全文获取类型
收费全文 | 32063篇 |
免费 | 2011篇 |
国内免费 | 1928篇 |
专业分类
林业 | 3142篇 |
农学 | 3638篇 |
基础科学 | 1704篇 |
5025篇 | |
综合类 | 6716篇 |
农作物 | 1382篇 |
水产渔业 | 1751篇 |
畜牧兽医 | 9363篇 |
园艺 | 759篇 |
植物保护 | 2522篇 |
出版年
2023年 | 277篇 |
2022年 | 519篇 |
2021年 | 756篇 |
2020年 | 763篇 |
2019年 | 763篇 |
2018年 | 751篇 |
2017年 | 933篇 |
2016年 | 903篇 |
2015年 | 1055篇 |
2014年 | 1053篇 |
2013年 | 1439篇 |
2012年 | 1473篇 |
2011年 | 1664篇 |
2010年 | 1509篇 |
2009年 | 1465篇 |
2008年 | 1546篇 |
2007年 | 1600篇 |
2006年 | 1507篇 |
2005年 | 1501篇 |
2004年 | 846篇 |
2003年 | 847篇 |
2002年 | 658篇 |
2001年 | 1118篇 |
2000年 | 1140篇 |
1999年 | 1155篇 |
1998年 | 675篇 |
1997年 | 623篇 |
1996年 | 574篇 |
1995年 | 531篇 |
1994年 | 483篇 |
1993年 | 423篇 |
1992年 | 610篇 |
1991年 | 610篇 |
1990年 | 480篇 |
1989年 | 429篇 |
1988年 | 395篇 |
1987年 | 395篇 |
1986年 | 290篇 |
1985年 | 221篇 |
1984年 | 189篇 |
1983年 | 164篇 |
1982年 | 109篇 |
1981年 | 106篇 |
1980年 | 89篇 |
1979年 | 144篇 |
1978年 | 94篇 |
1977年 | 73篇 |
1975年 | 77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 15 毫秒
41.
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
42.
43.
从机体抗胃肠道线虫的黏膜免疫、胃肠道黏膜的抗原加工与递呈、胃肠道黏膜抵御寄生虫的效应机制等几方面论述了胃肠道线虫的免疫机理和免疫学研究的进展,旨在进一步阐明用免疫介入方法防治胃肠道线虫的理论基础,以解决胃肠道线虫治疗过程中的药物残留以及寄生虫的抗药性问题。 相似文献
44.
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
45.
46.
从上海光明乳业股份有限公司车间发酵罐中分离出4株酸奶噬菌体。1号噬菌体头部呈六角形,平均直径为95.1nm,头部剖面平均面积为8184.8nm^2,尾部的平均直径为18.3nm,平均长度为403.4nm;2号噬菌体头部呈六角形,平均直径为85.4nm,头部剖面平均面积为8046.2nm^2,尾部的平均直径为23.3nm,平均长度为549.4nm;3号噬菌体头部呈六角形,平均直径为95.5nm,头部剖面平均面积为9792.3nm^2,尾部的平均直径为19.8nm,平均长度为450.5nm;4号噬菌体头部呈六角形,平均直径为119.3nm.头部剖面平均面积为12586.1nm^2,尾部的平均直径为23.6nm,平均长度为520.5nm。 相似文献
47.
48.
49.
50.
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