全文获取类型
收费全文 | 4788篇 |
免费 | 278篇 |
国内免费 | 12篇 |
专业分类
林业 | 238篇 |
农学 | 253篇 |
基础科学 | 54篇 |
857篇 | |
综合类 | 397篇 |
农作物 | 194篇 |
水产渔业 | 240篇 |
畜牧兽医 | 2274篇 |
园艺 | 117篇 |
植物保护 | 454篇 |
出版年
2021年 | 42篇 |
2020年 | 81篇 |
2019年 | 67篇 |
2018年 | 94篇 |
2017年 | 102篇 |
2016年 | 86篇 |
2015年 | 64篇 |
2014年 | 89篇 |
2013年 | 212篇 |
2012年 | 181篇 |
2011年 | 262篇 |
2010年 | 198篇 |
2009年 | 175篇 |
2008年 | 228篇 |
2007年 | 193篇 |
2006年 | 182篇 |
2005年 | 178篇 |
2004年 | 166篇 |
2003年 | 162篇 |
2002年 | 187篇 |
2001年 | 136篇 |
2000年 | 118篇 |
1999年 | 112篇 |
1998年 | 54篇 |
1997年 | 37篇 |
1996年 | 41篇 |
1995年 | 43篇 |
1994年 | 49篇 |
1993年 | 57篇 |
1992年 | 85篇 |
1991年 | 77篇 |
1990年 | 80篇 |
1989年 | 76篇 |
1988年 | 45篇 |
1987年 | 58篇 |
1986年 | 48篇 |
1985年 | 56篇 |
1984年 | 62篇 |
1983年 | 55篇 |
1982年 | 55篇 |
1980年 | 34篇 |
1979年 | 41篇 |
1978年 | 47篇 |
1977年 | 46篇 |
1976年 | 43篇 |
1975年 | 35篇 |
1974年 | 41篇 |
1972年 | 36篇 |
1971年 | 34篇 |
1969年 | 43篇 |
排序方式: 共有5078条查询结果,搜索用时 15 毫秒
81.
J G Van der Walt 《The Onderstepoort journal of veterinary research》1978,45(2):125-131
82.
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
83.
84.
85.
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
86.
87.
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
88.
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
89.
90.
J F Van Vleet W A Tacker P E Cechner R M Bright J A Greene M R Raffee L A Geddes V J Ferrans 《American journal of veterinary research》1978,39(6):981-987
The safety of open thorax defibrillation with single damped sine-wave shocks and 6-cm-diameter electrodes was evaluated in healthy anesthetized dogs. Twenty-one dogs were allotted to 6 groups: Group A were nonshocked controls and groups B through F were given single shocks of 4-, 7-, 12-, 19-, or 32-fold, respectively, greater than a defibrillation threshold dose (30 mA/g of heart). Immediate postshock death resulted in group F dogs; group A through E dogs survived and were killed after 2 days. The incidence and severity of cardiac morphologic damage increased with shock strength (mild damage occurred in 1 of 3 dogs in group C and in 3 of 4 dogs in group D and severe damage occurred in 2 of 3 dogs in group E). The cardiac lesions were characterized grossly and microscopically. In dogs that died immediately after shocking, damage was apparent as pale circular zones of edema and myofibrillar degeneration in the ventricular free walls beneath the electrode placement sites on the cardiac surface. In the dogs that survived 2 days, the defibrillator-induced areas of myocardial necrosis and calcification were concentrated in arc or ringlike patterns beneath the periphery of the electrode placement sites. All dogs that were studied 2 days after shocking had mild fibrinous pericarditis. Postshock electrocardiographic changes were not good indicators of cardiac damage because the mild epicardial inflammatory reaction associated with the surgical procedure produced large ST and T wave changes which masked any changes associated with myocardial necrosis induced by the electric shocks. It was concluded that a substantial safety margin exists between the required defibrillation threshold shock dose and the large shocks required to produce marked cardiac damage or death in healthy dogs. 相似文献