全文获取类型
收费全文 | 511篇 |
免费 | 42篇 |
国内免费 | 2篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 4篇 |
妇产科学 | 2篇 |
基础医学 | 75篇 |
口腔科学 | 28篇 |
临床医学 | 95篇 |
内科学 | 98篇 |
皮肤病学 | 7篇 |
神经病学 | 54篇 |
特种医学 | 7篇 |
外科学 | 76篇 |
综合类 | 10篇 |
预防医学 | 23篇 |
眼科学 | 17篇 |
药学 | 31篇 |
肿瘤学 | 25篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 17篇 |
2018年 | 14篇 |
2017年 | 18篇 |
2016年 | 21篇 |
2015年 | 17篇 |
2014年 | 21篇 |
2013年 | 21篇 |
2012年 | 56篇 |
2011年 | 54篇 |
2010年 | 26篇 |
2009年 | 27篇 |
2008年 | 42篇 |
2007年 | 46篇 |
2006年 | 38篇 |
2005年 | 18篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 6篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1974年 | 2篇 |
1971年 | 4篇 |
1970年 | 1篇 |
排序方式: 共有555条查询结果,搜索用时 15 毫秒
51.
Shahriar Koochekpour Geoffrey J. Pilkington Abderrahim Merzak 《International journal of cancer. Journal international du cancer》1995,63(3):450-454
The mechanisms underlying the invasive properties of glio-mas, the major form of intrinsic brain tumours in humans, are poorly understood. We have reported that CD44 plays an important role in this behaviour in vitro. In the present work, we investigated the role of its ligand, hyaluronic acid (HA), in invasion in 8 human glioma cell lines. We found that HA mediates cell detachment via its interaction with its high affinity receptor, CD44H. Using 8 μm porosity polycarbonate filter transwells, we demonstrate that HA strongly stimulates migration in all 8 cell lines. This effect was found to be partially counteracted by a CD44H monoclonal antibody (MAb), suggesting the involvement of CD44H, as well as other HA receptors, in this process. Furthermore, incorporation of increasing concentrations of HA in Matrigel in an in vitro invasion assay resulted in a substantial increase in the invasive propensity of the glioma cell lines. Moreover, blocking experiments with the CD44H MAb suggest that CD44H and other receptors interact with HA to promote cell invasion in vitro. Our results show that HA induces cell detachment, stimulates migration and promotes invasion via its interaction with CD44H and other HA receptors in vrtro. These effects could be prevented by use of specific HA receptor antibodies. 相似文献
52.
Selection and Characterization of β-Lactam–β-Lactamase Inactivator-Resistant Mutants following PCR Mutagenesis of the TEM-1 β-Lactamase Gene
下载免费PDF全文
![点击此处可从《Antimicrobial agents and chemotherapy》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sergei B. Vakulenko Bruce Geryk Lakshmi P. Kotra Shahriar Mobashery Stephen A. Lerner 《Antimicrobial agents and chemotherapy》1998,42(7):1542-1548
Mechanism-based inactivators of β-lactamases are used to overcome the resistance of clinical pathogens to β-lactam antibiotics. This strategy can itself be overcome by mutations of the β-lactamase that compromise the effectiveness of their inactivation. We used PCR mutagenesis of the TEM-1 β-lactamase gene and sequenced the genes of 20 mutants that grew in the presence of ampicillin-clavulanate. Eleven different mutant genes from these strains contained from 1 to 10 mutations. Each had a replacement of one of the four residues, Met69, Ser130, Arg244, and Asn276, whose substitutions by themselves had been shown to result in inhibitor resistance. None of the mutant enzymes with multiple amino acid substitutions generated in this study conferred higher levels of resistance to ampicillin alone or ampicillin with β-lactamase inactivators (clavulanate, sulbactam, or tazobactam) than the levels of resistance conferred by the corresponding single-mutant enzymes. Of the four enzymes with just a single mutation (Ser130Gly, Arg244Cys, Arg244Ser, or Asn276Asp), the Asn276Asp β-lactamase conferred a wild-type level of ampicillin resistance and the highest levels of resistance to ampicillin in the presence of inhibitors. Site-directed random mutagenesis of the Ser130 codon yielded no other mutant with replacement of Ser130 besides Ser130Gly that produced ampicillin-clavulanate resistance. Thus, despite PCR mutagenesis we found no new mutant TEM β-lactamase that conferred a level of resistance to ampicillin plus inactivators greater than that produced by the single-mutation enzymes that have already been reported in clinical isolates. Although this is reassuring, one must caution that other combinations of multiple mutations might still produce unexpected resistance. 相似文献
53.
Glycine-induced long-term potentiation is associated with structural and functional modifications of α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid receptors
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)
Wael Musleh Xiaoning Bi Georges Tocco Shahriar Yaghoubi Michel Baudry 《Proceedings of the National Academy of Sciences of the United States of America》1997,94(17):9451-9456
Global long-term potentiation (LTP) was induced in organotypic hippocampal slice cultures by a brief application of 10 mM glycine. Glycine-induced LTP was occluded by previous theta burst stimulation-induced potentiation, indicating that both phenomena share similar cellular processes. Glycine-induced LTP was associated with increased [3H]α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA) binding in membrane fractions as well as increased amount of a selective spectrin breakdown product generated by calpain-mediated spectrin proteolysis. Antibodies against the C-terminal (C-Ab) and N-terminal (N-Ab) domains of GluR1 subunits were used to evaluate structural changes in AMPA receptor properties resulting from glycine-induced LTP. No quantitative or qualitative changes were observed in Western blots from membrane fractions prepared from glycine-treated slices with C-Ab. In contrast, Western blots stained with N-Ab revealed the formation of a 98-kDa species of GluR1 subunits as well as an increased amount of immunoreactivity after glycine-induced LTP. The amount of spectrin breakdown product was positively correlated with the amount of the 98-kDa species of GluR1 after glycine treatment. Functional modifications of AMPA receptors were evaluated by determining changes in the effect of pressure-applied AMPA on synaptic responses before and after glycine-induced LTP. Glycine treatment produced a significant increase in AMPA receptor function after potentiation that correlated with the degree of potentiation. The results indicate that LTP induction produces calpain activation, truncation of the C-Ab domain of GluR1 subunits of AMPA receptors, and increased AMPA receptor function. They also suggest that insertion of new receptors takes place after LTP induction. 相似文献
54.
Shahriar Shahi Saeed Rahimi Hamid Reza Yavari Negin Ghasemi Fereshte Ahmadi 《Journal of endodontics》2018,44(10):1462-1466
Introduction
Previous studies have reported that it is difficult to obtain proper anesthesia in mandibular molars with symptomatic irreversible pulpitis, and supplemental injections are usually unavoidable. The aim of the present study was to determine the anesthetic efficacy of articaine in mandibular first molars with symptomatic irreversible pulpitis with 3 injection methods: an inferior alveolar nerve block (IANB), an IANB with an intraligamentary injection, and an IANB with buccal infiltration before initiating the endodontic treatment.Methods
Ninety-six patients (54 women and 42 men) with a diagnosis of symptomatic irreversible pulpitis in mandibular first molars were selected and randomly assigned into 3 groups (n = 32) according to the injection method as follows: group 1, a conventional IANB injection; group 2, an IANB injection, and after profound lip numbness after the IANB (after 15 minutes), buccal infiltration was administered; and group 3, an IANB injection, and after profound lip numbness after the IANB (after 15 minutes), an intraligamentary injection was performed, and after 20 minutes from the IANB, the endodontic treatment was initiated. The anesthetic solution was articaine 4% with 1:100,000 epinephrine. Success was defined as no or mild pain on the basis of the visual analog scale recording upon access cavity preparation or initial instrumentation. Data were statistically analyzed using the chi-square and Mann-Whitney U tests, and P < .05 was set as significant.Results
The success rate for IANBs with an intraligamentary injection was 75%, and for IANBs with a buccal injection, it was 65.6%. For IANBs alone, the success rate was 28.1%.Conclusions
Considering the limitations of the present study, in can be concluded that the success rate of IANBs increased with intraligamentary injections and buccal infiltrations with articaine that were performed before initiating treatment. Also, none of the injection methods showed complete success in anesthesia in all patients. 相似文献55.
56.
57.
Ventricular tachycardia and fibrillation are major causes of morbidity and mortality after myocardial infarction. Frequently, sudden cardiac death is the first manifestation of such malignant rhythms. Optimal risk stratification strategies in this population are of utmost importance. In this review the authors discuss the background and clinical use of invasive tests, such as electrophysiologic study and implantable loop recorders, and noninvasive tests, such as signal-averaged electrocardiography, heart rate variability, and T-wave alternans. The utility, indications, and limitations of each test in clinical practice are discussed, especially for the purpose of postmyocardial infarction risk stratification in the elderly population. 相似文献
58.
AIM: To assess the prevalence of clinically significant lesions in patients with minimal bright red bleeding per rectum (BRBPR). METHODS: Consecutive outpatients prospectively underwent colonoscopy at Loghman Hakim Hospital, Tehran. Minimal BRBPR was defined as small amounts of red blood after wiping or in the toilet bowl. Patients with the following alarm signs were excluded: Positive personal history of colorectal neoplasms or inflammatory bowel disease (IBD), positive first degree family history of colorectal neoplasms, history of altered bowel habits, recent significant weight loss, and presence of iron deficiency anemia. Neoplastic polyps, colorectal carcinoma, and IBD were defined as significant lesions. RESULTS: A total of 402 patients (183 female and 219 male, aged 43.6 ± 15.7 years) were studied. Hemorrhoids (54.2%), anal fissures (14.2%) and ul- cerative colitis (14.2%) were the most common lesions and colonoscopy was normal in 8.0%. Significant lesions were found in 121 (30.1%) patients, including 26 patients (6.5%) with adenocarcinoma and 30 (7.5%) with adenomatous polyps. Almost all patients with significant lesions had at least one lesion in the distal colon; an adenocarcinoma and an adenomatous polyp in the proximal colon were found in 2 patients with hemorrhoids. CONCLUSION: Flexible sigmoidoscopy appears to be sufficient for the evaluation of average risk patients with minimal BRBPR. Rigid sigmoidoscopy may be used as an alternative in patients less than 40 years of age in settings where the former is not available. Thechoice of colonoscopy over flexible sigmoidoscopy in patients aged over 50 years should be individualized. 相似文献
59.
Bozkurt M Canbay S Neves GF Aktüre E Fidan E Salamat MS Başkaya MK 《Acta neurochirurgica》2012,154(7):1235-1239
Background
For successful DREZ (dorsal root entry zone) surgery, optimal neuroanatomical orientation and precise microsurgical dissection are required. Although cervical, lumbar, and sacral spinal segments have been studied in detail, such information is not available for thoracic segments. The objective of this anatomical study is to comprehensively illustrate the microanatomical features of the thoracic DREZs and their variations. 相似文献60.
BackgroundSimple hand lacerations (not involving bones, tendons, nerves, or vessels) are a common emergency department (ED) complaint. Whilst the practices of irrigation, debridement, foreign body removal, and suture repair are well accepted, the use of prophylactic antibiotics is not. Without evidenced-based guidelines, practice is left to physician preference.ObjectivesThe aim of this study was to assess the need for, and the feasibility to perform, a randomised controlled trial to evaluate the role of prophylactic antibiotics in simple hand lacerations.MethodsThe study was done in three phases: (1) estimation of the national ED burden of simple hand lacerations and the use of antibiotic prophylaxis; (2) assessment of indications for antibiotic prophylaxis and (3) investigation of patient willingness to enrol in a randomised controlled trial and their preferred outcomes from simple hand lacerations. For Phase 1, we analysed the 2007 National Hospital Ambulatory Medical Care Survey. For Phase 2, we surveyed ED physicians in three urban teaching institutions (two in Brooklyn, NY and one in Washington, DC). For Phase 3, we surveyed ED patients at the same three institutions.ResultsPhase 1: out of 116.8 million ED visits nationally in 2007, 1.8 million (1.6%) were due to simple hand lacerations, of which 1.3 million (71%) required repair. Of those repaired, 27% (95% CI, 19–35%) were prescribed prophylactic antibiotics, most commonly cephalexin (73%). Phase 2: out of 108 providers surveyed, 69 (64%) responded. 16% (95% CI, 9–27%) reported prescribing prophylactic antibiotics routinely, most commonly cephalexin (84%, 95% CI, 67–93%). The degree of contamination was the most important factor (91%, 95% CI, 82–96%) in the physicians’ decision to prescribe antibiotics. Phase 3: of the 490 patients surveyed, 64% (95% CI, 60–68%) expressed interest in participating in a study to evaluate the use of prophylactic antibiotics. Their primary concern was prevention of infection (77%, 95% CI, 73–81%).ConclusionSimple hand lacerations represent a substantial number of ED visits in the United States. Absence of clear guidelines, disparity in physician practice, and patient interest in infection prevention all support performing a prospective randomised controlled trial to establish the role of antibiotic prophylaxis in simple hand lacerations. 相似文献