全文获取类型
收费全文 | 981篇 |
免费 | 76篇 |
国内免费 | 1篇 |
专业分类
林业 | 82篇 |
农学 | 39篇 |
基础科学 | 15篇 |
197篇 | |
综合类 | 76篇 |
农作物 | 58篇 |
水产渔业 | 134篇 |
畜牧兽医 | 362篇 |
园艺 | 18篇 |
植物保护 | 77篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 17篇 |
2021年 | 44篇 |
2020年 | 61篇 |
2019年 | 51篇 |
2018年 | 51篇 |
2017年 | 45篇 |
2016年 | 36篇 |
2015年 | 38篇 |
2014年 | 46篇 |
2013年 | 53篇 |
2012年 | 84篇 |
2011年 | 78篇 |
2010年 | 44篇 |
2009年 | 40篇 |
2008年 | 38篇 |
2007年 | 50篇 |
2006年 | 28篇 |
2005年 | 24篇 |
2004年 | 26篇 |
2003年 | 27篇 |
2002年 | 24篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 16篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 4篇 |
1965年 | 3篇 |
1963年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有1058条查询结果,搜索用时 15 毫秒
11.
David Santiago‐Ramos Juan de Dios Figueroa‐Crdenas Jos Juan Vles‐Medina Rosalía Reynoso‐Camacho Minerva Ramos‐Gmez Marcela Gaytn‐Martínez Eduardo Morales‐Snchez 《Cereal Chemistry》2015,92(5):475-480
The objective of the present work was to study the effect of annealing and concentration of Ca(OH)2 (lime) and calcium salts on the thermal and rheological properties of maize starch during an ecological nixtamalization process. Thermal and rheological properties of maize starch changed during the ecological nixtamalization process because of three main causes: the annealing phenomenon, type of calcium salt, and calcium salt concentration. In all treatments thermal properties (To, Tp, and Tf) of nixtamal starch increased owing to the annealing process, whereas the type of salt or lime increased thermal properties and decreased pasting properties in this order: CaCl2 > CaSO4 > Ca(OH)2 ≈ CaCO3. This behavior was because of the dissociation of each salt or lime in water. Anions (OH−) can penetrate much more easily into the starch granule and start the gelatinization process by rupturing hydrogen bonds. Additionally, amylose‐lipid complexes were formed during the nixtamalization processes, as indicated by an increasing peak at 4.5 Å in X‐ray diffraction patterns. 相似文献
12.
Morphological and Immunohistochemical Characterization of Canine Osteosarcoma Spheroid Cell Cultures 下载免费PDF全文
Spheroid cell culture emerges as powerful in vitro tool for experimental tumour research. In this study, we established a scaffold‐free three‐dimensional spheroid system built from canine osteosarcoma (OS) cells (D17). Spheroids (7, 14 and 19 days of cultivation) and monolayer cultures (2 and 7 days of cultivation) were evaluated and compared on light and electron microscopy. Monolayer and spheroid cultures were tested for vimentin, cytokeratin, alkaline phosphatase, osteocalcin and collagen I by means of immunohistochemistry. The spheroid cell culture exhibited a distinct network of collagen I in particular after 19‐day cultivation, whereas in monolayer cultures, collagen I was arranged as a lamellar basal structure. Necrotic centres of large spheroids, as observed in 14‐ and 19‐day cultures, were characterized by significant amounts of osteocalcin. Proliferative activity as determined by Ki‐67 immunoreactivity showed an even distribution in two‐dimensional cultures. In spheroids, proliferation was predominating in the peripheral areas. Metastasis‐associated markers ezrin and S100A4 were shown to be continuously expressed in monolayer and spheroid cultures. We conclude that the scaffold‐free spheroid system from canine OS cells has the ability to mimic the architecture of the in vivo tumour, in particular cell–cell and cell–matrix interactions. 相似文献
13.
Maria Clia Ramos Bellenzani PhD Associate Professor Júlia Maria D'andrea Greve PhD Professor-Physiatrics Csar Augusto Martins Pereira 《Journal of Equine Veterinary Science》2007,27(11):475-480
Horseshoeing is a common practice, but effects on the hoof wall are poorly understood. Strain gauges were used to document and compare hoof behavior in vitro during flat weight bearing and after artificial heel elevation. Ten front limbs of Thoroughbred race horses, shod with conventional flat shoes, were used. Eight strain gauges were symmetrically distributed around the toe, quarters, and heels. Each limb was mounted to a testing machine (Kratos K5002; Kratos Dynamômetros, Ltda., Cotia-SP-Brazil) and subjected to a load equivalent to 30% of the donor's body weight. Strains (μ) were acquired by means of a computerized system and the results compared using Friedman and Wilcoxon statistical tests. There was greater strain variation when the heels were elevated. Compression predominated during flat weight bearing, with a tendency to horizontal traction after heel elevation. The changes in strain caused by heel elevation were not always symmetrical. Elevation of the heels tensed the toe and the medial quarter horizontally, increased load at the posterior portion of the hoof capsule, and hindered its expansion. 相似文献
14.
Ramos Silva JC Marvulo MF Dias RA Ferreira F Amaku M Adania CH Ferreira Neto JS 《Preventive veterinary medicine》2007,78(3-4):286-295
From September 1995 to February 2001, blood samples were collected from 865 neotropical felids belonging to 8 different species. These animals were housed in 86 institutions located in 78 cities of 20 Brazilian states. Our goal was to identify the risk factors associated with sero-positivity to Toxoplasma gondii in captive neotropical felids from Brazil. All serum samples were tested by the modified agglutination test (MAT), using formalin-fixed whole tachyzoites and mercaptoethanol. For each animal an individual questionnaire was filled with questions about tattoo number, felid species, age, sex, origin, number of animals in the group, introduction of new animals in the group, time in the institution, eating meat previously frozen for a period <7 days in the last 6 months, eating meat of run-over or euthanized animals in the last 6 months, predation of rodents or birds in the last 6 months and presence of domestic cats near the enclosures in the last 6 months. The total sero-prevalence was 55% (95% CI: 52%, 57%). We estimated a prevalence of 46% (95% CI: 40%, 54%) for jaguarundi (Puma yagouaroundi); 58% (95% CI: 53%, 63%) for ocelot (Leopardus pardalis); 50% (95% CI: 45%, 56%) for oncilla (L. tigrinus); 54% (95% CI: 46%, 62%) for margay (L. wiedii); 12% (95% CI: 4%, 31%) for Pampas-cat (L. colocolo); 83% (95% CI: 65%, 93%) for Geoffroy's-cat (L. geoffroyi); 64% (95% CI: 50%, 68%) for jaguar (Panthera onca) and 48% (95% CI: 42%, 54%) for puma (Puma concolor). Multiple logistic regression was used to evaluate the association between the variables in the questionnaire and sero-positivity to T. gondii. We concluded that the independent risk factors for toxoplasmosis were: age >3 years (OR = 4.75 [2.75; 8.2]), eating meat previously frozen for a period <7 days (OR = 2.23 [1.24; 4.01]), and consumption of animals that were run-over or euthanized (OR = 1.64; [1.14; 2.37]). 相似文献
15.
16.
de Ramos Eduarda Kalena Kirsch Pazdiora Paulo Cesar Dallagnol Leandro José de Souza Mayara Rodrigues de Araujo Filho Jeronimo Vieira 《植物病害和植物保护杂志》2023,130(1):211-214
Journal of Plant Diseases and Protection - Tobacco (Nicotiana tabacum L.) is one of the major nonfood crops in the Southern of Brazil. During 2019/2020 and 2020/2021 crop seasons, Root Knot... 相似文献
17.
Tracey Jones Ruth Feber Gabriel Hemery Paul Cook Katy James Curt Lamberth Marian Dawkins 《Agricultural Systems》2007
The commercial, welfare and environmental impacts of rearing small colonies of free-range chickens in newly planted woodland at two sites in the UK, during the first 2 years of the enterprise, were investigated. Newly planted rather than established trees were used so that commercially viable species could be planted in a way that would suit the management of the chicken enterprise, and small colonies were used so that farmers wishing to diversify could buy into the system progressively. It was anticipated that marketing a high specification product would provide an immediate income, whilst waiting for the future investment in trees to grow. 相似文献
18.
Landscape Ecology - Pollinator declines and functional homogenization of farmland insect communities have been reported. Mass-flowering crops (MFC) can support pollinators by providing floral... 相似文献
19.
Sediment production from unpaved roads in a sub-tropical dry setting — Southwestern Puerto Rico 总被引:1,自引:0,他引:1
The threat imposed by increased sediment loading rates ranks among the most important stressors affecting coral reef ecosystems worldwide. This study represents an effort to quantify the effects of unpaved roads on erosion rates in a dry sub-tropical area of Puerto Rico and is intended to aid in developing scientifically-based erosion mitigation strategies. Hence, the specific objectives of this study were to: (1) measure sediment production rates from unpaved roads; (2) evaluate the effect of precipitation, rainfall erosivity, slope, plot length, and vegetation cover on sediment production rates; and (3) compare measured sediment production rates to published surface erosion data from roaded and natural sites in the Eastern Caribbean. Sediment production from nine abandoned road segments with varying slopes and plot lengths were measured with sediment traps in southwestern Puerto Rico from August 2003 to September 2005. 相似文献
20.