全文获取类型
收费全文 | 1353篇 |
免费 | 70篇 |
国内免费 | 2篇 |
专业分类
林业 | 96篇 |
农学 | 35篇 |
基础科学 | 16篇 |
236篇 | |
综合类 | 182篇 |
农作物 | 34篇 |
水产渔业 | 147篇 |
畜牧兽医 | 479篇 |
园艺 | 32篇 |
植物保护 | 168篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 25篇 |
2020年 | 22篇 |
2019年 | 33篇 |
2018年 | 30篇 |
2017年 | 30篇 |
2016年 | 40篇 |
2015年 | 27篇 |
2014年 | 38篇 |
2013年 | 45篇 |
2012年 | 91篇 |
2011年 | 82篇 |
2010年 | 56篇 |
2009年 | 45篇 |
2008年 | 100篇 |
2007年 | 97篇 |
2006年 | 90篇 |
2005年 | 72篇 |
2004年 | 80篇 |
2003年 | 62篇 |
2002年 | 64篇 |
2001年 | 30篇 |
2000年 | 15篇 |
1999年 | 17篇 |
1998年 | 18篇 |
1997年 | 16篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 12篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1961年 | 2篇 |
1942年 | 3篇 |
排序方式: 共有1425条查询结果,搜索用时 31 毫秒
991.
Ian D. Jones Virginia Luis Fuentes Adrian Boswood Melanie J. Hezzell David Wrigglesworth Ana Mateus Walasinee Moonarmart Jonathan Elliott 《Journal of Veterinary Cardiology》2012,14(1):203-210
ObjectivesTo measure flow-mediated vasodilation (FMD) in healthy dogs and in client-owned dogs with chronic valvular disease (CVD) and to investigate possible correlations between markers of CVD severity and FMD.AnimalsTwelve dogs with CVD and 11 healthy weight-matched dogs.MethodsBrachial artery FMD following 5 min inflation of a cuff around the antebrachium was measured in 12 dogs with CVD and 11 healthy weight-matched dogs. Measurements were also obtained in the healthy dogs 5 min after cuff placement but without inflation (‘sham cuff placement’). Dogs with CVD underwent echocardiography to confirm and characterize their disease.ResultsIn healthy dogs (median age 4 [2–6] years), median FMD was 7.7% versus 3.4% with sham cuff placement (P = 0.003). In dogs with CVD (median age 8 [4–16] years) median FMD was 5.5% versus 7.7% in healthy dogs (P = 0.131). FMD showed an inverse correlation with left ventricular end-diastolic diameter normalized for body weight (r = ?0.76, P = 0.0043).ConclusionsBrachial FMD in dogs with early CVD inversely correlates with severity of left ventricular remodelling. 相似文献
992.
993.
994.
995.
996.
Two separate trials during 2007 and 2008 were conducted using containerized white flowering horse chestnut trees (Aesculus hippocastanum L.) to assess the efficacy of a range of insecticides applied at three different times during a growing season against the insect pest, horse chestnut leaf miner (Cameraria ohridella Deschka and Dimic; HCLM). Insecticides were timed to coincide with the emergence of the adult moth, the target organism. A conventional synthetic insecticide (deltamethrin) used within the UK for HCLM control was included for comparison. A marked impact of insecticide type and frequency of application on HCLM severity was recorded. The effectiveness of each insecticide on mean number of HCLM mines per leaf and percent HCLM larvae/pupae mortality increased when applied at increasing frequencies, i.e. three sprays provided a higher degree of control than two sprays while two sprays provided a higher degree of control than one spray. Limited efficacy as HCLM protectant compounds was demonstrated when the insecticides pyrethrum and soap were applied, irrespective of number of applications. The synthetic insecticide deltamethrin and insect growth regulator diflubenzuron provided the greatest degree of HCLM control. In some instances two foliar sprays provided 100% HCLM control. Efficacy of remaining insecticides based on reduction of HCLM mines per leaf after three sprays averaged across both the 2007 and 2008 trials was in the order silicon dioxide > alginate/polysaccharide combination > organic plant extract > spray oil. Results show commercially registered insecticides exist that provide growing season control of HCLM provided two sprays are applied. 相似文献
997.
The presence of excessive amounts of heavy metals such as arsenic in the environment is a problem in many parts of the world. Many countries e.g., Bangladesh are already severely affected by arsenic contamination of soil and groundwater. Phytoaccumulation is a method in which plants are used to uptake heavy metals from soil. The genus Brassica has many species that can efficiently accumulate arsenic. Despite many studies on phytoaccumulation, little is known about the genetics of phytoaccumulation of Brassica. This study investigated the genetic effect on phytoaccumulation of arsenic in Brassica juncea L. and attempted to identify any morphological trait(s) for phytoaccumulation. Two cultivars of B. juncea namely, B. juncea cv. Rai and B. juncea cv. BARI-11 were chosen as parents for the study. A set of their morphological characteristics were selected to evaluate their potential as marker(s) for phytoaccumulation. A single concentration, 15 ppm of arsenic was used to study the genetic effect on phytoaccumulation using quantitative genetics. The results revealed that phytoaccumulation of arsenic (by the root and shoot systems) is heritable in the broad sense and polygenic in nature. The stem diameter was also found to be heritable in the broad sense and path analysis indicated that it has a significant direct effect on the shoot uptake. It is concluded that phytoaccumulation of arsenic in B. juncea (cvs. Rai and BARI-11) is a genetic phenomenon and stem diameter may be a potential marker of phytoaccumulation of arsenic in B. juncea (cvs. Rai and BARI-11). 相似文献
998.
Eric B. Taylor Rachel Chudnow Ray Pillipow Ian Spendlow Brett van Poorten 《Fisheries Management and Ecology》2021,28(3):219-229
A mixed-stock fishery occurs when multiple populations of a fish species are exploited together in a common area where they aggregate outside the breeding season (e.g. for feeding or overwintering), and the aggregation is known as a mixture. Recreational fishing often exploits such mixtures, and estimating the proportional contributions of populations to fisheries promotes more sustainable resource use. Ten DNA microsatellites were assayed in a mixture of bull trout Salvelinus confluentus Suckley overwintering in the Nechako River, upper Fraser River, British Columbia, and in baseline population samples from 14 tributaries putatively contributing to the overwintering mixture. A DNA microsatellite-based mixed-stock fishery analysis suggested that five populations together contributed 0.80 to the mixture. Most of the errors associated with the mixture estimates were attributable to uncertainty in baseline allele frequencies. Radiotracking data confirmed that tributary populations contributing to the mixture estimated by genetic analysis also contained individuals that moved between spawning tributaries and overwintering sites. The results better resolve habitat use by potadromous bull trout in the upper Fraser River and, in combination with assessments of baseline population-specific spawning abundances and productivity, will better inform a decision of whether or not allowing some harvest within the current catch-and-release fishery is biologically sustainable. 相似文献
999.
Dicen Gerald P. Navarrete Ian A. Rallos Roland V. Salmo Severino G. Garcia Maria Carmela A. 《Journal of Soils and Sediments》2019,19(1):501-510
Journal of Soils and Sediments - Despite occupying only 0.5% of the global coastal ocean, mangroves play a disproportionately large role in the capture and retention of atmospheric carbon dioxide... 相似文献
1000.
Genetic structure of Irish freshwater pearl mussels (Margaritifera margaritifera and Margaritifera durrovensis): Validity of subspecies,roles of host fish,and conservation implications
下载免费PDF全文
![点击此处可从《水产资源保护:海洋与淡水生态系统》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Juergen Geist Evelyn Moorkens Ian Killeen Sarah Feind Bernhard C. Stoeckle Áine O. Connor Ralph Kuehn 《水产资源保护:海洋与淡水生态系统》2018,28(4):923-933