全文获取类型
收费全文 | 7413篇 |
免费 | 427篇 |
国内免费 | 1017篇 |
专业分类
林业 | 685篇 |
农学 | 965篇 |
基础科学 | 450篇 |
1109篇 | |
综合类 | 2687篇 |
农作物 | 494篇 |
水产渔业 | 357篇 |
畜牧兽医 | 1271篇 |
园艺 | 334篇 |
植物保护 | 505篇 |
出版年
2024年 | 47篇 |
2023年 | 146篇 |
2022年 | 324篇 |
2021年 | 389篇 |
2020年 | 395篇 |
2019年 | 390篇 |
2018年 | 243篇 |
2017年 | 377篇 |
2016年 | 297篇 |
2015年 | 389篇 |
2014年 | 409篇 |
2013年 | 435篇 |
2012年 | 541篇 |
2011年 | 517篇 |
2010年 | 432篇 |
2009年 | 387篇 |
2008年 | 351篇 |
2007年 | 317篇 |
2006年 | 321篇 |
2005年 | 226篇 |
2004年 | 150篇 |
2003年 | 199篇 |
2002年 | 312篇 |
2001年 | 259篇 |
2000年 | 203篇 |
1999年 | 138篇 |
1998年 | 67篇 |
1997年 | 89篇 |
1996年 | 85篇 |
1995年 | 81篇 |
1994年 | 67篇 |
1993年 | 46篇 |
1992年 | 54篇 |
1991年 | 41篇 |
1990年 | 26篇 |
1989年 | 30篇 |
1988年 | 28篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1962年 | 4篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有8857条查询结果,搜索用时 0 毫秒
201.
202.
Lingyan Zhang Xing Tao Zhang Pingting Jin Hongbo Zhao Xue Liu Qingkai Sheng 《Animal Science Journal》2021,92(1):e13593
To evaluate the effects of Spirulina platensis and probiotics on growth, immunity indexes, fecal flora, and fecal odor in mice, 40 mice were randomly allotted to four groups, and each was administrated with nothing, S. platensis, probiotics, or both for 28 days, respectively. Then, many indexes were measured. The results showed that S. platensis was more effective (P < 0.001) than probiotics in improving mice's feed conversion ration (FCR). In immunity, probiotics administration increased (P < 0.042) serum IgE, IgM, IFN-γ, colonic AHR, TLR4, and NF-κB protein expression and decreased (P < 0.039) serum IL-1α, IL-21, IL-22, and colonic ARNT gene expression. However, the S. platensis showed weaker effect, which increased (P < 0.025) the serum IgE, IgM, TNF-α, and the colonic AHR and NF-κB protein expression, and decreased (P < 0.01) serum IL-21. Probiotics consumption decreased the fecal odor by decreasing (P < 0.02) fecal Escherichia coli, indole-3-acetic acid (IAA), and skatole contents, and the S. platensis decreased (P = 0.04) the IAA. These results indicated that oral administration of probiotics, S. platensis, or both of them in mice probably benefited body's immunity and reduced fecal odor. However, their mechanisms were still unclear and need further study. 相似文献
203.
剌激断乳仔猪的食欲,提高采食量,才能最大限度地发挥断乳仔猪的生长性能。选择36头平均体重为7.36kg、30日龄的杜长大杂交断乳仔猪,按体重、公母等平均原则,随机分为对照组和试验组,对照组饲喂基础日粮,试验组在基础日粮基础上添加含5'-肌苷酸二钠(IMP)、5'-鸟苷酸二钠(GMP)的呈味核苷酸400mg/kg,试验期30d。结果显示:试验组各重复头均日采食量、头均日增重分别比对照组提高18.96%、13.61%。由此可知,添加含5'-肌苷酸二钠(IMP)、5'-鸟苷酸二钠(GMP)的呈味核苷酸能提高断乳仔猪的食欲及采食量,并改善断乳仔猪的生长性能。 相似文献
204.
205.
利用Vero-DST细胞从死亡犬、狐狸肺、脾内分离到4株犬瘟热病毒-CDV-TM-CC、CDV-Dog-SCh、CDV-Fox-SY、CDV-Fox-WF,在Vero-DST细胞上传5代没有细胞病变,5代细胞培养物经电镜、间接免疫荧光及PCR鉴定为阳性。与本实验室保存的CDV-Monkey-BJ进行基因测序,并对与致病相关的F蛋白、V蛋白进行分析,F蛋白分析5株毒具有6个潜在N-末端糖基化位点,与强毒株同源性在92%~99.7%,与疫苗株不高于93.3%,在F1亚基内有7个特有氨基酸位点,这可能与其对灵长类致病有关。V蛋白分析表明,其与强毒株同源性在94%~99.7%之间,而与疫苗株不高于93.3%,CDV-Monkey-BJ C272R突变使其Zn结合能力丧失。试验结果显示,所有分离株均为强毒株,不同宿主毒株序列存在差异,值得进一步研究。 相似文献
206.
摘要:“寿美青翠”是以自交系CU1307318为母本,自交系CU1507031为父本配制而成的水果黄瓜一代杂种。早熟,植株长势强,叶片中等,单性结实能力强;瓜长16 cm左右,无瘤,有稀刺,口感清脆,特别适合生食;干物质含量68 g/kg,可溶性固形物含量2.8%,VC含量70 mg/kg,可溶性糖含量17.1 mg/g;综合抗性强,耐低温、弱光,耐寒,高抗白粉病,抗霜霉病,中抗黄瓜花叶病毒病(CMV),每667 m2产量高达4 965.8 kg,适合保护地春、秋及越冬季节栽培。 相似文献
207.
208.
209.
Klotz JL Brown KR Xue Y Matthews JC Boling JA Burris WR Bush LP Strickland JR 《Journal of animal science》2012,90(2):682-693
As part of a 2-yr study documenting the physiologic impact of grazing endophyte-infected tall fescue on growing cattle, 2 experiments were conducted to characterize and evaluate effects of grazing 2 levels of toxic endophyte-infected tall fescue pastures on vascular contractility and serotonin receptors. Experiment 1 examined vasoconstrictive activities of 5-hydroxytryptamine (5HT), α-methylserotonin (ME5HT; a 5HT(2) receptor agonist), d-lysergic acid (LSA), and ergovaline (ERV) on lateral saphenous veins collected from steers immediately removed from a high-endophyte-infected tall fescue pasture (HE) or a low-endophyte-infected mixed-grass (LE) pasture. Using the same pastures, Exp. 2 evaluated effects of grazing 2 levels of toxic endophyte-infected tall fescue on vasoconstrictive activities of (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), BW 723C86 (BW7), CGS-12066A (CGS), and 5-carboxamidotryptamine hemiethanolate maleate (5CT), agonists for 5HT(2A),( 2B), 5HT(1B), and 5HT(7) receptors, respectively. One-half of the steers in Exp. 2 were slaughtered immediately after removal from pasture, and the other one-half were fed finishing diets for >91 d before slaughter. For Exp. 1, maximal contractile intensities were greater (P < 0.05) for steers grazing LE pastures than HE pastures for 5HT (73.3 vs. 48.9 ± 2.1%), ME5HT (52.7 vs. 24.9 ± 1.5%), and ERV (65.7 vs. 49.1 ± 2.6%). Onset of contractile response did not differ for 5HT (P = 0.26) and ERV (P = 0.93), but onset of ME5HT contraction was not initiated (P < 0.05) in HE steers until 10(-4) compared with 10(-5) M in LE-grazing steers. For Exp. 2, maximal contractile intensities achieved with DOI were 35% less (P < 0.05), whereas those achieved with 5CT were 37% greater (P < 0.05), in steers grazing HE pastures. Contractile response to CGS did not differ between pasture groups, and there was an absence of contractile response to BW7 in both groups. There were no differences between endophyte content in contractile responses after animals were finished for >91 d. Experiment 1 demonstrated that grazing of HE pastures for 89 to 105 d induces functional alterations in blood vessels, as evidenced by reduced contractile capacity and altered serotonergic receptor activity. Experiment 2 demonstrated that grazing HE pastures alters vascular responses, which may be mediated through altered serotonin receptor activities, and these alterations may be ameliorated by the removal of ergot alkaloid exposure as demonstrated by the absence of differences in finished steers. 相似文献
210.
道路交通的通达性是城市空间相互作用和经济联系的重要前提。本研究利用ArcGIS的网络分析和空间分析功能在对石羊河流域公路交通网络通达性定量评价的基础上,采用引力、潜力和场强模型对区域内7个县(区)的空间相互作用程度、城市潜力值和城市的辐射场强进行定量测度和比较分析。研究发现,凉州区对区域内城市作用力最强,城市对外相互作用潜力大,辐射带动作用强度高。区域整体上形成了以金川区、凉州区为中心的辐射中心,其对区域内其他县、区的辐射强度随交通距离增加和道路通达性降低而不断减小。 相似文献