全文获取类型
收费全文 | 1102篇 |
免费 | 63篇 |
国内免费 | 123篇 |
出版年
2023年 | 15篇 |
2022年 | 20篇 |
2021年 | 14篇 |
2020年 | 33篇 |
2019年 | 25篇 |
2018年 | 28篇 |
2017年 | 24篇 |
2016年 | 23篇 |
2015年 | 24篇 |
2014年 | 59篇 |
2013年 | 85篇 |
2012年 | 47篇 |
2011年 | 71篇 |
2010年 | 28篇 |
2009年 | 35篇 |
2008年 | 42篇 |
2007年 | 37篇 |
2006年 | 35篇 |
2005年 | 38篇 |
2004年 | 28篇 |
2003年 | 39篇 |
2002年 | 35篇 |
2001年 | 35篇 |
2000年 | 34篇 |
1999年 | 26篇 |
1998年 | 27篇 |
1997年 | 21篇 |
1996年 | 18篇 |
1995年 | 23篇 |
1994年 | 35篇 |
1993年 | 24篇 |
1992年 | 26篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 8篇 |
1980年 | 17篇 |
1979年 | 9篇 |
1977年 | 12篇 |
1976年 | 12篇 |
1975年 | 10篇 |
1974年 | 13篇 |
1973年 | 10篇 |
排序方式: 共有1288条查询结果,搜索用时 15 毫秒
81.
82.
厌氧氨氧化体的组成、结构与功能 总被引:2,自引:1,他引:1
厌氧氨氧化(Anammox)是微生物和环境领域的研究热点之一。厌氧氨氧化菌(AnAOB)是Anammox的功能载体。不同于大部分原核微生物,AnAOB具有独特的细胞器——厌氧氨氧化体,它是进行Anammox代谢的场所。研究厌氧氨氧化体有助于探明厌氧氨氧化菌的代谢特性。本文综述了厌氧氨氧化体的组成、结构与功能,以期为从事Anammox研究的同行提供参考。 相似文献
83.
Mitigation of ammonia inhibition by internal dilution in high‐rate anaerobic digestion of food waste leachate and evidences of microbial community response
下载免费PDF全文
![点击此处可从《Biotechnology and bioengineering》网站下载免费的PDF全文](/ch/ext_images/free.gif)
84.
85.
Oxygen consumption and ammonia excretion of juvenile pink shrimp (Farfantepenaeus paulensis) in culture: temperature effects 总被引:1,自引:0,他引:1
Edison Barbieri Aline Maria Zigiotto de Medeiros Marcelo Barbosa Henriques 《Marine and Freshwater Behaviour and Physiology》2016,49(1):19-25
We evaluated oxygen consumption and ammonia excretion by juveniles of the pink shrimp Farfantepenaeus paulensis at three different temperatures (15, 20 and 25 °C). The shrimp were collected in the coastal region of Cananéia, São Paulo State, Brazil. The selected temperatures are the limits recorded in aquaculture tanks in the coastal region of Cananéia. We measured oxygen consumption and ammonia excretion as proxies for metabolic activity. Oxygen consumption and ammonia excretion increased with increasing temperature, but no change was observed at 15 and 20 °C. It is possible that within this temperature range, there is thermal independence in juvenile F. paulensis do not need to allocate additional energy to compensate for temperature changes because they are physiologically adapted for this range. 相似文献
86.
《Harmful algae》2019
Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1–3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds.Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts. 相似文献
87.
Rongting Xu Hanqin Tian Shufen Pan Stephen A. Prior Yucheng Feng William D. Batchelor Jian Chen Jia Yang 《Global Change Biology》2019,25(1):314-326
Excessive ammonia (NH3) emitted from nitrogen (N) fertilizer applications in global croplands plays an important role in atmospheric aerosol production, resulting in visibility reduction and regional haze. However, large uncertainty exists in the estimates of NH3 emissions from global and regional croplands, which utilize different data and methods. In this study, we have coupled a process‐based Dynamic Land Ecosystem Model (DLEM) with the bidirectional NH3 exchange module in the Community Multiscale Air‐Quality (CMAQ) model (DLEM‐Bi‐NH3) to quantify NH3 emissions at the global and regional scale, and crop‐specific NH3 emissions globally at a spatial resolution of 0.5° × 0.5° during 1961–2010. Results indicate that global NH3 emissions from N fertilizer use have increased from 1.9 ± 0.03 to 16.7 ± 0.5 Tg N/year between 1961 and 2010. The annual increase of NH3 emissions shows large spatial variations across the global land surface. Southern Asia, including China and India, has accounted for more than 50% of total global NH3 emissions since the 1980s, followed by North America and Europe. Rice cultivation has been the largest contributor to total global NH3 emissions since the 1990s, followed by corn and wheat. In addition, results show that empirical methods without considering environmental factors (constant emission factor in the IPCC Tier 1 guideline) could underestimate NH3 emissions in context of climate change, with the highest difference (i.e., 6.9 Tg N/year) occurring in 2010. This study provides a robust estimate on global and regional NH3 emissions over the past 50 years, which offers a reference for assessing air quality consequences of future nitrogen enrichment as well as nitrogen use efficiency improvement. 相似文献
88.
Marina Kurbasic Ana M. Garcia Simone Viada Silvia Marchesan 《Journal of peptide science》2022,28(1):e3304
Self-assembling short peptides have attracted great interest as enzyme mimics, especially if the catalytic activity resides solely in the supramolecular structure so that it can be switched on/off as needed by controlling assembly/disassembly. Among the various enzyme classes, hydrolases find wide application in biomaterials, and their mimetics often contain His residues, in addition to either divalent cations or other amino acids to mimic the catalytic site. This work reports two self-assembling tetrapeptides based on the Ser-His motif for catalysis and the Phe-Phe motif to drive amyloid structure formation. Both peptides form thermoreversible hydrogels in phosphate buffer at neutral pH that display a mild esterase-like activity, as demonstrated on the hydrolysis of 4-nitrophenyl acetate as a model substrate, although presence of Ser did not enhance catalytic activity. The systems are characterised by circular dichroism, transmission electron microscopy, oscillatory rheology and Thioflavin T fluorescence as an amyloid stain, to provide further insights that may assist the future design of improved supramolecular catalysts. 相似文献
89.
90.
黄酮类化合物是桦褐孔菌菌丝体中多酚类化合物的重要组成部分,也是该菌治疗众多疾病的有效成分之一。然而人工培养桦褐孔菌黄酮等酚类化合物积累甚少,导致药理活性的明显下降。为此,我们研究了3种氨基酸和4种霉菌水提物对深层发酵桦褐孔菌黄酮的积累及其抗氧化能力的影响。在所试验的3种氨基酸和4种霉菌水提物中,L-酪氨酸,黄曲霉和毛霉水提物能有效地增加该菌黄酮的积累。人工培养菌体中的黄酮至少由4种黄酮苷组成,苷元分别是槲皮素、柚皮素、山奈酚和异鼠李素。深层发酵菌丝体具有一定的抗氧化能力,并与总黄酮的含量呈正相关。由L-酪氨酸,黄曲霉和毛霉水提物调控生长的桦褐孔菌菌丝体,能有效地清除超氧阴离子、羟基自由基和DPPH自由基。 相似文献