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991.
微卫星分子标记指导镜鲤群体选育   总被引:2,自引:0,他引:2  
本文用26个扩增效果好的微卫星分子标记分析了镜鲤(Cyprinus carpio L.)养殖亲本群体的遗传结构,指导其群体选育。本研究共检测到153个等位基因,片段大小为108~400 bp,平均等位基因数(A)5.8846个,平均有效等位基因数(Ne)2.8625个,平均观察杂合度(Ho)0.5063,平均期望杂合度...  相似文献   
992.
Fish are able to select a balanced diet according to their nutritional needs by choosing among incomplete feeds or even pure macronutrients. However, the relevance of both the organoleptic properties of diet and the postingestive signals that they produce remains unclear. Thus, sharpsnout seabream were allowed to select between diets containing different edible oils with their organoleptic properties masked by using gelatine capsules. Fish were fed capsules of two different colours so that they could associate the capsule colour with its corresponding postingestive effect. The longitudinal experiment included a first phase during which the fish were adapted to consuming the gelatine capsules. In a second phase, the fish were challenged with two different encapsulated diets: one comprising a complete diet containing fish oil and the other a fat‐free diet. Sharpsnout seabream showed a preference for the fish oil capsules (3.8 ± 1.1 g kg?1 body weight (BW), 66.8% of total intake) over the fat‐free capsules, showing that they were able to associate the colour of the capsule with their nutritional content through postingestive signals. After that, the fish were challenged to select between the capsules containing the fish oil diet and capsules containing a vegetable oil (linseed or soybean), in which case they showed no preference between diets (2.4 ± 0.3: 2.1 ± 0.5 g kg?1 BW of fish oil versus linseed oil capsules and 2.2 ± 0.2: 1.8 ± 0.6 g kg?1 BW of fish oil versus soybean oil capsules), indicating that the fatty acid composition of the different oils was not sufficient to affect dietary selection through postingestive signals. So, in conclusion, when orosensorial information from food is absent, the fish are able to select between diets at a macronutrient level by using postingestive information. However, this information is not sufficient for distinguishing between diets that differ in the type of oil used.  相似文献   
993.
2002-2007年在人工感染白斑综合症病毒(white spot syndrome virus, WSSV)的基础上进行一代个体选育(G1)后,对凡纳滨对虾连续进行了4代家系选育,共建立120个抗WSSV家系,感染实验结果表明:G2~G5选育家系对虾平均成活率分别为5.57%±9.83%, 8.66%±11.52%, 9.52%±8.84% 和 13.79%±12.86%;G2~ G5选育家系对虾平均成活率的变异系数分别为1.77、1.40、0.97和0.87。根据每个家系对虾的成活情况可分为敏感、中等抗性和高抗性家系,G2至G5敏感家系在各代选育家系中的比例逐年下降,分别占76.5%、55.2%、51.4%和33.3%,抗病成活率分别为0.44%±1.09%、0.78%±1.70%、2.27%±2.76%和2.44%±3.09%,感染WSSV后2~3 d出现1个急性死亡高峰;中等抗病家系在各代选育家系中的比例逐年上升,分别占0、20.7%、31.1%和38.5%,抗病成活率分别为0、9.08%±1.46%、10.7%±1.41%和11.36%±3.30%,感染WSSV后出现2个死亡高峰,第1死亡高峰值大于第2高峰;高抗家系在各代选育家系中的比例逐年上升(G4除外),分别占23.5%、24.1%、17.1%和28.2%,抗病成活率分别为22.23%±5.21%、22.7%±12.30%、24.45%±6.56%和28.98%±8.09%,感染WSSV后出现2个死亡高峰,第1死亡高峰至小于第2高峰。经连续的定向选育,选育对虾抗病性状一代比一代强,表现出明显的抗病性能,特别是高抗对虾不仅死亡率低且其死亡高峰推迟2~3d,延缓了对虾WSSV暴发的时间,但是每代每尾对虾平均产卵量逐年下降(P<0.05)。  相似文献   
994.
本文结合寒带地区的气候特点,减少施工过程的断板率,提高路面抗冻耐久性,保证路面良好的使用状态是水泥砼路面配合比设计中的重点。  相似文献   
995.
不同种源西南桦在云南景东的生长差异   总被引:5,自引:4,他引:1       下载免费PDF全文
从西南桦分布区内选择的13个种源在南亚热带山地进行筛选试验的结果表明:不同种源在生长、产量、形态 特征上都有很大差异。以胸径、树高、材积和干形等为指标,用坐标综合评定方法对13个不同种源进行综合评定, 结果表明:潞西、屏边和镇源3个种源生长和形态等各种特征都比其它种源好,位列前3名,是当地适生的好种源; 西马、龙陵和百色种源表现较好,属可利用种源;腾冲和西莲种源表现差,不好利用;平果、凭祥、靖西、景洪和田林5 种源表现一般,最好不发展。  相似文献   
996.
Occurrence of pale potato cyst nematode, Globodera pallida (Stone) Behrens, was first recorded in Japan in 2015. Among several control measures, cultivation of resistant potato (Solanum tuberosum L.) varieties is the most effective in cost and environmental impact. As no G. pallida-resistant varieties have yet been developed in Japan, great emphasis is being placed on screening of germplasm possessing the resistance and development of the resistant varieties. In this study, we first improved previously reported DNA markers linked to the G. pallida resistance loci (GpaIVsadg and Gpa5) and then used these to screen more than 1,000 germplasms to select several candidate germplasms with resistance. We performed inoculation testing on the selected candidates and identified several resistant germplasms to the Japanese G. pallida population. Furthermore, we developed a simultaneous detection method combining three DNA markers linked to G. pallida and Globodera rostochiensis (Wollenweber) Behrens resistance loci. We validated the ability of C237-I marker to select resistant allele of GpaIVsadg and predict the presence of resistance in a Japanese breeding population. Resistant germplasms identified in this study could potentially be used to develop G. pallida-resistant varieties. The marker evaluation methods developed in this study will contribute to the efficient development of resistant varieties.  相似文献   
997.
对 13个尾叶桉×细叶桉杂种、10个尾叶桉×赤桉杂种、1个尾叶桉× (尾叶桉×细叶桉 )杂种、1个尾叶桉种内控制授粉子代、5个尾叶桉母本的自由授粉子代和 1个尾叶桉×细叶桉F1自由授粉子代的比较研究表明 ,家系间树高、胸径和材积的差异均达 0 0 1显著水平。选择出优良杂种和子代 14个以及优良单株 12株。优良单株可以作为无性系比较试验的材料 ,优良杂种的优良单株可以用于建立下一世代的育种群体。这为优良杂种单株的无性系化和进一步的桉树杂交育种提供了有效的遗传材料。  相似文献   
998.
  • 1. Generalized additive models of sighting data for cetaceans collected during two surveys of waterways in the Sundarbans mangrove forest of Bangladesh indicated that Ganges River dolphin Platanista gangetica gangetica distribution was conditionally dependent (P<0.05) on low salinity, high turbidity, and moderate depth during both low and high freshwater flow; and Irrawaddy dolphin Orcaella brevirostris distribution was conditionally dependent (P<0.05) on low salinity during high freshwater flow, high and moderate depths during low and high freshwater flow, respectively; low and high‐low extremes of turbidity during low and high freshwater flow, respectively; and high temperature and increasing numbers of large–small channel confluences during low freshwater flow.
  • 2. According to sighting data collected over a 3‐year period by the captains of three nature tourism vessels, there were significant differences between the actual and expected frequencies of Ganges River dolphin sightings and individuals according to various channel types (chi‐square=64.22, P<0.0001 and chi‐square=134.14, P<0.0001, respectively, df=6) and of Irrawaddy dolphin sightings and individuals (chi‐square=15.28, P=0.0182, and chi‐square=29.42, P<0.0001, respectively, df=6), with shared preferences for wide sinuous channels with at least two small confluences or one large confluence.
  • 3. The dependency exhibited by both species for environmental characteristics associated with abundant freshwater flow, including low salinity and the availability of confluences, make them particularly vulnerable to habitat loss due to upstream water abstraction and sea‐level rise.
  • 4. Although the results of this study may not affect plans for construction in India of large‐scale, inter‐basin water transfer projects that will result in further declines in freshwater flows, or decisions within the international community about CO2 emissions affecting global sea levels, they can be used to prioritize locations where protective measures could be employed to benefit the long‐term conservation of both species.
Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
999.
1000.
The black‐lipped pearl oyster, Pinctada margaritifera, is the most important farmed species in French Polynesia and the basis of the most valuable export industry. Mass production of black pearls relies on a surgical operation requiring tissue from a donor pearl oyster to be grafted, together with a nucleus made of shell, into the gonad of a recipient oyster. Improving pearl size through family selection remains one of the main challenges for future aquaculture development. This study analyses the relative contribution of donor and recipient oysters to pearl size. To this end, hatchery‐produced donor oysters of two batches, large and small (based on shell height), were used to supply grafts for recipients, which were then monitored individually for their growth performance by recording shell height, width, and thickness, and total live weight (flesh + shells) every 6 months (four biometric measurement times) over 20 months of culture. Pearls issued from the two batches of donors showed no significant differences in nacre weight or thickness. In contrast, recipient oyster shell height and total weight were increasingly positively correlated with these pearl size parameters over the culture period, becoming significant at 8 months post‐grafting. Potential therefore exists to use shell height and oyster weight as phenotypic indicators for selective breeding of recipient oysters with high growth performance to increase pearl size in P. margaritifera.  相似文献   
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