全文获取类型
收费全文 | 11868篇 |
免费 | 859篇 |
专业分类
林业 | 1212篇 |
农学 | 448篇 |
基础科学 | 42篇 |
2713篇 | |
综合类 | 763篇 |
农作物 | 506篇 |
水产渔业 | 809篇 |
畜牧兽医 | 4838篇 |
园艺 | 288篇 |
植物保护 | 1108篇 |
出版年
2023年 | 105篇 |
2022年 | 135篇 |
2021年 | 245篇 |
2020年 | 258篇 |
2019年 | 177篇 |
2018年 | 579篇 |
2017年 | 547篇 |
2016年 | 491篇 |
2015年 | 389篇 |
2014年 | 446篇 |
2013年 | 672篇 |
2012年 | 945篇 |
2011年 | 847篇 |
2010年 | 464篇 |
2009年 | 355篇 |
2008年 | 729篇 |
2007年 | 692篇 |
2006年 | 545篇 |
2005年 | 581篇 |
2004年 | 531篇 |
2003年 | 493篇 |
2002年 | 392篇 |
2001年 | 286篇 |
2000年 | 248篇 |
1999年 | 220篇 |
1998年 | 67篇 |
1997年 | 56篇 |
1996年 | 41篇 |
1995年 | 69篇 |
1994年 | 37篇 |
1993年 | 36篇 |
1992年 | 84篇 |
1991年 | 67篇 |
1990年 | 67篇 |
1989年 | 59篇 |
1988年 | 57篇 |
1987年 | 52篇 |
1986年 | 49篇 |
1985年 | 48篇 |
1984年 | 50篇 |
1983年 | 40篇 |
1979年 | 38篇 |
1978年 | 24篇 |
1974年 | 29篇 |
1973年 | 23篇 |
1972年 | 26篇 |
1971年 | 25篇 |
1970年 | 27篇 |
1969年 | 26篇 |
1968年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
61.
62.
63.
Navid Adnani Emmanuel Vazquez-Rivera Srikar N. Adibhatla Gregory A. Ellis Doug R. Braun Tim S. Bugni 《Marine drugs》2015,13(10):6082-6098
With respect to bacterial natural products, a significant outcome of the genomic era was that the biosynthetic potential in many microorganisms surpassed the number of compounds isolated under standard laboratory growth conditions, particularly among certain members in the phylum Actinobacteria. Our group, as well as others, investigated interspecies interactions, via co-culture, as a technique to coax bacteria to produce novel natural products. While co-culture provides new opportunities, challenges exist and questions surrounding these methods remain unanswered. In marine bacteria, for example, how prevalent are interspecies interactions and how commonly do interactions result in novel natural products? In an attempt to begin to answer basic questions surrounding co-culture of marine microorganisms, we have tested both antibiotic activity-based and LC/MS-based methods to evaluate Micromonosporaceae secondary metabolite production in co-culture. Overall, our investigation of 65 Micromonosporaceae led to the identification of 12 Micromonosporaceae across three genera that produced unique metabolites in co-culture. Our results suggest that interspecies interactions were prevalent between marine Micromonosporaceae and marine mycolic acid-containing bacteria. Furthermore, our approach highlights a sensitive and rapid method for investigating interspecies interactions in search of novel antibiotics, secondary metabolites, and genes. 相似文献
64.
65.
66.
Physiological Response of Multiple Contrasting Rice (Oryza sativa L.) Cultivars to Suboptimal Temperatures
下载免费PDF全文
![点击此处可从《Journal of Agronomy and Crop Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M. M. Rachoski A. Vidal O. A. Ruiz A. B. Menéndez A. A. Rodríguez 《Journal of Agronomy and Crop Science》2015,201(2):117-127
The physiological response of multiple rice cultivars, eighteen initially and eight cultivars later on, to suboptimal temperatures (ST) conditions was investigated in laboratory and outdoor experimental conditions. Treatment with ST decreased growth in different extents according to the cultivar and affected the PSII performance, determined by chlorophyll fluorescence fast‐transient test, and stomatal conductance, regardless the experimental condition. Two groups of cultivars could be distinguished on the base of their growth and physiological parameters. The group of cultivars presenting higher growths displayed optimal JIP values, and higher instantaneous water use efficiency (WUEi), due to a lower Gs under ST, unlike cultivars showing lower growth values, which presented worse JIP values and could not adjust their Gs and hence their WUEi. In this work, we detected at least two cultivars with superior tolerance to ST than the cold tolerant referent Koshihikari. These cultivars could be used as parents or tolerance donors in breeding for new crop varieties. On other hand, positive and significant correlations between data obtained from laboratory and outdoor experiments suggest that laboratory measurements of most of the above mentioned parameters would be useful to predict the response of rice cultivars to ST outdoor. 相似文献
67.
Comparative Characterization of Enzymatic Digestion from Fish and Soybean Meal from Simulated Digestive Process of Pacific Bluefin Tuna,Thunnus orientalis
下载免费PDF全文
![点击此处可从《Journal of the World Aquaculture Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ariana I. Román‐Gavilanes Emmanuel Martínez‐Montaño María Teresa Viana 《Journal of the World Aquaculture Society》2015,46(4):409-420
The digestive process of the Pacific bluefin tuna (PBT), Thunnus orientalis, was simulated through two phases of in vitro digestion: acidic digestion with porcine pepsin, followed by alkaline digestion with pancreatic crude extract (PCE) obtained from the PBT to hydrolyze fish meal (FM) and soybean meal (SBM) as protein substrates. The crude protein from FM resulted in a lower degree of hydrolysis (73.3%) compared with SBM (79.2%). However, the resulting digested products showed that FM contained 35% more small peptides, with sizes <6.5 kDa than those from the starting material (>150 kDa). The SBM had an increase of only 1.3% in the similar peptide cut‐offs found after hydrolysis. These results suggested that FM appeared to be a better source of protein according to the amount of low‐molecular weight peptides. In addition, the proteolytic activity of PCE showed that 88.9% of its alkaline proteolytic activity corresponded to trypsin and 2.9% corresponded to chymotrypsin activity. The results shown here demonstrate that peptide sizes are important in identifying suitable protein sources for aquafeed production to reinforce the primary results obtained from the in vitro digestibility using the pH‐Stat system. These results also contribute to a better understanding of the digestibility process in aquatic organisms. 相似文献
68.
69.
İsmail Hakkı Nur William Pérez Horst Erich König 《Anatomia, histologia, embryologia》2021,50(3):658-667
This study aims to reveal the morphological properties of facial nerve and the middle ear in Van cats. Study material was composed of 6 female Van cats. Dissections were performed under a Zoom Stereo Microscope. There was no plexus buccalis in Van cats. The chorda tympani was observed to pass through an opening in the tympanic cavity, emerge through a small opening just behind the retroarticular process, and join the lingual nerve. A rounded anatomical formation with a size of 2.75 ± 0.3 mm was found to be located within the mastoid process of the temporal bone between the facial nerve and the auricular branch of the vagus nerve. The stapes nerve was not present. The geniculate ganglion was very prominent and about 1.00 mm high. The deep petrosal nerve was observed to emerge from the plexus tympanicus. The bulla tympanica was 18.96 ± 0.10 mm long, 13.03 ± 0.20 mm wide and 13.16 ± 0.20 mm high. After leaving the mandibular nerve, the n.tensoris tympani coursed caudally around the a.maxillaris, formed an ansa, entered the tympanic cavity through the canalis musculotubarius and reached an end in the m. tensor tympani. Due to the scarcity of studies on the middle ears of Van cats, it is thought that this study will fill a gap in the field of veterinary anatomy. 相似文献
70.