全文获取类型
收费全文 | 1707篇 |
免费 | 103篇 |
国内免费 | 8篇 |
专业分类
耳鼻咽喉 | 14篇 |
儿科学 | 40篇 |
妇产科学 | 30篇 |
基础医学 | 160篇 |
口腔科学 | 65篇 |
临床医学 | 165篇 |
内科学 | 405篇 |
皮肤病学 | 83篇 |
神经病学 | 109篇 |
特种医学 | 68篇 |
外科学 | 333篇 |
综合类 | 16篇 |
现状与发展 | 1篇 |
预防医学 | 75篇 |
眼科学 | 62篇 |
药学 | 91篇 |
中国医学 | 8篇 |
肿瘤学 | 93篇 |
出版年
2023年 | 23篇 |
2022年 | 39篇 |
2021年 | 83篇 |
2020年 | 61篇 |
2019年 | 85篇 |
2018年 | 85篇 |
2017年 | 63篇 |
2016年 | 67篇 |
2015年 | 87篇 |
2014年 | 100篇 |
2013年 | 112篇 |
2012年 | 142篇 |
2011年 | 142篇 |
2010年 | 72篇 |
2009年 | 74篇 |
2008年 | 140篇 |
2007年 | 109篇 |
2006年 | 110篇 |
2005年 | 85篇 |
2004年 | 51篇 |
2003年 | 45篇 |
2002年 | 26篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 3篇 |
排序方式: 共有1818条查询结果,搜索用时 515 毫秒
71.
72.
Keivan Lorian Mehri Kadkhodaee Farzaneh Kianian Arash Abdi Mina Ranjbaran Ghorbangol Ashabi Behjat Seifi 《Andrologia》2020,52(2):e13496
The main aim of this study was to assay the testicular H2S levels in the varicocele rat model and then to investigate the protective effects of NaHS on morphometric changes, sperm parameters, oxidative stress and apoptosis markers in rat's testis. D,L-propargylglycine (PAG) was administrated to show the effects of cystathionine γ-lyase enzyme (CSE) inhibition in the varicocele. Rats were assigned to four groups: (a) Sham, (b) varicocele, (c) varicocele + PAG and (d) varicocele + NaHS. Animals in varicocele + NaHS group received 30 µmol/L NaHS in drinking water for 56 days. In the varicocele + PAG group, animals received PAG 19 mg/kg twice a week. Morphometric assessment, oxidative stress markers, testicular H2S levels, sperm parameters, TUNEL assay and expression of Bax/Bcl2 were evaluated at the end of experiment. Testicular H2S levels were significantly decreased in varicocele group. NaHS significantly improved sperm parameters, morphometric characteristics and oxidative stress compared to varicocele group. Oxidative stress status deteriorated in the PAG group compared to the varicocele group. This study showed that a low testicular H2S level might play a critical role in male infertility. Thus, NaHS administration may be a promising treatment strategy for male infertility in varicocele. In addition, CSE may not be the only important enzyme in testicular H2S production. 相似文献
73.
Kim D Harrison Beverly D Hiebert Arash Panahifar Janna M Andronowski Amir M Ashique Gavin A King Terra Arnason Kurtis J Swekla Peter Pivonka David ML Cooper 《Journal of bone and mineral research》2020,35(11):2211-2228
Cortical bone porosity is intimately linked with remodeling, is of growing clinical interest, and is increasingly accessible by imaging. Thus, the potential of animal models of osteoporosis (OP) to provide a platform for studying how porosity develops and responds to interventions is tremendous. To date, rabbit models of OP have largely focused on trabecular microarchitecture or bone density; some such as ovariectomy (OVX) have uncertain efficacy and cortical porosity has not been extensively reported. Our primary objective was to characterize tibial cortical porosity in rabbit-based models of OP, including OVX, glucocorticoids (GC), and OVX + GC relative to controls (SHAM). We sought to: (i) test the hypothesis that intracortical remodeling is elevated in these models; (ii) contrast cortical remodeling and porosity in these models with that induced by parathyroid hormone (1–34; PTH); and (iii) contrast trabecular morphology in the proximal tibia across all groups. Evidence that an increase in cortical porosity occurred in all groups was observed, although this was the least robust for GC. Histomorphometric measures supported the hypothesis that remodeling rate was elevated in all groups and also revealed evidence of uncoupling of bone resorption and formation in the GC and OVX + GC groups. For trabecular bone, a pattern of loss was observed for OVX, GC, and OVX + GC groups, whereas the opposite was observed for PTH. Change in trabecular number best explained these patterns. Taken together, the findings indicated rabbit models provide a viable and varied platform for the study of OP and associated changes in cortical remodeling and porosity. Intriguingly, the evidence revealed differing effects on the cortical and trabecular envelopes for the PTH model. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).. 相似文献
74.
Hosein Shabaninejad Gholamhossein Mehralian Arash Rashidian Ahmad Baratimarnani Hamid Reza Rasekh 《Daru : journal of Faculty of Pharmacy, Tehran University of Medical Sciences》2014,22(1):35
Background
Pharmaceutical industry is knowledge-intensive and highly globalized, in both developed and developing countries. On the other hand, if companies want to survive, they should be able to compete well in both domestic and international markets. The main purpose of this paper is therefore to develop and prioritize key factors affecting companies’ competitiveness in pharmaceutical industry. Based on an extensive literature review, a valid and reliable questionnaire was designed, which was later filled up by participants from the industry. To prioritize the key factors, we used the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS).Results
The results revealed that human capital and macro-level policies were two key factors placed at the highest rank in respect of their effects on the competitiveness considering the industry-level in pharmaceutical area.Conclusion
This study provides fundamental evidence for policymakers and managers in pharma context to enable them formulating better polices to be proactively competitive and responsive to the markets’ needs. 相似文献75.
Arash Khorrami Mojtaba Hammami Mehraveh Garjani Nasrin Maleki-Dizaji Alireza Garjani 《Daru : journal of Faculty of Pharmacy, Tehran University of Medical Sciences》2014,22(1)
Background
The inflammatory responses play a major role in the pathogenesis of acute myocardial infarction (MI). Early inhibition of inflammation may improve post MI cardiac function. The aim of this study was to investigate the effects of tacrolimus on cardiac function, hemodynamic parameters as well as histopathologic and electrocardiographic changes in isoproterenol-induced myocardial infarction.Methods
Male Wistar rats were randomly divided into six groups of control, isoproterenol alone, tacrolimus alone, and isoproterenol plus tacrolimus (0.5, 1 and 2 mg/kg). Isoproterenol (100 mg/kg) was injected subcutaneously for two consecutive days to induce myocardial infarction, and simultaneously tacrolimus was administered orally twice a day for three days.Results and conclusions
Administration of isoproterenol resulted in myocardial edema and necrosis as well as a marked reduction in the left ventricular systolic pressure (LVSP), left ventricular contractility (LVdP/dtmax) and relaxation (LVdP/dtmin) along with a severe elevation in left ventricular end-diastolic pressure (LVEDP). Isoproterenol also elevated the ST-segment and suppressed the R-amplitude and R-R interval on ECG. It was found that all doses of tacrolimus could amend the ECG pattern and ameliorated the isoproterenol induced disturbances in cardiac function. Acute and short term treatment with tacrolimus at dose of 2 mg/kg significantly (P < 0.001) improved LVdP/dtmax from 2712 ± 82 in myocardial infarcted rats to 4592 ± 149 mmHg/sec. Similarly, tacrolimus lowered LVEDP from 17.6 ± 0.68 in MI group to the value of 5.6 ± 0.22 mmHg (P < 0.001). Furthermore, tacrolimus was found to reduce malondialdehyde concentration in serum and myocardium by 50-70% (P < 0.001).The results of this study showed that acute treatment with tacrolimus, coincided with the occurrence of myocardial infarction, strongly protected the myocardium against the isoproterenol-induced myocardial infarction; where this might be due to the anti-inflammatory properties of tacrolimus. 相似文献76.
Hamidreza AZIZI Behrouz SHIRAN Arash Borjian BOROUJENI Milad JAFARI 《Iranian Journal of Parasitology》2014,9(3):429-434
Background
Toxoplasmosis is a worldwide spread disease. The present study examined the prevalence of Toxoplasma gondii infection among animals of edible meat (cattle and sheep) in Chaharmahal va Bakhtiari Province (Southwest of Iran) in 2012. Furthermore, we attempted for the first time to identify this parasite from the meat products in the province.Methods
The tongue, brain, femur muscle and liver of 50 sheep and 70 cattle as well as 50 samples of meat products were selected and collected to perform molecular survey using Nested-PCR method.Results
Of the studied sheep, 38% were infected. The infection rate in the age groups under 1 year, 1-2 years, and more than 2 years was 25%, 35.29% and 52.94%, respectively. The infection rate in femur muscle, brain, liver and tongue was 28%, 32%, 30% and 16%, respectively. Of the studied cattle, 8.57% were infected. The infection rate in the age groups 1-2 years, 2-4 years, and more than 4 years was 3.7%, 9.09% and 14.28%, respectively. Sheep was infected 6 times more than cattle (OR = 6.53 CI = 2.374-18.005).The infection rate among samples of meat products was 12% (6 samples out of 50 samples).Conclusion
Due to the high rate of this parasitic infection among the slaughtered animals as well as meat products in this region, the use of infected material can be one of the main risk factors of transmission of the parasite to humans. 相似文献77.
Aryana Arash Gandhavadi Maheer Bhaskar Rohit Di Biase Luigi 《Journal of interventional cardiac electrophysiology》2021,61(1):211-212
Journal of Interventional Cardiac Electrophysiology - 相似文献
78.
Dramatic acceleration of protein folding by stabilization of a nonnative backbone conformation
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Di Nardo AA Korzhnev DM Stogios PJ Zarrine-Afsar A Kay LE Davidson AR 《Proceedings of the National Academy of Sciences of the United States of America》2004,101(21):7954-7959
Through a mutagenic investigation of Gly-48, a highly conserved position in the Src homology 3 domain, we have discovered a series of amino acid substitutions that are highly destabilizing, yet dramatically accelerate protein folding, some up to 10-fold compared with the wild-type rate. The unique folding properties of these mutants allowed for accurate measurement of their folding and unfolding rates in water with no denaturant by using an NMR spin relaxation dispersion technique. A strong correlation was found between beta-sheet propensity and the folding rates of the Gly-48 mutants, even though Gly-48 lies in an unusual non-beta-strand backbone conformation in the native state. This finding indicates that the accelerated folding rates of the Gly-48 mutants are the result of stabilization of a nonnative beta-strand conformation in the transition-state structure at this position, thus providing the first, to our knowledge, experimentally elucidated example of a mechanism by which folding can occur fastest through a nonnative conformation. We also demonstrate that residues that are most stabilizing in the transition-state structure are most destabilizing in the native state, and also cause the greatest reductions in in vitro functional activity. These data indicate that the unusual native conformation of the Gly-48 position is important for function, and that evolutionary selection for function can result in a domain that folds at a rate far below the maximum possible. 相似文献
79.
Weiss BP Kim SS Kirschvink JL Kopp RE Sankaran M Kobayashi A Komeili A 《Proceedings of the National Academy of Sciences of the United States of America》2004,101(22):8281-8284
Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetofossils. Here we use three rock magnetic techniques, low-temperature cycling, the Moskowitz test, and ferromagnetic resonance, to sense the bulk composition and crystallography of millions of ALH84001 magnetite crystals. The magnetic data demonstrate that although the magnetite is unusually pure and fine-grained in a manner similar to terrestrial magnetofossils, most or all of the crystals are not arranged in chains. 相似文献
80.
p19Arf induces p53-dependent apoptosis during Abelson virus-mediated pre-B cell transformation 总被引:10,自引:0,他引:10
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Arash Radfar Indira Unnikrishnan Han-Woong Lee Ronald A. DePinho Naomi Rosenberg 《Proceedings of the National Academy of Sciences of the United States of America》1998,95(22):13194-13199
The Ink4a/Arf locus encodes p16Ink4a and p19Arf and is among the most frequently mutated tumor suppressor loci in human cancer. In mice, many of these effects appear to be mediated by interactions between p19Arf and the p53 tumor-suppressor protein. Because Tp53 mutations are a common feature of the multistep pre-B cell transformation process mediated by Abelson murine leukemia virus (Ab-MLV), we examined the possibility that proteins encoded by the Ink4a/Arf locus also play a role in Abelson virus transformation. Analyses of primary transformants revealed that both p16Ink4a and p19Arf are expressed in many of the cells as they emerge from the apoptotic crisis that characterizes the transformation process. Analyses of primary transformants from Ink4a/Arf null mice revealed that these cells bypassed crisis. Because expression of p19Arf but not p16 Ink4a induced apoptosis in Ab-MLV-transformed pre-B cells, p19Arf appears to be responsible for these events. Consistent with the link between p19Arf and p53, Ink4a/Arf expression correlates with or precedes the emergence of cells expressing mutant p53. These data demonstrate that p19Arf is an important part of the cellular defense mounted against transforming signals from the Abl oncoprotein and provide direct evidence that the p19Arf–p53 regulatory loop plays an important role in lymphoma induction. 相似文献