全文获取类型
收费全文 | 134篇 |
免费 | 2篇 |
专业分类
林业 | 3篇 |
农学 | 6篇 |
基础科学 | 1篇 |
45篇 | |
综合类 | 33篇 |
农作物 | 2篇 |
水产渔业 | 2篇 |
畜牧兽医 | 42篇 |
园艺 | 1篇 |
植物保护 | 1篇 |
出版年
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2014年 | 2篇 |
2013年 | 8篇 |
2012年 | 1篇 |
2011年 | 7篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1940年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有136条查询结果,搜索用时 15 毫秒
41.
42.
Scherbel C Pichner R Groschup MH Mueller-Hellwig S Scherer S Dietrich R Maertlbauer E Gareis M 《Zoonoses and public health》2007,54(5):185-190
The influence of a complex microflora residing in the gastrointestinal tract of cattle on the prion protein plays a crucial role with respect to early pathogenesis and the potential infectivity of faeces resulting in contamination of the environment. It is unknown whether infectious prion proteins, considered to be very stable, are inactivated by microbial processes in the gastrointestinal tract of animals during digestion. In our previous study it was shown that the scrapie-associated prion protein was degraded by ruminal and colonic microbiota of cattle, as indicated by a loss of anti-prion antibody 3F4 immunoreactivity in Western blot. Subsequently, in this study hamster bioassays with the pre-treated samples were performed. Although the PrP(Sc) signal was reduced up to immunochemically undetectable levels within 40 h of pre-treatment, significant residual prion infectivity was retained after degradation of infected hamster brain through the gastrointestinal microflora of cattle. The data presented here show that the loss of anti-prion antibody 3F4 immunoreactivity is obviously not correlated with a biological inactivation of PrP(Sc). These results highlight the deficiency of using Western blot in transmissible spongiform encephalopathies inactivation assessment studies and, additionally, point to the possibility of environmental contamination with faeces containing PrP(Sc) following an oral ingestion of prions. 相似文献
43.
Waite JH Niemann H Yelle RV Kasprzak WT Cravens TE Luhmann JG McNutt RL Ip WH Gell D De La Haye V Müller-Wordag I Magee B Borggren N Ledvina S Fletcher G Walter E Miller R Scherer S Thorpe R Xu J Block B Arnett K 《Science (New York, N.Y.)》2005,308(5724):982-986
The Cassini Ion Neutral Mass Spectrometer (INMS) has obtained the first in situ composition measurements of the neutral densities of molecular nitrogen, methane, molecular hydrogen, argon, and a host of stable carbon-nitrile compounds in Titan's upper atmosphere. INMS in situ mass spectrometry has also provided evidence for atmospheric waves in the upper atmosphere and the first direct measurements of isotopes of nitrogen, carbon, and argon, which reveal interesting clues about the evolution of the atmosphere. The bulk composition and thermal structure of the moon's upper atmosphere do not appear to have changed considerably since the Voyager 1 flyby. 相似文献
44.
Soft materials are finding applications in areas ranging from microfluidic device technology to nanofabrication. We review recent work in these areas, discuss the motivation for device fabrication with soft materials, and describe applications of soft materials. In particular, we discuss active microfluidic devices for cell sorting and biochemical assays, replication-molded optics with subdiffraction limit features, and nanometer-scale resonators and wires formed from single-molecule DNA templates as examples of how the special properties of soft materials address outstanding problems in device fabrication. 相似文献
45.
McCauley LA Sticker D Bryan C Lasarev MR Scherer JA 《Journal of agricultural safety and health》2002,8(4):397-409
A substantial proportion of the agricultural production in the U.S. is dependent on the labor of Latino farmworkers. While exact figures are not known, it is estimated that adolescents make up 7% of this valuable workforce. These young workers may be at increased risk for the toxic effects of environmental exposures encountered during their work. Furthermore, language barriers and health beliefs may influence the risk perceptions of this population. We conducted a cross-sectional survey of migrant adolescent farmworkers in 1998 to investigate their work practices, health beliefs, and pesticide knowledge. The large majority of the adolescents in our sample were from Mexico, and 36.3% spoke primarily indigenous languages. Many of the adolescents (64.7%) were traveling and working in the U.S. independent of their parents. Few of the adolescents reported having received pesticide training; however, 21.6% of the sample reported that their current work involved mixing and/or applying agricultural chemicals. The scores on the pesticide knowledge questionnaire were found to significantly predict self-reported use of protection for adolescent farmworkers. The results of this study point to a need for improved pesticide training in youth agricultural workers and specialized education efforts directed toward minorities who speak indigenous dialects. Special attention is merited toward adolescent farmworkers who report that their work includes mixing or applying agricultural chemicals. As the number of adolescent farmworkers increases in the U.S. and the characteristics of the migrant stream continue to change, culturally and developmentally appropriate instruments are needed to adequately assess the health beliefs and protective practices of this population. 相似文献
46.
Turnover of 15N labelled nitrate nitrogen in soil as related to straw application and soil moisture In incubation experiments the effect of straw application on the turnover of 15N labelled nitrate has been studied at two soil moisture levels (brown podzolic soil). High 15N losses were found at the high soil moisture level. These losses are supposed to originate from denitrification. At both soil moisture levels straw application reduced significantly the 15N losses. Straw application resulted in a remarkable decrease of the 15NO3 content in the soil and promoted the incorporation of 15N into the organic soil fraction. The incorporation of 15N into α-amino N and particularly into the rest hydrolyzable-N fraction was favoured by straw, while the incorporation into the amide-N fraction was hampered. Exhaustive cropping (Lolium multiflorum and Sinapis alba) on the soil incubated before with 15N, showed that the 15N incorporated into the organic fraction was poorly available. Thus straw application resulted in significant yield depression. It is assumed that the fraction of the rest hydrolyzable N is hardly available to plants. 相似文献
47.
Effect of straw and nitrapyrin application on the nitrogen availability in the soil and the yield and nitrogen uptake of Lolium multiflorum. In pot experiments the effect of straw and nitrapyrin application on the turn-over of fertilizer NH and on the nitrogen availability in the soil was investigated. The investigation comprised two sections: an incubation experiment in which straw and nitrapyrin together with NH-N were incorporated into a brown podsolic soil and a subsequent pot experiment with ryegrass. Nitrapyrin inhibited the nitrification and reduced the nitrogen loss of the soil. Compared with the treatments without nitrapyrin application, nitrapyrin resulted in a lower dry matter yield and in a lower nitrogen uptake of the ryegrass. Straw application reduced the nitrate content in the soil significantly. This effect was particulary evident in the treatments which did not receive nitrapyrin. Accordingly, nitrogen uptake and yield of ryegrass were significantly lower in the ‘straw treatments’ as compared with the treatments without straw. It is suggested that the impared nitrogen availability in the ‘straw treatments’ was mainly due to nitrogen losses caused by denitrification. 相似文献
48.
We investigated the transformation of the organic P fractions from organic manure in two paddy soils (Ultisol, Entisol) and the influence of organic manure or cellulose on organic P under anaerobic conditions. The results obtained from the P fractionation experiment indicated that during the incubation labile and moderately labile organic P fractions increased in the Ultisol and decreased in the Entisol, which might be related to the difference in the organic matter content of both soils. Immediately after the application of organic manure, a large part of labile and moderately labile organic P supplied with the manure was transformed into moderately resistant organic P, possibly Ca- or Mg-inositol P were transformed into Fe-inositol P. During anaerobic incubation, the labile forms of organic P in the soils treated with organic manure were increased along with the incubation period in the first 4 weeks. The change in the moderately labile fraction was dramatic. It increased sharply in the first 2 weeks, then decreased, which was more pronounced in the soils treated with pig faeces. The moderately resistant fraction decreased during the whole incubation period. This indicated that under anaerobic conditions, the moderately resistant fraction can be transformed into labile and moderately labile organic P fractions, perhaps as Fe3+-inositol P is reduced to Fe+2-inositol P. Cellulose as an organic substrate had an increasing effect on organic P, especially when it was combined with inorganic P. Therefore, it is suggested that the application of inorganic P fertilizer combined with organic manure may be an effective way of protecting inorganic P against intensive sorption in soils. 相似文献
49.
Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission 总被引:2,自引:0,他引:2
MH Acu?a JEP Connerney P Wasilewski RP Lin KA Anderson CW Carlson J McFadden DW Curtis D Mitchell H Reme C Mazelle JA Sauvaud C d'Uston A Cros JL Medale SJ Bauer P Cloutier M Mayhew D Winterhalter NF Ness 《Science (New York, N.Y.)》1998,279(5357):1676-1680
The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported. 相似文献
50.
Interspecies somatic cell nuclear transfer (interspecies SCNT) has been explored in many domestic and non‐domestic animal species. However, problems arise during the development of these embryos, which may be related to species‐specific differences in nuclear–cytoplasmic communication. The objectives of this study were to investigate the possibility of producing bison embryos in vitro using interspecies SCNT and assess the developmental potential of these embryos. Treatment groups consisted of cattle in vitro fertilization (IVF) and cattle SCNT as controls and wood bison SCNT, plains bison SCNT and wisent SCNT as experimental groups. Cleavage and blastocyst rates were assessed, and blastocyst quality was determined using total cell number, apoptotic incidence and relative quantification of mitochondria‐related genes NRF1, MT‐CYB and TFAM. These results indicate that embryos can be produced by interspecies SCNT in all bison species/subspecies (13.34–33.54% blastocyst rates). Although increased incidence of apoptosis was observed in bison SCNT blastocysts compared to cattle SCNT controls (10.45–12.69 vs 8.76, respectively) that corresponded with significantly lower cell numbers (80–87 cells vs >100 cells, respectively), no major differences were observed in the expression of NRF1, MT‐CYB and TFAM. This study is the first to report the production of bison embryos by interspecies SCNT. Blastocyst development in all three bison species/subspecies was greater than the rates obtained in previous studies by IVF, which supports the potential role of SCNT for in vitro embryo production in this species. Yet, further investigation of developmental competence and the factors influencing blastocyst quality and viability is required. 相似文献