全文获取类型
收费全文 | 564篇 |
免费 | 60篇 |
专业分类
林业 | 24篇 |
农学 | 11篇 |
基础科学 | 3篇 |
88篇 | |
综合类 | 61篇 |
农作物 | 20篇 |
水产渔业 | 34篇 |
畜牧兽医 | 319篇 |
园艺 | 13篇 |
植物保护 | 51篇 |
出版年
2023年 | 9篇 |
2022年 | 16篇 |
2021年 | 30篇 |
2020年 | 33篇 |
2019年 | 36篇 |
2018年 | 28篇 |
2017年 | 22篇 |
2016年 | 26篇 |
2015年 | 20篇 |
2014年 | 15篇 |
2013年 | 28篇 |
2012年 | 45篇 |
2011年 | 48篇 |
2010年 | 30篇 |
2009年 | 19篇 |
2008年 | 35篇 |
2007年 | 26篇 |
2006年 | 21篇 |
2005年 | 20篇 |
2004年 | 23篇 |
2003年 | 14篇 |
2002年 | 14篇 |
2001年 | 6篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1958年 | 1篇 |
1950年 | 1篇 |
1939年 | 1篇 |
1926年 | 1篇 |
1903年 | 2篇 |
1900年 | 1篇 |
排序方式: 共有624条查询结果,搜索用时 437 毫秒
201.
Carl A Bradbrook Louise Clark Alexandra HA Dugdale John Burford Martina Mosing 《Veterinary anaesthesia and analgesia》2013,40(4):382-389
Objective The aim of this study was to investigate normal values for the dynamic compliance of the respiratory system (Crs) and respiratory system resistance (Rrs) in mechanically ventilated anaesthetized dogs.Study design Prospective clinical study.Animals Forty healthy dogs undergoing elective orthopaedic surgery. Body weight was (mean ± SD) 26.8 ± 10.7 kg (range: 1.9–45.0 kg), age 4.7 ± 2.9 years (range: 0.1–10.6 years).Methods Dogs were premedicated with acepromazine and methadone administered intramuscularly and anaesthesia induced with propofol intravenously. After endotracheal intubation the dog's lungs were connected to an appropriate breathing system depending on body weight and isoflurane in oxygen administered for maintenance of anaesthesia. The lungs were ventilated mechanically with variables set to maintain normocapnia (end‐tidal carbon dioxide concentration 4.7–6.0 kPa). Peak inspiratory pressure, Crs, Rrs, tidal volume, respiratory rate and positive end‐expiratory pressure were recorded at 5, 30, 60, 90 and 120 minutes after start of mechanical ventilation. Cardiovascular variables were recorded at time of collection of respiratory data.Results General additive modeling revealed the following relationships: Crs = [0.895 × body weight (kg)] + 8.845 and Rrs = [?0.0966 × body weight (kg)] + 6.965. Body weight and endotracheal tube diameter were associated with Crs (p <0.001 and p =0.002 respectively) and Rrs (p = 0.017 and p =0.002 respectively), body weight being linearly related to Crs and inversely to Rrs.Conclusion and clinical relevance Body weight was linearly related to Crs while Rrs has an inverse linear relationship with body weight in mechanically ventilated dogs. The derived values of Crs and Rrs may be used for monitoring of lung function and ventilation in healthy dogs under anaesthesia. 相似文献
202.
Alexandra Wagstaffe H. Nick Battey 《The Journal of Horticultural Science and Biotechnology》2013,88(6):1086-1092
SummaryTemperature regimes that induce and ameliorate cropping troughs (“thermodormancy”) were evaluated over two seasons for the everbearing strawberry ‘Everest’. When plants were exposed to 26°C for 5, 10, 20 or 30 d in July, heat-induced troughs in cropping were observed in August. An important discovery was that cool (13°C) night temperatures ameliorated the severity of thermodormancy. In this study, thermodormancy appeared to be due principally to flower abortion post-anthesis, as large numbers of flowers emerged in mid-July, during the high temperature treatments, but went on to produce low fruit numbers in mid-August. Flower initiation itself (monitored by crown dissection) was not reduced by high temperatures. The observation that night-time temperature is critical for thermodormancy has significance for commercial production, in which protected cropping tends to increase average temperatures throughout the season, and venting tends to focus on day-time temperatures. 相似文献
203.
Anika Hudewenz Alexandra-Maria Klein Christoph Scherber Lea Stanke Teja Tscharntke Anja Vogel Alexandra Weigelt Wolfgang W. Weisser Anne Ebeling 《Biological conservation》2012,150(1):42-52
Agricultural intensification is a major driver of global environmental change. Disentangling the relative impact of losses in plant species richness and intensified management on higher trophic level organisms is important for conservation recommendations.We established different management regimes along an experimental gradient of plant species richness within “The Jena-Experiment” in Germany and quantified herbivory as well as grasshoppers and pollinators. Herbivory, grasshopper density and species richness and frequency of flower visiting pollinators were recorded two times in each of four subplots of altogether 80 plots differing in plant species richness. Each of the four subplots was subject to four different levels of fertilizer application and mowing to simulate very low, low, high and very high land use intensity.Fertilization and mowing significantly affected plant–herbivore interactions but plant species richness had no discernible effect. Grasshoppers were most abundant at high intensity subplots (3.1 individuals per m2) and least abundant on very low intensity subplots (1.3 individuals per m2). Leaf damage caused by herbivores was highest in even the very high intensity subplots (3.7%) with four mowing events per year and high amounts of fertilizer application and lowest on subplots with a low management intensity (2.4%) comprising two mowing events per year but no fertilizer application. In contrast, pollinators benefited most from lower management intensities, with only one or two mowing events and no fertilizer addition. In addition, higher numbers of flowering plant species and increased blossom cover was associated with enhanced pollinator species richness and flower visitation.Our results indicate that even in grasslands with high plant species richness, mowing and fertilization are more important drivers of herbivory and flower visitation by pollinators. Management with no more than two cuts per year and without fertilizer application in our grasslands balanced the ecosystem functions of increased pollination and decreased herbivory. 相似文献
204.
205.
Alexandra S. Silchenko Anatoly I. Kalinovsky Sergey A. Avilov Pelageya V. Andrijaschenko Roman S. Popov Pavel S. Dmitrenok Ekaterina A. Chingizova Vladimir I. Kalinin 《Marine drugs》2021,19(4)
Nine new mono-, di-, and trisulfated triterpene penta- and hexaosides, kurilosides A3 (1), D1 (2), G (3), H (4), I (5), I1 (6), J (7), K (8), and K1 (9) and two desulfated derivatives, DS-kuriloside L (10), having a trisaccharide branched chain, and DS-kuriloside M (11), having hexa-nor-lanostane aglycone with a 7(8)-double bond, have been isolated from the Far-Eastern deep-water sea cucumber Thyonidium (=Duasmodactyla) kurilensis (Levin) and their structures were elucidated based on 2D NMR spectroscopy and HR-ESI mass-spectrometry. Five earlier unknown carbohydrate chains and two aglycones (having a 16β,(20S)-dihydroxy-fragment and a 16β-acetoxy,(20S)-hydroxy fragment) were found in these glycosides. All the glycosides 1–9 have a sulfate group at C-6 Glc, attached to C-4 Xyl1, while the positions of the other sulfate groups vary in different groups of kurilosides. The analysis of the structural features of the aglycones and the carbohydrate chains of all the glycosides of T. kurilensis showed their biogenetic relationships. Cytotoxic activities of the compounds 1–9 against mouse neuroblastoma Neuro 2a, normal epithelial JB-6 cells, and erythrocytes were studied. The highest cytotoxicity in the series was demonstrated by trisulfated hexaoside kuriloside H (4), having acetoxy-groups at C(16) and C(20), the latter one obviously compensated the absence of a side chain, essential for the membranolytic action of the glycosides. Kuriloside I1 (6), differing from 4 in the lacking of a terminal glucose residue in the bottom semi-chain, was slightly less active. The compounds 1–3, 5, and 8 did not demonstrate cytotoxic activity due to the presence of hydroxyl groups in their aglycones. 相似文献
206.
207.
ter Halle A Wiszniowski J Hitmi A Ledoigt G Bonnemoy F Bonnet JL Bohatier J Richard C 《Pest management science》2009,65(1):14-18
BACKGROUND: Sulcotrione is a selective herbicide marketed for use in maize since 1993, but its environmental fate is not yet fully elucidated. A major metabolite resulting from cleavage between the two ring moieties, leading to 2‐chloro‐4‐mesylbenzoic acid (CMBA), has been identified; it presents a rather low toxicity. In photochemical studies this compound has also been claimed to be formed in high proportions. The present authors recently found that, under irradiation, sulcotrione mainly yields a cyclization product (CP). Thus, Sulcotrione photochemistry is still a matter of debate. The aim of the present work was to give an unequivocal answer to this issue. The potential toxicity of CP, CMBA and sulcotrione towards three organisms considered as representative of aquatic ecosystems was also evaluated. RESULTS: The main transformation product of sulcotrione is the cyclization product (CP), and CMBA is formed in smaller amounts. For the toxicological approach, the tested organisms were a bacterium, Vibrio fischeri (Bejerinck) Lehmann & Neumann, an alga, Pseudokirchneriella subcapitata (Korshikov) Hindak, and a protozoan, Tetrahymena pyriformis (Ehrenberg) Lwoff. Sulcotrione is more harmful towards the alga, but CP is more toxic to the bacterium and the protozoan. It must be noted that the measured toxicities are nonetheless rather low. CONCLUSION: On irradiation, sulcotrione mainly gives the photocyclization product, which presents a higher toxicity than sulcotrione and CMBA. This cyclization product should thus be considered in sulcotrione environmental risk assessment. Copyright © 2008 Society of Chemical Industry 相似文献
208.
209.
210.