全文获取类型
收费全文 | 4428篇 |
免费 | 262篇 |
国内免费 | 10篇 |
专业分类
林业 | 223篇 |
农学 | 238篇 |
基础科学 | 51篇 |
730篇 | |
综合类 | 328篇 |
农作物 | 185篇 |
水产渔业 | 196篇 |
畜牧兽医 | 2205篇 |
园艺 | 110篇 |
植物保护 | 434篇 |
出版年
2021年 | 37篇 |
2020年 | 78篇 |
2019年 | 60篇 |
2018年 | 84篇 |
2017年 | 97篇 |
2016年 | 77篇 |
2015年 | 62篇 |
2014年 | 83篇 |
2013年 | 198篇 |
2012年 | 167篇 |
2011年 | 224篇 |
2010年 | 176篇 |
2009年 | 162篇 |
2008年 | 206篇 |
2007年 | 176篇 |
2006年 | 172篇 |
2005年 | 163篇 |
2004年 | 148篇 |
2003年 | 145篇 |
2002年 | 164篇 |
2001年 | 130篇 |
2000年 | 115篇 |
1999年 | 106篇 |
1998年 | 52篇 |
1997年 | 34篇 |
1996年 | 40篇 |
1995年 | 36篇 |
1994年 | 46篇 |
1993年 | 54篇 |
1992年 | 82篇 |
1991年 | 74篇 |
1990年 | 79篇 |
1989年 | 72篇 |
1988年 | 42篇 |
1987年 | 58篇 |
1986年 | 47篇 |
1985年 | 57篇 |
1984年 | 62篇 |
1983年 | 51篇 |
1982年 | 53篇 |
1980年 | 33篇 |
1979年 | 39篇 |
1978年 | 45篇 |
1977年 | 45篇 |
1976年 | 44篇 |
1975年 | 35篇 |
1974年 | 41篇 |
1972年 | 34篇 |
1971年 | 34篇 |
1969年 | 43篇 |
排序方式: 共有4700条查询结果,搜索用时 0 毫秒
81.
C D Van Houweling W B Bixler J R McDowell 《Journal of the American Veterinary Medical Association》1977,171(11):1153-1156
Chemical contamination of animal feeds and feed ingredients is of concern to the Food and Drug Administration. Contamination by industrial chemicals such as polychlorinated biphenyls and polybrominated biphenyls; heavy metals such as lead, cadmium, and mercury; and pesticides such as dieldrin and chlordane exemplify the problem in feeds and the resulting problem of tissue residues in human foods. 相似文献
82.
J G Van der Walt 《The Onderstepoort journal of veterinary research》1978,45(2):125-131
83.
Merryn McKinnon Mizaan Ahmad Meg Bongers Rory Chevalier Isabel Telfer Clare Van Dorssen 《Human Dimensions of Wildlife》2018,23(1):90-99
Culling kangaroos, Australia’s most abundant marsupial, is a controversial practice in the Australian Capital Territory (ACT). The ACT government introduced a kangaroo management plan in response to the growing kangaroo population causing damage in grassland ecosystems. Although some groups (e.g., local government, some researchers) support implementation of this plan, critics claim it is inhumane and lacks concrete evidence. To examine media portrayal of this debate, this study conducted a content analysis of newspaper coverage between 2006 and 2016. Although ACT newspapers were impartial in their presentation of the debate, sources that previous studies found were typically considered trustworthy to speak on the scientific validity of the program were found to have conflicting messages and be less represented in the media. Thus, future research should explore if the messenger is more important than the message in determining influences on public perceptions about the use of lethal control. 相似文献
84.
85.
86.
J A Van Wyk 《The Onderstepoort journal of veterinary research》1975,42(2):75-76
With this adjustable apparatus sheep aged from five months to five years and varying in mass from 16-95 kg could be restrained effectively. Cercarial suspension was split by only 2/44 sheep during infestation with Schistosoma mattheei. Using a battery of seven cages, it was possible to infest 23 sheep, each for 30 minutes, in one day. No cercariae were more than 4-1/2 hours old at the end of exposure. 相似文献
87.
88.
Kubi C Billiouw M Van Den Bossche P 《The Onderstepoort journal of veterinary research》2007,74(3):223-229
Trypanosomal infections in female Glossina morsitans morsitans were investigated in an area in the Eastern Province of Zambia between 1992 and 1994. A total of 4416 flies were captured, aged using the ovarian ageing method and screened for trypanosomal infections in both the mouthparts, salivary glands and the midgut. Congolense-type infections were identified in 4.8% of the flies. Vivax-type and immature infections were identified in 1.8% and 6.8% of the flies, respectively. The prevalence of congolense-type, vivax-type and immature infections increased with age. For vivax-type infections the age-prevalence relationship could be described by a model assuming a constant per capita rate of infection. For congolense-type and midgut infections, a polynomial term was added to the model significantly improving the fit. The per capita at which flies become infected was significantly higher for immature compared to mature infections. Observations strongly suggest that tsetse acquire new midgut infections at any age and that maturation of these infections is not limited to those obtained during the first blood meal. 相似文献
89.
Aklilu HA Almekinders CJ Udo HM Van der Zijpp AJ 《Tropical animal health and production》2007,39(3):165-177
This study aimed to examine village poultry consumption and marketing in Ethiopia in relation to gender, socio-cultural events
and market access. The main objects of the research were producers, poultry markets, producer-sellers, and intermediary sellers
in three locations representing different levels of market access in Tigray. About 3000 farm records were collected over a
period of 12 months from 131 producers to obtain quantitative data on sales and consumption. Ninety-three semi-structured
interviews with 58 producer-sellers and 35 intermediaries and 12 group discussions with these market actors were conducted
to explore organization, price dynamics and socio-cultural aspects of poultry marketing. In total, 928 producer-sellers and
225 intermediaries were monitored monthly to examine participation by gender in poultry marketing. Better market access was
associated with a shorter market chain and higher prices for the producers. Female-headed households had smaller poultry sales
and consumption per household but sale and consumption per family member were 25% and 66% higher, respectively, than in male-headed
households. While women dominated in the producer-sellers group, intermediaries were mainly men. Religious festivals periodically
shifted local demand and prices of poultry. To improve the benefit of poultry keeping, poverty-stricken households may profit
from better market access through better market information, infrastructure, market group formation and careful planning to
match the dynamics in demand. 相似文献
90.
Present Concepts on the Inflammatory Modulators with Special Reference to Cytokines* 总被引:2,自引:0,他引:2
Van Miert AS 《Veterinary research communications》2002,26(2):111-126
The pro- and anti-inflammatory cytokines create a network of interactions between cells that lead to both stimulatory and inhibitory responses that maintain an effective homeostatic regulation. The anti-inflammatory cytokines are a family of peptides that modulate the pro-inflammatory cytokine response. Cytokines act in concert with non-cytokine mediators, such as prostaglandin E2, glucocorticosteroids, lipocortins, and catecholamines. This review highlights new developments in our understanding of the pathophysiology of inflammation and gives an example of a more recent approach to the modulation of acute systemic inflammatory disorders: activation of 2-adrenergic receptors on macrophages. In this respect the potent 2-adrenergic agonist clenbuterol seems of therapeutic interest. 相似文献