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71.
Grass lignocelluloses, such as those in corn and switchgrass, are a major resource in the emerging cellulose-to-ethanol strategy
for biofuels. The potential bioconversion of carbohydrates in this potential resource, however, is limited by the associated
aromatic constituents within the grass fiber. These aromatics include both lignins, which are phenylpropanoid units of various
types, and low-molecular weight phenolic acids. Structural and chemical studies over the years have identified the location
and limitation to fiber degradation imposed by a variety of these aromatic barriers. For example, coniferyl lignin appears
to be the most effective limitation to biodegradation, existing in xylem cells of vascular tissues. On the other hand, cell
walls with syringyl lignin, e.g., leaf sclerenchyma, are often less recalcitrant. Ferulic and p-coumaric acids that are esterified to hemicellulosic sugars constitute a major limitation to biodegradation in non-lignified
cell walls in grass fibers, especially warm season species. Non-chemical methods to improve bioconversion of the lignocelluloses
through modification of aromatics include: (1) use of lignin-degrading white rot fungi, (2) pretreatment with phenolic acid
esterases, and (3) plant breeding to modify cell wall aromatics. In addition to increased availability of carbohydrates for
fermentation, separation and collection of aromatics could provide value-added co-products to improve the economics of bioconversion.
JIMB-2008: BioEnergy—Special issue. 相似文献
72.
Bacteroides ovatus is a Gram-negative obligate anaerobe that was isolated from the human colon and is capable of utilizing xylan. The objective
of this study was to evaluate the ability of B. ovatus V975 to digest maize bran, oat bran, and wheat bran as well as the isolated cell walls from each bran source. Strain V975
was incubated in basal medium that contained either 0.1 or 0.3 g of each bran or each bran cell wall for 0, 24, 48, and 72
h. Acetate and succinate were the main products detected from each fermentation; however, less of each end product was produced
from the isolated cell walls than from each bran. More of the oat bran was digested (in vitro dry matter disappearance = 74.8%)
during the 72 h incubation than any other bran source. While each bran contained arabinose and xylose, more glucose, galactose,
and mannose were utilized by strain V975 during the 72-h incubation than either pentose sugar. Compared with each bran, the
bran cell walls had lower concentrations of most sugars, and more glucose than any other sugar was utilized by strain V975.
These results suggest that strain V975 preferentially utilizes glucose, galactose, and mannose in each bran, while glucose
is the main sugar fermented in bran cell walls.
Received: 19 June 1997 / Accepted: 31 July 1997 相似文献
73.
Oluwatosin Gbemisola Oladipo Olusegun Olufemi Awotoye Akin Olayinka Obinna Tobechukwu Ezeokoli Mark Steve Maboeta Cornelius Carlos Bezuidenhout 《Bioremediation Journal》2016,20(4):287-297
Increased heavy metal pollution generated through anthropogenic activities into the environment has necessitated the need for eco-friendly remediation strategies such as mycoremediation. With a view to prospecting for fungi with heavy metal remediation potentials, the tolerance of five Aspergillus species isolated from soils of three active gold and gemstone mining sites in southwestern Nigeria to varied heavy metal concentrations was investigated. Isolated Aspergillus strains were identified based on the internal transcribed spacer 1 and 2 (ITS 1 and ITS 2) regions. Growth of Aspergillus strains were challenged with a range of varied concentrations of heavy metals: cadmium (Cd) (0–100), copper (Cu) (0–1000), lead (Pb) (0–400), arsenic (As) (0–500), and iron (Fe) (0–800) concentrations (ppm) incorporated into Malt Extract Agar (MEA) in triplicates. Mycelial radial growths were recorded at intervals of 3 days during a 13-day incubation period. Aspergillus strains were identified as A. tubingensis, A. fumigatus, A. terreus, A. nidulans, and A. nomius. A. tubingensis tolerated Cd, Cu, Pb, As, and Fe at all test concentrations (100–1000 ppm), showing no significant (p > .05) difference compared with the control. Similarly, A. nomius tolerated all concentrations of Cu, Pb, As, and Fe and only 50 ppm Cd concentrations. A. nidulans, A. terreus, and A. fumigatus, on the other hand, tolerated all concentrations of Cu, Pb, and Fe with no statistical significance (p > .05) difference from the controls. Overall, the Aspergillus species showed tolerance to heavy metal concentrations above permissible limits for contaminated soils globally. These heavy metal tolerance traits exhibited by the Aspergillus isolates may suggest that they are potential candidates for bioremediation of heavy metal–polluted environments. 相似文献
74.
75.
Aydin Ece Bekir Sami Uyamik Akin IŞcan Pelin Ertan M. Ramazan Yiğitolu 《Biological trace element research》1997,59(1-3):31-39
In order to evaluate serum copper and zinc status in children with iron deficiency anemia (IDA), 60 children with IDA aged
1–14 yr and 64 healthy children as controls aged 1–14 yr were included the study. Serum copper levels were higher in children
with IDA (189 ± 49 (Μg/dL) than those of controls (163 ± 37 Μg/dL) (p = 0.001). Serum zinc levels were lower in the patient group (109 ± 59 Μg/dL) than those of control subjects (135 ± 56 Μg/dL)
(p = 0.017). In addition, there were statistically significant negative correlations between hematological parameters and serum
copper levels in the patient group, but not in controls. No correlation between hematological parameters and serum zinc levels
were found in both patient and control groups, except positive correlation between mean corpuscular volume (MCV) and serum
zinc level in patients.
It was concluded that at the time of managing children with IDA, zinc deficiency must be borne in mind and if necessary treatment
should be initiated with zinc. 相似文献
76.
77.
Brandy L. Akin Thomas D. Hurley Zhenhui Chen Larry R. Jones 《The Journal of biological chemistry》2013,288(42):30181-30191
P-type ATPases are a large family of enzymes that actively transport ions across biological membranes by interconverting between high (E1) and low (E2) ion-affinity states; these transmembrane transporters carry out critical processes in nearly all forms of life. In striated muscle, the archetype P-type ATPase, SERCA (sarco(endo)plasmic reticulum Ca2+-ATPase), pumps contractile-dependent Ca2+ ions into the lumen of sarcoplasmic reticulum, which initiates myocyte relaxation and refills the sarcoplasmic reticulum in preparation for the next contraction. In cardiac muscle, SERCA is regulated by phospholamban (PLB), a small inhibitory phosphoprotein that decreases the Ca2+ affinity of SERCA and attenuates contractile strength. cAMP-dependent phosphorylation of PLB reverses Ca2+-ATPase inhibition with powerful contractile effects. Here we present the long sought crystal structure of the PLB-SERCA complex at 2.8-Å resolution. The structure was solved in the absence of Ca2+ in a novel detergent system employing alkyl mannosides. The structure shows PLB bound to a previously undescribed conformation of SERCA in which the Ca2+ binding sites are collapsed and devoid of divalent cations (E2-PLB). This new structure represents one of the key unsolved conformational states of SERCA and provides a structural explanation for how dephosphorylated PLB decreases Ca2+ affinity and depresses cardiac contractility. 相似文献
78.
Emel akmak dem Akin Peken Changr Krazli Elf Yama Staffan Bensch Cemal Can Blgn 《Ibis》2019,161(4):793-805
Vulture populations worldwide have suffered precipitous declines in recent decades. The Cinereous Vulture Aegypius monachus, a highly philopatric scavenger distributed across southern Europe and the central Asian plateau, is threatened in many parts of its range. Turkey holds the second largest population of this species in the Western Palaearctic, but there has been no research on its genetic structure and the possible implications of this structure for the future of the species. Here we report nuclear diversity and relatedness determined by short tandem repeat genotyping of 81 individuals from the four largest colonies. Our results demonstrated no significant genetic structuring, suggesting a single panmictic metapopulation connected by frequent dispersal. Furthermore, we show that the study population has retained moderate levels of genetic diversity, despite passing through a recent demographic bottleneck. We estimated the effective population size to be 112 individuals (95% confidence interval 74–201). Our results imply that the observed lack of increase in population size since the 1990s has not been caused by lowered fitness due to genetic inbreeding but rather by increased mortality via demographic processes. In the short term, we suggest that conservation efforts should treat the Turkish subpopulations as a single management unit and aim to increase population size through effective protection, especially during the breeding season. 相似文献
79.
Summary Orchid bees (Euglossini) provide a potentially informative contrast for examining origins of advanced social behaviour in bees because they are the only tribe in the apine clade that do not form large colonies or have queens and workers. We investigated natural nests of Euglossa hyacinthina Dressler, an orchid bee that nests singly or in groups. By comparing the two types of nests, we examined if individuals in a group merely share the nest (are communal) or exhibit a level of social organization where there is reproductive division of labour among the females. Observations are consistent with communal nesting, indicating that all females in group nests are reproductively similar to the solitary nesting females because the provisioning of young, as well as the ovary development and mating status of females sharing nests were not different than that of solitary-nesting females. Also, multiple female nests did not produce a female-biased brood as predicted for nests with reproductive division of labour. We also investigated potential advantages of group nesting vs. individual nesting. We demonstrate that per capita offspring production is lower in nests with more than one female. However, we found that nests with single females were left unattended for longer periods of time during foraging, and that there was a high incidence of natural enemy attack in nests when females were absent. Group and solitary nesting may be advantageous under different conditions.Received 3 December 2002; revised 7 March 2003; accepted 2 April 2003. 相似文献
80.
Jared A. Niska Jeffrey A. Meganck Jonathan R. Pribaz Jonathan H. Shahbazian Ed Lim Ning Zhang Brad W. Rice Ali Akin Romela Irene Ramos Nicholas M. Bernthal Kevin P. Francis Lloyd S. Miller 《PloS one》2012,7(10)