全文获取类型
收费全文 | 769606篇 |
免费 | 10710篇 |
国内免费 | 2178篇 |
专业分类
电工技术 | 14539篇 |
综合类 | 890篇 |
化学工业 | 119547篇 |
金属工艺 | 32758篇 |
机械仪表 | 24270篇 |
建筑科学 | 18068篇 |
矿业工程 | 4822篇 |
能源动力 | 19399篇 |
轻工业 | 65643篇 |
水利工程 | 8461篇 |
石油天然气 | 16030篇 |
武器工业 | 52篇 |
无线电 | 84452篇 |
一般工业技术 | 153030篇 |
冶金工业 | 139494篇 |
原子能技术 | 17517篇 |
自动化技术 | 63522篇 |
出版年
2021年 | 7030篇 |
2020年 | 5205篇 |
2019年 | 6610篇 |
2018年 | 11496篇 |
2017年 | 11559篇 |
2016年 | 12290篇 |
2015年 | 8071篇 |
2014年 | 13220篇 |
2013年 | 35529篇 |
2012年 | 20590篇 |
2011年 | 27681篇 |
2010年 | 22354篇 |
2009年 | 24753篇 |
2008年 | 25522篇 |
2007年 | 25267篇 |
2006年 | 22148篇 |
2005年 | 20012篇 |
2004年 | 18986篇 |
2003年 | 18734篇 |
2002年 | 18264篇 |
2001年 | 17828篇 |
2000年 | 16888篇 |
1999年 | 17054篇 |
1998年 | 41384篇 |
1997年 | 29725篇 |
1996年 | 23029篇 |
1995年 | 17478篇 |
1994年 | 15719篇 |
1993年 | 15285篇 |
1992年 | 11543篇 |
1991年 | 11263篇 |
1990年 | 10814篇 |
1989年 | 10562篇 |
1988年 | 10243篇 |
1987年 | 9112篇 |
1986年 | 8898篇 |
1985年 | 10247篇 |
1984年 | 9252篇 |
1983年 | 8701篇 |
1982年 | 7914篇 |
1981年 | 8103篇 |
1980年 | 7741篇 |
1979年 | 7625篇 |
1978年 | 7523篇 |
1977年 | 8636篇 |
1976年 | 11536篇 |
1975年 | 6719篇 |
1974年 | 6427篇 |
1973年 | 6499篇 |
1972年 | 5555篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
11.
12.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
13.
Kathleen T. Lauser Amy L. Rueter Michelle A. Calabrese 《American Institute of Chemical Engineers》2022,68(12):e17850
While protein medications are promising for treatment of cancer and autoimmune diseases, challenges persist in terms of development and injection stability of high-concentration formulations. Here, the extensional flow properties of protein-excipient solutions are examined via dripping-onto-substrate extensional rheology, using a model ovalbumin (OVA) protein and biocompatible excipients polysorbate 20 (PS20) and 80 (PS80). Despite similar PS structures, differences in extensional flow are observed based on PS identity in two regimes: at moderate total concentrations where surface tension differences drive changes in extensional flow behavior, and at small PS:OVA ratios, which impact the onset of weakly elastic flow behavior. Undesirable elasticity is observed in ultra-concentrated formulations, independent of PS identity; higher PS contents are required to observe these effects than in analogous polymeric excipient solutions. These studies reveal novel extensional flow behaviors in protein-excipient solutions, and provide a straightforward methodology for assessing the extensional flow stability of new protein-excipient formulations. 相似文献
14.
Moghadam Seyedeh Hadis Ashofteh Parisa-Sadat Loáiciga Hugo A. 《Water Resources Management》2022,36(9):3181-3205
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in... 相似文献
15.
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
16.
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
17.
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
18.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the... 相似文献
19.
Automation and Remote Control - A linear-quadratic positional differential game of three persons is considered. Coefficient criteria are established under which there is no Nash equilibrium... 相似文献
20.
Optimization and Engineering - 相似文献