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11.
Kendall MM Wardlaw GD Tang CF Bonin AS Liu Y Valentine DL 《Applied and environmental microbiology》2007,73(2):407-414
Methanogenesis in cold marine sediments is a globally important process leading to methane hydrate deposits, cold seeps, physical instability of sediment, and atmospheric methane emissions. We employed a multidisciplinary approach that combined culture-dependent and -independent analyses with geochemical measurements in the sediments of Skan Bay, Alaska (53 degrees N, 167 degrees W), to investigate methanogenesis there. Cultivation-independent analyses of the archaeal community revealed that uncultivated microbes of the kingdoms Euryarchaeota and Crenarchaeota are present at Skan Bay and that methanogens constituted a small proportion of the archaeal community. Methanogens were cultivated from depths of 0 to 60 cm in the sediments, and several strains related to the orders Methanomicrobiales and Methanosarcinales were isolated. Isolates were psychrotolerant marine-adapted strains and included an aceticlastic methanogen, strain AK-6, as well as three strains of CO(2)-reducing methanogens: AK-3, AK7, and AK-8. The phylogenetic positions and physiological characteristics of these strains are described. We propose a new species, Methanogenium boonei, with strain AK-7 as the type strain. 相似文献
12.
Sanne?Johansson Ulrik?S?chtingEmail author John?A.?Elix Judith?H.?Wardlaw 《Mycological Progress》2005,4(2):139-148
Secondary metabolites from 193 specimens belonging to 15 species of Letrouitia were analyzed by HPLC. Significant quantities of the anthraquinones parietin and fragilin were found in most species and
occasionally minor quantities of emodin, 5-chloroemodin, 7-chloroemodin, 7-chloroteloschistin, 7-chlorofallacinal and 7-chloroparietinic
acid were present. Eight previously unknown lichen substances were identified. A chemotype containing seven new dibenzofurans
(8-chlorodioxocondidymic acid, 8-chlorodioxodidymic acid, 8-chloroxodidymic acid, dioxocondidymic acid, dioxodidymic acid,
letrouitic acid and oxodidymic acid) was found in 3 species. In addition, a chemotype containing four unknowns (possibly chlorodepsidones)
occurred in L. subvulpina. Eight different chemotypes were identified in the genus. The secondary chemistry was important for the precise identification
of some species in Letrouitia. The similarity in secondary chemistry between Letrouitiaceae and Teloschistaceae is not particularly strong, as the shared
compounds are also known to occur in several other lichen families. 相似文献
13.
CCR7 expression and memory T cell diversity in humans 总被引:22,自引:0,他引:22
Campbell JJ Murphy KE Kunkel EJ Brightling CE Soler D Shen Z Boisvert J Greenberg HB Vierra MA Goodman SB Genovese MC Wardlaw AJ Butcher EC Wu L 《Journal of immunology (Baltimore, Md. : 1950)》2001,166(2):877-884
CCR7, along with L-selectin and LFA-1, mediates homing of T cells to secondary lymphoid organs via high endothelial venules (HEV). CCR7 has also been implicated in microenvironmental positioning of lymphocytes within secondary lymphoid organs and in return of lymphocytes and dendritic cells to the lymph after passage through nonlymphoid tissues. We have generated mAbs to human CCR7, whose specificities correlate with functional migration of lymphocyte subsets to known CCR7 ligands. We find that CCR7 is expressed on the vast majority of peripheral blood T cells, including most cells that express adhesion molecules (cutaneous lymphocyte Ag alpha(4)beta(7) integrin) required for homing to nonlymphoid tissues. A subset of CD27(neg) memory CD4 T cells from human peripheral blood is greatly enriched in the CCR7(neg) population, as well as L-selectin(neg) cells, suggesting that these cells are incapable of homing to secondary lymphoid organs. Accordingly, CD27(neg) T cells are rare within tonsil, a representative secondary lymphoid organ. All resting T cells within secondary lymphoid organs express high levels of CCR7, but many activated cells lack CCR7. CCR7 loss in activated CD4 cells accompanies CXC chemokine receptor (CXCR)5 gain, suggesting that the reciprocal expression of these two receptors may contribute to differential positioning of resting vs activated cells within the organ. Lymphocytes isolated from nonlymphoid tissues (such as skin, lung, or intestine) contain many CD27(neg) cells lacking CCR7. The ratio of CD27(neg)/CCR7(neg) cells to CD27(pos)/CCR7(pos) cells varies from tissue to tissue, and may correlate with the number of cells actively engaged in Ag recognition within a given tissue. 相似文献
14.
Effects of latitude, altitude and climate on the habitat and conservation of the endangered butterfly Maculinea arion and its Myrmica ant hosts 总被引:2,自引:1,他引:1
J.A. Thomas D.J. Simcox J.C. Wardlaw G.W. Elmes M.E. Hochberg R.T. Clarke 《Journal of Insect Conservation》1998,2(1):39-46
Analyses were made of the habitats of the endangered myrmecophilous butterfly, Maculinea arion, and its host ant, Myrmica sabuleti, in five regions, spanning most of the climatic range of the butterfly in west Europe. Near their altitudinal or north latitudinal limits, both species are confined to warm south-facing slopes where the turf is grazed <3 cm tall, but at low altitudes further south, where the summer climate is 4°C warmer, the butterfly and ant inhabit ground with any aspect other than south-facing, and the butterfly is restricted to swards >20 cm tall. Intermediate types of habitat were used in regions with intermediate summer climates. The implications for conservation management are discussed. The fact that M. arion has a narrow niche and occupies very early successional stages near its range-edge makes it difficult to conserve in regions with cool climates. A successful example is described from one site in the UK. During 20 years of intensive management the sward structure was altered from being tall and dense to that predicted as optimal for M. arion at its range-edge. The species of Myrmica changed greatly during this period, with thermophilous ants, including M. sabuleti, supplanting cool-loving non-host species. A population of M. arion now inhabits this site. We predict that the conservation of M. arion will be easier and cheaper to achieve under the warm climates of central lowland Europe where different, less intensive, management is required. © Rapid Science Ltd. 1998 相似文献
15.
Partially Redundant Enhancers Cooperatively Maintain Mammalian Pomc Expression Above a Critical Functional Threshold 总被引:1,自引:0,他引:1
16.
Ren H Orozco IJ Su Y Suyama S Gutiérrez-Juárez R Horvath TL Wardlaw SL Plum L Arancio O Accili D 《Cell》2012,149(6):1314-1326
Hypothalamic neurons expressing Agouti-related peptide (AgRP) are critical for initiating food intake, but druggable biochemical pathways that control this response remain elusive. Thus, genetic ablation of insulin or leptin signaling in AgRP neurons is predicted to reduce satiety but fails to do so. FoxO1 is a shared mediator of both pathways, and its inhibition is required to induce satiety. Accordingly, FoxO1 ablation in AgRP neurons of mice results in reduced food intake, leanness, improved glucose homeostasis, and increased sensitivity to insulin and leptin. Expression profiling of flow-sorted FoxO1-deficient AgRP neurons identifies G-protein-coupled receptor Gpr17 as a FoxO1 target whose expression is regulated by nutritional status. Intracerebroventricular injection of Gpr17 agonists induces food intake, whereas Gpr17 antagonist cangrelor curtails it. These effects are absent in Agrp-Foxo1 knockouts, suggesting that pharmacological modulation of this pathway has therapeutic potential to treat obesity. 相似文献
17.
Introduction
Low muscle mass secondary to disease and ageing is an important cause of excess mortality and morbidity. Many studies include a MR brain scan but no peripheral measure of muscle mass. We developed a technique to measure posterior neck muscle cross-sectional area (CSA) on volumetric MR brain scans enabling brain and muscle size to be measured simultaneously.Methods
We performed four studies to develop and test: feasibility, inter-rater reliability, repeatability and external validity. We used T1-weighted MR brain imaging from young and older subjects, obtained on different scanners, and collected mid-thigh MR data.Results
After developing the technique and demonstrating feasibility, we tested it for inter-rater reliability in 40 subjects. Intraclass correlation coefficients (ICC) between raters were 0.99 (95% confidence intervals (CI) 0.98–1.00) for the combined group (trapezius, splenius and semispinalis), 0.92 (CI 0.85–0.96) for obliquus and 0.92 (CI 0.85–0.96) for sternocleidomastoid. The first unrotated principal component explained 72.2% of total neck muscle CSA variance and correlated positively with both right (r = 0.52, p = .001) and left (r = 0.50, p = .002) grip strength. The 14 subjects in the repeatability study had had two MR brain scans on three different scanners. The ICC for between scanner variation for total neck muscle CSA was high at 0.94 (CI 0.86–0.98). The ICCs for within scanner variations were also high, with values of 0.95 (CI 0.86–0.98), 0.97 (CI 0.92–0.99) and 0.96 (CI 0.86–0.99) for the three scanners. The external validity study found a correlation coefficient for total thigh CSA and total neck CSA of 0.88.Discussion
We present a feasible, valid and reliable method for measuring neck muscle CSA on T1-weighted MR brain scans. Larger studies are needed to validate and apply our technique with subjects differing in age, ethnicity and geographical location. 相似文献18.
The behavioural interactions between caterpillars of Maculinea rebeli Hir. and their Myrmica ant hosts were studied, both in the wild at the time of adoption, and inside captive nests of six Myrmica species.
In the wild, freshly moulted, final instar caterpillars left their food-plants at a time of day that coincided with the peak foraging activity of Myrmica (18:00-20:00 h). Once on the ground, caterpillars made no attempt to search for Myrmica but settled and waited for foraging ants to find them, which took up to 1.5 h. There was no adoption ritual: foragers of any Myrmica species picked up the caterpillars within 1–4 sec of discovery, and carried them directly to their nests.
Caterpillars grew from < 2 mg to 110 mg in laboratory ant-nests. About 60 mg was gained in autumn but 40% of this was lost during the winter, while the temperature was < 14 °C. Although caterpillars survived best with their normal host, Myrmica schencki , they could also survive in the nests of other Myrmica species. The presence of queen ants had no effect upon survival. The behaviour of the caterpillars was described and illustrated: this included the production of secretions that were drunk by the ants, begging for food and direct feeding by ants. The preferred solid food was ant eggs.
The results are discussed in terms of the social biology of Myrmica ants. It is hypothesized that Maculinea rebeli caterpillars mimic the touch pheromones of ant worker-larvae. This would explain the inability of ants to recognize caterpillars before touching them, their immediate adoption by any Myrmica species after discovery, host specificity inside wild ant-nests, the absence of queen-effect and the intimate attention of host workers. 相似文献
In the wild, freshly moulted, final instar caterpillars left their food-plants at a time of day that coincided with the peak foraging activity of Myrmica (18:00-20:00 h). Once on the ground, caterpillars made no attempt to search for Myrmica but settled and waited for foraging ants to find them, which took up to 1.5 h. There was no adoption ritual: foragers of any Myrmica species picked up the caterpillars within 1–4 sec of discovery, and carried them directly to their nests.
Caterpillars grew from < 2 mg to 110 mg in laboratory ant-nests. About 60 mg was gained in autumn but 40% of this was lost during the winter, while the temperature was < 14 °C. Although caterpillars survived best with their normal host, Myrmica schencki , they could also survive in the nests of other Myrmica species. The presence of queen ants had no effect upon survival. The behaviour of the caterpillars was described and illustrated: this included the production of secretions that were drunk by the ants, begging for food and direct feeding by ants. The preferred solid food was ant eggs.
The results are discussed in terms of the social biology of Myrmica ants. It is hypothesized that Maculinea rebeli caterpillars mimic the touch pheromones of ant worker-larvae. This would explain the inability of ants to recognize caterpillars before touching them, their immediate adoption by any Myrmica species after discovery, host specificity inside wild ant-nests, the absence of queen-effect and the intimate attention of host workers. 相似文献
19.
20.