全文获取类型
收费全文 | 615篇 |
免费 | 24篇 |
专业分类
林业 | 16篇 |
农学 | 8篇 |
61篇 | |
综合类 | 94篇 |
农作物 | 56篇 |
水产渔业 | 18篇 |
畜牧兽医 | 333篇 |
园艺 | 18篇 |
植物保护 | 35篇 |
出版年
2020年 | 4篇 |
2019年 | 14篇 |
2018年 | 10篇 |
2016年 | 5篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 35篇 |
2012年 | 25篇 |
2011年 | 26篇 |
2010年 | 20篇 |
2009年 | 24篇 |
2008年 | 22篇 |
2007年 | 22篇 |
2006年 | 16篇 |
2005年 | 27篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 19篇 |
1999年 | 13篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 10篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 13篇 |
1990年 | 23篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 9篇 |
1971年 | 4篇 |
1970年 | 6篇 |
1967年 | 7篇 |
1955年 | 4篇 |
排序方式: 共有639条查询结果,搜索用时 15 毫秒
41.
Plant circadian clocks increase photosynthesis, growth, survival, and competitive advantage 总被引:3,自引:0,他引:3
Dodd AN Salathia N Hall A Kévei E Tóth R Nagy F Hibberd JM Millar AJ Webb AA 《Science (New York, N.Y.)》2005,309(5734):630-633
Circadian clocks are believed to confer an advantage to plants, but the nature of that advantage has been unknown. We show that a substantial photosynthetic advantage is conferred by correct matching of the circadian clock period with that of the external light-dark cycle. In wild type and in long- and short-circadian period mutants of Arabidopsis thaliana, plants with a clock period matched to the environment contain more chlorophyll, fix more carbon, grow faster, and survive better than plants with circadian periods differing from their environment. This explains why plants gain advantage from circadian control. 相似文献
42.
43.
44.
45.
The feasibility of autologous intrarenal mesenchymal stem cell (MSC) therapy in cats with chronic kidney disease (CKD) was investigated. Six cats (two healthy, four with CKD) received a single unilateral intrarenal injection of autologous bone marrow-derived or adipose tissue-derived MSC (bmMSC or aMSC) via ultrasound guidance. Minimum database and glomerular filtration rate (GFR) via nuclear scintigraphy were determined pre-injection, at 7 days and at 30 days post-injection. Intrarenal injection did not induce immediate or long-term adverse effects. Two cats with CKD that received aMSC experienced modest improvement in GFR and a mild decrease in serum creatinine concentration. Despite the possible benefits of intrarenal MSC injections for CKD cats, the number of sedations and interventions required to implement this approach would likely preclude widespread clinical application. We concluded that MSC could be transferred safely by ultrasound-guided intrarenal injection in cats, but that alternative sources and routes of MSC therapy should be investigated. 相似文献
46.
47.
There are concerns over a range of adverse environmental effects resulting from the storage of livestock manures on farms. The objectives of this study were to examine all the likely environmental effects of different storage methods, and to recommend which were the most desirable options.Literature reviews were undertaken to identify the likely environmental consequences of each commonly used storage method, in terms of water pollution risks, odour and ammonia emissions, greenhouse gas emissions and survival of microorganisms during storage. Planning and landscape aspects were considered and the most feasible options for abatement of ammonia emissions were identified. An ‘environmental rating’ for different storage systems was then devised, with the aim of obtaining a balance between water pollution, aerial emissions and other concerns.The environmental rating exercise favoured the more sophisticated and hence most expensive storage methods. No large differences emerged between ratings for slurry systems and solid systems when ease of adding ammonia control measures was excluded. For pigs, slurry systems appear to have a slight advantage, because of the greater ammonia emissions from the solid pig manure. The use of such a rating system could be developed further as more data become available. Whilst the method indicates the relative desirability of systems at a national scale it could be adapted to take account of local considerations or those of individual farm sites. 相似文献
48.
A method is described for determining the artificial sweetener aspartame in beverages and beverage mixes by liquid chromatography. Aspartame is separated on a microC18 column, using a mobile phase of acetic acid, water, and isopropyl alcohol at pH 3.0 and UV detection at 254 nm. Beverages are filtered through 0.45 micron filters and injected directly into the chromatograph. Aspartame is eluted in approximately 7 min. Detection of aspartame is confirmed by a UV scan of the trapped peak. Aspartame is quantitated in the presence of other beverage additives such as saccharin, caffeine, sodium benzoate, artificial colors, and artificial flavors. Results are presented for spiked soda beverages, beverages from fruit-flavored mixes, instant tea, reconstituted presweetened drink mixes, and a powdered tabletop sweetener. 相似文献
49.
Johannes Vernooij Florine de Munck Evelien van Nieuwenhuizen Edward Webb Herman Jonker Peter Vos Dietmar Holm 《Reproduction in domestic animals》2020,55(11):1592-1598
Pelvis size plays an important role to prevent dystocia in cattle caused by the foeto-maternal disproportion in commonly primiparous females. The reproducibility and repeatability are two important aspects for the reliability of the measurements to use in the selection of cattle for culling. Pelvic measures were taken with a Rice pelvimeter from 224 young cattle (180 females and 44 males) of four beef breeds in South Africa. One experienced and two inexperienced observers each measured pelvic height and width twice. The proportion measurements with a maximum difference of 0.5 cm within animal compared with the first measurement by the experienced observer are around 80% and by the inexperienced observers around 50% for pelvic height and around 60% for pelvic width. Breed and sex do not affect the reliability of pelvimetry by an experienced observer. Under- and overestimation of pelvis size were observed in inexperienced observers, which seems to be unrelated to breed and sex. 相似文献
50.
Dr Stephen Collier Dr Bob Bradley Faith Rosson Will Gartrell Dr Bob Bradley Alistair Webb Dr Graham Thompson Dr Elaine Cebuliak 《Australian veterinary journal》2001,79(5):320-322
Editor's note: The AVJ welcomes letters from members in all areas of the profession on matters of importance to you. Please keep them brief ‐ to meet our space constraints. Letters will be subject to minimal editing procedures. Subject to letters complying with the AVJ's legal responsibilities, they will not be censored. Nor will individuals or groups waging'‘campaigns’ be permitted to abuse these pages. If submitting a letter intended for publication, kindly identify it as such. Letters to the Editor can be sent by mail, fax or e‐mail at the contact points listed at the start of the News Section. Writers may use a pseudonym to protect their identities ‐ but must supply the Editor with verifiable names and points of contact. 相似文献