全文获取类型
收费全文 | 457488篇 |
免费 | 5985篇 |
国内免费 | 2015篇 |
专业分类
电工技术 | 8606篇 |
综合类 | 352篇 |
化学工业 | 67939篇 |
金属工艺 | 18775篇 |
机械仪表 | 15263篇 |
建筑科学 | 9675篇 |
矿业工程 | 2551篇 |
能源动力 | 12846篇 |
轻工业 | 33461篇 |
水利工程 | 4898篇 |
石油天然气 | 9467篇 |
武器工业 | 55篇 |
无线电 | 54296篇 |
一般工业技术 | 94572篇 |
冶金工业 | 84337篇 |
原子能技术 | 11035篇 |
自动化技术 | 37360篇 |
出版年
2022年 | 2928篇 |
2021年 | 4444篇 |
2020年 | 3373篇 |
2019年 | 4292篇 |
2018年 | 7443篇 |
2017年 | 7506篇 |
2016年 | 8060篇 |
2015年 | 4945篇 |
2014年 | 8187篇 |
2013年 | 22548篇 |
2012年 | 13046篇 |
2011年 | 17205篇 |
2010年 | 13819篇 |
2009年 | 15546篇 |
2008年 | 15876篇 |
2007年 | 15612篇 |
2006年 | 13929篇 |
2005年 | 12509篇 |
2004年 | 11838篇 |
2003年 | 11722篇 |
2002年 | 11078篇 |
2001年 | 10984篇 |
2000年 | 10368篇 |
1999年 | 10679篇 |
1998年 | 27096篇 |
1997年 | 18678篇 |
1996年 | 14294篇 |
1995年 | 10669篇 |
1994年 | 9397篇 |
1993年 | 9399篇 |
1992年 | 6803篇 |
1991年 | 6501篇 |
1990年 | 6478篇 |
1989年 | 6133篇 |
1988年 | 5757篇 |
1987年 | 5101篇 |
1986年 | 4980篇 |
1985年 | 5543篇 |
1984年 | 5008篇 |
1983年 | 4574篇 |
1982年 | 4191篇 |
1981年 | 4270篇 |
1980年 | 3959篇 |
1979年 | 3840篇 |
1978年 | 3822篇 |
1977年 | 4369篇 |
1976年 | 5597篇 |
1975年 | 3306篇 |
1974年 | 3102篇 |
1973年 | 3179篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Zavadiuk S.V. Loboda P.I. Soloviova T.O. Trosnikova I.Iu. Karasevska O.P. 《Powder Metallurgy and Metal Ceramics》2020,59(1-2):22-28
Powder Metallurgy and Metal Ceramics - The properties of sintered and heat-treated steels produced from the Catamold 8740 material by powder injection molding were examined. Parts made of the... 相似文献
102.
This paper presents an analytical solution to the non-uniform pressure on thick-walled cylinder. The formulation is based on the linear elasticity theory (plain strain) and stress function method. As an example, the proposed solution is used to model the stress distribution due to non-uniform steel reinforcement corrosion in concrete. The model is formulated considering different scenarios of corrosion pressure distribution. It is validated against the finite element model for different cases of non-uniform pressure distributions. The results show that the corrosion-induced cracks are likely to start just beyond the anodic zone. This is confirmed by the experimental tests on concrete cylinder exposed to non-uniform accelerated corrosion of steel reinforcement. The model can be effectively used to calculate the distribution of corrosion-induced stresses in concrete. 相似文献
103.
The miniaturization has become a key word for advanced integrated circuits over the last few years. It is within this context that the fin field effect tra 相似文献
104.
105.
Niluka M. Dissanayake Kelley M. Current Sherine O. Obare 《International journal of molecular sciences》2015,16(10):23482-23516
In recent years, there has been an increased interest in the design and use of iron oxide materials with nanoscale dimensions for magnetic, catalytic, biomedical, and electronic applications. The increased manufacture and use of iron oxide nanoparticles (IONPs) in consumer products as well as industrial processes is expected to lead to the unintentional release of IONPs into the environment. The impact of IONPs on the environment and on biological species is not well understood but remains a concern due to the increased chemical reactivity of nanoparticles relative to their bulk counterparts. This review article describes the impact of IONPs on cellular genetic components. The mutagenic impact of IONPs may damage an organism’s ability to develop or reproduce. To date, there has been experimental evidence of IONPs having mutagenic interactions on human cell lines including lymphoblastoids, fibroblasts, microvascular endothelial cells, bone marrow cells, lung epithelial cells, alveolar type II like epithelial cells, bronchial fibroblasts, skin epithelial cells, hepatocytes, cerebral endothelial cells, fibrosarcoma cells, breast carcinoma cells, lung carcinoma cells, and cervix carcinoma cells. Other cell lines including the Chinese hamster ovary cells, mouse fibroblast cells, murine fibroblast cells, Mytilus galloprovincialis sperm cells, mice lung cells, murine alveolar macrophages, mice hepatic and renal tissue cells, and vero cells have also shown mutagenic effects upon exposure to IONPs. We further show the influence of IONPs on microorganisms in the presence and absence of dissolved organic carbon. The results shed light on the transformations IONPs undergo in the environment and the nature of the potential mutagenic impact on biological cells. 相似文献
106.
107.
Emma Layton Anna-Marie Fairhurst Sam Griffiths-Jones Richard K. Grencis Ian S. Roberts 《International journal of molecular sciences》2020,21(23)
In eukaryotes, microRNAs (miRNAs) have roles in development, homeostasis, disease and the immune response. Recent work has shown that plant and mammalian miRNAs also mediate cross-kingdom and cross-domain communications. However, these studies remain controversial and are lacking critical mechanistic explanations. Bacteria do not produce miRNAs themselves, and therefore it is unclear how these eukaryotic RNA molecules could function in the bacterial recipient. In this review, we compare and contrast the biogenesis and functions of regulatory RNAs in eukaryotes and bacteria. As a result, we discovered several conserved features and homologous components in these distinct pathways. These findings enabled us to propose novel mechanisms to explain how eukaryotic miRNAs could function in bacteria. Further understanding in this area is necessary to validate the findings of existing studies and could facilitate the use of miRNAs as novel tools for the directed remodelling of the human microbiota. 相似文献
108.
109.
110.