全文获取类型
收费全文 | 114篇 |
免费 | 4篇 |
专业分类
林业 | 6篇 |
农学 | 8篇 |
6篇 | |
综合类 | 33篇 |
农作物 | 8篇 |
水产渔业 | 13篇 |
畜牧兽医 | 25篇 |
园艺 | 5篇 |
植物保护 | 14篇 |
出版年
2023年 | 1篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 5篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 9篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1965年 | 2篇 |
1959年 | 1篇 |
1952年 | 2篇 |
1892年 | 1篇 |
排序方式: 共有118条查询结果,搜索用时 0 毫秒
41.
42.
43.
From early times, jute fibre has been generally conditioned for easy spinning by adding oil and water in the form of an emulsion. The commonly used oil consists of C12–C31 fractions of mineral oil that sometimes impart different intensities of oily (kerosene) or fishy smell to the end product. In the present work, efforts have been made to find a suitable sustainable substitute of mineral oil based conditioning agent for spinning of jute yarn and for this, three types of vegetable oil (rice bran oil, palmolein oil and castor oil), a silicone emulsion, a mixed enzyme system and glycerine have been used separately or in combinations as conditioning agents for jute fibre before its mechanical processing for making yarn in jute spinning machines. Considering comparable mechanical process performance for spinning of jute fibre (viz., fibre loss as droppings during processing, moisture retention prior to spinning stage and spinning end breakage rate), tensile properties of yarn, and lower yarn hairiness, it may be suggested to use 2.5% castor oil alone, or 2% castor oil in combination with 0.1–0.5% glycerine in the form of oil-in-water emulsion as the most suitable alternatives to conventional mineral oil-based jute conditioning agent to spin ordinary jute yarn. 相似文献
44.
Coconut fibres were subjected to chemical treatment to obtain softer and finer fibres, suitable to blend with other finer fibre like jute. The chemical softening recipe was optimized using Box-Behnken design of experiments as 40 % Na2S, 10 % NaOH and 6 % Na2CO3, which notably reduced the fineness (33 %) and flexural rigidity (74 %) and improved tensile property of coconut fibre. Effect of softening of coconut fibre on its process performance was studied in high speed mechanized spinning system at different blend ratios with jute. Blending with jute assists in spinning of coconut fibre to produce yarn of 520 tex at production rate of 5-6 kg/h, as compared to 15 kg/day for hand spun 5300 tex raw coconut fibre yarn in manual system. Analysis of blended yarn structure in terms of packing density, radial distribution of fiber components (SEM) and mass irregularity were investigated. SEM shows yarns made from softened coconut fibre -jute blends are more compact than raw coconut fibre -jute blend yarns. Coconut fibres were preferentially migrated to core of the yarn. Major yarn properties viz., tensile strength, and flexural rigidity of raw and chemically softened blended yarns were compared against their finest possible 100 % coconut fibre yarn properties. Yarn made up to 50:50 chemically softened coconut fibre-jute blend showed much better spinning performance, and having superior property in terms of reduced diameter, higher compactness, strength, initial modulus and less flexural rigidity than 100 % raw, 100 % chemically softened coconut fibre rope, and raw coconut fibre-jute blend yarns. 相似文献
45.
Aritra Bera Paramita Banerjee Sawant Subrata Dasgupta N. K. Chadha Bhawesh T. Sawant Asim Kumar Pal 《Fish physiology and biochemistry》2017,43(6):1677-1688
Diel cyclic hypoxia occurs with varying frequency and duration in freshwater habitats, yet little is known about its effects on reproduction of freshwater fishes. The present study shows that long-term exposure of goldfish (Carassius auratus) to cyclic hypoxia (0.8 ± 0.2 mg/l dissolved oxygen) for 9 h or more, per day, altered plasma lipid and sex steroid profiles, which in turn directly or indirectly suppressed ovarian growth and viable spermatozoa production. Hypoxia decreased total cholesterol and high density lipoprotein (HDL p < 0.05) and elevated triglycerides (TG; p < 0.05) in both sexes. Plasma steroid concentrations particularly of 17α-hydroxyprogesterone (17-HP), estradiol (E2), testosterone (T) in females, and T and 11-ketotestosterone (11-KT) in males were attenuated under diel hypoxic conditions. Intriguingly, both diel and continuous hypoxia elevated plasma E2 and vitellogenin levels in males. However, neither lipid nor steroid profiles recorded any variation in a dose-dependent manner in response to diel hypoxia. The reduced GSI, decreased number of tertiary oocytes, and motile spermatozoa in hypoxic fish clearly indicate suppression of gametogenesis. Thereby, prolonged diel cyclic hypoxia may affect valuable fishery resources and fish population structure by impairing reproductive performances and inducing estrogenic effects in males. 相似文献
46.
Rathee JS Patro BS Mula S Gamre S Chattopadhyay S 《Journal of agricultural and food chemistry》2006,54(24):9046-9054
The 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay of the ethanol extracts of three varieties (Bangla, sweet, and Mysore) of Piper betel (pan) revealed the Bangla variety to possess the best antioxidant activity that can be correlated with the total phenolic content and reducing powers of the respective extracts. Column chromatography of the extract of the Bangla variety led to the isolation of chevibetol (CHV), allylpyrocatechol (APC), and their respective glucosides. The HPTLC analyses of the extracts revealed similar chemical profiles in all three P. betel varieties, although the concentrations of CHV and APC were significantly less in the sweet and Mysore varieties. Among the isolated compounds, APC showed the best results in all the in vitro experiments. It could prevent Fe(II)-induced lipid peroxidation (LPO) of liposomes and rat brain homogenates as well as gamma-ray-induced damage of pBR322 plasmid DNA more efficiently than CHV. The superior anti-LPO and radioprotective activities of APC vis-à-vis those of CHV could not be explained by their respective Fe(II) chelation and .OH radical scavenging capacities. The better ability of APC to scavenge O2-. radicals and H2O2 might account for the results. 相似文献
47.
Chinmay Biswas Piyali Dey Subrata Satpathy Pratik Satya B. S. Mahapatra 《Phytoparasitica》2013,41(1):17-21
Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales), an entomopathogenic fungus, was introduced through seed inoculation with spore suspension as an endophyte in white jute (Corchorus capsularis L.), a bast fiber crop. Out of nine B. bassiana strains, seven, viz., ITCC 6063, ITCC 4512, ITCC 4563, ITCC 5562, ITCC 4796, ITCC 5408 and ITCC 4705, became established as endophytes. The endophytic colonization was initially detected by cultivation on selective medium. Colonization was confirmed by polymerase chain reaction (PCR) using sequence characterized amplified region (SCAR) marker. Endophytic B. bassiana strains colonized in leaves of all the plants grown from treated seeds. However, the colonization frequency varied among the strains. The highest colonization frequency (70.09%) was recorded in ITCC 6063 followed by ITCC 5562 (67.67%) and ITCC 5408 (64.17%); ITCC 4512 exhibited the lowest (42.54%) colonization. ITCC 4925 and ITCC 4644 did not show any colonization. Endophytic colonization of B. bassiana reduced stem weevil infestation under pot culture. ITCC 5408 and ITCC 6063 were found most efficient, with only 10.44% and 14.06% infested plants, respectively. 相似文献
48.
49.
A detailed study of electromagnetic shielding effectiveness (EMSE) of woven fabrics made of polyester and stainless steel/polyester blended conductive yarn was presented in this research work. Fabrics with different structures were analyzed and their shielding behavior was reported under different frequencies. Shielding efficiency of fabric was analyzed by vector network analyzer in the frequency range of 300 kHz to 1.5 GHz using coaxial transmission line holder. The effects of different fabric parameters such as weft density, proportion of conductive weft yarn, proportion of stainless steel content, grid openness, weave pattern and number of fabric layers on EMSE of fabrics were studied. The EMSE of fabric was found to be increased with increase in proportion of conductive yarn in the weft way. With increase in overall stainless-steel content in the fabric, the EMSE of fabric was increased. As such weave is considered, it did not have significant effect on EMSE of fabrics. But fabric with lower openness and aperture ratio showed better conducting network, hence better shielding. With increase in number of layers of fabric and ply yarns, EMSE of fabric was increased. 相似文献
50.
Carter JA Agol E Chaplin WJ Basu S Bedding TR Buchhave LA Christensen-Dalsgaard J Deck KM Elsworth Y Fabrycky DC Ford EB Fortney JJ Hale SJ Handberg R Hekker S Holman MJ Huber D Karoff C Kawaler SD Kjeldsen H Lissauer JJ Lopez ED Lund MN Lundkvist M Metcalfe TS Miglio A Rogers LA Stello D Borucki WJ Bryson S Christiansen JL Cochran WD Geary JC Gilliland RL Haas MR Hall J Howard AW Jenkins JM Klaus T Koch DG Latham DW MacQueen PJ Sasselov D Steffen JH Twicken JD Winn JN 《Science (New York, N.Y.)》2012,337(6094):556-559
In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets' orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky "super-Earth," whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system. 相似文献