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   177篇
  免费   7篇
林业   17篇
农学   15篇
  24篇
综合类   11篇
农作物   11篇
水产渔业   10篇
畜牧兽医   73篇
园艺   1篇
植物保护   22篇
  2023年   3篇
  2022年   6篇
  2021年   2篇
  2019年   4篇
  2018年   3篇
  2017年   8篇
  2016年   7篇
  2015年   3篇
  2014年   8篇
  2013年   14篇
  2012年   7篇
  2011年   10篇
  2010年   9篇
  2009年   9篇
  2008年   11篇
  2007年   10篇
  2006年   11篇
  2005年   9篇
  2004年   12篇
  2003年   11篇
  2002年   8篇
  2001年   3篇
  2000年   3篇
  1999年   3篇
  1998年   2篇
  1993年   1篇
  1991年   3篇
  1989年   1篇
  1983年   1篇
  1982年   1篇
  1968年   1篇
排序方式: 共有184条查询结果,搜索用时 15 毫秒
1.
The seasonal change in petal color and pigmentation of 29 commercial Eustoma cultivars was studied. The flowers are basically divided into four groups according to the major anthocyanidin phenotype in association with petal coloration, i.e., delphinidin (Dp)-based (purple flower), cyanidin (Cy)-based (reddish purple flower), pelargonidin (Pg)-based (pink flower), and none (white flower) groups. The constitution of petal anthocyanidins was not changed by forcing treatment in most of the flowers. Lightness (L*) and chroma (C*, color saturation) showed a change along with the increase/decrease of hue angle difference (ΔH*), thus simultaneously the chromatic tonalities tended to move to redder and bluer, respectively. Floral pigment clustering described two flower groups in a dendrogram, based on anthocyanidin constitutions as phenetic markers, which are apparently the Dp- and Pg-based phenotypes of anthocyanidin syntheses. The Cy-based flowers made a subcluster with the Pg-based flowers, indicating a close relationship in the biosynthesis of the two anthocyanidins, and suggesting the Dp- and Pg-syntheses complement one another.  相似文献   
2.
3.
The foam stability of beer is one of the important key factors in evaluating the quality of beer. The purpose of this study was to investigate the relationship between the level of malt modification (degradation of protein, starch, and so on) and the beer foam stability. This was achieved by examining foam-promoting proteins using two-dimensional gel electrophoresis (2DE). We found that the foam stability of beer samples brewed from the barley malts of cultivars B and C decreased as the level of malt modification increased; however, the foam stability of cultivar A did not change. To identify the property providing the increased foam stability of cultivar A, we analyzed beer proteins using 2DE. We analyzed three fractions that could contain beer foam-promoting proteins, namely, beer whole proteins, salt-precipitated proteins, and the proteins concentrated from beer foam. As a result, we found that in cultivar A, some protein spots did not change in any of these three protein fractions even when the level of malt modification increased, although the corresponding protein spots in cultivars B and C decreased. We analyzed these protein spots by peptide mass finger printing using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. As a result, all of these spots were identified as barley dimeric alpha-amylase inhibitor-I (BDAI-I). These results suggest that BDAI-I is an important contributor to beer foam stability.  相似文献   
4.
We have constructed a physical map of the human genome by using a panel of 90 whole-genome radiation hybrids (the TNG panel) in conjunction with 40,322 sequence-tagged sites (STSs) derived from random genomic sequences as well as expressed sequences. Of 36,678 STSs on the TNG radiation hybrid map, only 3604 (9.8%) were absent from the unassembled draft sequence of the human genome. Of 20,030 STSs ordered on the TNG map as well as the assembled human genome draft sequence and the Celera assembled human genome sequence, 36% of the STSs had a discrepant order between the working draft sequence and the Celera sequence. The TNG map order was identical to one of the two sequence orders in 60% of these discrepant cases.  相似文献   
5.
We estimated the aboveground net primary production (ANPP) in five self-thinning jack pine (Pinus banksiana) stands in Wood Buffalo National Park, NWT, Canada. The stands (11 to ca.175 years old) were selected to examine the relationship between stand density and tree size and its effect on carbon dynamics. Aboveground litterfall was collected from each stand from 1997 to 2012. Stand biomass was estimated by measuring tree size every 5 years and estimating the individual mass using allometric relationships. ANPP was then estimated by summing the litterfall mass, dead stem mass increment and stand biomass increment. We determined the proportional contribution of each organ to the total litter and the seasonal pattern of needle litterfall. There was a lower turnover rate of aboveground biomass in older stands than younger stands. The ANPP increased in the youngest stand (<30 years old) showed a decreasing trend in stands >50 years old. The maximum ANPP was estimated to be ca. 500?g m?2 year?1 in dry matter, which was found in 30–50 year-old stands.  相似文献   
6.
Journal of Plant Diseases and Protection - Three isolates of chrysanthemum white rust fungus, Puccinia horiana, were collected from two regions in Hiroshima Prefecture, Japan, in 2017. In an in...  相似文献   
7.
Forest management and climate change may have a substantial impact on future soil organic carbon (SOC) stocks at the country scale. Potential SOC in Japanese forest soils was regionally estimated under nine forest managements and a climate change scenario using the CENTURY ecosystem model. Three rotations (30, 50, 100 yr) and three thinning regimes were tested: no‐thinning; 30% of the trees cut in the middle of the rotation (e.g. 15 year in a 30‐yr rotation) and thinned trees all left as litter or slash (ThinLef) and the trees from thinning removed from the forest (ThinRem). A climate change scenario was tested (ca. 3 °C increase in air temperature and 9% increase in precipitation). The model was run at 1 km resolution using climate, vegetation and soil databases. The estimated SOC stock ranged from 1600 to 1830 TgC (from 6800 to 7800 gC/m2), and the SOC stock was largest with the longest rotation and was largest under ThinLef with all three rotations. Despite an increase in net primary production, the SOC stock decreased by 5% under the climate change scenario.  相似文献   
8.
9.
Since the beginning of the 20th century, pine trees in Japan have been seriously damaged by the pine wilt disease. This disease is caused by the pine wood nematode, Bursaphelenchus xylophilus, which is transmitted by the Japanese pine sawyer, Monochamus alternatus. The control of disease depends to a large extent on chemicals, but the public is now demanding environmentally friendly control methods. The virulence of B. xylophilus varies very widely. Pre-inoculation of young pine trees in a nursery with avirulent B. xylophilus has induced systemic resistance of trees against a subsequent inoculation with virulent B. xylophilus. This induced resistance was considered a hopeful means for developing a biological control for the disease. The induced resistance by the avirulent nematodes was also expressed in mature pine trees in a forest where the disease was naturally epidemic. However, the effects of induced resistance were not satisfactory for practical biological control. Since the inoculation with higher concentrations of the avirulent B. xylophilus induced the resistance more effectively, the pre-inoculation method will need to be improved to develop the biological control. The induced resistance of pine trees by avirulent B. xylophilus should be one of the candidate biological control methods against pine wilt disease. This induced resistance also provides an experimental system to clarify physiological interactions between the nematodes and pine trees.  相似文献   
10.
Lymphoma was seen in an 11-year-old female savanna monkey (Ceropithecus aethiops). The superficial inguinal and visceral lymph nodes were markedly enlarged, and their architecture was completely effaced by neoplastic cells. The neoplastic cells, which were highly pleomorphic, resembled those in adult T-cell lymphoma-leukemia in humans. Ultrastructurally the neoplastic cells were characterized by nuclear irregularity and clustered dense bodies, and almost all cells showed positivity for CD3. The animal had been reared with her family, and her mother and 2 brothers had antibodies reactive to human T-cell leukemia virus. This virus serologically cross-reacts with simian T-cell leukemia virus, which may be the causative agent of the present neoplasm.  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