全文获取类型
收费全文 | 3181篇 |
免费 | 283篇 |
国内免费 | 63篇 |
专业分类
林业 | 154篇 |
农学 | 134篇 |
基础科学 | 40篇 |
85篇 | |
综合类 | 216篇 |
农作物 | 63篇 |
水产渔业 | 35篇 |
畜牧兽医 | 2739篇 |
园艺 | 16篇 |
植物保护 | 45篇 |
出版年
2024年 | 3篇 |
2023年 | 60篇 |
2022年 | 17篇 |
2021年 | 31篇 |
2020年 | 118篇 |
2019年 | 32篇 |
2018年 | 80篇 |
2017年 | 89篇 |
2016年 | 59篇 |
2015年 | 91篇 |
2014年 | 128篇 |
2013年 | 141篇 |
2012年 | 104篇 |
2011年 | 121篇 |
2010年 | 120篇 |
2009年 | 121篇 |
2008年 | 112篇 |
2007年 | 103篇 |
2006年 | 82篇 |
2005年 | 66篇 |
2004年 | 69篇 |
2003年 | 76篇 |
2002年 | 85篇 |
2001年 | 82篇 |
2000年 | 76篇 |
1999年 | 92篇 |
1998年 | 122篇 |
1997年 | 122篇 |
1996年 | 108篇 |
1995年 | 91篇 |
1994年 | 82篇 |
1993年 | 101篇 |
1992年 | 113篇 |
1991年 | 94篇 |
1990年 | 104篇 |
1989年 | 87篇 |
1988年 | 74篇 |
1987年 | 81篇 |
1986年 | 36篇 |
1985年 | 49篇 |
1984年 | 35篇 |
1983年 | 48篇 |
1982年 | 18篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有3527条查询结果,搜索用时 15 毫秒
11.
Kevin Kline PhD Leonard P. Frey PhD Jonathan H. Foreman DVM MS Joseph T. Lyman DVM MS 《Journal of Equine Veterinary Science》2005,25(8):349-354
Changes in blood gases, pH, and plasma electrolyte concentrations in response to intravenously infused sodium bicarbonate (NaHCO3) and sodium acetate (NaCH3CO2) solutions (1.34 mEq/mL) in 5 light breed mares were investigated. Jugular venous blood samples were collected before and after completion of the infusions in 20-minute intervals for 200 minutes. Infusion of sodium bicarbonate and sodium acetate caused significant (P < .00l) increases in blood pH and bicarbonate ion concentration that persisted throughout the collection period. The elevation in blood pH and bicarbonate ion concentrations was greater (P < .01) for sodium bicarbonate than for sodium acetate immediately after the completion of the infusions but was not different (P > .05) thereafter. There were significant reductions (P < .01) in plasma-ionized calcium and potassium after infusion of both sodium bicarbonate and sodium acetate. This study found that significant metabolic alkalosis in horses and corresponding shifts in electrolyte concentrations can be induced by intravenous infusion of solutions of either sodium bicarbonate or sodium acetate, and they persist for at least 3 hours. These data show that the short-term elevation in pH and bicarbonate ion concentration is momentarily higher after infusion of sodium bicarbonate. This is likely due to the direct infusion of bicarbonate ions in the sodium bicarbonate treatment, such that further metabolism is not required to be effective. However, the longer-term alkalosis did not differ between isomolar solutions of sodium bicarbonate and sodium acetate. 相似文献
12.
13.
S.G. Nykamp DVM P.V. Scrivani DVM A.P. Pease DVM MS 《Veterinary radiology & ultrasound》2004,45(1):23-28
Computed tomography-dacryocystography (CT-DCG) was used to evaluate the nasolacrimal system in four patients (three dogs and one horse) that were admitted for evaluation of chronic epiphora, facial swelling, or facial trauma. The four patients are reviewed and the technique for performing CT-DCG is described. Additionally, the indications for this procedure are discussed. CT-DCG is advantageous because cross-sectional imaging provides superior resolution of the nasolacrimal apparatus and the relatively long, small-diameter, bony nasolacrimal canal in most veterinary patients. 相似文献
14.
15.
16.
国外生物乙醇燃料生产现状和发展趋势分析 总被引:1,自引:0,他引:1
生物乙醇燃料作为清洁环保的可再生能源,正逐步受到越来越多国家的重视和积极扶持.本文介绍了生物乙醇燃料的定义及其生产原料;重点阐述了美国、巴西、欧盟等世界主要生产国家和地区的生物乙醇燃料的生产现状,以及各国政府发展生物燃料的扶持政策;并在此基础上,分析了未来生物乙醇燃料的发展趋势. 相似文献
17.
18.
19.
为了研究仔猪所吮乳汁中IgA抗体水平与乳汁中PEDV感染情况,探讨母猪免疫猪流行性腹泻疫苗后乳汁与血清中IgA、IgG抗体水平的相关性,临床采集多家规模化猪场母猪群乳汁、血清样品以及发病仔猪所吮母猪乳汁样品。采用实验室已经建立的IgA、IgG抗体ELISA方法,检测临床上猪流行性腹泻疫苗免疫后IgA抗体与IgG抗体的相关性,同时采用RT-PCR方法检测发病仔猪所吮乳汁中PEDV感染情况。结果表明,免疫猪流行性腹泻活疫苗后母猪乳汁中IgA抗体水平与血清中IgA、IgG抗体水平呈现很好的正相关性;当发病仔猪所吮母猪乳汁IgA抗体检测结果为阴性时,其PEDV抗原检测结果为阳性;乳汁IgA抗体检测结果趋于阳性样品临界值时,其PEDV抗原检测结果亦为阳性。结论:乳汁中低水平的IgA抗体很难有效地保护仔猪抵御PEDV感染;乳汁中IgA抗体与血清IgA、IgG抗体呈现很好的相关性,且乳汁中IgA抗体水平远远高于血清;通过IgG抗体水平可以间接反映乳汁中的IgA抗体水平,在初乳样品采集难度较大的情况下,可用于间接评估猪流行性腹泻免疫保护水平。 相似文献
20.
Craig A. Harms DVM James J. Hoskinson DVM David S. Bruyette DVM James W. Carpenter MS DVM Johna K. Veatch DVM PhD 《Veterinary radiology & ultrasound》1994,35(6):473-478
Thyroid scintigraphy using sodium 99m Technetium pertechnetate (99 TcO4 -) was performed in normal and radiothyroidectomized cockatiels ( Nymphicus hollandicus ). 131 I scintigraphy was performed in the course of ablating the thyroid glands. The thyroid glands in normal birds were clearly visualized, but were not individually resolvable. Thyroid glands were not visualized in thyroid-ablated birds. With 99m TcO4 scans, thyroid (or other region of interest)/body count density ratios were used for comparisons of normal and thyroid-ablated birds. Normal 99m TcO4 - thyroid/body ratios (mean +/− SD) for the dorsal and lateral views were 1.83 +/− 0.31 and 1.70 +/− 0.34 respectively. Pertechnetate thyroid/body count density ratios decreased (to 0.93 -/−0.14 and 0.88 +/− 0.12 for dorsal and lateral views respectively) after thyroid ablation, while crop/body ratios increased. 99m TcO4 - thyroid scintigraphy, therefore, was capable of detecting hypofunctional thyroid abnormalities in 131 I radiothyroidectomized cockatiels. 相似文献