全文获取类型
收费全文 | 136篇 |
免费 | 2篇 |
专业分类
138篇 |
出版年
2016年 | 3篇 |
2015年 | 2篇 |
2012年 | 7篇 |
2011年 | 2篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 3篇 |
2007年 | 11篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2002年 | 2篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1972年 | 3篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1953年 | 3篇 |
1952年 | 2篇 |
1951年 | 2篇 |
1950年 | 1篇 |
1949年 | 1篇 |
排序方式: 共有138条查询结果,搜索用时 15 毫秒
71.
ALLAN PENTECOST FRANCIS ROSE 《Botanical journal of the Linnean Society. Linnean Society of London》1985,90(3):217-230
The cryptogam flora of 15 sandrock sites in the central Weald, U.K. was assessed and compared with previous records beginning in 1688. A total of 264 species was recorded (29 algae, 90 lichens, 165 bryophytes and eight ferns) of which 18 lichens, 21 bryophytes and one fern were not relocated. Air pollution, changes in the microclimate brought about by invasion of trees and shrubs and trampling appear to be the main cause for the decline in the flora, although over-collection of rarities was also a factor. 相似文献
72.
Assessing the impacts of wind farms on birds 总被引:6,自引:1,他引:5
The potential effects of the proposed increase in wind energy developments on birds are explored using information from studies of existing wind farms. Evidence of the four main effects, collision, displacement due to disturbance, barrier effects and habitat loss, is presented and discussed. The consequences of such effects may be direct mortality or more subtle changes to condition and breeding success. The requirements for assessing the impact of future developments are summarized, including relevant environmental legislation and appropriate methods for undertaking baseline surveys and post-construction monitoring, with particular emphasis on the rapidly developing area of offshore wind farm assessments. Mitigation measures which have the potential to minimize impacts are also summarized. Finally, recent developments in the monitoring and research of wind energy impacts on birds are outlined and some areas for future work are described. 相似文献
73.
It has previously been proposed that saccharin has a dual tasefor the rat, that is has both sweet and aversive componentsto its taste, and that the aversion shown to saccharin by alloxandiabetic rats might be accounted for by the diabetes reducingthe effectiveness of the sweet component. In this study it isshown that the generalization to saccharin of a conditionedaversion to glucose is reduced or eliminated following alloxantreatment suggesting that the sweet component is reduced, andthat the generalization of a conditioned aversion to quinineis enhanced suggesting that the second component of the saccharintaste is quinine-like.
* Supported by National Research Council of Canada Grant #APO-97 相似文献
74.
In comparison with nitrate nutrition,ammonium nutrition increases growth of the frostbite1 Arabidopsis mutant 下载免费PDF全文
ANNA PODGÓRSKA MONIKA OSTASZEWSKA PER GARDESTRÖM ALLAN G. RASMUSSON BOŻENA SZAL 《Plant, cell & environment》2015,38(1):224-237
Ammonium nutrition inhibits the growth of many plant species, including Arabidopsis thaliana. The toxicity of ammonium is associated with changes in the cellular redox state. The cellular oxidant/antioxidant balance is controlled by mitochondrial electron transport chain. In this study, we analysed the redox metabolism of frostbite1 (fro1) plants, which lack mitochondrial respiratory chain complex I. Surprisingly, the growth of fro1 plants increased under ammonium nutrition. Ammonium nutrition increased the reduction level of pyridine nucleotides in the leaves of wild‐type plants, but not in the leaves of fro1 mutant plants. The observed higher activities of type II NADH dehydrogenases and cytochrome c oxidase in the mitochondrial electron transport chain may improve the energy metabolism of fro1 plants grown on ammonium. Additionally, the observed changes in reactive oxygen species (ROS) metabolism in the apoplast may be important for determining the growth of fro1 under ammonium nutrition. Moreover, bioinformatic analyses showed that the gene expression changes in fro1 plants significantly overlap with the changes previously observed in plants with a modified apoplastic pH. Overall, the results suggest a pronounced connection between the mitochondrial redox system and the apoplastic pH and ROS levels, which may modify cell wall plasticity and influence growth. 相似文献
75.
JUSTIN D. DERNER HYRUM B. JOHNSON† BRUCE A. KIMBALL‡ PAUL J. PINTER Jr ‡ H. Wayne POLLEY† CHARLES R. TISCHLER† THOMAS W. BOUTTON§ ROBERT L. LAMORTE‡ GERALD W. WALL‡ NEIL R. ADAM‡ STEVEN W. LEAVITT¶ MICHAEL J. OTTMAN ALLAN D. MATTHIAS†† TALBOT J. BROOKS‡‡ 《Global Change Biology》2003,9(3):452-460
We evaluated the influences of CO2[Control, ~ 370 µ mol mol ? 1; 200 µ mol mol ? 1 above ambient applied by free‐air CO2 enrichment (FACE)] and soil water (Wet, Dry) on above‐ and below‐ground responses of C3 (cotton, Gossypium hirsutum) and C4 (sorghum, Sorghum bicolor) plants in monocultures and two density mixtures. In monocultures, CO2 enrichment increased height, leaf area, above‐ground biomass and reproductive output of cotton, but not sorghum, and was independent of soil water treatment. In mixtures, cotton, but not sorghum, above‐ground biomass and height were generally reduced compared to monocultures, across both CO2 and soil water treatments. Density did not affect individual plant responses of either cotton or sorghum across the other treatments. Total (cotton + sorghum) leaf area and above‐ground biomass in low‐density mixtures were similar between CO2 treatments, but increased by 17–21% with FACE in high‐density mixtures, due to a 121% enhancement of cotton leaf area and a 276% increase in biomass under the FACE treatment. Total root biomass in the upper 1.2 m of the soil was not influenced by CO2 or by soil water in monoculture or mixtures; however, under dry conditions we observed significantly more roots at lower soil depths ( > 45 cm). Sorghum roots comprised 81–85% of the total roots in the low‐density mixture and 58–73% in the high‐density mixture. CO2‐enrichment partly offset negative effects of interspecific competition on cotton in both low‐ and high‐density mixtures by increasing above‐ground biomass, with a greater relative increase in the high‐density mixture. As a consequence, CO2‐enrichment increased total above‐ground yield of the mixture at high density. Individual plant responses to CO2 enrichment in global change models that evaluate mixed plant communities should be adjusted to incorporate feedbacks for interspecific competition. Future field studies in natural ecosystems should address the role that a CO2‐mediated increase in C3 growth may have on subsequent vegetation change. 相似文献
76.
NORMAN SARTORIUS WOLFGANG GAEBEL HELEN‐ROSE CLEVELAND HEATHER STUART TSUYOSHI AKIYAMA JULIO ARBOLEDA‐FLÓREZ ANJA E. BAUMANN OYE GUREJE MIGUEL R. JORGE MARIANNE KASTRUP YURIKO SUZUKI ALLAN TASMAN 《World psychiatry》2010,9(3):131-144
In 2009 the WPA President established a Task Force that was to examine
available evidence about the stigmatization of psychiatry and psychiatrists
and to make recommendations about action that national psychiatric societies
and psychiatrists as professionals could do to reduce or prevent the stigmatization
of their discipline as well as to prevent its nefarious consequences. This
paper presents a summary of the Task Force’s findings and recommendations.
The Task Force reviewed the literature concerning the image of psychiatry
and psychiatrists in the media and the opinions about psychiatry and psychiatrists
of the general public, of students of medicine, of health professionals other
than psychiatrists and of persons with mental illness and their families.
It also reviewed the evidence about the interventions that have been undertaken
to combat stigma and consequent discrimination and made a series of recommendations
to the national psychiatric societies and to individual psychiatrists. The
Task Force laid emphasis on the formulation of best practices of psychiatry
and their application in health services and on the revision of curricula
for the training of health personnel. It also recommended that national psychiatric
societies establish links with other professional associations, with organizations
of patients and their relatives and with the media in order to approach the
problems of stigma on a broad front. The Task Force also underlined the role
that psychiatrists can play in the prevention of stigmatization of psychiatry,
stressing the need to develop a respectful relationship with patients, to
strictly observe ethical rules in the practice of psychiatry and to maintain
professional competence. 相似文献
77.
RICK ROSATTE KIRK SOBEY DENNIS DONOVAN MIKE ALLAN LAURA BRUCE TORE BUCHANAN CHRIS DAVIES 《The Journal of wildlife management》2007,71(7):2373-2378
ABSTRACT Population reduction (PR) and trap-vaccinate-release (TVR) were used to control an outbreak of the raccoon (Procyon lotor) variant of rabies in Ontario, Canada, during 1999. Raccoon density declined significantly following PR; however, density increased significantly 9–10 months post-PR. Recolonization of PR areas with raccoons marked in TVR areas was very low with only 1.8% (32/1,759) of those raccoons dispersing into PR areas during 1999–2000. In addition, the number of raccoons dispersing from TVR areas into PR areas was not significantly greater than the number of raccoons dispersing into treatment areas where population reduction had not been implemented during 1999–2000. Raccoon movements in this study, determined by mark-recapture, averaged < 4.0 km during 1999–2000 and did not differ among treatments (with or without PR). In summary, there was not a mass exodus of raccoons from TVR areas to PR areas during 1999–2000, suggesting there was not an immediate, dramatic, vacuum effect drawing raccoons into areas devoid of raccoons due to PR. However, one year post-PR, raccoon populations were near or above pre-PR densities (due to a high reproductive rate of resident raccoons), suggesting that PR would have to be an annual event if rabies is not eliminated from an area. 相似文献
78.
TILMAN J. ALPERMANN BÁNK BESZTERI UWE JOHN URBAN TILLMANN ALLAN D. CEMBELLA 《Molecular ecology》2009,18(10):2122-2133
Genotypic or phenotypic markers for characterization of natural populations of marine microalgae have typically addressed questions regarding differentiation among populations, usually with reference to a single or few clonal isolates. Based upon a large number of contemporaneous isolates from the same geographical population of the toxigenic species Alexandrium tamarense from the North Sea, we uncovered significant genetic substructure and low but significant multilocus linkage disequilibrium (LD) within the planktonic population. Between the alternative molecular genotyping approaches, only amplified fragment length polymorphism (AFLP) revealed cryptic genetic population substructure by Bayesian clustering, whereas microsatellite markers failed to yield concordant patterns. Both markers, however, gave evidence for genetic differentiation of population subgroups as defined by AFLP. A considerable portion of multilocus LD could be attributed to population subdivision. The remaining LD within population subgroups is interpreted as an indicator of frequency shifts of clonal lineages during vegetative growth of planktonic populations. Phenotypic characters such as cellular content and composition of neurotoxins associated with paralytic shellfish poisoning (PSP) and allelochemical properties may contribute to intra- or inter-annual differentiation of planktonic populations, if clonal lineages that express these characters are selectively favoured. Nevertheless, significant phenotypic differentiation for these characters among the genetically differentiated subgroups was only detected for PSP toxin content in two of the four population subgroups. By integrating the analysis of phenotypic and genotypic characteristics, we developed a conceptual population genetic model to explain the importance of life-cycle dynamics and transitions in the evolutionary ecology of these dinoflagellates. 相似文献
79.
D. SNYDER N. CERNICCHIARO S. A. ALLAN L. W. COHNSTAEDT 《Medical and veterinary entomology》2016,30(2):209-217
The mixing of an insecticide with sugar solution creates an oral toxin or insecticidal sugar bait (ISB) useful for reducing adult insect populations. The ability of ISBs to kill the biting midge Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae), a vector of bluetongue virus, epizootic hemorrhagic disease and vesicular stomatitis viruses, was tested. The commercial insecticide formulations (percentage active ingredient) tested included bifenthrin, cyfluthrin, deltamethrin, permethrin, dinotefuran, imidacloprid, thiamethoxam and spinosad. Mortality rates were determined for various concentrations of commercial formulations (0.01, 0.05, 0.1, 1, 2 and 3%) and observed at 1, 4, 10 and 24 h post‐exposure to the ISB. In the first set of assays, laboratory‐reared midges were fed sugar ad libitum and then exposed to insecticide‐treated sugar solutions to measure mortality. The second assay assessed competitive feeding: midges were provided with a control sugar solution (10% sucrose) in one vial, and a sugar and insecticide solution in another. Pyrethroid treatments resulted in the greatest mortality in the first hour at the lowest concentrations and spinosad consumption resulted in the least mortality. Biting midges were not deterred from feeding on the 1% ISB solutions despite the presence of an insecticide‐free alternative source of sugar. 相似文献
80.
SANDRA A. ALLAN NICOLAS BARRÉ DANIEL E. SONENSHINE & MICHAEL J. BURRIDGE 《Medical and veterinary entomology》1998,12(2):141-150
The efficacy of tags impregnated with pheromone and acaricide for control of Amblyomma variegatum on cattle in Guadeloupe was determined for a 13-week trial. Comparisons were made between untreated cattle and cattle with tags containing either pheromones alone (o-nitrophenol, methyl salicylate, 2,6-dichlorophenol and phenylacetaldehyde), pheromones plus acaricide (cyfluthrin or deltamethrin), or acaricide alone. Tags were fastened to cattle both on collars on the neck and with adhesive to tail hairs, with over 98 and 90% of tags retained, respectively, during the trial. By the end of the trial, tick infestations increased on untreated cattle (311.7%) and cattle with pheromone tags (154.8%) but decreased on cattle with pheromone/cyfluthrin (–45.0%), cyfluthrin (–42.8%), pheromone/deltamethrin (–68.7%) and deltamethrin tags (–87.6%). Cattle with pheromone tags had greater proportions of ticks on the hind regions (81%) compared to untreated cattle (62.5%) and on the front regions (18.2%) compared to untreated cattle (8.2%) indicating that ticks aggregated in response to pheromones. Analysis of hair samples by gas chromatography indicated that, within 2 days of placement, cyfluthrin spread rapidly over the body from the tags. Both cyfluthrin and deltamethrin were present in detectable levels on all eight body regions examined throughout the trial. Analysis of the tags indicated that they all still contained pheromone components after 13 weeks under field conditions. 相似文献