全文获取类型
收费全文 | 179篇 |
免费 | 9篇 |
国内免费 | 42篇 |
专业分类
大气科学 | 6篇 |
地球物理 | 16篇 |
地质学 | 43篇 |
海洋学 | 132篇 |
综合类 | 25篇 |
自然地理 | 8篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 2篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 11篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 9篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1991年 | 2篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有230条查询结果,搜索用时 15 毫秒
81.
为了探究一种新型纳豆菌发酵食品的最佳工艺,利用纳豆菌发酵大豆和海带,以发酵物中游离氨基酸态氮含量和纳豆激酶活性为评价指标,通过单因素试验和正交试验确定最佳发酵条件。结果表明,发酵温度42℃、发酵时间54 h、接种量1%、料水比(m/v)1︰4、配料比(大豆︰海带)2︰1时发酵产物中游离氨基酸态氮含量最高(0.041%);发酵温度40℃、发酵时间48 h、接种量3%、料水比(m/V)1︰2,配料比(大豆︰海带)3︰1时发酵产物中纳豆激酶活性最高(可达1426.53IU/g)。 相似文献
82.
83.
为探究海水养殖池塘红树林浮岛养殖拟穴青蟹(Scylla paramamosain)的生长及其与野生拟穴青蟹营养成分的差异,选择福建省漳浦县东山湾北部的海水养殖池塘内设置四个拟穴青蟹养殖实验组,分别为红树林(秋茄)浮岛养殖组、海马齿浮岛养殖组、空白浮岛养殖组(水面无种植植物)和外围环沟养殖组,并以试验点附近海区捕获的拟穴青蟹(野生组)作为对照,对各组拟穴青蟹的肌肉营养成分进行分析。结果显示,空白浮岛组拟穴青蟹增重率、特定生长率、出肉率及存活率均高于红树林浮岛组、海马齿浮岛组和外围环沟组;红树林浮岛养殖拟穴青蟹肌肉粗蛋白含量(71.66%)最高,粗脂肪含量(2.52%)相对较低,各组拟穴青蟹肌肉中氨基酸总量在60.54%~68.68%之间,其中红树林浮岛组拟穴青蟹肌肉中氨基酸总量、必需氨基酸总量上均显著高于野生组(P<0.05);从氨基酸评分(AAS)和化学评分(CS)结果可以得出拟穴青蟹的第一限制性氨基酸是蛋氨酸+胱氨酸,各组拟穴青蟹肌肉中必需氨基酸指数(EAAI)均高于0.75;肌肉中均富含不饱和脂肪酸,尤其是多不饱和脂肪酸;红树林浮岛组拟穴青蟹肌肉中多不饱和脂肪酸总量(ΣPUF... 相似文献
84.
缢蛏肉的食品化学特性及其营养液的研制 总被引:7,自引:0,他引:7
研究了缢蛏(Sinonovacula constricta(Lamarck))内的食品化学特性。结果表明,缢蛏内的营养特点是蛋白质丰富,低脂肪,富含灰分和总糖;蛋白质的氨基酸组成中富含呈味氨基酸.并富含婴幼儿所需的组氨酸、亮氨酸和赖氨酸;蛋白质氨基酸价为82,其显著特点是只有一种限制氨基酸,且其它氨基酸效价较均衡,说明必需氨基酸的组成比较合理;缢蛏贝内中含有丰富矿物质元素,是人体所需的多种矿物质元素的良好来源。在此基础上研制了缢蛏营养液.缢蛏营养液含有缢蛏内的全部营养,易吸收,无明显腥味。 相似文献
85.
实验测定了海水中氨基酸存在下Cu(Ⅱ)在r-MnOOH上吸附的等温线、Cu(Ⅱ)%--pH曲线和Cu(Ⅱ)%-氨基酸深度曲线。结果表明,较低浓度氨基酸对Cu(Ⅱ)在r-MnOOH上吸附没有影响,而较高浓度氨基酸却起抑制作用,这主要是由于海水中Cu(Ⅱ)-氨基酸络合反应与r-MnOOH竞争Cu(Ⅱ)所致。此外,海水中较高浓度氨基酸只使Cu(Ⅱ)在r-MnOOH上吸附的表面分级离子交换稳定常数Ki(i 相似文献
86.
Factors Influencing Nitrogen Speciation in Coastal Rainwater 总被引:1,自引:0,他引:1
Rainwater was collected from 129 rain events between February 2002 and August 2003 and analyzed for ammonium (NH4+), nitrate (NO3−), organic nitrogen (ON) and free amino acids (AA). Inorganic nitrogen (NO3− + NH4+) was the dominant form of N representing 85% of total nitrogen based on volume-weighted averages. The remainder of the N
occurred as organic nitrogen species of which free amino acids contribute approximately 17%. A significant, and in some cases
the majority (> 75%), of the remaining ON could be accounted for by macromolecular uncharacterized humic like substances.
This has important ramifications with respect to the long range transport of atmospheric ON because humic materials are recalcitrant
and therefore may travel long distances from their source. There was a distinct seasonality to the N speciation data with
maximum concentrations of NH4+, ON and AA occurring in the spring. Air-mass back trajectory analysis indicates there is a strong anthropogenic component
to the NO3−, NH4+ and AA signal but not ON. There was a strong positive correlation between amino acid concentrations and ammonium which suggests
they have similar sources and sinks in rainwater. Finally, large episodic additions of NH4+ and AA during tropical events could significantly impact short term bioavailable N budgets in estuaries impacted by these
storms. Approximately three times as much NH4+ and AA were deposited during Hurricane Isabel (317 μ moles ⋅ m−2 and 84 μ moles ⋅ m−2 respectively) compared to the mean impact of average summertime rain events at this location. 相似文献
87.
The variation in mycosporine‐like amino acid (MAA) concentration in the soft coral Heteroxenia fuscescens in relation to changes in ultraviolet radiation (UVR) regimes was investigated at the Gulf of Eilat, northern Red Sea. Solar radiation (300–700 nm) was measured for different depths and seasons. The UVR irradiance was measured to a depth of 25 m on the reef. The mean attenuation coefficient for UV‐B measured in winter was twofold that of the summer value. Separation of H. fuscescens extracts by reverse‐phase isocratic high‐performance liquid chromatography revealed a single MAA compound, palythine (λmax = 320 nm). Possible seasonal changes in MAAs in colonies of H. fuscescens along a depth gradient were examined on different dates. Palythine concentrations in the colonies were significantly higher in summer than in the other seasons particularly in shallow water. Possible changes in MAA content in colonies of H. fuscescens as a result of UVR protection, were determined by experiments conducted for periods of 1 week, 1 month and 3 months, at a depth of 5 m. In these experiments colonies were removed from the natural substrate and placed underwater, protected from UVR by a PVC filter. Significant differences between UV‐exposed and protected colonies of H. fuscescens were found only in the 3‐month experiment conducted during the summer. These findings demonstrate that UVR is an important environmental factor regulating MAA biosynthesis in the soft coral H. fuscescens. 相似文献
88.
89.
90.
Soil core samples fromRhizophora mangleL. andAvicennia schauerianaStapf & Leech forests from south-eastern Brazil were analysed for their total organic matter content and their sugars, amino acid and amino sugars composition. Organic carbon and nitrogen contents were higher inAvicenniathan inRhizophorasoils. The contribution of sugars and amino acids to the total organic carbon pool was constant with depth inRhizophorasoils whereas inAvicenniasoils it increased. Spectral distribution of sugars and amino acids showed a dominance of Ca-affine monomers, particularly acidic amino acids, and the sugar arabinose. Biogeochemical indicators derived from ratios of individual sugar and amino acid monomers confirm previous studies which showed that organic matter in both soils is mainly of mangrove origin. The results further suggest accumulation of organic matter inRhizophorasoils and a continuing degradation of organic matter inAvicenniasoils. The latter may thus release more nutrients to adjacent ecosystems thanRhizophorasoils. 相似文献