全文获取类型
收费全文 | 4827篇 |
免费 | 510篇 |
国内免费 | 886篇 |
专业分类
6223篇 |
出版年
2024年 | 34篇 |
2023年 | 148篇 |
2022年 | 195篇 |
2021年 | 241篇 |
2020年 | 267篇 |
2019年 | 274篇 |
2018年 | 241篇 |
2017年 | 248篇 |
2016年 | 278篇 |
2015年 | 253篇 |
2014年 | 312篇 |
2013年 | 389篇 |
2012年 | 231篇 |
2011年 | 336篇 |
2010年 | 182篇 |
2009年 | 264篇 |
2008年 | 234篇 |
2007年 | 239篇 |
2006年 | 207篇 |
2005年 | 173篇 |
2004年 | 172篇 |
2003年 | 136篇 |
2002年 | 133篇 |
2001年 | 112篇 |
2000年 | 82篇 |
1999年 | 67篇 |
1998年 | 66篇 |
1997年 | 64篇 |
1996年 | 66篇 |
1995年 | 70篇 |
1994年 | 59篇 |
1993年 | 58篇 |
1992年 | 34篇 |
1991年 | 42篇 |
1990年 | 33篇 |
1989年 | 31篇 |
1988年 | 25篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 23篇 |
1984年 | 29篇 |
1983年 | 24篇 |
1982年 | 31篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1973年 | 12篇 |
排序方式: 共有6223条查询结果,搜索用时 15 毫秒
121.
磁场对羊草过氧化物酶的激活效应及同工酶分析 总被引:17,自引:0,他引:17
利用外磁场处理羊草种子,并将羊草进行盐(NaCl)碱(Na2CO3)混合胁迫处理,结果表明,磁场处理不仅促进了羊草的生长,而且提高了羊草的抗盐碱性。磁场使羊草过氧化物酶(POD)活性提高,并且诱发了一条新的同工酶带。根据羊草的长势及POD活性分析,确定羊草最佳的磁处理参数是300mT处理,其次是200mT。 相似文献
122.
Abram F Enright AM O'Reilly J Botting CH Collins G O'Flaherty V 《Journal of applied microbiology》2011,110(6):1550-1560
Aims: The objective of this work was to provide functional evidence of key metabolic pathways important for anaerobic digestion processes through the identification of highly expressed proteins in a mixed anaerobic microbial consortium. Methods and Results: The microbial communities from an anaerobic industrial‐like wastewater treatment bioreactor were characterized using phylogenetic analyses and metaproteomics. Clone libraries indicated that the bacterial community in the bioreactor was diverse while the archaeal population was mainly composed of Methanocorpusculum‐like (76%) micro‐organisms. Three hundred and eighty‐eight reproducible protein spots were obtained on 2‐D gels, of which 70 were excised and 33 were identified. The putative functions of the proteins detected in the anaerobic bioreactor were related to cellular processes, including methanogenesis from CO2 and acetate, glycolysis and the pentose phosphate pathway. Metaproteomics also indicated, by protein assignment, the presence of specific micro‐organisms in the bioreactor. However, only a limited overlap was observed between the phylogenetic and metaproteomic analyses. Conclusions: This study provides some direct evidence of the microbial activities taking place during anaerobic digestion. Significance and Impact of Study: This study demonstrates metaproteomics as a useful tool to uncover key biochemical pathways underpinning specific anaerobic bioprocesses. 相似文献
123.
124.
不同蕨类植物提取物乙酰胆碱酯酶抑制活性的评价 总被引:3,自引:2,他引:3
为对采自浙江天目山的40种蕨类植物乙醇提取物进行乙酰胆碱酯酶抑制活性研究。本文采用乙酰胆碱酯酶抑制活性筛选模型。结果表明:在供试质量浓度在1mg/mL时,40种植物的乙醇提取物均具有明显的乙酰胆碱酯酶抑制活性,其中密羽贯众、野雉尾金粉蕨和狗脊等13种蕨类植物表现出较强的抑制活性,抑制率均大于90%,其余大部分植物的抑制率均大于60%。而在供试质量浓度在0.025mg/mL时,只有少数植物表现出较高的乙酰胆碱酯酶抑制活性,其中狭顶鳞毛蕨的抑制率为62.63%±3.72%,蜈松草的抑制率为48.01%±2.87%,其余大部分植物的抑制活性均小于40%,甚至有些植物提取物不仅对乙酰胆碱酯酶没有抑制活性,反而表现出一定的增强作用。 相似文献
125.
Guoqin Huang Xiuying Liu Longwang Liu Fang Ye Mingling Zhang Yanhong Shu 《Frontiers of Biology in China》2008,3(3):344-350
According to the principles and methods of ecology and system engineering, we set up an evaluation indicator system for multi-component
and multiple cropping systems, evaluated the comprehensive benefits of multi-component and multiple cropping systems using
grey relation clustering analysis and screened out the optimized model based on research done in the upland red soil in Jiangxi
Agricultural University from 1984 to 2004. The results show that the grey relation degree of “cabbage/potato/maize — sesame”
was the highest among 23 multi-component and multiple cropping systems and was clustered into the optimized system. This indicates
that “cabbage/potato/maize — sesame” can bring the best social, economic and ecological benefits, increase product yield and
farmers’ income and promote sustainable development of agricultural production. Therefore, it is suitable for promotion on
upland red soil. The grey relation degree of “canola/Chinese milk vetch/maize/mung bean/maize” was second, which is suitable
for implementation at the city outskirts. In conclusion, these two planting patterns are expected to play important roles
in the reconstruction of the planting structure and optimization of the planting patterns on upland red soil.
__________
Translated from Acta Ecologica Sinica, 2006, 26(8): 2532–2539 [译自: 生态学报] 相似文献
126.
基因工程菌大肠杆菌JM109富集废水中镍离子的研究 总被引:4,自引:2,他引:4
利用通过基因工程技术所构建的在细胞内同时表达出高特异性镍转运蛋白和金属硫蛋白的基因工程菌富集水体中的镍离子。菌体细胞对Ni2+的富集速率很快,富集过程满足Langmuir等温线模型。与原始宿主菌相比,经基因改造的基因工程菌不仅最大镍富集容量增加了5倍多,而且对pH值、离子强度的变化及其它共存重金属离子的影响都呈现出更强的适应性。相比而言,Na+、Ca2+、Cd2+、Pb2+的影响较小,但Mg2+、Hg2+和Cu2+所引起的负面效应较大。进一步的实验表明基因工程菌对Ni2+的富集行为不需要外加营养物质。 相似文献
127.
湖泊生态系统弹性系数理论及其应用 总被引:1,自引:1,他引:1
在湖泊生态系统健康评价的基础上,分析城市湖泊营养状态的特殊性,论证得出响应型和非响应型湖泊的生态系统健康指数(EHI)与营养状态指数(TSI)近似呈二次函数关系.提出湖泊生态系统弹性系数,对生态系统健康指数(EHI)做出适当改进.改进后的生态系统健康指数(EHI′)能够更好地反映各类型湖泊的健康状态,完善了Xu等的EHI理论并扩展了其应用范围,是目前最为接近Costanza对HI定义的可量化计算的数学公式和方法,并成功用于厦门杏林湾生态系统健康评价. 相似文献
128.
Synthetic antimicrobial β‐peptide in dual‐treatment with fluconazole or ketoconazole enhances the in vitro inhibition of planktonic and biofilm Candida albicans 下载免费PDF全文
Camilo Mora‐Navarro Jean Caraballo‐León Madeline Torres‐Lugo Patricia Ortiz‐Bermúdez 《Journal of peptide science》2015,21(12):853-861
Fungal infections are a pressing concern for human health worldwide, particularly for immunocompromised individuals. Current challenges such as the elevated toxicity of common antifungal drugs and the emerging resistance towards these could be overcome by multidrug therapy. Natural antimicrobial peptides, AMPs, in combination with other antifungal agents are a promising avenue to address the prevailing challenges. However, they possess limited biostability and susceptibility to proteases, which has significantly hampered their development as antifungal therapies. β‐peptides are synthetic materials designed to mimic AMPs while allowing high tunability and increased biostability. In this work, we report for the first time the inhibition achieved in Candida albicans when treated with a mixture of a β‐peptide model and fluconazole or ketoconazole. This combination treatment enhanced the biological activity of these azoles in planktonic and biofilm Candida, and also in a fluconazole‐resistant strain. Furthermore, the in vitro cytotoxicity of the dual treatment was evaluated towards the human hepatoma cell line, HepG2, a widely used model derived from liver tissue, which is primarily affected by azoles. Analyses based on the LA‐based method and the mass‐action law principle, using a microtiter checkerboard approach, revealed synergism of the combination treatment in the inhibition of planktonic C. albicans. The dual treatment proved to be fungicidal at 48 and 72 h. Interestingly, it was also found that the viability of HepG2 was not significantly affected by the dual treatments. Finally, a remarkable enhancement in the inhibition of the highly azole‐resistant biofilms and fluconazole resistant C. albicans strain was obtained. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
129.
城市生态系统是城市社会经济发展的基础和载体,但城市生态系统健康状况问题中包含多种不确定性因素,而集对分析可以有效处理这种不确定性.论文以特大型综合性城市兰州为研究案例,基于集对分析方法,构建包括生产力、生活态、生态势和生机度的城市生命力指数,诊断兰州城市生态系统2002至2008年间的健康状态.研究结果表明:2002~2008年,兰州市城市生态系统健康状况呈上升趋势,其健康联系度由2002年的0.451增至2008年的0.519,但总体水平仍不高.该研究为兰州市城市规划和生态建设推荐了重点行动领域,同时也可为兰州市实施可持续发展战略提供决策依据. 相似文献
130.
家兔腹泻生态疗法的实验观察 总被引:1,自引:0,他引:1
根据动物微生态学理论,将3株正常菌:嗜酸乳杆菌、两歧双歧杆菌、粪链球菌研制成复方生态制剂,对家免细菌性腹泻进行治疗试验。共治疗75例,治愈率为96.00%,比痢特灵对照组治愈率提高16.00%。该制剂价格低廉,无毒、副作用,使用安全可靠,是一种防治家免细菌性腹泻的较理想制剂。 相似文献