全文获取类型
收费全文 | 489篇 |
免费 | 33篇 |
国内免费 | 4篇 |
专业分类
林业 | 31篇 |
农学 | 15篇 |
84篇 | |
综合类 | 50篇 |
农作物 | 24篇 |
水产渔业 | 36篇 |
畜牧兽医 | 249篇 |
园艺 | 9篇 |
植物保护 | 28篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 13篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 35篇 |
2012年 | 31篇 |
2011年 | 29篇 |
2010年 | 18篇 |
2009年 | 17篇 |
2008年 | 18篇 |
2007年 | 23篇 |
2006年 | 17篇 |
2005年 | 19篇 |
2004年 | 25篇 |
2003年 | 27篇 |
2002年 | 30篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1996年 | 8篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 15篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1971年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1946年 | 2篇 |
1942年 | 1篇 |
排序方式: 共有526条查询结果,搜索用时 10 毫秒
141.
Olivia Saunders Joe Harrison Ann Marie Fortuna Elizabeth Whitefield Andy Bary 《Water, air, and soil pollution》2012,223(3):1055-1063
Animal wastes are commonly used in a sustainable manner to fertilize crops. However, manures contain numerous pathogenic bacteria
that can impact animal and human health. Treatment of animal waste by anaerobic digestion has the potential to reduce pathogen
loading to land. This study was conducted to determine the fate of bacteria applied in raw and anaerobically digested dairy
slurries that were broadcast and subsurface applied in a field of forage grasses. Digested slurry had significantly fewer
indicator bacteria, Escherichia coli and fecal coliform at time of application. Anaerobic digestion did not increase the survivability of indicator bacteria.
Waste treatment and application method did not affect the rate of bacteria die-off. There were fewer E. coli and fecal coliform at the end of each trial in the soils that received digested slurry. Anaerobic digestion of dairy waste
has the potential to reduce pathogenic bacteria loading to cropland. 相似文献
142.
Singer JB Hill AE Burrage LC Olszens KR Song J Justice M O'Brien WE Conti DV Witte JS Lander ES Nadeau JH 《Science (New York, N.Y.)》2004,304(5669):445-448
Chromosome substitution strains (CSSs) have been proposed as a simple and powerful way to identify quantitative trait loci (QTLs) affecting developmental, physiological, and behavioral processes. Here, we report the construction of a complete CSS panel for a vertebrate species. The CSS panel consists of 22 mouse strains, each of which carries a single chromosome substituted from a donor strain (A/J) onto a common host background (C57BL/6J). A survey of 53 traits revealed evidence for 150 QTLs affecting serum levels of sterols and amino acids, diet-induced obesity, and anxiety. These results demonstrate that CSSs greatly facilitate the detection and identification of genes that control the wide diversity of naturally occurring phenotypic variation in the A/J and C57BL/6J inbred strains. 相似文献
143.
We have discovered nonvolcanic tremor activity (i.e., long-duration seismic signals with no clear P or S waves) within a transform plate boundary zone along the San Andreas Fault near Cholame, California, the inferred epicentral region of the 1857 Fort Tejon earthquake (moment magnitude approximately 7.8). The tremors occur between 20 to 40 kilometers' depth, below the seismogenic zone (the upper approximately 15 kilometers of Earth's crust where earthquakes occur), and their activity rates may correlate with variations in local earthquake activity. 相似文献
144.
145.
146.
An acidic pectin methylesterase (PME) is responsible for the gelation of water extract from jelly fig (Ficus awkeotasang) achenes. A new, fast and efficient, method has been developed to purify this acidic PME. The method includes preparing jelly curd by traditional hand washing, extracting proteins from the curd, and separating PME by anion-exchanger. The purified PME exists as a monomer of 38 kDa determined by gel filtration, and exerts enzymatic activity over a broad pH range, particularly in acidic environments where most known PME enzymes from various species are inactivated. Chemical staining and enzymatic cleavage suggest that the jelly fig PME is an N-linked glycoprotein. Fluorophore-assisted carbohydrate electrophoresis reveals that the polysaccharide of this glycoprotein putatively consists of 22 hexoses including 16 mannose, 4 N-acetylglucosamine, and 2 galactose residues. 相似文献
147.
Antioxidant activities and antitumor screening of extracts from cranberry fruit (Vaccinium macrocarpon) 总被引:6,自引:0,他引:6
Yan X Murphy BT Hammond GB Vinson JA Neto CC 《Journal of agricultural and food chemistry》2002,50(21):5844-5849
Polyphenolic compounds in cranberries have been investigated to determine their role in protection against cardiovascular disease and some cancers. Extracts of whole fruit were assayed for radical-scavenging activity and tumor growth inhibition using seven tumor cell lines. Selective inhibition of K562 and HT-29 cells was observed from a methanolic extract in the range of 16-125 microg/mL. Radical-scavenging activity was greatest in an extract composed primarily of flavonol glycosides. Seven flavonol glycosides were isolated and purified from whole fruit for further evaluation; the anthocyanin cyanidin 3-galactoside was also purified for comparison with the flavonoids. Three flavonol monoglycosides were newly identified by (13)C NMR as myricetin 3-alpha-arabinofuranoside, quercetin 3-xyloside, and 3-methoxyquercetin 3-beta-galactoside (isorhamnetin); the other four isolated were the previously identified myricetin 3-beta-galactoside, quercetin 3-beta-galactoside, quercetin 3-alpha-arabinofuranoside, and quercetin 3-alpha-rhamnopyranoside. These compounds were evaluated for 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity and ability to inhibit low-density lipoprotein oxidation in vitro. Most of the flavonol glycosides showed antioxidant activity comparable or superior to that of vitamin E; cyanidin 3-galactoside showed activity superior to that of the flavonoids as well as vitamin E or Trolox in both antioxidant assays. 相似文献
148.
The sequence of the human genome 总被引:8,自引:0,他引:8
Venter JC Adams MD Myers EW Li PW Mural RJ Sutton GG Smith HO Yandell M Evans CA Holt RA Gocayne JD Amanatides P Ballew RM Huson DH Wortman JR Zhang Q Kodira CD Zheng XH Chen L Skupski M Subramanian G Thomas PD Zhang J Gabor Miklos GL Nelson C Broder S Clark AG Nadeau J McKusick VA Zinder N Levine AJ Roberts RJ Simon M Slayman C Hunkapiller M Bolanos R Delcher A Dew I Fasulo D Flanigan M Florea L Halpern A Hannenhalli S Kravitz S Levy S Mobarry C Reinert K Remington K Abu-Threideh J Beasley E 《Science (New York, N.Y.)》2001,291(5507):1304-1351
149.
Mundy NI Badcock NS Hart T Scribner K Janssen K Nadeau NJ 《Science (New York, N.Y.)》2004,303(5665):1870-1873
A key question in evolutionary genetics is whether shared genetic mechanisms underlie the independent evolution of similar phenotypes across phylogenetically divergent lineages. Here we show that in two classic examples of melanic plumage polymorphisms in birds, lesser snow geese (Anser c. caerulescens) and arctic skuas (Stercorarius parasiticus), melanism is perfectly associated with variation in the melanocortin-1 receptor (MC1R) gene. In both species, the degree of melanism correlates with the number of copies of variant MC1R alleles. Phylogenetic reconstructions of variant MC1R alleles in geese and skuas show that melanism is a derived trait that evolved in the Pleistocene. 相似文献
150.
Materials representing common interstratified clay minerals are shown to be composed of aggregates of fundamental particles. Transmission electron microscopy and x-ray diffraction demonstrate that the x-ray diffraction characteristics of a wide range of interstratification can be modeled experimentally by utilizing materials containing only three types of particles. The data have been incorporated into a new model that regards interstratified clay minerals as populations of fundamental particles whose x-ray diffraction patterns result from interparticle diffraction. 相似文献