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   1119篇
  免费   83篇
  国内免费   90篇
林业   18篇
农学   57篇
基础科学   13篇
  30篇
综合类   319篇
农作物   52篇
水产渔业   268篇
畜牧兽医   450篇
园艺   64篇
植物保护   21篇
  2024年   7篇
  2023年   27篇
  2022年   42篇
  2021年   59篇
  2020年   33篇
  2019年   45篇
  2018年   23篇
  2017年   56篇
  2016年   47篇
  2015年   54篇
  2014年   35篇
  2013年   88篇
  2012年   79篇
  2011年   86篇
  2010年   55篇
  2009年   37篇
  2008年   42篇
  2007年   46篇
  2006年   38篇
  2005年   37篇
  2004年   45篇
  2003年   35篇
  2002年   41篇
  2001年   42篇
  2000年   29篇
  1999年   39篇
  1998年   21篇
  1997年   28篇
  1996年   26篇
  1995年   12篇
  1994年   4篇
  1993年   5篇
  1992年   5篇
  1991年   6篇
  1990年   5篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1981年   1篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
排序方式: 共有1292条查询结果,搜索用时 828 毫秒
91.
【目的】 分离鉴定武汉市患皮肤病犬猫细菌性病原,并探索其对传统抗菌药物与天然活性产物藤黄酸(GA)和6-溴靛玉红-3’-肟(BIO)的敏感性。【方法】 对患皮肤病犬猫采样并分离病原,通过生长特性观察、革兰氏染色镜检、PCR等方法鉴定并利用SPF小鼠验证致病性;通过药敏纸片验证其对传统药物的耐药性,并测定天然产物对其最小抑菌浓度(minimum inhibitory concentration,MIC)值。【结果】 分离得到2株金黄色葡萄球菌、3株伪中间型葡萄球菌、2株猫葡萄球菌、1株犬链球菌及1株奇异变形杆菌。SPF小鼠皮肤创伤感染验证分离菌株均有致病性。犬链球菌及奇异变形杆菌对各自受试药物均敏感;葡萄球菌对复方新诺明、青霉素、红霉素、四环素、左氧氟沙星、苯唑西林、庆大霉素、克林霉素及氯霉素存在不同程度耐药。天然活性产物GA和BIO对上述9株菌均具有良好抑菌效果,且除分离菌株F5外GA对分离菌株的MIC值均小于BIO。【结论】 本研究共分离得到5种、9株犬猫皮肤细菌。犬链球菌、奇异变形杆菌对传统抗菌药物均敏感,部分葡萄球菌存在耐药。GA和BIO对犬猫皮肤病原菌均有明显抑菌活性,显示其可作为防控犬猫细菌性皮肤病的候选药物。  相似文献   
92.
The main purpose of this study was to investigate the changes in heat flux and temperature after the subject's palm was in contact with interior decorating materials. The relations among heat flux, temperature, and sensation of cold/warm during contact were studied. Ten men and ten women were selected and introduced to 21 materials for the contact test. They were in contact with the specimens for 30min without seeing them in a climate-controlled room at 25°±1°C and 65% RH. Changes in the heat flux and temperature of the specimens were determined by a heat flux meter. A sensory evaluation test was applied to evaluate the cold-warm contact. Results indicated that the heat flux and temperature increased with increasing time after the subject's palm was in contact with the specimens. The heat flux (Q 30) and temperature (T 30) 30min after the subject's palm contacted the specimens were greater for male subjects than for female subjects. A positive linear regression equation existed between the values for Q30 andT 30, whereas a negative linear regression formula existed the sensation of cold-warm by contact (5) and the values of ln(Q 1·). Therefore, the sensation of cold/warm by contact could be estimated simply by using the thermal physical properties of the interior decorating materials.Part of this report was presented at the International Conference on Effective Utilization of Plantation Timber, Chi-Tou, Taiwan, ROC, May 1999  相似文献   
93.
试验旨在为评价动物疯草中毒解毒治疗药物——速康解毒口服溶液的临床前应用安全性,为临床推广应用提供实验依据.用速康解毒口服溶液、赋形剂(蒸馏水)局部涂抹大白兔破损皮肤及完整皮肤,并逐日观察症状表现,统计观察结果.用速康解毒口服溶液或赋形剂、2,4-二硝基氯苯(DNCB)对大白兔多次致敏,并于2周后观察大白兔的反应.结果表明:速康解毒口服溶液对家兔完整皮肤刺激反应的平均分值为零,属于无刺激药物,对破损皮肤也无明显刺激;在过敏性实验中,给药组5只家兔中1只有轻微的过敏现象,结合致敏反应评价的分值法和致敏反应发生率,速康解毒口服溶液对家兔皮肤过敏反应的分值为0.2(1/5),致敏率为20%(1/5),具有弱致敏性.结论:速康解毒口服溶液对家兔皮肤无明显刺激性,有轻微过敏现象,属于临床安全药物.  相似文献   
94.
文章旨在研究绒山羊皮肤生物钟基因clock、tim、per1和cry1的表达模式,进而分析其在绒山羊皮肤组织中的作用及相互关系。生物钟基因形成一个转录-翻译反馈环,通过钟基因在绒山羊皮肤生长周期进行高表达,激活per1和cry1基因的转录-转化过程,从而在mRNA和蛋白水平的调控下进行有节律的表达。结果表明,这些生物钟基因在绒山羊皮肤中的表达量依次为:clocktimper1cry1;皮肤次级毛囊兴盛期,高振幅clock、per1、tim、cry1的节律表达分别出现在一天中的04∶00、08∶00、08∶00、16∶00;皮肤次级毛囊休止期,这些基因的高振幅节律表达分别出现在一天中的08∶00、04∶00、04∶00、16∶00。另外,cry1、per1基因的表达在生物钟基因正反馈循环中被激活,tim基因的表达在生物钟基因的负反馈循环中被激活。因此,clock、tim、per1和cry1调控下运行的钟基因反馈环是绒毛生长呈周期性现象的基础。  相似文献   
95.
应用间接ELISA方法,研究经嗜水气单胞菌(Aeromonas hydrophila)疫苗浸泡免疫后鳜(Siniperca chuatsi)皮肤黏液中抗体消长规律,以揭示鳜局部黏膜免疫在免疫保护中的作用及浸泡免疫的保护效果。结果表明,鳜皮肤黏液中抗体滴度在免疫后第7天达到峰值211,抗体从开始形成到消失持续21 d;添加佐剂(IMS1312、葡聚糖、莨菪碱、食盐)可以提高鳜皮肤黏液及血清中抗体滴度和相对免疫保护率,其中添加IMS1312组免疫保护率最高,达77.8%,免疫保护与抗体滴度成正相关(R2=0.79,P<0.05);以溶菌酶为代表的非特异性免疫在免疫后1周内即抗体未形成时,对鱼体起主要保护作用。此外,通过比较鳜血清与皮肤黏液中的抗体消长规律,发现血清中抗体滴度峰值出现时间较迟(第14天),抗体持续时间较长(42 d),初步推断鳜皮肤黏膜中可能存在相对独立于全身免疫系统的局部黏膜免疫系统。  相似文献   
96.
97.
根据在印度洋鸢乌贼(Symplectoteuthisluminose)渔场对鱿钓船周围水中光照度的实测数据,对5kW金属卤化物灯和5kW卤素灯的水中光照度分布进行了分析和比较。结果表明,金属卤化物灯和卤素灯光照度的衰减曲线分别为:I=28 74×e-0 0952r和I=6 29×e-0 0914r;金属卤化物灯0 01lx等光照度曲面所包含的水体体积为244 6×104m3,是卤素灯的1 67倍。以一些头足类的适宜光照度0 01~10lx为例,金属卤化物灯和卤素灯在这一光照度的诱集范围之比为1 66∶1。  相似文献   
98.
A quantitative genetic analysis was performed to study potential to breed for improved body shape, skin colour and skin spottiness of large rainbow trout in sea and fresh water production environments, and in different stages of growth. The results showed that heritabilities in both production environments were moderate for body shape and skin colour and very high for skin spots. For body shape and skin spots, genetic correlation between the two production environments was high (rA≥0.90), revealing weak genotype‐by‐environment interactions across the environments. For skin colour, genetic correlation between the environments was positive (0.78) but lower than for body shape and skin spots, indicating moderate genotype‐by‐environment interactions. Genetic correlations between 2‐ and 3‐year‐old fish were high for body shape and skin spots (rA≥0.93) and moderate for skin colour (0.85), showing that differences among families persisted strongly during growth. The positive correlations between the environments and between the ages imply that selection in fresh water environment at a single point of time should lead to favourable correlated genetic responses in the sea and at the other stages of growth.  相似文献   
99.
Immature gilthead sea bream (Sparus aurata L.) with a mean initial weight of 25.6 g were reared over 11 months to market size under different photoperiods: 16L:8D; 24L:0D and a control. Differences in final mean weight were significant between the three treatments (P<0.001): 16L:8D, 465.0 g; 24L:0D, 445.9 g; control, 402.6 g. Fish from the 24L:0D consumed most while 16L:8D fish converted it most efficiently. The lipid content of fillets was lower (P<0.05) for the 24L:0D (5.37±0.16 g 100 g?1 of fillet) than for the control (6.02±0.12 g), and the moisture content lower for the control than for either treatment groups. Skin luminosity (L*) was directly related to the number of hours of light exposure.  相似文献   
100.
Squid are short lived, with highly labile populations that respond rapidly to changes in environmental conditions. This makes them a good model for studying the response of recruitment processes to environmental signals. This study examines the influence of the Southern Oscillation Index (SOI) and Trans Polar Index (TPI) on the environment and abundance of six species of commercially important squid from the southern hemisphere, all linked to major current systems connected by the Antarctic Circumpolar Current: Dosidicus gigas (Southeast Pacific), Loligo vulgaris reynaudii (Southeast Atlantic), Nototodarus sloanii, N. gouldi (Southwest Pacific), Illex argentinus and L. gahi (Southwest Atlantic). All fisheries displayed a high level of inter‐annual variability and a degree of synchronicity was seen to occur in the abundance of the three Pacific species. The SOI signal was reflected in the environment of each fishery, particularly in Pacific regions. Both indices are correlated with squid abundance, particularly during the early life history stages (SOI) and adult stages (TPI), suggesting some degree of latitudinal separation, with juveniles potentially influenced by environmental variability at lower latitudes and adults at higher latitudes.  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