全文获取类型
收费全文 | 548篇 |
免费 | 45篇 |
国内免费 | 2篇 |
专业分类
林业 | 16篇 |
农学 | 27篇 |
基础科学 | 1篇 |
71篇 | |
综合类 | 25篇 |
农作物 | 30篇 |
水产渔业 | 67篇 |
畜牧兽医 | 327篇 |
园艺 | 10篇 |
植物保护 | 21篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 16篇 |
2020年 | 25篇 |
2019年 | 33篇 |
2018年 | 32篇 |
2017年 | 18篇 |
2016年 | 29篇 |
2015年 | 13篇 |
2014年 | 27篇 |
2013年 | 55篇 |
2012年 | 37篇 |
2011年 | 33篇 |
2010年 | 31篇 |
2009年 | 24篇 |
2008年 | 21篇 |
2007年 | 21篇 |
2006年 | 19篇 |
2005年 | 6篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 17篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1969年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有595条查询结果,搜索用时 78 毫秒
91.
Samuel Luiz Fioreze João Paulo Costa Carneiro Daniela Dias Pinto João Domingos Rodrigues 《Journal of plant nutrition》2017,40(18):2602-2610
We characterized the pollination and fecundation times in soybean flowers and evaluated the effects of kinetin and calcium applications on physiological and productive traits of soybean plants during the reproductive stage. The anatomical study of flowers of eight soybean cultivars showed that fecundation occurred in closed flowers with visible petals, which presented embryo in the first cell divisions. These results indicate that fertilizers and growth regulation applications should be performed before flower opening, which is different from the current recommendation. Foliar applications of kinetin and calcium between the floral bud and full flowering stages did not affect carbon dioxide (CO2) assimilation, yield components and final yield. The results obtained in this research showed the lack of viability of foliar application of calcium and kinetin in order to increase pod set and number of seeds per plant in soybean crop. 相似文献
92.
Glaydson S. dos Reis Matthew A. Adebayo Carlos H. Sampaio Eder C. Lima Pascal S. Thue Irineu A. S. de Brum Silvio L. P. Dias Flavio A. Pavan 《Water, air, and soil pollution》2017,228(1):33
Sludge-derived activated carbons (ACs) were prepared by conventional heating and microwave pyrolysis. The ACs were characterized using several analytical and functional techniques and used for removal of six phenolic compounds from aqueous solutions. The adsorbents exhibited similar features and possessed hydrophobic surfaces. The ACs were assigned mesoporous materials, with specific surface areas of up to 641 and 540 m2 g?1 for CAC-500 and MAC-980, respectively. The preliminary results indicated that phenol removal onto the ACs increased in the order: m-cresol?<?phenol?<?o-cresol?<?2-chrorophenol?<?2-nitrophenol?<?hydroquinone. Hydroquinone exhibited the highest adsorption capacity and was chosen to continue the remaining part of the experimental work—kinetic and isothermal studies. The adsorption kinetic and isotherm data were well described by the Avrami fractionary order and Redlich–Peterson models, respectively. The maximum amounts (Q max) of hydroquinone adsorbed at 25 °C were too high, reaching 1218.3 and 1202.1 mg g?1 for CAC-500 and MAC-980, respectively. The mechanism of adsorption was proposed in this work, and it was suggested that donor–acceptor complex and π–π interactions play major roles in the adsorption process. The adsorbents were also tested on simulated effluents. The two ACs displayed good efficiency for the treatment of industrial simulated effluents. 相似文献
93.
Amanda B. Dias Carmen M.O. MüllerFábio D.S. Larotonda João B. Laurindo 《Journal of Cereal Science》2010
Rice flour is a starchy material with low-cost, because it can be produced from rice that is broken during processing. The aim of this study was to develop biodegradable films based on rice starch and rice flour, and to characterize their physicochemical, microscopic and mechanical properties. Films from rice starch and rice flour were prepared by casting, with glycerol or sorbitol as plasticizer. SEM analysis of starch and flour films revealed compact structures. Rice flour films prepared in the present work have similar mechanical properties to those of starch based films. However, their water vapor permeabilities are two times higher than those of starch based films. Films with sorbitol were less permeable to water and more rigid, while films with glycerol are more plasticized and have poorer water vapor barrier properties. Therefore, preparing edible films from rice flour is a new alternative for using this raw material, which is sometimes much cheaper than commercial starches. 相似文献
94.
J Bingham RA Lunt DJ Green KR Davies V Stevens FYK Wong 《Australian veterinary journal》2010,88(6):204-210
Objective To study the potential role of an Australian corvid, the little raven (Corvus mellori), in the surveillance for exotic West Nile virus (WNV) in Australia. Method In a series of trials, little ravens were infected with WNV (strain 4132 New York 1999) and Kunjin virus (strain K42886) by the intramuscular route. They were observed for 20 days during which blood and swab samples were taken for virus isolation. Tissue samples were taken from ravens humanely killed during the acute infection period, and at the termination of the trials, for virus isolation, histopathology and immunohistochemistry. Results Ravens infected with WNV became mildly ill, but all recovered and seroconverted. Blood virus titres peaked around 3 to 4 days after inoculation at levels between 103.0 to 107.5 plaque forming units/mL. Virus or viral antigen was detected in spleen, liver, lung, kidney, intestine, testis and ovary by virus isolation and/or immunohistochemistry. WNV was detected in oral and cloacal swabs from 2 to 7 days post inoculation. The molecular and pathogenic characteristics of the inocula were consistent with them being of high virulence, as expected for this isolate. Ravens infected with Kunjin virus developed viraemia and seroconverted, although they did not develop disease. Conclusions Little ravens do not develop severe disease in response to virulent WNV infection and for this reason may not be important sentinel hosts in the event of an outbreak of WNV, as in North America. However, as they have relatively high viraemias, they may be able to support virus cycles. 相似文献
95.
Sachin Kumar Flavia Militino Dias Baibaswata Nayak Peter L. Collins Siba K. Samal 《Veterinary research》2010,41(5)
Avian paramyxoviruses (APMV) are divided into nine serotypes. Newcastle disease virus (APMV-1) is the most extensively characterized, while relatively little information is available for the other APMV serotypes. In the present study, we examined the pathogenicity of two divergent strains of APMV-3, Netherlands and Wisconsin, in (i) 9-day-old embryonated chicken eggs, (ii) 1-day-old specific pathogen free (SPF) chicks and turkeys, and (iii) 2-week-old SPF chickens and turkeys. The mean death time in 9-day-old embryonated chicken eggs was 112 h for APMV-3 strain Netherlands and > 168 h for strain Wisconsin. The intracerebral pathogenicity index in 1-day-old chicks for strain Netherlands was 0.39 and for strain Wisconsin was zero. Thus, both strains are lentogenic. Both the strains replicated well in brain tissue when inoculated intracerebrally in 1-day-old SPF chicks, but without causing death. Mild respiratory disease signs were observed in 1-day-old chickens and turkeys when inoculated through oculonasal route with either strain. There were no overt signs of illness in 2-weeks-old chickens and turkeys by either strain, although all the birds seroconverted after infection. The viruses were isolated predominantly from brain, lungs, spleens, trachea, pancreas and kidney. Immunohistochemistry studies also showed the presence of large amount of viral antigens in both epithelial and sub-epithelial lining of respiratory and alimentary tracts. Our result suggests systemic spread of APMV-3 even though the viral fusion glycoprotein does not contain the canonical furin proteases cleavage site. Furthermore, there was little or no disease despite systemic viral spread and abundant viral replication in all the tissues tested. 相似文献
96.
MIN SU LEE JEFF KO AH RA LEE IN HYE LEE MI AE JUNG BRENDA AUSTIN HYUNWOO CHUNG SANGSOEP NAHM KIDONG EOM 《Veterinary radiology & ultrasound》2010,51(2):130-135
The purpose of this study was to assess the effects of four anesthetic protocols on normal canine brain uptake of 2‐deoxy‐2‐[18F]fluoro‐d ‐glucose (FDG) using positron emission tomography/computed tomography (PET/CT). Five clinically normal beagle dogs were anesthetized with (1) propofol/isoflurane, (2) medetomidine/pentobarbital, (3) xylazine/ketamine, and (4) medetomidine/tiletamine–zolazepam in a randomized cross‐over design. The standard uptake value (SUV) of FDG was obtained in the frontal, parietal, temporal and occipital lobes, cerebellum, brainstem and whole brain, and compared within and between anesthetic protocols using the Friedman test with significance set at P<0.05. Significant differences in SUVs were observed in various part of the brain associated with each anesthetic protocol. The SUV for the frontal and occipital lobes was significantly higher than in the brainstem in all dogs. Dogs receiving medetomidine/tiletamine–zolazepam also had significantly higher whole brain SUVs than the propofol/isoflurane group. We concluded that each anesthetic protocol exerted a different regional brain glucose uptake pattern. As a result, when comparing brain glucose uptake using PET/CT, one should consider the effects of anesthetic protocols on different regions of the glucose uptake in the dog's brain. 相似文献
97.
AH RA LEE MIN SU LEE IN SEONG JUNG DAE YOUNG KIM SANG SEOP NHAM HYUN WOO CHUNG KIDONG EOM 《Veterinary radiology & ultrasound》2010,51(2):145-147
An 8‐year‐old Shih Tzu developed abdominal pain and hyperglobulinemia. A round splenic mass was noted radiographically and sonographically. The patient was evaluated by fluorodeoxyglucose positron emission tomography coupled with computed tomography (FDG‐PET/CT). There was no evidence of metastasis or bone marrow involvement on PET/CT images. The standardized uptake value (SUV) of the splenic mass was increased over the reference range (SUV=4.83). The patient was diagnosed as splenic extramedullary plasmacytoma through immunohistopathologic study. After the splenectomy, the globulin level normalized and the patient is alive without complications. 相似文献
98.
Land-use and land-cover change processes in the Upper Uruguay Basin: linking environmental and socioeconomic variables 总被引:1,自引:0,他引:1
de Freitas Marcos Wellausen Dias Santos João Roberto dos Alves Diógenes Salas 《Landscape Ecology》2013,28(2):311-327
Landscape Ecology - Land-use and land-cover change affects both ecological and socioeconomic processes, motivating the integration of environmental and socioeconomic data to help understand this... 相似文献
99.
Maria João Verdasca Ana Sofia Leitão Joana Santana Miguel Porto Susana Dias Pedro Beja 《Biological conservation》2012,146(1):14-23
In cultural landscapes there are often negative biodiversity consequences of agricultural abandonment and subsequent scrub and forest encroachment, due to homogenization and the loss of early-successional habitats. The common forestry practice of removing understory vegetation to prevent fire hazard (fuel management) probably has the side-effect of ameliorating these consequences, but it is uncertain whether it effectively restores habitats for early-successional species. Here we examine the influence of time since fuel management and management frequency on butterfly assemblages, using a chronosequence of cork oak (Quercus suber) stands spanning about 70 years. Overall species richness increased immediately after management and abundances peaked about 2–3 years later, while both declined thereafter for about 10–20 years to pre-disturbance levels. Richness and abundances were also much higher in recurrently managed stands. Most life history groups showed successional trends similar to the overall species richness and abundances, though consistent positive effects of fuel management were only observed for species with univoltine life cycle, herbaceous layer feeding, larval overwintering, and intermediate body size. Individual species were largely associated with recent and recurrent management, though a few specialists occurred most often in undisturbed stands. These findings suggest that fuel management at <10 years intervals is strongly positive for butterfly assemblages in landscapes under land abandonment. However, to maintain the overall forest biodiversity it is critical that patches of undisturbed habitat are also retained at the landscape scale. 相似文献
100.
CA Letelier MA Sanchez RA Garcia‐Fernandez B Sanchez P Garcia‐Palencia A Gonzalez‐Bulnes JM Flores 《Reproduction in domestic animals》2011,46(3):481-488
The aim of the current study was to determine the possible effects of progestagen oestrous synchronization on vascular endothelial growth factor (VEGF) expression during sheep luteogenesis and the peri‐implantation period and the relationship with luteal function. At days 9, 11, 13, 15, 17 and 21 of pregnancy, the ovaries from 30 progestagen treated and 30 ewes cycling after cloprostenol injection were evaluated by ultrasonography and, thereafter, collected and processed for immunohistochemical evaluation of VEGF; blood samples were drawn for evaluating plasma progesterone. The progestagen‐treated group showed smaller corpora lutea than cloprostenol‐treated and lower progesterone secretion. The expression of VEGF in the luteal cells increased with time in the cloprostenol group, but not in the progestagen‐treated group, which even showed a decrease between days 11 and 13. In progestagen‐treated sheep, VEGF expression in granulosa‐derived parenchymal lobule capillaries was correlated with the size of the luteal tissue, larger corpora lutea had higher expression, and tended to have a higher progesterone secretion. In conclusion, the current study indicates the existence of deleterious effects from exogenous progestagen treatments on progesterone secretion from induced corpora lutea, which correlate with alterations in the expression of VEGF in the luteal tissue and, this, presumably in the processes of neoangiogenesis and luteogenesis. 相似文献