全文获取类型
收费全文 | 310篇 |
免费 | 18篇 |
国内免费 | 30篇 |
专业分类
林业 | 8篇 |
农学 | 6篇 |
基础科学 | 13篇 |
40篇 | |
综合类 | 67篇 |
农作物 | 9篇 |
水产渔业 | 184篇 |
畜牧兽医 | 14篇 |
园艺 | 9篇 |
植物保护 | 8篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 8篇 |
2017年 | 13篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 23篇 |
2013年 | 27篇 |
2012年 | 25篇 |
2011年 | 24篇 |
2010年 | 15篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 18篇 |
2006年 | 25篇 |
2005年 | 14篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1987年 | 4篇 |
排序方式: 共有358条查询结果,搜索用时 15 毫秒
91.
针对太阳能水蒸发技术中的关键核心光热转化材料存在太阳能利用率不高、价格昂贵且制备工艺复杂等问题,该研究提出以农业废弃物玉米芯为生物质原材料制备玉米芯生物炭饼,探究了热解温度对其理化性质的影响及其在太阳能水蒸发中的应用性能。结果表明,玉米芯生物炭(Corncob Biochar,CB)的理化性质受热解温度的影响明显,随着热解温度升高,CB逐渐由大孔主导转向微孔/介孔主导,CB的热稳定性增强,对光的吸收增强。在一个太阳光照强度下(1 kW/m),CB的太阳能水蒸发速率和表观能量利用率随CB热解温度的升高而增大;相较于250和450℃,650 ℃制备的玉米芯生物炭(CB650)具有最高的水蒸发速率(4.16 kg/(m2·h))和表观能量利用率(97.8%);CB650高效太阳能水蒸发性能主要基于其具有较高的光吸收能力(润湿条件下达96.4%)及以微孔为主的孔隙结构通过毛细管力提供适当的水传输,Li离子蒸发试验证实其水蒸发机制为小水团簇形式蒸发。此外,CB650不仅表现出一定的耐用性,且对海水、重金属和染料废水具有优异的水蒸发处理效果。研究结果不仅为玉米芯的资源化和减量化处置提供了新的技术途径,亦为其在太阳能水蒸发技术中的应用提供了必要的理论和技术依据。 相似文献
92.
杂交笛鲷人工繁育技术的初步研究 总被引:6,自引:2,他引:4
红鳍笛鲷(♀,40尾)×千年笛鲷(♂,45尾)杂交,得到受精卵2.2kg,浮卵率为78.57%,受精卵的孵化率为90.51%,共得到健康仔鱼349.2万尾;千年笛鲷(♀,30尾)×红鳍笛鲷(♂,28尾)的杂交,不成功。在水温27.5~33.5℃、盐度27.5~32.5、pH7.6~8.3、溶解氧4~6 mg/L条件下,杂交笛鲷仔鱼经过32 d的培育,用3个育苗池塘(面积共0.933 hm2)培育出平均全长36.8 mm的幼鱼44.4万尾,单位面积培育鱼种47.57万尾/hm2,育苗成活率为8.95%。 相似文献
93.
ONPG单管定量检测法与国标法在检测海水中大肠菌群的比较研究 总被引:1,自引:0,他引:1
本实验室根据ONPG显色技术原理建立了大肠菌群单管定量检测技术,即在此基础上利用ONPG单管定量检测方法和国标法对实验室制备的标准菌的菌悬液和水样进行检测,对2种方法的检测结果进行比对.研究结果显示:两种方法对菌悬液、水样的检测结果无统计学差异,ONPG单管定量检测方法检测数据的准确性、精确性和重现性都高于国标法;ON... 相似文献
94.
Red and white muscle from specimens of wild and farmed gilthead sea bream (Sparus aurata) were analyzed for histochemical ATPase activity, total protein content, fatty acids, trace element concentrations and myosin isoforms. The fibre type composition of muscle samples was confirmed histochemically by the ATPase reaction, which did not show any differences between the two groups of animals. Myosin ATPase activities, myosin and protein yields were significantly higher in white muscle than in the red muscle and for the red muscle the latter two parameters were higher in wild fish. Fatty acid profiles revealed differences between the two groups of animals, probably because of the fatty acid composition of the diets. Zinc, copper and iron concentrations were higher in red muscle than in white muscle; muscles from wild fish were significantly richer in trace elements. No separation of fast and slow heavy chains of myosin could be obtained on SDS-gel electrophoresis, but two dimensional electrophoresis revealed the presence of three light chains in white muscle (LC1F, LC2F, LC3F), and two main types in red muscle (LC1S, LC2S). Small, variable percentages of LC3F were found in the red muscle samples, especially in the wild fish. It is concluded that the different environmental conditions, experienced by wild and farmed fish, have significantly influenced the biochemical composition of their lateral muscle. 相似文献
95.
The sensitivity of Oreochromis mossambicus to Clostridium botulinum toxin types A–E was investigated. All five toxin types were toxic to O. mossambicus. In the case of toxin types A–D, O. mossambicus was considerably more resistant than mice and, in the case of type E toxin, fish were more sensitive. The minimum intraperitoneal (i.p.) dose of type E toxin for fish was half the minimum lethal dose for mice. The results of the study suggest that good hygiene should be maintained in fish/shrimp farms to keep contamination at a low level. 相似文献
96.
Halil Kurban Hirofumi Saneoka Kunito Nehira Rahmutulla Adilla Kounosuke Fujita 《Soil Science and Plant Nutrition》2013,59(4):589-597
The response of two leguminous plants Alhagi pseudoalhagi and Vigna radiata to seawater salinity was studied over a period of 30 d. The growth of Vigna radiata was markedly and gradually reduced by increasing salinity levels, whereas that of Alhagi pseudoalhagi was promoted at 9.1 and 16.2 dS m-1 salinity but then was slightly reduced at 28.2 dS m-1 salinity. These results indicate that Alhagi pseudoalhagi belongs to the group of halophytic plants. Seawater salinity caused changes in the membrane permeability measured as electrolyte leakage in both plants. Alhagi pseudoalhagi maintained a lower membrane permeability than Vigna radiata. With increasing salinity levels, the membrane permeability decreased in Alhagi pseudoalhagi, whereas, in Vigna radiata it slightly increased at 9.1 dS m-1. The leaf water potential and the osmotic potential decreased in both plants along with the seawater salinity levels. However, the turgor potential and osmotic adjustment in Alhagi pseudoalhagi were maintained at a higher level than in Vigna radiata. The contributions of organic and inorganic solutes to the osmotic adjustment differed: Alhagi pseudoalhagi achieved osmotic adjustment through Cl- and Na+ uptake from the substrate, while the contribution of K+, Ca2+, and organic solutes to the osmotic adjustment was limited. These results suggest that the differences in salt tolerance between Alhagi pseudoalhagi and Vigna radiata can not be due to differences in specific-ion effects, but may be related to some factors involved in membrane permeability and osmotic adjustment. 相似文献
97.
Z. Zhang K. A. Glover V. Wennevik T. Svåsand A. G. E. Sørvik P. Fiske S. Karlsson Ø. Skaala 《Fisheries Management and Ecology》2013,20(1):42-51
Microsatellite DNA analysis and statistical assignment methods were implemented to identify the origin of 190 farmed escaped Atlantic salmon recaptured over a period of 2 months at a netting station located in Trondheim fjord, Norway. Samples were also collected from farms within the region. The escapees originated from a minimum of two sources, separated in time of capture at the netting station. The majority of the escapees captured in the early period probably originated from a single farm within the region, while escapees captured in later period probably originated from multiple farms, including from outside of the region. Biological data from the escapees supported these conclusions. This study serves to exemplify the use of genetic methods to assist fisheries management. 相似文献
98.
海水入侵和土壤盐渍化是海岸带重要的地质灾害类型之一。本文报告了2008—2010年福建省漳州市漳浦县海岸带海水入侵和土壤盐渍化状况及趋势监测结果。在漳浦县旧镇和霞美镇离岸1.4~3.9 km的监测过渡区范围,地下水(水井水)的Cl-含量为1 200~5 030 mg/L,矿化度含量为2.20~13.97 g/L,全部Cl-含量和大部分矿化度指标超过严重入侵标准值,表明监测区发生严重海水入侵。梅宅村断面过渡区,枯水期发生不同程度土壤盐渍化,但在丰水期恢复成非盐渍化;刘板村断面过渡区,除2009年丰水期监测到氯化物—硫酸盐型中盐渍化土,其他全部为非盐渍化,但在2008年和2009年枯水期,分别在离岸最远的非盐渍化区,监测到硫酸盐—氯化物型盐土和氯化物—硫酸盐型中盐渍化土,表明监测区土壤盐渍化总体较轻,但缺乏明显规律性,有待进一步监测与研究。 相似文献
99.
海水胁迫对5种生态型菊芋生理生化的影响 总被引:4,自引:0,他引:4
Three treatments consisting of 0%, 15%, and 30% seawater were investigated to analyse the ecotypic variabilities among five populations of Jerusalem artichoke (Helianthus tuberosus)regarding their responses to seawater stress under a hydroponic culture system. Analyses were done 2, 4, and 6 days after treatments. The 15% and 30% seawater treatments reduced the growth rates of roots and shoots of H. tuberosus populations. The activities of superoxide dismutase, peroxidase, and catalase majored in the leaves were stimulated under the seawater stress. The electrolyte leakage and malondialdehyde contents of the leaves were also stimulated owing to seawater stress. The contents of proline and soluble-sugars in the leaves increased significantly with increasing seawater concentrations. The concentrations of Na+, K+, and Cl- in the aerial parts and roots increased with an increase in the seawater concentration throughout the experimental period. There were ecotypic differences among the five populations of H. tuberosus as evidenced by the analyses of the above items in both aerial parts and roots under seawater treatment. The magnitude of the ecotypic variance components indicated that a substantial proportion of the total variation for these physiological and biochemical responses were owing to ecotype, indicating the possibility of improvement through hybridization and selection. 相似文献
100.