全文获取类型
收费全文 | 718667篇 |
免费 | 16802篇 |
国内免费 | 5860篇 |
专业分类
电工技术 | 17036篇 |
技术理论 | 2篇 |
综合类 | 6228篇 |
化学工业 | 108588篇 |
金属工艺 | 28502篇 |
机械仪表 | 23507篇 |
建筑科学 | 23225篇 |
矿业工程 | 4407篇 |
能源动力 | 18792篇 |
轻工业 | 67206篇 |
水利工程 | 7726篇 |
石油天然气 | 12229篇 |
武器工业 | 703篇 |
无线电 | 88520篇 |
一般工业技术 | 131667篇 |
冶金工业 | 122096篇 |
原子能技术 | 12884篇 |
自动化技术 | 68011篇 |
出版年
2021年 | 7750篇 |
2020年 | 5602篇 |
2019年 | 6093篇 |
2018年 | 9158篇 |
2017年 | 9620篇 |
2016年 | 9772篇 |
2015年 | 8764篇 |
2014年 | 13389篇 |
2013年 | 34096篇 |
2012年 | 21297篇 |
2011年 | 28328篇 |
2010年 | 22811篇 |
2009年 | 24993篇 |
2008年 | 25994篇 |
2007年 | 25897篇 |
2006年 | 23504篇 |
2005年 | 21312篇 |
2004年 | 19222篇 |
2003年 | 18353篇 |
2002年 | 18052篇 |
2001年 | 17732篇 |
2000年 | 16612篇 |
1999年 | 17187篇 |
1998年 | 37189篇 |
1997年 | 27579篇 |
1996年 | 21788篇 |
1995年 | 16826篇 |
1994年 | 14913篇 |
1993年 | 14310篇 |
1992年 | 10841篇 |
1991年 | 10432篇 |
1990年 | 9883篇 |
1989年 | 9549篇 |
1988年 | 9207篇 |
1987年 | 7792篇 |
1986年 | 7746篇 |
1985年 | 9190篇 |
1984年 | 8730篇 |
1983年 | 7709篇 |
1982年 | 7261篇 |
1981年 | 7331篇 |
1980年 | 6950篇 |
1979年 | 6795篇 |
1978年 | 6608篇 |
1977年 | 7816篇 |
1976年 | 10343篇 |
1975年 | 5745篇 |
1974年 | 5491篇 |
1973年 | 5403篇 |
1972年 | 4582篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Chemical and Petroleum Engineering - The processes of separation of impurities of particles of different sizes are analyzed under conditions of irregularity of structural and kinematic parameters... 相似文献
62.
The corrosion mechanisms of T24, T92, VM12, and AISI 304 steels are studied under the influence of NaCl–KCl, NaCl–Na2SO4, and KCl–K2SO4 salt mixtures in a dry air atmosphere at 650°C for 15 days. NaCl–KCl was the most aggressive deposit and AISI 304 stainless steel exhibited the highest corrosion resistance. There was no relation between the Cr content of the ferritic steels and their corrosion resistance in NaCl–KCl. In contrast, the resistance of high-Cr steels was better when exposed to NaCl–Na2SO4 and KCl–K2SO4. The high-Cr and the low-Cr steels were more susceptible to NaCl–Na2SO4 and to KCl–K2SO4, respectively. 相似文献
63.
Cheng-Chin Huang Ching-Yao Yang Chin-Chuan Su Kai-Min Fang Cheng-Chieh Yen Ching-Ting Lin Jui-Min Liu Kuan-I Lee Ya-Wen Chen Shing-Hwa Liu Chun-Fa Huang 《International journal of molecular sciences》2021,22(9)
4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), a major active metabolite of bisphenol A (BPA), is generated in the mammalian liver. Some studies have suggested that MBP exerts greater toxicity than BPA. However, the mechanism underlying MBP-induced pancreatic β-cell cytotoxicity remains largely unclear. This study demonstrated the cytotoxicity of MBP in pancreatic β-cells and elucidated the cellular mechanism involved in MBP-induced β-cell death. Our results showed that MBP exposure significantly reduced cell viability, caused insulin secretion dysfunction, and induced apoptotic events including increased caspase-3 activity and the expression of active forms of caspase-3/-7/-9 and PARP protein. In addition, MBP triggered endoplasmic reticulum (ER) stress, as indicated by the upregulation of GRP 78, CHOP, and cleaved caspase-12 proteins. Pretreatment with 4-phenylbutyric acid (4-PBA; a pharmacological inhibitor of ER stress) markedly reversed MBP-induced ER stress and apoptosis-related signals. Furthermore, exposure to MBP significantly induced the protein phosphorylation of JNK and AMP-activated protein kinase (AMPK)α. Pretreatment of β-cells with pharmacological inhibitors for JNK (SP600125) and AMPK (compound C), respectively, effectively abrogated the MBP-induced apoptosis-related signals. Both JNK and AMPK inhibitors also suppressed the MBP-induced activation of JNK and AMPKα and of each other. In conclusion, these findings suggest that MBP exposure exerts cytotoxicity on β-cells via the interdependent activation of JNK and AMPKα, which regulates the downstream apoptotic signaling pathway. 相似文献
64.
The Fe/C/SiCN composite ceramics were synthesized by polymer-derived method to obtain the integration of structure and functions. The electromagnetic waves (EMW) absorption properties at X and Ku bands were investigated. The addition of nano-sized Fe particles improved the magnetic loss and impedance matching, and the carbon nanotubes generated by the iron in-situ catalysis increased the internal relaxation polarization and interfacial polarization, which together improved the EMW absorption properties significantly. In particular, the Fe/C/SiCN-9 showed the optimum reflection loss (RL) of ?31.06 dB at 10.03 GHz with an effective absorption bandwidth (EAB, RL < ?10 dB) of 3.03 GHz at 2.51 mm, indicating the excellent EMW absorption properties of Fe/C/SiCN composite ceramics. 相似文献
65.
Nitsa Buaron Antonella Mangraviti Francesco Volpin Ann Liu Mariangela Pedone Eric Sankey Dina Aranovich Itay Adar Fausto J. Rodriguez Abraham Nyska Riki Goldbart Tamar Traitel Henry Brem Betty Tyler Joseph Kost 《Advanced functional materials》2021,31(44):2100643
Treating neuroinflammation-related injuries and disorders through manipulation of neuroinflammation functions is being heralded as a new therapeutic strategy. In this study, a novel pectic galactan (PG) polysaccharide based gene therapy approach is developed for targeting reactive gliosis in neuroinflammation. Galectin-3 (Gal-3) is a cell protein with a high affinity to β-galactoside sugars and is highly expressed in reactive gliosis. Since PG carries galactans, it can target reactive gliosis via specific carbohydrate interaction between galactan and Gal-3 on the cell membrane, and therefore can be utilized as a carrier for delivering genes to these cells. The carrier is synthesized by modifying quaternary ammonium groups on the PG. The resulting quaternized PG (QPG) is found to form complexes with plasmid DNA with a mean diameter of 100 nm and have the characteristics required for targeted gene therapy. The complexes efficiently condense large amounts of plasmid per particle and successfully bind to Gal-3. The in vivo study shows that the complexes are biocompatible and safe for administration and can selectively transfect reactive glial cells of an induced cortical lesion. The results confirm that this PG-based delivery system is a promising platform for targeting Gal-3 overexpressing neuroinflammation cells for treating neuroinflammation-related injuries and neurodegenerative diseases. 相似文献
66.
67.
68.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文
69.
尕斯库勒油田E13油藏已经进入高含水时期,储采失衡加剧,综合含水率达到了80%以上,原油产量下降,经济效益变差。为了提高油藏原油采出程度、改善油藏开发效果,调研了国内外减氧空气驱的机理研究以及现场试验的资料,建立了以油藏真实孔渗饱数据为基础的一维条形地层机理模型,并选取该油藏Y12-27井组进行了减氧空气驱可行性验证。研究表明:纵向顶部减氧空气驱驱油效果优于水驱和氮气驱;驱替压力对原油采出程度影响不大;注水转注气可以提高原油采出程度;对于减氧空气驱,由于低温氧化反应的作用,氧气浓度对原油采出程度有一定影响,但比较微弱,其中,氧气浓度为10%时,驱替结束采出程度最高;尕斯库勒油田E13油藏属于注水开发“双高”油藏,适用于减氧空气驱;对于该油藏Y12-27井组,顶部减氧空气驱驱油效果好于水驱和氮气驱,建议氧气浓度超过10%时采取关井等措施。 相似文献
70.