全文获取类型
收费全文 | 658篇 |
免费 | 65篇 |
国内免费 | 24篇 |
专业分类
747篇 |
出版年
2023年 | 5篇 |
2022年 | 36篇 |
2021年 | 22篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 25篇 |
2015年 | 32篇 |
2014年 | 51篇 |
2013年 | 67篇 |
2012年 | 57篇 |
2011年 | 73篇 |
2010年 | 76篇 |
2009年 | 45篇 |
2008年 | 40篇 |
2007年 | 14篇 |
2006年 | 21篇 |
2005年 | 7篇 |
2004年 | 14篇 |
2003年 | 6篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1968年 | 3篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1954年 | 1篇 |
1950年 | 1篇 |
1937年 | 1篇 |
1929年 | 2篇 |
1928年 | 1篇 |
排序方式: 共有747条查询结果,搜索用时 15 毫秒
41.
Bukan N Sözen S Coskun U Sancak B Günel N Bozkirli I Senocak C 《European cytokine network》2003,14(3):163-167
BACKGROUND: Both interleukin-18 and nitric oxide are multifunctional molecules that are involved in the different steps of carcinogenesis. METHODS: In the present study, we measured serum interleukin-18 and nitric oxide activity in 51 bladder cancer patients with different tumor stage and grade, and in 8 healthy controls. Serum nitrite-nitrate levels were measured as an index of nitric oxide generation. RESULTS: Serum interleukin-18 levels were significantly higher in bladder cancer patients when compared to the control subjects (p > 0.05). Serum interleukin-18 levels were found to be higher in patients with Ta stage than patients with T1 and T2, T3, T4 stages and in patients with grade 1 tumors than patients with grade 2 and grade 3 tumors, but this was not statistically significant (p > 0.05). There was no significant difference in serum nitrite + nitrate levels between bladder cancer patients and control subjects. CONCLUSIONS: Elevated serum interleukin-18 levels in bladder carcinoma patients may be a result of host defence mechanism against the growth and progression of bladder cancer cells. 相似文献
42.
Coskun T Chu S Montrose MH 《American journal of physiology. Gastrointestinal and liver physiology》2001,281(4):G870-G877
Our previous report showed gastric mucosal surface pH was determined by alkali secretion at intragastric luminal pH 3 but by acid secretion at intragastric pH 5. Here, we question whether regulation of mucosal surface pH is due to the effect of luminal pH on net acid/base secretions of the whole stomach. Anesthetized rats with a gastric cannula were used, the stomach lumen was perfused with weakly buffered saline, and gastric secretion was detected in the gastric effluent with 1) a flow-through pH electrode and 2) a fluorescent pH-sensitive dye (Cl-NERF). During pH 5 luminal perfusion, both pH sensors reported the gastric effluent was acidic (pH 4.79). After perfusion was stopped transiently (stop-flow), net acid accumulation was observed in the effluent when perfusion was restarted (peak change to pH 4.1-4.3). During pH 3 luminal perfusion, both pH sensors reported gastric effluent was close to perfusate pH (3.0-3.1), but net alkali accumulation was detected at both pH sensors after stop-flow (peak pH 3.3). Buffering capacity of gastric effluents was used to calculate net acid/alkaline secretions. Omeprazole blocked acid secretion during pH 5 perfusion and amplified net alkali secretion during pH 3 perfusion. Pentagastrin elicited net acid secretion under both luminal pH conditions, an effect antagonized by somatostatin. We conclude that in the basal condition, the rat stomach was acid secretory at luminal pH 5 but alkaline secretory at luminal pH 3. 相似文献
43.
Twenty-eight rhodium, iridium or ruthenium complexes were evaluated for their in vitro antifungal activities against Candida albicans and Candida tropicalis. Fourteen compounds showed an antifungal activity against C. albicans and C. tropicalis with a range of the minimum inhibitor concentrations (MICs) between 16 and 250 micrograms/mL. 相似文献
44.
Dilara Kaman Necip İlhan Kerem Metin Mehmet Akbulut Bilal Üstündağ 《Cell biochemistry and function》2009,27(2):88-92
Paraoxonase 1 (PON 1) is a high‐density lipoprotein (HDL)‐associated enzyme with antioxidant function protecting low‐density lipoprotein (LDL) from oxidation. PON 1 has two amino acid polymorphisms in coding region; L/M 55 and Q/R 192. These polymorphisms modulate paraoxonase activity of the enzyme. PON 1 activity decreases in coronary artery disease (CAD). In the present study, distribution of PON 1 L/M 55 and Q/R 192 polymorphisms and the effect of these polymorphisms on the activities of PON 1, and on the severity of CAD in 277 CAD (+) patient and 92 CAD (?) subjects were examined. PON 1 L/M 55 and Q/R 192 genotypes were determined by PCR, RFLP and agarose gel electrophoresis techniques. Genotype distributions and allele frequencies for PON 1 Q/R 192 polymorphism were not significantly different between controls and CAD (+) patient group (p > 0.05), but in genotype and allele distribution of PON 1 L/M55 polymorphism, there was significantly difference among groups (p < 0.05). Genotype distributions for both polymorphisms were not significantly different between subgroups of single‐vessel disease (SVD), double‐vessel disease (DVD) and triple‐vessel disease (TVD). Serum PON 1 activity was lower in CAD (+) group than in controls and this was also statistically significant (p < 0.001). In both groups, the highest PON activities were detected in LL and RR genotypes. In summary, our results suggest that there is an association between the PON 1 L/M 55 polymorphism of paraoxonase and CAD in Turkish patients but not with PON 1 Q/R 192 polymorphism. However, it is hard to correlate these polymorphisms and severity of CAD. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
45.
46.
Post‐translational modifications of transthyretin affect the triiodonine‐binding potential 下载免费PDF全文
Andrea Henze Thomas Homann Mustafa Serteser Ozge Can Ozlem Sezgin Abdurrahman Coskun Ibrahim Unsal Florian J. Schweigert Aysel Ozpinar 《Journal of cellular and molecular medicine》2015,19(2):359-370
Transthyretin (TTR) is a visceral protein, which facilitates the transport of thyroid hormones in blood and cerebrospinal fluid. The homotetrameric structure of TTR enables the simultaneous binding of two thyroid hormones per molecule. Each TTR subunit provides a single cysteine residue (Cys10), which is frequently affected by oxidative post‐translational modifications. As Cys10 is part of the thyroid hormone‐binding channel within the TTR molecule, PTM of Cys10 may influence the binding of thyroid hormones. Therefore, we analysed the effects of Cys10 modification with sulphonic acid, cysteine, cysteinylglycine and glutathione on binding of triiodothyronine (T3) by molecular modelling. Furthermore, we determined the PTM pattern of TTR in serum of patients with thyroid disease by immunoprecipitation and mass spectrometry to evaluate this association in vivo. The in silico assays demonstrated that oxidative PTM of TTR resulted in substantial reorganization of the intramolecular interactions and also affected the binding of T3 in a chemotype‐ and site‐specific manner with S‐glutathionylation as the most potent modulator of T3 binding. These findings were supported by the in vivo results, which indicated thyroid function‐specific patterns of TTR with a substantial decrease in S‐sulphonated, S‐cysteinylglycinated and S‐glutathionylated TTR in hypothyroid patients. In conclusion, this study provides evidence that oxidative modifications of Cys10 seem to affect binding of T3 to TTR probably because of the introduction of a sterical hindrance and induction of conformational changes. As oxidative modifications can be dynamically regulated, this may represent a sensitive mechanism to adjust thyroid hormone availability. 相似文献
47.
48.
1. Cyclical parthenogens, organisms switching between sexual and asexual mode of reproduction, are common in aquatic habitats. In permanent waterbodies with year‐round persistence of populations, the relevance of sexually produced resting eggs for population dynamics and structure is still largely unexplored. 2. The aim of this study was to investigate the importance of recruitment from resting eggs to Daphnia spp. in a deep dimictic reservoir with overwintering populations (Saidenbach Reservoir, Germany). We linked field studies on Daphnia population dynamics, hatching rates and diapausing egg abundances in the sediment with allozyme analysis of the genetic variability of both the pelagic population and hatchlings from resting eggs. 3. We found higher hatching rates at intermediate depths (10–18 m), although highest diapausing egg abundances were found in the deeper parts of the reservoir. From the extensive field data, we calculated a population budget for the main basin of the reservoir, which showed that hatched daphnids accounted for <1% of the total abundance and explained only a tiny fraction of population growth. 4. The genetic composition (MultiLocus Genotypes, MLG) of the pelagic population was relatively stable throughout the stratified period with up to five among 39 detected MLGs attaining frequencies >5% per date. From 11 MLGs differentiated among hatched daphnids, three were recovered in the pelagic population in perceptible, albeit low frequencies (1–4%). 5. We conclude that the contribution of hatched animals to the spring population dynamics is negligible in situations with an overwintering population present and will only become relevant if densities are extremely low. In this type of system, the significance of the resting egg bank is presumably mainly related to the maintenance of genetic diversity. 相似文献
49.
Doris Freißmuth Alexander Hiltgartner Christiane Stahl‐Hennig Dietmar Fuchs Klara Tenner‐Racz Paul Racz Klaus Überla Alexander Strasak Manfred P. Dierich Heribert Stoiber Barbara Falkensammer 《Journal of medical primatology》2010,39(2):97-111
Background To determine the correlation between protection and humoral immune response against simian immunodeficiency virus (SIVmac251), 11 macaques were immunized with live‐attenuated SIVmac239Δnef either intravenously or via the tonsils and exposed to SIVmac251 after either 6 or 15 months along with unvaccinated controls. Results Independent of the route of vaccine application, viremia was significantly reduced in vaccinees compared with controls 2 weeks post‐challenge. Concomitantly, viremia correlated inversely with SIV‐specific IgG, complement‐mediated lysis and neutralizing antibodies and these parameters seemed to contribute to reduced viremia. During chronic infection, six monkeys controlled viremia in the circulation (two or fewer infectious units per 106 PBMCs) and showed no signs of trapping in lymphatic tissues (Appendix S1). Conclusions As no significant differences were observed throughout the study, with respect to the humoral immune response and viremia control, between the two vaccinated cohorts, mucosal immunization strategies are recommended due to more simplified application. 相似文献
50.
FLORIAN WITZMANN HENNING SCHOLZ JOHANNES MÜLLER NIKOLAY KARDJILOV 《Zoological Journal of the Linnean Society》2010,160(2):302-340
Sculpture of dermal bones and their vascularization in basal tetrapods are closely connected. Ontogenetic data suggest that the large vessels that coursed to the superficial bone surface induced the formation of sculptural ridges and tubercles around their openings. Imprints show that the vessels continued on the bone surface and coursed within furrows or pits, where they were protected by the sculpture from mechanical damage. Dermal bone histology indicates a consolidation of the integument in basal tetrapods by strong, mineralized Sharpey's fibres in the sculptural ridges and tubercles, and by the presence of metaplastic tissue in several taxa. Because of the tight integration of bone and dermis, the large vessels were not able to spread over the sculptural elements, but instead had to pass interosseously. The diverse sculptural morphologies depend on the variation in height and width of the ‘nodal points’ and their connecting ridges, and in the size and shape of the enclosed cells and furrows. A principal component analysis (PCA) and discriminant function analysis (DFA) of 47 basal tetrapod taxa with 12 discrete characters shows that dermal sculpture is suited for distinguishing some main basal tetrapod lineages. Taxa that are interpreted as being largely aquatic have generally a more regular sculpture than presumably terrestrial ones. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 302–340. 相似文献