全文获取类型
收费全文 | 1115篇 |
免费 | 100篇 |
国内免费 | 1篇 |
专业分类
林业 | 49篇 |
农学 | 38篇 |
基础科学 | 10篇 |
153篇 | |
综合类 | 122篇 |
农作物 | 69篇 |
水产渔业 | 55篇 |
畜牧兽医 | 659篇 |
园艺 | 30篇 |
植物保护 | 31篇 |
出版年
2023年 | 14篇 |
2022年 | 14篇 |
2021年 | 38篇 |
2020年 | 40篇 |
2019年 | 32篇 |
2018年 | 37篇 |
2017年 | 36篇 |
2016年 | 33篇 |
2015年 | 28篇 |
2014年 | 37篇 |
2013年 | 53篇 |
2012年 | 87篇 |
2011年 | 79篇 |
2010年 | 48篇 |
2009年 | 44篇 |
2008年 | 78篇 |
2007年 | 67篇 |
2006年 | 62篇 |
2005年 | 48篇 |
2004年 | 39篇 |
2003年 | 33篇 |
2002年 | 34篇 |
2001年 | 12篇 |
2000年 | 21篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1971年 | 3篇 |
1970年 | 8篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1966年 | 4篇 |
1963年 | 4篇 |
排序方式: 共有1216条查询结果,搜索用时 15 毫秒
81.
影响烟草特有亚硝胺积累的因素 总被引:1,自引:0,他引:1
把Nicotiana plumbaginifolia的基因突变种子和普通种子发芽后嫁接在Wesconsin38烟株上,与温室条件下正常盆栽生长的Nicotiana plumbaginifolia和母体Wesconsin38分析比较,试验结果得出:Wesconsin38上嫁接Nicotiana plumbaginifolia基因突变种子还原酶活性最高,晾制后烟叶中烟草特有的亚硝胺含量次之;温室盆栽的 相似文献
82.
83.
Julia Griffin 2011年10月在互联网发表的论文"Ensuring Certified Supply"报道了零售商B&Q公司(百安居)实现了所售木材商品全部来自可持续来源,同时也指出了,木材供应可持续发展面临着难题和挑战仍有很长的路要走。 相似文献
84.
A new copepod species, Acanthochondria sagitta sp. n., is described based on specimens collected from the flounder Xystreurys rasile (Jordan) (Pleuronectiformes, Paralichthyidae), caught in the coastal waters off Necochea, Buenos Aires Province, Argentina. The new species differs from its congeners by the following combination of characters: presence of three pairs of cephalic outgrowths; the triangular shape of the trunk with diverging postero-lateral processes; leg 2 of an intermediate shape between Types C and D, which projects laterally from the trunk, and Type B-V antennule bearing two proximal processes (one ventral and one dorsal) on the swollen basal portion. 相似文献
85.
The upper critical concentration for Cd in wheat plants (Triticum aestivum) grown in Hoagland's solution, was found by the method of Beckett and Davis (1977) to be 44 μg g?1 dry weight, using shoot chlorophyll levels as an indicator of plant health. Chlorophyll compared favorably with other indices of growth and may, in conditions where metal toxicity is manifest as chlorosis, be more accurate and sensitive than shoot dry weights or longest root lengths. It was not possible with the limited number of experiments conducted here to determine, with any degree of confidence, differences in the levels at which chlorophylls a and b were affected. 相似文献
86.
The fungicide Vitavax RS and the seed polymer Extender were sequentially applied to canola seed to determine their effect on the fungal inoculum, Penicillium bilaiae. In the laboratory, the fungicide was applied at the recommended rate of 23.4 ml kg–1, and the polymer was applied by the manufacturer. Significant death of P. bilaiae occurred after 2.5 days on the Vitavax RS-treated seed and after 1.5 days with the seed treated with both Vitavax RS and Extender. In field treatments, the seed was sown at six sites in the fall just prior to freeze-up. Results from the laboratory experiment indicate that there should be no harmful effects of the Vitavax RS and Extender on the P. bilaiae at the time of seeding because the seeds were sown within 2 h of inoculation. The environmental extremes in 2001 and 2002 resulted in large variations in the data. P. bilaiae did not increase yield under these conditions. 相似文献
87.
Differences in weed population dynamics with respect to within-field heterogeneity are not well documented despite increasing interest in site-specific management of agro-ecosystems. The focus of this study was to determine if mechanical weed management (cultivation) and/or soil factors help to explain observed within-field distributions of feral common sunflower (Helianthus annuus L.). The ridges and furrows created by the ridge–tillage system adds additional microsites to existing spatial heterogeneity for soil characteristics such as soil organic carbon (SOC) concentration. Experimental areas were selected on the basis of naturally high or low SOC concentration. Cultivation resulted in 100% mortality of H. annuus seedlings growing in the middle of furrows. Cultivation of pre-emergence herbicide treated and no-herbicide ridges resulted in small but statistically significant ( = 0.05) reductions in seedling survival. No differences were detected in H. annuus canopy height, stem diameter, stem length, or vegetative biomass between high and low SOC environments. Neither total reproductive biomass (P = 0.49) nor the biomass of flowers near physiological maturity (an estimate of fecundity; P = 0.59) were affected by SOC environment. Late season H. annuus lodging was observed to reduce reproductive biomass. Juvenile plants that survived mechanical weed control efforts grew and produced reproductive biomass similarly across SOC environments. The lack of difference in vegetative and reproductive characteristics between high and low SOC environments suggests that SOC (or the edaphic conditions associated with greater or lesser SOC level) was not critical in contributing to the observed distribution of H. annuus from juvenile to flowering stages of growth within well-fertilized, irrigated agricultural habitats. 相似文献
88.
89.
90.
Extensive large colon resection in the pony. II. Digestibility studies and postmortem findings. 总被引:1,自引:0,他引:1 下载免费PDF全文
N G Ducharme J H Burton A A van Dreumel F D Horney J D Baird M Arighi 《Canadian journal of veterinary research》1987,51(1):76-82
The nutritional implications and adaptive processes resulting from resection of 75% of the length of the large colon in ponies were investigated. Ten ponies in good physical condition were divided into two groups: six in the experimental group and four in the control group. During the sixth postoperative month, two digestibility studies were conducted, and phosphate fractional renal excretion and serum biochemical profiles were determined in both groups. The ponies (N = 10) were euthanized six months postoperatively, and gross and histopathological examinations were performed. Results of the serum biochemical profiles, phosphate fractional renal extraction and digestibility studies showed no statistically significant difference between groups except for the serum phosphate concentration. However, large colon resection was associated with hypophosphatemia in three of the six ponies and produced an overall significantly lower phosphate concentration in the experimental ponies. This hypophosphatemia suggests that some dietary modifications may be needed postoperatively in ponies or horses undergoing this surgical procedure. Postmortem examination and histopathological examination failed to demonstrate differences between groups. Adaptive mechanisms, specifically mucosal hypertrophy or hyperplasia, were not observed. 相似文献