全文获取类型
收费全文 | 6794篇 |
免费 | 373篇 |
国内免费 | 3篇 |
专业分类
林业 | 161篇 |
农学 | 171篇 |
基础科学 | 36篇 |
682篇 | |
综合类 | 1300篇 |
农作物 | 263篇 |
水产渔业 | 266篇 |
畜牧兽医 | 3827篇 |
园艺 | 108篇 |
植物保护 | 356篇 |
出版年
2021年 | 71篇 |
2020年 | 86篇 |
2019年 | 101篇 |
2018年 | 91篇 |
2017年 | 98篇 |
2016年 | 97篇 |
2015年 | 87篇 |
2014年 | 104篇 |
2013年 | 293篇 |
2012年 | 246篇 |
2011年 | 269篇 |
2010年 | 133篇 |
2009年 | 136篇 |
2008年 | 294篇 |
2007年 | 304篇 |
2006年 | 299篇 |
2005年 | 254篇 |
2004年 | 227篇 |
2003年 | 234篇 |
2002年 | 265篇 |
2001年 | 194篇 |
2000年 | 172篇 |
1999年 | 158篇 |
1998年 | 71篇 |
1997年 | 64篇 |
1996年 | 67篇 |
1995年 | 84篇 |
1992年 | 121篇 |
1991年 | 136篇 |
1990年 | 122篇 |
1989年 | 110篇 |
1988年 | 107篇 |
1987年 | 114篇 |
1986年 | 113篇 |
1985年 | 128篇 |
1984年 | 90篇 |
1983年 | 87篇 |
1982年 | 57篇 |
1981年 | 48篇 |
1979年 | 55篇 |
1978年 | 49篇 |
1977年 | 52篇 |
1976年 | 52篇 |
1975年 | 45篇 |
1974年 | 60篇 |
1973年 | 74篇 |
1972年 | 64篇 |
1971年 | 67篇 |
1970年 | 59篇 |
1969年 | 53篇 |
排序方式: 共有7170条查询结果,搜索用时 974 毫秒
71.
Marcelo Gómez DVM Larry Freeman DVM MS Jeryl Jones DVM PhD Otto Lanz DVM Pam Arnold 《Veterinary radiology & ultrasound》2004,45(1):29-37
Computed tomographic (CT) venography of the cervical vertebral canal was performed in six, clinically normal, adult mixed-breed dogs from 14 to 23 kg. After dogs were euthanized and saline perfused, a gelatin and iothalamate mixture was injected into the right external jugular vein. Contiguous, 4-mm-thick CT images were obtained with dogs in sternal recumbency. Dogs were kept in the same position as for the CT scan and frozen to approximately -8 degrees C. All post-contrast CT images were analyzed using similar bone window and level settings. Additional multiplanar reformatted dorsal images were obtained in all dogs. The frozen cadavers were sectioned through the cervical region extending from the occiput to T1 at approximately 8-mm intervals. The frozen sections were then compared with the CT images. The CT appearance of the normal cervical vertebral venous system was described and illustrated. Components such as the internal vertebral venous plexus, interarcuate veins, intervertebral veins, and vertebral veins were clearly identified on the CT images. 相似文献
72.
Aleksa Obradovic Athanassios Mavridis Klaus Rudolph Jaap D. Janse Momcilo Arsenijevic Jeffrey B. Jones Gerald V. Minsavage Jaw-Fen Wang 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(3):285-292
During the last two decades bacterial strains associated with necrotic leaf spots of pepper and tomato fruit spots were collected in Serbia. Twenty-eight strains isolated from pepper and six from tomato were characterized. A study of their physiological and pathological characteristics, and fatty acid composition analysis revealed that all of the strains belong to Xanthomonas campestris pv. vesicatoria. Being non-amylolytic and non-pectolytic, pathogenic on pepper but not on tomato, containing lower amounts of fatty acid 15 : 0 ante–iso, the pepper strains were designated as members of the A group of X. campestris pv. vesicatoria. However, the tomato strains hydrolyzed starch and pectate, caused compatible reactions on tomato but not on pepper, had higher percent of 15 : 0 ante–iso fatty acid, and were classified into B phenotypic group and identified as X. vesicatoria. PCR primers were developed which amplified conserved DNA regions related to the hrp genes of different strains of X. campestris pv. vesicatoria associated with pepper and tomato. Restriction analysis of the PCR product resulted in different patterns and enabled grouping of the strains into four groups. When xanthomonads isolated from pepper and tomato in Serbia were analyzed, they clustered into two groups corresponding to the grouping based on their physiological and pathological characteristics. According to the reaction of pepper and tomato differential varieties, the strains from pepper belong to races P7 and P8 and tomato strains belong to the race T2. All strains were sensitive to copper and streptomycin. Advantages and disadvantages of various bacterial spot management practices are discussed. 相似文献
73.
74.
Laryngeal mask airway and transient hypercapnic hyperpnea for video‐endoscopic assessment of unilateral laryngeal paralysis in dogs
下载免费PDF全文
![点击此处可从《Veterinary surgery : VS》网站下载免费的PDF全文](/ch/ext_images/free.gif)
75.
Incidence and risk factors of surgical site infection and septic arthritis after elective arthroscopy in horses
下载免费PDF全文
![点击此处可从《Veterinary surgery : VS》网站下载免费的PDF全文](/ch/ext_images/free.gif)
76.
Removal of hemangiosarcoma cells from canine blood with a cell salvage system and leukocyte reduction filter
下载免费PDF全文
![点击此处可从《Veterinary surgery : VS》网站下载免费的PDF全文](/ch/ext_images/free.gif)
77.
78.
Distribution,characteristics and condition of Arctic charr (Salvelinus alpinus) spawning grounds in a differentially eutrophicated twin‐basin lake
下载免费PDF全文
![点击此处可从《Ecology of Freshwater Fish》网站下载免费的PDF全文](/ch/ext_images/free.gif)
79.
80.
Limited effects of land use on soil dissolved organic matter chemistry as assessed by excitation–emission fluorescence spectroscopy and molecular weight fractionation
下载免费PDF全文
![点击此处可从《Soil Use and Management》网站下载免费的PDF全文](/ch/ext_images/free.gif)
P. Roberts J. M. Gibbons P. W. Hill D. L. Jones M. Farrell 《Soil Use and Management》2016,32(4):662-665
Dissolved organic matter (DOM) in soil solution represents a complex mixture of organic molecules and plays a central role in carbon and nitrogen cycling in plant–microbial–soil systems. We tested whether excitation–emission matrix (EEM) fluorescence spectroscopy can be used to characterize DOM and support previous findings that the majority of DOM is of high molecular weight (MW). EEM fluorescence spectroscopy was used in conjunction with MW fractionation to characterize DOM in soil solution from a grassland soil land management gradient in North Wales, UK. Data analysis suggested that three distinct fluorescence components could be separated and identified from the EEM data. These components were identified as being of humic‐like or fulvic‐like origin. Contrary to expectations, the majority of the fluorescence signal occurred in the small MW (<1 kDa) fraction, although differences between soils from the differently managed grasslands were more apparent in larger MW fractions. We conclude that following further characterization of the chemical composition of the fluorophores, EEM has potential as a sensitive technique for characterizing the small MW phenolic fraction of DOM in soils. 相似文献