首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   206篇
  免费   8篇
林业   20篇
农学   6篇
  25篇
综合类   16篇
农作物   4篇
水产渔业   19篇
畜牧兽医   118篇
植物保护   6篇
  2023年   3篇
  2022年   3篇
  2021年   3篇
  2020年   4篇
  2019年   2篇
  2018年   11篇
  2017年   3篇
  2016年   4篇
  2015年   2篇
  2014年   5篇
  2013年   10篇
  2012年   11篇
  2011年   7篇
  2010年   4篇
  2009年   2篇
  2008年   6篇
  2007年   6篇
  2006年   10篇
  2005年   13篇
  2004年   8篇
  2003年   9篇
  2002年   2篇
  2001年   13篇
  2000年   10篇
  1999年   5篇
  1998年   5篇
  1994年   1篇
  1992年   2篇
  1991年   4篇
  1990年   1篇
  1989年   3篇
  1988年   4篇
  1987年   1篇
  1985年   6篇
  1984年   3篇
  1983年   1篇
  1981年   2篇
  1980年   1篇
  1979年   3篇
  1978年   2篇
  1977年   3篇
  1976年   1篇
  1975年   3篇
  1974年   1篇
  1973年   1篇
  1969年   4篇
  1968年   1篇
  1966年   1篇
  1964年   2篇
  1963年   1篇
排序方式: 共有214条查询结果,搜索用时 31 毫秒
31.
Epicotyl length (ECL) of adzuki bean (Vigna angularis) affects the efficiency of mechanized weeding and harvest. The present study investigated the genetic factors controlling ECL. An F2 population derived from a cross between the breeding line ‘Tokei1121’ (T1121, long epicotyls) and the cultivar ‘Erimo167’ (common epicotyls) was phenotyped for ECL and genotyped using simple sequence repeats (SSRs) and single-nucleotide polymorphism (SNP) markers. A molecular linkage map was generated and fifty-two segregating markers, including 27 SSRs and 25 SNPs, were located on seven linkage groups (LGs) at a LOD threshold value of 3.0. Four quantitative trait loci (QTLs) for ECL, with LOD scores of 4.0, 3.4, 4.8 and 6.4, were identified on LGs 2, 4, 7 and 10, respectively; together, these four QTLs accounted for 49.3% of the phenotypic variance. The segregation patterns observed in F5 residual heterozygous lines at qECL10 revealed that a single recessive gene derived from T1121 contributed to the longer ECL phenotype. Using five insertion and deletion markers, this gene was fine mapped to a ~255 kb region near the end of LG10. These findings will facilitate marker-assisted selection for breeding in the adzuki bean and contribute to an understanding of the mechanisms associated with epicotyl elongation.  相似文献   
32.
33.
The role of Tween 80 in biobleaching of unbleached hardwood kraft pulp (HWKP) with manganese peroxidase (MnP) was investigated. Among the surfactants (e.g., Tween 80, Tween 20, CHAPSO) the most significant brightness increase was obtained with Tween 80. Tween 80 and Tween 20 exhibited several effects, such as dispersion of degraded lignin and activation of MnP, that partly contributed to the brightening of HWKP during MnP treatment. However, these characteristics did not explain the most appreciable effect on the brightness increase by Tween 80. Lipid peroxidation of surfactants during MnP biobleaching was determined by measuring the peroxide value (POV). The order of the POV increase was consistent with that of the brightness increase of pulp during MnP treatment in the presence of various surfactants or linolenic acid. However, radicals and peroxides derived from lipid (linolenic acid) peroxidation by lipoxidase hardly brightened the HWKP by themselves. These results suggested that Tween 80 was peroxidized by Mn(III), and that Mn(III) and lipid peroxidation of Tween 80 synergistically brightened HWKP.This study was presented in part at the 43rd lignin symposium, Fuchu, Tokyo, Oct. 26–27, 1998 and the 49th annual meeting of the Japan Wood Research Society, Tokyo, April 2–4, 1999  相似文献   
34.
The cardiac musculature of cranial and caudal venae cavae and pulmonary vein was examined to clarify its distribution pattern in the fowl using both light and electron microscopies. The musculature was distributed from the heart to the root of subclavian vein in the cranial vena cava, to the cranial margin of the liver in the caudal vena cava, and to the left and right distal pulmonary veins in the pulmonary vein, respectively. Judging from the morphology and distribution pattern in the venous wall, the cardiac musculature in the fowl is thought to share the same phylogenic origin with that in mammals. The ultrastructure of cardiac myocytes including transitional cells in the cranial vena cava and the pulmonary vein resembled that of atrial myocytes. While, the typical specialized myocytes such as Purkinje fiber were found in the caudal vena cava of the fowl.  相似文献   
35.
The cardiac musculature of intrapulmonary veins was examined to elucidate its distribution pattern in the musk shrew, the primitive mammalian type, using by both light and electron microscopies. The musculature was distributed extensively from the hilum to the small veins less than 50 microns in diameter, suggesting that the phylogenic origin of this musculature may be traceable to the primitive mammalian types. Ultrastructure of cardiac myocyte in the intrapulmonary venous walls was essentially similar to that of left atrial myocyte. This suggests that the cardiac musculature may contribute to the regulation of pulmonary blood circulation. The abundance of large lipid droplets in both atrial and pulmonary myocytes was also observed and seemed to be the characteristic ultrastructure related to the physiological condition in this animal.  相似文献   
36.
This study evaluated methane (CH4) emission, intake, digestibility, and nitrogen efficiency in sheep fed diets containing replacement levels (0%, 33%, 50%, and 67% of soybean meal with euglena). In this experiment, four Corriedale wether sheep with an initial body weight of 53.8 ± 4.6 were arranged in a 4 × 4 Latin square design. This experiment lasted 84 days, divided into four experimental periods. Each period lasted 21 days, which consists of 14 days of adaptation to the diets, 5 days to collect samples, and 2 days to collect gas emission from sheep. Methane emission expressed as L/kg DM intake or g/kg DM intake reduced by up to 37% and the energy loss via CH4 (% of GE intake) reduced by up to 34%. No differences (> 0.05) were observed in DM and OM intake and whole tract apparent DM digestibility due to substitution of soybean meal with euglena. The total CP loss reduced significantly (linear, < 0.001) and CP efficiency increased linearly (= 0.03) with increasing concentration of euglena. As a result, nitrogen balance and average daily weight gain remained unchanged despite higher nitrogen concentration in soybean supplemented group. In conclusion, substitution of soybean meal with euglena reduced methane emission without affecting the performance of animals.  相似文献   
37.
38.
39.
Volatile organic compounds (VOCs) from wood and their effects on artifacts are of intense interest to museum staff who must strictly manage the preservation environment. In this study, the causal substances of deterioration were inferred by comparison with laser Raman (LR) spectra of deterioration products. The artifact samples were deteriorated using VOCs from woods (WV test), and using specific substances that occur in wood VOCs (SV test). The deteriorated samples were analyzed by LR spectroscopy and the results of the WV and SV tests were compared. Hinokitiol and acetic acid were found to be two of the main causal substances of deterioration in western red cedar. Deterioration of iron and copper by spruce did not appear to be caused by acetic acid, as is generally assumed, but by some other unknown compound(s). Sensitivity to wood-based VOC components depended on the type of artifact. In western red cedar, mitsudasou (litharge) was very sensitive to acetic acid, while other artifacts were sensitive to hinokitiol. The LR method used in this study is very useful for the inference of causal substances of deterioration based on the detection of small amounts of deteriorated products such as those generated by deterioration due to wood VOCs. Part of this article was presented at the 25th Annual Meeting of the Japan Society for the Conservation of Cultural Property, Kyoto, June 2003  相似文献   
40.
 Experimental results were studied to determine the relationships between positioning precision of a differential global positioning system (DGPS) and forest type, antenna height, and season, and to clarify the relationship between sampling number and the convergence of positioning precision. Observation was carried out for 24 h. Mean circular area probability (CEP95) was 2.80 m for deciduous broadleaved trees, and 4.99 m for conifers. The mean CEP95 taken at 7 m height (3.14 m) was higher than that at 1 m height (3.92 m) at all sites. The mean CEP95 taken during the defoliation season (2.65 m) was slightly better than during the foliation season (2.96 m). There were significant differences between forest types (P < 0.001) and antenna heights (P < 0.05). Positioning precision was not noticeably improved if the sampling number was around ten or less. A sampling number of 100–1000 or more is required before substantial improvements can be expected. As long as high positioning precision is not required, it is acceptable to use 2D & 3D modes and relatively few samples to take measurements. Received: April 24, 2002 / Accepted: October 10, 2002 Correspondence to:I. Sawaguchi  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号