全文获取类型
收费全文 | 153749篇 |
免费 | 21735篇 |
国内免费 | 29024篇 |
专业分类
林业 | 12083篇 |
农学 | 10475篇 |
基础科学 | 9500篇 |
42771篇 | |
综合类 | 48581篇 |
农作物 | 9709篇 |
水产渔业 | 9604篇 |
畜牧兽医 | 46580篇 |
园艺 | 3912篇 |
植物保护 | 11293篇 |
出版年
2023年 | 1354篇 |
2022年 | 1955篇 |
2021年 | 2084篇 |
2020年 | 3674篇 |
2019年 | 7050篇 |
2018年 | 7113篇 |
2017年 | 8120篇 |
2016年 | 8765篇 |
2015年 | 8818篇 |
2014年 | 8075篇 |
2013年 | 10082篇 |
2012年 | 9214篇 |
2011年 | 8541篇 |
2010年 | 6705篇 |
2009年 | 6021篇 |
2008年 | 5732篇 |
2007年 | 5798篇 |
2006年 | 5241篇 |
2005年 | 4770篇 |
2004年 | 4503篇 |
2003年 | 4261篇 |
2002年 | 3931篇 |
2001年 | 4064篇 |
2000年 | 3762篇 |
1999年 | 3350篇 |
1998年 | 2059篇 |
1997年 | 2025篇 |
1996年 | 1771篇 |
1995年 | 2032篇 |
1994年 | 1889篇 |
1993年 | 1664篇 |
1992年 | 2473篇 |
1991年 | 2383篇 |
1990年 | 2321篇 |
1989年 | 2255篇 |
1988年 | 2067篇 |
1987年 | 1866篇 |
1986年 | 1903篇 |
1985年 | 1707篇 |
1984年 | 1422篇 |
1983年 | 1324篇 |
1979年 | 1376篇 |
1978年 | 1081篇 |
1975年 | 994篇 |
1974年 | 1271篇 |
1973年 | 1311篇 |
1972年 | 1335篇 |
1971年 | 1260篇 |
1970年 | 1159篇 |
1969年 | 1060篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
21.
22.
In a feeding trial lasting for months Halothane-positive fattening pigs were put on a diet containing different concentrations of vitamin E and selenium. After a Myostress application vitamin E and selenium were additionally injected in order to examine stress resistance (CK-test) and regenerative capacity (histological examination of Musculus longissimus dorsi) of skeletal muscle. The study revealed that neither high dietary levels of vitamin E/selenium nor a vitamin E/selenium treatment applied after stress are capable of preventing stress related myopathy nor can they influence its healing up favourably. 相似文献
23.
Four experiments with 270, 44, 432 and 66800 Leghorn hens were carried out to investigate the influence of various Mn additions to diets differed in mineral or Ca contents on egg shell quality. The addition of 300 mg Mn/kg diet improved significantly egg shell breaking strength by 4 N over one year. The supply of 50-500 mg Mn/kg diet for 10-24 weeks of the second half of laying year did not influence the egg shell quality. Addition of mineral mixture or Ca grit to layer rations with adequate or higher Mn levels did not influence egg shell strength. High mineral content in a low manganese diet increased number of cracks by 3%. Strength, weight and ash content of tibia were significantly reduced by feeding a low mineral level. Addition of 50-150 mg Mn per kg low mineral diet normalized partially tibia stability in young hens. It was concluded that supplied dietary Manganese influences calcification positively only in young hens. High levels of Ca did not influence the effects of Mn. 50 mg Mn per kg layers mixture have been considered as an essential supply. 相似文献
24.
A Lindner A Wahdati H Sommer 《Berliner und Münchener tier?rztliche Wochenschrift》1992,105(7):239-242
GSH-Px activity in blood and plasma of 269 horses was determined and interrelated to age, sex, and type of use or breed. Furthermore values in blood were related to hematocrit and hemoglobin contents. Trotters and riding horses had higher GSH-Px activities in plasma as well as in blood (0.83 +/- 0.22 and 0.79 +/- 0.23 U/ml plasma or 27.2 +/- 4.3 and 24.0 +/- 7.0 U/ml blood) than Thoroughbreds in training and yearlings (0.61 +/- 0.,14 and 0.56 +/- 0.16 U/ml plasma or 20.6 2 +/- 6.9 and 24.6 +/- 4.3 U/ml blood). 3 to 6 years old Thoroughbreds had higher GSH-Px-activities than 1 to 2 years old ones. Colts and fillies did not have differing values. 相似文献
25.
46 one day old chickens, divided into five groups, were fed an alternately composed vitamin D3 ration during 36 days. In the group depleted of vitamin D3 the typical rickets were found. When treated with a standard ration (2000 I.U. vit. D3/kg food) after 15 days depletion of vitamin D3 the chickens showed control-group parameters within 3 weeks. Using 60,000 I.U. vitamin D3 after a period of 15 days depletion evoked rather an abrupt beginning of healing tendency accompanied by signs of intoxication which were enhanced in those chickens treated with 120,000 I.U. vitamin D3: increase in number of osteoblasts, calcification of osteoblastic mitochondrial membranes and endothelial cell membranes, as well as degeneration of osteoblasts together with a strong reaction of eosinophils. There did not occur necrosis of osteocytes or of bone structure. Erythrocytes, being embedded in ground substance without endothelial surrounding, was a common finding in every group. 相似文献
26.
聚丙烯酰胺凝胶电泳法鉴定禽呼肠孤病毒 总被引:1,自引:0,他引:1
从感染禽呼肠孤病毒的细胞中,以SDS和酚提取病毒核酸,通过聚丙烯酰胺凝胶电泳(PAGE)法将分节段的核酸分开,经银染色显示,呈3-3-1-3分布,此法可用于禽呼肠孤病毒的快速检测、鉴定。同样方法未能使传染性法氏囊病毒核酸显示。 相似文献
27.
A Yabuki S Suzuki M Matsumot M Kurohmaru Y Hayashi H Nishinakagawa 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(12):1339-1342
The proximal straight tubules of the female mouse kidney exhibit heavy periodic acid Schiff (PAS) staining in their brush borders and numerous cytoplasmic granules. In the present study, the female DBA/2Cr mouse kidney was examined, using various fixatives (formalin, PFA, PLP, Zamboni's, Bouin, or Carnoy solution) and various staining methods (HE, PAS, alcian blue, periodic acid methenamine-silver (PAM), toluidine blue, azan, or Congo red). Under azan and PAM, the staining pattern of the brush border was similar to that of PAS, and few effects of the fixative were observed. Cytoplasmic granules were clearly detected with PAM as well as PAS. However, these granules were not detected with Carnoy solution. Furthermore, distribution of granules differed between PAS and PAM. 相似文献
28.
本文考虑一类耗散非线性波动方程的初边值问题。用半(?)方法和先验估计论证了该问题小初值下在时间大范围的可解性、唯一性;并用凸性方法证明了(?)当条件下该问题的解在有限时间内发生爆破现象。 相似文献
29.
Neutralising antibody to bovid herpesvirus 2 was demonstrated in the serum of 31 (10.8%) of 286 heads of cattle in north, south, and west Syria. 38% of titres were 1:2 to 1:8. There is no published report on isolation of this virus in Syria. 相似文献
30.
Evaluation of abomasal outflow diversion as an experimental model of hypochloremic, hypokalemic metabolic alkalosis in lactating cows.
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J L Ward D F Smith S L Fubini D M Deuel-Aromando 《Canadian journal of veterinary research》1994,58(1):13-19
Four adult, lactating dairy cows were subjected to diversion (loss) of gastric contents through a T-shaped cannula placed in the cranial part of the duodenum just distal to the pylorus. Diversion was continued for 10 to 12 hours, at which point the cows were very weak and depressed. The volume of effluent during this period ranged from 37.3 to 46.8 L, with the largest volume being produced during the first four hours. All cows became dehydrated, with mean packed cell volume and total plasma protein concentration increasing 30% and 19.6%, respectively, but with only a slight increase in plasma creatinine concentration. Plasma Cl- concentrations decreased from a mean of 97.3 mEq/L at the beginning of diversion to a mean of 87.2 mEq/L at eight hours. This was followed by a plateau or slight increase in concentrations over the final hours of diversion. Plasma K+ concentration followed a similar pattern, decreasing from a mean of 3.9 mEq/L to a mean of 2.94 mEq/L at six hours, followed by increasing values until termination of diversion. No changes in plasma Na+ concentration were noted, except for a mild decrease in one cow. Plasma calcium concentrations decreased significantly, reaching 6.6 +/- 0.6 mEq/L at the end of diversion. Venous pH, plasma HCO3- concentration, and plasma base excess concentration increased during the first four to eight hours of diversion, followed by a gradual decline. Although a mild hypochloremic metabolic alkalosis resulted from diversion of abomasal outflow in all cows, substantiated by a mild increase in plasma strong ion difference, the changes observed were not as great as expected.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献