全文获取类型
收费全文 | 893篇 |
免费 | 41篇 |
专业分类
934篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 14篇 |
2018年 | 40篇 |
2017年 | 42篇 |
2016年 | 50篇 |
2015年 | 50篇 |
2014年 | 67篇 |
2013年 | 77篇 |
2012年 | 84篇 |
2011年 | 83篇 |
2010年 | 53篇 |
2009年 | 29篇 |
2008年 | 31篇 |
2007年 | 53篇 |
2006年 | 51篇 |
2005年 | 40篇 |
2004年 | 40篇 |
2003年 | 34篇 |
2002年 | 21篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
排序方式: 共有934条查询结果,搜索用时 24 毫秒
11.
Joanna Suliburska Paweł Bogdański Danuta Pupek-Musialik Zbigniew Krejpcio 《Biological trace element research》2011,139(2):137-150
Inadequate minerals intake, as well as disruption of some metabolic processes in which microelements are cofactors, are suggested
to lead to the development of hypertension. The role of minerals in the pathogenesis of hypertension still remains to be explained.
In the present study, we sought to determine associations between serum and hair mineral concentrations and serum lipids and
glucose levels. Forty obese hypertensive subjects with insulin resistance and 40 healthy volunteers were recruited in the
study. Blood pressure, BMI, and insulin resistance were recorded in all subjects. Levels of lipids, glucose, sodium and potassium,
iron, copper, zinc, magnesium, and calcium were assessed in serum. Iron, copper, zinc, magnesium, and calcium were assessed
in hair. Dietary intake of the analyzed minerals was estimated. We found distinctly higher concentrations of serum iron and
serum and hair calcium as well as markedly lower levels of hair zinc in the hypertensive subjects. The study group manifested
also significantly lower daily intake of calcium, magnesium, and iron. We observed a relationship between the concentrations
of iron, zinc, and copper in serum and hair and high and low range of cholesterol, triglycerides, and glucose serum levels
in the studied patients. Moreover, this study demonstrated significant correlation between serum and hair concentrations of
selected minerals and their dietary intake and levels of serum lipids and glucose and blood pressure in the study and the
control groups. The obtained results seem to indicate the association between lipid and glucose metabolism and iron, copper,
zinc, and calcium concentrations in blood and hair of hypertensive and obese patients with insulin resistance. 相似文献
12.
13.
Valery A. Isidorov Paweł Lech Anna Żółciak Magdalena Rusak Lech Szczepaniak 《Trees - Structure and Function》2008,22(4):531-542
An investigation was carried out of the composition of metabolites in pine seedlings tissues at the initial stages of the
infectious process caused by pathogenic fungi Armillaria ostoyae, which causes a root rot of trees and degradation of forest resources. With the help of successive extraction with organic
solvents of different polarity, more than 190 metabolites were extracted from the needles and roots of the seedlings and then
identified by GC–MS method. The composition of the extracts from control plants and those inoculated with Armillaria ostoyae were compared. It was established that part of secondary metabolites (glucosamines and free amino acids, carbohydrates raffinose
and trehalose) were present only in the tissues of inoculated plants. Possible roles of some of these compounds appearing
in the roots of seedlings infected with the fungus are also discussed in the paper. 相似文献
14.
15.
Recently published biochemical data suggest the significant role of selenium compounds as the adjuvants combined with L: -thyroxine therapy, which can reduce antithyroid peroxidase antibodies' (TPOAb) levels in patients with Hashimoto disease. The study was undertaken to document in a more detailed way the changes in parameters expressing the thyroid and ovarian function brought about by selenium supplementation (50-100 microg/day) in a woman undergoing autoimmune thyroiditis (AIT) therapy. This prospective observational case study lasted for 14 months plus additional 5 months as a follow-up period. Parameters reflecting selenium status, thyroid metabolism, and sex hormones secretion were determined at the onset and end of the study period, as well as in some of its middle points. During the supplementation trial, serum selenium (Se) increased by 45% and plasma glutathione peroxidase (GPX3) by 21%. TPOAb decreased by 76%. All other parameters also fluctuated during the supplementation period, but all results were always within normal physiological ranges. After withdrawal of the supplementation, the sharp fall of Se and GPX3 promptly occurred, and this phenomenon was accompanied with a marked increase in TPOAb. This report stresses the importance of selenium supplementation in AIT treatment. However, the efficiency and durability of the effect of Se supplementation on the TPOAb titer remain an open question. The clarification of mechanism(s) underlying Se interaction with autoimmune processes should throw new light on this issue. 相似文献
16.
Karolina Krystkowiak Monika Langner Tadeusz Adamski Bolesław P. Salmanowicz Zygmunt Kaczmarek Paweł Krajewski Maria Surma 《Journal of applied genetics》2017,58(1):37-48
The quality of wheat depends on a large complex of genes and environmental factors. The objective of this study was to identify quantitative trait loci controlling technological quality traits and their stability across environments, and to assess the impact of interaction between alleles at loci Glu-1 and Glu-3 on grain quality. DH lines were evaluated in field experiments over a period of 4 years, and genotyped using simple sequence repeat markers. Lines were analysed for grain yield (GY), thousand grain weight (TGW), protein content (PC), starch content (SC), wet gluten content (WG), Zeleny sedimentation value (ZS), alveograph parameter W (APW), hectolitre weight (HW), and grain hardness (GH). A number of QTLs for these traits were identified in all chromosome groups. The Glu-D1 locus influenced TGW, PC, SC, WG, ZS, APW, GH, while locus Glu-B1 affected only PC, ZS, and WG. Most important marker-trait associations were found on chromosomes 1D and 5D. Significant effects of interaction between Glu-1 and Glu-3 loci on technological properties were recorded, and in all types of this interaction positive effects of Glu-D1 locus on grain quality were observed, whereas effects of Glu-B1 locus depended on alleles at Glu-3 loci. Effects of Glu-A3 and Glu-D3 loci per se were not significant, while their interaction with alleles present at other loci encoding HMW and LMW were important. These results indicate that selection of wheat genotypes with predicted good bread-making properties should be based on the allelic composition both in Glu-1 and Glu-3 loci, and confirm the predominant effect of Glu-D1d allele on technological properties of wheat grains. 相似文献
17.
Mitoraj MP Parafiniuk M Srebro M Handzlik M Buczek A Michalak A 《Journal of molecular modeling》2011,17(9):2337-2352
The present study characterizes changes in the electronic structure of reactants during chemical reactions based on the combined
charge and energy decomposition scheme, ETS-NOCV (extended transition state–natural orbitals for chemical valence). Decomposition
of the activation barrier, ΔE
#, into stabilizing (orbital interaction, ΔE
orb, and electrostatic, ΔE
elstat) and destabilizing (Pauli repulsion, ΔE
Pauli, and geometry distortion energy, ΔE
dist) factors is discussed in detail for the following reactions: (I) hydrogen cyanide to hydrogen isocyanide, HCN → CNH isomerization; (II) Diels-Alder cycloaddition of ethene to 1,3-butadiene; and two catalytic processes, i.e., (III) insertion of ethylene into the metal-alkyl bond using half-titanocene with phenyl-phenoxy ligand catalyst; and (IV) B–H bond activation catalyzed by an Ir-containing catalyst. Various reference states for fragments were applied in ETS-NOCV
analysis. We found that NOCV-based deformation densities (Δρ
i) and the corresponding energies ΔE
orb(i) obtained from the ETS-NOCV scheme provide a very useful picture, both qualitatively and quantitatively, of electronic
density reorganization along the considered reaction pathways. Decomposition of the barrier ΔE# into stabilizing and destabilizing contributions allowed us to conclude that the main factor responsible for the existence
of positive values of ΔE
# for all processes (I, II, III and IV) is Pauli interaction, which is the origin of steric repulsion. In addition, in the case of reactions II, III and IV, a significant degree of structural deformation of the reactants, as measured by the geometry distortion energy, plays an
important role. Depending on the reaction type, stabilization of the transition state (relatively to the reactants) originating
either from the orbital interaction term or from electrostatic attraction can be of vital importance. Finally, use of the
ETS-NOCV method to describe catalytic reactions allows extraction of information on the role of catalysts in determination
of ΔE
#. 相似文献
18.
Paweł Gruszczyński Krzysztof Smalara Michał Obuchowski Rajmund Kaźmierkiewicz 《Journal of molecular modeling》2011,17(5):1081-1090
In this work we used a combination of classical molecular dynamics and simulated annealing techniques to shed more light on the conformational flexibility of 12 adenosine triphosphate (ATP) analogues in a water environment. We present simulations in AMBER force field for ATP and 12 published analogues [Shah et al. (1997) Proc Natl Acad Sci USA 94: 3565–3570]. The calculations were carried out using the generalized Born (GB) solvation model in the presence of the cation Mg2+. The ion was placed at a close distance (2 Å) from the charged oxygen atoms of the beta and gamma phosphate groups of the ?3 negatively charged ATP analogue molecules. Analysis of the results revealed the distribution of inter-proton distances H8–H1′ and H8–H2′ versus the torsion angle ψ (C4–N9-C1′–O4′) for all conformations of ATP analogues. There are two gaps in the distribution of torsion angle ψ values: the first is between ?30 and 30 degrees and is described by cis-conformation; and the second is between 90 and 175 degrees, which mostly covers a region of anti conformation. Our results compare favorably with results obtained in experimental assays [Jiang and Mao (2002) Polyhedron 21:435–438]. 相似文献
19.
The cyanobacterial endosymbionts of Paulinella chromatophora can shed new light on the process of plastid acquisition. Their genome is devoid of many essential genes, suggesting gene transfer to the host nucleus and protein import back into the endosymbionts/plastids. Strong evidence for such gene transfer is provided by the psaE gene, which encodes a PSI component that was efficiently transferred to the Paulinella nucleus. It remains unclear, however, how this protein is imported into the endosymbionts/plastids. We reanalyzed the sequence of Paulinella psaE and identified four potential non‐AUG translation initiation codons upstream of the previously proposed start codon. Interestingly, the longest polypeptide, starting from the first UUG, contains a clearly identifiable signal peptide with very high (90%) predictability. We also found several downstream hairpin structures that could enhance translation initiation from the alternative codon. These results strongly suggest that the PsaE protein is targeted to the outer membrane of Paulinella endosymbionts/plastids via the endomembrane system. On the basis of presence of respective bacterial homologs in the Paulinella endosymbiont/plastid genome, we discuss further trafficking of PsaE through the peptidoglycan wall and the inner envelope membrane. It is possible that other nuclear‐encoded proteins of P. chromatophora also carry signal peptides, but, alternatively, some may be equipped with transit peptides. If this is true, Paulinella endosymbionts/plastids would possess two distinct targeting systems, one cotranslational and the second posttranslational, as has been found in higher plant plastids. Considering the endomembrane system‐mediated import pathway, we also discuss homology of the membranes surrounding Paulinella endosymbionts/plastids. 相似文献
20.
Małgorzata Wnętrzak Paweł Błażej Dorota Mackiewicz Paweł Mackiewicz 《BMC evolutionary biology》2018,18(1):192