全文获取类型
收费全文 | 378863篇 |
免费 | 44706篇 |
国内免费 | 30949篇 |
专业分类
电工技术 | 33849篇 |
技术理论 | 1篇 |
综合类 | 40999篇 |
化学工业 | 46793篇 |
金属工艺 | 26853篇 |
机械仪表 | 26458篇 |
建筑科学 | 28241篇 |
矿业工程 | 16663篇 |
能源动力 | 10006篇 |
轻工业 | 43225篇 |
水利工程 | 12588篇 |
石油天然气 | 13734篇 |
武器工业 | 5615篇 |
无线电 | 39364篇 |
一般工业技术 | 31115篇 |
冶金工业 | 17016篇 |
原子能技术 | 6553篇 |
自动化技术 | 55445篇 |
出版年
2024年 | 2402篇 |
2023年 | 6514篇 |
2022年 | 15114篇 |
2021年 | 19449篇 |
2020年 | 13688篇 |
2019年 | 9566篇 |
2018年 | 10196篇 |
2017年 | 12171篇 |
2016年 | 10710篇 |
2015年 | 16992篇 |
2014年 | 21420篇 |
2013年 | 25339篇 |
2012年 | 31490篇 |
2011年 | 33139篇 |
2010年 | 31034篇 |
2009年 | 29570篇 |
2008年 | 30802篇 |
2007年 | 29804篇 |
2006年 | 25839篇 |
2005年 | 21288篇 |
2004年 | 15115篇 |
2003年 | 9970篇 |
2002年 | 9200篇 |
2001年 | 8098篇 |
2000年 | 6567篇 |
1999年 | 2737篇 |
1998年 | 1077篇 |
1997年 | 845篇 |
1996年 | 790篇 |
1995年 | 579篇 |
1994年 | 458篇 |
1993年 | 389篇 |
1992年 | 354篇 |
1991年 | 250篇 |
1990年 | 236篇 |
1989年 | 208篇 |
1988年 | 169篇 |
1987年 | 114篇 |
1986年 | 97篇 |
1985年 | 61篇 |
1984年 | 65篇 |
1983年 | 57篇 |
1982年 | 68篇 |
1981年 | 75篇 |
1980年 | 112篇 |
1979年 | 83篇 |
1976年 | 10篇 |
1965年 | 13篇 |
1959年 | 70篇 |
1951年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
针对基站柜式空调耗电量大的问题,创造性地使用基站分布式冷却的方式,达到精确送风,节能高效的目的.在应用实践中检验了分布式冷却系统实际节能量和应用效果,总结出分布式冷却系统应用场景和范围,为更大范围推广应用DCS分布式冷却系统提供实践依据. 相似文献
42.
43.
The fracture behaviour and morphologies of high-strength boron steel were investigated at different temperatures at a constant strain rate of 0.1 s-1 based on isothermal tensile tests. Fracture mechanisms were also analyzed based on the relationship between microstructure transformation and continuous cooling transformation(CCT) curves. It is found that 1) fractures of the investigated steel at high temperatures are dimple fractures; 2) the deformation of high-strength boron steel at high temperatures accelerates diffusion transformations; thus, to obtain full martensite, a higher cooling rate is needed; and 3) the investigated steel has the best plasticity when the deformation temperature is 750 °C. 相似文献
44.
Xuejing Lin Zhangxiao Peng Changqing Su 《International journal of molecular sciences》2015,16(5):10888-10906
Costunolide (CE) and dehydrocostuslactone (DE) are derived from many species of medicinal plants, such as Saussurea lappa Decne and Laurus nobilis L. They have been reported for their wide spectrum of biological effects, including anti-inflammatory, anticancer, antiviral, antimicrobial, antifungal, antioxidant, antidiabetic, antiulcer, and anthelmintic activities. In recent years, they have caused extensive interest in researchers due to their potential anti-cancer activities for various types of cancer, and their anti-cancer mechanisms, including causing cell cycle arrest, inducing apoptosis and differentiation, promoting the aggregation of microtubule protein, inhibiting the activity of telomerase, inhibiting metastasis and invasion, reversing multidrug resistance, restraining angiogenesis has been studied. This review will summarize anti-cancer activities and associated molecular mechanisms of these two compounds for the purpose of promoting their research and application. 相似文献
45.
为提高电压跌落条件下双馈风电机组的运行稳定性,介绍了crowbar与chopper共同配合作用的低电压穿越技术,并从提高crowbar阻值整定上限这一角度通过理论分析与仿真验证说明了crowbar与chopper配合作用的优势。提出低电压穿越过程中机侧变流器的无扰切换控制方法,通过仿真验证了这种方法可以大大减少crowbar投切次数与低穿过渡时间,且控制简单可行。 相似文献
46.
47.
48.
Rapid synthesis of silver nanowires(Ag NWs) with high quality and a broad processing window is challenging because of the low selectivity of the formation of multiply twinned particles at the nucleation stage for subsequent Ag NWs growth.Herein we report a systematic study of the water-involved heterogeneous nucleation of Ag NWs with high rate(less than 20 min) in a simple and scalable preparation method.Using glycerol as a reducing agent and a solvent with a high boiling point,the reaction is rapidly heated to 210 ℃ in air to synthesize Ag NWs with a very high yield in gram level.It is noted that the addition of a small dose of water plays a key role for obtaining highly pure Ag NWs in high yield,and the optimal water/glycerol ratio is0.25%.After investigating a series of forming factors including reaction temperature and dose of catalysts,the formation kinetics and mechanism of the Ag NWs are proposed.Compared to other preparation methods,our strategy is simple and reproducible.These Ag NWs show a strong Raman enhancement effect for organic molecules on their surface. 相似文献
49.
In vivo Kinetic Biodistribution of Nano‐Sized Outer Membrane Vesicles Derived from Bacteria
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Su Chul Jang Sae Rom Kim Yae Jin Yoon Kyong‐Su Park Ji Hyun Kim Jaewook Lee Oh Youn Kim Eun‐Jeong Choi Dae‐Kyum Kim Dong‐Sic Choi Yoon‐Keun Kim Jaesung Park Dolores Di Vizio Yong Song Gho 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(4):456-461
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo. 相似文献
50.