全文获取类型
收费全文 | 4086篇 |
免费 | 401篇 |
国内免费 | 16篇 |
专业分类
林业 | 350篇 |
农学 | 179篇 |
基础科学 | 35篇 |
854篇 | |
综合类 | 198篇 |
农作物 | 257篇 |
水产渔业 | 591篇 |
畜牧兽医 | 1595篇 |
园艺 | 100篇 |
植物保护 | 344篇 |
出版年
2024年 | 9篇 |
2023年 | 56篇 |
2022年 | 93篇 |
2021年 | 206篇 |
2020年 | 210篇 |
2019年 | 250篇 |
2018年 | 252篇 |
2017年 | 253篇 |
2016年 | 238篇 |
2015年 | 172篇 |
2014年 | 229篇 |
2013年 | 265篇 |
2012年 | 306篇 |
2011年 | 339篇 |
2010年 | 175篇 |
2009年 | 158篇 |
2008年 | 202篇 |
2007年 | 187篇 |
2006年 | 155篇 |
2005年 | 109篇 |
2004年 | 96篇 |
2003年 | 102篇 |
2002年 | 110篇 |
2001年 | 78篇 |
2000年 | 64篇 |
1999年 | 30篇 |
1998年 | 11篇 |
1997年 | 16篇 |
1996年 | 7篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 5篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1970年 | 2篇 |
1934年 | 2篇 |
1926年 | 1篇 |
1925年 | 1篇 |
排序方式: 共有4503条查询结果,搜索用时 15 毫秒
1.
Gustavo Pereira Valani Aline Fachin Martíni Laura Fernanda Simes da Silva Renata Cristina Bovi Miguel Cooper 《Soil Use and Management》2021,37(1):22-36
Integrated crop–livestock–forest is a promising strategy to improve soil quality. It comprises four different integrated farming systems: crop–livestock, crop–forest, forest–livestock and crop–livestock–forest. This work systematically reviewed studies about integrated crop–livestock–forest systems and soil quality. A total of 92 papers were retrieved from the Web of Science—Clarivate Analytics platform, and the following information was analysed: publication year, institution, region of the studied site, type of integrated system, soil type, tillage system, maximum soil depth and the soil quality indicators assessed. Most studies were published in the second half of the 2010s. Brazil is a prominent focus of research about soil quality and integrated crop–livestock–forest systems, with significant contribution from its central and southern regions. The Embrapa was the main publishing institution, present in over one‐third of the studies. Crop–livestock was the most common integrated system, Ferralsols was the most common soil group, and most of the studied soils were clayey. No tillage was the main tillage system. Most studies focused on the topsoil, assessing physical and/or chemical soil quality indicators. More emphasis on biological indicators of soil quality is required, as well as assessments integrating biological, physical and chemical indicators of soil quality. Future works should compare different integrated systems, including assessments deeper in the soil profile, especially in systems with the forest component, and also in sandy and silty soils. Soil quality indicators that have been rarely used should be further tested. Novel indicators should be added to better understand the promotion of soil quality by integrated crop–livestock–forest systems. 相似文献
2.
3.
4.
5.
Foot-and-mouth disease virus typing by complement fixation and enzyme-linked immunosorbent assay using monovalent and polyvalent antisera. 总被引:1,自引:0,他引:1
A Alonso M A Martins M da P Gomes R Allende M S S?ndahl 《Journal of veterinary diagnostic investigation》1992,4(3):249-253
An indirect "sandwich" enzyme-linked immunosorbent assay (ELISA) using polyvalent and monovalent antisera was compared with the 50% complement fixation (CF50) test for the detection of foot-and-mouth disease (FMD) O, A, and C virus types. ELISA was more sensitive than CF50 tests when polyvalent antisera were used for detecting the 3 types of virus in epithelial samples, whereas ELISA using monovalent antisera was the least sensitive technique. The ELISA performed with polyvalent antisera was 9 times more sensitive for detecting FMD virus than that with monovalent antisera. However, viral isolation in cell culture was the most sensitive detection system. The combined use of ELISA with polyvalent antisera and cell culture inoculations was the most effective procedure for identifying FMD virus in epithelial samples from the field. 相似文献
6.
V. Villar B. Colao I. Calles‐Venal J. G. Fernndez‐lvarez M. Fernndez‐Caso J. M. Villar 《Anatomia, histologia, embryologia》2005,34(Z1):54-54
Chondrocytes dedifferentiate to a fibroblast‐like phenotype on plastic surfaces. Dedifferentiation is reversible if these cells are then cultured embedded in gels as alginate, agarose or collagen. Chondrocytes cultured in suspension on a non‐adherent surface are also known to form aggregates of differentiated cells. The knowledge of chondrocyte behavior in culture is relevant for tissue engineering purposes. In this report we describe a simple method to culture differentiated or redifferentiated rabbit auricular chondrocytes on plastic surfaces with a stable phenotype. When chondrocyte aggregates formed in suspension are next seeded on plastic surfaces, most of them attach to the plastic as round or polygonal cells, and this morphological differentiation, confirmed by the presence of type II collagen, is stable for long culture periods. We also report that the addition of aggregates to monolayer cultures of dedifferentiated chondrocytes results in their redifferentiation, as is shown by their morphological changes and the synthesis of type II collagen. Therefore, this simple method can be useful for the study of chondrocyte behavior on plastic surfaces and for redifferentiating previously proliferated chondrocytes in tissue engineering techniques. Furthermore, these results demonstrate that, in addition to culture conditions such as cell isolation method or cell‐density, chondrocyte behavior on plastic depends on the presence or absence of aggregates resulting from the dissociation process. 相似文献
7.
P. López-Romero R. Rekaya M. J. Carabaño 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2004,121(1):14-25
Test‐day milk yields from Spanish Holstein cows were analysed with two random regression models based on Legendre polynomials under two different assumptions of heterogeneity of residual variance which aim to describe the variability of temporary measurement errors along days in milk with a reduced number of parameters, such as (i) the change point identification technique with two unknown change points and (ii) using 10 arbitrary intervals of residual variance. Both implementations were based on a previous study where the trajectory of the residual variance was estimated using 30 intervals. The change point technique has been previously implemented in the analysis of the heterogeneity of the residual variance in the Spanish population, yet no comparisons with other methods have been reported so far. This study aims to compare the change point technique identification versus the use of arbitrary intervals as two possible techniques to deal with the characterization of the residual variance in random regression test‐day models. The Bayes factor and the cross‐validation predictive densities were employed for the model assessment. The two model‐selecting tools revealed a strong consistency between them. Both specifications for the residual variance were close to each other. The 10 intervals modelling showed a slightly better performance probably because the change point function overestimates the residual variance values at the very early lactation. 相似文献
8.
Resistance to Botrytis cinerea in Solanum lycopersicoides is Dominant in Hybrids with Tomato, and Involves induced Hyphal Death 总被引:2,自引:0,他引:2
Rejane L. Guimarães Roger T. Chetelat Henrik U. Stotz 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(1):13-23
Botrytis cinerea causes gray mold disease and affects hundreds of plant species, including tomato (Lycopersicon esculentum). The wild nightshade, Solanum lycopersicoides, is cross compatible with tomato and is more resistant to B. cinerea, thus representing a potential source for crop improvement. Tests involving droplet inoculation of detached leaves and spray inoculation of entire seedlings demonstrated that resistance to B. cinerea varies among S. lycopersicoides accessions, with S. lycopersicoides LA2951 being the most resistant accession tested. Expression of resistance in the intergeneric hybrid (L. esculentum cv. 'VF36' × S. lycopersicoides LA2951) suggested that resistance is at least partially dominant in tomato. A green fluorescent protein-tagged B. cinerea strain was used for confocal microscopic comparison of infection in leaves of S. lycopersicoides and tomato. Even though S. lycopersicoides supported spore germination, there was evidence for hyphal lysis and death 3 days after inoculation, at a time when lesions were expanding on susceptible tomato plants. The reduced frequency of B. cinerea lesion spread on S. lycopersicoides explains why this fungus produced fewer spores in this wild nightshade than in tomato. 相似文献
9.
F.J. López-Escudero C. del Río J.M. Caballero M.A. Blanco-López 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(1):79-85
Resistance of 23 important olive cultivars to Verticillium dahliae has been evaluated in four experiments under controlled conditions. Nine-month-old nursery olive plants were inoculated with a cotton non-defoliating (ND) (V4) or a cotton defoliating (D) (V117) isolate of V. dahliae. Resistance was evaluated by assessing symptom severity using a 0–4 rating scale and estimating the area under disease progress curves. The percentage of plants killed and of those which recovered from the disease were used as additional parameters for including a particular cultivar into a defined category. Most of the evaluated cultivars were susceptible, although at different levels, to both isolates of V. dahliae. All cultivars were more susceptible to the D pathotype than to the ND one. A group of 11 cultivars, including several important Spanish cultivars, were susceptible or extremely susceptible to both pathotypes of V. dahliae. A second group showed differences of resistance depending on the pathotype used. They were susceptible or extremely susceptible to the D pathotype but resistant or moderately susceptible to the ND one. Finally, 'Frantoio', 'Oblonga' and 'Empeltre' were moderately susceptible to the D isolate of V. dahliae and resistant to the ND one. The resistance of 'Empeltre' was evident by the plant ability to recover from infection with either isolates. 'Empeltre' is considered to be a valuable cultivar for inclusion in breeding programmes for resistance to Verticillium wilt. 相似文献
10.
Morphofunctional description of mucous cells in the gills of the Arapaimidae Arapaima gigas (Cuvier) during its development
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)
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