全文获取类型
收费全文 | 1204篇 |
免费 | 56篇 |
国内免费 | 96篇 |
出版年
2024年 | 4篇 |
2023年 | 15篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 22篇 |
2019年 | 53篇 |
2018年 | 29篇 |
2017年 | 51篇 |
2016年 | 37篇 |
2015年 | 35篇 |
2014年 | 61篇 |
2013年 | 62篇 |
2012年 | 41篇 |
2011年 | 44篇 |
2010年 | 26篇 |
2009年 | 58篇 |
2008年 | 67篇 |
2007年 | 72篇 |
2006年 | 57篇 |
2005年 | 61篇 |
2004年 | 42篇 |
2003年 | 31篇 |
2002年 | 42篇 |
2001年 | 31篇 |
2000年 | 27篇 |
1999年 | 27篇 |
1998年 | 16篇 |
1997年 | 23篇 |
1996年 | 18篇 |
1995年 | 19篇 |
1994年 | 25篇 |
1993年 | 17篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 19篇 |
1988年 | 8篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 21篇 |
1983年 | 4篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 8篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 15篇 |
1975年 | 3篇 |
排序方式: 共有1356条查询结果,搜索用时 15 毫秒
101.
102.
103.
Effects of hydrodynamics on phosphorus concentrations in water of Lake Taihu,a large,shallow, eutrophic lake of China 总被引:4,自引:0,他引:4
Guangwei Zhu Boqiang Qin Guang Gao Lu Zhang Liancong Luo Yunlin Zhang 《Hydrobiologia》2007,581(1):53-61
To understand the effect of hydrodynamical process on water phosphorus concentration, wind, wave, and several water quality
indices were observed in Meiliang Bay, a shallow and eutrophic bay locates in north of Lake Taihu. During the 7 day observation
period, wind speed and significant wave height were recorded more than 3 h per day, and water samples were collected in five
water-depth layers once a day. Hydrodynamical disturbance had no significant correlationship with the water quality at the
top layer when the significant wave height was smaller than 30 cm, but it significantly increased suspended solids (SS) concentration
of the bottom water layer. Concentrations of nutrients showed no positive correlationship with SS concentration in the water
body. Intensive sediment resuspension may not have occurred when the hydrodynamic stress on sediment was only a little higher
than the critical stress for sediment resuspension. A new method for confirming the critical stress for intensive sediment
resuspension and nutrient release still needs to be developed. The range of the water quality indices was quite high during
the seven days of observation. High variation seems to be a common character of large shallow lakes like Taihu. 相似文献
104.
粤东柘林湾中肋骨条藻(Skeletonema costatum)种群生态学 总被引:2,自引:0,他引:2
于2000年5月~2004年12月对粤东大规模养殖区柘林湾的赤潮藻中肋骨条藻(Skeletonema costatum)种群的时空分布进行了长达5a的调查。结果表明,中肋骨条藻种群密度的周年变动模式基本为双峰型,平面分布没有显著的空间差异。调查期间,中肋骨条藻种群密度的站位实测值为0~1.4×10^7cells/dm^3,总均值为3.3×10^5cells/dm^3,占浮游植物总细胞数的67.1%,为调查海区第1优势种。在总共1045份样品中,有中肋骨条藻出现的样品数为1020份。其中,种群密度大于10^6cells/dm^3的样品有65份,大于10^7cells/dm。则有4份。以大于10^6cells/dm^3为中肋骨条藻的赤潮密度标准,在调查期间至少于2000年、2003年发生4次赤潮。运用灰关联理论对中肋骨条藻种群密度与13个环境因子的关系进行排序分析发现,水温、pH值和浮游动物是影响柘林湾中肋骨条藻种群时空分布的关键因子。水温还与中肋骨条藻种群密度的对数值具极显著意义的线性关系,而达到赤潮密度的样品均落在24.5~32.0℃区间,即每年的5~9月份高温季节。由于柘林湾浮游动物的年高峰期也出现在高温季节,说明浮游动物摄食压力的存在可能是柘林湾中肋骨条藻赤潮发生的重要抑制因子。2004年调查海区中肋骨条藻种群密度和在浮游植物群落中的优势度骤然降低,可能与水体营养盐结构和Fe含量的变化有关。因此,长期调查与监测对于研究海湾生态学和赤潮发生机制是极为重要的。 相似文献
105.
Hai Quoc Luyen Ji-Young Cho Hyun-Woung Shin Nam Gyu Park Yong-Ki Hong 《Journal of applied phycology》2007,19(2):175-180
Microalgal growth was enhanced by the addition of levoglucosan to the culture medium. The growth-enhancing compound levoglucosan
was isolated from the green seaweed Monostroma nitidum using water extraction, molecular fractionation, DEAE-cellulose column chromatography, and high-performance liquid chromatography.
Yield of the compound from seaweed powder was 5 × 10−3% (w/w). At 10 mM concentration, levoglucosan enhanced cell growth and the specific growth rate of all feed microalgal species
tested (Chaetoceros gracilis, Chlorella ellipsoidea, Dunaliella salina, Isochrysis galbana, Nannochloris oculata, Navicula incerta, Pavlova lutheri, Tetraselmis suecica) in most culture media by approximately 150%. Cellular fatty acid profiles and cell size differed marginally between cultures
with and without levoglucosan. 相似文献
106.
Bioassays were performed to investigate the effects of the novel allelochemical, ethyl 2-methylacetoacetate (EMA), isolated
from the reed (Phragmitis australis) on the growth of three common species of algae; Scenedesmus obliquus, Selenastrum capricornutum and Chlamydomonas reinhardtii. The results demonstrated that EMA has three quite different types of effect on these three species of algae. The growth
of S. capricornutum was significantly inhibited by EMA during the whole cultivation period. The EC50 values of EMA on S. capricornutum was 0.6 mg L−1(7 days). However, the inhibitory effect of EMA on S. obliquus was apparent during the first 4 days of batch cultivation and then the inhibitory effect disappeared, and a stimulating effect
was observed instead. The EC50 value of EMA on S. obliquus was 0.43 mg L−1(4 days). In addition, following the addition of EMA, the cells of S. obliquus and S. capricornutum became significantly larger than the normal untreated one and the algal cells changed morphologically. The microstructure
of the algal cells was disrupted by the addition of EMA. There was no significant inhibition of the growth of C. reinhardtii by EMA, but cell motility was affected. 相似文献
107.
Uwe John Urban Tillmann Jennifer Hülsk?tter Tilman J. Alpermann Sylke Wohlrab Dedmer B. Van de Waal 《Proceedings. Biological sciences / The Royal Society》2015,282(1798)
Dinoflagellates are a major cause of harmful algal blooms (HABs), with consequences for coastal marine ecosystem functioning and services. Alexandrium fundyense (previously Alexandrium tamarense) is one of the most abundant and widespread toxigenic species in the temperate Northern and Southern Hemisphere and produces paralytic shellfish poisoning toxins as well as lytic allelochemical substances. These bioactive compounds may support the success of A. fundyense and its ability to form blooms. Here we investigate the impact of grazing on monoclonal and mixed set-ups of highly (Alex2) and moderately (Alex4) allelochemically active A. fundyense strains and a non-allelochemically active conspecific (Alex5) by the heterotrophic dinoflagellate Polykrikos kofoidii. While Alex4 and particularly Alex5 were strongly grazed by P. kofoidii when offered alone, both strains grew well in the mixed assemblages (Alex4 + Alex5 and Alex2 + Alex5). Hence, the allelochemical active strains facilitated growth of the non-active strain by protecting the population as a whole against grazing. Based on our results, we argue that facilitation among clonal lineages within a species may partly explain the high genotypic and phenotypic diversity of Alexandrium populations. Populations of Alexandrium may comprise multiple cooperative traits that act in concert with intraspecific facilitation, and hence promote the success of this notorious HAB species. 相似文献
108.
109.
Katherine A. McHugh Jason B. Allen Aaron A. Barleycorn Randall S. Wells 《Marine Mammal Science》2011,27(3):622-643
Harmful algal blooms (HABs) are natural stressors in the coastal environment that may be increasing in frequency and severity. This study investigates whether severe red tide blooms, caused by Karenia brevis, affect the behavior of resident coastal bottlenose dolphins in Sarasota Bay, Florida through changes to juvenile dolphin activity budgets, ranging patterns, and social associations. Behavioral observations were conducted on free‐ranging juvenile dolphins during the summer months of 2005–2007, and behavior during red tide blooms was compared to periods of background K. brevis abundance. We also utilized dolphin group sighting data from 2004 to 2007 to obtain comparison information from before the most severe recent red tide of 2005 and incorporate social association information from adults in the study area. We found that coastal dolphins displayed a suite of behavioral changes associated with red tide blooms, including significantly altered activity budgets, increased sociality, and expanded ranging behavior. At present, we do not fully understand the mechanism behind these red tide‐associated behavioral effects, but they are most likely linked to underlying changes in resource availability and distribution. These behavioral changes have implications for more widespread population impacts, including increased susceptibility to disease outbreaks, which may contribute to unusual mortality events during HABs. 相似文献
110.
The use of ultrasound for the control of algae and in particular for Microcystis aeruginosa has been investigated. The results indicate that sonication may provide a more environmentally friendly and more effective method for the control of cyanobacteria blooms than conventional treatments.Algae blooms occur frequently and globally in water bodies and are a major concern in terms of their effects on other species such as plants, fish and other microorganisms together with the potential danger to human health from cyanobacterial toxins that are carcinogenic. In addition to removing the algae itself ultrasound can also degrade such toxins. A range of ultrasonic conditions (in terms of frequency and intensity) have been studied under laboratory conditions together with a small number of pilot (field) studies that confirm the potential for ultrasonic treatment of algae on a large scale. 相似文献