全文获取类型
收费全文 | 477161篇 |
免费 | 5930篇 |
国内免费 | 1694篇 |
专业分类
电工技术 | 8343篇 |
综合类 | 765篇 |
化学工业 | 73281篇 |
金属工艺 | 18688篇 |
机械仪表 | 14501篇 |
建筑科学 | 11095篇 |
矿业工程 | 2720篇 |
能源动力 | 11361篇 |
轻工业 | 43026篇 |
水利工程 | 5089篇 |
石油天然气 | 9817篇 |
武器工业 | 74篇 |
无线电 | 53347篇 |
一般工业技术 | 92749篇 |
冶金工业 | 89453篇 |
原子能技术 | 11873篇 |
自动化技术 | 38603篇 |
出版年
2021年 | 3909篇 |
2019年 | 3732篇 |
2018年 | 6383篇 |
2017年 | 6401篇 |
2016年 | 6825篇 |
2015年 | 4304篇 |
2014年 | 7437篇 |
2013年 | 20576篇 |
2012年 | 12021篇 |
2011年 | 16549篇 |
2010年 | 12914篇 |
2009年 | 14673篇 |
2008年 | 15262篇 |
2007年 | 15372篇 |
2006年 | 13454篇 |
2005年 | 12188篇 |
2004年 | 11975篇 |
2003年 | 11568篇 |
2002年 | 11401篇 |
2001年 | 11340篇 |
2000年 | 10846篇 |
1999年 | 11125篇 |
1998年 | 26543篇 |
1997年 | 18926篇 |
1996年 | 14549篇 |
1995年 | 11280篇 |
1994年 | 9989篇 |
1993年 | 9879篇 |
1992年 | 7420篇 |
1991年 | 6965篇 |
1990年 | 7071篇 |
1989年 | 6959篇 |
1988年 | 6504篇 |
1987年 | 5818篇 |
1986年 | 5851篇 |
1985年 | 6610篇 |
1984年 | 6168篇 |
1983年 | 5682篇 |
1982年 | 5313篇 |
1981年 | 5445篇 |
1980年 | 5320篇 |
1979年 | 5052篇 |
1978年 | 5094篇 |
1977年 | 5654篇 |
1976年 | 7382篇 |
1975年 | 4407篇 |
1974年 | 4236篇 |
1973年 | 4352篇 |
1972年 | 3691篇 |
1971年 | 3347篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state.... 相似文献
3.
4.
Muniyandi Kasipandi Jagadeesan Gayathri George Blassan P. Manoharan Ashwini Lydia Nataraj Gayathri Abrahamse Heidi Thangaraj Parimelazhagan 《Food science and biotechnology》2022,31(13):1717-1728
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and... 相似文献
5.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an... 相似文献
6.
Karimi Bayan Chang Yu-Cheng Pekola Jukka P. 《Journal of Low Temperature Physics》2022,207(3-4):220-225
We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.
相似文献7.
Julio E. Trevino Swati Mohan Alexandra E. Salinas Emilia Cueva Karen Lozano 《应用聚合物科学杂志》2021,138(28):50665
This study presents the development and characterization of PVDF-conjugated polymer nanofiber-based systems. Five different conducting polymers (CPs) were synthesized successfully and used to create the nanofiber systems. The CPs used are polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polyanthranilic acid (PANA), and polycarbazole (PCZ). Nanofiber systems were produced utilizing the Forcespinning® technique. The nanofiber systems were developed by mechanical stretching. No electrical field or post-process poling was used in the nanofiber systems. The morphology, structure, electrochemical and piezoelectric performance was characterized. All of the nanofiber PVDF/CP systems displayed higher piezoelectric performance than the fine fiber PVDF systems. The PVDF/PPY nanofiber system displays the highest piezoelectric performance of 15.56 V. The piezoelectric performance of the PVDF/CP nanofiber systems favors potential for an attractive source of energy where highly flexible membranes could be used in power actuators, sensors and portable, and wireless devices to mention some. 相似文献
8.
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
9.
Seredin P. V. Radam Ali Obaid Goloshchapov D. L. Len’shin A. S. Buylov N. S. Barkov K. A. Nesterov D. N. Mizerov A. M. Timoshnev S. N. Nikitina E. V. Arsentyev I. N. Sharafidinov Sh. Kukushkin S. A. Kasatkin I. A. 《Semiconductors》2022,56(4):253-258
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid... 相似文献
10.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献