全文获取类型
| 收费全文 | 11646篇 |
| 免费 | 855篇 |
专业分类
| 林业 | 1201篇 |
| 农学 | 431篇 |
| 基础科学 | 45篇 |
| 2642篇 | |
| 综合类 | 725篇 |
| 农作物 | 512篇 |
| 水产渔业 | 821篇 |
| 畜牧兽医 | 4735篇 |
| 园艺 | 289篇 |
| 植物保护 | 1100篇 |
出版年
| 2023年 | 104篇 |
| 2022年 | 138篇 |
| 2021年 | 252篇 |
| 2020年 | 239篇 |
| 2019年 | 180篇 |
| 2018年 | 568篇 |
| 2017年 | 551篇 |
| 2016年 | 492篇 |
| 2015年 | 391篇 |
| 2014年 | 449篇 |
| 2013年 | 665篇 |
| 2012年 | 931篇 |
| 2011年 | 849篇 |
| 2010年 | 462篇 |
| 2009年 | 358篇 |
| 2008年 | 715篇 |
| 2007年 | 676篇 |
| 2006年 | 540篇 |
| 2005年 | 562篇 |
| 2004年 | 515篇 |
| 2003年 | 477篇 |
| 2002年 | 388篇 |
| 2001年 | 275篇 |
| 2000年 | 245篇 |
| 1999年 | 218篇 |
| 1998年 | 70篇 |
| 1997年 | 55篇 |
| 1996年 | 42篇 |
| 1995年 | 62篇 |
| 1994年 | 37篇 |
| 1993年 | 34篇 |
| 1992年 | 81篇 |
| 1991年 | 69篇 |
| 1990年 | 60篇 |
| 1989年 | 56篇 |
| 1988年 | 52篇 |
| 1987年 | 46篇 |
| 1986年 | 47篇 |
| 1985年 | 46篇 |
| 1984年 | 42篇 |
| 1983年 | 34篇 |
| 1979年 | 37篇 |
| 1974年 | 26篇 |
| 1973年 | 21篇 |
| 1972年 | 22篇 |
| 1971年 | 23篇 |
| 1970年 | 27篇 |
| 1969年 | 25篇 |
| 1968年 | 25篇 |
| 1967年 | 21篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
71.
Andrea Weissman Mauricio Solano Olivier Taeymans Shannon P. Holmes David Jiménez Bruce Barton 《Veterinary radiology & ultrasound》2016,57(2):124-129
An imaging report is a vital communication tool between a radiologist and clinician. In a field where in‐person communication may not be readily available, it is imperative that the report clearly relays pertinent clinical information in a timely manner. The purpose of this observational study was to describe and compare opinions and expectations of small animal general practitioners, veterinary specialists, and veterinary radiologists regarding the imaging report. Online surveys were distributed, and data were collected from 202 veterinary clinicians and 123 veterinary radiologists. The majority (89%) of clinicians were satisfied with their imaging reports and stated that they read the radiology report as soon as it was available (92%). Just less than half (48%) of clinicians indicated it was standard of care that a board‐certified veterinary radiologist read all imaging studies. Radiologists and clinicians agreed that a clinical history (98% and 94%, respectively) and clinical question (82% and 68%, respectively) were needed to generate a good radiology report. Fifty‐five percent to 70% of clinicians prefer red bulleted reports, which included incidental findings (96%); while radiologists slightly favored prose reporting (37–46%). Clinicians found it helpful when additional imaging (86%), medical (71%), and surgical recommendations (73%) were made. About one‐third of specialists who had been in practice for >11 years thought they were better able to interpret imaging for their own specialty than the radiologist. Clinicians voiced discontentment with reports that were not completed in a timely manner or did not give a prioritized differential list. Further studies are warranted to provide a more in‐depth evaluation of veterinary radiology reporting structure and style. 相似文献
72.
73.
Analgesic efficacy of an oral transmucosal spray formulation of meloxicam alone or in combination with tramadol in cats with naturally occurring osteoarthritis 
下载免费PDF全文
下载免费PDF全文 74.
75.
The African Penguin (Spheniscus demersus) has suffered population declines and is listed in the IUCN Red List as Endangered. The species is endemic to the coast of southern Africa, and breeding colonies are distributed on the south-western coast of Africa. Currently, African Penguins are being kept in zoo and aquarium facilities throughout South Africa. In this study, molecular genetic data based on 12 microsatellite markers from 1 119 African Penguin samples from four facilities were generated in order to determine the level of genetic variation, population structure and differentiation, and effective population size to assist in the development of an effective captive management plan. Expected heterozygosity ranged from 0.57 to 0.62, and allelic richness from 4.2 to 5.1. However, based on differences between first- and second-generation captive birds, we conclude that the ex situ population is at risk of losing genetic variability in the future and management programmes should include exchange of birds between captive facilities in order to induce gene flow and increase effective population size. Adding individuals from in situ populations should also be considered in the future in cases where these birds cannot be rehabilitated. Molecular genetic analyses of wild penguin populations should be carried out for comparison, and to ascertain to what degree ‘in situ genetic diversity’ is represented among ex situ populations. With regular resampling and analyses, the extent of the effect of processes such as genetic drift on diversity in the ex situ penguin populations will become evident. 相似文献
76.
Fabien Génin Ayabulela Yokwana Nokuthula Kom Sébastien Couette Thibault Dieuleveut Stephen D Nash 《African Zoology》2016,51(3):135-143
The primate fauna of South Africa has historically been viewed as comprising three diurnal cercopithecoid taxa – chacma baboons (Papio ursinus), vervet (Chlorocebus pygerythrus) and samango monkeys (Cercopithecus albogularis) – and two nocturnal lorisoid species – the thick-tailed greater galago (Otolemur crassicaudatus) and the southern lesser galago (Galago moholi). Here we report the positive identification of a third galago species within South Africa’s borders: the Mozambique dwarf galago or Grant’s galago, Galagoides granti (Thomas and Wroughton, 1907). The taxon was previously held to be restricted to Mozambique, eastern Zimbabwe, Malawi and Tanzania, but we have also observed it in the sand forest of Tembe Elephant Park and the Tshanini Community Reserve, near the Mozambique border. The species was formerly mistaken for Galago moholi, erroneously (we believe) extending the range of the latter species into northern KwaZulu-Natal. In South Africa the two small galagos are unlikely to have overlapping ranges: Galago moholi prefers dry savanna woodlands, whereas Galagoides granti is apparently confined to dry sand forest. However, both species may coexist with the larger and more widespread Otolemur crassicaudatus, an inhabitant of moist savanna, forest edge and thicket. The true South African ranges of both small galago species need to be ascertained. 相似文献
77.
In Tunisia both Psammomys obesus and P. vexillaris are found. These taxa have been the subject of taxonomic controversy for some time, due to variability in the classical morphological characters used for taxonomic recognition. In this study we investigated skull size and shape variation in the genus Psammomys by using geometric morphometrics to evaluate the extent of intra- and interspecific shape variation and explicitly tested for the impact of allometric shape variation on species discrimination. Eleven populations of the two species from 10 localities in Tunisia were studied. Statistical analyses of size and shape showed large size variation within P. obesus, but no shape differences were revealed among populations of this species. Interspecific analysis revealed that P. vexillaris had the smallest skull. Principal component analysis and Procrustes distances showed good discrimination between the two species after removal of the allometric component of shape variation. The results obtained show that allometric-related shape variation could mask discrimination between the two Psammomys species. This finding might explain the uncertainty in classification of these species in the past. The interspecific allometric-free phenotypic differences observed may be associated with adaptive processes linked to the different environmental and trophic preferences of the two species. 相似文献
78.
Comparison of 4 point‐of‐care blood gas analyzers for arterial blood gas analysis in healthy dogs and dogs with cardiopulmonary disease 下载免费PDF全文
下载免费PDF全文 79.