tropomyosin undergo during the ATPase cycle and the alterations in these changes caused by R90P replacement in Tpm3.12, we used polarized fluorimetry. It was shown that the R90P mutation inhibits the ability of tropomyosin to shift towards the outer domains of actin, which is accompanied by the almost complete depression of troponin’s ability to switch actin monomers off and to reduce the amount of the myosin heads weakly bound to F-actin at a low Ca2+. These changes in the behavior of tropomyosin and the troponin–tropomyosin complex, as well as in the balance of strongly and weakly bound myosin heads in the ATPase cycle may underlie the occurrence of both abnormally high Ca2+-sensitivity and muscle weakness. BDM, an inhibitor of myosin ATPase activity, and W7, a troponin C antagonist, restore the ability of tropomyosin for Ca2+-dependent movement and the ability of the troponin–tropomyosin complex to switch actin monomers off, demonstrating a weakening of the damaging effect of the R90P mutation on muscle contractility. 相似文献
77.
5CrMnMo钢中、小型热锻模具的强韧化热处理 总被引:1,自引:0,他引:1
5CrMnMo钢中、小型热锻模具经强韧化工艺处理后与经常规工艺热处理相比,强韧性、疲劳抗力和使用寿命显著提高,且工艺简单,操作方便,质量稳定。 相似文献
78.
Kinetics of synthesis of Li4Ti5O12 through solid-solid reaction 总被引:1,自引:0,他引:1
CHPU Kuo-Chih QIU Weihua WU Ke ZHANG Guohua 《稀有金属(英文版)》2006,25(5):399-406
1. Introduction The solid-solid reaction used in synthesizing various kinds of electrochemical materials has many advantages, such as simple process, without using solvent, saving energy, friendly to the environment and easy to obtain good quality materials like nano-size materials. Recently, the manufacturing of electrochemistry materials has been paid more atten- tion due to its increasing needs. Therefore it is a natural interest to study the synthesis of electro- chemical materials by usin… 相似文献
79.
高密度钨合金热静液挤压流动粘度的数值计算 总被引:1,自引:0,他引:1
采用粘性流体的运动微分方程分析工作介质在锥模中的挤压流动,通过分析工作介质的粘度对热静液挤压的影响,指出了合理的选择工作介质的成分使得粘度适宜,可以使热静液挤压力最小,而且能够避免挤压件缺陷的产生。挤压介质的粘度是关系到坯料变形流动的润滑性能及挤压变形流动性能的关键。在此基础上,给出了挤压介质的粘度的数学关系式,为热静液挤压工艺奠定重要的理论基础。 相似文献
80.
MoSi2—Mo5Si3复合材料的低温氧化行为 总被引:1,自引:0,他引:1
通过热重分析(TGA)、X射线衍射(XRD)和扫描电镜(SEM)研究了MoSi2-Mo5Si3复合材料的低温氧化行为,指出材料低温氧化时,随Mo5Si3量增多,材料氧化加剧,当Mo5Si3含量超过16%(质量分数)时发生“PEST”现象,所形成的SiO2由于MoS3晶须的大量存在,使其不能均匀连续地分布于材料表面,从而加剧了氧化。 相似文献