全文获取类型
收费全文 | 1350篇 |
免费 | 69篇 |
国内免费 | 1篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 27篇 |
2020年 | 19篇 |
2019年 | 24篇 |
2018年 | 43篇 |
2017年 | 35篇 |
2016年 | 47篇 |
2015年 | 53篇 |
2014年 | 68篇 |
2013年 | 102篇 |
2012年 | 115篇 |
2011年 | 114篇 |
2010年 | 67篇 |
2009年 | 45篇 |
2008年 | 90篇 |
2007年 | 115篇 |
2006年 | 88篇 |
2005年 | 83篇 |
2004年 | 55篇 |
2003年 | 66篇 |
2002年 | 53篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有1420条查询结果,搜索用时 15 毫秒
41.
42.
Wojciech Lipinski Joanna Wasko Malgorzata Walczak Justyna Fraczyk Zbigniew J. Kaminski Krystian Galecki Zbigniew Draczynski Izabella Krucinska Marta Kaminska Beata Kolesinska 《化学与生物多样性》2019,16(11)
The aim of the study was the assessment of the ability of short peptides to form aggregates under physiological conditions. The dipeptides studied were derived from different aromatic amino acids (heteroaromatic peptides). Tripeptides were obtained from two distinct aromatic amino acids and cysteine or methionine residue in the C‐terminal, N‐terminal, or central position. The ability of the peptides to form fibrous aggregates under physiological conditions was evaluated using three independent methods: the Congo Red assay, the Thioflavin T assay, and microscopic examinations using normal and polarized light. Materials potentially useful for regenerative medicine were selected based on their cytotoxicity to the endothelial cell line EA.hy 926 and physicochemical properties of films formed by peptides. The required parameters of biocompatibility were fulfilled by H?PheCysTrp?OH, H?PheCysTyr?OH, H?PheTyrMet?OH, and H?TrpTyr?OH. 相似文献
43.
Liucija Weselik Ewa Majchrzak Matthew Ibbs Adam Lewandowski Andrzej Marszałek Piotr Machczyński Wojciech Golusiński 《Reports of Practical Oncology and Radiotherapy》2019,24(5):443-449
AimThe aim of the study was to assess the accuracy of radiological diagnosis of laryngeal cartilage infiltration by histopathological examination of laryngeal specimen after total laryngectomy.BackgroundDespite the development of new medical technologies and significant clinical advances allowing early diagnosis and treatment of laryngeal cancer, mortality is still on the rise. Neoplastic infiltration of the laryngeal cartilages is the most common source of error in the assessment of cancer staging. Furthermore, cartilage invasion is listed as a contraindication to partial surgical techniques as well as radiotherapy.Materials and methodsThe study was carried out on 21 larynges following total laryngectomy. Before taking the decision to perform surgery, high-resolution CT scans were performed in all cases. An extended histopathological examination was conducted using a unique vertical cross-section of the whole larynx.ResultsPathology reported 2 cases of arytenoid cartilage invasion, 5 cases of cricoid cartilage invasion, 12 cases of thyroid cartilage penetration, 1 case of internal cortex invasion and 9 cases of extra-laryngeal spread. CT imaging identified 8 of 13 cases (61.5%) of pathologically proven invasion of thyroid cartilage and only 2 cases (2/9, 22%) of extra-laryngeal spread. According to CT results, arytenoid cartilage invasion was correctly identified in 2 cases, cricoid cartilage invasion in 4 (4/5, 80%). The positive predictive values for thyroid, cricoid and arytenoid cartilage invasion and penetration were 80%, 66.7% and 50%, respectively. In case of pre-laryngeal spread the positive predictive value was 100%.ConclusionDespite increasingly advanced methods involved in the diagnosis of laryngeal cancer, many discrepancies may be observed between the radiological and histopathological assessments. CT imaging has limitations especially in thyroid cartilage penetration and extra-laryngeal spread assessment in advanced laryngeal cancer cases. An extended histopathological examination, involving vertical cross-sections of the whole larynx is a very precise study that allows a precise determination of local cancer staging (T). 相似文献
44.
Michael Jakob Rupar Pawel Golusinski Wojciech Golusinski Michal M. Masternak 《Reports of Practical Oncology and Radiotherapy》2019,24(6):544-550
Human Papillomavirus (HPV) remains one of the most commonly contracted sexually transmitted diseases around the world. There are a multitude of HPV types, some of which may never present any symptoms. Others, however, are considered high-risk types, which increase the chance of the person infected to develop cancer. In recent years, the utilization of nanotechnology has allowed researchers to employ and explore the use of nanoparticles in immunotherapies.The new nanoparticle frontier has opened many doors in this area of research as a form of prevention, diagnosis, and treatment in cancers resulting from HPV. This review will provide a brief background of HPV, its relationship to head and neck cancer (HNC) and present some insight into the field of immunotherapeutic nanoparticles. 相似文献
45.
This paper presents an ab initio quantum chemical investigation of the geometrical structures and the non-linear optical properties (NLO) of three structural isomers of pyridinium N-phenolate betaine dye. The ground state geometrical parameters and the first-order hyperpolarizabilities were calculated using the Hartree-Fock (HF) as well as the second-order perturbation Møller-Pleset (MP2) method with the 6–31G, 6–31G(d), 6–31G(d,p), 6–31+G(d), 6–31++G(d,p), 6–311+G(d), aug-cc-PVDZ and the recently developed Z3PolX basis sets. Moreover, the first-order hyperpolarizability was calculated at the coupled cluster singles and doubles (CCSD/6–31+G(d)) level of theory. The analysis of the results of calculations for the investigated isomers indicates that there are important differences in their NLO activities. Additionally, it was shown that Z3PolX basis set works reasonable well for betaine dyes. Figure
The molecules investigated in the present study. (Figure prepared using Mercury 1.5.) 相似文献
46.
Gaucher disease is a lysosomal storage disorder caused by deficiency of human acid β-glucosidase. Recent x-ray structural
elucidation of the enzyme alone and in the presence of its inhibitor was done, which provided an excellent template for further
studies on the binding of substrate, product and inhibitor. To draw correlations between the clinical manifestation of the
disease driven by point mutations, L444P and L444R, and the placement and function of putative S-binding sites, the presented
theoretical studies were undertaken, which comprised of molecular dynamics and molecular docking methods. The obtained results
indicate the D443 and D445 residues as extremely important for physiological functionality of an enzyme. They also show, although
indirectly, that binding of the substrate is influenced by an interplay of E235 and E334 residues, constituting putative substrate
binding site, and the region flanked by D435 and D445 residues.
Figure The binding of an arbitrarily chosen structure of glucosylceramide (A), conduritol-β-epoxide (B), glucose (C) to the active
site D443/D445 (A1, B1, C1) and E320/E340 (A2, B2, C2) of the wild-type structure of human acid-β-glucosidase. A1, B1, C1
blue mask represents the residues D443-D445; red mask represents the residue D444; A2, B2, C2 blue mask represents loop1 (Ser345-Glu349) and loop2 (Val394-Asp399), whereas red mask the residues E235 and 340 相似文献
47.
Harańczyk Michał Konieczyńska Małgorzata Płazak Wojciech 《Sleep and biological rhythms》2022,20(1):65-72
Sleep and Biological Rhythms - Obstructive sleep apnea syndrome (OSAS) is considered to be an important predisposing factor for cardiovascular diseases. The main objective of this study was to... 相似文献
48.
49.
Szczepanik W Kaczmarek P Jezowska-Bojczuk M 《Journal of inorganic biochemistry》2004,98(12):2141-2148
Actinomycin D (AD) is a potent anticancer drug widely applied in therapy, which however exhibits very high toxicity in humans. As the character of donors present in the AD molecule seems to be very favorable for Cu(II) ions, we undertook the coordination study on the Cu(II)-AD system. Potentiometric experiments proved a formation of very stable complexes and with the use of spectroscopic methods the identification of the binding sites was made. The values of potential energy minima, provided by theoretical modeling, confirmed the feasibility of formation of the complexes in water solution. We also demonstrated a significant effect of Cu(II) ions on AD interactions with DNA. The strand-nicking activity was observed. This process could be correlated with the speciation of complex forms. We also found out that in the presence of H2O2, low levels of Cu(II)-AD complexes induce the formation of considerable amounts of linearised plasmid. In consequence, the hypothesis is proposed that the physiologically available cupric ions may participate in the drug-induced toxic effects. 相似文献
50.
Zachara BA Koterska D Manitius J Sadowski L Dziedziczko A Salak A Wasowicz W 《Biological trace element research》2004,97(1):15-30
Patients with chronic renal failure (CRF) usually have a lower than healthy level of selenium (Se) in whole blood and plasma.
Plasma glutathione peroxidase (GSH-Px) is synthesized mostly in the kidney. In CRF patients, activity of this enzyme is significantly
reduced and its reduction increases with the progress of the disease. The aim of the study was to evaluate the effect of Se
supplementation to CRF patients at various stages of the disease on Se concentration in blood components and on plasma GSH-Px
activity.
The study group comprised 53 CRF patients at various stages of the disease supplemented with Se (200 μg/d for 3 mo as Se-enriched
yeast, containing about 70% l-selenomethionine [SeMet]). The control group consisted of 20 healthy subjects. The Se concentration in blood components was
measured spectrofluorometrically with 2,3-diaminonaphthalene as a complexing reagent. GSH-Px activity in red cell hemolysates
and plasma was assayed by the coupled method with tert-butyl hydroperoxide as a substrate.
The Se concentration in whole blood and plasma of CRF patients is significantly lower as compared with healthy subjects, but
similar at all stages of the disease. In the patients’ plasma, total protein and albumin levels are also significantly lower
than in healthy subjects. Plasma GSH-Px activity in patients is extremely low, and contrary to Se concentration, it decreases
linearly with the increasing stage of the illness. Se-supplied patients show an increased Se concentration in all blood components
and at all disease stages, whereas plasma GSH-Px activity is enhanced only at the incipient stage of the disease. Se supply
has no effect on plasma GSH-Px activity in uremic patients at the end stage of the disease. Total plasma protein and albumin
levels did not change after Se supplementation. Our data seem to show that in patients with CRF lower total protein and albumin
levels in plasma may be the chief cause of the low blood and plasma Se concentrations. GSH-Px activity decreases along with
the kidney impairment. At the end stage of the disease, Se supplementation in the form of Se-enriched yeast has no effect
on the increase in plasma GSH-Px activity. 相似文献