全文获取类型
收费全文 | 449474篇 |
免费 | 6491篇 |
国内免费 | 1826篇 |
专业分类
电工技术 | 8319篇 |
综合类 | 1013篇 |
化学工业 | 64770篇 |
金属工艺 | 18137篇 |
机械仪表 | 13093篇 |
建筑科学 | 11266篇 |
矿业工程 | 2109篇 |
能源动力 | 11017篇 |
轻工业 | 39885篇 |
水利工程 | 4387篇 |
石油天然气 | 5276篇 |
武器工业 | 15篇 |
无线电 | 52048篇 |
一般工业技术 | 82148篇 |
冶金工业 | 97343篇 |
原子能技术 | 8533篇 |
自动化技术 | 38432篇 |
出版年
2021年 | 3093篇 |
2019年 | 2874篇 |
2018年 | 5057篇 |
2017年 | 5195篇 |
2016年 | 5915篇 |
2015年 | 4210篇 |
2014年 | 6227篇 |
2013年 | 18925篇 |
2012年 | 11604篇 |
2011年 | 15864篇 |
2010年 | 11597篇 |
2009年 | 13024篇 |
2008年 | 13545篇 |
2007年 | 13661篇 |
2006年 | 12202篇 |
2005年 | 13961篇 |
2004年 | 12830篇 |
2003年 | 12349篇 |
2002年 | 10866篇 |
2001年 | 10980篇 |
2000年 | 9902篇 |
1999年 | 10852篇 |
1998年 | 30212篇 |
1997年 | 21023篇 |
1996年 | 16069篇 |
1995年 | 11643篇 |
1994年 | 10261篇 |
1993年 | 9989篇 |
1992年 | 6981篇 |
1991年 | 6839篇 |
1990年 | 6298篇 |
1989年 | 6286篇 |
1988年 | 6104篇 |
1987年 | 5152篇 |
1986年 | 5035篇 |
1985年 | 5903篇 |
1984年 | 5331篇 |
1983年 | 4922篇 |
1982年 | 4511篇 |
1981年 | 4688篇 |
1980年 | 4419篇 |
1979年 | 4215篇 |
1978年 | 4234篇 |
1977年 | 5410篇 |
1976年 | 8016篇 |
1975年 | 3652篇 |
1974年 | 3436篇 |
1973年 | 3455篇 |
1972年 | 2818篇 |
1971年 | 2584篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Prof. Andrea Baier Dr. Anne Kokel Dr. William Horton Ewa Gizińska Dr. Garima Pandey Prof. Ryszard Szyszka Prof. Béla Török Prof. Marianna Török 《ChemMedChem》2021,16(12):1927-1932
A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays. 相似文献
5.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration. 相似文献
6.
Wireless Personal Communications - Besides anti-malware usage for the eradication of malicious attacks, researchers have developed epidemic models in order to gain more insights into the spread... 相似文献
7.
A. Nakano T. Shimazaki M. Sekiya H. Shiozawa K. Ohtsuka A. Aoyagi T. Iwakiri Z. Mikami M. Sato Y. Sugino K. Kinoshita T. Matsuoka T. Imamura Y. Takayama K. Yamamoto 《International Journal of Hydrogen Energy》2021,46(29):15649-15659
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa. 相似文献
8.
Abulyazied Dalia E. Alturki Asma M. Youness Rasha A. Abomostafa H. M. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):4077-4092
Journal of Inorganic and Organometallic Polymers and Materials - In this work, a borosilicate glass sample (5SiO2–45B2O3–20Na2O–25CaO–5Ag2O) was added to nano-sized... 相似文献
9.
Chemical engineering systems often involve a functional porous medium, such as in catalyzed reactive flows, fluid purifiers, and chromatographic separations. Ideally, the flow rates throughout the porous medium are uniform, and all portions of the medium contribute efficiently to its function. The permeability is a property of a porous medium that depends on pore geometry and relates flow rate to pressure drop. Additive manufacturing techniques raise the possibilities that permeability can be arbitrarily specified in three dimensions, and that a broader range of permeabilities can be achieved than by traditional manufacturing methods. Using numerical optimization methods, we show that designs with spatially varying permeability can achieve greater flow uniformity than designs with uniform permeability. We consider geometries involving hemispherical regions that distribute flow, as in many glass chromatography columns. By several measures, significant improvements in flow uniformity can be obtained by modifying permeability only near the inlet and outlet. 相似文献
10.
Dr. Thomas Le Bihan Dr. Cathryn H. S. Driver Dr. Thomas Ebenhan Dr. Nathalie Le Bris Dr. Jan Rijn Zeevaart Prof. Dr. Raphaël Tripier 《ChemMedChem》2021,16(5):809-821
An improved glucose-chelator-albumin bioconjugate (GluCAB) derivative, GluCAB-2Mal, has been synthesized and studied for in vivo 64Cu-PET/CT imaging in breast cancer mice models together with its first-generation analogue GluCAB-1Mal. The radioligand works on the principle of tumor targeting through the enhanced permeability and retention (EPR) effect with a supportive role played by glucose metabolism. [64Cu]Cu-GluCAB-2Mal (99 % RCP) exhibited high serum stability with immediate binding to serum proteins. In vivo experiments for comparison between tumor targeting of [64Cu]Cu-GluCAB-2Mal and previous-generation [64Cu]Cu-GluCAB-1Mal encompassed microPET/CT imaging and biodistribution analysis in an allograft E0771 breast cancer mouse model. Tumor uptake of [64Cu]Cu-GluCAB-2Mal was clearly evident with twice as much accumulation as compared to its predecessor and a tumor/muscle ratio of up to 5 after 24 h. Further comparison indicated a decrease in liver accumulation for [64Cu]Cu-Glu-CAB-2Mal. 相似文献