全文获取类型
收费全文 | 141586篇 |
免费 | 7838篇 |
国内免费 | 93篇 |
专业分类
林业 | 6378篇 |
农学 | 4614篇 |
基础科学 | 867篇 |
19261篇 | |
综合类 | 22027篇 |
农作物 | 5795篇 |
水产渔业 | 7376篇 |
畜牧兽医 | 71308篇 |
园艺 | 2051篇 |
植物保护 | 9840篇 |
出版年
2021年 | 1179篇 |
2020年 | 1382篇 |
2019年 | 1525篇 |
2018年 | 2468篇 |
2017年 | 2746篇 |
2016年 | 2487篇 |
2015年 | 2034篇 |
2014年 | 2576篇 |
2013年 | 5809篇 |
2012年 | 4854篇 |
2011年 | 5776篇 |
2010年 | 3610篇 |
2009年 | 3680篇 |
2008年 | 5553篇 |
2007年 | 5218篇 |
2006年 | 4783篇 |
2005年 | 4536篇 |
2004年 | 4253篇 |
2003年 | 4346篇 |
2002年 | 3856篇 |
2001年 | 4316篇 |
2000年 | 4395篇 |
1999年 | 3509篇 |
1998年 | 1522篇 |
1997年 | 1427篇 |
1996年 | 1319篇 |
1995年 | 1572篇 |
1994年 | 1384篇 |
1993年 | 1258篇 |
1992年 | 2630篇 |
1991年 | 2755篇 |
1990年 | 2626篇 |
1989年 | 2643篇 |
1988年 | 2402篇 |
1987年 | 2380篇 |
1986年 | 2456篇 |
1985年 | 2371篇 |
1984年 | 1911篇 |
1983年 | 1699篇 |
1982年 | 1165篇 |
1979年 | 1771篇 |
1978年 | 1411篇 |
1976年 | 1226篇 |
1975年 | 1303篇 |
1974年 | 1523篇 |
1973年 | 1530篇 |
1972年 | 1422篇 |
1971年 | 1322篇 |
1970年 | 1270篇 |
1969年 | 1301篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
C F Burrows A M Merritt A M Chiapella 《Journal of the American Veterinary Medical Association》1979,174(1):62-66
Quantitative fat and trypsin analysis was done on the feces of dogs with chronic diarrhea. The results of clinical examination, quantitative fecal analysis, and other laboratory tests permitted assignment of the dogs into one of 4 groups: (1)pancreatic exocrine insufficiency,(2)small intestinal malabsorption,(3)colitis, and(4)other nonspecific or incompletely diagnosed diarrhea. The mean 24-hour fat output was significantly higher (p less than 0.01) in dogs with malabsorption or pancreatic insufficiency than in clinically normal dogs, dogs with colitis, or dogs with nonsteatorrheic diarrheas. The mean 24-hour trypsin output with pancreatic insufficiency was significantly (P less than 0.01) lower, and in dogs with malabsorption, significantly (P less than 0.05) higher than in clinically normal dogs. Normalization of the output data for body weight enhanced the value of fat and trypsin analyses in the differentiation of pancreatic insufficiency and intestinal malabsorption from other causes of chronic canine diarrhea. 相似文献
992.
The colostomised hens received 15N-labelled wheat. For a period of 8 days the incorporation of the 15N excess (15N') into the albumen, the yolk and the egg-shell was measured. In addition to that, the values for atom-percent of 15N' in the amino acids lysine, histidien and arginine of the albumen and the yolk were ascertained. The egg-shell and the albumen were labelled shortly after the beginning of the experiment. In both fractions the atom-per cent of 15N' rises more quickly than in the yolk. After the withdrawal of the labelled feed the decrease in the yolk was slower than in the egg-shell and the albumen. Concerning the atom-per cent of 15N' there is hardly a difference between the total N and the amino acids. Despite the different supply with amino acids, the relation of histidine 15N' : lysine 15N' : arginine-15N' in the yolk and the albumen remains largely constant. It is 1 : 2 : 3 and corresponds to the quantitative relation of the N content of the three amino acids in the egg protein. The utilisation of 14N and 15N' of the wheat lysin for the egg synthesis amounts to approximately 50%. There are considerable differences between the utilisation of 15N' of the histidine and 15N' of the arginine and the 14N of the two dietary amino acids. 相似文献
993.
T A Bongso 《The Veterinary record》1979,105(19):442-443
Doses of 100 to 300 mg of a 10 per cent solution of xylazine satisfactorily sedated six elephants ranging from 150 to 255 cm shoulder height. At these dosages all animals were sedated in the standing position. The time taken to produce the initial signs of sedation ranged from 10 +/- 4 to 20 +/- 4 minutes and the effects lasted from 60 +/- 8 to 100 +/- 15 minutes. The time taken from injection to complete recovery ranged from 360 +/- 31 to 540 +/- 21 minutes. Recovery was uncomplicated. Repeated administration of as much as seven injections per animal at intervals of three to four days had no adverse effects. Disturbances during induction delayed the onset of action of the drug. 相似文献
994.
995.
The effect of parturition on the blood picture of sheep 总被引:1,自引:0,他引:1
Parturition in sheep was associated with significant increases in the packed cell volume, haemoglobin concentration and red cell counts. Subsequently these values gradually declined, attaining prepartum levels by the seventh day post partum. Blood leucocyte counts were also elevated at parturition and this was associated with marked neutrophilia, lymphocytopenia and mild eosinopenia. These changes were gradually reversed thereafter, with normal values being attained by the fourteenth day post partum. 相似文献
996.
997.
A M Pope J E Heavner J A Guarnieri C P Knobloch 《Journal of the American Veterinary Medical Association》1986,189(7):781-783
The neuroteratogenicity of trichlorfon was evaluated in 3 groups of pregnant sows (8/group). The treatments were: control (no trichlorfon), trichlorfon (60 mg/kg of body weight) in the feed only on day 55 of gestation, or trichlorfon (60 mg/kg of body weight) in the feed on day 55 and day 70 of gestation. One week after farrowing, all newborn pigs were removed from the sows and were euthanatized. Brain and cerebellum weights of the newborn pigs were recorded. Mean cerebellum weights and cerebellum/total brain weight ratios of the neonatal pigs were 3.780 and 0.106 (group 1, n = 26), 3.183 and 0.098 (group 2, n = 42), and 2.986 and 0.088 (group 3, n = 61). Although trichlorfon interfered with cerebellar development and the severity of the trichlorfon-induced cerebellar hypoplasia was dosage-related, ataxia did not develop in the neonatal pigs. 相似文献
998.
Four subsamples of meat and bone meal (MBM) were heated (150 degrees C) for 0, 1.5, 3 and 5 h and then incorporated into four individual diets (100 g MBM/kg diet). The diets were precision-fed to 10 caecectomised and 10 intact adult cockerels. The apparent amino acid digestibility (ApAAD) and true amino acid digestibility (TAAD) of the diets were determined by analysis of the excreta. The digestibility coefficients measured using caecectomised birds were lower than those determined with intact birds. Coefficients of digestibility were statistically examined by analysis of variance for the effects of bird type (caecectomised or intact), type of calculation (apparent or true) and diet (heat-treatment) with and without accommodation for individual bird variability. If individual bird variability was not considered in the analysis the bird type X diet interactions (P less than 0.01) included glutamic acid, tyrosine and serine. When individual bird variability was included in the analysis, significant (P less than 0.01) bird type X diet interactions occurred for aspartic acid, serine, glutamic acid, leucine, tyrosine and lysine and the precision of the data was markedly improved. Amino acid digestibility using the precision-feeding procedure is affected by the selection of either intact or caecectomised birds. 相似文献
999.
1000.
M L Bruss Y Gr?hn E M Huffman L A Lindberg 《American journal of veterinary research》1986,47(2):336-341
Sodium propionate (3 mmol/kg) was injected IV into 8 nonlactating dairy cows before and after 6 days (144 hours) of fasting. During fasting, long-chain fatty acids in plasma increased from 0.30 +/- 0.05 (SE) mM to 1.09 +/- 0.15 mM (P less than 0.05). Liver fat increased from 0.5 +/- 0.3% to 9.3 +/- 1.7% (P less than 0.05). Half-life of injected sodium propionate increased significantly (P less than 0.05) from 7.6 +/- 0.5 minutes to 10.1 +/- 1.0 minutes during fasting. Sulfobromophthalein half-life did not change significantly (3.8 +/- 0.79 minutes to 5.3 +/- 1.3 minutes). Increases in plasma glucose concentrations after propionate loading were significantly less during fasting than during feeding. Thus, the change in glucose concentration served as an indicator of hepatic conversion of propionate to glucose. Increases in glucose concentration of less than 2 mM at 30 minutes after propionate loading indicated that liver function was altered in nonlactating dairy cows. 相似文献