全文获取类型
收费全文 | 64529篇 |
免费 | 3392篇 |
国内免费 | 1512篇 |
专业分类
林业 | 4250篇 |
农学 | 3612篇 |
基础科学 | 1349篇 |
7977篇 | |
综合类 | 14195篇 |
农作物 | 2792篇 |
水产渔业 | 2794篇 |
畜牧兽医 | 27238篇 |
园艺 | 1135篇 |
植物保护 | 4091篇 |
出版年
2022年 | 531篇 |
2021年 | 917篇 |
2020年 | 799篇 |
2019年 | 948篇 |
2018年 | 1043篇 |
2017年 | 1215篇 |
2016年 | 1148篇 |
2015年 | 1279篇 |
2014年 | 1329篇 |
2013年 | 2467篇 |
2012年 | 2342篇 |
2011年 | 2512篇 |
2010年 | 1911篇 |
2009年 | 1965篇 |
2008年 | 2387篇 |
2007年 | 2442篇 |
2006年 | 2278篇 |
2005年 | 2124篇 |
2004年 | 1716篇 |
2003年 | 1644篇 |
2002年 | 1529篇 |
2001年 | 1782篇 |
2000年 | 1776篇 |
1999年 | 1581篇 |
1998年 | 804篇 |
1997年 | 773篇 |
1996年 | 752篇 |
1995年 | 768篇 |
1994年 | 693篇 |
1993年 | 649篇 |
1992年 | 1106篇 |
1991年 | 1102篇 |
1990年 | 1036篇 |
1989年 | 1023篇 |
1988年 | 961篇 |
1987年 | 939篇 |
1986年 | 921篇 |
1985年 | 902篇 |
1984年 | 737篇 |
1983年 | 663篇 |
1979年 | 647篇 |
1978年 | 540篇 |
1975年 | 502篇 |
1974年 | 691篇 |
1973年 | 605篇 |
1972年 | 675篇 |
1971年 | 671篇 |
1970年 | 598篇 |
1969年 | 590篇 |
1967年 | 511篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
71.
Canine distal renal tubular acidosis and urolithiasis 总被引:1,自引:0,他引:1
D J Polzin C A Osborne F W Bell 《Veterinary Clinics of North America: Small Animal Practice》1986,16(2):241-250
Distal RTA is characterized by decreased distal renal tubular hydrogen ion secretion, decreased ability to acidify urine, hypercalciuria, hyperphosphaturia, hypocitraturia, and metabolic acidosis. Because of the resulting alterations in urine composition and pH, patients with distal RTA are predisposed to urolithiasis and renal calcification. Diagnosis of distal RTA is important because it is a potentially reversible disorder that, left untreated, may cause nephrocalcinosis, recurrent urolith formation, moderate to severe metabolic acidosis, and renal failure. 相似文献
72.
F. Baur 《European Journal of Forest Research》1868,12(1):113-120
Ohne Zusammenfassung 相似文献
73.
74.
75.
76.
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
77.
78.
Intrajugular injection of a purified E. coli lipopolysaccharide induced a biphasic fever in sheep after a latent period of 12 to 20 min. The changes in the blood flow from the liver and from the viscera drained by the portal vein were: (a) in the latent period, decreases in total hepatic blood flow (THF) due to decreased portal venous blood flow (PVF); (b) during the first febrile phase, increases in THF due to increased hepatic arterial blood flow and, (c) in the second febrile phase, increases in THF due to decreased PVF. Although there were large variations in the oxygen supply to the viscera drained by the portal vein and to the liver, there were relatively small or no changes in their oxygen consumption. 相似文献
79.
E M Aburto A Cribb I C Fuentealba B O Ikede F S Kibenge F Markham 《Canadian journal of veterinary research》2001,65(2):104-110
This study evaluates the ability of selenium (Se) supplementation to prevent experimental copper (Cu)-induced hepatocellular damage. Weanling male Fischer 344 rats were randomly assigned to groups of 15, 3 groups (A,B,C) were fed Cu-loaded diets (containing 2000 microg/g copper, added as CuSO4) and different levels of Se (added as Na2SeO3 x 5H2O) as follows: A) Cu-loaded/Se adequate diet (0.4 microg/g Se, fed basis); B) Cu-loaded/Se-supplemented diet (2 microg/g Se); and C) Cu-loaded/Se-deficient diet (< 0.2 microg/g). Three additional groups (D,E,F) were fed diets containing adequate levels of Cu (14 microg/g Cu, fed basis) and different levels of Se as follows: D) Cu-adequate/Se-adequate diet; E) Cu-adequate/Se-supplemented diet (2 microg/g Se); and F) Cu-adequate/Se-deficient (< 0.2 microg/g) diet. After 4, 8, and 12 weeks on the experimental diets, liver samples were processed for histology, histochemistry, metal analysis, glutathione peroxidase (GSH-Px) measurement, and quantification of malondialdehyde (MDA). Morphologic changes characteristic of Cu-associated hepatitis, without an increase in hepatic MDA levels, were seen in all Cu-loaded rats in each sampling. Similar changes occurred in rats fed Se-adequate, Se-supplemented and Se-deficient diets. This study demonstrates that Fischer 344 rats fed 2000 microg/g Cu develop morphologic changes due to Cu toxicity without evidence of lipid peroxidation. Furthermore, Se supplementation does not result in protection against Cu-induced liver injury. 相似文献
80.
用铬变素2R法对家蚕微孢子虫孢子染色的研究 总被引:4,自引:1,他引:3
采用铬变素 2R法 (Chromotrope 2R)染色家蚕微孢子虫 (Nosemabombycis,N .b)孢子和绿僵 (Nomuraearile yi)孢子、曲霉 (Aspergillusflavus)孢子、花粉粒 (Pollengranule)等与N .b孢子形状相似物 ,结果表明 :Chromotrope 2R法特异性地将N .b孢子染成粉红色 ,绿僵孢子、曲霉孢子、花粉粒未被染成红色 ,初步认为Chromotrope 2R法可应用于母蛾镜检的N .b鉴定 ,能明显提高N .b的检出率与准确性 ;染色N .b孢子的最佳时间与温度为 4 0min ,30℃。鉴于本染色法的条件、技术操作简便 ,染色特异性强 ,因而具有良好的应用前景 相似文献