全文获取类型
收费全文 | 4870篇 |
免费 | 263篇 |
国内免费 | 28篇 |
学科分类
农业科学 | 5161篇 |
出版年
2024年 | 4篇 |
2023年 | 43篇 |
2022年 | 68篇 |
2021年 | 203篇 |
2020年 | 196篇 |
2019年 | 243篇 |
2018年 | 193篇 |
2017年 | 196篇 |
2016年 | 181篇 |
2015年 | 160篇 |
2014年 | 232篇 |
2013年 | 309篇 |
2012年 | 391篇 |
2011年 | 403篇 |
2010年 | 232篇 |
2009年 | 213篇 |
2008年 | 299篇 |
2007年 | 327篇 |
2006年 | 226篇 |
2005年 | 184篇 |
2004年 | 157篇 |
2003年 | 158篇 |
2002年 | 153篇 |
2001年 | 44篇 |
2000年 | 35篇 |
1999年 | 33篇 |
1998年 | 18篇 |
1997年 | 24篇 |
1996年 | 14篇 |
1995年 | 14篇 |
1994年 | 16篇 |
1993年 | 17篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1978年 | 4篇 |
1975年 | 4篇 |
1973年 | 5篇 |
1972年 | 6篇 |
1969年 | 3篇 |
1968年 | 6篇 |
1966年 | 5篇 |
排序方式: 共有5161条查询结果,搜索用时 390 毫秒
991.
Gisele J. dos Santos Jeana P. da Silva Alícia G. Hippólito Bárbara S. Ferro Elton Luís R. Oliveira Priscylla Tatiana C. G. Okamoto Maria Lucia G. Lourenço Vania Maria de Vasconcelos Machado Sheila C. Rahal Carlos R. Teixeira Alessandra Melchert 《Anatomia, histologia, embryologia》2020,49(2):299-306
This study aimed to assess radiographic and tomographic cardiac parameters, including width and length of the heart, and the ratio of heart width to coelom width of blue-fronted Amazon parrots (Amazona aestiva) with varying body condition scores. Thirty-five captive birds were included in the study and were allocated into one of three groups according to their respective body condition score: lean, ideal and obese. No differences were observed among the groups with regard to radiographic and tomographic measurements. Computed tomography enabled better identification of the structures of the cardiovascular system without interference from the overlying structures of the celomatic cavity observed in radiographic images. However, radiographic examinations should still be considered the standard screening method to identify cardiac alterations, such as increased or reduced organ dimensions. Standardizing the techniques and measurements performed in this study may serve as a basis for further research in the field. 相似文献
992.
Érika A. Praxedes Luiza B. de Queiroz Neta Alana A. Borges Maria B. Silva Maria V. O. Santos Leandro R. Ribeiro Herlon V. R. Silva Alexsandra F. Pereira 《Anatomia, histologia, embryologia》2020,49(1):121-129
Skin of mammals vulnerable to extinction, such as the jaguar, is used as a source of material in conservation strategies. The composition of skin is not uniform among species, and the ability to distinguish similarities in skin morphology in animal groups is fundamental in the application of skin tissue for use in biobanks. The aim of our study was to evaluate the structure, composition and capacity for culture of ear skin from the yellow and black jaguars. Both qualitative and quantitative methods were used, focusing on skin thickness, cell quantification and distribution, collagen density, proliferative activity and viability. Histomorphometrical study of the skin showed a total thickness of 273.2 and 274.6 µm for the yellow and black jaguars, respectively. Melanocytes and fibroblasts were, respectively, 9.7 and 23.0 for the yellow jaguar and 11.3 and 26.8 for the black jaguar. A collagen density of 67.0% and 49.0% was observed for yellow and black jaguars, respectively. Both animals presented a proliferative activity varying between 1.20 and 1.30. All tissues could promote cellular detachment, reaching subconfluence in 10–15 days. This kind of information from histomorphometrical features and cell cultures can be essential for a more targeted application of ear skin cryopreservation in this species, as such information will enable understanding the action of substances on tissues during the conservation process. 相似文献
993.
Francesco Abbate Maria Cristina Guerrera Maria Levanti Rosaria Laurà Germana Patrizia Germanà Giuseppe Montalbano Mauro Cavallaro Antonino Germanà 《Anatomia, histologia, embryologia》2020,49(6):686-694
The Atlantic salmon (Salmo salar) is a freshwater and marine fish of the family Salmonidae, widely farmed in aquaculture facilities in several countries. The salmon are carnivorous, but in aquaculture, alternative foods have been experienced. It is well known that feeding in captivity should cause adaptation and modifications of the morphological characteristics of the oral cavity, especially of tongue; therefore, the aim of this study was to investigate, by light, laser confocal and scanning electron microscopy, the morphological characteristics of the tongue dorsal surface, considering the importance of the correlations between feeding habits and the anatomy of the tongue. Scanning electron microscopy demonstrates the presence of caniniform teeth with oro-aboral orientation surrounded by numerous filiform papillae, single, fused or arranged in row. Oro-aborally, the papillae show an appearance like a rosette and they disappear at level of the root. Light and laser confocal microscopy demonstrates that the mucosa is covered by a non-keratinized stratified pavement epithelium with, in the deepest layer, the presence of a triangular structure whose apex is cranially directed and base facing aborally. In this structure, spindle-shaped cells are present, with a vimentin immunoreactivity, that for their characteristics could be adult mesenchymal stem cells. The obtained data could be useful not only for further studies on the nutrition, but it is interesting the detection of tissues typical of the embryo-fetal phase in the adult specimens tongue, thus giving a basis for studies of potential applications, if any, regarding cell therapies for different clinical indications. 相似文献
994.
995.
996.
Adrian Boswood Sonya G. Gordon Jens Häggström Martin Vanselow Gerhard Wess Rebecca L. Stepien Mark A. Oyama Bruce W. Keene John Bonagura Kristin A. MacDonald Mark Patteson Sarah Smith Philip R. Fox Karen Sanderson Richard Woolley Viktor Szatmári Pierre Menaut Whitney M. Church M. Lynne O'Sullivan Jean-Philippe Jaudon Jan-Gerd Kresken John Rush Kirstie A. Barrett Steven L. Rosenthal Ashley B. Saunders Ingrid Ljungvall Michael Deinert Eric Bomassi Amara H. Estrada Maria J. Fernandez Del Palacio N. Sydney Moise Jonathan A. Abbott Yoko Fujii Alan Spier Michael W. Luethy Roberto A. Santilli Masami Uechi Anna Tidholm Christoph Schummer Philip Watson 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2020,34(3):1108-1118
997.
森林经营方案编制及实施效果评价的微机辅助系统研究 总被引:2,自引:0,他引:2
本文以微型计算机为工具,选用dBASEⅢ关系型数据库和BASICA语言,研制了国营林场森林经营方案编制及实施效果评价的辅助系统,并以福建林学院莘口教学林场的森林资源数据试运行.经过运行表明,该系统结构合理、功能较全、性能可靠、科学实用. 相似文献
998.
Concetta Maria Messina Simona Manuguerra Rosaria Arena Giuseppe Renda Giovanna Ficano Mariano Randazzo Stefano Fricano Saloua Sadok Andrea Santulli 《Marine drugs》2021,19(4)
Non-edible parts of crustaceans could be a rich source of valuable bioactive compounds such as the carotenoid astaxanthin and peptides, which have well-recognized beneficial effects. These compounds are widely used in nutraceuticals and pharmaceuticals, and their market is rapidly growing, suggesting the need to find alternative sources. The aim of this work was to set up a pilot-scale protocol for the reutilization of by-products of processed shrimp, in order to address the utilization of this valuable biomass for nutraceutical and pharmaceuticals application, through the extraction of astaxanthin-enriched oil and antioxidant-rich protein hydrolysates. Astaxanthin (AST) was obtained using “green extraction methods,” such as using fish oil and different fatty acid ethyl esters as solvents and through supercritical fluid extraction (SFE), whereas bioactive peptides were obtained by protease hydrolysis. Both astaxanthin and bioactive peptides exhibited bioactive properties in vitro in cellular model systems, such as antioxidant and angiotensin I converting enzyme (ACE) inhibitory activities (IA). The results show higher astaxanthin yields in ethyl esters fatty acids (TFA) extraction and significant enrichment by short-path distillation (SPD) up to 114.80 ± 1.23 µg/mL. Peptide fractions of <3 kDa and 3–5 kDa exhibited greater antioxidant activity while the fraction 5–10 kDa exhibited a better ACE-IA. Lower-molecular-weight bioactive peptides and astaxanthin extracted using supercritical fluids showed protective effects against oxidative damage in 142BR and in 3T3 cell lines. These results suggest that “green” extraction methods allow us to obtain high-quality bioactive compounds from large volumes of shrimp waste for nutraceutical and pharmaceutical applications. 相似文献
999.
Fishery by-products are rich in biologically active substances and the use of green and efficient extraction methods to recover these high-added-value compounds is of particular importance. In this study, head, skin and viscera of rainbow trout and sole were used as the target matrices and accelerated solvent extraction (ASE) (45–55 °C, 15 min, pH 5.2–6.8, 103.4 bars) and pulsed electric fields (PEF) (1–3 kV/cm, 123–300 kJ/kg, 15–24 h) were applied as extraction technologies. The results showed that ASE and PEF significantly increased the protein extract efficiency of the fish by-products (p < 0.05) by up to 80%. SDS-PAGE results showed that ASE and PEF treatments changed the molecular size distribution of the protein in the extracts, which was specifically expressed as the change in the area or number of bands between 5 and 250 kDa. The antioxidant capacity of the extracts was evaluated by oxygen radical absorbance capacity (ORAC) and total antioxidant capacity (ABTS) assays. The results showed that both ASE and PEF treatments significantly increased the antioxidant capacity of rainbow trout and sole skin and head extracts (p < 0.05). ASE and PEF extraction processes can be used as new technologies to extract high-added-value compounds from fish by-products. 相似文献
1000.
Ultrasound-assisted water extraction was optimized to recover gelling biopolymers and antioxidant compounds from Mastocarpus stellatus. A set of experiments following a Box–Behnken design was proposed to study the influence of extraction time, solid liquid ratio, and ultrasound amplitude on the yield, sulfate content, and thermo-rheological properties (viscoelasticity and gelling temperature) of the carrageenan fraction, as well as the composition (protein and phenolic content) and antiradical capacity of the soluble extracts. Operating at 80 °C and 80 kHz, the models predicted a compromise optimum extraction conditions at ~35 min, solid liquid ratio of ~2 g/100 g, and ultrasound amplitude of ~79%. Under these conditions, 40.3% carrageenan yield was attained and this product presented 46% sulfate and good mechanical properties, a viscoelastic modulus of 741.4 Pa, with the lowest gelling temperatures of 39.4 °C. The carrageenans also exhibited promising antiproliferative properties on selected human cancer cellular lines, A-549, A-2780, HeLa 229, and HT-29 with EC50 under 51.9 μg/mL. The dried soluble extract contained 20.4 mg protein/g, 11.3 mg gallic acid eq/g, and the antiradical potency was equivalent to 59 mg Trolox/g. 相似文献