全文获取类型
收费全文 | 1050篇 |
免费 | 116篇 |
专业分类
林业 | 73篇 |
农学 | 60篇 |
基础科学 | 1篇 |
154篇 | |
综合类 | 49篇 |
农作物 | 74篇 |
水产渔业 | 131篇 |
畜牧兽医 | 538篇 |
园艺 | 21篇 |
植物保护 | 65篇 |
出版年
2024年 | 2篇 |
2023年 | 16篇 |
2022年 | 30篇 |
2021年 | 61篇 |
2020年 | 59篇 |
2019年 | 67篇 |
2018年 | 64篇 |
2017年 | 66篇 |
2016年 | 68篇 |
2015年 | 49篇 |
2014年 | 62篇 |
2013年 | 75篇 |
2012年 | 75篇 |
2011年 | 80篇 |
2010年 | 44篇 |
2009年 | 42篇 |
2008年 | 43篇 |
2007年 | 54篇 |
2006年 | 30篇 |
2005年 | 26篇 |
2004年 | 22篇 |
2003年 | 22篇 |
2002年 | 22篇 |
2001年 | 8篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有1166条查询结果,搜索用时 31 毫秒
991.
Rafael Torres de Souza Rodrigues Mario Luiz Chizzotti Daniel Ribeiro Menezes Fernando Santos Costa Carlos Wagner de Souza Wanderley Álvaro Santos Lisboa Neto 《Tropical animal health and production》2013,45(4):1031-1037
This experiment was conducted to evaluate the effect of different levels of substitution (0, 33.3, 66.7, and 100 %) of elephant grass by hay of mango tree pruning (HMTP) on intake and digestibility in cattle and on the in vitro gas production. Moreover, the effect of tannin in HMTP on the gas production and in vitro degradability of the dry matter was evaluated, using polyethylene glycol (PEG). The intake and digestibility were evaluated in a double 4?×?4 square Latin design, using eight Holstein intact bulls. To evaluate the gas production and degradability, in vitro semi-automated gas production technique was used. The substitution of elephant grass by HMTP decreased the intake (P?<?0.05) and the digestibility (P?<?0.05) of the nutrients and also the gas production (P?<?0.05). Furthermore, the utilization of PEG as a tannin-complexing agent increased the gas production and degradability of the HMTP (P?<?0.05). It was concluded that the high cell wall lignification and the presence of tannin limit the use of HMTP as the only source of roughage in cattle diets. 相似文献
992.
993.
L. N. S. Santana L. V. M. Barbosa F. B. Teixeira A. M. P. Costa L. M. P. Fernandes R. R. Lima 《Anatomia, histologia, embryologia》2013,42(6):410-414
The aim of this study was to describe the dentine morphology of sloths (Bradypus tridactylus). The sloth teeth were removed and prepared for light microscopy (LM) and scanning electron microscopy analyses (SEM). LM revealed two patterns of tubular dentins: an outer with dentinary tubules over the all tooth length and one in the inner part with larger diameter and more spaced tubules, when compared to those present in the outer dentine. These findings were confirmed by SEM, which revealed a tubular pattern in the outer dentine like in humans. The inner dentine displayed pared grouped tubules that were characterized as vascular channels. It can be concluded that this sloth species present two types of dentins: an inner dentin (ortodentin) and an outer dentin characterized as a vascular dentin. This suggests a partial evolutive/adaptive process of this dental tissue, as compared to other mammalian species. 相似文献
994.
Here we summarize the current knowledge on the transfer and accumulation of harmful algal bloom (HAB)-related toxins in cephalopods (octopods, cuttlefishes and squids). These mollusks have been reported to accumulate several HAB-toxins, namely domoic acid (DA, and its isomers), saxitoxin (and its derivatives) and palytoxin (and palytoxin-like compounds) and, therefore, act as HAB-toxin vectors in marine food webs. Coastal octopods and cuttlefishes store considerably high levels of DA (amnesic shellfish toxin) in several tissues, but mainly in the digestive gland (DG)—the primary site of digestive absorption and intracellular digestion. Studies on the sub-cellular partitioning of DA in the soluble and insoluble fractions showed that nearly all DA (92.6%) is found in the cytosol. This favors the trophic transfer of the toxins since cytosolic substances can be absorbed by predators with greater efficiency. The available information on the accumulation and tissue distribution of DA in squids (e.g., in stranded Humboldt squids, Dosidicus gigas) is scarcer than in other cephalopod groups. Regarding paralytic shellfish toxins (PSTs), these organisms accumulate them at the greatest extent in DG >> kidneys > stomach > branchial hearts > posterior salivary glands > gills. Palytoxins are among the most toxic molecules identified and stranded octopods revealed high contamination levels, with ovatoxin (a palytoxin analogue) reaching 971 μg kg−1 and palytoxin reaching 115 μg kg−1 (the regulatory limit for PlTXs is 30 μg kg−1 in shellfish). Although the impacts of HAB-toxins in cephalopod physiology are not as well understood as in fish species, similar effects are expected since they possess a complex nervous system and highly developed brain comparable to that of the vertebrates. Compared to bivalves, cephalopods represent a lower risk of shellfish poisoning in humans, since they are usually consumed eviscerated, with exception of traditional dishes from the Mediterranean area. 相似文献
995.
Phylogeny is an evolutionary reconstruction of the past relationships of DNA or protein sequences and it can further be used as a tool to assess population structuring, genetic diversity and biogeographic patterns. In the microbial world, the concept that everything is everywhere is widely accepted. However, it is much debated whether microbes are easily dispersed globally or whether they, like many macro-organisms, have historical biogeographies. Biogeography can be defined as the science that documents the spatial and temporal distribution of a given taxa in the environment at local, regional and continental scales. Speciation, extinction and dispersal are proposed to explain the generation of biogeographic patterns. Cyanobacteria are a diverse group of microorganisms that inhabit a wide range of ecological niches and are well known for their toxic secondary metabolite production. Knowledge of the evolution and dispersal of these microorganisms is still limited, and further research to understand such topics is imperative. Here, we provide a compilation of the most relevant information regarding these issues to better understand the present state of the art as a platform for future studies, and we highlight examples of both phylogenetic and biogeographic studies in non-symbiotic cyanobacteria and cyanotoxins. 相似文献
996.
RP Roberto da Costa H Carvalho R Agrícola J Alpoim-Moreira C Martins G Ferreira-Dias 《Reproduction in domestic animals》2003,38(6):464-469
The purpose of this study was to evaluate different parameters of the immune status in the mare, during the follicular and the luteal phases of the oestrous cycle, in two consecutive years. Functional competence of peripheral blood neutrophils, such as chemotaxis, phagocytosis and oxidative burst was assessed under physiological cyclic conditions (Exp. I). In the second year of this study (Exp. II), besides peripheral blood neutrophil phagocytosis and oxidative burst analysis, circulating lymphocyte subsets were also characterized. The reproductive status in a total of 17 adult cycling mares was evaluated by ultrasonography and further confirmed by plasma progesterone levels. Chemotaxis tests were performed using porous membranes inserted in transwell chambers. Lipopolysaccharide (LPS) from Escherichia coli and N‐formyl‐Met‐Leu‐Phe (fMLP) were used as chemoattractants. Measurement of phagocytosis and oxidative burst in blood neutrophils were assessed by flow cytometry using commercially available kits. Quantification of T‐lymphocyte subsets was assessed by indirect immunofluorescence staining after incubation with monoclonal antibodies specific for CD2, CD3, CD4 and CD8 cell markers by flow cytometry. Natural killer cells and B cells were estimated mathematically. No significant difference was found in migration, phagocytosis and oxidative burst at either phase of the oestrous cycle. Statistical analysis of total white blood cell counts also showed no significant difference between either phase of the oestrous cycle, although there was a tendency for blood neutrophils to increase in number under the progesterone influence (p = 0.09). Lymphocytic subpopulations did not differ throughout the oestrous cycle. Overall, our results suggest that luteal and follicular phases in cycling mares may not influence the immune status of the mare. 相似文献
997.
Histology and Immunohistochemistry of the Cardiac Ventricular Structure in the Green Turtle (Chelonia mydas)
下载免费PDF全文
![点击此处可从《Anatomia, histologia, embryologia》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J. K. F. S. Braz M. L. Freitas M. S. Magalhães M. F. Oliveira M. S. M. O. Costa N. S. Resende N. K. Clebis N. B. Silva C. E. B. Moura 《Anatomia, histologia, embryologia》2016,45(4):277-284
This study describes the implications of cardiac ventricular microscopy in Chelonia mydas relating to its ability to dive. For this work, 11 specimens of the marine turtle species C. mydas found dead on the coast of Rio Grande do Norte (Northeast Brazil) were used. After necropsy, fragments of the cardiac ventricular wall were fixed in 10% buffered formaldehyde solution for 24 h and then subjected to routine processing for light and scanning electron microscopy (SEM). The ventricle in this species is formed by the epicardium, myocardium and endocardium. The subepicardial layer consists of highly vascularised connective tissue that emits septa to reinforce the myocardium surface. There is an abundant and diffuse subepicardial nerve plexus shown by immunostaining technique. The thickness of the spongy myocardium and the nature of its trabeculae varied between the heart chambers. The endocardium shows no characteristic elements of the heart conduction system. The valves have a hyaline cartilage skeleton, coated by dense irregular connective tissues characterised by elastic fibres. These findings in the green turtle ventricular microscopy are related to hypoxia resistance during diving. 相似文献
998.
999.
Santos-Doni Thaís Rabelo Viol Milena Araúz Lima Valéria Marçal Felix Oliveira Bruno César Miranda Matos Lucas Vinicius Shigaki da Costa Alvimar José Gomes Jancarlo Ferreira Bresciani Katia Denise Saraiva 《Veterinary research communications》2022,46(1):109-120
Veterinary Research Communications - The aim of this study was evaluating the association and correlation between the diagnostics tests used for Leishmania spp. detection in dogs and ticks. We... 相似文献
1000.
Ramírez Olga Lucia Herrán Santos Huarrisson Azevedo Paulino Patrícia Gonzaga van der Meer Carolina Soares Bautista José Luis Rodríguez Delgado Ingrid Lorena Jaramillo Obando Juliana González Garcia Rene Ramirez da Costa Angelo Isabele 《Veterinary research communications》2022,46(1):189-201
Veterinary Research Communications - A cross-sectional study was conducted in Colombia to recover Brucella spp. DNA from bovine whole-blood samples through probe-based real-time PCR (qPCR). By an... 相似文献