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   791篇
  免费   38篇
  国内免费   7篇
林业   102篇
农学   31篇
基础科学   3篇
  118篇
综合类   40篇
农作物   18篇
水产渔业   108篇
畜牧兽医   343篇
园艺   12篇
植物保护   61篇
  2024年   1篇
  2023年   3篇
  2022年   6篇
  2021年   28篇
  2020年   13篇
  2019年   13篇
  2018年   15篇
  2017年   23篇
  2016年   21篇
  2015年   42篇
  2014年   33篇
  2013年   42篇
  2012年   58篇
  2011年   51篇
  2010年   40篇
  2009年   37篇
  2008年   66篇
  2007年   65篇
  2006年   46篇
  2005年   53篇
  2004年   43篇
  2003年   49篇
  2002年   36篇
  2001年   16篇
  2000年   9篇
  1999年   2篇
  1998年   11篇
  1997年   5篇
  1996年   3篇
  1994年   3篇
  1993年   1篇
  1980年   1篇
  1977年   1篇
排序方式: 共有836条查询结果,搜索用时 17 毫秒
101.
Genetic diversity of 30 radish (Raphanus sativus L.) accessions was investigated at the phenotypic level with morphological characters and at the DNA level using the random amplified polymorphic DNA (RAPD) technique. Thirty-six morpho-physiological traits were recorded from seedling stage to harvest. The 31 primers used generated 202 RAPD bands, of which 158 (78.2%) were polymorphic. Multivariate procedures were used to classify the germplasm on the basis of phenotypic traits and RAPD fragments. Dendrograms were generated for the Euclidean distance from the morphological data and the Nei's genetic distance from the RAPD markers. Phenotypically, all the accessions were classified into four major groups corresponding to the different forms of cultivated radish. The morphological diversity existing within each of these groups suggested that they should be discriminated into the three botanical convarieties, sativusT (large-rooted), caudatus (pod-type) and oleifer (oilseed-type). Clustering of the accessions did not show any pattern of association between the morphological characters and the collection sites. Instead, landrace groups were associated with their morphological similarities and horticultural uses. On the other hand, the intra-specific genetic relationships of several accessions based on RAPD analysis were related primarily to their collection sites rather than to their phenotypic affinities. The level of polymorphism exhibited by the various convarieties could be exploited in genetic mapping populations to tag economically important traits. These genotypes also could serve as a useful germplasm source for root, leaf, pod and seed. This preliminary study of traditional radish landraces from Pakistan provides useful information regarding their horticultural potential.  相似文献   
102.
This study was carried out to investigate whether expensive enzyme-treated fish meal (EFM) can be partially replaced by soybean meal (SM) or enzyme-treated SM (ESM) without compromising the growth of captive-raised Pacific bluefin tuna (PBT) juveniles. Five fish diets were tested: EFM (control) and EFM in which 10 or 20% of the EFM was replaced with either ESM or SM (ESM10, ESM20, SM10 and SM20, respectively). The respective diets were provided to 28-day-old PBT juveniles (mean body weight approx. 0.38 g) stocked randomly in 15-m3 tanks (276 juveniles per tank; two tanks per treatment) for 12 days. The final mean body weight of PBT juveniles on diets EFM, SM10, and SM20 was significantly higher than that of juveniles on diet ESM20. Although daily feeding rate was significantly higher in the ESM and SM groups, feed efficiency (FE) was significantly higher in the EFM group; there was no significant difference between juveniles fed diets EFM and SM10. Protein and phosphorus retention efficiency were significantly lower in the ESM20, and ESM20 and EFM groups, respectively. Phosphorus discharge was significantly lower in the SM groups. The results demonstrate that 10% SM (11% EFM replacement) can be included in EFM without compromising the growth performance of PBT juveniles.  相似文献   
103.
Occurrence of pale potato cyst nematode, Globodera pallida (Stone) Behrens, was first recorded in Japan in 2015. Among several control measures, cultivation of resistant potato (Solanum tuberosum L.) varieties is the most effective in cost and environmental impact. As no G. pallida-resistant varieties have yet been developed in Japan, great emphasis is being placed on screening of germplasm possessing the resistance and development of the resistant varieties. In this study, we first improved previously reported DNA markers linked to the G. pallida resistance loci (GpaIVsadg and Gpa5) and then used these to screen more than 1,000 germplasms to select several candidate germplasms with resistance. We performed inoculation testing on the selected candidates and identified several resistant germplasms to the Japanese G. pallida population. Furthermore, we developed a simultaneous detection method combining three DNA markers linked to G. pallida and Globodera rostochiensis (Wollenweber) Behrens resistance loci. We validated the ability of C237-I marker to select resistant allele of GpaIVsadg and predict the presence of resistance in a Japanese breeding population. Resistant germplasms identified in this study could potentially be used to develop G. pallida-resistant varieties. The marker evaluation methods developed in this study will contribute to the efficient development of resistant varieties.  相似文献   
104.
Sustainable management of the kelp forests of the Shiretoko Peninsula, a World Natural Heritage site, is necessary due to kelp’s ecological and economic importance. The objectives of this study were to estimate the area of kelp forests and to clarify their spatial characteristics in coastal waters of the Shiretoko Peninsula. Data on the presence/absence and thickness of kelp forests were collected via acoustic observation on transects over about 80 km using an echosounder at 200 kHz. Acoustic data were geostatistically interpolated, and the areas covered by kelp forests were estimated. Differences in kelp distribution between the eastern and western sides of the peninsula were compared. The total area of kelp forest was 3.88 km2 (eastern area: 3.49 km2; western area: 0.39 km2). The range of thickness of the kelp forests was 34–91 cm. Many kelp forests in the eastern area were thick (>78 cm) and distributed continuously, while kelp forests in the western area were sparsely distributed.  相似文献   
105.
Sequence analysis based on the anterior part of the mitochondrial DNA control region was carried out to reveal the genetic diversity, stock structure, and historical demography of the red tilefish. Nucleotide sequences of 388 bp in length were determined for 280 individuals taken from eight localities. The molecular diversity, haplotype diversity, and nucleotide diversity were relatively high (average h = 0.929 ± 0.011; average π = 0.008 ± 0.005). The mismatch distribution was not significantly different from the expected distribution for a rapidly expanding population (P = 0.453). The minimum spanning network connecting with full-sequence haplotypes contained star-like topologies derived from multiple ancient lineages, supporting the mismatch distribution analysis. No significant genetic differentiation was observed among eight localities (maximum pairwise F ST = 0.023, reduced-sequence data set). Our results suggest a large panmictic population of the red tilefish along the coast of Honshu to the East China Sea.  相似文献   
106.
Fisheries Science - Fish oil containing omega-3 polyunsaturated fatty acids (PUFA) attenuates chronic inflammation found in obesity, leading to a reduction in insulin resistance. The effect of fish...  相似文献   
107.
Fisheries Science - The novel organic selenium compound, selenoneine, is found in the blood of tuna and has metal-binding activity. In this report, selenoneine displays tyrosinase inhibitory...  相似文献   
108.
Fatty-acid esters of dinophysistoxin-1 (DTX1) in scallops Patinopecten yessoensis, mussels Mytilus coruscus, and toxic dinoflagellate Dinophysis species, collected from Japanese seawater, were analyzed by liquid-chromatography mass spectrometry (LC–MS). Precursor ion monitoring, multiple reaction monitoring for 18 fatty-acid esters of DTX1, and full-scan MS/MS spectra obtained with a hybrid triple–quadrupole linear-ion-trap mass spectrometer showed that 14:0, 16:0, and 16:1 esters were the most abundant 7-O-acyl-DTX1 analogues in bivalves. Fatty-acids esters formed by conjugations at hydroxyl positions other than the 7-position of DTX1 were not detected in the bivalves. DTX1 and okadaic acid-16:0 fatty-acid esters have been reported as the most abundant ester in bivalves in several previous studies; however, we found that 7-O-16:1-DTX1 was the most abundant ester in some mussels in which 16:1 was more dominant than 16:0 in the free fatty-acid profile. Comparison between 7-O-acyl-DTX1 and free fatty-acid profiles in the same bivalve samples suggests that polyunsaturated fatty acids are selectively excluded in enzymatic acylation of DTX1. No 7-O-acyl-DTX1 was detected in any single-cell isolates of D. fortii, D. acuminata, D. mitra, D. norvegica, D. tripos, D. infundibulus, and D. rotundata.  相似文献   
109.
A translucent collagen gel was formed from a transparent acidic solution of red stingray collagen by adjusting to physiological ionic strength and pH in phosphate buffer and then incubating at 25–37°C. During fibril formation from red stingray collagen, the turbidity increased when the NaCl concentration was increased at constant pH and the rate of fibril formation was accelerated by higher pH or lower NaCl concentration. The T m of red stingray collagen fibrillar gel was estimated as 44.3 ± 3.5°C, which was higher than that of the collagen solution, 33.2°C. In addition, red stingray collagen gel maintained its shape without melting and was suitable for culture of mouse stromal cells at 37°C.  相似文献   
110.
Canine gastroesophageal intussusception (GEI) is a rare and life-threatening condition that requires prompt diagnosis and treatment. A 19-day-old Siberian Husky with a 4-day history of regurgitation was diagnosed with GEI based on the findings of computed tomography (CT) performed without anesthesia. Endoscopic reduction of intussusception was impossible; thus, surgical reduction by traction of the duodenum was performed. CT revealed improvement of megaesophagus 82 days postoperatively. Eleven months postoperatively, fluoroscopy showed recovery to nearly normal esophageal motility. Two years postoperatively, no clinical signs were reported. CT is useful to diagnose GEI in neonate puppies with poor abdominal fat and to assess the gastric edema and the anatomical association of stomach with other organs. Fluoroscopy is helpful for evaluating postoperative esophageal motility.  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