首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   197篇
  免费   22篇
  国内免费   68篇
测绘学   1篇
大气科学   1篇
地球物理   27篇
地质学   34篇
海洋学   181篇
综合类   23篇
自然地理   20篇
  2023年   3篇
  2022年   1篇
  2021年   5篇
  2020年   3篇
  2019年   11篇
  2018年   8篇
  2017年   10篇
  2016年   7篇
  2015年   10篇
  2014年   17篇
  2013年   13篇
  2012年   16篇
  2011年   9篇
  2010年   16篇
  2009年   16篇
  2008年   17篇
  2007年   12篇
  2006年   16篇
  2005年   13篇
  2004年   12篇
  2003年   9篇
  2002年   9篇
  2001年   6篇
  2000年   9篇
  1999年   4篇
  1998年   8篇
  1997年   5篇
  1996年   3篇
  1995年   1篇
  1994年   2篇
  1993年   3篇
  1992年   9篇
  1991年   1篇
  1990年   1篇
  1978年   1篇
  1973年   1篇
排序方式: 共有287条查询结果,搜索用时 140 毫秒
181.
应用反相高效液相色谱定性和定量浮游植物光合色素   总被引:1,自引:0,他引:1  
胡俊  柳欣  王磊  黄邦钦 《海洋科学》2011,35(11):19-28
利用本实验室建立的反相高效液相色谱实验体系分析了19 种高纯度的浮游植物光合色素标准样品的特征参数。结果显示, 该体系可将各种光合色素较好分离, 但个别色素的保留时间、洗脱顺序、最大吸收波长及响应因子与文献报道的其他实验体系有所差异。表明在利用反相高效液相色谱定性、定量光合色素时不仅要参考其保留时间, 还要参考其最大吸...  相似文献   
182.
长棘海星(Acanthaster planci)的暴发是导致我国南海乃至印度—太平洋海域珊瑚礁退化的主要原因之一。浮游幼体的密度是决定成体种群是否暴发的重要指标, 但是由于幼体肉眼不可见且不易分辨, 常规调查和显微镜观察均无法有效检测到自然海域的长棘海星幼体, 因此迫切需要开发一种高灵敏性且特异性的长棘海星幼体检测技术。本研究针对长棘海星幼体线粒体细胞色素氧化酶亚基I(mtCOI, mitochondrial cytochrome oxidase subunit I)基因序列, 建立了基于聚合酶链式反应(PCR, polymerase chain reaction)的长棘海星幼体特异性检测技术, 并对西沙七连屿珊瑚礁海域的长棘海星幼体进行了检测。结果表明, 设计筛选的4对特异性引物均可以扩增长棘海星ApmtCOI基因片段, 且与蓝指海星(Linckia laevigata)、面包海星(Culcita novaeguineae)、粒皮海星(Choriaster granulatus)和吕宋棘海星(Echinaster luzonicus)没有交叉反应。在退火温度为58.5℃时, 引物2aooniF/2aooniR的特异性最佳, 具有较高的灵敏度, 可检测到皮克级的长棘海星基因组DNA。利用该技术检测了西沙七连屿海域长棘海星幼体分布情况, 发现10月底西沙七连屿珊瑚礁海域能检测到长棘海星幼体, 且幼体分布并不均匀。因此, 该检测技术可作为今后长棘海星幼体种群监测的有效方法。  相似文献   
183.
为探究全缘马尾藻(Sargassum intrgerrimum)幼孢子体对温度的适应性,在照度为10 000 lx,光照周期为12L:12D,温度分别为11.0、16.0、21.0、26.0、31.0、36.0℃的条件下,研究不同温度对全缘马尾藻幼孢子体生长、光合色素含量、SOD活力和CAT活力的影响。结果表明,幼孢子体在16.0~26.0℃的温度范围内生长明显,差异有统计学意义(P﹤0.05),温度为21.0℃时生长最快;温度为11.0℃时生长缓慢,温度为31.0和36.0℃时幼孢子体的生长因温度过高有溃烂现象。在本实验条件下,全缘马尾藻幼孢子体的适宜温度范围为16.0~26.0℃,最适温度为21.0℃。  相似文献   
184.
CHEMTAX analysis of high-performance liquid chromatography(HPLC) pigment was conducted to study phytoplankton community structure in the northern Bering Sea shelf, where a seasonal subsurface cold pool emerges. The results showed that fucoxanthin(Fuco) and chlorophyll a(Chl a) were the most abundant diagnostic pigments, with the integrated water column values ranging from 141 to 2 160 μg/m2 and 477 to 5 535 μg/m2, respectively. Moreover, a diatom bloom was identified at Sta. BB06 with the standing stock of Fuco up to 9 214 μg/m3. The results of CHEMTAX suggested that the phytoplankton community in the northern Bering Sea shelf was dominated by diatoms and chrysophytes with an average relative contribution to Chl a of 80% and 12%, respectively, followed by chlorophytes, dinoflagellates, and cryptophytes. Diatoms were the absolutely dominant algae in the subsurface cold pool with a relative contribution exceeding 90%, while the contribution of chrysophytes was generally higher in oligotrophic upper water. Additionally, the presence of a cold pool would tend to favor accumulation of diatom biomass and a bloom that occurred beneath the halocline would be beneficial to organic matter sinks, which suggests that a large part of the phytoplankton biomass would settle to the seabed and support a rich benthic biomass.  相似文献   
185.
Identification of hydrozoan species is challenging, even for taxonomic experts, due to the scarcity of distinct morphological characters and phenotypic plasticity. DNA barcoding provides an efficient method for species identification, however, the choice between mitochondrial cytochrome c oxidase subunit I(COI) and large subunit ribosomal RNA gene(16S) as a standard barcode for hydrozoans is subject to debate. Herein, we directly compared the barcode potential of COI and 16S in hydrozoans using 339 sequences from 47 pelagic hydrozoan species. Analysis of Kimura 2-parameter genetic distances(K2P) documented the mean intraspecific/interspecific variation for COI and 16S to be 0.004/0.204 and 0.003/0.223, respectively. An obvious "barcoding gap" was detected for all species in both markers and all individuals of a species clustered together in both the COI and 16S trees. These results suggested that the species within the studied taxa can be efficiently and accurately identified by COI and 16S. Furthermore, our results confirmed that 16S was a better phylogenetic marker for hydrozoans at the genus level, and in some cases at the family level. Considering the resolution and effectiveness for barcoding and phylogenetic analyses of Hydrozoa, we strongly recommend 16S as the standard barcode for hydrozoans.  相似文献   
186.
Reaumuria soongorica is a short woody shrub widely found in semi-arid areas of China. It can survive severe environ- mental stress including high salinity in its natural habitat. Thus, we investigated the involvement of anti-oxidative enzymes, photosynthetic pigments and flavonoid metabolism in the adaptation of R. soongorica to saline environments. R. soon- gorica was treated with 0, 100, 200 and 400 mM NaC1 solutions for 14 days. Soil salt content increased significantly by watering with high content of NaC1 solution, and no variation between 8 and 14 days during treatment. The levels ofpe- roxidation of lipid membranes (measured by malondialdehyde content) and the activities of three antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX)) increased under salt stress. Chlorophyll and carotenoid content decreased with increasing salt content. The ratio of Chl a/Chl b and carotenoid/Chl exhibited sig- nificant increase under 400 mM NaC1. However, total flavonoid and anthocyanin contents and key enzyme activities in the flavonoid pathway including phenylalanine ammonialyase (PAL) and Chalcone isomerase (CHI) decreased under salt stress. These findings possibly suggest that R. soongorica has an adaptation protection mechanism against salt-induced oxidative damage by inducin~ the activity of antioxidant enzymes and maintaining a steady level of carotenoid/Chl.  相似文献   
187.
对虾壳色素提取及部分性质研究   总被引:1,自引:0,他引:1  
以水产加工废弃物 (对虾壳 )为原料 ,经过对对虾壳的烘干、碾碎、提取、洗涤和分离 ,提取了对虾壳色素。探讨了该虾壳色素的部分性质 ,得到如下初步结论 :在可见光区对虾壳色素的 λmax为 470 nm,在 1 0 0℃加热时间不超过 1 5 min的条件下对虾壳色素对热较稳定 ,耐氧化 ,光照影响对虾壳色素的稳定性。  相似文献   
188.
189.
In this study, Raman scattering measurements were obtained for momo corals covering their typical range of colors. Three different excitation wavelengths (785, 633, 514 nm) are used for the same samples at the same points. All the samples show the two major Raman features of polyenic compounds assigned to double carbon-carbon (C=C) stretching vibration at approximately 1 500 cm-1 and single carbon-carbon (C--C) stretching vibration at approximately 1 130 cm-1 bond stretching mode. These peaks are not detected in the corresponding white parts of momo corals. However, somechanges in intensities, shape, and position of C=C stretching vibrations of the same point are observed by using different excitation wavelengths. The exact position of C-C stretching vibration of polyenic molecules depends strongly on the number of double bonds contained in their polyenic chain. In addition, the number of double bonds contained in the polyenic chains shows that different colors of the red momo coral are caused by different mixtures of polyenic compounds.  相似文献   
190.
本文以苋菜红、胭脂红组成的两组份混合体系为研究对象,应用改进单纯形优化法对混合色素进行同时测定的研究。结果表明,采用该法优化混合物的各组份浓度具有可行性。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号