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   151篇
  免费   14篇
林业   10篇
农学   27篇
基础科学   2篇
  45篇
综合类   12篇
农作物   5篇
水产渔业   5篇
畜牧兽医   37篇
园艺   5篇
植物保护   17篇
  2023年   5篇
  2022年   5篇
  2021年   4篇
  2020年   4篇
  2019年   5篇
  2018年   5篇
  2017年   14篇
  2016年   5篇
  2015年   9篇
  2014年   6篇
  2013年   19篇
  2012年   13篇
  2011年   11篇
  2010年   9篇
  2009年   7篇
  2008年   7篇
  2007年   5篇
  2006年   7篇
  2005年   2篇
  2004年   5篇
  2003年   2篇
  2002年   2篇
  2001年   1篇
  2000年   3篇
  1999年   2篇
  1998年   1篇
  1997年   3篇
  1996年   1篇
  1992年   2篇
  1989年   1篇
排序方式: 共有165条查询结果,搜索用时 15 毫秒
51.
The oleo-gum resin of Commiphora wightii (Arn.) Bhandari, a pharmacologically important balsamiferous woody shrub, has been used in treating various ailments and disorders since ancient times (2000 B.C.) due to the presence of steroidal compound guggulsterone. Two bioactive isomers of guggulsterone, E and Z, are responsible for lipid- and cholesterol-lowering and anti-cancerous activities. Further, guggul has been approved as food supplement by US-FDA as well as Council of Europe. Indiscriminate harvest of C. wightii from wild with negligible conservation efforts has lead to its inclusion in IUCN assemblage of endangered plant species. For identification of high guggulsterone yielding ecotypes of C. wightii, using high-performance thin-layer chromatographic (HPTLC) analysis, stem samples were collected from 50 plants from eleven locations in arid tracts of Haryana, Gujarat and Rajasthan. Dried, powdered material was subjected to extraction with petroleum ether using soxhlet apparatus. Samples were spotted on precoated activated silica plates (60F-254) and were developed using toluene–acetone (9:1 v/v) as mobile phase. The analysis was carried out in the absorbance mode at 250 nm using HPTLC scanner. The regression analysis data for the calibration plots for E and Z guggulsterone showed good linear relationship with R2 = 1 and 0.9897, respectively. Highest concentration of guggulsterone E (284 μg/g dry wt) was found in the accession collected from Palana, Bikaner whereas highest guggulsterone Z concentration (89.5 μg/g dry wt) was found in the accession collected from CAZRI, Jodhpur.  相似文献   
52.
The Random Amplified Polymorphic DNA (RAPD) technique was used to amplify DNA segments, with the objective of finding markers linked to sex determination in male and female plants of Piper betle L. Two bulks of DNA were made drawing one each from male and female, by pooling an equal volume of DNA samples from each group of individual contributing to the bulk analysis. Fifty different random decamer primers were screened with the two bulks to identify markers associated with sex expression of which only four primers were found to be associated with sex expression. These four primers were then tested with individual plant DNA samples where sex-associated RAPD markers were identified. A ~1,400 and ~850?bp fragment from the primer OPA04 and OPN 02 respectively was found to be present in all the male individuals and absent in all the female plants. In another primer, a ~980?bp amplification product from the primer OPC 06 was present only in the female individuals. A common primer OPA 08 showed both male and female specific markers of 650 and 1,200?bp respectively. Thus, the three male- specific RAPD markers OPA041400, OPA08650 and OPN02850 and two female-specific markers OPA081200 and OPC06980 can reliably differentiate the male and female plants of P. betle L. Ploidy comparison also showed the differences in male and female plants.  相似文献   
53.
The study was conducted to investigate the effect of phosphorus (P) concentrations (0, 5, 10, 20, 50, and 100 μg g−1) on growth and arbuscular mycorrhizal (AM) colonization of two crops (a rainy season crop, Phaseolus mungo Roxb. var. PU-35 and a winter crop, Triticum aestivum L. var. WH-147) and seedlings of two multipurpose tree species (Eucalyptus tereticornis Sm. [Clone C-7, ITC, Bhadrachalam] and Albizia procera Benth.). Plant growth parameters (shoot length, dry weight) and P uptake increased significantly after inoculations with AM fungi (Acaulospora scrobiculata Trappe, Glomus cerebriforme McGee, and Glomus intraradices Schenck and Smith) in P. mungo, T. aestivum, E. tereticornis, and A. procera. Best results were obtained with G. cerebriforme in P. mungo and A. procera, and A. scrobiculata in T. aestivum, and G. intraradices in E. tereticornis. Results on effect of P application on mycorrhizal dependency (MD) of studied crop and tree species showed that decrease in MD with increase in P concentrations in non-nitrogen-fixing species (T. aestivum and E. tereticornis) was higher than in nitrogen-fixing species (P. mungo and A. procera). Threshold P concentrations for maximum benefits from the AM symbiosis in above-mentioned plant species varied from 5 to 20 μg g−1 and corresponding peaks of arbuscules, vesicles, sporocarp formation, colonization index, and spore count per 100 g sand were noticed. Thus, the results showed that the recorded plant growth peaks were due to AM colonization of crops and tree rhizosphere. Inoculations with AMF were more important than P application (explaining 14–78% variation in plant growth) for P. mungo, T. aestivum, and A. procera (forward selection method), whereas P application was more important for growth in E. tereticornis. Therefore, inoculating plants with a suitable AM inoculant could result in a benefit comparable to high P input and lead to a significant saving of inorganic P fertilizer.  相似文献   
54.
In this study, the genotoxic effects of insecticides in different phases of cell cycle were investigated in the mitotic cells of barley (Hordeum vulgare L.). The seeds of H. vulgare L. Var. Karan 4 were treated with different concentrations (0.05%, 0.1% and 0.5%) of insecticides alphamethrin (AM) and monocrotophos (MP) for 6 h after synchronization of cells in G1, S and G2 phase of cell cycle with the help of various presoaking durations (7 h, 17 h and 27 h.). Positive and negative control was run parallel in the form of ethyl methane sulphonate (EMS) and distilled water, respectively. The data indicate that higher dose of alphamethrin and monocrotophos produce toxicity, chromosomal aberrations and mitotic aberrations in Hordeum vulgare L. The present study indicates the genotoxic potential of the insecticides AM and MP and it also showed that S-phase of cell cycle was more sensitive compared to the G1 and G2 phases.  相似文献   
55.
Several Ayurvedic plants are known to have activity against diverse urinary crystals. The traditional knowledge of Ayurveda, collective clinical experience in arthritis and the earlier experimental studies on urinary crystals led to the selection of three plants, viz. Rotula aquatica, Commiphora wightii Bhandari syn. C.mukul. and Boerhaavia diffusa for screening anticrystal activity against basic calcium phosphate (BCP), calcium pyrophosphate (CPPD) and monosodium urate monohydrate (MSUM). The effects of each plant were assayed on microcrystals in 24-well microplates in vitro. Our results show that the aqueous extracts of only R. aquatica and C. wightii have shown crystal dissolving activity against MSUM.  相似文献   
56.
The objective of the study was to evaluate the effects of genetic and non-genetic factors on production of breeding bulls and semen quality parameters in Karan Fries crossbred male by fitting least squares analysis. Genetically, the animals were divided into three subclasses. The non-genetic factors were season of birth, period of birth, and age group with three subclasses each for season of birth and period of birth. Age group was classified into four subclasses. The traits generated in the study were number of males reaching semen donation stage (AFSC) and first freezing (AFSF), age at last semen collection (ALSC) and last freezing (ALSF), age at disposal (AD), and lifetime semen production traits (up to 1 year after first freezing). The effect of period of birth was significant for AFSC, AFSF, ALSC, and AD. It was also significant for total ejaculates produced in a year. The age group had significant effect on AFSF. Effect of genetic group was significant for freezable ejaculates produced in a year, for frozen semen doses produced in a year, and for number of ejaculates cryoprocessed in a year. Season had no statistically significant effect on any of the traits studied. The influence of period revealed that the most of the traits of breeding bulls improved after intermediate period, which could be due to better care, training, feeding, and other management practices in the latter years. However, no consistent trend could be established for the effects of genetic groups and other non-genetic causes on the traits considered.  相似文献   
57.
A set of 50 rice genotypes comprising landraces, local selections, and improved varieties were characterized using simple sequence repeat(SSR) and inter simple sequence repeat(ISSR) markers to study genetic diversity and population structure. Following unweighted pair group method with arithmetic mean based clustering using binary data of polymorphic markers, the genotypes were grouped into 5 clusters and 11 sub-clusters, whereas population structure analysis separated 50 rice genotypes into 5 sub-populations. Grouping of rice genotypes showed better resemblance with the pedigree information of the genotypes. Both genetic diversity and population structure analysis separated majority of the improved varieties from landraces and local selections. Some of the SSR markers amplified unique alleles which were specific to a particular genotype and could distinguish them from the rest. The results indicate that these rice genotypes exhibit a higher genetic diversity and can be very useful in rice improvement program.  相似文献   
58.
β-Asarone content in Acorus calamus is a paramount issue because it limits the usage of plant for medicinal purpose. In the present study A. calamus L. accessions based on RAPD marker, ploidy level and β-asarone content were characterized and correlated on the basis of β-asarone content/ploidy level. Of the 40 random primers used, 6 primers generated polymorphism. Genetic relatedness among accessions evaluated by a similarity matrix based on Dice's coefficient ranged from 0.72 to 0.97. A phenetic dendrogram based on UPGMA analysis grouped accessions into two clusters. A. calamus L. accessions were found to be triploid and tetraploid and their β-asarone content was found in two ranges 6.92–8.0% and 73–88%. The study clustered the accessions as per their ploidy level, β-asarone content and geographical locations. This study would have extensive application in quality control of raw materials.  相似文献   
59.
A new serine protease from the latex of Ipomoea carnea spp. fistulosa (Morning glory), belonging to the Convolvulaceae family, was purified to homogeneity by ammonium sulfate fractionation followed by cation exchange chromatography. The enzyme, named carnein, has a molecular mass of 80.24 kDa (matrix-assisted laser desorption/ionization time-of-flight) and an isoelectric point of pH 5.6. The pH and temperature optima for proteolytic activity were 6.5 and 65 degrees C, respectively. The extinction coefficient (epsilon2801%) of the enzyme was estimated as 37.12, and the protein molecule consists of 35 tryptophan, 76 tyrosine, and seven cysteine residues. The effect of several inhibitors such as iodoacetic acid, diisopropylfluorophosphate, phenyl-methanesulfonyl fluoride, chymostatin, soybean trypsin inhibitor, HgCl2, 3S-3-(N-{(S)-1-[N-(4-guanidinobutyl)carbamoyl]3-ethylbutyl}carbamoyl)oxirane-2-carboxylic acid, N-ethyl maleimide, ethylene glycol-bis(alpha-amino ethyl ether)tetraacetic acid, ethylenediamminetetraacetic acid, and o-phenonthroline indicates that carnein belongs to the family of serine proteases. The enzyme is not prone to autolysis even at very low concentrations. The N-terminal sequence of carnein (T-T-H-S-P-E-F-L-G-L-A-E-S-S-G-L-X-P-N-S) exhibited considerable similarity to those of other plant serine proteases; the highest similarity was with alnus AG12, one of the subtilase family endopepetidases.  相似文献   
60.
Research on marine gastropod breeding in India is in its infancy and scanty literature is only available. To fill the lacunae, marine gastropods of three ornamentally valued and conservation important groups such as Cyprids, Strombids and Muricids were held under captivity and studied for their broodstock maintenance, spawning behaviour, larval rearing and metamorphosis into juveniles at the Shellfish Hatchery of Central Marine Fisheries Research Institute, Tuticorin. Valuable information on the focal themes of the article was obtained for Strombids and Muricids leading to the successful life cycle closing for Lambis lambis and Chicoreus virgineus are reported earlier. In the present study, experiments were conducted on aspects such as post‐metamorphosed juvenile rearing up to 76 days post hatch for L. lambis, spawning, larval development and life cycle closing and reasonable level of juvenile production (8.8%) for Chicoreus ramosus. In addition, the primary observations on the captive breeding of Cypraea tigris with reference to its egg mass, brooding habit and early development is reported. However, while studying these groups few unanswered questions and bottle necks in their breeding nature, larval rearing and metamorphosis arose. The following account details the experiments conducted and results obtained in each of the focal themes of the paper and the constraints faced.  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