全文获取类型
收费全文 | 208篇 |
免费 | 16篇 |
专业分类
林业 | 32篇 |
农学 | 32篇 |
5篇 | |
综合类 | 19篇 |
农作物 | 15篇 |
水产渔业 | 10篇 |
畜牧兽医 | 100篇 |
园艺 | 3篇 |
植物保护 | 8篇 |
出版年
2022年 | 3篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2017年 | 3篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1985年 | 5篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 3篇 |
1975年 | 2篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1967年 | 2篇 |
1958年 | 3篇 |
1947年 | 3篇 |
1946年 | 2篇 |
1945年 | 2篇 |
1944年 | 3篇 |
1943年 | 5篇 |
1942年 | 9篇 |
1941年 | 2篇 |
1940年 | 3篇 |
1939年 | 5篇 |
1938年 | 8篇 |
1937年 | 2篇 |
1926年 | 3篇 |
排序方式: 共有224条查询结果,搜索用时 11 毫秒
61.
62.
63.
64.
65.
De Pontieu B McIntosh SW Carlsson M Hansteen VH Tarbell TD Schrijver CJ Title AM Shine RA Tsuneta S Katsukawa Y Ichimoto K Suematsu Y Shimizu T Nagata S 《Science (New York, N.Y.)》2007,318(5856):1574-1577
Alfvén waves have been invoked as a possible mechanism for the heating of the Sun's outer atmosphere, or corona, to millions of degrees and for the acceleration of the solar wind to hundreds of kilometers per second. However, Alfvén waves of sufficient strength have not been unambiguously observed in the solar atmosphere. We used images of high temporal and spatial resolution obtained with the Solar Optical Telescope onboard the Japanese Hinode satellite to reveal that the chromosphere, the region sandwiched between the solar surface and the corona, is permeated by Alfvén waves with strong amplitudes on the order of 10 to 25 kilometers per second and periods of 100 to 500 seconds. Estimates of the energy flux carried by these waves and comparisons with advanced radiative magnetohydrodynamic simulations indicate that such Alfvén waves are energetic enough to accelerate the solar wind and possibly to heat the quiet corona. 相似文献
66.
Peptide neurotoxins from fish-hunting cone snails 总被引:39,自引:0,他引:39
B M Olivera W R Gray R Zeikus J M McIntosh J Varga J Rivier V de Santos L J Cruz 《Science (New York, N.Y.)》1985,230(4732):1338-1343
To paralyze their more agile prey, the venomous fish-hunting cone snails (Conus) have developed a potent biochemical strategy. They produce several classes of toxic peptides (conotoxins) that attack a series of successive physiological targets in the neuromuscular system of the fish. The peptides include presynaptic omega-conotoxins that prevent the voltage-activated entry of calcium into the nerve terminal and release of acetylcholine, postsynaptic alpha-conotoxins that inhibit the acetylcholine receptor, and muscle sodium channel inhibitors, the mu-conotoxins, which directly abolish muscle action potentials. These distinct peptide toxins share several common features: they are relatively small (13 to 29 amino acids), are highly cross-linked by disulfide bonds, and strongly basic. The fact that they inhibit sequential steps in neuromuscular transmission suggests that their action is synergistic rather than additive. Five new omega-conotoxins that block presynaptic calcium channels are described. They vary in their activity against different vertebrate classes, and also in their actions against different synapses from the same animal. There are susceptible forms of the target molecule in peripheral synapses of fish and amphibians, but those of mice are resistant. However, the mammalian central nervous system is clearly affected, and these toxins are thus of potential significance for investigating the presynaptic calcium channels. 相似文献
67.
Aluko RE Reaney M McIntosh T Ouellet F Katepa-Mupondwa F 《Journal of agricultural and food chemistry》2004,52(19):6030-6034
A calcium-soluble protein isolate (CSPI) was prepared from the supernatant obtained after addition of 0.75 M calcium chloride to a pH 5.0 aqueous extract of yellow mustard (Sinapis alba) seed meal. Total amino acid analysis showed that the CSPI has significantly higher (p < 0.05) contents of glutamic acid + glutamine, cysteine, and proline when compared to the precipitated, calcium-insoluble proteins. Peptide mass fingerprinting of tryptic peptides of the major polypeptides by mass spectrometry indicated that the CSPI is composed mainly of cruciferin proteins with a contribution from napins (the major allergenic proteins of S. alba). The S. alba CSPI had significantly higher (p < 0.05) protein solubility and emulsion formation ability in the presence of 0.75 M calcium chloride when compared to similar isolates prepared from Brassica juncea (brown mustard) and soybean seed meals. We suggest that the S. alba CSPI could be used to prepare calcium-fortified high protein liquid products. However, the presence of allergenic proteins in this extract may limit its widespread food use. 相似文献
68.
A New Source of Resistance to Puccinia striiformis f. sp. tritici in Spring Wheats (Triticum aestivum) 总被引:1,自引:0,他引:1
The use of P. striiformis f. sp. tritici pathotypes virulent or avirulent with respect to both Yr6 and a previously undescribed source of resistance, designated YrA, allowed the recognition of the corresponding host resistance genes m a range of Australian and exotic spring wheats. The phenotypes conferred by the YrA resistance varied when exposed to contrasting light intensities in the post-inoculation phase. The implications of the results in international studies of host resistance to P. striiformis f. sp. tritici are discussed. 相似文献
69.
Summary Seedling responses to one Australian isolate of each of the stripe rust, stem rust and leaf rust pathogens were determined for 541 accessions of T. dicoccoides collected from 23 locations in Israel. Resistance to stripe rust was more frequent than resistance to stem rust. Stripe rust responses showed a wide range of variability indicative of a number of genes for resistance. Comparison of the present stem rust data and that reported for the same accessions tested in Israel indicated that different genes were operating in each country. Only moderately resistant responses to stem rust were obtained. This level of resistance is probably inadequate for transfer to commercial wheat cultivars. We found no potentially useful seedling resistance to leaf rust. 相似文献
70.
Summary Genes Yr1 for resistance to stripe rust and Pm4a for resistance to powdery mildew showed linkage of 2.0±0.6 cM. Close repulsion linkage probably accounts for the absence in European wheats of genes Yr1 and Pm4b in combination. 相似文献