全文获取类型
收费全文 | 146294篇 |
免费 | 8162篇 |
国内免费 | 84篇 |
专业分类
林业 | 5420篇 |
农学 | 4369篇 |
基础科学 | 1035篇 |
16889篇 | |
综合类 | 25583篇 |
农作物 | 5416篇 |
水产渔业 | 7379篇 |
畜牧兽医 | 76305篇 |
园艺 | 1774篇 |
植物保护 | 10370篇 |
出版年
2018年 | 1801篇 |
2017年 | 1989篇 |
2016年 | 1864篇 |
2015年 | 1631篇 |
2014年 | 1992篇 |
2013年 | 5444篇 |
2012年 | 3823篇 |
2011年 | 4810篇 |
2010年 | 2975篇 |
2009年 | 3006篇 |
2008年 | 4745篇 |
2007年 | 4510篇 |
2006年 | 4376篇 |
2005年 | 4078篇 |
2004年 | 3963篇 |
2003年 | 3973篇 |
2002年 | 3900篇 |
2001年 | 4698篇 |
2000年 | 4551篇 |
1999年 | 3713篇 |
1998年 | 1469篇 |
1997年 | 1491篇 |
1996年 | 1395篇 |
1995年 | 1752篇 |
1994年 | 1582篇 |
1993年 | 1510篇 |
1992年 | 3164篇 |
1991年 | 3295篇 |
1990年 | 3334篇 |
1989年 | 3327篇 |
1988年 | 3055篇 |
1987年 | 3139篇 |
1986年 | 3231篇 |
1985年 | 3095篇 |
1984年 | 2615篇 |
1983年 | 2313篇 |
1982年 | 1575篇 |
1981年 | 1474篇 |
1980年 | 1430篇 |
1979年 | 2324篇 |
1978年 | 1917篇 |
1977年 | 1629篇 |
1976年 | 1444篇 |
1975年 | 1541篇 |
1974年 | 2083篇 |
1973年 | 2092篇 |
1972年 | 2059篇 |
1971年 | 1821篇 |
1970年 | 1717篇 |
1969年 | 1576篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Ante mortem diagnosis of pancreatitis in four cats 总被引:1,自引:0,他引:1
K. W. Simpson J. T. Shiroma D. S. Biller J. Wicks S. E. Johnson D. Dimski D. Chew 《The Journal of small animal practice》1994,35(2):93-99
The ante mortem detection of pancreatitis in four cats is reported. Clinical findings included vomiting, lethargy and constipation in all the cats, diabetes mellitus in two cats and severe jaundice and a vitamin K responsive coagulopathy in one cat. Serum amylase was normal in all the cats and serum lipase was elevated in one azotaemic cat. Ultrasonography revealed predominantly hypoechoic masses in the right cranial quandrant of the abdomen of each cat. The anatomical location of these masses was consistent with the pancreas. Gross examination supported these ultrasonographic observations. The pancreatic lesions were characterised histologically as acute necrotising pancreatitis, acute necrotising pancreatitis with abscessation, chronic active pancreatitis with cystic dilatation of the pancreatic duct causing bile duct obstruction and chronic active pancreatitis with nodular hyperplasia. This report indicates that pancreatitis is a clinically significant disease in cats that may be diagnosed ante mortem. 相似文献
992.
J. A. Joyce 《The Journal of small animal practice》1994,35(7):341-344
Aural haematomas were treated using a Pen-rose tissue drain inserted through the haematoma and left in situ for two weeks. Oral prednisolone was prescribed at a dose of 2 mg/kg for two weeks then 1 mg/kg for a further two weeks. Twenty-nine haematomas were treated in 22 dogs. Twenty-six cases resolved after a single treatment. Three ears required a second treatment two to four weeks after the initial treatment and one dog had a postoperative infection of the drain tract. No ears required more than one repeated drainage. Good cosmetic results were achieved in all cases. 相似文献
993.
S. Quirós Carmona R. Navarrete-CalvoM.M. Granados J.M. DomínguezJ. Morgaz J.A. Fernández-SarmientoP. Muñoz-Rascón R.J. Gómez-Villamandos 《Research in veterinary science》2014
Six Beagles were used in this prospective randomised crossover experimental study. Dexmedetomidine was administered at 0, 1 or 2 μg/kg IV for group C, LDA and HDA, respectively. Animals were induced and maintained with alfaxalone at 0.07 mg/kg/min with a CRI dexmedetomidine dose of 0, 0.5 or 1 μg/kg/h for group C, LDA and HDA, respectively. Cardiorespiratory variables, arterial blood gases and depth of anaesthesia were recorded. The recovery times and quality of recovery were scored. Group HDA produced a greater increase in the depth of anaesthesia than LDA. However, with both protocols, CI was halved compared to normal values in dogs. The use of oxygen before and during the anaesthetic maintenance is advisable, mainly if dexmedetomidine is going to be use as a pre-medicant and maintenance agent. The quality of recovery was better in groups receiving dexmedetomidine, without causing an increase in recovery time. 相似文献
994.
J. Sales M. Skřivan M. Englmaierová 《Journal of animal physiology and animal nutrition》2014,98(6):1054-1059
Mathematical modelling of the relationships between mineral inputs and outputs would enable the prediction of mineral requirements of poultry under a wide range of conditions. To establish the feasibility of possible modelling of mineral requirements, the current study aimed to describe the individual mineral concentrations of whole bodies of quail over the life cycle from hatching to 70 days of age. Quail were reared indoors without any restrictions that could limit growth. Sampling of birds (n = 6–18) was carried out at 0, 3, 7, 14, 21, 35, 49 and 70 days after hatching. Freeze‐dried samples of whole bodies (digestive contents removed) were analysed for ash, and macrominerals (calcium, magnesium, phosphorus, potassium, sodium) and microminerals (copper, iron, manganese, nickel, selenium, zinc). Ash concentration followed a curvilinear trend, with a maximum of 101.7 g/kg dry matter at 32.77 days. Individual mineral concentrations, expressed as a proportion of ash, were fluctuating over time, with the most prominent changes at 3 days and again at either 14 or 21 days. Dissimilar patterns in individual mineral concentrations resulted that ratios between minerals followed inconsistent patterns over time. Although mineral contents in absolute quantities can be described through modelling over the entire life cycle of the bird, it can be concluded that variable concentrations of individual minerals could complicate further model development. 相似文献
995.
Environmental correlations with mean, as well as seasonal, distribution and abundance of the meiofauna in two exposed beaches in the Swartkops Estuary, near Port Elizabeth, were elucidated. Population densities showed a direct relationship with particle size. Consequent on this, oxygen appeared to be the controlling factor although desiccation played a role in the intertidal distribution of meiofauna in sandy areas. Seasonal fluctuations in numbers were characterized by peaks occurring in spring and autumn. Variations of temperature and oxygen were found to be responsible for this pattern. The presence of the sand prawn Callianassa kraussi affected both vertical penetration and seasonal fluctuation of the meiofauna. Since fluctuation in nitrogen and chlorophyll a content of the substrate bore little relationship to the fluctuation of the meiofauna, it is concluded that food is not limiting in these areas. Biomass determinations revealed that nematodes, which were the dominant taxon, weighed 0,42 μg individual mean ash-free dry mass and harpacticoid copepods 0,47 μg. On this basis the standing crop biomass was 0,40 μm2 in the sandy areas and 0,07 g/m2 in the muddier areas, both to a depth of 20 cm. 相似文献
996.
Karin H. Jensen Lene J. Pedersen Anne Mette Giersing Hageisø Knud Erik Heller Erik Jørgensen Jan Ladewig 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(4):276-285
Abstract Ninetysix pigs, half females and half castrated males from 12 litters, were housed in 24 groups of 4 litter mates (2 females, 2 castrates). The pigs were weaned at 4 weeks of age and from the age of 115 days half of the groups were subjected to a schedule of unpredictable, inescapable electroshocks for 33 days, and half served as control. The adrenocortical reactivity to ACTH stimulation and to an emotional stressor (the procedure associated with initiation of blood collection) was measured in females, whereas the behavioural and pituitary-adrenocortical reactivity to an open field test was measured in castrates, as was the behavioural reactivity in a social test. Intermittent stress increased adrenocortical reactivity to ACTH stimulation significantly. This effect was present within the first week of intermittent stress (p < 0.06), but no difference was found after 4–5 weeks of stress. In contrast, the adrenocortical reactivity to additional emotional stressors was unaffected by stress after one week of intermittent stress, but increased after 4–5 weeks. In the open field test, centre location increased after one week of intermittent stress, whereas exploration decreased and walking and ambulation increased after 4–5 weeks of stress. In addition, 4–5 weeks of intermittent stress decreased aggressiveness in a social test. In conclusion, the change in reactivity to an additional acute stressor during intermittent stress appeared in different variables and contexts at different times during the course of intermittent stress. Thus, assessment of stress based on changed reactivity has to include several distinct measures of behavioural and hormonal reactivity. 相似文献
997.
S.J. Milton 《African Journal of Range and Forage Science》2013,30(2):54-58
Abstract Seeds of four indigenous plant species were sown in 1990 in small‐scale field trials in an arid, non‐seasonal rainfall region of the southern Karoo, South Africa. Seeds of a winter annual Tetragonia echinata (Aizoaceae) showed innate dormancy but those of three perennial shrubs Pteronia empetrifolia, P. pollens and Osteospermum sinuatum (all Asteraceae) emerged only after the first substantial autumn rain. In good rangeland, seedling growth and survival was better in clearings than in undisturbed vegetation. In poor, continuously‐grazed rangeland, sheep had more influence on growth and survival of O. sinuatum seedlings than did vegetation clearing. These findings should be tested by means of large‐scale trials replicated in time and space. 相似文献
998.
999.
Hatt JM 《Schweizer Archiv für Tierheilkunde》2002,144(11):606-613
Pet birds are frequently viewed as difficult patients for anaesthesia. The present paper revises the current anaesthetic procedures for injectable and inhalant anaesthetics. Currently the method of choice for the anaesthesia of pet birds is the isoflurane inhalation anaesthesia. Special emphasis is given to the preanaesthetic preparations. Fasting is shorter for pet birds than for mammals. Anaesthetized birds are at special risk for hypothermia. Methods for the prevention of heat loss are given. The use of analgesics are recommended both for welfare reasons but also because of the possibility to reduce the concentration of inhalation anaesthetics and therefore the amount of possible exposure of personnel to waste gases. 相似文献
1000.
Genetic resistance to diseases is a multigenic trait governed mainly by the immune system and its interactions with many physiologic and environmental factors. In the adaptive immunity, T cell and B cell responses, the specific recognition of antigens and interactions between antigen presenting cells, T cells and B cells are crucial. It occurs through a network of mediator proteins such as the molecules of the major histocompatibility complex (MHC), T cell receptors, immunoglobulins and secreted proteins such as the cytokines and antibodies. The diversity of these proteins that mainly is due to an intrinsic polymorphism of the genes causes phenotypic variation in disease resistance. The well-known linkage of MHC polymorphism and Marek's disease resistance difference represents a classic model revealing immunological factors in resistance differences and diversity of mediator molecules. The molecular bases in any resistance variation to infectious pathogens are vaguely understood. This paper presents a review of the major immune mediators involved in resistance and susceptibility to infectious diseases and their functional mechanisms in the chicken. The genetic interaction of disease resistance with production traits and the environment is mentioned. 相似文献