全文获取类型
收费全文 | 76072篇 |
免费 | 3417篇 |
国内免费 | 36篇 |
专业分类
林业 | 5948篇 |
农学 | 3089篇 |
基础科学 | 431篇 |
9237篇 | |
综合类 | 10899篇 |
农作物 | 4126篇 |
水产渔业 | 4544篇 |
畜牧兽医 | 33994篇 |
园艺 | 1727篇 |
植物保护 | 5530篇 |
出版年
2018年 | 3508篇 |
2017年 | 3506篇 |
2016年 | 1953篇 |
2015年 | 835篇 |
2014年 | 853篇 |
2013年 | 2580篇 |
2012年 | 2424篇 |
2011年 | 4068篇 |
2010年 | 3298篇 |
2009年 | 2457篇 |
2008年 | 3147篇 |
2007年 | 3358篇 |
2006年 | 1754篇 |
2005年 | 1678篇 |
2004年 | 1598篇 |
2003年 | 1691篇 |
2002年 | 1527篇 |
2001年 | 1813篇 |
2000年 | 1823篇 |
1999年 | 1462篇 |
1998年 | 620篇 |
1997年 | 606篇 |
1996年 | 546篇 |
1995年 | 642篇 |
1994年 | 600篇 |
1993年 | 581篇 |
1992年 | 1227篇 |
1991年 | 1369篇 |
1990年 | 1259篇 |
1989年 | 1269篇 |
1988年 | 1174篇 |
1987年 | 1137篇 |
1986年 | 1194篇 |
1985年 | 1194篇 |
1984年 | 960篇 |
1983年 | 900篇 |
1982年 | 582篇 |
1979年 | 891篇 |
1978年 | 701篇 |
1977年 | 698篇 |
1976年 | 711篇 |
1975年 | 714篇 |
1974年 | 866篇 |
1973年 | 842篇 |
1972年 | 813篇 |
1971年 | 727篇 |
1970年 | 769篇 |
1969年 | 734篇 |
1968年 | 654篇 |
1967年 | 657篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
J B Herrick 《Veterinary Clinics of North America: Food Animal Practice》1989,5(3):457-469
Marketing to veterinarians is the process of synchronizing the business aspects of his or her goods and services so that they are understood and desired by animal owners. The basic components of a successful marketing program are in four categories: the individual, the situation, the needs, and the implementation. Each category is important and all are interrelated; however, the implementation of a program should not begin until a self-analysis has been done and the situation and its needs are thoroughly researched. Programs that have been used by successful practitioners can be copied. No program can be effective unless the economic status of the client's enterprise is known and understood. 相似文献
42.
Taenia saginata cyst fluid was examined for host proteins; IgG1 and IgG2 as well as haemolytic complement activity were detected. Polyacrylamide gel electrophoresis revealed differences in proteinograms among the samples taken from 1-, 4-, and 10-month old cysts. Fluid from older cysts had fewer protein components and showed a weaker antigenic reaction with sera of bovines infected with T. saginata than that of younger cysts. The roles of antibody and complement in initiating degeneration of the parasite are discussed. 相似文献
43.
P. Laffaille A. Acou J. Guillouët B. Mounaix A. Legault 《Ecology of Freshwater Fish》2006,15(4):583-588
Abstract – Changes in the numbers and size-class structure of European silver eels, Anguilla anguilla , in the River Frémur (France) were examined over a 9-year period after installation of downstream eel passes. The number of silver eels migrating downstream peaked in 1999, then decreased strongly and steadily after 2000, reaching relatively low levels. At the same time, a gradual shift in the silver eel sex ratio from a dominance of males (size from 270 to 442 mm, age from 3 to 6 years) to females (size from 366 to 1112 mm, age from 4 to 9 years) was recorded. Possible explanations for the escapement patterns observed are environmental sex determination and the installation of eel passes on the main hydraulic engineering structures in 1992 and 1996. 相似文献
44.
Fifty six dogs of mixed age and sex were acquired from farms in the Otago/Southland region, and maintained at the Hydatid Research Unit, Taieri, where 43 were each fed two Tueniu ovis cysts. All were bled fortnightly for six or 12 weeks. Coded sera were sent to Wallaceville Animal Research Centre for testing using ELISA, with antigen from T. ovis scoleces. Dog treatments were identified after all tests were complete. A discriminant level was derived from the mean absorbance value plus three standard deviations of 56 sera taken at time zero and 78 sera from serially bled uninfected dogs. None of these 134 sera registered as a false positive using this discriminant level. The data showed no significant deviation from normality, and the expected frequency of the occurrence of false positives is therefore less than 0.14%. Four weeks after infection 63% of dogs proved to be infected were serologically positive, rising to 78% after 6 weeks. When worms were removed by anthelmintic treatment, ELISA absorbance levels decreased. Four weeks after removal 70% of previously infected dogs remained positive, decreasing to 30% after 6 weeks. Six weeks after infection the sensitivity of the test was 78%, and the specificity 63%. However, if dogs with positive ELISA absorbance levels, but which did not purge worms, were regarded as having had worms, the respective figures would be 82% and 100%. The latter figures are similar to our previously published laboratory results. The test is of comparable efficiency to arecoline purgation for surveillance, and has the additional advantage of detecting infection in the majority of those dogs that have been infected for three weeks or more but fail to pass worms on purgation, and a substantial proportion of those infected dogs that were treated by their owners prior to presenting them for purgation in order to avoid detection of infection. 相似文献
45.
46.
47.
48.
Babbitt B 《Science (New York, N.Y.)》1995,267(5206):1954-1955
49.
50.
Culliton BJ 《Science (New York, N.Y.)》1982,216(4552):1295-1296