全文获取类型
收费全文 | 459篇 |
免费 | 15篇 |
专业分类
林业 | 135篇 |
农学 | 12篇 |
103篇 | |
综合类 | 36篇 |
农作物 | 16篇 |
水产渔业 | 22篇 |
畜牧兽医 | 123篇 |
园艺 | 7篇 |
植物保护 | 20篇 |
出版年
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 11篇 |
2012年 | 18篇 |
2011年 | 30篇 |
2010年 | 10篇 |
2009年 | 15篇 |
2008年 | 28篇 |
2007年 | 20篇 |
2006年 | 20篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 22篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1972年 | 6篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1967年 | 5篇 |
1966年 | 3篇 |
1965年 | 4篇 |
1962年 | 3篇 |
1956年 | 4篇 |
1948年 | 7篇 |
1941年 | 3篇 |
1934年 | 3篇 |
1933年 | 3篇 |
1932年 | 12篇 |
1927年 | 7篇 |
1919年 | 6篇 |
1918年 | 5篇 |
1915年 | 4篇 |
1904年 | 5篇 |
1902年 | 3篇 |
排序方式: 共有474条查询结果,搜索用时 15 毫秒
31.
32.
F. Franz 《European Journal of Forest Research》1968,87(1):257-269
Zusammenfassung In der Forstwissenschaft gewinnen neben der herk?mmlichen elektronischen Datenverarbeitung die zahlreichen Formen fortentwickelter
automatisierter Datenverarbeitung zunehmende Bedeutung. Wichtigste Voraussetzung für ihre Anwendung ist, da? Rechenanlagen
mit ausreichender Maschinenkonfiguration und leistungsf?higem Betriebssystem zur Verfügung stehen und eine angemessene Programmversorgung
gew?hrleistet ist, was heute i. d. R. vorausgesetzt werden kann. Daneben mu? eine Reihe personeller und finanzieller Mindestvoraussetzungen
geschaffen sein. Die Programmversorgung für die Datenverarbeitung in der Forstwissenschaft der Bundesrepublik stützt sich
im wesentlichen auf Programm-Bibliotheken der internationalen EDV-Benutzungsorganisationen und auf Programmquellen aus dem
engeren Bereich der mathematischen Statistik, in jüngster Zeit auch zunehmend auf Programmbest?nde forstlicher Fachinstitute
des Auslandes und auf eigene Programmentwicklungen. Die vielf?ltigen Einsatzm?glichkeiten der elektronischen Datenverarbeitung
in der Forstwissenschaft werden an Beispielen aus der Holzvorratsinventur und Stichprobensimulation, der Ertragstafelforschung,
Planungs- und Optimierungstechnik sowie am Beispiel eines neuen ?kologischen Forschungsprojektes dargestellt. Abschlie?end
wird auf einige Aussagegrenzen hingewiesen, die bei Auswertung und Interpretation von Datenverarbeitungsergebnissen zu beachten
sind.
Herrn Professor Dr.E. Assmann zu seinem 65. Geburtstag in Verehrung gewidmet. 相似文献
33.
34.
Welche Nutzorganismen sind in Europa für den blologischen Pflanzen- und Gesundheitsschutz verfügbar?
Prof. Dr. J. M. Franz 《Journal of pest science》1984,57(6):105-111
Zusammenfassung Angesichts fehlender Information über die kommerzielle Verfügbarkeit in Europa von Biopräparaten (auf der Basis von Mikroorganismen einschl. der Viren) und von nützlichen Metazoen für biologische Maßnahmen zur Unterdrückung von Schadorganismen wurde an die amtlichen Stellen, ausnahmsweise an Einzelexperten in folgenden Ländern eine Umfrage gerichtet: Frankreich, Großbritannien, Italien, Österreich, Rumänien, Jugoslawien, Schweden, die Schweiz, die Niederlande, Finnland und Bundesrepublik Deutschland. Die Ergebnisse werden in 2 Teilen als ein Momentbild des Zustandes Anfang 1984 vorgelegt. Im Begleittext wird für die Annahme einer Europäischen Zulassungsordnung für Biopräparate plädiert (die als Entwurf bereits vorliegt), um Zeit und Geld zu sparen. Zwischen den einzelnen Ländern bestehen sehr große Unterschiede bezüglich der Verfügbarkeit biotischer Agentien für biologische Verfahren. Einige vielversprechende neue Entwicklungen werden kurz in der Hoffnung vorgestellt, daß sie stimulierend wirken. Allen Kollegen, die bei der Umfrage geholfen haben, sei besonders gedankt.
Mit 2 Tabellen 相似文献
Which beneficial organisms are available in Europe for biological plant and health protection
In view of the lack of information concerning the commercial availability in Europe of biopreparations (based on microorganisms including viruses) as well as of beneficial metazoa for biological control of pest organisms, an inquiry was started for the following countries: France, Great Britain, Italy, Austria, Rumania, Yugoslavia, Sweden, Switzerland, the Netherlands, Finland and Germany Fed. Rep. Results are presented as a momentary picture of the situation in early 1984. A plead is made for the acceptance of an European protocol for registration of biopreparations (which has already been drafted) in order to save money and time. There are great differences between countries in the availability of biotic agents for biological control. Some very promising new developments are briefly reviewed and considered to act in a stimulating way. Thanks are due to those colleagues who helped to obtain the information here presented.
Mit 2 Tabellen 相似文献
35.
European Journal of Forest Research - Anhand yon Wuchsmodellen wird die Bestandesentwicktung der Kiefer bei unterschied-licher Begrüindungsdichte und Bestandesbehandlung dargestellt. Neben... 相似文献
36.
37.
Surface Electromyography of the Vastus Lateralis,Biceps Femoris,and Gluteus Medius Muscle in Sound Dogs During Walking and Specific Physiotherapeutic Exercises
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)
38.
Ana Afonso Jose Cortinas Abrahantes Franz Conraths Anouk Veldhuis Armin Elbers Helen Roberts Yves Van der Stede Estelle Méroc Kristel Gache Jane Richardson 《Preventive veterinary medicine》2014
During the Schmallenberg virus (SBV) epidemic, the European Food Safety Authority (EFSA) collected data on SBV occurrence across Europe in order to provide an assessment of spread and impact. By May 2013, twenty-nine countries were reporting to EFSA and twenty-two countries had reported cases of SBV. The total number of SBV herds reported was 13,846 and the number of SBV laboratory confirmed herds was 8730. The surveillance activities were based on the detection of SBV clinical cases (either adults or newborns). Malformation in newborns was the most commonly reported clinical sign of SBV-infection. All countries were able to provide the date when the first suspicion of SBV in the herd was reported and nineteen could report the location of the herd at a regional level. This allowed the spread of SBV in Europe to be measured both temporally and spatially. The number of SBV confirmed herds started to increase in December 2011 and two peaks were observed in 2012 (February and May). Confirmed herds continued to be reported in 2012 and into 2013. An increase during winter 2012 and spring 2013 was again observed, but the number of confirmed herds was lower than in the previous year. SBV spread rapidly throughout Europe from the initial area of detection. SBV was detected above the latitude of 60° North, which exceeds the northern expansion observed during the bluetongue virus serotype 8 epidemic in 2006–2009. The impact of SBV was calculated as ratio of the number of herds with at least one malformed SBV positive foetus and the total number of herds in this region. The 75th percentile of the malformations ratio in the various affected countries for the whole reporting period was below 1% and 3% for cattle and sheep herds, respectively. International data collection on emerging diseases represents a challenge as the nature of available data, data quality and the proportion of reported cases may vary widely between affected countries. Surveillance activities on emerging animal diseases are often structured only for case detection making the estimation of infection/diseases prevalence and the investigation of risk factors difficult. The impact of the disease must be determined to allow risk managers to take appropriate decisions. Simple within-herd impact indicators suitable for emerging disease outbreaks should be defined that could be measured as part of routine animal health surveillance programmes and allow for rapid and reliable impact assessment of emerging animal health diseases. 相似文献
39.
Tropical regions are currently undergoing remarkable rates of land use change accompanied by altered litter inputs to soil. In vast areas of Southern Ecuador forests are clear cut and converted for use as cattle pastures. Frequently these pasture sites are invaded by bracken fern, when bracken becomes dominant pasture productivity decreases and the sites are abandoned. In the present study implications of invasive bracken on soil biogeochemical properties were investigated. Soil samples (0-5 cm) were taken from an active pasture with Setaria sphacelata as predominant grass and from an abandoned pasture overgrown by bracken. Grass (C4 plant) and bracken (C3 plant) litter, differing in C:N ratio (33 and 77, respectively) and lignin content (Klason-lignin: 18% and 45%, respectively), were incubated in soils of their corresponding sites and vice versa for 28 days at 22 °C. Unamended microcosms containing only the respective soil or litter were taken as controls. During incubation the amount of CO2 and its δ13C-signature were determined at different time intervals. Additionally, the soil microbial community structure (PLFA-analysis) as well as the concentrations of KCl-extractable C and N were monitored. The comparison between the control soils of active and abandoned pasture sites showed that the massive displacement of Setaria-grass by bracken after pasture abandonment was characterized by decreased pH values accompanied by decreased amounts of readily available organic carbon and nitrogen, a lower microbial biomass and decreased activity as well as a higher relative abundance of actinomycetes. The δ13C-signature of CO2 indicated a preferential mineralization of grass-derived organic carbon in pasture control soils. In soils amended with grass litter the mineralization of soil organic matter was retarded (negative priming effect) and also a preferential utilization of easily available organic substances derived from the grass litter was evident. Compared to the other treatments, the pasture soil amended with grass litter showed an opposite shift in the microbial community structure towards a lower relative abundance of fungi. After addition of bracken litter to the abandoned pasture soil a positive priming effect seemed to be supported by an N limitation at the end of incubation. This was accompanied by an increase in the ratio of Gram-positive to Gram-negative bacterial PLFA marker. The differences in litter quality between grass and bracken are important triggers of changes in soil biogeochemical and soil microbial properties after land use conversion. 相似文献
40.