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111.
A new low-molecular-weight peptide with phenol oxidase activity, named Pc factor, was isolated and purified from liquid culture
of a white-rot basidiomycete Phanerochaete chrysosporium. Its molecular weight was about 600 Da estimated by gel-filtration. Three amino acids Glu, Gly and Val were detected in hydrolysate.
Absorption peaks corresponding to amino acids and peptide were observed by UV and IR spectra analysis. And the signal of Cα
of amino acid was also detected by 13C-NMR method. Pc factor had high thermostability and remained active in weakly alkalescent pH range. It could chelate Fe3+ and reduce it to Fe2+, but no hydroxyl radical HO˙ could be detected during the reaction process. It could oxidize phenolic lignin-model compounds
such as 2,6-dimethoxyphenol (2,6-DMP), 2,2′-azinobis (3-ethylbenzathiazoline-6-sulfinic acid) (ABTS) and syringaldazine in
the absence of Mn2+ and H2O2. These characteristics differed greatly from those of manganese peroxidases. The oxidative catalysis of Pc factor can be
enhanced by certain metal ions such as Cu2+ and Mn2+ etc., and O2 molecule was necessary for this reaction. In summary, Pc factor may function as an electron carrier in this novel oxidation-reduction
system. 相似文献
112.
We have found that the phenol oxidase activity in 50-hr Drosophila melanogaster pupae is much greater than that of adult flies. The mutants lz and lz
g have all of the phenol oxidase components present in wild type, whereas the mutant tyr-1 has all of the wild-type components but the activity of each component is greatly reduced in comparison with wild-type activity. The newly discovered lozenge allele, lz
rfg, lacks all phenol oxidase activity.Predoctoral fellow supported by Grant GM 1974 from the National Institute of General Medical Sciences, National Institutes of Health.The Oak Ridge National Laboratory is operated for the U.S. Atomic Energy Commission by Union Carbide Corporation. 相似文献
113.
114.
Niche shifts and range expansions along cordilleras drove diversification in a high‐elevation endemic plant genus in the tropical Andes 下载免费PDF全文
The tropical Andes represent one of the world's biodiversity hot spots, but the evolutionary drivers generating their striking species diversity still remain poorly understood. In the treeless high‐elevation Andean environments, Pleistocene glacial oscillations and niche differentiation are frequently hypothesized diversification mechanisms; however, sufficiently densely sampled population genetic data supporting this are still lacking. Here, we reconstruct the evolutionary history of Loricaria (Asteraceae), a plant genus endemic to the Andean treeless alpine zone, based on comprehensive population‐level sampling of 289 individuals from 67 populations across the entire distribution ranges of its northern Andean species. Partly incongruent AFLP and plastid DNA markers reveal that the distinct genetic structure was shaped by a complex interplay of biogeography (spread along and across the cordilleras), history (Pleistocene glacial oscillations) and local ecological conditions. While plastid variation documents an early split or colonization of the northern Andes by at least two lineages, one of which further diversified, a major split in the AFLP data correlate with altitudinal ecological differentiation. This suggests that niche shifts may be important drivers of Andean diversification not only in forest–alpine transitions, but also within the treeless alpine zone itself. The patterns of genetic differentiation at the intraspecific level reject the hypothesized separation in spatially isolated cordilleras and instead suggest extensive gene flow among populations from distinct mountain chains. Our study highlights that leveraging highly variable markers against extensive population‐level sampling is a promising approach to address mechanisms of rapid species diversifications. 相似文献
115.
Hot,humid air decontamination of a C‐130 aircraft contaminated with spores of two acrystalliferous Bacillus thuringiensis strains,surrogates for Bacillus anthracis 下载免费PDF全文
116.
Two Radix spp. (Gastropoda: Lymnaeidae) endemic to thermal springs around Lake Baikal represent ecotypes of the widespread Radix auricularia 下载免费PDF全文
Olga Aksenova Maxim Vinarski Ivan Bolotov Alexander Kondakov Yulia Bespalaya Alyona Tomilova Inga Paltser Mikhail Gofarov 《Journal of Zoological Systematics and Evolutionary Research》2017,55(4):298-309
In this study, we re‐examine two species of freshwater gastropods of the genus Radix Montfort, 1810 (family Lymnaeidae), endemic to the geothermal springs in the Lake Baikal region in the southern part of eastern Siberia — Lymnaea (Radix) hakusyensis Kruglov et Starobogatov, 1989, and Lymnaea (Radix) thermobaicalica Kruglov et Starobogatov, 1989. The alleged species status of these endemics has been re‐assessed by means of an integrative approach combining molecular genetic taxonomy techniques with the traditional methods based on shell and soft body morphology. Phylogenetic reconstructions were made using both mitochondrial (COI) and nuclear (ITS2) DNA markers. We used topotypic samples of both species and specimens sampled from other sites around Lake Baikal. The results demonstrate that the two endemic species are only synonyms of a widespread Holarctic species, Radix auricularia (Linnaeus, 1758), and represent its intraspecific morph (ecotype) adapted to living in thermal springs. A new synonymy is proposed: Thermoradix Kruglov et Starobogatov, 1989 = Radix Montfort, 1810 (syn. n.). 相似文献
117.
Shubing Hou Tianxia Tan Wenxian Du 《Archives Of Phytopathology And Plant Protection》2017,50(9-10):463-472
Botanical insecticides investigation led to 21 compounds from the bark of Juglans mandshurica Maxim., in which, compounds 4, 10, 11, 13, 14 and 15 were isolated from Juglans genus for the first time. The inhibitory effect of dihydrokaempferol (6), naringenin (7) and rhoiptelol C (18) on phenol oxidase (PO) are 5–10 times more than arbutin, a well-known tyrosinase inhibitor. Thus, the selective and effective these inhibitors can be expected for using in the development of environment-friendly pesticide. 相似文献
118.
Dirk Raiser Stephanie Mildner Benedikt Ifland Mohsen Sotoudeh Peter Blöchl Simone Techert Christian Jooss 《Liver Transplantation》2017,7(12)
Understanding and controlling the relaxation process of optically excited charge carriers in solids with strong correlations is of great interest in the quest for new strategies to exploit solar energy. Usually, optically excited electrons in a solid thermalize rapidly on a femtosecond to picosecond timescale due to interactions with other electrons and phonons. New mechanisms to slow down thermalization will thus be of great significance for efficient light energy conversion, e.g., in photovoltaic devices. Ultrafast optical pump–probe experiments in the manganite Pr0.65Ca0.35MnO3, a photovoltaic, thermoelectric, and electrocatalytic material with strong polaronic correlations, reveal an ultraslow recombination dynamics on a nanosecond‐time scale. The nature of long living excitations is further elucidated by photovoltaic measurements, showing the presence of photodiffusion of excited electron–hole polaron pairs. Theoretical considerations suggest that the excited charge carriers are trapped in a hot polaron state. Escape from this state is possible via a slow dipole‐forbidden recombination process or via rare thermal fluctuations toward a conical intersection followed by a radiation‐less decay. The strong correlation between the excited polaron and the octahedral dynamics of its environment appears to be substantial for stabilizing the hot polaron. 相似文献
119.
Yuecun Ma Biao Zhu Zhenzhong Sun Chuang Zhao Yan Yang Shilong Piao 《Journal of Plant Ecology》2014,7(3):240
Aims Nitrogen (N) addition could affect the rate of forest litter and soil organic matter decomposition by regulating extracellular enzyme activity (EEA). The impact of N addition on EEA may differ across different age stands with different organic matter quality. We were interested in whether the impact of N addition on EEA in litter and mineral soil during the growing season was dependent on stand age of a larch plantation in North China.Methods We added three levels of N (0, 20 and 50kg N ha-1 year-1) in three age stands (11, 20 and 45 years old) of Larix principis-rupprechtii plantation in North China. We measured potential activities of β-1,4-glucosidase (BG), cellobiohydrolase (CB), β-1,4-N-acetyl-glucosaminidase (NAG) and phenol oxidase (PO) in litter (organic horizon) and mineral soil (0–10cm) during the second growing season after N amendment. We also measured C and N concentrations, microbial biomass C and N, and KCl-extractable ammonium and nitrate in both litter and mineral soil.Important findings We observed unimodal patterns of EEA during the growing season in all three stands, consistent with the seasonal variations of soil temperature. Stand age had a strong effect on EEA in both litter and mineral soil, and this effect differed between litter and mineral soil as well as between different enzymes. N addition did not significantly affect the activities of BG or CB but significantly suppressed the activity of NAG in litter. We also found stand age-specific responses of PO activity to N addition in both litter and mineral soil. N addition suppressed PO activity of the high C:N ratio litters in 20- and 45-year-old stands but had no significant effect on PO activity of the low C:N ratio litter in 11-year-old stand. Moreover, N addition inhibited PO activity of the high C:N ratio soil in 20-year-old stand but had no significant impact on PO activity of the low C:N ratio soils in 11- and 45-year-old stands. Overall, stand age had a greater effect on EEA in litter and mineral soil compared to 2 years of N addition. Moreover, the effect of N addition on PO activity is stand age dependent, which may affect the long-term soil carbon storage in this forest. 相似文献
120.
Stoichiometry of soil enzyme activity at global scale 总被引:27,自引:0,他引:27
Sinsabaugh RL Lauber CL Weintraub MN Ahmed B Allison SD Crenshaw C Contosta AR Cusack D Frey S Gallo ME Gartner TB Hobbie SE Holland K Keeler BL Powers JS Stursova M Takacs-Vesbach C Waldrop MP Wallenstein MD Zak DR Zeglin LH 《Ecology letters》2008,11(11):1252-1264
Extracellular enzymes are the proximate agents of organic matter decomposition and measures of these activities can be used as indicators of microbial nutrient demand. We conducted a global-scale meta-analysis of the seven-most widely measured soil enzyme activities, using data from 40 ecosystems. The activities of beta-1,4-glucosidase, cellobiohydrolase, beta-1,4-N-acetylglucosaminidase and phosphatase g(-1) soil increased with organic matter concentration; leucine aminopeptidase, phenol oxidase and peroxidase activities showed no relationship. All activities were significantly related to soil pH. Specific activities, i.e. activity g(-1) soil organic matter, also varied in relation to soil pH for all enzymes. Relationships with mean annual temperature (MAT) and precipitation (MAP) were generally weak. For hydrolases, ratios of specific C, N and P acquisition activities converged on 1 : 1 : 1 but across ecosystems, the ratio of C : P acquisition was inversely related to MAP and MAT while the ratio of C : N acquisition increased with MAP. Oxidative activities were more variable than hydrolytic activities and increased with soil pH. Our analyses indicate that the enzymatic potential for hydrolyzing the labile components of soil organic matter is tied to substrate availability, soil pH and the stoichiometry of microbial nutrient demand. The enzymatic potential for oxidizing the recalcitrant fractions of soil organic material, which is a proximate control on soil organic matter accumulation, is most strongly related to soil pH. These trends provide insight into the biogeochemical processes that create global patterns in ecological stoichiometry and organic matter storage. 相似文献