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1.
Farm managers' decision to cull dairy cows is based on the cows' milk production, history of disorder(s), and reproductive performance, each of which affects dairy cows' lifetime (herd life and productive lifespan). We investigated the relationships among the incidence of clinical mastitis (CM), the reproductive performance, and the culling rate. We also assessed the effects of these relationships on the lifetimes of dairy cows, using the records made before and after the introduction of an automatic milking system (AMS) at Hiroshima University Farm. Milk yield, CM incidence density, and culling rate of dairy cows increased after the AMS introduction. The CM incidence was associated with an elongation of the calving interval in cows with the same parity. CM in the 1st parity might have caused the reductions of the cows' lifetime and their parity at culling. A higher age at first calving (AFC) was associated with an increase in culling rate but did not lead to a significant decrease in lifetime. Investigations of the factors mediating CM in the 1st parity or AFC with CM incidence or culling rate in the later stages might contribute to the control of lifetime of dairy cows.  相似文献   
2.
濒危中华鲟人工群体的繁殖生物学   总被引:2,自引:2,他引:0  
以1998―2008年孵出的子一代(F1)中华鲟(Acipensersinensis)为材料,研究了人工养殖中华鲟的繁殖生物学特征。结果表明:年龄10~20龄的492尾人工养殖子一代中华鲟体重为30~169 kg,体长为140~258 cm,肥满度为0.77~1.26,体长(L)与体重(W)之间的关系式为W=1×10~(–5)L~(2.9658) (R~2=0.9076,n=492)。74尾中华鲟性腺发育成熟,成熟比例为15.04%,成熟个体中雄鱼体重[(60.73±14.53)kg]和体长[(172.27±13.46)cm]均小于雌鱼体重[(88.39±29.14)kg]和体长[(193.37±18.90) cm];雄鱼最小性成熟年龄为10龄,平均为(14.96±1.93)龄,雌鱼最小成熟年龄为12龄,平均为(17.84±1.80)龄。雄鱼催产成功率为76.36%,精子快速运动时间为(49.11±13.38) s,精子寿命为(220.75±56.47)s;雌鱼催产成功率为57.89%,产卵量为(13.43±6.79)万粒,卵径(3.97±0.15)mm,卵重(0.046±0.013)g,受精率为(42.72±27.82)%,孵化率为(51.61±32.41)%,出苗量为(4.44±5.67)万尾。与野生中华鲟相比,人工养殖中华鲟成熟个体体格、繁殖力和繁殖效果均有下降趋势,人工保种面临挑战。  相似文献   
3.
Cotton producers have substantially reduced their inputs(labor, nutrients, and management) mainly by adopting a shortseason cropping management that is characterized by late sowing, high density, and reduced fertilization with one-time application at the first bloom stage without lint yield reduction. However, it has been hypothesized that one-time fertilization at an earlier growth stage could be a more effective and economic management practice. A two-year field experiment was conducted by applying five fertilizer one-time fertilization at 0(FT1), 5(FT2), 10(FT3), 15(FT4), and 20(FT5) days after the first flower appeared in the field and one three-split fertilizer application taken as the conventional control(FT6), making six treatments altogether. Cotton growth period, biomass accumulation, yield, and its formation were quantified. The results showed that the one-time fertilization did not affect the cotton growth progress as compared to FT6, however, the total crop cycles for FT3–FT5 were 3 days shorter. FT1 produced the highest cotton lint yield(1 396 kg ha–1), which was similar to the FT6 but higher than the other treatments, and could be attributed to more bolls per unit area and higher lint percentage. Cotton yield was positively correlated with cotton plant biomass accumulated. FT1 had both the highest average(VT)(193.7 kg ha–1 d–1) and the highest maximum(VM)(220.9 kg ha–1 d–1) rates during the fast biomass accumulation period. These results suggest that one-time fertilizer application at the first flower stage might be an adjustment that is more effective than at first bloom, and allowed for easier decision making for application date due to non counting of plants with flowers is needed.  相似文献   
4.
The aim of this study was to compare the nutritional composition and effects of short periods with cultivated copepod nauplii versus rotifers in first‐feeding. Atlantic cod (Gadus morhua) and ballan wrasse (Labrus bergylta) larvae were given four different dietary regimes in the earliest start‐feeding period. One group was fed the copepod Acartia tonsa nauplii (Cop), a second fed enriched rotifers (RotMG), a third fed unenriched rotifers (RotChl) and a fourth copepods for the seven first days of feeding and enriched rotifers the rest of the period (Cop7). Cod larvae were fed Artemia sp. between 20 and 40 dph (days posthatching), and ballan wrasse between 36 and 40 dph, with weaning to a formulated diet thereafter. In addition to assessing growth and survival, response to handling stress was measured. This study showed that even short periods of feeding with cultivated copepod nauplii (7 days) had positive long‐term effects on the growth and viability of the fish larvae. At the end of both studies (60 days posthatching), fish larvae fed copepods showed higher survival, better growth and viability than larvae fed rotifers. This underlines the importance of early larval nutrition.  相似文献   
5.
中国北方主产地苹果始花期模拟及晚霜冻风险评估   总被引:1,自引:1,他引:0  
建立中国北方苹果主产地苹果始花期模型,分析苹果花期晚霜冻气候风险,为有效防御晚霜冻灾害对当地苹果生产的影响提供科学指导。该研究选取中国新疆的伊宁、阿克苏、黄土高原的万荣、白水、礼泉、陕州区和渤海湾的福山、熊岳分别代表中国3大苹果产区,利用各区代表站的苹果始花期资料和同期气象数据,建立并检验了不同站点苹果始花期模型,并利用该模型重建了1962-2019年苹果始花期,分析其时空变化特征。结合晚霜冻气象指标,对苹果花期晚霜冻气候风险进行评估。结果表明:1)苹果始花期模型能够在数据独立的情况下较准确地模拟各区代表站的始花期变化,新疆、黄土高原和渤海湾苹果产区内部检验的均方根误差分别为2.5~4.8、2.4~5.0、2.3~3.0 d,交叉检验的均方根误差分别为5.0~6.6、3.4~6.0和3.6~4.1 d。2)模拟得到的苹果始花期均呈显著提前趋势,趋势系数分别为-1.84~-1.04、-3.09~-2.62和-2.37~-1.88 d/10 a。3)不同区域苹果晚霜冻气候风险有着明显的差异。新疆和黄土高原果区苹果晚霜冻气候风险指数相对较大,其中伊宁最大达2.38,其次是万荣达1.81,而渤海湾果区的福山苹果晚霜冻气候风险指数为0。新疆和黄土高原果区苹果遭受晚霜冻的影响较大,渤海湾果区受晚霜冻影响最小。  相似文献   
6.
笔者利用寿光市1961—2015年的气候资料,通过对初、终霜日期、无霜期观测资料,利用现代气候诊断分析方法,分析寿光市初、终霜日期、无霜期变化特征,科学评估初、终霜日变化对冬小麦和棉花产量的影响,为寿光农业生产防灾减灾提供参考依据。结果表明,(1)初霜日总体呈推迟趋势,终霜日呈提早趋势,无霜期延长。(2)初霜日呈推迟趋势,气候倾向率为2.23 d/10 a,1991年初霜日发生突变;(3)终霜日呈提前趋势,气候倾向率为-1.35 d/10 a。(4)无霜期日数呈增多趋势,气候倾向率为3.58 d/10 a,1994年无霜期日数发生突变。(5)初霜日和无霜期与小麦和棉花产量呈正相关,终霜日与小麦和棉花产量呈负相关,初霜日推迟比终霜日提前对小麦和棉花的产量贡献大。  相似文献   
7.
Maternal colouration based on carotenoids has been proposed to negatively affect offspring quality in several taxa, since females might trade off their limited carotenoid resources between body colouration and eggs. This study investigated in the ornamental “red cherry” shrimp (Neocaridina davidi) the relationship between maternal colouration and female reproductive performance, as well as offspring quality. Females selected displayed a broad array of body colour, from less coloured to intensely red coloured and were paired with transparent males. The first two spawning events of each female were studied and compared. The number of newly hatched juveniles was associated to maternal weight, but not to maternal colouration. Offspring quality was measured in terms of survival at the end of the 90‐day growth period, weight and length increment for 0–30 days and 30–60 days periods, and protein, lipid and glycogen contents in 30‐day‐old offspring. Yet, neither of these variables was associated to maternal colouration. These results indicate that there is no trade‐off between maternal colouration and offspring quality in this species. Furthermore, no association was found between maternal and offspring colouration, evaluated at a similar age. However, body colouration in 180‐day old females was significantly higher than in 90‐day‐old females, indicating that female colouration is strongly influenced by age.  相似文献   
8.
It is important to assess the reproductive efficiency and improve the reproductive management to promote the donkey population development. The overall foaling-related parameters of jennies under smallholder farm conditions in China were hardly under investigation. A cross-sectional survey of randomly selected 694 smallholder farms was conducted in 40 villages in the north, east, and south areas of Western Liaoning Province and Eastern Inner Mongolia Autonomous Region between March and July, 2017. Foaling-related parameters were assessed such as the mean age at first foaling, foaling rate and foaling interval during 2014–2017. Only two-thirds of the adult jennies foaled during the 3-year survey period and delivered a foal every 1.9 years. The mean age at first foaling was 45.3 months. The lowest incidence of foaling rate was in coincidence with the peak of foaling. The overall mean values for the foaling rate and foaling interval were 75% and 500.5 days, respectively. Significant changes of foaling rates before the age of 15 years and foaling intervals in the first 8 parities were not observed. The results indicate that the jennies could maintain relatively fine foaling-related parameters under smallholder farm conditions in northeast of China. However, the foaling rates hardly remained high during the whole breeding season represented a major loss to the donkey breeding.  相似文献   
9.
王鑫  马凌 《安徽农业科学》2014,(34):12330-12332,12335
我国的第一代农民工已经到了知天命的年龄,但是他们未能安享晚年,养老问题将集中爆发。首先从城镇职工养老保险的参保率低退保率高、新农保的参保率高保险待遇低、超龄务工三个方面分析了第一代农民工的境遇,其次从政府、企业、第一代农民工个体三个责任主体剖析了其深层原因,然后对第一代农民工的其他养老方式的可行性进行了分析,最后基于第一代农民工的不同去向及主要收入来源提出了对策建议。  相似文献   
10.
曾婷  赵东旭 《安徽农业科学》2014,(20):6717-6718
利用武威市观测站2005~2013年最大风速与极大风速观测数据,拟合武威市最大风速与极大风速之间关系,从而推算1980~2004年极大风速,对武威市1980年以来极大风速气候特征进行分析。结果表明,1980年以来武威市极大风速共出现4个峰值,分别出现在1984、1985、1993和2013年,尤其是1993年,极大风速达30.5 m/s,历史灾情记录显示1993年的"5.5黑风"破环力极强,给武威的农业生产带来了极大的影响,1994~2012年属于极大风速较小阶段,但由于此阶段武威市设施农业发展迅速,仍是给当地生产造成的严重的损失,利用第Ⅰ型极值分布方法推算武威市未来10、30、50、100年内可能出现的最大风速,推算结果分别为28.6、31.3、32.6、34.3m/s,在今后设施农业的规划和发展应加强大风灾害的防范。  相似文献   
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