全文获取类型
收费全文 | 1494篇 |
免费 | 69篇 |
国内免费 | 84篇 |
专业分类
林业 | 36篇 |
农学 | 74篇 |
基础科学 | 8篇 |
479篇 | |
综合类 | 495篇 |
农作物 | 77篇 |
水产渔业 | 76篇 |
畜牧兽医 | 364篇 |
园艺 | 13篇 |
植物保护 | 25篇 |
出版年
2024年 | 4篇 |
2023年 | 17篇 |
2022年 | 30篇 |
2021年 | 44篇 |
2020年 | 53篇 |
2019年 | 58篇 |
2018年 | 56篇 |
2017年 | 58篇 |
2016年 | 73篇 |
2015年 | 54篇 |
2014年 | 53篇 |
2013年 | 148篇 |
2012年 | 187篇 |
2011年 | 73篇 |
2010年 | 82篇 |
2009年 | 59篇 |
2008年 | 48篇 |
2007年 | 84篇 |
2006年 | 56篇 |
2005年 | 53篇 |
2004年 | 42篇 |
2003年 | 50篇 |
2002年 | 30篇 |
2001年 | 28篇 |
2000年 | 22篇 |
1999年 | 22篇 |
1998年 | 23篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 17篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 24篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1962年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有1647条查询结果,搜索用时 0 毫秒
11.
为了探索微量元素对妊娠母羊营养状况的影响,选取体重相近、年龄和胎次相同的卡拉库尔羊妊娠母羊和空怀母羊各6只,清晨采取颈静脉血样和臀部毛样,利用原子吸收光谱法对铜、锌、铁、锰4种微量元素含量进行了测定(国标法)。结果表明:血清中,铜的含量在妊娠母羊与空怀母羊之间差异显著(P<0.05);全血中,铁、铜、锰含量在妊娠母羊与空怀母羊之间差异显著(P<0.05);羊毛中,铜、锰含量在妊娠母羊与空怀母羊之间差异显著(P<0.05)。 相似文献
12.
通过温室盆栽试验,研究了铅锌尾矿污染土壤上施用有机肥、石灰2种改良剂对紫花苜蓿生长发育、产量、叶绿素含量以及重金属元素Cu、Cd、Pb、Zn积累特性的影响,并分析施用改良剂后土壤pH值和土壤中有效态重金属含量的变化。结果表明,与对照(不施加任何改良剂)相比,2种改良剂的不同施用水平均能不同程度地提高土壤pH值,显著降低土壤中各重金属有效态含量。明显抑制Cd、Pb、Cu、Zn向紫花苜蓿地上部转移,降低重金属在紫花苜蓿地上部植株中的积累。改善紫花苜蓿的生长和发育,株高、地上部鲜重和地下部鲜重、叶绿素含量均有不同程度的增加;2种改良剂的不同处理水平对紫花苜蓿地下部重金属含量的影响均达到显著水平。总体上看。当有机肥、石灰的施用量均为10g/kg土时。其改良土壤的效果最明显。 相似文献
13.
14.
采用室内培养方法,探讨了6种作物种苗对水体中锌的去除作用。分析表明,在所选择的实验条件下,采用种苗过滤可以在144h内使水体中锌浓度明显降低。在蓖麻、豌豆、向日葵等植物幼苗的根中分别积累了高达30.0mg·g-1、20.5mg·g-1和18.3mg·g-1的锌,在其茎中分别积累了7.08mg·g-1、5.89mg·g-1和7.88mg·g-1的锌。文章对实验结果进行了对比和讨论,提出选择具有“重金属超量积累倾向”的传统作物种苗进行环境水体中锌污染的植物修复,这种处理技术具有良好的应用前景。 相似文献
15.
M. Spolders S. Öhlschläger J. Rehage G. Flachowsky 《Journal of animal physiology and animal nutrition》2010,94(2):162-173
The influence of different copper and zinc contents in rations on blood serum concentrations was tested in a feeding trial at the Institute of Animal Nutrition of the Federal Research Institute for Animal Health (FLI). A total of 60 German Holstein breed cows (38 first lactating and 22 second lactating cows) were tested. All animals received a diet based on maize‐ and grass silage ad libitum. The animals were divided into two groups with 30 cows each. Group A received concentrates supplemented with copper and zinc as recommended, whereas Group B was offered a concentrate with roughly double the amount of copper and zinc. Blood samples were taken several times during the lactation. The concentrations of copper and zinc in the serum were measured and correlations between trace element intake and their serum concentrations were calculated. The mean dry matter intake was significantly higher for cows in the second lactation (19.1 kg/day) than for cows in the first lactation (16.4 kg/day), whereas the DM‐intake was constant in the different feeding groups (17.3 and 17.4 kg/day). The correlation between feed intake in the first and the second lactation was r = 0.76. The copper concentration in the serum was not influenced by the different feedings (11.9 and 12.5 μmol/l), but high variations were found between the cows. The influence of the lactation number was not significant (12.1 and 12.4 μmol/l). In contrast to copper, the zinc concentration in the serum was significantly higher for Group B (14.0 μmol/l) than for Group A (12.2 μmol/l), respectively, for second lactating cows (13.8 μmol/l) in relation to 12.7 μmol/l for first lactating cows. The individual variation was also high as for copper. Neither the correlation between copper intake and copper serum concentration nor the correlation between zinc intake and zinc serum concentration was significant. 相似文献
16.
本试验采用3×3因子设计,将日粮苜蓿草粉比例设为10%、20%、30%三个水平、蛋白质设为15.83%、14.01%、12.74%三个水平。选用180只12月龄健康产蛋豁鹅,随机分为9组,每组20只,试验期20d。研究日粮苜蓿草粉比例和蛋白水平及二者交互作用对豁眼鹅蛋黄铁锌含量的影响。结果表明,苜蓿草粉比例增加使蛋黄铁含量呈降低趋势,而日粮蛋白质水平对蛋黄铁含量无显著影响;日粮苜蓿草粉比例和蛋白质水平的交互作用对蛋黄铁含量无显著影响(P〉0.05)。苜蓿草粉比例增加使蛋黄锌含量呈增加趋势,而日粮蛋白质水平 相似文献
17.
【目的】在受白粉病菌侵染的中国野葡萄叶片中克隆锌指蛋白基因全长,研究葡萄抗白粉病的分子机制。【方法】在前期采用mRNA差异显示技术获得的中国野葡萄华东葡萄株系白河35-1抗白粉病基因表达差异cDNA片段T11GG/B0324-292的基础上,利用cDNA末端快速扩增(RACE)技术克隆了该cDNA全长序列,并结合生物信息学方法对所获取的序列进行分析。【结果】该cDNA全长2663bp(GenBank登录号HM008621),具有完整的开放阅读框,基因全长2223bp,编码1个由740个氨基酸组成的锌指蛋白(Zinc finger protein),5′和3′非翻译区长度分别为395和44bp。多重比较分析表明,该基因推导的氨基酸序列与拟南芥、蒺藜苜蓿、水稻的C3H亚型CCCH型锌指蛋白的同源性分别为61%,70%和60%。【结论】利用RACE技术获得了锌指蛋白基因全长,为进一步研究锌指蛋白基因与葡萄抗白粉病的关系奠定了基础。 相似文献
18.
施用锌肥和硼肥对玉米穗粒性状和品质的影响 总被引:6,自引:0,他引:6
为了探究微量元素锌和硼对玉米果穗的影响,以豫单606为材料,采用盆栽试验,设置不施用锌肥和硼肥(对照,CK)、施用锌肥、施用硼肥、同时施用锌肥和硼肥4种处理,调查了玉米穗粒性状和品质的变化。结果表明,施用锌肥和硼肥,秃尖减少,行粒数增加,产量显著提高;施用锌肥籽粒长度增加,粒厚、百粒体积和百粒重降低,由于穗粒数提高,单穗产量增加;施用硼肥籽粒长度、百粒重、百粒体积和单穗产量均增加。与CK相比,单施锌肥、硼肥及锌肥和硼肥配施均能提高籽粒蛋白质含量;施用锌肥籽粒脂肪含量显著提高,施用硼肥籽粒脂肪含量降低;各施肥处理淀粉含量均无显著差异。与CK相比,施用锌肥或硼肥以及锌肥和硼肥配施显著提高了籽粒锌和硼的含量。本研究结果为锌肥和硼肥在玉米生产中的应用提供了参考。 相似文献
19.
Organic zinc and copper supplementation on antioxidant protective mechanism and their correlation with sperm functional characteristics in goats 下载免费PDF全文
M Narasimhaiah A Arunachalam S Sellappan VK Mayasula PR Guvvala SK Ghosh V Chandra J Ghosh H Kumar 《Reproduction in domestic animals》2018,53(3):644-654
Trace minerals feeding had significant effects on sperm production and fertility with better absorption and proper utilization within the body for optimum reproductive function. Several studies have shown that more influenced trace elements in the diets of animals are copper (Cu) and zinc (Zn). Bucks showing deficiency of this mineral might affect the quality of semen production which in turn would affect the fertility. This experiment was thus designed to test the effects of organic Cu and Zn supplementation on antioxidants enzyme activities and sperm functional attributes in fresh semen of bucks. Forty bucks (n = 40, Aged 5 months) were assigned to ten groups of four animals in each group, supplemented (for a period of 8 months) with different levels of organic Zn: 20 mg (T2), 40 mg (T3) and 60 mg (T4), organic Cu: 12.5 mg (T5), 25 mg (T6), 37.5 mg (T7) and combined organic Zn and Cu: 20 + 12.5 mg (T8), 40 + 25 mg (T9), 60 + 37.5 mg (T10), respectively, per kg dry matter and no additional mineral diet (control; T1). One hundred and sixty semen samples were collected through electro‐ejaculator and analysed for sperm quantity, quality, acrosome intactness and plasma membrane integrity and correlated with the catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase enzyme activities in seminal plasma. The results indicated organic Cu and zinc supplemented bucks produced more sperm cells, had higher sperm concentrations, maintained higher (p < .01) sperm livability, plasma membrane and acrosome integrities, more motility and velocity. The increased antioxidant enzyme activities, reduced oxidative stress and lowered lipid peroxidation were positively correlated (p < .05) with the sperm functional attributes. In conclusion, organic Cu and Zn supplement to male goats showed protective roles against oxidative damage and maintained better fresh semen characteristics. 相似文献
20.