全文获取类型
收费全文 | 822篇 |
免费 | 51篇 |
国内免费 | 1篇 |
专业分类
林业 | 9篇 |
农学 | 23篇 |
基础科学 | 1篇 |
70篇 | |
综合类 | 142篇 |
农作物 | 19篇 |
水产渔业 | 34篇 |
畜牧兽医 | 516篇 |
园艺 | 19篇 |
植物保护 | 41篇 |
出版年
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 14篇 |
2017年 | 17篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 45篇 |
2012年 | 28篇 |
2011年 | 46篇 |
2010年 | 26篇 |
2009年 | 18篇 |
2008年 | 28篇 |
2007年 | 27篇 |
2006年 | 29篇 |
2005年 | 21篇 |
2004年 | 32篇 |
2003年 | 26篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 30篇 |
1999年 | 26篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 29篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 12篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1980年 | 9篇 |
1979年 | 14篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1972年 | 4篇 |
1971年 | 7篇 |
1970年 | 6篇 |
1967年 | 4篇 |
排序方式: 共有874条查询结果,搜索用时 968 毫秒
141.
Perkins-Veazie P Collins JK Davis AR Roberts W 《Journal of agricultural and food chemistry》2006,54(7):2593-2597
The lycopene content of 50 commercial cultivars of seeded and seedless red-fleshed watermelons was determined. Scanning colorimetric and spectrophotometric assays of total lycopene were used to separate watermelon cultivars into low (<50 mg/kg fw), average (50-70 mg/kg fw), high (70-90 mg/kg fw), and very high (>90 mg/kg fw). Cultivars varied greatly in lycopene content, ranging from 33 to 100 mg/kg. Most of the seeded hybrid cultivars had average lycopene contents. Sixteen of the 33 seedless types had lycopene contents in the high and very high ranges. All-trans-lycopene was the predominant carotenoid (84-97%) in all watermelon cultivars measured by high-performance liquid chromatography, but the germplasm differed in the relative amounts of cis-lycopene, beta-carotene, and phytofluene. Red-fleshed watermelon genotypes vary extensively in carotenoid content and offer opportunities for developing watermelons with specifically enhanced carotenoids. 相似文献
142.
CCL11 (also known as eotaxin) is a very potent and selective mediator of eosinophil migration which exerts its effects through its receptor, CCR3. In this study we report the cloning of an equine CCR3 cDNA sequence and investigation of the localization of CCR3 mRNA expression in horse tissues. Equine CCR3 displayed high levels of sequence identity with CCR3 sequences in other species. RT-PCR analysis revealed the expression of CCR3 in colon, lung and spleen of normal horses. In situ hybridisation experiments indicated that expression of CCR3 mRNA in colon was predominantly in eosinophils and to a lesser extent in mast cells, whereas CCR3 was seen mainly in lymphocytes of the lung and spleen. In view of the role of CCR3 in the recruitment of cells into sites of allergic inflammation, equine-specific CCR3 sequence data and information on tissue localization will be of potential benefit in the development of CCR3-targeted anti-inflammatory therapies in the horse. 相似文献
143.
Collins JD 《Veterinary microbiology》2006,112(2-4):369-381
In the later stages of eradication of tuberculosis in cattle there is a need to take account of the fact that Mycobacterium bovis infection in cattle presents, not as cases of clinical disease but most commonly as apparently healthy animals showing an immunological response to tuberculin. This is an entirely different scenario to that seen when national eradication programmes were first devised, at a time when the protection of public health rather than animal health was the prime motivation. In countries with active programmes to eradicate bovine tuberculosis, it is critical for the programme's success that account is taken of this redefinition of tuberculosis, side by side with changes in modern animal production systems and their impact on the transmission of M. bovis. This paper highlights factors critical to the success of a national eradication programme, including a clear identification of the goals, of the policies that guide actions, and of the sequences of actions that are required within the programme to accomplish these goals. Experience has illustrated the adverse effects of compromise on outcome when the application of fundamental principles of disease control such as sound animal management, removal of known sources of infection, early diagnosis, quarantine, movement control and environmental hygiene are less than enthusiastically promoted and applied. The reality is that where these principles are applied in a sustained manner, the outcome is more likely to be successful. Therein lies the challenge for the risk manager. 相似文献
144.
Plant genotypic diversity predicts community structure and governs an ecosystem process 总被引:1,自引:0,他引:1
Crutsinger GM Collins MD Fordyce JA Gompert Z Nice CC Sanders NJ 《Science (New York, N.Y.)》2006,313(5789):966-968
Theory predicts, and recent empirical studies have shown, that the diversity of plant species determines the diversity of associated herbivores and mediates ecosystem processes, such as aboveground net primary productivity (ANPP). However, an often-overlooked component of plant diversity, namely population genotypic diversity, may also have wide-ranging effects on community structure and ecosystem processes. We showed experimentally that increasing population genotypic diversity in a dominant old-field plant species, Solidago altissima, determined arthropod diversity and community structure and increased ANPP. The effects of genotypic diversity on arthropod diversity and ANPP were comparable to the effects of plant species diversity measured in other studies. 相似文献
145.
Collins GS 《Science (New York, N.Y.)》2012,335(6073):1176-1177
146.
Objective The ability of a new commercial ELISA to detect pigs with subclinical proliferative enteropathy (PE) was compared with the traditional indirect fluorescent antibody test (IFAT). Methods Serum samples were selected from pigs with known Lawsonia intracellularis infection status and clinical signs of PE, but the sample population consisted predominantly of pigs subclinically affected by PE. Results Significant association and agreement were shown between the ELISA and IFAT assays. ELISA results correlated well with the duration of L. intracellularis shedding as detected by polymerase chain reaction. Conclusion ELISA can be successfully used to monitor L. intracellularis infection in pigs. 相似文献
147.
148.
Manju V. Sharma Catherine M. Collins Simon R. Leather 《Journal of Sustainable Forestry》2013,32(6):563-575
Myristica dactyloides is characteristic of the mid- and high-elevation evergreen forests of the Western Ghats of India. Aril and seeds of the species are valuable nontimber forest products and are harvested extensively. We made visual estimates of fruit crop size in nine populations. We assessed disturbance using five variables: distance from road, method of harvesting fruits, nonforest matrix around the population, seedling regeneration, and protected area status. Unsustainable harvest and proximity to road impacted fruit crop, as did the nonforest matrix (F = 38.17 df = 5,102, p < .001). While high protection and measures against harvesting keep some populations safe, the harvest method plays a crucial role in determining total fruit production and seedling recruitment in the species. 相似文献
149.
Graeme J. Eamens Jocelyn R. Gonsalves Cheryl Jenkins Damian Collins Graham Bailey 《Veterinary parasitology》2013,191(3-4):209-217
Between September 2010 and November 2011, 350 EDTA blood samples were received from 73 Australian cattle herds, as cases suspected to be infected with Theileria orientalis. Beef cattle were predominantly affected, with Angus and Angus-crossbred cattle representing 48% of smear positive samples examined. DNA extracts were tested in conventional polymerase chain reaction (PCR) assays for genes encoding the p32, Ikeda, Chitose and Buffeli major piroplasm surface proteins (MPSP). PCR findings were compared with results of clinical pathology examinations of stained blood smears for parasitaemia and packed cell volume (PCV). PCR testing was much more sensitive than clinical pathology examinations in detecting T. orientalis infections, and concurrent testing of neat and diluted extracts gave significantly more PCR positive results than testing of neat extract alone. Significant associations and correlations were shown between PCR results of p32 and Ikeda assays with PCV levels indicative of anaemia, and with the level of parasitaemia estimated by smears. A high proportion of samples had concurrent Ikeda and Chitose infection, and significantly more clinical cases of theileriosis were associated with the Ikeda MPSP type as the sole infection, compared with sole infection with types Chitose or Buffeli. The findings indicate Ikeda type organisms were significantly associated with clinical parameters of theileriosis in cattle herds in eastern Australia, and that this type is most likely to be responsible for outbreaks of theileriosis experienced in affected Australian herds. In New South Wales, 11 of 14 regulatory districts yielded Ikeda positive samples, with five (Mid-Coast, Cumberland, Central North, Hume and Lachlan) containing 234/307 (76%) of the Ikeda positive samples. 相似文献
150.