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   171篇
  免费   1篇
林业   15篇
农学   5篇
  23篇
综合类   10篇
农作物   4篇
水产渔业   14篇
畜牧兽医   48篇
园艺   7篇
植物保护   46篇
  2023年   3篇
  2022年   4篇
  2021年   3篇
  2020年   2篇
  2018年   2篇
  2016年   3篇
  2015年   8篇
  2014年   5篇
  2013年   13篇
  2012年   4篇
  2011年   11篇
  2010年   7篇
  2009年   8篇
  2008年   13篇
  2007年   8篇
  2006年   6篇
  2005年   13篇
  2004年   13篇
  2003年   12篇
  2002年   8篇
  2001年   3篇
  2000年   8篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1995年   1篇
  1993年   1篇
  1992年   2篇
  1991年   3篇
  1990年   1篇
  1988年   1篇
  1985年   1篇
排序方式: 共有172条查询结果,搜索用时 15 毫秒
91.
The antifungal glycoalkaloid -tomatine accumulates in tomato plants and may protect plants from fungal infection. Fusarium oxysporum f. sp. lycopersici, the causal agent of vascular wilt of tomato, produces a tomatinase (FoToml) that degrades -tomatine to the nontoxic compounds tetrasaccharide lycotetraose and tomatidine. Induction of tomatinases and the distribution of FoToml homologs were examined among 30 strains belonging to 16 formae speciales of F. oxysporum. Tomatinase activity was found in 27 strains belonging to 15 formae speciales, but FoToml homologs (>98% sequence identity) were detected in only six strains belonging to four formae speciales. To identify tomatinases other than FoToml, -tomatine-inducible proteins of another tomato pathogen F. oxysporum f. sp. radicis-lycopersici were analyzed by two-dimensional gel electrophoresis. A protein with a molecular mass of 64kDa accumulated in the -tomatine-induced culture filtrates, and the protein had tomatinase activity, degrading -tomatine to lycotetraose and tomatidine.  相似文献   
92.
The journal Fisheries Oceanography provides a global forum for fisheries scientists and oceanographers to understand how marine ecosystems, and the services they provide to society, are structured and shaped by environmental variability and climate change. With this special issue, as well as the 30th Anniversary Virtual Issue of the most influential papers from the journal's history, we commemorate 30 years of publishing leading research in the field of fisheries oceanography. These issues showcase the extent, depth and impact of the research published in Fisheries Oceanography. We also reflect on the evolution of research themes through the journal's history, and highlight key emergent themes in our field. We look forward to continuing to publish impactful research in the pages of Fisheries Oceanography in the years ahead.  相似文献   
93.
Tobacco mosaic virus (TMV) was detected by ELISA, electron microscopy and/or bioassay from bumblebee (Bumbus terrestris), pollen clumps, nest materials and bee-visited anthers of flowers from greenhouses in which tomatoes had been pollinated by bees and were severely infected with TMV. Experimental bee-mediated transmission of TMV in greenhouse tomatoes demonstrated that the bumblebees transported TMV from plant to plant and that they spread the virus in greenhouses. This is the first report describing TMV transmission by bumblebees. Received 11 August 1999/ Accepted in revised form 30 September 1999  相似文献   
94.
The Shimokita Peninsula in Aomori Prefecture, Japan, which is inhabited by Japanese monkeys (Macaca fuscata), is the northernmost habitat for wild primates in the world. This study was the first to determine the conception dates of specific individuals and estimate the pregnancy rate of wild populations in this region. The pregnancy rate of animals aged 5 years or more at delivery was estimated to be 40.9% (27/66). Conception dates of each fetus were also estimated using a regression line of Pig-tail monkeys (Macaca nemestrina), which are taxonomically related to Japanese monkeys and have a similar physique. The conception dates were distributed across 90 days between September 24th and December 23rd, with a mean conception date of November 4th (SD=22.3 days, n=53). Using these findings, the mean birth date was estimated as April 25th, more than two weeks earlier than the mean birth date in previous research determined using direct observations carried out over the past 20 years ago. Global warming due to climate change is thought to be one of the main causes of this difference.  相似文献   
95.
Troponin T (TnT) is one of the myofibrillar proteins that is easily degraded during postmortem aging of pork. In this study, we determined the N-terminal amino acid sequences of TnT degradation fragments produced during postmortem aging and by m-calpain hydrolysis. The N-terminal amino acid sequences of TnT fragments produced during postmortem aging were EVHEPEEKPRPKLTAP, EKPRPKLTAPKIPEG, and APKIPEGEKVDF. On the other hand, the N-terminal amino acid sequences of TnT fragments produced by the action of m-calpain were APPPPAEV, EVHEPEEK, and APK. These sequences of degradation fragments could be mapped on fast type TnT isoform 2. The peptide bonds of His37-Glu38 and Thr51-Ala52 in fTnT2 were cleaved during postmortem aging as well as by the calpain hydrolysis; therefore, calpain was concluded to have an important role in TnT degradation during postmortem aging. It was also found that the sourness-suppressing peptide APPPPAEVHEVHEEVH (Okumura et al. Biosci. Biotechnol. Biochem. 2004, 68, 1657-1662) derived from TnT degradation could be produced by the action of calpains on Glu21-Ala22 and His37-Glu38 sites.  相似文献   
96.
A novel potyvirus, tentatively named Ornithogalum virus 2 (OV-2) because only its nucleotide sequence of the coat protein gene has been revealed, was isolated for the first time from Ornithogalum thyrsoides. OV-2 had a flexuous particle (700–740 nm in length) and was sap and aphid transmissible. The virus had a narrow host range; of 36 test plants in 12 families, only O. thyrsoides and O. dubium were infected. Because the virus caused characteristic stripe mosaic on O. thyrsoides, we propose Ornithogalum stripe mosaic virus (OrSMV), instead of OV-2 for the proper name of the virus. The nucleotide sequence data reported is available in the DDBJ/EMBL/GenBank databases under accession number AB271783.  相似文献   
97.
Many Japanese dragonfly species depend on habitat complexes maintained in rice paddy systems. We postulated that recent alterations to habitat complexes in paddy systems have had adverse effects on dragonfly populations, especially those ‘once common species’ that have come to depend primarily on paddy systems following losses of natural floodplain habitats. A high proportion of Japanese lentic dragonfly species depends on paddy fields or agricultural ponds that have been extensively degraded, while lotic species can often use both paddies and natural river systems. Thus we also postulated that lentic species are more susceptible to changes in agricultural habitats and are subject to higher extinction risks than lotic species. We aimed to extend previous work on estimating dragonfly extinction risk by developing mechanistic insights into the processes involved. Postulates were tested by analyzing relationships between (1) previous quantitative extinction risk assessments for dragonfly species and (2) species’ ecological characteristics (i.e., distribution range and habitat type [lentic or lotic]). Lentic species were disproportionately represented among those with elevated extinction risk. Species with large distribution ranges were also subject to higher extinction risks than those with narrower ranges, reflecting a driving force acting at a national scale (i.e., intensive degradation of paddy systems).  相似文献   
98.
Dual functions (insect repelling and capturing) of a single-charged dipolar electric field screen were evaluated to successfully exclude whiteflies from a window-open greenhouse. The screen consisted of three parts: 1) insulated conductor wires (ICWs) arrayed in parallel at 5?mm intervals, 2) two earthed stainless nets placed within 3?mm of both sides of the ICW layer, and 3) a voltage generator for the negatively charged ICWs. The screen formed two electric fields between the ICW-layer and the ICW-side surface of the earthed net and between the ICWs. At negative charging of 1.5–2.5?kV, all whiteflies reaching the outer surface of the screen net avoided entering the electric field and flew away from the screen. This avoidance was disturbed by 3?m s?1 wind, as the insects were compulsorily blown inside. However, almost all whiteflies (99.4?%) were captured with the ICW. These results indicate that the insect-capturing function is effective to complement a failure to repel. A greenhouse assay was conducted in the screen-attached and non-screened parts in which a greenhouse was divided with a partition. During the 3-month operation, the screen was durable and functional for excluding pests, and better air ventilation changed the climate conditions in the greenhouse. Thus, the present study demonstrated that our electric field screen can provide an airy condition for tomatoes in a window-open greenhouse and successfully exclude whiteflies using dual screen functions.  相似文献   
99.
Involvements of estrogen receptor (ER)α, proliferating cell nuclear antigen (PCNA) and p53 in the uterine carcinogenesis process in Donryu rats, a high yield strain of the uterine cancer were investigated immunohistochemically. ERα was expressed in atypical endometrial hyperplasia, accepted as a precancerous lesion of the uterine tumors, as well as well- and in moderately-differentiated endometrial adenocarcinomas, and the intensities of expression were similar to those in the luminal epithelial cells of the atrophic uterus at 15 months of age. The expression, however, was negative in the tumor cells of poorly differentiated type. Good growth of implanted grafts of the poorly-differentiated adenocarcinomas in both sexes with or without gonadectomy supported the estrogen independency of tumor progression to malignancy. PCNA labeling indices were increased with tumor development from atypical hyperplasia to adenocarcinoma. The tumor cells in poorly-differentiated adenocarcinomas were positive for p53 positive but negative for p21 expression, suggesting accumulation of mutated p53. These results indicate that the consistent ERα expression is involved in initiation and promotion steps of uterine carcinogenesis, but not progression. In addition, PCNA is related to tumor development and the expression of mutated p53 might be a late event during endometrial carcinogenesis.  相似文献   
100.
Due to the long parturition period of raccoons, we assumed that age at first conception of late born females was later than that of early born females. From March 2005 to September 2008, 201 females estimated to be younger than 24 months were separated into early- and late-born groups on the basis of their estimated birth month (to the nearest 2 months), and parous status and body mass index (BMI) were examined. Age at first conception of late-born females (over 18 months old) was estimated to be later than that of early-born females (over 12 months old). The average BMI in early-born individuals at 12 months old might have affected their ability to conceive because of body fat deposition.  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