全文获取类型
收费全文 | 391篇 |
免费 | 47篇 |
国内免费 | 1篇 |
专业分类
林业 | 19篇 |
农学 | 10篇 |
基础科学 | 2篇 |
79篇 | |
综合类 | 50篇 |
农作物 | 14篇 |
水产渔业 | 22篇 |
畜牧兽医 | 213篇 |
园艺 | 4篇 |
植物保护 | 26篇 |
出版年
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 15篇 |
2016年 | 17篇 |
2015年 | 18篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 22篇 |
2009年 | 17篇 |
2008年 | 23篇 |
2007年 | 23篇 |
2006年 | 19篇 |
2005年 | 14篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 15篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1958年 | 1篇 |
1945年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有439条查询结果,搜索用时 46 毫秒
51.
Climate and vegetation history of the midcontinent from 75 to 25 ka: A speleothem record from crevice cave, missouri, USA 总被引:3,自引:0,他引:3
Four Missouri stalagmites yield consistent overlapping records of oxygen and carbon isotopic changes and provide a climate and vegetation history with submillennial resolution from 75 to 25 thousand years ago (ka). The thorium-230-dated records reveal that between 75 and 55 ka, the midcontinental climate oscillated on millennial time scales between cold and warm, and vegetation alternated among forest, savanna, and prairie. Temperatures were highest and prairie vegetation peaked between 59 and 55 ka. Climate cooled and forest replaced grassland at 55 ka, when global ice sheets began to build during the early part of Marine Oxygen Isotope Stage 3. 相似文献
52.
M V Jaraiz C Rodriguez M D San Andres F Gonzalez M I San Andres 《Equine veterinary journal》1999,31(5):411-416
Suxibuzone (SBZ), a nonsteroidal anti-inflammatory drug, was administered to 6 horses at a dose rate of 7.5 mg/kg bwt by intravenous (i.v.) route. Plasma and synovial fluid concentrations of suxibuzone and its main active metabolites, phenylbutazone (PBZ) and oxyphenbutazone (OPBZ), were measured simultaneously by a sensitive and specific high-performance liquid chromatographic method. The pharmacokinetic parameters were determined by noncompartmental analysis. Plasma SBZ concentrations rapidly decreased and were not detectable beyond 20 min after treatment. The parent drug was not detected in any synovial fluid samples. Average maximum plasma concentrations of PBZ (16.43 microg/ml) and OPBZ (2.37 microg/ml) were attained at 0.76 and 7.17 h, respectively. The mean residence time (MRT) of PBZ was 6.96 h in plasma. Oxyphenbutazone plasma concentrations were below those reached by phenylbutazone during the first 12 h after suxibuzone administration, even though its values were detectable for at least 24 h (MRT = 10.65 h). Plasma concentrations of PBZ and OPBZ exceeding EC50 and IC50 of TXB2 and PGE2 were reached by at least 12 h. Synovial fluid concentrations of PBZ and OPBZ were 2.87+/-0.37 microg/ml and 0.97+/-0.08 microg/ml at 9 h after suxibuzone administration and exceeded IC50 of PGE2 for at least this time. In the present study, suxibuzone was well tolerated following i.v. injection. 相似文献
53.
不同碳氮有机物料对有机菜田土壤细菌多样性的影响 总被引:1,自引:1,他引:0
通过模拟试验,利用聚合酶链式反应-变性梯度凝胶电泳法(PCR-DGGE),研究了施入不同碳氮有机物料(秸秆、苜蓿、有机肥、尿素)56d后,有机生产系统菜田土壤细菌群落结构的特征。结果表明,常规和有机生产系统土壤的细菌群落结构有明显差异。由DGGE图谱ShannonWiener多样性指数分析得知,有机背景处理的细菌多样性整体高于常规背景处理,且有机生产系统土壤加秸秆处理(OS)多样性最高,加入尿素后细菌多样性降低,相反,加入苜蓿后细菌多样性升高。非加权组平均法(UPGMA)聚类分析将常规和有机背景土壤分为两大族群。DGGE条带测序和系统进化树表明,30个条带归属为Proteobacteria、Acidobacteria、Actinobacteria、Firmicutes、Verrucomicrobia。常规土壤加苜蓿(CA)处理出现的特征性条带B13与有机背景处理的共有条带B28分别与Bacillus属和Pseudomonas假单胞菌属同源性最高。 相似文献
54.
55.
Spread of the yellow‐legged hornet Vespa velutina nigrithorax du Buysson (Hymenoptera: Vespidae) across Northern Spain 下载免费PDF全文
A. Goldarazena I. P. de Heredia P. Romon J. C. Iturrondobeitia M. Gonzalez S. Lopez 《EPPO Bulletin》2015,45(1):133-138
The yellow‐legged hornet Vespa velutina nigrithorax du Buysson (Hymenoptera: Vespidae) is an Asian native species which has now established in parts of Europe. Since its detection in France in 2005 it has spread quickly across the country and also spread to the Iberian Peninsula. This paper compiles the most recent data about its spread and distribution on the Spanish mainland. The efficacy of using Véto‐Pharma© traps as a control method is also discussed. 相似文献
56.
Mansoor Sarani Mostafa Oveisi Hamid Rahimian Mashhadi Hassan Alizade Jose Luise Gonzalez‐Andujar 《Weed Biology and Management》2014,14(3):198-208
Field experiments were conducted in Iran in order to determine the interactions between the tillage system and crop rotation on weed seedling populations and crop yields from 2002 to 2005. No tillage, shallow tillage and deep tillage were the main plots and three crop sequences comprising continuous wheat (W‐W), wheat–canola–wheat–canola (C‐W) and wheat–safflower–wheat–safflower (S‐W) were the subplots. Bromus japonicus, Carthumus lanatus, Polygonum aviculare, Lolium temulentum and Avena ludoviciana were found to be the dominant species. The initial weed population in 2002 was estimated at 65 seedlings per m2 and B. japonicus (~35 seedlings per m2) was the most abundant species, followed by A. ludoviciana and L. temulentum. The dominant weed species mostly did not favor the combination of S‐W and C‐W with any tillage type. For the B. japonicus population, S‐W in combination with moldboard plowing indicated the lowest seedling population. In conclusion, the crop sequence in combination with tillage would help to control troublesome weed species. Safflower and canola were determined to be effective in reducing the grass weeds. The inclusion of these crops in rotation also increased the total revenue of the cropping systems because of the higher sale price of canola and safflower. 相似文献
57.
This study compared the efficiency of the aromatase inhibitor, anastrazole, with the antioestrogenic receptor blocker, tamoxifen, on normal (NRL) and hyperplastic prostate glands. Forty healthy dogs were classified as NRL (n = 18) or abnormal (ABN) with benign prostate hyperplasia (n = 22). The dogs were randomly assigned to one of the following six groups, treated for 60 days; oral placebo for normal (NRL-PLC; n = 6) and abnormal (ABN-PLC; n = 6), oral anastrazole 0.25–1 mg/day, for normal (NRL-ANZ, n = 6) and abnormal (ABN-ANZ, n = 8) and oral tamoxifen citrate 2.5–10 mg/day for normal (NRL-TMX; n = 6) and abnormal (ABN-TMX; n = 8) dogs. The dogs were evaluated before treatment and then monthly for 4 months. At the end of the treatment, the prostatic volume decreased by 28.5 ± 4.3%, 21.6 ± 6.3% and 0.7 ± 1.0% in the ABN-TMX, ABN-ANZ and ABN-PLC (p < 0.01), respectively. From then on, prostatic volume began to increase without reaching pre-treatment values at the end of the study. In the ABN animals, there were no differences for this parameter between ANZ and TMX treatment (p > 0.1), whereas in the NRL animals ANZ produced a less pronounced decrease (p < 0.05), libido, testicular consistency and scrotal diameter decreased during treatment in the TMX group (p > 0.05). These parameters and sperm volume, count, motility and morphological abnormalities remained unaltered throughout the study in the ANZ and PLC groups (p > 0.05). There were no haematological nor biochemical side effects. Anastrazole might offer a safe and effective alternative for the medical management of dogs with benign prostatic hyperplasia. 相似文献
58.
Goldman CG Loureiro JD Matteo MJ Catalano M Gonzalez AB Heredia SR Zubillaga MB Solnick JV Cremaschi GA 《Research in veterinary science》2009,86(1):18-21
Gastrointestinal lesions with uncertain etiology have been widely described among pinnipeds. The aim of our study was to investigate the presence of Helicobacter spp. in the gastric mucosa of South American fur seals (Arctocephalusaustralis). Gastric biopsies from thirteen seals, stranded on the shores of the Southwestern Atlantic Ocean in Argentina, were evaluated for the presence of Helicobacter spp. by PCR and DNA sequence analysis. Six gastric biopsies were positive for Helicobacter spp. Pairwise sequence comparisons showed less than 95% identity to novel Helicobacter spp. described from pinnipeds from North America and Australia. However, phylogenetic analysis revealed that the South American fur seal sequences clustered with 99-100% homology with H. cetorum, a species isolated from dolphins and whales. The presence of H. cetorum in pinnipeds, if confirmed by its isolation from the gastric mucosa of these mammals, demonstrates the wide host range of this bacterium in the marine environment. 相似文献
59.
60.
Sven Günter Paul Gonzalez Guido Álvarez Nikolay Aguirre Ximena Palomeque Frank Haubrich Michael Weber 《Forest Ecology and Management》2009
The Andes of Ecuador are known for their outstanding biodiversity but also as the region with the highest deforestation rate in South America. This process is accompanied by accelerating degradation and loss of environmental services. Despite an extraordinary richness in native tree diversity, more than 90% of all forest plantations established in Ecuador consist of exotic species, primarily Eucalyptus spp. and Pinus spp. This is mainly due to the lack of information about the autecological and synecological requirements of the native species. 相似文献