全文获取类型
收费全文 | 19942篇 |
免费 | 1485篇 |
国内免费 | 877篇 |
专业分类
林业 | 1137篇 |
农学 | 1618篇 |
基础科学 | 745篇 |
3147篇 | |
综合类 | 3610篇 |
农作物 | 927篇 |
水产渔业 | 1367篇 |
畜牧兽医 | 7767篇 |
园艺 | 427篇 |
植物保护 | 1559篇 |
出版年
2023年 | 193篇 |
2022年 | 273篇 |
2021年 | 344篇 |
2020年 | 344篇 |
2019年 | 430篇 |
2018年 | 585篇 |
2017年 | 626篇 |
2016年 | 597篇 |
2015年 | 627篇 |
2014年 | 588篇 |
2013年 | 942篇 |
2012年 | 879篇 |
2011年 | 946篇 |
2010年 | 807篇 |
2009年 | 727篇 |
2008年 | 849篇 |
2007年 | 902篇 |
2006年 | 789篇 |
2005年 | 767篇 |
2004年 | 524篇 |
2003年 | 626篇 |
2002年 | 628篇 |
2001年 | 1003篇 |
2000年 | 873篇 |
1999年 | 733篇 |
1998年 | 264篇 |
1997年 | 246篇 |
1996年 | 202篇 |
1995年 | 223篇 |
1994年 | 216篇 |
1993年 | 163篇 |
1992年 | 364篇 |
1991年 | 382篇 |
1990年 | 309篇 |
1989年 | 294篇 |
1988年 | 286篇 |
1987年 | 332篇 |
1986年 | 254篇 |
1985年 | 194篇 |
1984年 | 175篇 |
1983年 | 150篇 |
1982年 | 96篇 |
1981年 | 85篇 |
1980年 | 83篇 |
1979年 | 142篇 |
1978年 | 96篇 |
1977年 | 74篇 |
1975年 | 78篇 |
1974年 | 79篇 |
1969年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
T N Tully S M Shane R P Poston J J England C C Vice D Y Cho B Panigrahy 《Avian diseases》1992,36(3):808-812
Eastern equine encephalitis (EEE) was diagnosed in a flock of emus in southeastern Louisiana. The outbreak involved juvenile and adult breeders ranging in age from 20 to 36 months, with an attack rate of 76% and a case fatality rate of 87%. The diagnosis was confirmed by isolation and characterization of the viral agent, and by detection of EEE antibody in two recovered emus. High mortality was preceded by marked depression, hemorrhagic diarrhea, and emesis of blood-stained ingesta. On postmortem examination, hemorrhagic enteritis and multiple petechia of viscera were observed. Microscopic changes included severe necrosis of hepatocytes, intestinal mucosa, and necrotizing vasculitis of the spleen and lamina propria of the intestine. No nervous system lesions were observed. This outbreak occurred concurrently with EEE in horses and was attributed to unseasonably heavy rainfall with an abundance of arthropod vectors and proximity to free-living reservoir host species. 相似文献
22.
23.
D E Gunson P S Sahota W O Iverson R Y Chau G M McCormick V M Traina 《Veterinary pathology》1992,29(2):145-151
Male and female Sprague-Dawley rats were given CGS 21595, a pro-drug that is almost immediately metabolized to CGS 19213, a naphthoquinone that acts as a 5-lipoxygenase inhibitor. The compound was administered by gavage to five groups of Sprague-Dawley rats (group Nos. 1, 5, n = 30; group Nos. 2-4, n = 20) at daily doses of 0, 50, 150, 500, or 1,000 mg/kg for 13 weeks. Rats in the higher dose groups had a reduced weight gain, but significant neurologic signs were not observed. A peripheral neuropathy consisting predominantly of myelin destruction in the spinal nerve roots and sciatic nerves in male rats treated with greater than or equal to 150 mg/kg CGS 21595 and in female rats treated with greater than or equal to 50 mg/kg CGS 21595 for 13 weeks. This lesion was not fully reversible after a recovery period of 4 weeks. Lesions consisted of ballooning of myelin sheaths, infiltration by macrophages, demyelination, and occasional areas of remyelination. Axons were generally preserved, and the brain and spinal cord were not affected. Male and female rats in all treatment groups had cytoplasmic hyaline droplets in the proximal renal tubules. This change was reversible after 4 weeks and was not associated with any other adverse effects on the kidney. 相似文献
24.
Mouse pronuclear stage embryos with intact slit zona pellucida (manipulated) were cultured in vitro until the hatched blastocyst stage in simplex optimized medium with higher K+ concentration (KSOM) prepared with three different water types: tap, deionized reverse osmosis (D‐O) water and Milli‐Q system (M‐Q) water. The culture media were supplemented with or without protein and ethylenediaminetetraacetic acid (EDTA, disodium salt). The rates of hatched blastocysts were significantly affected (p < 0.01) by micromanipulation, protein supplement and water source. The water source has no influence (p > 0.05) on development in EDTA‐supplemented protein‐free culture media, whereas in EDTA‐ and protein‐free culture media, the water quality significantly (p < 0.001) affected the rates of development, with higher rates in media prepared with M‐Q water. The micromanipulated embryos showed higher sensitivity to the water quality (p < 0.01). It worth mentioning that the rates of hatched blastocysts in protein‐free culture media were very low (0–7.5%). Furthermore, the three different water types were analysed by measuring the electrical conductivity, inorganic ions, total organic carbon and endotoxins to evaluate the purity. M‐Q water showed the lowest levels of inorganic ion, total organic carbon and endotoxin concentrations. We concluded that manipulated mouse embryos are good system to evaluate the quality of water used in biological system. 相似文献
25.
26.
27.
28.
姜瘟病是中国生姜生产上发生较为普遍的病害,是由青枯劳尔氏菌(Ralstoniasolanacearum)引起的。此病原菌寄主范围广,可侵染44个科300多种植物。菌体短杆状,在TZC选择性培养基上培养出现白边较宽和白边较窄的两种菌落。菌系划分为5个生理小种和5个生化型,中国的姜瘟菌主要属生理小种1号,生物型属II、III、IV。此病害是一种较难防治的土传病害,在高温、高湿、雨水多、氮肥过量的情况下发生较为严重。中国植病工作者对此病害作了大量的研究工作,对中国姜瘟病的病原菌、发病规律、及防治等研究进展作一综述。 相似文献
29.
30.
Y Maruyama Y Suzuki A Kazusaka S Fujita 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(5):493-497
The intracellular dynamics of norsalsolinol, a neurotoxin candidate causing parkinsonism-like symptoms, in PC12 cells was studied. We found that dopamine and norsalsolinol are co-localized to secretory granule layer by sucrose density gradient in norsalsolinol-treated PC12 cells. The norsalsolinol was actively taken up into isolated secretory vesicle fraction from PC12 cells with a Km value of 41.5+/-6.8 microM. The uptake of 10 microM of norsalsolinol was sensitive to reserpine (1 microM), an inhibitor of vesicular dopamine transporter, and dopamine, an endogenous substrate, but insensitive to GBR-12909, an inhibitor of dopamine transporter on plasma membrane. In norsalsolinol-treated PC12 cells, exposure to high K+ or ATP resulted in simultaneous release of norsalsolinol and dopamine. Time course of a release of dopamine and that of norsalsolinol evoked by 50 mM KCl or 100 microM ATP corresponded to each other. These releases were dependent on the concentrations of secretagogues. These data suggest that norsalsolinol is taken up with dopamine into secretory vesicle via vesicular catecholamine transporter. 相似文献