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   3258篇
  免费   187篇
  国内免费   236篇
林业   96篇
农学   146篇
基础科学   42篇
  125篇
综合类   1180篇
农作物   89篇
水产渔业   260篇
畜牧兽医   1631篇
园艺   61篇
植物保护   51篇
  2024年   16篇
  2023年   45篇
  2022年   112篇
  2021年   137篇
  2020年   125篇
  2019年   146篇
  2018年   91篇
  2017年   218篇
  2016年   186篇
  2015年   181篇
  2014年   148篇
  2013年   162篇
  2012年   264篇
  2011年   261篇
  2010年   184篇
  2009年   198篇
  2008年   142篇
  2007年   163篇
  2006年   132篇
  2005年   123篇
  2004年   82篇
  2003年   65篇
  2002年   48篇
  2001年   45篇
  2000年   56篇
  1999年   44篇
  1998年   25篇
  1997年   32篇
  1996年   28篇
  1995年   33篇
  1994年   21篇
  1993年   21篇
  1992年   28篇
  1991年   16篇
  1990年   14篇
  1989年   15篇
  1988年   9篇
  1987年   12篇
  1986年   8篇
  1985年   5篇
  1984年   6篇
  1983年   2篇
  1982年   2篇
  1981年   3篇
  1980年   7篇
  1979年   4篇
  1978年   3篇
  1976年   3篇
  1975年   5篇
  1956年   2篇
排序方式: 共有3681条查询结果,搜索用时 31 毫秒
61.
To study the effect of weaning stress on dairy buffalo calves,5 healthy calves were chosen and weaned,and the blood samples were collected at 1 day before weaning,and 1,14 and 21 days after weaning to analysis blood physiology and biochemistry indexes and immune function.The results showed that the count of white blood cell,lymphocyte,erythrocyte,monocytes and hematocrit,aspartate aminotransferase activity,blood glucose,cortisol and immunoglobulin G contents of dairy buffalo calves were no significant difference between before and after weaning treatments (P > 0.05).The count of neutrophils at 21 d after weaning were significantly lower than that of 1 d before weaning of dairy buffalo calves (P < 0.05).However,lactate dehydrogenase and alanine aminotransferase activity in weaned treatments were significantly higher than those of animals in the treatment before weaning (P < 0.05).The serum urea nitrogen of dairy buffalo calves at 21 d after weaning was significantly higher than that of 1 d before weaning (P < 0.05) and hemoglobin content at 21 d after weaning was significantly lower than that at 1 day before weaning (P < 0.05).It indicated that the physiological and immunity function of dairy buffalo calves were challenged under weaning stress.  相似文献   
62.
This experiment was conducted to investigate the effects of complex nutritional regulation additives on growth performance, slaughter performance and serum biochemical indexes of grazing sheep in cold season.A single factor random block design was used and 48 grazing ewes with the average weight (28.01±1.70) kg and 7 months old were randomly divided into 4 groups:Group Ⅰ without supplement;Group Ⅱ with concentrate;Group Ⅲ with concentrate+complex formulation 1 (0.30% malic acid, 0.06% cysteamine, 0.08% saccharicterpenin);Group Ⅳ with concentrate+complex formulation 2 (0.60% malic acid, 0.12% cysteamine, 0.16% saccharicterpenin)with 3 replicates per group and 4 grazing ewes per replicate.The results showed that:①The final weight of group Ⅲ was the highest and higher than group Ⅱ and Ⅳ by 6.26% (P>0.05)、3.69% (P>0.05), respectively.The average daily gain of group Ⅲ was highest, and higher than group Ⅱ and Ⅳ by 26.32% (P<0.01)、5.74% (P>0.05) respectively.②Comparing with group Ⅱ, the slaughter rate of group Ⅲ was increased by 4.68% (P>0.05).Compared with groupⅠ, Ⅱ and Ⅳ, the meat percentage of group Ⅲ was increased 18.46% (P<0.05), 10.97% (P>0.05) and 4.40% (P>0.05), while the net meat weight of carcass in group Ⅲ was increased by 49.74% (P<0.01), 13.22% (P>0.05) and 18.27% (P<0.05), respectively.Compared with groupⅠ, Ⅱ and Ⅳ, the net meat rat of carcass in group Ⅲ was increased 10.42% (P<0.01)、6.00% (P>0.05) and 3.37% (P>0.05), respectively.③There was a rising trend as the order of groupⅠ, Ⅱ, Ⅳ and Ⅲ in serum glucose, Ca, P, HDL, LDL, GPT and IgG, while A/G and TG showed a decreasing trend.Based on the above results, in this trial, supplementing complex nutritional regulation additives had good effects on growth performance, slaughter performance and serum biochemical indexes of grazing sheep in cold season.And supplementing complex formulation group 1 (group Ⅲ) was the best.  相似文献   
63.
64.
This study was conducted to investigate the impacts of deoxynivalenol (DON) feeding either alone or in combination with a microbial feed additive (MFA) on the immune response to a viral vaccine and serum clinical chemical parameters. Forty 1‐day‐old boiler chicks were weighed and randomly divided into four groups, 10 birds in each group: (i) control group fed with basal diet; (ii) DON group fed with basal diet artificially contaminated with 10 mg DON/kg feed; (iii) DON + MFA group fed with basal diet contaminated with 10 mg DON/kg feed and supplemented with 2.5 kg of MFA/ton feed; and (iv) MFA group fed with basal diet supplemented with 2.5 kg of MFA/ton feed. At 35 days of age, birds were slaughtered and blood was collected for investigating the antibody titre against infectious bronchitis virus (IBV) and clinical chemical parameters. The results showed that DON reduced (p = 0.032) the titre against IBV, decreased (p = 0.005) the level of alanine transaminase (ALT) (4.2 ± 0.5 U/l) compared with control birds (6.4 ± 0.5 U/l), increased (p = 0.002) the serum cholesterol concentration (144 ± 6 mg/dl) compared with their control counterparts (123 ± 5 mg/dl) and increased (p = 0.074) the amount of circulating triglycerides (62.25 ± 7.50 mg/dl) compared with controls (39.55 ± 4.74). These results indicate that dietary DON altered the humoral immune response to viral vaccine and affected the serum clinical biochemistry. However, DON in combination with MFA did not affect serum IBV titre. Taken together, DON in the feed of broilers produced an impairment of the success of IBV vaccine and affected the health of birds.  相似文献   
65.
This trial was conducted in a 2 × 3 + 1 factorial arrangement based on a completely randomized design to evaluate the effects of different dl ‐selenomethionine (dl ‐Se‐Met) and sodium selenite (SS) levels on growth performance, immune functions and serum thyroid hormones concentrations in broilers. A total of 840 Ross 308 broilers (7 days old) were allocated by body weight to seven treatments (three replicates of 40 birds each treatment) including (1) basal diet (containing 0.04 mg of selenium (Se)/kg; control) without supplementary Se; (2, 3 and 4) basal diet + 0.05, 0.15 or 0.25 mg/kg Se as SS; (5, 6 and 7) basal diet + 0.05, 0.15 or 0.25 mg/kg Se as dl ‐Se‐Met. The experiment lasted 42 days. The results revealed that dietary Se supplementation improved (p < 0.05) average daily gain, feed efficiency, immune organ index, serum immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM) and triiodothyronine (T3) concentrations and decreased (p < 0.01) thyroxine (T4)/T3 ratio in serum compared with the control. Broilers receiving the dl ‐Se‐Met‐supplemented diets had higher (p < 0.05) feed efficiency, thymus index, the amounts of IgA, IgG, IgM and T3 as well as lower (p < 0.05) serum T4 concentrations and T4/T3 ratio than those consuming the SS‐supplemented diets. Serum IgA and IgM levels of broilers fed 0.15 mg Se/kg were significantly higher (p < 0.05) than those of broilers fed 0.05 or 0.25 mg Se/kg. In summary, we concluded that dl ‐Se‐Met is more effective than SS in increasing immunity and promoting conversion of T4 to T3, thus providing an effective way to improve the growth performance of broilers. Besides, based on a consideration of all experiment indices, 0.15 mg Se/kg was suggested to be the optimal level of Se supplementation under the conditions of this study.  相似文献   
66.
[目的] 研究不同驱虫药对伊犁马血液生化指标的影响,为伊犁马科学驱虫及健康养殖提供参考。[方法] 将平均体重(265.5±35.6)kg、出生日期相近的40匹1岁伊犁马随机分为5组,每组8匹,分别为对照组、试验Ⅰ组、试验Ⅱ组、试验Ⅲ组和试验Ⅳ组。在相同的饲养管理和日粮营养水平条件下,对照组不驱虫,在试验开始第1天,试验Ⅰ组使用伊维菌素驱虫,试验Ⅱ组使用吡喹酮驱虫,试验Ⅲ组使用阿苯达唑驱虫,试验Ⅳ组使用伊维菌素和阿苯达唑的混合药剂驱虫;在试验第14天采集马匹血液样品,测定血浆氮代谢指标、葡萄糖及酶相关指标、脂代谢指标及金属离子指标。[结果] ①试验Ⅲ组总蛋白(TP)浓度最低,与对照组、试验Ⅰ组、试验Ⅱ组及试验Ⅳ组相比,分别降低了8.16%、7.15%、4.98%及6.62%(P>0.05)。对照组及各试验组白蛋白(ALB)、尿素(UREA)浓度均无显著(P>0.05)差异。与对照组相比,试验Ⅲ组及试验Ⅳ组血浆中UREA浓度分别降低了33.15%及36.10%(P>0.05)。②与对照组相比,试验Ⅰ组、试验Ⅱ组、试验Ⅲ组、试验Ⅳ组丙氨酸氨基转移酶(ALT)活力分别降低了26.51%、21.11%、47.14%及52.38%(P>0.05)。试验Ⅲ组血浆中碱性磷酸酶(ALP)活力低于对照组,降低了0.19%(P>0.05)。与对照组相比,试验Ⅱ组和试验Ⅳ组的乳酸脱氢酶(LDH)活力显著(P<0.05)升高,分别提高了17.84%、13.51%;谷草转氨酶(AST)活力分别提高了5.40%和4.08%(P>0.05)。③对照组血浆中甘油三酯(TG)、肌酐(CREA)及尿酸(UA)的含量与各试验组相比均无显著(P>0.05)差异。试验Ⅰ组及试验Ⅳ组血浆中CREA浓度较对照组分别提高13.38%和9.86%(P>0.05)。试验Ⅱ组血浆中胆碱酯酶(CHE)活力显著(P<0.05)高于试验Ⅲ组,提高了17.70%。④对照组血浆中Mg2+浓度与各试验组相比差异不显著(P>0.05);试验Ⅲ组血浆中Ca2+浓度最低,与对照组、试验Ⅰ组、试验Ⅱ组及试验Ⅳ组相比,分别降低了23.44%、16.40%、25.89%及21.43%(P<0.05)。[结论] 综合来看,使用伊维菌素和阿苯达唑混合驱虫,对伊犁马血浆中的氮代谢、糖脂代谢指标及肝功能代谢酶活力改善效果更明显。  相似文献   
67.
本试验旨在研究饲粮添加过瘤胃半胱氨酸对育成期梅花鹿生长性能、营养物质表观消化率和血清生化指标的影响。采用单因素随机区组试验设计,将12头7月龄雄性梅花鹿仔鹿分为4组(每组3个重复,每个重复1只),组间体重差异不显著。对照组(Ⅰ组)饲喂基础饲粮,试验组分别饲喂额外添加1.25(Ⅱ组)、2.50(Ⅲ组)和5.00 g·kg-1(Ⅳ组)过瘤胃半胱氨酸(有效成分51.70%)的试验饲粮。试验预饲期15 d,正试期112 d。结果表明,1)与Ⅰ组相比,添加过瘤胃半胱氨酸Ⅲ组总增重和平均日增重显著提高(P<0.05),Ⅲ组料重比显著降低(P<0.05);2)与Ⅰ组相比,添加过瘤胃半胱氨酸各组粗蛋白质、钙和磷表观消化率显著提高(P<0.05),Ⅲ组干物质和有机物表观消化率显著提高(P<0.05);3)与Ⅰ组相比,添加过瘤胃半胱氨酸Ⅱ组和Ⅲ组甘氨酸表观消化率显著提高(P<0.05),各组半胱氨酸、蛋氨酸、丝氨酸、赖氨酸、苏氨酸、缬氨酸、异亮氨酸、亮氨酸、精氨酸、苯丙氨酸、组氨酸、天冬氨酸、酪氨酸、谷氨酸、丙氨酸和脯氨酸表观消化率显著提高(P<0...  相似文献   
68.
Brans of 23 traditional and 12 improved (both red and white) rice varieties in Sri Lanka were screened for anti-amylase and anti-glycation activities in vitro. Varieties which showed the highest inhibitory activities at screening were further investigated for anti-glucosidase and glycation reversing as anti-diabetic properties. The same varieties were studied for selected antioxidant properties. Significantly high anti-amylase and anti-glycation activities were observed for bran extracts of red varieties compared to white varieties at screening. Traditional red rice varieties, Masuran, Sudu Heeneti, Dik Wee and Goda Heeneti, exhibited significant and dose dependent anti-amylase, anti-glycation and glycation reversing activities. These varieties also showed marked antioxidant properties. It is concluded that brans of Sri Lankan traditional red rice varieties Masuran, Sudu Heeneti, Dik Wee and Goda Heeneti may be potential food supplements for diabetes.  相似文献   
69.
选用不同的高压静电场处理参数。采用U5(5^4)均匀设计安排试验。对刺青瓜种子进行电场处理,测定其发芽期的发芽势、发芽率、SOD、VC、MDA等生化指标变化,并建立了相应的数学模型,寻找出刺青瓜种子的最佳静电场处理参数。  相似文献   
70.
针对精密排种器性能指标统计分析中存在统计计算工作量大,且为重复性工作,人工计算耗时多,又难以保证计算准确性和结果可靠性的现实问题,研究开发了一种基于Visual C 能实现与Excel进行数据链接的精密排种器性能指标统计分析软件。研究得出该系统界面友好,与Excel数据链接方便,具有自动导入试验数据、保存和查找计算结果及比较分析试验结果的功能。此软件可大大地提高计算效率,保证数据处理的可靠性和计算结果的准确性。  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