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161.
162.
In marine food web studies, stable isotopes of nitrogen (δ15N) and carbon (δ13C) are widely used to estimate organisms’ trophic levels (TL) and carbon sources, respectively. For smaller organisms, whole
specimens are commonly analyzed. However, this “bulk method” involves several pitfalls since different tissues may fractionate
stable isotopes differently. We compared the δ15N and δ13C values of exoskeleton versus soft tissue, in relation to whole specimens, of three common Arctic amphipods in Svalbard waters:
the benthic Anonyx nugax, the sympagic (ice-associated) Gammarus wilkitzkii and the pelagic Themisto libellula. The δ15N values of the exoskeletons were significantly lower than those of the soft tissues for A. nugax (10.5 ± 0.7‰ vs. 15.7 ± 0.7‰), G. wilkitzkii (3.3 ± 0.3‰ vs. 8.3 ± 0.4‰) and T. libellula (8.6 ± 0.3‰ vs.10.8 ± 0.3‰). The differences in δ13C values between exoskeletons and soft tissues were insignificant, except for A. nugax (−21.2 ± 0.2‰ vs. −20.3 ± 0.2‰, respectively). The δ15N values of whole organisms were between those of the exoskeletons and the soft tissues, being similarly enriched in 15N as the exoskeletons (except G. wilkitzkii) and depleted in 15N by 1.2–3.7‰ compared to the soft tissues. The δ15N-derived TLs of the soft tissues agreed best with the known feeding preferences of the three amphipods, which suggest a potential
underestimation of 0.5–1.0 TL when stable isotope analyses are performed on whole crustaceans with thick exoskeletons. The
insignificant or small differences in δ13C values among exoskeletons, soft tissues and whole specimens, however, suggest low probability for misinterpretations of
crustaceans’ primary carbon source in marine ecosystems with distinctly different δ13C-carbon sources. 相似文献
163.
Andersen JP Schwartz A Gramsbergen JB Loeschcke V 《Journal of insect physiology》2006,52(11-12):1163-1170
Dopamine, a catecholamine neurotransmitter, is important for insect development and is known to be involved in insect stress responses. In the current study, dopamine was analysed in Aedes aegypti heads by HPLC. We found that immediately after adult emergence, males have significantly higher concentrations of dopamine than females, and that dopamine concentrations decrease with age in both sexes. Dopamine levels increase in females following a blood meal suggesting that dopamine might be involved in ovarian- and/or egg-development. We also found that female mosquitoes have a higher tolerance to a short term thermal stress in a water bath than males up to 44 degrees C, however, both sexes die if exposed to short term temperatures between 44 and 45 degrees C. Finally, we did not find any indication that dopamine levels were associated with short time thermal stress response in female mosquitoes. 相似文献
164.
Larsen MH Kallipolitis BH Christiansen JK Olsen JE Ingmer H 《Molecular microbiology》2006,61(6):1622-1635
Listeria monocytogenes is a versatile bacterial pathogen that is able to accommodate to diverse environmental and host conditions. Presently, we have identified a L. monocytogenes two-component response regulator, ResD that is required for the repression of virulence gene expression known to occur in the presence of easily fermentable carbohydrates not found inside host organisms. Structurally and functionally, ResD resembles the respiration regulator ResD in Bacillus subtilis as deletion of the L. monocytogenes resD reduces respiration and expression of cydA, encoding a subunit of cytochrome bd. The resD mutation also reduces expression of mptA encoding the EIIABman component of a mannose/glucose-specific PTS system, indicating that ResD controls sugar uptake. This notion was supported by the poor growth of resD mutant cells that was alleviated by excess of selected carbohydrates. Despite the growth deficient phenotype of the mutant in vitro the mutation did not affect intracellular multiplication in epithelial or macrophage cell lines. When examining virulence gene expression we observed traditional induction by charcoal in both mutant and wild-type cells whereas the repression observed in wild-type cells by fermentable carbohydrates did not occur in resD mutant cells. Thus, ResD is a central regulator of L. monocytogenes when present in the external environment. 相似文献
165.
A. R. Khomutov T. A. Keinanen N. A. Grigorenko M. T. Hyvonen A. Uimari M. Pietila M. Cerrada-Gimenez A. R. Simonian M. A. Khomutov J. Vepsalainen L. Alhonen J. Janne 《Molecular Biology》2009,43(2):249-259
Biogenic amines spermine (Spm) and spermidine (Spd) are essential for cell growth. Polyamine analogs are widely used to investigate the enzymes of polyamine metabolism and the functions of spermine and spermidine in vitro and in vivo. It was demonstrated recently that α-methylated derivatives of Spm and Spd are able to fulfill the key cellular functions of polyamines, moreover, in some cases, the effects of (R) and (S) isomers were actually different. Using these α-methylated analogs of Spm and Spd, it turned possible to prevent the development of acute pancreatitis in SSAT-transgenic rats with controllable expression of the Spm/Spd N1-acetyltransferase gene. The analogs made it possible to reveal dormant stereospecificity of polyamine oxidase, Spm oxidase, and deoxyhypusine synthase. An original approach was suggested to regulate the stereospecificity of polyamine oxidase. Depletion of the intracellular polyamine pool was found to have both hypusine-related consequences and consequences unrelated to posttranslational modification of the eukaryotic translation initiation factor eIF5A. Possible applications of a new family of C-methylated polyamine analogs for the investigation and regulation of polyamine metabolism in vitro and in vivo are discussed. 相似文献
166.
167.
Maria Kahlert Raino-Lars Albert Eeva-Leena Anttila Roland Bengtsson Christian Bigler Tiina Eskola Veronika Gälman Steffi Gottschalk Eva Herlitz Amelie Jarlman Jurate Kasperoviciene Mikołaj Kokociński Helen Luup Juha Miettinen Ieva Paunksnyte Kai Piirsoo Isabel Quintana Janne Raunio Bernt Sandell Heikki Simola Irene Sundberg Sirje Vilbaste Jan Weckström 《Journal of applied phycology》2009,21(4):471-482
The goal of this study was a harmonization of diatom identification and counting among diatomists from the Scandinavian and
Baltic countries to improve the comparison of diatom studies in this geographical area. An analysis of the results of 25 diatomists
following the European standard EN 14407 during an intercalibration exercise showed that a high similarity was achieved by
harmonization and not because of a long experience with diatoms. Sources of error were wrong calibration scales, overlooking
of small taxa, especially small Navicula s.l., misidentifications (Eunotia rhomboidea was mistaken for Eunotia incisa) and unclear separation between certain taxa in the identification literature. The latter was discussed during a workshop
with focus on the Achnanthes minutissima group, the separation of Fragilaria capucina var. gracilis from F. capucina var. rumpens, and Nitzschia palea var. palea from N. palea var. debilis. The exercise showed also that the Swedish standard diatom method tested here worked fine with acceptable error for the indices
IPS (Indice de Polluo-sensibilité Spécifique) and ACID (ACidity Index for Diatoms) when diatomists with a low similarity (Bray–Curtis
<60%) with the auditor in at least one of the samples are excluded. 相似文献
168.
Bing He Anne-May
sterholm Anna Hoverflt Carol Forsblom Eyrún Edda Hjrleifsdttir Ann-Sofie Nilsson Maikki Parkkonen Janne Pitkniemi strdur Hreidarsson Cinzia Sarti Amy Jayne McKnight A. Peter Maxwell Jaakko Tuomilehto Per-Henrik Groop Karl Tryggvason 《American journal of human genetics》2009,84(1):5-13
Diabetic nephropathy (DN) is the primary cause of morbidity and mortality in patients with type 1 diabetes mellitus (T1DM) and affects about 30% of these patients. We have previously localized a DN locus on chromosome 3q with suggestive linkage in Finnish individuals. Linkage to this region has also been reported earlier by several other groups. To fine map this locus, we conducted a multistage case-control association study in T1DM patients, comprising 1822 cases with nephropathy and 1874 T1DM patients free of nephropathy, from Finland, Iceland, and the British Isles. At the screening stage, we genotyped 3072 tag SNPs, spanning a 28 Mb region, in 234 patients and 215 controls from Finland. SNPs that met the significance threshold of p < 0.01 at this stage were followed up by a series of sample sets. A genetic variant, rs1866813, in the noncoding region at 3q22 was associated with increased risk of DN (overall p = 7.07 × 10−6, combined odds ratio [OR] of the allele = 1.33). The estimated genotypic ORs of this variant in all Finnish samples suggested a codominant effect, resulting in significant association, with a p value of 4.7 × 10−5 (OR = 1.38; 95% confidence interval = 1.18–1.62). Additionally, an 11 kb segment flanked by rs62408925 and rs1866813, two strongly correlated variants (r2 = 0.95), contains three elements highly conserved across multiple species. Independent replication will clarify the role of the associated variants at 3q22 in influencing the risk of DN. 相似文献
169.
170.
Lepidopterists have long acknowledged that many uncommon butterfly species can be extremely abundant in suitable locations. If this is generally true, it contradicts the general macroecological pattern of the positive interspecific relationship between abundance and distribution, i.e. locally abundant species are often geographically more widespread than locally rare species. Indeed, a negative abundance–distribution relationship has been documented for butterflies in Finland. Here we show, using the Finnish butterflies as an example, that a positive abundance–distribution relationship results if the geographically restricted species are missed, as may be the case in studies based on random or restricted sampling protocols, or in studies that are conducted over small spatial scales. In our case, the abundance–distribution relationship becomes negative when approximately 70 per cent of the species are included. This observation suggests that the abundance–distribution relationship may in fact not be linear over the entire range of distributions. This intriguing possibility combined with some taxonomic biases in the literature may undermine the generalization that for a given taxonomic assemblage there is a positive interspecific relationship between local abundance and regional distribution. 相似文献