全文获取类型
收费全文 | 1676篇 |
免费 | 110篇 |
专业分类
林业 | 98篇 |
农学 | 29篇 |
基础科学 | 11篇 |
255篇 | |
综合类 | 357篇 |
农作物 | 58篇 |
水产渔业 | 105篇 |
畜牧兽医 | 772篇 |
园艺 | 36篇 |
植物保护 | 65篇 |
出版年
2023年 | 16篇 |
2022年 | 20篇 |
2021年 | 41篇 |
2020年 | 49篇 |
2019年 | 51篇 |
2018年 | 37篇 |
2017年 | 35篇 |
2016年 | 47篇 |
2015年 | 24篇 |
2014年 | 43篇 |
2013年 | 65篇 |
2012年 | 103篇 |
2011年 | 121篇 |
2010年 | 68篇 |
2009年 | 50篇 |
2008年 | 115篇 |
2007年 | 90篇 |
2006年 | 95篇 |
2005年 | 72篇 |
2004年 | 56篇 |
2003年 | 72篇 |
2002年 | 70篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1996年 | 13篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1972年 | 7篇 |
1971年 | 13篇 |
1969年 | 12篇 |
1968年 | 7篇 |
1967年 | 13篇 |
排序方式: 共有1786条查询结果,搜索用时 203 毫秒
101.
Conclusions
German federal research plan from the German Federal Ministry for the Environment, Wildlife Conservation and Nuclear Safety
- Treatment and utilization of wastes. Research report 297 33 911 - UBA-FB 000074. Original title: Charakterisierung und Verwertung
von Abf?llen aus der Massentierhaltung unter Berücksichtigung verschiedener B?den. Stoffeintrag in B?den durch Tierarzneimittel
und pharmakologisch wirksame Futterzusatzstoffe unter besonderer Berücksichtigung von Tetrazyklinen. A research article on
this topic follows in JSS No. 2.
DOI: http://dx.doi.org/10.1065/jss2001.02.006. By courtesy of the German Federal Environmental Agency (Umweltbundesamt - UBA).
The complete research report is available as UBA-TEXTE 44/00 (ISSN 0722-186X) by payment of DM 20,00 (Euro 10,26), account
no. 4327 65-104, Postbank Berlin (BLZ 10010010), Fa. Werbung und Vertrieb, Ahornstra?e 1-2, D-10787 Berlin, Germany 相似文献
– | •In intensive animal production, a considerable proportion of the livestock population must be expected to receive animal pharmaceuticals. |
– | •The administration of pharmacologically-active feed additives has been influenced through the revocation of approval for some individual substances over the last few years. Aside from the substitution of these forbidden substances, further reductions in the use of antibiotic growth promotors can be expected primarily because of economic reasons. |
– | •Animal pharmaceuticals frequently consist of so-called older preparations whose ecotoxicological potentials have only been investigated inadequately. |
– | •High elimination rates of the active substances and their stability during storage, which could be demonstrated for tetracyclines, might also lead to a significant incorporation of these substances into the soil even when they are employed correctly. In the future, ecotoxicological investigations should be demanded in cases where the EMEA/CVMP trigger values (which are substantially lower) have been exceeded, a procedure which is currently only required for the newly approved agents. |
– | •There is presently a considerable need for research into the environmental fate of these older preparations and their ecotoxicological effects. Here, it will be especially important to take the degradation and transformation processes in the soil into account, as well as especially considering the consequences on the microbiological impacts affecting the soil. |
– | •Improved transparency in the application of these substances, in the sense of a quantitative’registration of the animal pharmaceuticals (especially the older preparations) which are employed, as well as the environmental monitoring of animal pharmaceuticals (e.g. in groundwater and surface water), would considerably improve the significance of the basic data for future appraisals. |
102.
A fully automated rain exclusion canopy system has been designed and constructed to study the impact of simulated acid rain on the growth and yield of agricultural crops. The system consists of three, mobile greenhouse shelters which exclude ambient rainfall and apply simulated acid rain (SAR) treatments to crops established in field plots. All aspects of the field system are controlled by a microcomputer and data acquisition system. In addition, elevated ambient levels of gaseous pollutants (e.g. O3, SO2, NOx) are reduced in field plots via an air exclusion system consisting of large blowers, potassium permanganate-treated alumina filters and perforated polyethylene tubes. Gaseous pollutants can be injected into the treatment plots via the blowers. 相似文献
103.
104.
105.
Neuron activity related to short-term memory 总被引:39,自引:0,他引:39
Nerve cells in the monkey's prefrontal cortex and nucleus medialis dorsalis of the thalamus show changes of firing frequency associated with the performance of a delayed response test. Most cells increase firing during the cue presentation period or at the beginning of the ensuing delay; spike discharge highler than that in intertrial periods is present in some cells throughout the delay. These changes are interpreted as suggestive evidence of a role of frontothalamic circuits in the attentive process involved in short-term memory 相似文献
106.
Rensing SA Lang D Zimmer AD Terry A Salamov A Shapiro H Nishiyama T Perroud PF Lindquist EA Kamisugi Y Tanahashi T Sakakibara K Fujita T Oishi K Shin-I T Kuroki Y Toyoda A Suzuki Y Hashimoto S Yamaguchi K Sugano S Kohara Y Fujiyama A Anterola A Aoki S Ashton N Barbazuk WB Barker E Bennetzen JL Blankenship R Cho SH Dutcher SK Estelle M Fawcett JA Gundlach H Hanada K Heyl A Hicks KA Hughes J Lohr M Mayer K Melkozernov A Murata T Nelson DR Pils B Prigge M Reiss B Renner T Rombauts S Rushton PJ 《Science (New York, N.Y.)》2008,319(5859):64-69
We report the draft genome sequence of the model moss Physcomitrella patens and compare its features with those of flowering plants, from which it is separated by more than 400 million years, and unicellular aquatic algae. This comparison reveals genomic changes concomitant with the evolutionary movement to land, including a general increase in gene family complexity; loss of genes associated with aquatic environments (e.g., flagellar arms); acquisition of genes for tolerating terrestrial stresses (e.g., variation in temperature and water availability); and the development of the auxin and abscisic acid signaling pathways for coordinating multicellular growth and dehydration response. The Physcomitrella genome provides a resource for phylogenetic inferences about gene function and for experimental analysis of plant processes through this plant's unique facility for reverse genetics. 相似文献
107.
108.
109.
110.