全文获取类型
收费全文 | 718篇 |
免费 | 26篇 |
专业分类
林业 | 96篇 |
农学 | 23篇 |
基础科学 | 3篇 |
226篇 | |
综合类 | 32篇 |
农作物 | 66篇 |
水产渔业 | 44篇 |
畜牧兽医 | 185篇 |
园艺 | 15篇 |
植物保护 | 54篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 10篇 |
2021年 | 23篇 |
2020年 | 24篇 |
2019年 | 35篇 |
2018年 | 27篇 |
2017年 | 21篇 |
2016年 | 27篇 |
2015年 | 16篇 |
2014年 | 31篇 |
2013年 | 34篇 |
2012年 | 61篇 |
2011年 | 69篇 |
2010年 | 48篇 |
2009年 | 25篇 |
2008年 | 47篇 |
2007年 | 52篇 |
2006年 | 32篇 |
2005年 | 33篇 |
2004年 | 34篇 |
2003年 | 29篇 |
2002年 | 24篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1974年 | 1篇 |
1972年 | 3篇 |
1971年 | 1篇 |
排序方式: 共有744条查询结果,搜索用时 15 毫秒
91.
José M. Molleda Isabel Cervantes Alba Galán Rodrigo Tardón† José M. Gallardo‡ Eva M. Martín-Suárez 《Veterinary ophthalmology》2008,11(S1):2-7
Purpose: To describe the protocol and appearance of fluorescein angiography (FA) in normal horses.
Animals: A total of 25 healthy horses aged between 5 and 15 years.
Materials and Methods: The horses were sedated with 15 µg/kg detomidine and 50 µg/kg butorphanol and dilated with topical tropicamide 1%. All angiograms were recorded after intravenous bolus injection of 10 mg/kg of fluorescein sodium solution.
Results: Two successive angiographic phases could be discerned: the choriopapillary phase, starting at 46.95 ± 9.48 s, and the retinal vascular phase, starting at 47.79 ± 10.38 s. The retinal vascular phase was divided in three parts: filling phase , maximum fluorescence point , and fading phase . During the filling phase, the dye progressed into the retinal vessels, obtaining maximum fluorescence at 59.79 ± 10.39 s, termed the maximum fluorescence point. The fading phase started immediately following the maximum fluorescence point. During this phase, vascular fluorescence decreased to complete reduction at 74.76 ± 9.81 s. Also, areas of delayed choroidal filling, the presence of short retinal vessels in the ventral region of the optic disc, and a particular filling of the optic disc were also observed.
Conclusions: The normal angiographic sequence was described in horses. FA may be a useful method for studying the integrity of the blood–retinal barriers in horses. 相似文献
Animals: A total of 25 healthy horses aged between 5 and 15 years.
Materials and Methods: The horses were sedated with 15 µg/kg detomidine and 50 µg/kg butorphanol and dilated with topical tropicamide 1%. All angiograms were recorded after intravenous bolus injection of 10 mg/kg of fluorescein sodium solution.
Results: Two successive angiographic phases could be discerned: the choriopapillary phase, starting at 46.95 ± 9.48 s, and the retinal vascular phase, starting at 47.79 ± 10.38 s. The retinal vascular phase was divided in three parts: filling phase , maximum fluorescence point , and fading phase . During the filling phase, the dye progressed into the retinal vessels, obtaining maximum fluorescence at 59.79 ± 10.39 s, termed the maximum fluorescence point. The fading phase started immediately following the maximum fluorescence point. During this phase, vascular fluorescence decreased to complete reduction at 74.76 ± 9.81 s. Also, areas of delayed choroidal filling, the presence of short retinal vessels in the ventral region of the optic disc, and a particular filling of the optic disc were also observed.
Conclusions: The normal angiographic sequence was described in horses. FA may be a useful method for studying the integrity of the blood–retinal barriers in horses. 相似文献
92.
Pouya Dini Kaatje Ducheyne Isabel Lemahieu Wendy Wambacq Hilde Vandaele Peter Daels 《Reproduction in domestic animals》2019,54(7):987-995
Several methods have been proposed to advance the onset of the breeding season in horses. Most of them are based on the exposure to an artificial lighting period combined with hormonal treatments. Mares exposed to an artificial photoperiod are most often housed indoors where the ambient temperature is often higher than the outside temperature. Mares held in barns are also exposed to different daylight intensities than horses kept outside, depending on the architecture. In the current study, we evaluated the impact of ambient temperature, daylight intensity and changes in body condition score (BCS) on the timing of first ovulation after winter anestrus in mares exposed to an artificial photoperiod. Mares (n = 211) were housed in barns with different ambient temperature and daylight exposure but with the same artificial photoperiod exposure (except for a natural photoperiod control group). Artificial photoperiod as well as an increase in BCS over the winter significantly advanced the first spring ovulation. The BCS at the start and end of the anestrus period did not have an effect on the interval to first ovulation and neither did the modest increase in ambient temperature in the barn. However, a higher light intensity during the daytime significantly advanced the first spring ovulation. The results of this study suggest that exposure to more sunlight advances the onset of the breeding season. This effect is likely mediated through the biological effect of short wavelength blue light and its impact on melatonin suppression and biological rhythms. We suggest that greater/direct exposure to the blue light component of daylight improves the response to the artificial photoperiod. The results of the present study can further assist to optimize the conditions that lead to an efficient spring transition of breeding mares. 相似文献
93.
Pouya Dini Lucas Troch Isabel Lemahieu Peter Deblende Peter Daels 《Reproduction in domestic animals》2019,54(8):1113-1120
The objective of this study was to evaluate the accuracy of a novel, portable device (iSperm® Equine for assessing concentration and motility of stallion semen). In the first experiment, semen concentration was determined by the iSperm® Equine (Aidmics Biotechnology), Androvision® (Minitube) and NucleoCounter® SP‐100? (ChemoMetec). The total motility and progressive motility were determined by the iSperm® Equine and the Androvision® using the manufacturer's guidelines. Frozen/thawed semen samples (n = 33) at various dilutions were analysed for concentration and motility with the above‐mentioned devices. There was a significant correlation between the concentrations measured with iSperm® and NucleoCounter® at all the measured dilutions. Moreover, <10% difference in concentrations was observed between the iSperm® and NucleoCounter® using the Bland–Altman test. There was also a significant correlation between iSperm® and Androvision® for total and progressive motility. In the second experiment, the parameters used in the Androvision® were modified to match those of the iSperm®. Total motility and progressive motility of frozen/thawed semen samples (n = 10) were determined, and the similarity between the Androvision® and iSperm® was confirmed by correlation studies and Bland–Altman test. The results of these experiments demonstrate that the iSperm® offers a reliable and practical alternative for the semi‐automated measurement of concentration and motility of stallion semen in the field. The iSperm® enables the practitioner to obtain objective and repeatable measurements on a variety of semen types (fresh, cooled and frozen) in the field at the time of insemination and thus acquire more insight into the quantity and quality of the provided insemination doses. This mare‐side diagnostic tool may help practitioners in identifying presumed subfertility problems more rapidly and act accordingly. 相似文献
94.
Maria Diaz‐Jimenez Jesús Dorado Blasa Pereira Cesar Consuegra Isabel Ortiz Manuel Hidalgo 《Reproduction in domestic animals》2019,54(Z4):102-105
Sperm from fertile donkeys have been successfully frozen in absence of permeable cryoprotectants. The aim of this study was to determine whether this cryopreservation method is suitable for subfertile donkeys in comparison to conventional sperm freezing with glycerol. Ejaculates were collected from four Andalusian Donkeys: three fertile and one subfertile. Semen was frozen with an extender containing glycerol (GLY), or adding instead sucrose 0.25 molar and 1% bovine serum albumin (SUC) as non‐permeable cryoprotectants. After thawing, samples were assessed for total (TM, %) and progressive (PM, %) sperm motility by CASA, plasma membrane integrity (PMI, %) by epifluorescence microscopy and DNA integrity (DFI, %) by SCSA. Results (mean ± SD) were compared between extenders in fertile and subfertile donkeys using the Student's t test. No differences between GLY and SUC treatments were found in the fertile group for the sperm parameters assessed. In subfertile donkey ejaculates, GLY resulted in significantly higher values than SUC for TM (25.5 ± 3.1 vs. 19.6 ± 1.9) and PM (13.3 ± 5.1 vs. 4.0 ± 1.2), respectively. In conclusion, considering all the sperm parameters assessed, sperm freezing in absence of permeable cryoprotectants may not be still an option for cryopreservation of subfertile donkey sperm. 相似文献
95.
Merryn McKinnon Mizaan Ahmad Meg Bongers Rory Chevalier Isabel Telfer Clare Van Dorssen 《Human Dimensions of Wildlife》2018,23(1):90-99
Culling kangaroos, Australia’s most abundant marsupial, is a controversial practice in the Australian Capital Territory (ACT). The ACT government introduced a kangaroo management plan in response to the growing kangaroo population causing damage in grassland ecosystems. Although some groups (e.g., local government, some researchers) support implementation of this plan, critics claim it is inhumane and lacks concrete evidence. To examine media portrayal of this debate, this study conducted a content analysis of newspaper coverage between 2006 and 2016. Although ACT newspapers were impartial in their presentation of the debate, sources that previous studies found were typically considered trustworthy to speak on the scientific validity of the program were found to have conflicting messages and be less represented in the media. Thus, future research should explore if the messenger is more important than the message in determining influences on public perceptions about the use of lethal control. 相似文献
96.
Juan Luis H. Cardós Isabel Martínez Victoria Calvo Gregorio Aragón 《Landscape Ecology》2016,31(9):1975-1995
Context
Mediterranean forests have been fragmented intensively over time, thereby yielding small and isolated forest remnants. They host a rich variety of epiphytes, which may be affected by landscape structure. Previous studies have analyzed the influence of habitat quality on these epiphytic communities, but there is little knowledge of the effects of other fragment features.Objectives
We evaluated the impacts of forest loss and fragmentation on epiphytic communities (lichens and bryophytes) at plot and fragment scales after controlling the variation in forest structure and management.Methods
We considered 40 fragments of dense oak forests in a human-modified landscape. We quantified their spatial attributes (size and shape), the quality of the surrounding matrix and the forest stand structure. We modeled community traits, and the presence and abundance of species at fragment and plot scales.Results
Fragment size, shape, and the quality of the surrounding matrix were key factors that affected epiphytic richness and diversity. Larger and more regularly shaped fragments hosted the richest and most diverse communities, possibly offering a larger core area and thus favoring the entry of typical forest species. A high-contrast matrix was only favorable in small fragments, probably allowing the arrival of propagules. The species-level response was highly variable.Conclusions
Landscape structure provides powerful explanations of the richness and diversity losses among epiphytes. Forest management should ensure the retention of the largest possible continuous forests. The management strategy of the matrix will depend on the conservation goal, since we observed different effects related with quality and fragment size.97.
de la Fuente J Atkinson MW Naranjo V Fernández de Mera IG Mangold AJ Keating KA Kocan KM 《Veterinary microbiology》2007,119(2-4):375-381
Anaplasma ovis (Rickettsiales: Anaplasmataceae) is a tick-borne pathogen of sheep, goats and wild ruminants. The genetic diversity of A. ovis strains has not been well characterized due to the lack of sequence information. In this study, we evaluated bighorn sheep (Ovis canadensis) and mule deer (Odocoileus hemionus) from Montana for infection with A. ovis by serology and sequence analysis of the msp4 gene. Antibodies to Anaplasma spp. were detected in 37% and 39% of bighorn sheep and mule deer analyzed, respectively. Four new msp4 genotypes were identified. The A. ovismsp4 sequences identified herein were analyzed together with sequences reported previously for the characterization of the genetic diversity of A. ovis strains in comparison with other Anaplasma spp. The results of these studies demonstrated that although A. ovismsp4 genotypes may vary among geographic regions and between sheep and deer hosts, the variation observed was less than the variation observed between A. marginale and A. phagocytophilum strains. The results reported herein further confirm that A. ovis infection occurs in natural wild ruminant populations in Western United States and that bighorn sheep and mule deer may serve as wildlife reservoirs of A. ovis. 相似文献
98.
A new procedure was developed for the isolation of highly purified water‐extractable arabinoxylan (WE‐AX) from hull‐less barley flour. It included inactivation of endogenous enzymes, removal of proteins with silica gel, and removing β‐glucans, arabinogalactan‐peptides, and starch fragments by enzyme or solvent precipitation steps. WE‐AX recovered by this isolation procedure represented, on average, 47% of all WE‐AX present in hull‐less barley flour. Purified WE‐AX from flour of different hull‐less European barley cultivars contained 84.9–91.8% AX and showed small structural differences. The apparent peak molecular weight of the purified WE‐AX was 730,000–250,000, and the arabinose‐to‐xylose ratio was 0.55–0.63. Proton nuclear magnetic resonance spectroscopy showed that the levels of un‐, O‐2 mono‐, O‐3 mono‐, and O‐2,O‐3 disubstituted xylose residues were 59.1–64.7%, 8.2–10.0%, 5.7–10.6%, and 17.6– 23.1%, respectively, and the ratio of di‐ to monosubstituted xylose was 0.90–1.54. Both O‐3 mono‐ and disubstituted xylose residues occurred isolated or next to disubstituted xylose residues in the WE‐AX chain. 相似文献
99.
100.
J. Dustin Loy Isabel Turney Harris D. L. Hank Harris Bruce H. Janke 《Journal of the World Aquaculture Society》2011,42(3):370-375
The necrotizing hepatopancreatitis bacterium (NHPB) is difficult to preserve and has not been propagated in vitro. NHPB can be maintained continuously by simply adding specific pathogen free (SPF) shrimp to tanks containing NHPB‐infected shrimp. However, obtaining large amounts of highly concentrated infectious material free of contaminating bacterial flora for repeating challenge experiments was found to be exceedingly difficult using the current published methods. Therefore, a system was implemented using visible implant elastomer (VIE) tags to identify animals within a propagation tank by introduction group. Utilizing this method allowed for continuous reproduction of NHP within propagation tanks and provided researchers with access to infectious material allowing for consistent replication of challenge experiments and concentrated material for preservation. 相似文献