全文获取类型
收费全文 | 98751篇 |
免费 | 6037篇 |
国内免费 | 46篇 |
专业分类
林业 | 4508篇 |
农学 | 3821篇 |
基础科学 | 685篇 |
13135篇 | |
综合类 | 13819篇 |
农作物 | 3725篇 |
水产渔业 | 5728篇 |
畜牧兽医 | 51577篇 |
园艺 | 1315篇 |
植物保护 | 6521篇 |
出版年
2021年 | 804篇 |
2020年 | 909篇 |
2019年 | 1085篇 |
2018年 | 1946篇 |
2017年 | 2235篇 |
2016年 | 2048篇 |
2015年 | 1689篇 |
2014年 | 2065篇 |
2013年 | 4206篇 |
2012年 | 3528篇 |
2011年 | 4109篇 |
2010年 | 2620篇 |
2009年 | 2620篇 |
2008年 | 3891篇 |
2007年 | 3610篇 |
2006年 | 3484篇 |
2005年 | 3015篇 |
2004年 | 2867篇 |
2003年 | 2882篇 |
2002年 | 2615篇 |
2001年 | 3572篇 |
2000年 | 3489篇 |
1999年 | 2697篇 |
1998年 | 1021篇 |
1997年 | 1083篇 |
1996年 | 924篇 |
1995年 | 1044篇 |
1994年 | 918篇 |
1993年 | 917篇 |
1992年 | 1959篇 |
1991年 | 2013篇 |
1990年 | 1944篇 |
1989年 | 1963篇 |
1988年 | 1714篇 |
1987年 | 1696篇 |
1986年 | 1727篇 |
1985年 | 1621篇 |
1984年 | 1290篇 |
1983年 | 1098篇 |
1982年 | 756篇 |
1979年 | 1152篇 |
1978年 | 891篇 |
1975年 | 854篇 |
1974年 | 978篇 |
1973年 | 931篇 |
1972年 | 895篇 |
1971年 | 874篇 |
1970年 | 822篇 |
1969年 | 807篇 |
1967年 | 761篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
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
992.
993.
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.
García-Bocanegra I Arenas-Montes A Lorca-Oró C Pujols J González MA Napp S Gómez-Guillamón F Zorrilla I Miguel ES Arenas A 《Veterinary research》2011,42(1):88
ABSTRACT: Although the importance of wild ruminants as potential reservoirs of bluetongue virus (BTV) has been suggested, the role played by these species in the epidemiology of BT in Europe is still unclear. We carried out a serologic and virologic survey to assess the role of wild ruminants in the transmission and maintenance of BTV in Andalusia (southern Spain) between 2006 and 2010.A total of 473 out of 1339 (35.3%) wild ruminants analyzed showed antibodies against BTV by both ELISA and serum neutralization test (SNT). The presence of neutralizing antibodies to BTV-1 and BTV-4 were detected in the four species analyzed (red deer, roe deer, fallow deer and mouflon), while seropositivity against BTV-8 was found in red deer, fallow deer and mouflon but not in roe deer. Statistically significant differences were found among species, ages and sampling regions. BTV RNA was detected in twenty-one out of 1013 wild ruminants (2.1%) tested. BTV-1 and BTV-4 RNA were confirmed in red deer and mouflon by specific rRT-PCR.BTV-1 and BTV-4 seropositive and RNA positive wild ruminants, including juveniles and sub-adults, were detected years after the last outbreak was reported in livestock. In addition, between the 2008/2009 and the 2010/2011 hunting seasons, the seroprevalence against BTV-1, BTV-4 and BTV-8 increased in the majority of provinces, and these serotypes were detected in many areas where BTV outbreaks were not reported in domestic ruminants. The results indicate that wild ruminants seem to be implicated in the dissemination and persistence of BTV in Spain. 相似文献
996.
Claerhoudt S Bergman EH van der Veen H Vanderperren K Raes EV Saunders JH 《Anatomia, histologia, embryologia》2011,40(1):55-60
The morphological features of the distal border synovial invaginations (SI) of the distal sesamoid bone (DSB) in horses were described by the use of computed tomography (CT). Transverse CT images were obtained on 50 cadaver forefeet from 25 Warmblood horses. Dorsal and sagittal planes were reformatted. The CT images allowed the evaluation of the number, shape, depth of penetration and direction of the SI into the bone. The total number of SI was 295 (mean 5.9). The number of invaginations in a particular DSB ranged from 3 (n = 3), 4 (n = 6), 5 (n = 11), 6 (n = 12), 7 (n = 13), 8 (n = 3), 9 (n = 1) to 11 (n = 1). The shape of the SI was 'conical' (n = 118), 'linear' (n = 109), 'lollipop' (n = 38) or 'branched' (n = 30). Penetration of the SI into the DSB was 'mild' in 195 cases, 'moderate' in 67 cases and 'deep' in 33 cases. The SI ran in a 'straight', 'dorsoproximal' and 'palmaroproximal' direction in 187, 28 and 80 cases, respectively. In only six DSBs, all SI ran in the same direction. The images obtained in this study may serve as reference for the radiographic evaluation of these SI. 相似文献
997.
Quintal AP Ribeiro Ede S Rodrigues FP Rocha FS Floeter-Winter LM Nunes CM 《Veterinary parasitology》2011,176(2-3):112-119
Leishmaniasis is kept in nature by the participation of several animal species. This study evaluated the presence of Leishmania spp. in skin samples of free-ranging marsupials Micoureus paraguayanus (n=95) and Didelphis albiventris (n=191), captured in Morro do Diabo State Park and in sections of its surrounding forest, in the region of Pontal do Paranapanema, S?o Paulo State, Brazil. The samples were tested for the presence of kDNA of Leishmania spp. by polymerase chain reaction (PCR) and by real time PCR (qPCR). All samples from D. albiventris tested by PCR were negative for the presence of kDNA of Leishmania spp. However, when tested by qPCR, the positivity was 1.6%. A positivity of 7.4% by PCR and 11.6% by qPCR was observed for M. paraguayanus. Sixty-four per cent (9/14) of positive animals were limited to the same forest fragment. Presence of Leishmania (Leishmania) amazonensis and Leishmania (Viannia) braziliensis was detected in M. paraguayanus samples. While D. albiventris is the most studied marsupial species due to its urban habits, other marsupial species such as M. paraguayanus can be potential reservoirs of Leishmania spp. and should also be studied. 相似文献
998.
Abattoir data collected from three British pig health monitoring schemes were combined to investigate the associations between Salmonella infection and the presence of gross lesions detected in slaughtered pigs. Each set of results was linked back to the farm from which the pigs were submitted, and the Salmonella results and lesions reports were connected at farm level. Salmonella infection was determined through meat juice ELISA (MJE), and the health conditions were assessed by postmortem inspection. The final dataset contained 873 slapmarks, with an average of 215 samples tested by MJE, and 355 pigs that were assessed for health conditions, per slapmark. Each of the health assessment conditions was individually analysed by regression models to investigate associations with the MJE results, accounting for clustering at the slapmark level and also for seasonality. A multivariable model was also used to estimate the strength of association with MJE results when all the health conditions were entered into the model. The results showed positive associations between Salmonella and enzootic pneumonia-like lesions, milk spots, peritonitis and pericarditis. 相似文献
999.
Guil-Luna S Sánchez-Céspedes R Millán Y De Andrés FJ Rollón E Domingo V Guscetti F Martín de Las Mulas J 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2011,25(3):518-523
Background: Progesterone receptor (PR) antagonist aglepristone (RU534) has been used successfully for pregnancy termination and therapy of pyometra, vaginal tumors, and mammary hyperplasia in bitches and queens. All of these conditions share with canine mammary carcinomas the expression of PR. Objectives: To study the effect of RU534 on proliferation and apoptosis in canine mammary carcinomas in relation to PR expression. Animals: Twenty‐seven nonspayed bitches with mammary carcinomas were treated with either 2 doses of 20 mg/kg RU534 (n = 22, RU534‐treated group) or oil placebo (n = 5, control group) on days 1 and 8. Methods: Tumor samples were collected before (day 1) and after (day 15) treatment for immunohistochemistry. PR expression, proliferation index (PI), and apoptotic index (AI) were determined using antibodies against PR, Ki67, and cleaved lamin A/C antigens, respectively. The effect of treatment on these parameters was analyzed. Results: Differential expression of PR between day 1 (59.1% PR‐positive tumors) and day 15 (36.4% PR‐positive tumors) was observed in RU534‐treated tumors exclusively. After RU534 treatment, mean PI was significantly decreased in PR‐positive but unchanged in PR‐negative RU534‐treated tumors. A reduction of ≥20% in PI was found in 61.5% of RU534‐treated tumors with PR expression. Conversely, no effect on AI was observed after RU534 treatment. Conclusions and Clinical Importance: Neoadjuvant RU534 treatment had PR expression‐related inhibiting effects on proliferation of canine mammary carcinoma cells. 相似文献
1000.