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1.
MARION BREUER GERALD SCHULTE KLAUS J. SCHWEGMANN HELMUT J. SCHMIDT 《The Journal of eukaryotic microbiology》1996,43(4):314-322
ABSTRACT. When Paramecium tetraurelia expresses the D serotype, detectable by serum tests, high molecular mRNA could be isolated, which corresponds to the molecular mass of the D surface protein. Using this D specific mRNA as a probe for screenings in different genomic libraries a subfamily of five very similar genes was found, named α-51D, γ1 -51D, γ2 -51D, δ-51D and ε-51D. Each of them is about 8-kb long, they show regions of identity to each other, and there is no evidence that any are defective genes or pseudogenes. Up to now serotype D is the only known serotype showing this phenomenon. Another novel feature is that two of the D isogenes are closely linked. The sequence for the entire coding region of the α-51D gene has been determined, as well as the upstream and downstream noncoding regions. Its deduced amino acid sequence shows the same characteristic cysteine periodicity displayed by all other immobilization antigen (i-ag) genes from Paramecium. However, in contrast to most other such genes, tandem repeats are missing from the 7599-bp long coding region of the α-51D gene. When the sequences of the type 51D genes are compared to each other, the similarity is very high and extends to coding as well as to noncoding regions. Similarity within noncoding regions is usually only observed for allelic i-ag genes. We conclude that the type D genes constitute a family of isogenes that are nonallelic. They contain slightly different consensus sequences with possible functions as regulatory regions. 相似文献
2.
WINTER KLAUS; HOLTUM JOSEPH A. M.; EDWARDS GERALD E.; O'LEARY MARION H. 《Journal of experimental botany》1982,33(1):88-91
When grown under conditions of low relative humidity, the C3C4intermediate Panicum milioides, as well as the C3 grasses Triticumaestivum and Poa pratense, exhibited 13C values which were upto 27%o less negative than the 13C values of the correspondingplants grown at high relative humidity. At both humidity levels,there was no evidence of a substantial contribution of phosphoenolpyruvatecarboxylase to carbon gain in Panicum milioides 相似文献
3.
Comparisons were made of the host ranges, interactions in infected plants, and effects on yields of cereals of two isolates of barley yellow-dwarf virus, one avirulent, RV, obtained from Rothamsted farm (Watson & Mulligan, 1956) and the other virulent, KV, obtained from Kent. They resembled each other and the American yellow-dwarf viruses in their ability to infect wild grasses but differences were found when the infection tests were made using inbred lines of the same grass species. KV infected one variety each of rice, rye and maize, and caused symptoms in each.
When plants were first infected with RV and later, when symptoms had fully developed, with KV, they suffered the same loss of yield from KV as did plants infected for the same length of time with KV alone. Therefore plants infected with RV were not protected against infection with KV. Similarly, aphids ( Rhopalosiphum padi L.), fed first on sources of RV and then on KV, transmitted mainly KV so there was no evidence of protection in the insect vectors.
Effects on yield of cereals were related to the time of appearance and intensity of symptoms. The effect of RV was not only less than that of KV but was also more variable. 相似文献
When plants were first infected with RV and later, when symptoms had fully developed, with KV, they suffered the same loss of yield from KV as did plants infected for the same length of time with KV alone. Therefore plants infected with RV were not protected against infection with KV. Similarly, aphids ( Rhopalosiphum padi L.), fed first on sources of RV and then on KV, transmitted mainly KV so there was no evidence of protection in the insect vectors.
Effects on yield of cereals were related to the time of appearance and intensity of symptoms. The effect of RV was not only less than that of KV but was also more variable. 相似文献
4.
5.
ZHI-BIN LUO CARLO CALFAPIETRA† MARION LIBERLOO‡ GIUSEPPE SCARASCIA-MUGNOZZA† ANDREA POLLE 《Global Change Biology》2006,12(2):272-283
To determine whether globally increasing atmospheric carbon dioxide (CO2) concentrations can affect carbon partitioning between nonstructural and structural carbon pools in agroforestry plantations, Populus nigra was grown in ambient air (about 370 μmol mol?1 CO2) and in air with elevated CO2 concentrations (about 550 μmol mol?1 CO2) using free‐air CO2 enrichment (FACE) technology. FACE was maintained for 5 years. After three growing seasons, the plantation was coppiced and one half of each experimental plot was fertilized with nitrogen. Carbon concentrations and stocks were measured in secondary sprouts in seasons of active growth and dormancy during 2 years after coppicing. Although FACE, N fertilization and season had significant tissue‐specific effects on carbon partitioning to the fractions of structural carbon, soluble sugars and starch as well as to residual soluble carbon, the overall magnitude of these shifts was small. The major effect of FACE and N fertilization was on cell wall biomass production, resulting in about 30% increased above ground stocks of both mobile and immobile carbon pools compared with fertilized trees under ambient CO2. Relative C partitioning between mobile and immobile C pools was not significantly affected by FACE or N fertilization. These data demonstrate high metabolic flexibility of P. nigra to maintain C‐homeostasis under changing environmental conditions and illustrate that nonstructural carbon compounds can be utilized more rapidly for structural growth under elevated atmospheric [CO2] in fertilized agroforestry systems. Thus, structural biomass production on abandoned agricultural land may contribute to achieving the goals of the Kyoto protocol. 相似文献
6.
7.
SYNOPSIS. Using intervals up to 5 hours, attempts to excyst sporozoites of Eimeria acervulina from intact oocysts in vitro were unsuccessful.
Examination of crop, gizzard, and intestinal contents of chicks fed large numbers of sporulated oocysts indicated that (1) no obvious change in the oocysts occurred in the crop, (2) a high percentage of the sporocysts were quickly released from the oocysts in the gizzard, (3) the sporozoites escaped from the liberated sporocysts in the duodenum and jejunum, and (4) the action of the digestive juice was apparently on the sporocysts rather than on the oocysts.
In vitro attempts to excyst sporozoites from free sporocysts with various pancreatic preparations in the absence of bile produced low or insignificant percentages of excystation. In the presence of bile, bile salts, and other surface-active agents, the action of the pancreatic preparations was greatly increased. The heaviest suspension of motile, nonaggregating sporozoites was obtained with 0.25% trypsin 1–300 in 5% chicken bile at pH 7.6. 相似文献
Examination of crop, gizzard, and intestinal contents of chicks fed large numbers of sporulated oocysts indicated that (1) no obvious change in the oocysts occurred in the crop, (2) a high percentage of the sporocysts were quickly released from the oocysts in the gizzard, (3) the sporozoites escaped from the liberated sporocysts in the duodenum and jejunum, and (4) the action of the digestive juice was apparently on the sporocysts rather than on the oocysts.
In vitro attempts to excyst sporozoites from free sporocysts with various pancreatic preparations in the absence of bile produced low or insignificant percentages of excystation. In the presence of bile, bile salts, and other surface-active agents, the action of the pancreatic preparations was greatly increased. The heaviest suspension of motile, nonaggregating sporozoites was obtained with 0.25% trypsin 1–300 in 5% chicken bile at pH 7.6. 相似文献
8.
THOMAS JÄKEL MARION HENKE BERND WEINGARTEN DAMARIS KLIEMT SILVIA SEIDINGER 《The Journal of eukaryotic microbiology》1997,44(4):293-299
To establish an in vitro culture system for the precystic phase of Sarcocystis singaporensis, we initially tested various excysting fluids for sporocysts. An excysting fluid containing 2.5% bovine taurocholate and 10% bile of the specific intermediate host, Rattus norvegicus, in RPMI medium was the most suitable resulting in excystation of 80% of the sporozoites. Subsequently, we identified brain endothelial cells and pneumonocytes of the rat to promote growth of sporozoites to schizonts. Hepatoma, fibroblastic, or myoblastic cells were not suitable for the parasite's development. First-generation schizonts were seen at days 3-10 postinoculation (PI); a distinct second peak of schizogonic development only occurred in endothelial cells at days 14-18 PI. First-generation schizonts were 26.0 (± 3.8) μm in diameter and contained 32-50 merozoites, second-generation schizonts measured 34.4 (± 10.6) μm and contained 54-72 merozoites. Merozoite yield at large-scale culture conditions (75 cm2 flasks) using pneumonocytes as host cells was relatively low. Ultrastructurally, sporozoites and merozoites were quite similar to corresponding stages of other Sarcocystis species. With regard to host cell specificity and developmental kinetics, in vitro cultivation showed close similarities to the situation in vivo. 相似文献
9.
Abstract 1. In 2004, Brood X of the periodical cicada (Magicicada spp.) emerged in Delaware. Extensive suburban development and concomitant planting of exotic species has occurred since the previous emergence of Brood X in 1987. 2. Exotic species could suffer extensive damage during years of cicada emergences if they are preferred for oviposition. Alternately, a shortage of suitable plant hosts may negatively affect remaining cicada populations. 3. We determined if the periodical cicada, Magicicada septendecim, preferred to oviposit on native or exotic woody plant species. Potential hosts were divided into three groups and planted in a randomised design near a likely source of cicadas. The first group, Natives, included 15 species native to Delaware. The second group, Non‐natives, included 15 exotic species that had a native congener represented in the Native group. The final group, Aliens, included 13 exotic species that did not have a native congener. 4. Based on observations of 428 plants, cicadas were more likely to oviposit on Natives or Non‐natives, which did not differ from each other in this measure, than on Aliens. Non‐natives had more oviposition holes per metre than Natives, which had more holes per metre than Aliens. The likelihood of stem flagging was lowest on Alien species; the percentage of the total plant that flagged was greatest for Natives. Plant morphology also influenced host preference and likelihood of flagging. 5. Taking plant morphology into consideration, we speculate that the evolutionary history between periodical cicadas and potential hosts is an important component of host preference. 相似文献
10.
Variation in bird morphology (notably sex size dimorphism) has been suggested to contribute to differences in food use between individuals. We explore the hypothesis of food partitioning (diet overlap and prey size selection) in two sympatric subspecies of the Great Cormorant Phalacrocorax carbo with respect to bird morphology (subspecies and sex) in inland French waters. These areas represent a recent and increasing contact zone used as a common non-territorial winter feeding area by the continental P. c. sinensis and the marine P. c. carbo subspecies. A high dietary overlap between subspecies and sexes was found at the major sites studied. Prey size selection was found to be site-specific and generally related to a gradient of structural size and body mass (male P. c. carbo > male P. c. sinensis > female P. c. carbo > female P. c. sinensis ). With respect to bird morphology, differences in prey size consumed by Great Cormorants were more pronounced between sexes in freshwater habitats than between subspecies. This was reinforced by the fact that P. c. carbo birds entering inland areas were smaller than birds on the coast. These results also suggest that bird morphology is an important determinant of dietary differences. Our study demonstrated that P. c. carbo is an efficient generalist forager in continental areas, and food partitioning in type and size of prey between the two subspecies is low. 相似文献