全文获取类型
收费全文 | 207118篇 |
免费 | 11055篇 |
国内免费 | 143篇 |
专业分类
林业 | 8672篇 |
农学 | 6329篇 |
基础科学 | 1364篇 |
25142篇 | |
综合类 | 36659篇 |
农作物 | 8235篇 |
水产渔业 | 9792篇 |
畜牧兽医 | 106399篇 |
园艺 | 2688篇 |
植物保护 | 13036篇 |
出版年
2019年 | 1879篇 |
2018年 | 2799篇 |
2017年 | 3174篇 |
2016年 | 2915篇 |
2015年 | 2480篇 |
2014年 | 3144篇 |
2013年 | 8151篇 |
2012年 | 5759篇 |
2011年 | 7140篇 |
2010年 | 4729篇 |
2009年 | 4849篇 |
2008年 | 7088篇 |
2007年 | 6569篇 |
2006年 | 6151篇 |
2005年 | 5804篇 |
2004年 | 5735篇 |
2003年 | 5797篇 |
2002年 | 5397篇 |
2001年 | 6254篇 |
2000年 | 6295篇 |
1999年 | 4890篇 |
1998年 | 2262篇 |
1997年 | 2188篇 |
1996年 | 2041篇 |
1995年 | 2460篇 |
1994年 | 2235篇 |
1993年 | 2086篇 |
1992年 | 4208篇 |
1991年 | 4478篇 |
1990年 | 4349篇 |
1989年 | 4306篇 |
1988年 | 3979篇 |
1987年 | 3999篇 |
1986年 | 4124篇 |
1985年 | 4036篇 |
1984年 | 3284篇 |
1983年 | 2980篇 |
1982年 | 1974篇 |
1979年 | 3036篇 |
1978年 | 2454篇 |
1977年 | 2003篇 |
1976年 | 2039篇 |
1975年 | 2148篇 |
1974年 | 2612篇 |
1973年 | 2728篇 |
1972年 | 2602篇 |
1971年 | 2471篇 |
1970年 | 2314篇 |
1969年 | 2276篇 |
1967年 | 1951篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
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
103.
Abstract – Factors affecting long-term variation in brown trout, Salmo trutta L., stocking success were examined in a large lake, Lake Oulujärvi, in central Finland. Brown trout were stocked in spring (late May to early June) in 1974–1991 and in summer (late June to early July) in 1992–2001. The biomass of the vendace, Coregonus albula (L.), population (prey) at release time had the largest positive effect on stocking success within both periods: biomass of adult vendace in spring and both 0+ and adult vendace in summer. Increasing the size of stocked fish had a positive effect if the vendace available at release were only adults. The increasing trend of predator-catch-per-unit-effort (CPUE) [combined CPUE of northern pike Esox lucius L., burbot Lota lota (L.), and pike-perch Stizostedion lucioperca (L.)] through the study period and its negative effect on trout stocking success suggested an increasing effect of predation within the entire time series. 相似文献
104.
A E van de Braak A T van 't Klooster A Malestein J A Faber 《The Veterinary quarterly》1986,8(1):12-23
Forty-one dairy cows were fed a low (LCa-13 g/d) and a high (HCa-83.5 g/d) calcium ration in the 8 weeks prior to parturition and the effect on the Ca mobilization rate around parturition was studied. Plasma Ca values were stable in the LCa group around parturition. In the older cows of the HCa group a very slight decrease in the mean plasma Ca was observed: 2.58 mmol/l at 12-36 h ante partum decreased to 2.38 mmol/l at parturition. Hypocalcaemia, which commonly occurs around parturition, did not occur in 40 of the cows. A subclinical hypocalcaemia (1.8 mmol/l) occurred in one cow (parity 10) from the HCa group. To assess the efficiency of Ca mobilization, a severe hypocalcaemia (1.0 mmol/l) with clinical signs was induced by means of Na2EDTA infusion (0.90 mmol/min), starting at 10 h post-partum. The older cows in the LCa group required more Na2EDTA than those in the HCa group. Higher urinary hydroxyproline excretion in the week before parturition in the LCa than in the HCa group suggested a higher bone turnover. Plasma PTH levels around parturition were not significantly different between the groups. The amount of colostrum milked out in the first 10 h post-partum did not influence Ca homeostasis around parturition. The results contradict those of many other experiments in which hypocalcaemia was observed in cows ingesting high levels of Ca. It is concluded that the restricted feed intake prepartum possibly had a favourable effect on Ca homeostasis. 相似文献
105.
Spealman CR 《Science (New York, N.Y.)》1941,93(2408):187-188
The rate of the frog or guinea pig heart preparation was not significantly influenced by the H-ion concentration when this was kept within limits which allowed the heart to continue beating. The theory that the H-ion concentration is intimately concerned with the origination of the heart beat is not supported by the results of this investigation. 相似文献
106.
107.
108.
109.
110.