全文获取类型
收费全文 | 3776篇 |
免费 | 325篇 |
国内免费 | 213篇 |
出版年
2024年 | 4篇 |
2023年 | 33篇 |
2022年 | 78篇 |
2021年 | 134篇 |
2020年 | 88篇 |
2019年 | 104篇 |
2018年 | 108篇 |
2017年 | 86篇 |
2016年 | 133篇 |
2015年 | 217篇 |
2014年 | 252篇 |
2013年 | 283篇 |
2012年 | 347篇 |
2011年 | 292篇 |
2010年 | 188篇 |
2009年 | 194篇 |
2008年 | 235篇 |
2007年 | 216篇 |
2006年 | 169篇 |
2005年 | 152篇 |
2004年 | 151篇 |
2003年 | 123篇 |
2002年 | 127篇 |
2001年 | 84篇 |
2000年 | 79篇 |
1999年 | 79篇 |
1998年 | 37篇 |
1997年 | 21篇 |
1996年 | 20篇 |
1995年 | 29篇 |
1994年 | 24篇 |
1993年 | 17篇 |
1992年 | 25篇 |
1991年 | 25篇 |
1990年 | 20篇 |
1989年 | 31篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 8篇 |
1973年 | 3篇 |
排序方式: 共有4314条查询结果,搜索用时 31 毫秒
61.
Bin Zhang Chong Luo Yaqian Deng Zhijia Huang Guangmin Zhou Wei Lv Yan‐Bing He Ying Wan Feiyu Kang Quan‐Hong Yang 《Liver Transplantation》2020,10(15)
The lithium–sulfur (Li–S) battery is a next generation high energy density battery, but its practical application is hindered by the poor cycling stability derived from the severe shuttling of lithium polysulfides (LiPSs). Catalysis is a promising way to solve this problem, but the rational design of relevant catalysts is still hard to achieve. This paper reports the WS2–WO3 heterostructures prepared by in situ sulfurization of WO3, and by controlling the sulfurization degree, the structure is controlled, which balances the trapping ability (by WO3) and catalytic activity (by WS2) toward LiPSs. As a result, the WS2–WO3 heterostructures effectively accelerate LiPS conversion and improve sulfur utilization. The Li–S battery with 5 wt% WS2–WO3 heterostructures as additives in the cathode shows an excellent rate performance and good cycling stability, revealing a 0.06% capacity decay each cycle over 500 cycles at 0.5 C. By building an interlayer with such heterostructure‐added graphenes, the battery with a high sulfur loading of 5 mg cm?2 still shows a high capacity retention of 86.1% after 300 cycles at 0.5 C. This work provides a rational way to prepare the metal oxide–sulfide heterostructures with an optimized structure to enhance the performance of Li–S batteries. 相似文献
62.
63.
为提高农作物重大病虫害发生信息自动化、智能化采集能力,全面提升监测预警水平,笔者基于大数据、人工智能和深度学习技术,研发了一款农作物病虫害移动智能采集设备——智宝,主要实现了3个方面的功能:一是病虫害发生信息自动采集上报.通过该产品进行人工拍照,可实现对田间农作物重大病虫害发生图像、发生位置、发生数量、微环境因子等数据的实时采集和上报.二是自动识别计数.基于植保大数据与人工智能技术,通过构建病虫害自动识别系统,可实现重大病虫害精准识别与分析,只要拍摄照片,即可快速、精确地识别病虫害种类,并自动计数、上报到指定的测报系统.三是自动分析判别分级.针对拍摄采集上报的重大病虫害发生信息,系统可在自动识别和计数的基础上,进一步对病虫害发生严重程度进行智能判别分级,甚至根据相关预测模型,对病虫害的发生趋势进行辅助分析预测,提出预测建议.通过2016—2019年组织多地植保机构进行试验改进,该技术产品日趋成熟,有望在未来的农作物病虫害发生信息采集和预测预报工作中推广使用. 相似文献
64.
65.
Wu Ying Jiang Lisha Zhang Lingling Liu Xia Yan Lina Luan Ting Rui Can Mao Zhiyuan Fan Chong Liu Yu Li Ping Zeng Xin 《Mycopathologia》2021,186(2):177-188
Mycopathologia - Vulvovaginal candidiasis (VVC) caused by Candida spp. affects 70–75% of women at least once during their lives. We aim to elucidate the potential mechanism of VVC and... 相似文献
66.
67.
68.
Paek Hyo-Jin Luo Zhao-Bo Choe Hak-Myong Quan Biao-Hu Gao Kai Han Sheng-Zhong Li Zhou-Yan Kang Jin-Dan Yin Xi-Jun 《Transgenic research》2021,30(5):663-674
Transgenic Research - Herein, we investigate the high incidence of umbilical hernia and tippy-toe standing and their underlying changes in gene expression and proliferation in myostatin knockout... 相似文献
69.
Figs have been regarded as keystone plant resources that support diverse tropical vertebrate frugivore communities. Planting or conserving large fig trees, such as stranglers, have therefore been proposed for enhancing urban biodiversity. We compared the diversity and community structure of bird assemblages on strangler figs with non‐fig urban trees as well as between the fruiting and non‐fruiting fig trees in an urban setting in Singapore. The total bird abundance across all the fig trees when in fruit was 4.5‐fold higher than on non‐fig trees and 3.5‐fold higher than when the same fig trees were not fruiting, but only attracted two more species. On individual trees, after accounting for the presence of mistletoes, tree height, the area covered by buildings, road lane density, and the distance to natural vegetation, mean diversity was not different between non‐fig trees and fig trees when they were not in fruit. On the other hand, when fruiting, each fig tree on average had 1.4 more species, 3 more counts of non‐native birds, and 1.6 more counts of insectivorous birds than when not fruiting. There was significant compositional turnover between non‐fig trees and non‐fruiting fig trees, while community dispersion was significantly lower among fig trees in fruit. Our results demonstrate that fig trees provide fruit and non‐fruit resources for birds in an urban landscape but do not necessarily support more diverse total bird assemblages than non‐fig trees. Instead, bird communities on fruiting urban figs would be highly homogeneous and dominated by a few species. Abstract in Malay is available with online material. 相似文献
70.