全文获取类型
收费全文 | 8229篇 |
免费 | 403篇 |
国内免费 | 57篇 |
专业分类
林业 | 1261篇 |
农学 | 214篇 |
基础科学 | 62篇 |
1387篇 | |
综合类 | 744篇 |
农作物 | 248篇 |
水产渔业 | 356篇 |
畜牧兽医 | 3721篇 |
园艺 | 219篇 |
植物保护 | 477篇 |
出版年
2023年 | 50篇 |
2022年 | 73篇 |
2021年 | 98篇 |
2020年 | 142篇 |
2019年 | 73篇 |
2018年 | 210篇 |
2017年 | 181篇 |
2016年 | 209篇 |
2015年 | 192篇 |
2014年 | 175篇 |
2013年 | 426篇 |
2012年 | 401篇 |
2011年 | 373篇 |
2010年 | 239篇 |
2009年 | 163篇 |
2008年 | 322篇 |
2007年 | 381篇 |
2006年 | 334篇 |
2005年 | 275篇 |
2004年 | 270篇 |
2003年 | 246篇 |
2002年 | 229篇 |
2001年 | 162篇 |
2000年 | 159篇 |
1999年 | 124篇 |
1992年 | 95篇 |
1991年 | 111篇 |
1990年 | 133篇 |
1989年 | 151篇 |
1988年 | 120篇 |
1987年 | 102篇 |
1986年 | 106篇 |
1985年 | 97篇 |
1984年 | 95篇 |
1983年 | 75篇 |
1979年 | 103篇 |
1978年 | 72篇 |
1977年 | 64篇 |
1976年 | 50篇 |
1975年 | 66篇 |
1974年 | 84篇 |
1973年 | 95篇 |
1972年 | 69篇 |
1971年 | 86篇 |
1970年 | 80篇 |
1969年 | 88篇 |
1968年 | 69篇 |
1967年 | 70篇 |
1966年 | 49篇 |
1965年 | 65篇 |
排序方式: 共有8689条查询结果,搜索用时 31 毫秒
21.
22.
With the help of a new synthetic material follicles and corpora lutea from the ovaries of 80 cows in different stages of the sexual cycle were examined for modifications of their blood vessel architecture. In the theca externa the main artery which runs towards the follicle, separates into arterioles of which capillaries derive in the theca interna, building a basket-like network around the zona granulosa. After ovulation the follicle wall forms characteristic fields. Capillaries grow into the zona granulosa and thus the folds form the lobular structure of the corpus luteum. Capillaries which rise from the ruptured part of the follicle, spread centripetally and together with lutein cells they build up the not lobulated cupola of the corpus luteum. The regression of the corpus luteum starts around the 16th day of the cycle, beginning at the capillary network of the cupola. A contraction of the vessels and a quick decrease of the volume follow. 相似文献
23.
K Fehlhaber G Krüger V Schubert H Rolletschek 《Archiv fuer experimentelle veterinaermedizin》1989,43(6):855-862
Reference is made to work undertaken by Stehle (1983) on rapid semiquantitative determination of urinary protein in pigs for slaughter to identify premortal strain and stress, with additional studies being conducted into the suitability of the method. The investigations performed for this study covered urinary protein samples from 59 living and 762 slaughtered pigs. The Biophan E paper strip test was applied to groups of animals, and, when compared to high-accuracy laboratory determination of urinary protein, it provided sufficiently accurate information on the presence of stress-related proteinuria. Its accuracy, however, proved to be insufficient, when individual animals were examined. The number of clearly stressed slaughter pigs was unexpectedly high, although the same animals had been rated clinically inconspicuous prior to slaughter. Brief rest period resulted in significant rise of stress. The Biophan E paper strip test was found to be suitable for instantaneous determination of stress and strain on pigs for slaughter. 相似文献
24.
The anatomical-pathological findings of 15 woolly monkeys were comparable with those described in man with essential benign or malignant hypertension. Kidneys revealed arterio- and arteriolosclerosis or an onion peel-like proliferation, in some cases necrotizing endarteritis. Obesity due to restricted physical activity, unnatural feeding, and psychical and physical stress could have contributed to the development of this condition. Further, high vulnerability of the genus woolly monkey is postulated. Thus, essential hypertension of woolly monkeys appears to be a multifactorial disease. 相似文献
25.
M Steinhardt S Reimer J Kutschke U Bünger 《Archiv fuer experimentelle veterinaermedizin》1989,43(1):111-119
4 female and 2 male untrained fattening pigs, weighing 43.9 +/- 1.6 kg at the beginning of the experiment underwent continuous measurement of VO2, VCO2, and rectal temperature, prior to, during, and after running on a horizontal exercise belt set to speeds of 0.7, 1.3, and 2.5 m.s-1. The highest values of VO2 and VCO2 (ml-min-1/kg-1) and rectal temperature (degrees C) were usually measured few minutes after running. They were 18.84 +/- 3.65 and 20.4 +/- 4.53 as well as 41.2 +/- 0.4, 28.41 +/- 4.07 and 33.26 +/- 5.92 or 41.3 +/- 0.5, 26.21 +/- 7.7 and 32.32 +/- 7.14 as well as 40.5 +/- 0.7, depending on the above belt speeds. Exercise belt speeds of 1.3 to 1.8 m.s-1 were found to be suitable for testing aerobic metabolic capacity of untrained young pigs. 相似文献
26.
The occurrence of hide damage light flecks and spots was determined on tanned hides from 28 herds during a period of 8 to 12 months. Light flecks and spots are described as small areas of grain loss up to 3 mm in diameter that are seen on dyed crust cattle leather. Damage was found on 75.8% of all hides. The neck and shoulders were the anatomical region with the highest prevalence of damage. Sixty-eight per cent of all hides had light flecks and spots in this region. The forelimbs and dewlap were the anatomical region with the second highest occurrence with a prevalence of 39.1%. This distribution corresponded to the known distribution of lice in cattle. No significant differences were observed in age, sex, prevalence of lice in the herd assessed in March or infestations with different lice species. The frequency of light flecks and spots varied significantly during the year. The frequency was highest in the late winter and early spring, decreased significantly during the summer and was lowest in the autumn. This variation supported the importance of lice in the development of light flecks and spots and suggested a relatively long healing period for the damages induced by lice. 相似文献
27.
Christian Walzer Anna Kübber-Heiss Nadia Robert 《Journal of veterinary diagnostic investigation》2002,14(1):76-79
Removal of the spinal cord is considered time consuming and difficult. A delay in the necropsy procedure, especially in the central nervous system, can result in significant tissue autolysis and subsequent diagnostic difficulties. In the field, where many necropsies are performed, suitable electric saws are mostly unavailable. A technically simple and rapid method for spinal cord removal, requiring only a straightforward tool, has been devised. No necropsy-induced structural damage has been noted on histopathologic examination. 相似文献
28.
Bull sperm pellets experimentally infected with various concentrations of Mycoplasma (M.) bovis, M. bovigenitalium, and M. californicum were stored several months at -196 degrees C and were subsequently tested for mycoplasmas, using different methods and culturing media. M. bovis was reliably identified by laboratory diagnosis up to a concentration of 10(2) cfu/pellet. M. bovigenitalium and M. californicum were found to make higher demands on the quality of culturing substrates. Recommended are 1-h broth incubation and 5-d broth breeding. 相似文献
29.
30.