全文获取类型
收费全文 | 224篇 |
免费 | 9篇 |
专业分类
林业 | 111篇 |
农学 | 2篇 |
16篇 | |
综合类 | 19篇 |
农作物 | 8篇 |
水产渔业 | 4篇 |
畜牧兽医 | 62篇 |
园艺 | 3篇 |
植物保护 | 8篇 |
出版年
2018年 | 3篇 |
2016年 | 5篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2010年 | 5篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 21篇 |
2005年 | 8篇 |
2002年 | 3篇 |
2000年 | 3篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1989年 | 2篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1968年 | 2篇 |
1961年 | 2篇 |
1938年 | 3篇 |
1936年 | 3篇 |
1931年 | 4篇 |
1930年 | 3篇 |
1928年 | 2篇 |
1927年 | 2篇 |
1926年 | 3篇 |
1925年 | 2篇 |
1924年 | 3篇 |
1922年 | 2篇 |
1916年 | 2篇 |
1915年 | 3篇 |
1913年 | 2篇 |
1909年 | 7篇 |
1908年 | 5篇 |
1907年 | 2篇 |
1906年 | 5篇 |
1902年 | 3篇 |
1901年 | 2篇 |
1898年 | 3篇 |
1894年 | 2篇 |
排序方式: 共有233条查询结果,搜索用时 78 毫秒
101.
Professor Dr. Helmut Koblitz 《Genetic Resources and Crop Evolution》1982,30(1):27-43
Zusammenfassung Übersicht zu Anwendungen der Gewebekulturtechnik (Kalluskultur, Sproß- und Pflanzenregeneration aus Explantaten, Antherenkultur, Embryokultur, mit Ausnahme von Protoplastentechniken) in der GattungLycopersicon Miller.
Herrn Prof. Dr. Dr. h. c. mult.Hans Stubbe mit herzlichen Glückwünschen zu seinem achtzigsten Geburtstag gewidmet. 相似文献
Experiments on tissue culture in the genusLycopersicon Miller. I. Survey
Summary A survey is given concerning applications of tissue culture techniques (callus culture, shoot and plant regeneration from explants and calluses, anther culture, embryo culture, except protoplast techniques) in the genusLycopersicon Miller.
Lycopersicon Miller. I.
Lycopersicon Miller ( ): , , .
Herrn Prof. Dr. Dr. h. c. mult.Hans Stubbe mit herzlichen Glückwünschen zu seinem achtzigsten Geburtstag gewidmet. 相似文献
102.
103.
104.
Peach fruit easily soften and have a short storage time at normal temperature. In this study, peach fruit (Prunus persica sieb et Zucc cv. Yingqing) were picked and stored at 25 and 4℃ to investigate the senescence in correlation with Ca^2+- ATPase activity of microsomal membrane and lipid peroxidation during ripening and senescence. In comparison with that stored at 25~C, the fruit stored at 4℃ exhibited a higher flesh firmness, lower respiration rate, and generated the late bigger peak value of Ca^2+-ATPase activity as well as maintained the higher activity of the enzyme. Meanwhile, the lower levels of super oxygen radical (O2^-.) production and content of malondialdehyde (MDA), a product of membrane lipid peroxidation were observed. Sodium orthovanadate (SO) and erythrosin B (EB), as Ca^2+-ATPase inhibitors, could stimulate the respiration rate. The results suggested that the slower senescence rate of peach fruit was closely related to the higher peak value and longer duration of Ca^2+-ATPase activity in microsomal membrane, with the slighter membrane lipid peroxidation and lower O2^-. production rate. 相似文献
105.
Ultrastructural analysis of softwood fracture surfaces 总被引:2,自引:0,他引:2
Assistant Professor A. G. Zink Professor P. J. Pelikane Associate Professor C. E. Shuler 《Wood Science and Technology》1994,28(5):329-338
Summary The ultrastructural characteristics of fracture surfaces from southern pine and Douglas-fir specimens tested in tension at various angles to grain were examined. The fracture surace morphology was inspected using scanning electron microscopy. Three anatomical failure types were recognized: intercell failure, transwall failure, and intrawall failure. Certain failure characteristics were ascribed as a function of the magnitudes of paralleland perpendicular-tograin tension and parallel-to-grain shear present in the specimen. In specimens tested in paralleland perpendicular-to-grain tension, the thick-walled latewood cells were found to fail in a combination of transwall and intrawall failure. The intrawall failures were usually at the S1–S2 interface. The more thin-walled earlywood cells were more likely to exhibit abrupt, transwall failures. At intermediate angles of load to grain, surfaces indicative of the type found in pure shear tests were predominant. Perpendicularto-grain tension failures resulted in mostly intercell failures. Ray cells consistently exhibited transwall failures. The failure surface frequently changed planes in all loading modes. This path transfer was inevidably associated with material discontinuities in the wood. When the path did transfer, all three failure types were observed. No significant species effect was observed. 相似文献
106.
Danny W. Scott Professor of Medicine 《Veterinary dermatology》2003,14(2):117-117
107.
Soil Use and Management 总被引:9,自引:0,他引:9
108.
Summary A report is given on biochemical mutants in higher plants with emphasis on metabolic mutants. Since the discovery of thiamine-defective mutants inArabidopsis thaliana andLycopersicon esculentum some other mutants in different species became available. The first higher plant with an absolute requirement for an amino acid is a proline-deficient mutant inZea mays. Inchloronerva ofLycopersicon esculentum synthesis of nicotianamine is blocked. This is the first instance where a hitherto unknown function is attributed to an already known compound by work with a mutant of higher plants. Nicotianamine is distributed throughout all vascular plants and appears to be linked with short-distance iron transport. The wilty mutantflacca inL. esculentum lacks abscisic acid with some consequences to different parts of metabolism. In the same species the mutant T 3238btl/btl, fer/fer carries two separate, independent mutations which affect the transport of boron and iron, respectively. Selection for chlorate resistance led to the discovery of mutants with impaired nitrate reductase activity and nitrate uptake inArabidopsis thaliana and in consequence added new information to our knowledge of the regulation of nitrate assimilation. Other mutants of similar kind were detected inNicotiana tabacum andHordeum vulgare. Mutants with defects in the photosynthetic system were discovered inZea mays andHordeum vulgare. Plastome mutants inOenothera revealed a lack of ribulose-1,5-biphosphate carboxylase activity and showed interference between the genetic system of the plastids and that of the nucleus.The search for new mutations should be continued by different techniques, whereby the chance to find auxotrophic mutants by grafts should not be overlooked.
Biochemische Mutanten höherer Pflanzen als Objekte für chemische und physiologische Untersuchungen. Eine Übersicht
Zusammenfassung Es wird über biochemische Mutanten höherer Pflanzen unter besonderer Berücksichtigung von Stoffwechsel-Mutanten berichtet. Seit der Entdeckung von Thiamin-Mangelmutanten beiArabidopsis thaliana undLycopersicon esculentum sind einige andere Mutanten verschiedener Arten bekannt geworden. Die erste höhere Pflanze mit einem absoluten exogenen Aminosäure-Bedürfnis ist eine Prolin-Mangelmutante vonZea mays. Inchloronerva vonLycopersicon esculentum ist die Synthese von Nicotianamin blockiert. Dieses ist der erste Fall, bei dem durch Untersuchungen an der Mutante einer höheren Pflanze Aufschluß über die Funktion einer bereits bekannten, hinsichtlich ihrer biochemischen Rolle aber noch unerforschten Verbindung gewonnen werden konnte. Nicotianamin ist wahrscheinlich in allen Gefäßpflanzen vorhanden und steht dort mit dem Eisen-Nahtransport in Beziehung. Die Welke-Mutanteflacca vonL. esculentum produziert keine Abscisinsäure, was Auswirkungen auf verschiedene Richtungen des Stoffwechsels hat. In der gleichen Species trägt die Mutante T 3238btl/btl, fer/fer gleichzeitig zwei verschiedene, voneinander unabhängige Mutationen, die den Bor- bzw. den Eisentransport betreffen. Selektion auf Chlorat-Resistenz führte beiArabidopsis thaliana zur Entdeckung von Mutanten mit blockierter Nitratreduktase-Aktivität und verminderter Nitrataufnahme. Untersuchungen mit diesen Formen erbrachten neue Vorstellungen über die Regulation der Nitratassimilation. Ähnliche Mutanten wurden auch beiNicotiana tabacum undHordeum vulgare gefunden. Mutanten mit defektem Photosynthese-System sind beiZea mays undHordeum vulgare bekannt. Eine Plastom-Mutante vonOenothera zeigt einen Synthese-Block im Hinblick auf Ribulose-1,5-biphosphat-Carboxylase, der sich auf beide Untereinheiten auswirkt, so daß Wechselwirkungen zwischen dem genetischen System der Piastiden und dem des Kernes angenommen werden müssen.
. —
, ë , . - . , ë - . chloronerva . , , , , . , . flacca , . , 3238 btl/btl, fer/fer, , , . ë . . . . -1,5- -, , . , ë .相似文献
109.
Associate Professor R. C. Knox George Lynn Cross Research Professor Sun Company Professor of Ground Water Hydrology Director L. W. Canter 《Water, air, and soil pollution》1996,88(3-4):205-226
The objective of this research was to identify chemical, physical, bacteriological, and viral contaminants, and their sources, which present the greatest health threat in public ground water supplies in the USA; and to classify (prioritize) such contaminants and relative to their health concerns. The developed contaminant prioritization methodology was based on frequency of occurrence and adverse health effects. Adverse health effects were based on carcinogenic potency, toxicity, hazardous chemical priorities and drinking water standards. Application of the methodology for wellhead protection areas, (WHPAs) revealed that approximately 200 different contaminants have been detected in the nation's public ground water supplies. The seven chemical constituents with the highest priority were arsenic, chromium, cadmium, carbon tetrachloride, chloroform, 1, 1-dichloroethylene, and ethylene dibromide. Other contaminants of concern were trichloroethylene, nitrates, barium, 1,1,1-trichloroethane, benzene, tetrachloroethylene, selenium, lead, toluene, mercury, gross alpha radiation, methylene chloride, coliform bacteria, metolachlor, metribuzin, 1, 1, 2, 2-tetrachloroethane, dibromochloroethane, simazine, radium-266, and toxaphene. The contaminant source prioritization methodology was also based on frequency of occurrence. Over 30 categories of sources were evaluated, with the eight with highest priority including agricultural activities, hazardous waste sites, landfills, industrial operations, septic tank systems, oil and gas field activities, urban land use, and underground storage tanks. 相似文献
110.