全文获取类型
收费全文 | 379篇 |
免费 | 16篇 |
专业分类
林业 | 32篇 |
农学 | 14篇 |
基础科学 | 1篇 |
105篇 | |
综合类 | 18篇 |
农作物 | 24篇 |
水产渔业 | 37篇 |
畜牧兽医 | 134篇 |
园艺 | 13篇 |
植物保护 | 17篇 |
出版年
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 17篇 |
2020年 | 19篇 |
2019年 | 21篇 |
2018年 | 9篇 |
2017年 | 12篇 |
2016年 | 13篇 |
2015年 | 13篇 |
2014年 | 17篇 |
2013年 | 22篇 |
2012年 | 35篇 |
2011年 | 31篇 |
2010年 | 23篇 |
2009年 | 18篇 |
2008年 | 25篇 |
2007年 | 20篇 |
2006年 | 18篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 14篇 |
2002年 | 12篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有395条查询结果,搜索用时 593 毫秒
121.
122.
Summary A variety must be distinguishable, uniform, stable and of sufficient productivity to be officially registered. In Italy landraces of lucerne are still widely used because they are characterized by a good persistence and productivity in their area of origin and adaptation.The landrace from Casalina (20 km south of Perugia, Central Italy) has higher dry matter production than many other commercial cultivars. The objective of this paper was to measure the variation of the landrace Casalina and compare it with that of the commonest cultivars available on the market and with some lines selected from the landrace Casalina.The experiment consisted of 11 entries: Casalina, two selections from Casalina (one for high seed yield and one for frequent cuttings), the registered landrace Italia Centrale and 7 registered cultivars. Each entry was represented by 80 genotypes transplanted in the field 60×40 cm apart in a randomized block design with 4 replications. In 1991 the following characters were recorded on a single plant basis: time of first flowering, height, number of shoots and dry matter yield at the first harvest, time of second flowering, leafiness, height, number of shoots and dry matter yield at the second harvest, height, number of shoots and dry matter yield at the third and fourth harvest. Height, number of shoots and dry matter yield at the first harvest, dry matter at the second and third harvest were recorded during the 1992 season.Casalina was as variable as the other entries in 77% of the comparisons; it was more variable in 8% of the comparisons and less variable in 15% of the comparisons. In conclusion, the variation of landrace Casalina is equal to or less than that of registered varieties so that it could be directly registered at the National Registry of Varieties. 相似文献
123.
124.
Carlos Egberto Rodrigues Júnior Sandro Natal Daniel Diego Galetti Martins Diogo Teruo Hashimoto Fausto Foresti Fabio Porto‐Foresti 《水产资源保护:海洋与淡水生态系统》2020,30(6):1251-1254
- Billfish are oceanic pelagic species that are often caught by tuna fleets and are of great interest for sport fishing. Two species of billfish have specific legislation prohibiting their marketing and export in Brazil.
- DNA barcoding is a universal system of molecular identification based on a sequence of mitochondrial DNA cytochrome oxidase subunit I (COI), which serves as a diagnostic genomic marker in each species.
- The barcode DNA technique was used to identify billfish marketed in the second largest fishing warehouse in Latin America, the CEAGESP (Companhia de Entrepostos e Armazéns Gerais de São Paulo), located in São Paulo, Brazil. Seventy‐nine samples of billfish were collected during three inspection visits carried out by Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis.
- After DNA sequencing, 70 samples (88.60%) were identified to the species level; 21 (30.00%) were identified as Xiphias gladius, 43 (61.42%) as Istiophorus platypterus and six (8.57%) as Kajikia albida. The sale of this latter species is prohibited in Brazil and it is considered Vulnerable on the list of endangered species of the IUCN and in the official list of species of endangered Fauna – Fish and Aquatic Invertebrates.
- Molecular analyses proved to be very efficient at uncovering irregularities in the identification of the white marlin (K. albida), which was traded illegally in CEAGESP, demonstrating the ineffectiveness of the current monitoring techniques used and emphasizing the need for the adoption of better public policies for the conservation of the species.
125.
Konstantinos Tsiamis Ernesto Azzurro Michel Bariche Melih E. inar Fabio Crocetta Olivier De Clerck Bella Galil Fernando Gmez Razy Hoffman Kathe R. Jensen Lyudmila Kamburska Joachim Langeneck Martin R. Langer Ya'arit Levitt‐Barmats Marco Lezzi Agnese Marchini Anna Occhipinti‐Ambrogi Henn Ojaveer Stefano Piraino Noa Shenkar Maria Yankova Argyro Zenetos Ante
uljevi Ana Cristina Cardoso 《水产资源保护:海洋与淡水生态系统》2020,30(4):794-845
- The disproportionately low presence of marine species in the list of invasive alien species (IAS) of Union concern of the European Union (EU) Regulation 1143/2014 does not fully acknowledge the threat they pose to the EU marine environment.
- In this study, the first EU‐scale Horizon Scanning (HS) focusing on marine alien species was performed, aiming to deliver a ranked list of species that should be of high priority for risk assessment (Article 5 of the EU IAS Regulation).
- Species absent from or with a limited distribution in EU marine waters were targeted. In total, 363 alien species were initially screened for HS by a panel of experts, including a broad range of taxonomic groups. Species were scored for their likelihood of arrival, establishment, spread, and impact in EU waters.
- A consensus workshop ranked 267 species, including a subset of 26 prioritized species. These species are considered to be mainly introduced by shipping (fouling and ballast water), via the Suez Canal, and aquaculture activities. The 26 priority species were also scrutinized in terms of feasibility of their management; 18 of them were suggested for performing risk assessments on the basis of the EU IAS Regulation.
- Since biological invasions are dynamic and connected with accelerated globalization and diversified human activities, we recommend HS to be repeated periodically to review the species already listed and assess new ones.
126.
127.
Sansone Umberto Belli Maria Fernandez José A. Comans Rob N. J. Jeran Zvonka Cavolo Fabio Barbizzi Sabrina De Zorzi Paolo Jacimovic Radojko 《Water, air, and soil pollution》2002,141(1-4):313-324
Aquarium experiments were performed to quantify the inorganic fraction of suspended particles deposited on the external surface of aquatic biota. The mass of suspended particles retained on the surfaces of microalgae growing on submerged substrates and the algal biomass were determined by comparing the scandium content of suspended material with that in algal communities. Scandium, a predominantly soil-associated trace element, has been used as a ‘tracer’ for the inorganic component of suspended particles, because this element is geologically ubiquitous in soils, and it is recognized that it cannot cross natural membranes of plants and other organisms. The algal biomass determined using the scandium content was compared with biomass values calculated using phytopigments as estimates of periphyton biomass. The results indicate that the suspended particle mass adhering to the external periphyton surface may accounted for up to 55% of the total mass collected on submerged artificial substrates. 相似文献
128.
Chinnici F Natali N Sonni F Bellachioma A Riponi C 《Journal of agricultural and food chemistry》2011,59(12):6575-6582
The color features and the evolution of both the monomeric and the derived pigments of red wines aged in oak and cherry 225 L barriques have been investigated during a four months period. For cherry wood, the utilization of 1000 L casks was tested as well. The use of cherry casks resulted in a faster evolution of pigments with a rapid decline of monomeric anthocyanins and a quick augmentation formation of derived and polymeric compounds. At the end of the aging, wines stored in oak and cherry barriques lost, respectively, about 20% and 80% of the initial pigment amount, while in the 1000 L cherry casks, the same compounds diminished by about 60%. Ethyl-bridged adducts and vitisins were the main class of derivatives formed, representing up to 25% of the total pigment amount in the cherry aged samples. Color density augmented in both the oak and cherry wood aged samples, but the latter had the highest values of this parameter. Because of the highly oxidative behavior of the cherry barriques, the use of larger casks (e.g., 1000 L) is proposed in the case of prolonged aging times. 相似文献
129.
Berman KH Harrigan GG Nemeth MA Oliveira WS Berger GU Tagliaferro FS 《Journal of agricultural and food chemistry》2011,59(21):11643-11651
The soybean product MON 87701 × MON 89788 expresses both the cry1Ac gene derived from Bacillus thuringiensis and the cp4 epsps (5-enolpyruvylshikimate-3-phosphate synthase) gene derived from Agrobacterium sp. strain CP4. Each biotechnology-derived trait confers specific benefits of insect resistance and glyphosate tolerance, respectively. The purpose of this study was to compare the composition of seed and forage from this combined-trait product to those of conventional soybean grown in geographically and climatically distinct regions. Field trials were conducted in the United States during the 2007 growing season, in Argentina during the 2007-2008 growing season, and in the northern and southern soybean regions of Brazil during the 2007-2008 and 2008-2009 growing seasons. Results demonstrated that the compositional equivalence of MON 87701 × MON 89788 to the conventional soybean extended across all regions and growing seasons. Further evaluation of the data showed that natural variation (region and growing season) contributed more to compositional variability in soybean, particularly for such components as isoflavones, fatty acids, and vitamin E, than transgene insertion. 相似文献
130.
Ana Paula Bilck Sergio Ruffo Roberto Maria Victoria Eiras Grossmann Fabio Yamashita 《Scientia Horticulturae》2011
To produce guavas with good commercial or industrial potential, fruit farmers use phytosanitary practices such as fruit bagging. Bagging protects the fruit mainly from the attack of pests, such as the fruit fly (Anastrepha spp.) and the guava weevil (Conotrachelus psidii), and reduces the use of insecticides and fungicides. This investigation aimed to develop and produce biodegradable films from cassava starch and poly(butylene adipate-co-terephthalate) (PBAT) by extrusion for application in pre-harvest guava fruit bagging. After the fruit harvest, for 6–9 weeks all films were more fragile and rigid, but did not present cracks. BF70 was the most fragile and had the greatest tendency to tear; however, it remained whole until harvesting. Fruit bagged with films BF30, BF50, BF70 was analyzed for fruit quality and compared with PSF control and non-bagged fruit. There was no difference between the treatments relative to physical and chemical characteristics, indicating that biodegradable film did not influence fruit development when compared to the PSF control. 相似文献