全文获取类型
收费全文 | 6730篇 |
免费 | 458篇 |
国内免费 | 15篇 |
专业分类
林业 | 483篇 |
农学 | 237篇 |
基础科学 | 37篇 |
1171篇 | |
综合类 | 652篇 |
农作物 | 384篇 |
水产渔业 | 767篇 |
畜牧兽医 | 2753篇 |
园艺 | 178篇 |
植物保护 | 541篇 |
出版年
2023年 | 59篇 |
2022年 | 114篇 |
2021年 | 232篇 |
2020年 | 261篇 |
2019年 | 291篇 |
2018年 | 276篇 |
2017年 | 281篇 |
2016年 | 259篇 |
2015年 | 175篇 |
2014年 | 255篇 |
2013年 | 348篇 |
2012年 | 391篇 |
2011年 | 492篇 |
2010年 | 242篇 |
2009年 | 227篇 |
2008年 | 350篇 |
2007年 | 358篇 |
2006年 | 328篇 |
2005年 | 279篇 |
2004年 | 282篇 |
2003年 | 276篇 |
2002年 | 275篇 |
2001年 | 104篇 |
2000年 | 93篇 |
1999年 | 69篇 |
1998年 | 69篇 |
1997年 | 58篇 |
1996年 | 60篇 |
1995年 | 47篇 |
1994年 | 45篇 |
1993年 | 32篇 |
1992年 | 41篇 |
1991年 | 35篇 |
1990年 | 38篇 |
1989年 | 39篇 |
1988年 | 28篇 |
1987年 | 23篇 |
1986年 | 21篇 |
1985年 | 30篇 |
1984年 | 25篇 |
1983年 | 31篇 |
1982年 | 25篇 |
1981年 | 26篇 |
1980年 | 25篇 |
1979年 | 11篇 |
1978年 | 19篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1975年 | 18篇 |
1974年 | 16篇 |
排序方式: 共有7203条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
Morphofunctional description of mucous cells in the gills of the Arapaimidae Arapaima gigas (Cuvier) during its development 下载免费PDF全文
C. A. Ramos O. T. F. da Costa W. L. P. Duncan M. N. Fernandes 《Anatomia, histologia, embryologia》2018,47(4):330-337
The gill structure of the Amazonian fish Arapaima gigas (Cuvier 1829) shows ontogenetic changes during development, particularly due the transition from the aquatic to the obligatory air breathing mode of respiration. However, three main cell types can be found in the gills: mitochondrial rich cells, pavement cells and mucous cells (MCs). The MCs are involved in the secretory pathway. The functions of the secreted molecules include mechanical protection of epithelia, protection against parasites and bacterial infection, and role on ion regulation. In this study, we analysed mucous cell location and mucous cell type, based on pH, during the development of A. gigas. Using samples obtained from the environment, gills were collected and fixed in buffered solution. Histological techniques for the identification of MCs were performed Alcian Blue (AB) and periodic acid‐Schiff (PAS). The results showed the presence of PAS+ and AB+ cells in the whole filament in all examined fish. In animals less than 50 g, few MCs were present, and no differences were observed in AB+ and PAS+ cells. In animals weighing close to 500 g, more PAS+ cells than AB+ cells were observed, and in animals that weighed more than 1,000 g, more AB+ cells than PAS+ cells were observed. These observations may be a result of the ontogenetic changes in the gill epithelia, which can change the osmorespiratory compromise in ion regulation functions as well the glycosaminoglycans secreted by PAS cells, which in large animals can play a role in the protection against parasites and bacterial infection. 相似文献
25.
26.
de Carvalho Menezes de Almeida Sheylla Foligno Souza-Fabjan Joanna Maria Gonçalves Balaro Mario Felipe Alvarez Bragança Gláucia Mota Pinto Pedro Henrique Nicolau de Almeida José Gabriel Moura Ana Beatriz Bossois da Fonseca Jeferson Ferreira Brandão Felipe Zandonadi 《Tropical animal health and production》2018,50(2):427-432
Tropical Animal Health and Production - This study evaluated the effect of two doses of prostaglandin at different intervals on reproductive parameters of crossbred ewes. In Experiment 1, 30 ewes... 相似文献
27.
Silva D. C. Queiroz P. J. B. Caetano D. B. S Assis B. M. Rabelo R. E. Silva L. A. F. 《Tropical animal health and production》2018,50(7):1631-1636
Tropical Animal Health and Production - We aimed to follow the epidemiologic evolution of bovine digital dermatitis (BDD) and other podal diseases grouped in a dairy farm in Central Brazil between... 相似文献
28.
Veridiane da Rosa Gomes Paula Costa Ariza Naida Cristina Borges Francisco Jorge SchulzJr. Maria Clorinda Soares Fioravanti 《Veterinary research communications》2018,42(1):87-94
Urinary tract diseases are among the main reasons for consultation in veterinary clinics and hospitals. It affects animals of any age, breed and gender. Among the diseases that affect this system, urolithiasis is the second largest cause of clinical signs compatible with feline urinary tract disease. The term urolithiasis refers to the presence of uroliths in any region of the urinary tract, but it is more commonly seen in the bladder and urethra. Uroliths are classified based on the type of mineral present in their composition, therefore, quantitative and qualitative analyzes are important for a better therapeutic approach. The animals may suffer from the disease and be asymptomatic, or show nonspecific clinical signs, making the diagnosis difficult. The disease should not be seen as a single problem, but as a consequence of various disorders. As dietary, metabolic, genetic and infectious causes, as well as factors that potentiate the chance of development of uroliths such as breed, age, sex, age range, obesity, sedentary lifestyle, geographic region and climate. Thus, the knowledge of the factors that influence the formation of uroliths, as well as the understanding of the pathophysiology, are key elements for better alternatives of therapy and prevention. The recognition of these factors helps to identify susceptible populations, minimizing exposure and increasing the protection factors, which facilitates the diagnosis and treatment of patients with urolithiasis. The objective of this paper is to present the main risk factors involved in the formation of urinary lithiasis in felines. 相似文献
29.
Renata Pereira da Silva-Marques Joanis Tilemahos Zervoudakis Nelcino Francisco De Paula Luciana Keiko Hatamoto-Zervoudakis Pedro Ivo José Lopes da Rosa e Silva Núbia Bezerra do Nascimento Matos 《Tropical animal health and production》2018,50(3):495-501
Two experiments were conducted to evaluate reduced supplementation frequencies for grazing beef cattle in rainy season. In experiment 1, evaluating the nutritional parameters, four rumen-cannulated Nellore bulls (BW = 410 kg) were used. In experiment 2, evaluating animal performance, 48 Nellore bulls (BW = 358 kg) were used. The treatments were as follows: mineral supplement (MS) alone and MS plus protein-energy supplement provided 3×, 5× and 7×/week. Supplementation frequency did not affect (P > 0.05) intake and digestibility. Average daily gain was greater (P < 0.001) to supplementation compared with MS. The supplementation 5×/week resulted in greater weight gain per hectare (9.24) and higher economic returns during the study period (1.64%) compared to other supplementations. Supplementation 5×/week increased animal performance and positively influenced economic returns. 相似文献
30.
Paula de Aguiar Silva Gleidson Giordano Pinto de Carvalho Aureliano José Vieira Pires Stefanie Alvarenga Santos Douglas dos Santos Pina Robério Rodrigues Silva Carlindo Santos Rodrigues Luis Henrique Almeida de Matos Carlos Emanuel Eiras Daiane Novais-Eiras Wilson Souza Nunes 《Tropical animal health and production》2018,50(4):721-726
In this study, we evaluated the effects of including cassava wastewater in the diet on the feeding behavior of feedlot lambs in 35 male uncastrated Santa Inês × Dorper crossbred lambs at an approximate age of 3 months, with an average live weight of 20.0?±?3.4 kg. Diets were formulated with hay of cassava shoots (roughage) and a concentrate based on corn and soybean, with a roughage:concentrate ratio of 50:50, plus inclusion of cassava wastewater at the levels of 0, 12, 24, 36, or 48 g/kg of the total diet. Feeding behavior was evaluated between the 46th and 52nd days of the experiment. Increasing cassava wastewater levels in the diet reduced (P?<?0.05) the intakes (kg/day) of dry matter and neutral detergent fiber as well as the efficiency of rumination (g/cud and g/h) of dry matter and neutral detergent fiber. The other behavioral parameters were not affected by wastewater inclusion in the diet. Therefore, the inclusion of up to 48 g/kg of cassava wastewater on fresh matter of diets is not recommended for feedlot lambs. 相似文献