全文获取类型
收费全文 | 515篇 |
免费 | 29篇 |
专业分类
林业 | 50篇 |
农学 | 64篇 |
基础科学 | 8篇 |
102篇 | |
综合类 | 37篇 |
农作物 | 22篇 |
水产渔业 | 40篇 |
畜牧兽医 | 161篇 |
园艺 | 26篇 |
植物保护 | 34篇 |
出版年
2022年 | 9篇 |
2021年 | 11篇 |
2020年 | 16篇 |
2019年 | 9篇 |
2018年 | 27篇 |
2017年 | 22篇 |
2016年 | 16篇 |
2015年 | 21篇 |
2014年 | 23篇 |
2013年 | 46篇 |
2012年 | 26篇 |
2011年 | 28篇 |
2010年 | 26篇 |
2009年 | 25篇 |
2008年 | 24篇 |
2007年 | 16篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1983年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1970年 | 3篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1967年 | 8篇 |
1966年 | 6篇 |
排序方式: 共有544条查询结果,搜索用时 218 毫秒
41.
Thallium ion-induced carbonyl carbon chemical shifts were compared for all of the L-residue-peptide carbonyl carbons of the gramicidin A transmembrane channel. Molecular structures were deduced by using the argument that helically equivalent and equally proximal carbonyls would exhibit essentially equivalent ion-induced chemical shifts. The transmembrane channel was found to be a head-to-head dimer with the structure of a left-handed, single-stranded beta-helix. 相似文献
42.
Mangale VS Hirokawa KE Satyaki PR Gokulchandran N Chikbire S Subramanian L Shetty AS Martynoga B Paul J Mai MV Li Y Flanagan LA Tole S Monuki ES 《Science (New York, N.Y.)》2008,319(5861):304-309
The earliest step in creating the cerebral cortex is the specification of neuroepithelium to a cortical fate. Using mouse genetic mosaics and timed inactivations, we demonstrated that Lhx2 acts as a classic selector gene and essential intrinsic determinant of cortical identity. Lhx2 selector activity is restricted to an early critical period when stem cells comprise the cortical neuroepithelium, where it acts cell-autonomously to specify cortical identity and suppress alternative fates in a spatially dependent manner. Laterally, Lhx2 null cells adopt antihem identity, whereas medially they become cortical hem cells, which can induce and organize ectopic hippocampal fields. In addition to providing functional evidence for Lhx2 selector activity, these findings show that the cortical hem is a hippocampal organizer. 相似文献
43.
Niyas Z Variyar PS Gholap AS Sharma A 《Journal of agricultural and food chemistry》2003,51(22):6502-6504
The effect of gamma-irradiation on the lipid constituents of nutmeg (Myristica fragrans) was examined at radiation doses between 2.5 and 10 kGy. The fatty acid composition of the triacylglycerol, the major lipid component, was found to be made up of myristic (90%), palmitic (6%), lauric (3%), petroselinic (0.13%), and stearic acids (0.5%) as determined by gas chromatography-mass spectrometry. A dose-dependent decrease in the triacylglycerol content and a concomitant increase in free fatty acids characterized the lipid profile of the irradiated spice. This suggested a breakdown of acylglycerols during radiation processing, resulting in the release of free fatty acids. These changes were found to be significant at doses above 5 kGy. The impact of the above changes on the flavor of the spice is discussed. These studies suggest that radiation processing of nutmeg should be limited to a dose of 5 kGy. 相似文献
44.
Hiroshi FUJISE Masaru MURAKAMI Bhuminand DEVKOTA Ishwori Prasad DHAKAL Kumiko TAKEDA Hirofumi HANADA Hideo FUJITANI Masao SASAKI Kosaku KOBAYASHI 《Animal Science Journal》2003,74(1):1-5
Lulu is a dwarf cattle population bred in the Mustang district of western and central Nepal. This area is located around the habitat boundary between Bos taurus and Bos indicus. The peculiarities of Lulu are their small size (weight range in the adult female: 68–153 kg) and rearing in high mountain areas at 2800 m to 4000 m in altitude. There were 5770 head of Lulu cattle in the Mustang district in 1998, 4333 females and 1437 males. The morphological appearance of Lulu is Bos taurus. However, one of the five Lulu studied in Kagbeni, Mustang had a Bos indicus mitochondrial DNA type based on the D‐loop sequence, while the other four were Bos taurus. It is suggested that there are hybrids of Lulu with Bos indicus maternal lineage in a mostly taurine‐breed genetic background. Steps must be taken to preserve the unique Lulu. 相似文献
45.
46.
47.
P. S. John R. Prasad S. Singh Mercy George S. N. Sharma 《Journal of Agronomy and Crop Science》1989,163(3):177-180
A field experiment was conducted at the Division of Agronomy, Indian Agricultural Research Institute, New Delhi during 1983-84 and 1984-85 to study the effect of lentil residues on the yield and response of succeeding rice to nitrogen. Lentil residues benefitted the succeeding rice and gave longer and heavier panicles, more grains per panicle, higher 1000-grain weight and higher grain and straw yield of rice as compared to fallow. Rice responded well to applied nitrogen both in the absence and presence of lentil residues. The effect of lentil root residues and root residues plus incorporation of lentil straw was equivalent to 11 and 33 kg N ha−1 when 60 kg N ha−1 was applied to rice; the corresponding values being 54 and 60 kg N ha−1 when 120 kg N ha−1 was applied to rice. 相似文献
48.
49.
Physiological and biochemical effects of glyceryl guaiacolate-thiopentone sodium anaesthesia in buffalo calves 总被引:1,自引:0,他引:1
Glyceryl guaiacolate was used with thiopentone sodium for general anaesthesia in 10 clinically healthy male buffalo calves. When the animals were in the stage of surgical anaesthesia, there was marked hypotension and tachycardia along with a decrease in central venous pressure, tidal volume, partial pressure of oxygen in arterial blood and venous plasma potassium. Hyperglycaemia was another consistent feature. The changes in the acid base status were mild and inconsistent. 相似文献
50.