全文获取类型
收费全文 | 1119篇 |
免费 | 101篇 |
国内免费 | 5篇 |
专业分类
林业 | 32篇 |
农学 | 30篇 |
基础科学 | 12篇 |
130篇 | |
综合类 | 170篇 |
农作物 | 39篇 |
水产渔业 | 112篇 |
畜牧兽医 | 527篇 |
园艺 | 25篇 |
植物保护 | 148篇 |
出版年
2023年 | 7篇 |
2021年 | 14篇 |
2020年 | 25篇 |
2019年 | 15篇 |
2018年 | 20篇 |
2017年 | 23篇 |
2016年 | 23篇 |
2015年 | 20篇 |
2014年 | 28篇 |
2013年 | 59篇 |
2012年 | 56篇 |
2011年 | 59篇 |
2010年 | 38篇 |
2009年 | 27篇 |
2008年 | 61篇 |
2007年 | 57篇 |
2006年 | 55篇 |
2005年 | 52篇 |
2004年 | 40篇 |
2003年 | 56篇 |
2002年 | 46篇 |
2001年 | 29篇 |
2000年 | 23篇 |
1999年 | 32篇 |
1998年 | 19篇 |
1997年 | 17篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 16篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1972年 | 7篇 |
1966年 | 11篇 |
1961年 | 6篇 |
排序方式: 共有1225条查询结果,搜索用时 15 毫秒
11.
12.
SR Cho SA Ock JG Yoo B Mohana kumar SY Choe GJ Rho 《Reproduction in domestic animals》2005,40(2):171-176
The present study was designed to examine the effects of cell-cycle synchronization protocols, such as confluent, roscovitine treatment and serum starvation, in bovine foetal fibroblasts on synchronization accuracy at G0/G1, viability, apoptosis, necrosis and ploidy for use as a nuclei donor. The cells in 5-10 passages were randomly allocated into three treated groups. Cells were cultured either in Dulbecco's modified Eagle's medium (DMEM) + 10% foetal bovine serum (FBS) until 90% confluent (group 1, confluent), in DMEM + 10% FBS + 30 microM roscovitine for 12 h (group 2, roscovitine), or in DMEM + 0.5% FBS for 5 days (group 3, serum starvation). Most of the cells (>80%) in all groups were arrested at the G0/G1 stage. Although the rates did not differ, cells in group 1 showed an increased cell population arrested at the G0/G1 phase. Significantly (p < 0.05) higher rates of apoptosis occurred in group 3 than in group 1 and 2 (10% vs 6% and 6%, respectively). No differences in chromosomal abnormality were observed among groups. However, by increasing the number of cell culture passages up to 15, significantly (p < 0.05) higher chromosomal abnormality was observed than in 5 and 10 passages (39% vs 28% and 23%, respectively) in group 1. The results clearly indicated that bovine foetal fibroblasts could be effectively synchronized at G0/G1 stages by all the three different treatments, confluent, roscovitine and serum starvation. However, cells in confluent showed reduced apoptosis and necrosis when they underwent 5-10 passages, exhibiting increased percentage of cells with stable chromosome diversity. Hence, cells in confluent merit further studies before they could be used as nuclear donors. 相似文献
13.
Jennifer E Graham Michael S Kent Alain Théon 《Veterinary Clinics of North America: Exotic Animal Practice》2004,7(3):757-81, vii
The majority of information on oncology therapies has been reported in humans, canine, and feline patients, and laboratory animals with experimentally induced tumors. A variety of treatments,including radiation therapy, chemotherapy, photodynamic therapy, and others have been used with exotic animals. There are many species of exotic pets, and anatomic differences, as well as husbandry and nutritional requirements, must be taken into account to provide optimal care. By providing a broad overview of therapies and considerations for treatment, this article is intended to provide the practitioner with an overview of approach and options when addressing oncology cases in exotic animals. 相似文献
14.
15.
16.
Theileria orientalis (also known historically as T. sergenti and T. buffeli) is responsible for benign or non-transforming theileriosis, and exerts its major effect through erythrocyte destruction. The life cycle of T. orientalis is essentially similar to that of other Theileria species, except that the schizonts do not induce transformation and fatal lymphoproliferation. The pathogenesis of anaemia as a result of infection is not clearly established and may be multifaceted. Clinical signs of weakness, reluctance to walk and abortion are early but non-specific indications of disease, particularly if accompanied by a history of cattle being moved. Physical examination may reveal pallor (pale eyes, vaginal mucosa), pyrexia, and elevated heart and respiratory rates. T. orientalis is an economically important parasite of cattle in New Zealand, Australia and Japan, especially where naïve animals are introduced into an endemic area or in animals under stress. Increased awareness of the risks posed by the parasite is required to enable management practices to be implemented to minimise its impact. 相似文献
17.
18.
A computer program based on empirical relationships is described. It predicts daily energy and nitrogen utilisation repetitively for sheep of any age, before, during and after weaning; provision is also made for pregnancy, lactation and cold stress. Input information includes: intake, protein content and digestibility of the diet; age, empty body weight, fat content and feeding activity of the sheep; ambient temperature and wind speed; times of shearing and mating.Metabolisable energy from milk and/or dry feed is estimated and energy requirements for maintenance, including the cost of feeding activities and homeostasis in the cold, are deducted to obtain energy balance. The amount of amino acid nitrogen absorbed from the small intestine is estimated, and nitrogen balance in body tissues and wool is calculated from this, allowing for body weight and net energy intake. Potential wool growth is calculated from nitrogen and energy intakes, and potential conceptus growth or milk production is estimated primarily from stage of pregnancy or lactation. The use of nitrogen and energy for these products is assessed and balances of energy and nitrogen in body tissues are then obtained by difference. If achievement of the potential rates of production in pregnant or lactating animals would cause excessive loss of energy or nitrogen from body tissues, production of wool and conceptus or milk is reduced sufficiently to avoid this problem. Gain or loss of body fat and protein, and hence change of empty live weight, are finally derived and the animal parameters are incremented before proceeding to calculation for the next day.Evidence is presented that the model is stable in predicting lifetime performance, and that predictions of growth curves, body composition and various nutritional parameters are reasonably accurate in a variety of circumstances. 相似文献
19.
John B. Graham Joan I. Nassauer William S. Currie Herbert Ssegane M. Cristina Negri 《Landscape Ecology》2017,32(5):1023-1037
Context
Wild bee populations are currently under threat, which has led to recent efforts to increase pollinator habitat in North America. Simultaneously, U.S. federal energy policies are beginning to encourage perennial bioenergy cropping (PBC) systems, which have the potential to support native bees.Objectives
Our objective was to explore the potentially interactive effects of crop composition, total PBC area, and PBC patches in different landscape configurations.Methods
Using a spatially-explicit modeling approach, the Lonsdorf model, we simulated the impacts of three perennial bioenergy crops (PBC: willow, switchgrass, and prairie), three scenarios with different total PBC area (11.7, 23.5 and 28.8% of agricultural land converted to PBC) and two types of landscape configurations (PBC in clustered landscape patterns that represent realistic future configurations or in dispersed neutral landscape models) on a nest abundance index in an Illinois landscape.Results
Our modeling results suggest that crop composition and PBC area are particularly important for bee nest abundance, whereas landscape configuration is associated with bee nest abundance at the local scale but less so at the regional scale.Conclusions
Strategies to enhance wild bee habitat should therefore emphasize the crop composition and amount of PBC.20.