全文获取类型
收费全文 | 272篇 |
免费 | 3篇 |
专业分类
林业 | 13篇 |
基础科学 | 1篇 |
20篇 | |
综合类 | 67篇 |
农作物 | 26篇 |
水产渔业 | 1篇 |
畜牧兽医 | 108篇 |
园艺 | 34篇 |
植物保护 | 5篇 |
出版年
2012年 | 13篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2008年 | 12篇 |
2007年 | 14篇 |
2006年 | 21篇 |
2005年 | 10篇 |
2004年 | 21篇 |
2003年 | 14篇 |
2002年 | 15篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1996年 | 2篇 |
1995年 | 8篇 |
1994年 | 15篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1966年 | 4篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1958年 | 2篇 |
1957年 | 5篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1953年 | 3篇 |
1946年 | 1篇 |
1945年 | 1篇 |
1943年 | 1篇 |
1941年 | 1篇 |
1939年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有275条查询结果,搜索用时 437 毫秒
1.
通过9年田间试验,对幼龄M26砧Aroma苹果树施用0、60及120公斤N(硝酸钙)/公顷和 0、120及240公斤K(氯化钾)/公顷,植株5年生,试验初期便结果.砂壤土,含有机质10.5%.在除草剂处理 相似文献
2.
拉维林娜是一种易于裂果(一种生理失调症)的脐橙。本研究以其酸橙砧的10年生树为试材,每隔8—12天从树冠顶上喷灌一次,均施等量的N、P、K为基肥。试验处理设置如下:1)1987年7月15日—8月7日和1988年7月12日—8月8日间不灌溉; 相似文献
3.
4.
5.
Wathes DC Cheng Z Bourne N Taylor VJ Coffey MP Brotherstone S 《Domestic animal endocrinology》2007,33(2):203-225
During the early postpartum period dairy cows mobilize fat and muscle to support lactation. This is associated with alterations in blood metabolite and hormone profiles which in turn influence milk yield and fertility. This study developed models to determine how metabolic traits, milk yield and body condition score were inter-related at different times in the periparturient period and to compare these relationships in primiparous (PP, n=188) and multiparous (MP, n=312) cows. Data from four previous studies which included information on blood metabolic parameters, parity, milk yield, body condition score and diet were collated into a single dataset. Coefficients of polynomial equations were calculated for each trait between -1 week pre-calving and week +7 postpartum using residual maximum likelihood modelling. The completed dataset was used in a multiple correlation model to determine how the best fit curves were related to each other over time. PP cows had higher concentrations of insulin-like growth factor-I and lower beta-hydroxybutyrate concentrations throughout, higher leptin concentrations pre-partum and both the peak in non-esterified fatty acids and the nadir in urea concentration occurred earlier after calving. These differences were associated with significantly lower milk production. Leptin concentrations fell at calving and were related to body condition score. Insulin was negatively correlated with yield in MP cows only. In MP cows the relationship between insulin-like growth factor-I and yield switched from negative to positive between weeks +4 and +7. Both beta-hydroxybutyrate and urea were positively related to yield in PP cows. In contrast, in MP cows beta-hydroxybutyrate was negatively correlated with yield and urea was strongly related to body condition score but not yield. These results suggest that there are differences in the control of tissue mobilization between PP and MP cows which may promote nutrient partitioning into growth as well as milk during the first lactation. 相似文献
6.
Farquhar VJ McCue PM Nett TM Squires EL 《Journal of the American Veterinary Medical Association》2001,218(5):749-752
OBJECTIVE: To evaluate gonadotropin secretion and ovarian function after administration of deslorelin acetate to induce ovulation in mares. DESIGN: Randomized controlled trial. ANIMALS: 16 healthy mares with normal estrous cycles. PROCEDURE: 8 control mares were allowed to ovulate spontaneously, whereas 8 study mares received deslorelin to induce ovulation when an ovarian follicle > 35 mm in diameter was detected. Follicle development and serum concentrations of gonadotropins were monitored daily during 1 estrous cycle. Pituitary responsiveness to administration of gonadotropin-releasing hormone (GnRH) was evaluated 10 days after initial ovulation. RESULTS: Interovulatory intervals of mares treated with deslorelin (mean +/- SD, 25.6 +/- 2.6 days) were longer than those of control mares (22.9 +/- 1.8 days). Diameter of the largest follicle was significantly smaller during 2 days of the diestrous period after ovulation in deslorelin-treated mares than in control mares. Concentrations of follicle-stimulating hormone (FSH) were lower in deslorelin-treated mares on days 5 through 14 than in control mares. Concentrations of luteinizing hormone were not different between groups during most of the cycle. Gonadotropin release in response to administration of GnRH was lower in mares treated with deslorelin acetate than in control mares. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of deslorelin was associated with reduction in circulating concentrations of FSH and gonadotropin response to administration of GnRH during the estrous cycle. Low concentration of FSH in treated mares may lead to delayed follicular development and an increased interovulatory interval. 相似文献
7.
The densitometric and mechanical structural properties of the left and right fifth metacarpal bones of 10 racing greyhounds with a fracture of the central tarsal bone and 10 without a fracture were investigated by dual energy x-ray absorptiometry and a servo-hydraulic materials testing machine. In all the greyhounds the bone mineral density of the left fifth metacarpal bone was significantly greater than that of the right (P<0.001), but there was no significant difference between the degree of asymmetry in bone mineral density in the two groups. The ultimate torque and energy-to-failure of the left fifth metacarpal bone of the greyhounds with a fracture of the right central tarsal bone were significantly higher than in the right fifth metacarpal bone and higher than in both the left and right fifth metacarpal bones of the greyhounds with no fracture (P<0.05). The ultimate torque and energy-to-failure were significantly related to bone mineral density (P<0.005), and 22 per cent of the variation in these structural properties could be explained by variations in bone mineral density. Fifth metacarpal remodelling in response to asymmetric cyclic loading is bone-specific, and structural properties are enhanced in the left fifth metacarpal of greyhounds with a fracture of the right central tarsal bone. 相似文献
8.
Twenty feline vaccine-associated sarcomas were examined by transmission electron microscopy. Tumors contained pleomorphic spindle cells, histiocytoid cells, and giant cells. Most tumors contained myofibroblasts, which had morphologic features similar to those of fibroblasts. These cells were further distinguished by subplasmalemmal dense plaques and thin cytoplasmic actin myofilaments organized as elongated bundles concentrated at irregular intervals forming characteristic dense bodies. Intracellular crystalline particulate material was found in 5 of the 20 tumors. Energy dispersive X-ray spectroscopy was used to identify the crystalline material within one tumor as aluminum-based. One tumor from a feline leukemia virus-infected cat contained budding and immature retroviral particles. 相似文献
9.
顽固病系一种称作柑桔螺原体(Spiroplosma citri)的菌质体所引起。目前,在加利福尼亚州和亚利桑那州大约有二百万株柑桔树(其中绝大多数是甜橙、葡萄柚和桔柚)感染此病。虽然顽固病通常不会导致植株死亡,但能使果实产量大大减少,故现已成为加州柑桔生产上的一个严重问题。 相似文献
10.
Low-molecular-weight hydrocarbons in the C(l) to C(4) range have been detected and measured in sea water. Methane shows by far the highest concentration, followed in order by the C(2), C(3), and C(4) fractions. In general, the concentration tends to decrease with depth, but there is a strong indication that a maximum may exist about 30 to 50 meters below the surface. 相似文献