全文获取类型
收费全文 | 5702篇 |
免费 | 431篇 |
国内免费 | 497篇 |
出版年
2024年 | 10篇 |
2023年 | 75篇 |
2022年 | 174篇 |
2021年 | 322篇 |
2020年 | 224篇 |
2019年 | 275篇 |
2018年 | 287篇 |
2017年 | 187篇 |
2016年 | 247篇 |
2015年 | 329篇 |
2014年 | 404篇 |
2013年 | 429篇 |
2012年 | 502篇 |
2011年 | 436篇 |
2010年 | 293篇 |
2009年 | 279篇 |
2008年 | 297篇 |
2007年 | 271篇 |
2006年 | 218篇 |
2005年 | 162篇 |
2004年 | 170篇 |
2003年 | 148篇 |
2002年 | 101篇 |
2001年 | 90篇 |
2000年 | 83篇 |
1999年 | 85篇 |
1998年 | 60篇 |
1997年 | 54篇 |
1996年 | 66篇 |
1995年 | 57篇 |
1994年 | 33篇 |
1993年 | 39篇 |
1992年 | 36篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 31篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1966年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有6630条查询结果,搜索用时 15 毫秒
101.
选取长白山岳桦林中的岳桦-蟹甲草群落(Comm.Betula ermanii-Parasenecio forrestii)、岳桦-藜芦群落(Comm.Betula ermanii-Veratrum nigrum)和岳桦-小叶章群落(Comm.Betula ermanii-Deyeuxia purpurea)开展野外模拟氮沉降实验,采用野外原位模拟实验方法,设置对照(0 kg·hm-2·a-1)、低氮(30 kg·hm-2·a-1)、中氮(50 kg·hm-2·a-1)和高氮(100 kg·hm-2·a-1)4个氮处理水平,测定草本植物生长状况和土壤肥力,研究岳桦林下草本层植物和土壤肥力对氮沉降的短期响应。结果显示:(1)岳桦林下草本植物随氮沉降量的增加而加速生长,小叶章对氮沉降的响应较为敏感,藜芦次之,蟹甲草最弱;(2)氮添加造成林下土壤肥力发生变化,有机质含量下降,特别是岳桦-小叶章群落下的土壤有机质含量下降最明显;土壤总氮和速效氮含量增大,岳桦-蟹甲草群落下的土壤总氮和速效氮增加最多;土壤总磷和速效磷含量减小,岳桦-小叶章群落下的土壤总磷和速效磷含量的减少最多。本研究结果表明氮添加在短期内会促进长白山岳桦林下草本植物生长,尤其是小叶章的生长,加快土壤有机质的分解和磷的释放,逐步改变土壤肥力并反馈给植物,促使其进一步变化。 相似文献
102.
Hydrangea bretschneideri Dipp is a highly popular ornamental plant for garden decoration. Genetic engineering
technology has been successfully used in many plant species, but it is limited in Hydrangea. Here we established
an efficient regeneration system by using stem segments as explants for the first time. In our study, the plant
growth regulators (PGRs) were evaluated at the different regeneration processes, including axillary shoots regeneration and root induction. We found that the optimal concentration for axillary buds’ induction was 2.0 mgL−1
6-BA and 0.5 mgL−1
1 IAA, its highest induction rate was 70%. Moreover, the highest axillary shoots proliferation
coefficient was 10.7 on the Murashige and Skoog (MS) medium with 2.0 mgL−1 6-benzyladenine (BA), 0.2 mgL−1
indole-3-butyric acid (IBA), and 1.0 mgL−1 gibberellin A3 (GA3). The highest frequency of root induction was
80.0 ± 0.06% by culturing the elongated shoots in 1/2 MS medium containing 0.1 mgL−1 IBA. In summary,
our study will provide an effective technology for large-scale propagation and important pathway for promoting
the popularization and application of Hydrangea bretschneideri Dipp. 相似文献
103.
Tian Xin-Yue He Dong-Dong Bai Shuang Zeng Wen-Zhi Wang Zheng Wang Mo Wu Liang-Quan Chen Zhi-Chang 《Plant and Soil》2021,460(1-2):1-30
Plant and Soil - Phytoremediation of soil contaminated by trace elements is a technology using plants and microorganisms to sequester, inactivate, or extract contaminants from the soil. The... 相似文献
104.
Yunpeng Bai Wendong Huang Yaocai Li Changchun Lai Sumei Huang Guangwen Wang Yuemei He Linhui Hu Chunbo Chen 《Bioscience reports》2021,41(3)
Background: The pandemic of novel coronavirus disease 2019 (COVID-19) has become a serious public health crisis worldwide. The symptoms of COVID-19 vary from mild to severe among different age groups, but the physiological changes related to COVID-19 are barely understood.Methods: In the present study, a high-resolution mass spectrometry (HRMS)-based lipidomic strategy was used to characterize the endogenous plasma lipids for cured COVID-19 patients with different ages and symptoms. These patients were further divided into two groups: those with severe symptoms or who were elderly and relatively young patients with mild symptoms. In addition, automated lipidomic identification and alignment was conducted by LipidSearch software. Multivariate and univariate analyses were used for differential comparison.Results: Nearly 500 lipid compounds were identified in each cured COVID-19 group through LipidSearch software. At the level of lipid subclasses, patients with severe symptoms or elderly patients displayed dramatic changes in plasma lipidomic alterations, such as increased triglycerides and decreased cholesteryl esters (ChE). Some of these differential lipids might also have essential biological functions. Furthermore, the differential analysis of plasma lipids among groups was performed to provide potential prognostic indicators, and the change in signaling pathways.Conclusions: Dyslipidemia was observed in cured COVID-19 patients due to the viral infection and medical treatment, and the discharged patients should continue to undergo consolidation therapy. This work provides valuable knowledge about plasma lipid markers and potential therapeutic targets of COVID-19 and essential resources for further research on the pathogenesis of COVID-19. 相似文献
105.
106.
Liu Xinrong Liu Shuya Tang Yong Pu Zhengjia Xiao Hong Gao Jieying Yin Qi Jia Yan Bai Qunhua 《Neurochemical research》2021,46(6):1514-1539
Neurochemical Research - Gut microbial dysbiosis and alteration of gut microbiota composition in Parkinson's disease (PD) have been increasingly reported, no recognized therapies are available... 相似文献
107.
Chen Yen-Chi Wang I-Jen Cheng Chih-Ching Wu Yu-Chiao Bai Chun-Hsuan Yu Kuo-Pin 《Aerobiologia》2021,37(2):243-252
Aerobiologia - The liquid impingers can be used for sampling of viral aerosols, such as COVID-19 virus, influenza, and measles. However, the lowest cutoff diameter of commercially available liquid... 相似文献
108.
109.
110.