全文获取类型
收费全文 | 87033篇 |
免费 | 6897篇 |
国内免费 | 3552篇 |
学科分类
工业技术 | 97482篇 |
出版年
2024年 | 395篇 |
2023年 | 1502篇 |
2022年 | 2421篇 |
2021年 | 3514篇 |
2020年 | 2654篇 |
2019年 | 2191篇 |
2018年 | 2464篇 |
2017年 | 2885篇 |
2016年 | 2592篇 |
2015年 | 3359篇 |
2014年 | 4325篇 |
2013年 | 5321篇 |
2012年 | 5421篇 |
2011年 | 5935篇 |
2010年 | 5158篇 |
2009年 | 4845篇 |
2008年 | 4821篇 |
2007年 | 4653篇 |
2006年 | 4573篇 |
2005年 | 3946篇 |
2004年 | 2742篇 |
2003年 | 2367篇 |
2002年 | 2333篇 |
2001年 | 2020篇 |
2000年 | 2039篇 |
1999年 | 2235篇 |
1998年 | 1907篇 |
1997年 | 1635篇 |
1996年 | 1569篇 |
1995年 | 1207篇 |
1994年 | 1035篇 |
1993年 | 707篇 |
1992年 | 605篇 |
1991年 | 451篇 |
1990年 | 363篇 |
1989年 | 301篇 |
1988年 | 247篇 |
1987年 | 162篇 |
1986年 | 139篇 |
1985年 | 92篇 |
1984年 | 84篇 |
1983年 | 57篇 |
1982年 | 61篇 |
1981年 | 37篇 |
1980年 | 26篇 |
1979年 | 17篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1973年 | 7篇 |
1970年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
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
4.
In vivo Kinetic Biodistribution of Nano‐Sized Outer Membrane Vesicles Derived from Bacteria 下载免费PDF全文
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
5.
在分析单一MU(Most Uncertainty)采样缺陷的基础上,提出一种"全局最优搜寻"方法 GOS(Global Optimal Search),并结合MU共同完成查询选择。GOS+MU方法中,GOS着眼全局寻找目标,在应用环境能提供的训练样本数量有限、分类器受训不充分时,该方法选择的对象学习价值高,能快速推进分类器学习进程;MU则能够在GOS采样失效情形下,利用分类器当前训练成果,选择查询不确定性最强的样本补充训练集。通过对网络商品的用户评论进行分类仿真,并比较其他采样学习方法的效果,证明了GOS+MU方法在压缩学习成本、提高训练效率方面的有效性。 相似文献
6.
7.
8.
9.
10.