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   276篇
  免费   4篇
林业   42篇
农学   33篇
基础科学   3篇
  57篇
综合类   24篇
农作物   16篇
水产渔业   14篇
畜牧兽医   50篇
园艺   5篇
植物保护   36篇
  2024年   1篇
  2023年   6篇
  2022年   7篇
  2021年   8篇
  2020年   10篇
  2019年   9篇
  2018年   7篇
  2017年   10篇
  2016年   11篇
  2015年   4篇
  2014年   8篇
  2013年   19篇
  2012年   16篇
  2011年   15篇
  2010年   14篇
  2009年   9篇
  2008年   13篇
  2007年   15篇
  2006年   9篇
  2005年   12篇
  2004年   10篇
  2003年   13篇
  2002年   16篇
  2001年   10篇
  2000年   7篇
  1999年   6篇
  1998年   2篇
  1994年   1篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1985年   2篇
  1980年   1篇
  1978年   1篇
排序方式: 共有280条查询结果,搜索用时 15 毫秒
151.
152.
A liquid nitrogen (N2) adsorption isotherm was employed to understand the differential pore-volume distribution (PVD) patterns of commercial Clinoptilolite (zeolite) fractions (<125 µ (Z8; fine or micro), 125–250 µ (Z9; medium) and >250 µ (Z10; coarse). The differential PVD of the fractions were calculated from the original Horvath-Kawazoe (HK) model. A full spectrum of pore volume distribution has exhibited “curves symmetric around the origin” irrespective of the Clinoptilolite fractions. However, the fractions exhibited a definite pattern of curves for each of the micro, meso and macropore region. Although, ultramicropores couldn’t be seen in any of the fractions, super micropore region exhibited uni-modal distribution curve with mono-disperse pores for all the fractions with varying pore volumes, while multimodal and tri-modal for meso and macro pore region respectively. Irrespective of the pore region, fine fraction (Z8) exhibited higher differential pore volume than other fractions. It was evident from the differential PVD that particle size has a major role in determining the textural properties of Clinoptilolite fractions.  相似文献   
153.
A total of 236 urinary bladders (94 cattle and 142 buffaloes) collected from Bareilly, Uttar Pradesh, India, were studied for spontaneous lesions. These adult animals belonged to Institute’s organized dairy farm and rural areas in the Rohilkhand region of Uttar Pradesh. Grossly, congestion, hemorrhages, and cystoliths in urinary bladders were diagnosed. Histopathologically, the major conditions diagnosed were acute cystitis, 44 (18.64%), including, congestion, hemorrhages, sub-acute cystitis; chronic cystitis, 74 (31.35%), including chronic cystitis un-complicated type, lymphocytic cystitis, plasmolymphocytic cystitis, follicular cystitis, hyperplasia, nodular/acinar hyperplasia, and cystolithiasis; and nothing unusual diagnosed, 118 (50.00%). Similar types of pathological conditions were diagnosed in both species of animals with exception of follicular cystitis and nodular/acinar hyperplasia which was diagnosed respectively only in buffaloes and cystoliths in cows. In addition, a good number of 17/25 (68%) urinary bladder samples tested were found positive for presence of bovine papillomavirus type-2 (BPV-2) by polymerase chain reaction. These included eight cases of acute cystitis, an equal number of cases of chronic cystitis, and one normal bladder. BPV-2 is known as potential source of enzootic bovine hematuria along with other co-factors in enzootic areas. Lesions of zoonotic significance, like tuberculosis, etc., were not diagnosed. None of the observed lesions represented conditions, which, by themselves, would warrant carcass condemnation in buffaloes.  相似文献   
154.
In a field experiment, the effect of combination of different organic manures on the productivity of crops and soil quality were evaluated in deep vertisols of central India. Combinations of cattle dung manure (CDM), poultry manure (PM), and vermicompost (VC) vis‐à‐vis mineral fertilizers were tested in four cropping systems involving soybean (Glycine max L.), durum wheat (Triticum durum Desf.), mustard (Brassica juncea L.), chickpea (Cicer arietinum L.), and isabgol (Plantago ovata Forsk). The organic manures were applied based on the N‐equivalent basis and nutrient requirement of individual crop. The grain yields of durum wheat and isabgol were higher in the treatment that received a combination of CDM + VC + PM whereas in mustard, CDM + PM and in chickpea, CDM + VC recorded the higher yields. The yield levels in these organic‐manure combinations were similar to the yields obtained with mineral fertilizers. Among the cropping systems, soybean–durum wheat and among the nutrient sources, the combination of CDM + VC + PM recorded the highest total productivity. At the end of the 3‐year cropping cycle, application of organic manures improved the soil‐quality parameters viz., soil organic carbon (SOC), soil available nutrients (N, P, and K), soil enzymes (dehydrogenase and alkaline phosphatase), and microbial biomass C in the top 0–15 cm soil. Bulk density and mean weight diameter of the soil were not affected by the treatments. Among the cropping systems, soybean–durum wheat recorded the highest SOC and accumulated higher soil available N, P, and K. In conclusion, the study clearly demonstrated that the manures applied in different combinations improved the soil quality and produced the grain yields which are at par with mineral fertilizers.  相似文献   
155.
The high growth-stimulating effect of plant extract has urged the plant biotechnologists to use natural supplements in the culture media instead of synthetic phytohormones. We advocated the effect of sprouted sorghum extract(SSE) on emergence, in vitro acclimatization, and genetic fidelity in coleoptile derived callus of indica rice variety ADT36. The use of SSE with Murashige Skoog medium efficiently acclimatized the root and shoot apical systems. A higher mat and seminal roots(3.4 g biomass) with an efficient shoot primordium elongation were observed with an increase in the concentration of SSE. Seeds treated with SSE medium showed higher germination and earlier coleoptile maturation about 48 h compared to untreated seeds, and there was a higher expression of e EF-1α with an increase in coleoptile length. B5 medium was effective on inducing embryogenic and nodular callus from 3-day-old coleoptile with 3.0 mg/L 2,4-dichlorophenoxyacetic acid and further proliferated effectively with 0.8 mg/L kinetin with a fresh weight of 180 mg. Highly significant regeneration was observed with combination of 2.5 mg/L 6-benzylamino purine and 3.0 mg/L α-naphthaleneacetic acid. The metabolic and genetic profiles of in vitro and directly cultivated plants were the same, examined through Fourier-transform infrared spectroscopy, random amplified polymorphic DNA(RAPD), inter-simple sequence repeat(ISSR) and R-ISSR(combination of RAPD and ISSR) markers, respectively, and thus confirming the significant efficacy of the SSE incorporated medium. Disarmed T-DNA was transformed to coleoptile derived callus through Agrobacterium tumefaciens LBA4404 and confirmed by GUS assay. The T-DNA integration was confirmed by DNA blot analysis using DNA from transient GUS-expressed explants. Thus, SSE can be used as a natural and organic supplement for organogenesis and efficient acclimatizations of shoot and root apical meristems in regenerated plants.  相似文献   
156.
Tomato leaf curl disease (ToLCD) affected 25% of the tomato crop in Chitrakoot, India and symptomatic leaves were collected for molecular assay. The complete sequences of bipartite begomovirus DNA-A and a betasatellite DNA were amplified. In a sequence analysis, begomovirus DNA-A and betasatellite shared highest sequence identity (91–99%) with Tomato leaf curl New Delhi virus (ToLCNDV) DNA-A and chili leaf curl betasatellite (ChLCB), respectively. The virus was transmitted by whitefly to tomato plants and caused ToLCD symptoms with 70% transmission rate. To our knowledge, this is the first report of the natural occurrence of ToLCNDV and ChLCB in India.  相似文献   
157.
Ficin (EC 3.4.22.3), a cysteine proteinase isolated from the latex of a Ficus tree, is known to occur in multiple forms. Although crude ficin is of considerable commercial importance, ficin as such has not been fully characterized. A major ficin from the commercial crude proteinase mixture preparation of Ficus carica was purified and characterized. The purified enzyme was homogeneous in both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel-filtration chromatography and is a single polypeptide chain protein with a molecular mass of 23 100 +/- 300 Da as determined by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF). The enzyme was active in the pH range of 6.5-8.5, and maximum activity was observed at pH 7.0. The N-terminal core sequence of ficin has homology with N-terminal sequences of plant cysteine proteinases. The enzyme contains three disulfide bonds and a single free cysteine residue at the active site. The effect of co-solvents, such as sorbitol, trehalose, sucrose, and xylitol, on the thermal stability of ficin was determined by activity measurements, fluorescence, and thermal denaturation studies. The apparent thermal denaturation temperature (T(m)) of ficin was significantly increased from the control value of 72 +/- 1 degrees C in the presence of all co-solvents. However, the maximum stabilization effect was observed in terms of thermal stabilization by the co-solvent trehalose.  相似文献   
158.
This study presents the structural characteristics and regeneration potential of mangrove patches in the estuarine and coastal areas of Kerala, a tropical maritime state in India. Field surveys were carried out at 46 selected sites during August 2015 to May 2016. In each site, the vegetative structure and regeneration status were assessed using the quadrat method. Altogether 219 quadrates were laid out and a total of 13 true mangrove species, belonging to 5 families and 8 genera, were recorded. The total tree density and stand basal area of the study region was1678.08/ha and 20.33 m^2/ha respectively. The low basal areas indicate the reduced structural development in mangroves. Of the 13 tree species, Avicennia constitutes 56%of the total Important Value Index(IVI) and Avicennia officinalis represents 41% of the IVI in Kerala, followed by Avicennia marina(15%), Rhizophora mucronata(15%),Sonneratia alba(8%) Rhizophora apiculata(7%) and Excoecaria agallocha(7%). The diameter at breast height(DBH) in the study area revealed that 47% of the tree species came under the 1–10 cm DBH class. Total sapling and seedling density in Kerala was 2238.35 and 3232.42 individuals/ha respectively. Density of young plants(seedlings ? saplings) was only 31% greater of tree density and varied from 3–63%, which indicates poor regeneration potential. The Maturity index value(MIV) and complexity index(Ic) value of mangroves were 18.30 and 109.81 respectively. However, the low Ic value(\ 10) observed in seven out of ten coastal districts indicated poor structural development of mangroves in Kerala. Therefore, locationspecific conservation and management measures, guided by the knowledge on spatial distribution and habitat requirements of mangrove varieties should be taken to preserve the mangrove diversity of Kerala.  相似文献   
159.
Multiple element analyses were carried out to investigate variation in element concentrations in barley grains of 336 genotypes. Of 13 elements analyzed, Ba ranged from 0.2 to 8.9?mg kg?1, Ca from 186.4 to 977.5?mg kg?1, Cu from 1.5 to 9.8?mg kg?1, K from 353.2 to 7721.5?mg kg?1, Mg from 1049.8 to 2024.2?mg kg?1, Mn from 8.1 to 22.9?mg kg?1, Na from 55.9 to 627.9?mg kg?1, P from 2272.9 to 5428.8?mg kg?1, S from 880.7 to 1898.0?mg kg?1, Si from 19.1 to 663.2?mg kg?1, and Sr from 0.35 to 2.62?mg kg?1 in the barley grain. The least square means showed high Zn, Fe, Mg, P, and S concentration in AM-64 and AM-228 genotypes. The principal component analysis of element concentration showed four PCs explained 64.3% total variance. Strong positive correlations (p?<?0.001) of Fe-Mn, Fe-S, S-Mn, Zn-P, Zn-Mg, Mg-P, Mg-Mn, and Ca-Sr were found. The identification barley genotypes that showed high elements concentration furnish valuable genetic resources for biofortification in future.  相似文献   
160.
Sixteen tenorrhaphies were performed at the mid-metatarsal region in eight buffalo calves under lignocaine epidural analgesia. A 2 cm long gap was created in the superficial digital flexor (SDF) tendon and immediately repaired with acellular grafts in animals of group I, 1% glutaraldehyde-preserved tendon allografts in group II. In group III, the defect was repaired with autografts. This group served as control. The contralateral limb in each animal was operated after an interval of 60 days and the animals underwent the same procedure according to the designed groups. Diclofenac sodium and Enrofloxacin was given post-operatively for 5 days. Clinical examination revealed significant increase (P < 0.05) in rectal temperature, heart and respiratory rate for 3-4 postoperative days in all the animals. Mild pain and exudation as well as early restoration of tendon gliding movements and weight-bearing were observed earlier in group I in comparison with group II. Air-tendograms revealed early organization, minimal adhesion formation and lesser thickening of tendon at the reconstructive site in the acellular group whereas in the glutaraldehyde group dense homogenous swelling with adhesions was seen along the flexors. Angiography on day 30 showed that the area of proximal and distal host tendon graft junction appeared hypervascularized, whereas the area occupied by the graft appeared relatively less vascularized. Normal vascularization was observed on day 90 in all the three groups.  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