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   217篇
  免费   18篇
  国内免费   7篇
林业   4篇
农学   11篇
基础科学   2篇
  11篇
综合类   88篇
农作物   14篇
水产渔业   106篇
畜牧兽医   4篇
园艺   1篇
植物保护   1篇
  2024年   1篇
  2023年   4篇
  2022年   4篇
  2021年   6篇
  2019年   10篇
  2018年   3篇
  2017年   7篇
  2016年   8篇
  2015年   16篇
  2014年   11篇
  2013年   19篇
  2012年   11篇
  2011年   10篇
  2010年   8篇
  2009年   5篇
  2008年   7篇
  2007年   9篇
  2006年   10篇
  2005年   9篇
  2004年   7篇
  2003年   7篇
  2002年   17篇
  2001年   17篇
  2000年   9篇
  1999年   7篇
  1998年   5篇
  1997年   6篇
  1996年   5篇
  1995年   3篇
  1988年   1篇
排序方式: 共有242条查询结果,搜索用时 203 毫秒
101.
Our examination of the neon flying squid (Ommastrephes bartramii) winter–spring cohort catch per unit effort (CPUE, an index of stock) revealed significant positive correlations with the interannual variations of observed chlorophyll‐a (Chl‐a) concentration and autumn–winter mixed layer depth (MLD) in the winter–spring feeding grounds of paralarvae and juveniles (130–170°E, 20–27°N). These correlations suggest the importance of integrated bottom‐up effects by the autumn–winter MLD for the neon flying squid stocks. However, the influence of autumn–winter MLD interannual variation in the forage availability for paralarvae and juveniles, i.e., particulate organic matter and zooplankton, has still been unclear. In this study, we use the lower trophic ecosystem model NEMURO, which uses the physical environmental data from the ocean reanalysis dataset obtained by the four‐dimensional variational (4DVAR) data assimilation method. The model‐based investigation enables us to clarify how the autumn–winter MLD controls the particulate organic matter and zooplankton abundance in the feeding grounds. Further, our investigation of the autumn–winter MLD interannual variation demonstrates that the stronger autumn wind in the feeding grounds develops a deeper mixed layer. Therefore, the deep mixed layer entrains nutrient‐rich water and enhances photosynthesis, which results in good feeding conditions for paralarvae and juveniles. Our results underline that the wind system interannual variation has critical roles on the winter–spring cohort of the neon flying squid stock.  相似文献   
102.
近几十年随着传统渔业资源量的下降,短生命周期的鱿鱼类产量出现持续增加,并已成为重要的渔获对象。由于鱿鱼类为短生命周期鱼类,对环境变化极为敏感,这一特点使得传统基于种群动力和生物学过程的资源量评估模型并不能很好地估算其资源量,为了了解环境因子和鱿鱼类资源量变化的关系,从研究方法和内容上对其研究现状进行了回顾,目前的研究已经能够在一定程度上解释环境因子对鱿鱼类资源量变化的影响机制,但是还不能完全利用环境变量来预测资源量的变化;本文还归纳了主要经济鱿鱼类栖息环境的特点,以及环境因子对其生活史各个阶段(孵化、仔稚鱼、成鱼和产卵)和资源补充量的影响,总结了目前研究遇到的问题和不足,并提出了今后研究重点应放在环境因子如何影响鱿鱼类生活史阶段中的孵化到仔稚鱼过程,从而能够提高对鱿鱼类补充量大小的估测精度,为其资源评估的进一步发展提供全面的理论基础。  相似文献   
103.
不同处理条件下柔鱼胴体特性的变化   总被引:1,自引:0,他引:1  
以北太平洋的柔鱼为原料,研究柔鱼的胴体在2℃、50℃和100℃的处理条件下,重量、水分含量及总氮量的变化。通过研究发现,去皮柔鱼胴体在2℃冷水中漂洗时,水分含量的变化是引起重量变化的主要原因,而在漂洗过程中总氮量变化不明显;带皮柔鱼胴体在50℃热水中漂洗时,漂洗水量的增加比时间的延长更有利于防止营养成分的损失;100℃漂烫时,为防止脱水及营养成分的流失,应控制在4分钟内完成。  相似文献   
104.
We compared the diet of Ommastrephes bartramii paralarvae with morphological changes in their beaks and proboscis (fused tentacles). The paralarvae were collected north of the Hawaiian Islands during 2001 and 2002 and ranged in mantle length (ML) from 1.1 to 13.2 mm. They fed on crustaceans, including copepods (copepodite stage) and amphipods. The rostral tips of upper and lower beaks began to protrude anteriorly at around 3–4 mm ML, and the smallest paralarva with identifiable prey in its digestive tract was 4.2 mm ML, which suggests that the paralarvae can masticate prey soon after the beaks protrude. The proboscis separated into two tentacles at 9.3–13.2 mm ML, but the newly formed tentacles were weakly developed even in the largest specimen, suggesting that tentacles do not operate functionally and that the arms are used to capture prey.  相似文献   
105.
徐文其 《南方水产》2011,7(6):72-76
针对鱿鱼丝这类丝条状物料,分析了带皮鱿鱼丝与脱皮鱿鱼丝单根质量分布情况等物性参数,研究了鱿鱼丝称量过程中丝条的送料状态。通过试验论证实现小包装精确称量的可行性。采用预先整理松散丝条,定量初称结合二次复秤补偿的方法,能够对小包装鱿鱼丝进行精确的自动称量。  相似文献   
106.
王亚  王春琳  詹萍萍  宋微微  母昌考  邵楚  刘帅 《水产学报》2011,35(11):1633-1639
分析了长蛸墨囊组织学及墨腺细胞的超微结构.结果表明,墨囊由墨囊体、导管和墨腺3部分组成,墨囊壁和导管壁分为外膜、肌肉层、粘膜下层和粘膜层,墨囊壁与肝脏外膜紧密相连,墨囊导管开口于直肠末端近肛门处;墨腺集中在墨囊底部靠近肝脏的一侧,由粘膜上皮细胞向囊腔内增生形成,呈索状,腺体中部含丰富的结缔组织;墨腺细胞分为具有无分泌功能的A型细胞和有分泌功能的B型细胞,微绒毛分布于B型细胞的顶端;墨汁颗粒在墨腺细胞囊泡中形成,并以胞吐或细胞破碎的形式将墨汁颗粒排出.  相似文献   
107.
Mandarin fish is a typical carnivorous fish, it can accept artificial diet after domestication, which is significantly essential to optimize its artificial diet. Nevertheless, only few studies were conducted on artificial diet of mandarin fish. Therefore, an 8‐week feeding trial was conducted to evaluate the influence of feeding stimulants on growth performance, feed intake and appetite regulation of mandarin fish. In this trial, six diets were formulated, a basal diet contained 80% of Fish Meal without feeding stimulants, named as Control, 0.4% inosinic acid meal, 0.4% L‐Alanine meal, 3% Yeast meal, 3% a commercial squid extract meal and 0.4% betaine meal were added into the basal diet to make five experimental diets, which were named as IM, AM, YM, SVO and BM respectively. At the end of feeding trial, SVO group showed higher feed intake, up‐regulated mRNA expression of neuropeptide Y (NPY) and down‐regulated mRNA expression of pro‐opiomelanocorticoid (POMC) significantly as compared to control group, which suggested that squid extract improved feed acceptability and promoted appetite in mandarin fish. Similarly, compared to control group, SVO group showed low food conversion ratio, high weight gain and SGR, indicated that squid extract enhanced the growth performance. Our results suggested that the appropriate level of squid extract addition could contribute to optimize artificial diet in mandarin fish.  相似文献   
108.
哥斯达黎加外海茎柔鱼耳石形态学分析   总被引:3,自引:2,他引:1  
贾涛  陈新军  李纲  陆化杰  刘必林  马金 《水产学报》2010,34(11):1744-1752
茎柔鱼是大洋性重要经济头足类,其耳石包含着重要的生态信息。根据2009年7-8月哥斯达黎加外海采集的茎柔鱼耳石样本,分析其耳石外部形态,探讨耳石形态差异及生长模式。研究认为,茎柔鱼左右耳石及其分区间的形态差异均不显著(P>0.05)。主成分分析认为,耳石总长(TSL)、吻侧区间长(RDL)、吻侧区夹角(RDA)可表征左耳石形态特征,TSL、吻区基线长(RBL)、RDA可表征右耳石形态特征。在整个生长过程中耳石各部分均异速生长,其形态变化趋势为整体狭长、吻区长窄、背区宽大,符合中上层头足类耳石特征。耳石生长表现为两个阶段,TSL为1 600 μm前后其耳石形态出现显著差异。RDL/TSL由上升变为下降(P<0.05),RBL生长速度迅速上升(P<0.01),RDA由下降变为上升(P<0.05),TSL=1 600 μm可作为栖息水层变化的重要标志。  相似文献   
109.
The culture supernatant of Paenibacillus sp. TKU036, a bacterium isolated from Taiwanese soils, showed high antioxidant activity (85%) when cultured in a squid pen powder (SPP)-containing medium at 37 °C for three days. Homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA) was isolated and found to be the major antioxidant in the culture supernatant of the SPP-containing medium fermented by Paenibacillus sp. TKU036. Tryptophan was also present in the culture supernatant. The results of high-performance liquid chromatography (HPLC) fingerprinting showed that HGA and tryptophan were produced via fermentation but did not pre-exist in the unfermented SPP-containing medium. Neither HGA nor tryptophan was found in the culture supernatants obtained from the fermentation of nutrient broth or other chitinous material, i.e., medium containing shrimp head powder, by Paenibacillus sp. TKU036. The production of HGA via microorganisms has rarely been reported. In this study, we found that squid pen was a potential carbon and nitrogen source for Paenibacillus sp. Tryptophan (105 mg/L) and HGA (60 mg/L) were recovered from the culture supernatant. The isolated HGA was found to have higher antioxidant activity (IC50 = 6.9 μg/mL) than α-tocopherol (IC50 = 17.6 μg/mL). The anti-inflammatory activity of the isolated HGA (IC50 = 10.14 μg/mL) was lower than that of quercetin (IC50 = 1.14 μg/mL). As a result, squid pen, a fishery processing byproduct, is a valuable material for the production of tryptophan and the antioxidant and anti-inflammatory HGA via microbial conversion.  相似文献   
110.
在今天世界文化交流的舞台上,如何将民族的传统文化地与现代的国际性视觉语言融合在一起,从而更好地展示我们独特的传统文化和民族个性,已经成为平面设计师们面临的重要课题。文章从中国传统文化构成元素中的中国书法、水墨、民俗图形、民族色彩三方面,阐述中国传统元素在现代平面设计中的应用情况,探讨如何吸收传统文化元素,应用于现代平面设计之中,形成具有民族化特色的,中国式风格的现代设计理念。  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