全文获取类型
收费全文 | 743篇 |
免费 | 36篇 |
专业分类
779篇 |
出版年
2023年 | 9篇 |
2022年 | 20篇 |
2021年 | 31篇 |
2020年 | 12篇 |
2019年 | 9篇 |
2018年 | 23篇 |
2017年 | 16篇 |
2016年 | 25篇 |
2015年 | 37篇 |
2014年 | 41篇 |
2013年 | 51篇 |
2012年 | 73篇 |
2011年 | 80篇 |
2010年 | 44篇 |
2009年 | 27篇 |
2008年 | 51篇 |
2007年 | 58篇 |
2006年 | 28篇 |
2005年 | 33篇 |
2004年 | 29篇 |
2003年 | 22篇 |
2002年 | 27篇 |
2001年 | 3篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1964年 | 1篇 |
1954年 | 1篇 |
1952年 | 1篇 |
排序方式: 共有779条查询结果,搜索用时 0 毫秒
51.
Ilijin L Janković-Tomanić M Mitić M Vlahović M Lazarević J Perić-Maratuga V Prolić Z Nenadović V 《Folia biologica》2003,51(3-4):207-211
The response of Morimus funereus larvae to total starvation and refeeding with qualitatively different nutritive substrates (artificial diets supplemented with yeast as a source of B complex vitamins or with a digestibility reducer-tannic acid) was examined in this paper. Refeeding resulted in a compensatory increase of larval growth. Feeding and refeeding with qualitatively different nutritive substrates affected both quality and quantity of midgut and brain proteins. The observed differences suggest the possible switching of enzyme isoforms in M. funereus midgut and changes in synthesis/secretion of neurohormones, depending on food presence and its nutritional value. 相似文献
52.
53.
54.
Jelena Djordjevic Ana Djordjevic Miroslav Adzic Marija B. Radojcic 《Cellular and molecular neurobiology》2010,30(5):693-700
Chronic neuroendocrine stress usually leads to the elevation of the stress hormones and increased metabolic rate, which is
frequently accompanied by oxidative damage to the CNS. In the present study we hypothesized that chronic psychosocial isolation
(CPSI) of male Wistar rats, characterized by decreased serum corticosterone (CORT), unaltered catecholamines (CTs), and low
blood glucose (GLU), may also promote oxidative imbalance in the CNS, by targeting antioxidant defense system. To test it,
we have examined the relation between these input signals and protein expression/activity of antioxidant enzymes (AOEs): superoxide
dismutases (SODs), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GLR) in the hippocampus (HIPPO)
of CPSI animals. We found that CPSI did not affect SODs or CAT, but decreased activity of GPx and compromised GLR, an enzyme
highly dependent on blood GLU for its substrate precursor. Further, we have tested whether the CPSI experience altered AOEs
response to a novelty stress, and found that it attenuated peroxide-metabolizing enzymes, CAT and GPx, and decreased GLR activity,
even though blood GLU was restored. The altered ratios of hippocampal AOEs in CPSI animals, which were worsened under the
combined stress conditions, may lead to the accumulation of peroxide products and oxidative imbalance. The mechanism by which
CPSI generate oxidative imbalance in the HIPPO is most likely based on poor systemic energy conditions set by this stress.
Such conditions may cause functional decline of CNS structures, such as HIPPO, and are likely to promote state linked to onset
of many mood disorders. 相似文献
55.
Kroata Hazler Pilepić Miranda Morović Filip Orač Marija Šantor Vanja Vejnović 《Biologia》2010,65(5):805-812
The chloroplast DNA of 43 species including 16 sections from the genus Hypericum was studied by PCR-RFLP analysis. The PCR-amplified products of four cpDNA regions, trnC-trnD, psbC-trnS, trnL-trnF and rbcL were digested with four restriction endonucleases. A high level of interspecific variation was detected while intraspecific
diversity was not observed. The resulting parsimony analysis indicated the monophyletic assemblage of the sections Androsaemum, Olympia, Drosocarpium and Trigynobrathys. Monophyly of Hypericum is weakly supported, but close relationships of H. perforatum and H. maculatum are indicated. The members of Ascyreia are weakly resolved, but clustering of H. kouytchense and H. oblongifolium is well supported, however, H. reptans is nested with Olympia. CpDNA profiles and the positions on the parsimony tree indicate that the chloroplast donor among the putative parents of
the hybrid species H. ×inodorum is H. androsaemum. 相似文献
56.
57.
Jokić M Brčić-Kostić K Stefulj J Catela Ivković T Božo L Gamulin M Kapitanović S 《DNA and cell biology》2011,30(10):771-776
Altered folate levels may play an important role in colon carcinogenesis. The aim of this study was to investigate the association of polymorphisms in key folate-metabolizing genes with susceptibility to sporadic colon cancer. Six common polymorphisms (two in MTHFR and one each in MTR, MTRR, RFC1, and DHFR genes) were genotyped in 300 healthy subjects and 300 colon cancer patients from Croatia. Obtained results indicate possible protective role of MTRR 66 AA in sporadic colon cancer (OR=0.655; 95% CI=0.441-0.973; p=0.04). Maximum-likelihood analysis of haplotypes revealed a linkage disequilibrium (LD) between the two investigated polymorphisms of the MTHFR gene (C677T and A1298C), both in the control and patient groups (p<0.01 for both). LD was also detected between MTRR A66G and MTHFR A1298C polymorphisms but only in a group of patients (p<0.01). A haplotype of A66G and A1298C polymorphisms, A/A, proved to be protective (OR=0.775; 95% CI=0.603-0.996; p=0.04), whereas haplotype A/G was a risk factor for colon cancer (OR=1.270; 95% CI=1.007-1.602; p=0.04). Contrary to some previous studies, single-locus analyses identified no polymorphisms associated with risk for colon cancer, but demonstrated a possible protective effect of MTRR 66 AA genotype. The detected significant LD between two loci (MTHFR A1298C and MTRR A66G) located on different chromosomes indicates a strong selective force as a mechanism for the maintenance of their linkage. Specific combinations of alleles of these two polymorphisms showed a protective but also a risk effect on colon cancer susceptibility. 相似文献
58.
59.
Marija Brgles Pero Prebeg Tihana Kurtović Jelena Ranić Martina Marchetti-Deschmann Günter Allmaier 《Preparative biochemistry & biotechnology》2016,46(7):695-703
Tetanus toxoid (TTd) is a highly immunogenic, detoxified form of tetanus toxin, a causative agent of tetanus disease, produced by Clostridium tetani. Since tetanus disease cannot be eradicated but is easily prevented by vaccination, the need for the tetanus vaccine is permanent. The aim of this work was to investigate the possibility of optimizing TTd purification, i.e., ammonium sulfate precipitation process. The influence of the percentage of ammonium sulfate, starting amount of TTd, buffer type, pH, temperature, and starting purity of TTd on the purification process were investigated using optimal design for response surface models. Responses measured for evaluation of the ammonium sulfate precipitation process were TTd amount (Lf/mL) and total protein content. These two parameters were used to calculate purity (Lf/mgPN) and the yield of the process. Results indicate that citrate buffer, lower temperature, and lower starting amount of TTd result in higher purities of precipitates. Gel electrophoresis combined with matrix-assisted laser desorption ionization–mass spectrometric analysis of precipitates revealed that there are no inter-protein cross-links and that all contaminating proteins have pIs similar to TTd, so this is most probably the reason for the limited success of purification by precipitation. 相似文献
60.
Marta Narczyk Marta Ilona Wojty Ivana Le
i Aler Biserka
ini Marija Lui Elbieta Katarzyna Jagusztyn-Krynicka Zoran tefani Agnieszka Bzowska 《Journal of enzyme inhibition and medicinal chemistry》2022,37(1):1083
Helicobacter pylori represents a global health threat with around 50% of the world population infected. Due to the increasing number of antibiotic-resistant strains, new strategies for eradication of H. pylori are needed. In this study, we suggest purine nucleoside phosphorylase (PNP) as a possible new drug target, by characterising its interactions with 2- and/or 6-substituted purines as well as the effect of these compounds on bacterial growth. Inhibition constants are in the micromolar range, the lowest being that of 6-benzylthio-2-chloropurine. This compound also inhibits H. pylori 26695 growth at the lowest concentration. X-ray structures of the complexes of PNP with the investigated compounds allowed the identification of interactions of inhibitors in the enzyme’s base-binding site and the suggestion of structures that could bind to the enzyme more tightly. Our findings prove the potential of PNP inhibitors in the design of drugs against H. pylori. 相似文献