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51.
Johannes?EichhornEmail author Regina?Icke Ansgar?Isenberg Uwe?Paar Egbert?Sch?nfelder 《European Journal of Forest Research》2005,124(4):335-347
The evaluation uses the longest available time series for beech and oak defoliation in Germany. The data from Hesse, starting
from 1984, show a typical pattern: for the first 12 years, a continuous increase in defoliation was observed ranging from
an average value of 14% in 1984 to a peak value of 30%. This was followed by a subsequent decrease in the loss of foliage
accompanied by a high variability, until the last monitoring in 2003, where an average value of 25% defoliation was observed.
For both tree species, the years of trend reversal were identical. The same pattern was observed in the German federal states:
Rhineland-Palatinate, North Rhine-Westphalia, and Bavaria. The year of trend reversal was identical in Hesse and Rhineland-Palatinate.
In North Rhine-Westphalia, it occurred 1 year earlier and in Bavaria 3 years earlier. Whereas defoliation trends were clearly
demonstrated, tree mortality did not appear on a large scale. The sample trees were grouped into four discrete clusters according
to their annual defoliation values from 1984 to 2003. In 1996, the clusters represent 15, 25, 35, and 50% defoliation values.
Regarding beech in Hesse, there was no overlap in the defoliation curves observed among the different clusters. These four
clusters having different degrees of defoliation over the whole time span of 20 years were used for a further detailed statistical
analysis. For discrete variables like crown spacing and—in the case of beech—fruit bearing, mosaic plots were applied in order
to visualize relations of low dimensional contingency tables, with defoliation trends being used as the response variable.
The data show for beech a very clear relation between defoliation and age, relative crown spacing, stand composition, and
fruit bearing. Regarding oak, besides age and relative crown spacing, the years with significant appearance of biotic stress
factors—leaf eating insects—show a clear relation to trends of defoliation. The statistical model used in this study—logistic
regression—allows applying a multinomial response variable and a number of continuous or categorical explanatory variables.
With this approach, an iterative optimized selection of effect variables was used to test the relevance of different variables
on the defoliation pattern of the same four clusters mentioned above. For this, the variables were grouped in an iterative
process with five steps, starting with a few basic variables of tree and site information, and ending with a total of more
than 20 variables in the fifth step. The process selects first the variables which are of significance on the defoliation,
and calculates the possible errors in the grouping of the different trees to the four clusters. In this analysis of beech,
the basic tree and stand variables: age, relative crown spacing, stand composition and fruit bearing proved to be the most
relevant group of parameters, with the other variables explaining the variation of defoliation only to a minor extent. More
complex model levels do not change any basic selected variables; however, Cation Exchange Capacity (CEC), C/N-ratio, Al- and
Ca-proportion of CEC are additionally selected and give a hint of the relevance of soil conditions. Regarding beech, the errors
of the statistical model are lower compared to oak. 相似文献
52.
53.
Breme K Fernandez X Meierhenrich UJ Brevard H Joulain D 《Journal of agricultural and food chemistry》2007,55(5):1932-1938
New, odorant nitrogen- and sulfur-containing compounds are identified in cress extracts. Cress belongs to the botanical order Brassicales and produces glucosinolates, which are important precursors of nitrogen- and sulfur-containing compounds. Those compounds often present low perception thresholds and various olfactive notes and are thus of interest to the flavor and fragrance chemistry. When the study of organonitrogen and organosulfur compounds is undertaken, Brassicale extracts are one of the matrices of choice. Cress extracts were studied by analytical (GC-MS, GC-FPD) and chemical (fractionation) means to identify new interesting odorant compounds. Two compounds that have never been reported in cress extracts, containing both nitrogen and sulfur, were discovered: N-benzyl O-ethyl thiocarbamate and N-phenethyl O-ethyl thiocarbamate. These two molecules being of organoleptic interest, their homologues were synthesized and submitted to organoleptic tests (static and GC-sniffing). Their odors evolve from garlic and onion over green, mushroom- and cress-like to fresh, spearmint-like. This paper presents the origin, chemical synthesis, and organoleptic properties of a series of O-alkyl thiocarbamates. 相似文献
54.
Enzymatic and topochemical aspects of lignification were studied in a Pinus radiata D. Don cell culture system that was induced to differentiate tracheary elements and sclereids with lignified secondary cell walls. The activities of the lignin-related enzymes phenylalanine ammonia lyase (PAL; EC 4.3.1.5) and cinnamyl alcohol dehydrogenase (CAD; EC 1.1.1.195) increased concomitantly with cell differentiation, indicating that the increase in enzyme activity was related to lignification of the cell walls and was not induced by stress. This result also indicates that PAL and CAD are suitable markers for tracheary element differentiation in coniferous gymnosperms. To further characterize lignification in this cell culture system, cellular UV-microspectrophotometry and thioacidolysis were employed. Typical UV-absorption spectra of lignin were obtained from the secondary cell walls of the tracheary elements and sclereids and from the compound middle lamella connecting differentiated cells, and the presence of lignin was confirmed by thioacidolysis. Certain aspects of lignin topochemistry in the cell walls of the tracheary elements were similar to cell walls of P. radiata wood, such as the high lignin concentration in the compound middle lamella connecting adjacent cells and the lower lignin concentration in the secondary cell walls. Therefore, the P. radiata cell culture system appears to be well suited to study the formation of lignified secondary cell walls in coniferous gymnosperms. 相似文献
55.
Anja Guckland Bernd Ahrends Uwe Paar Inge Dammann Jan Evers Karl Josef Meiwes Egbert Sch?nfelder Thomas Ullrich Michael Mindrup Nils K?nig Johannes Eichhorn 《European Journal of Forest Research》2012,131(6):1869-1887
Forest liming is a common measure to counteract soil acidification. In forest practice, lime is applied to the forest floor where it changes the chemical properties. However, little is known about the depth impact of liming and the depth translocation of lime components. To investigate the long-term impact of forest liming, several study plots have been established in the 1980s in Germany in stands with different site conditions. We analysed soil chemical data obtained during the last 28?years from 45 of the study plots. We examined the depth impact of liming and predicted the main factors responsible for the increase in Calcium (Ca) and Magnesium (Mg) stocks after liming in the mineral soil using multiple linear regression analyses (MLR). Stocks of Ca and Mg as well as base saturation (BS) showed a strong depth gradient with significant differences between limed and control plots down to 40?cm of the mineral soil. About 65–70?% of applied Ca and Mg were recovered in the forest floor and the upper 40?cm of the mineral soil. BS in 0–40?cm increased by a mean of 11?%. MLR models could explain 48–74?% of the variation in mean changes of Ca and Mg in 0–10, 10–20 and 20–40?cm soil depth when soil and climate variables, amount of applied lime and years after liming are included in the model. After testing the model robustness with a cross-validating procedure, we concluded that these models might be applied to many regions in Central Europe with comparable soil and climate conditions and thus, have widespread application. 相似文献
56.
Reddy V Nathues A Le Corre L Sierks H Li JY Gaskell R McCoy T Beck AW Schröder SE Pieters CM Becker KJ Buratti BJ Denevi B Blewett DT Christensen U Gaffey MJ Gutierrez-Marques P Hicks M Keller HU Maue T Mottola S McFadden LA McSween HY Mittlefehldt D O'Brien DP Raymond C Russell C 《Science (New York, N.Y.)》2012,336(6082):700-704
Multispectral images (0.44 to 0.98 μm) of asteroid (4) Vesta obtained by the Dawn Framing Cameras reveal global color variations that uncover and help understand the north-south hemispherical dichotomy. The signature of deep lithologies excavated during the formation of the Rheasilvia basin on the south pole has been preserved on the surface. Color variations (band depth, spectral slope, and eucrite-diogenite abundance) clearly correlate with distinct compositional units. Vesta displays the greatest variation of geometric albedo (0.10 to 0.67) of any asteroid yet observed. Four distinct color units are recognized that chronicle processes--including impact excavation, mass wasting, and space weathering--that shaped the asteroid's surface. Vesta's color and photometric diversity are indicative of its status as a preserved, differentiated protoplanet. 相似文献
57.
Boutet S Lomb L Williams GJ Barends TR Aquila A Doak RB Weierstall U DePonte DP Steinbrener J Shoeman RL Messerschmidt M Barty A White TA Kassemeyer S Kirian RA Seibert MM Montanez PA Kenney C Herbst R Hart P Pines J Haller G Gruner SM Philipp HT Tate MW Hromalik M Koerner LJ van Bakel N Morse J Ghonsalves W Arnlund D Bogan MJ Caleman C Fromme R Hampton CY Hunter MS Johansson LC Katona G Kupitz C Liang M Martin AV Nass K Redecke L Stellato F Timneanu N Wang D Zatsepin NA Schafer D Defever J 《Science (New York, N.Y.)》2012,337(6092):362-364
Structure determination of proteins and other macromolecules has historically required the growth of high-quality crystals sufficiently large to diffract x-rays efficiently while withstanding radiation damage. We applied serial femtosecond crystallography (SFX) using an x-ray free-electron laser (XFEL) to obtain high-resolution structural information from microcrystals (less than 1 micrometer by 1 micrometer by 3 micrometers) of the well-characterized model protein lysozyme. The agreement with synchrotron data demonstrates the immediate relevance of SFX for analyzing the structure of the large group of difficult-to-crystallize molecules. 相似文献
58.
Alexander Rebl Tom Goldammer Uwe Fischer Bernd Kllner Hans-Martin Seyfert 《Veterinary immunology and immunopathology》2009,131(1-2):122-126
Toll-like receptors (TLR) are relevant for piscine innate immunity. TLR activation recruits several downstream factors regulating the expression of immunorelevant genes. We have characterized two key factors of innate immunity from rainbow trout: MyD88 as an adaptor protein interacting directly with TLRs, and serum amyloid A as an effector molecule induced by the activated Toll-like receptor signaling cascade.Both factors share a remarkable high degree of structural conservation with their mammalian orthologs suggesting that innate immune defense mechanisms may also functionally be conserved between fish and mammals. 相似文献
59.
Mrcio Garcia Ribeiro Marconi Rodrigues de Farias Uwe Roesler Katja Roth Sabrina Mari Rodigheri Marco Antonio Ostrowsky Tatiana Salerno Amanda Keller Siqueira Marta Catarina Fernandes 《Research in veterinary science》2009,87(3):479-481
This is a case report of enteric protothecosis caused by Prototheca zopfii in an eight-year-old male mixed breed dog with a history of chronic bloody diarrhea, loss of appetite and weight loss. Algae were isolated from rectal scrapings in defibrinated sheep blood agar and dextrose Sabouraud agar. Cytological evaluation showed the presence of globular and cylindrical organisms with a defined capsule and variable number of endospores, characteristic of the genus Prototheca, in the rectum of the animal. Scanning electron microscopy of P. zopfii strains at different development stages confirmed the diagnosis of algal infection. Molecular identification using a conserved 18S rDNA gene sequence determined that the strain belonged to genotype 2. This report describes success on treatment of canine protothecosis, diagnosed based on clinical, cytological, microbiological, scanning electron microscopy and genotypical findings. 相似文献
60.
Herman Egberink Diane Addie Sándor Belák Corine Boucraut-Baralon Tadeusz Frymus Tim Gruffydd-Jones Katrin Hartmann Margaret J. Hosie Albert Lloret Hans Lutz Fulvio Marsilio Maria Grazia Pennisi Alan D. Radford Etienne Thiry Uwe Truyen Marian C. Horzinek 《Journal of Feline Medicine and Surgery》2009,11(7):610-614