全文获取类型
收费全文 | 1357篇 |
免费 | 97篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 41篇 |
妇产科学 | 13篇 |
基础医学 | 169篇 |
口腔科学 | 200篇 |
临床医学 | 111篇 |
内科学 | 181篇 |
皮肤病学 | 24篇 |
神经病学 | 100篇 |
特种医学 | 50篇 |
外科学 | 207篇 |
综合类 | 17篇 |
一般理论 | 1篇 |
预防医学 | 141篇 |
眼科学 | 10篇 |
药学 | 87篇 |
中国医学 | 2篇 |
肿瘤学 | 87篇 |
出版年
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 14篇 |
2018年 | 19篇 |
2017年 | 17篇 |
2016年 | 24篇 |
2015年 | 29篇 |
2014年 | 23篇 |
2013年 | 31篇 |
2012年 | 47篇 |
2011年 | 53篇 |
2010年 | 13篇 |
2009年 | 20篇 |
2008年 | 53篇 |
2007年 | 48篇 |
2006年 | 47篇 |
2005年 | 63篇 |
2004年 | 68篇 |
2003年 | 63篇 |
2002年 | 65篇 |
2001年 | 51篇 |
2000年 | 55篇 |
1999年 | 49篇 |
1998年 | 11篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 28篇 |
1991年 | 33篇 |
1990年 | 33篇 |
1989年 | 29篇 |
1988年 | 34篇 |
1987年 | 28篇 |
1986年 | 20篇 |
1985年 | 25篇 |
1984年 | 26篇 |
1983年 | 24篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 24篇 |
1978年 | 10篇 |
1976年 | 10篇 |
1975年 | 17篇 |
1974年 | 16篇 |
1973年 | 16篇 |
1972年 | 12篇 |
1969年 | 14篇 |
1966年 | 12篇 |
排序方式: 共有1454条查询结果,搜索用时 15 毫秒
31.
32.
33.
Tumor Vascularity Is Not a Prognostic Factor for Malignant Melanoma of the Skin 总被引:1,自引:4,他引:1 下载免费PDF全文
Klaus J. Busam Marianne Berwick Karen Blessing Katrin Fandrey Sewon Kang Themis Karaoli Judy Fine Alistair J. Cochran Wain L. White Jason Rivers David E. Elder Duan-Ren Po Wen Bradley H. Heyman Raymond L. Barnhill 《The American journal of pathology》1995,147(4):1049-1056
Tumor vascularity has been proposed as a prognostic indicator for a number of solid tumors. Although a correlation between microvessel number and metastatic behavior has also been suggested for cutaneous melanoma, the small number of cases studied to date allows one to draw only preliminary conclusions. In this study, we have assessed tumor vascularity in cutaneous melanoma by comparing 60 cases of metastasizing and non-metastasizing tumors matched for tumor thickness, age, sex, and anatomic site. Ulex europaeus agglutinin I appeared to be the most suitable vascular marker for this study. Our results indicate that there was no statistically significant difference between the two groups with regard to tumor vascularity. Even after identifying 15 cases of thin (<1.0 mm thick) melanoma, there was no significant difference in the number of microvessels between metastasizing and non-metastasizing tumors. Comparison of patterns of vascular microarchitecture also failed to discriminate between the two groups. Thus, our results indicate that tumor vascularity may not be an independent prognostic factor for cutaneous melanoma. 相似文献
34.
The BOLD hemodynamic response in healthy aging 总被引:2,自引:0,他引:2
Aizenstein HJ Clark KA Butters MA Cochran J Stenger VA Meltzer CC Reynolds CF Carter CS 《Journal of cognitive neuroscience》2004,16(5):786-793
Several previous studies have compared the blood oxygen level-dependent (BOLD) hemodynamic response (HDR) in healthy elderly subjects to the HDR in young subjects. Some studies have found a relative decreased amplitude in the elderly in the visual cortex, whereas other studies have found the elderly HDR amplitude in the visual cortex to be nearly identical to that in young subjects. A possible explanation for the different findings is that the peak voxel HDR is similar between the groups, but that the HDR in the group-averaged region-of-interest (ROI) is "washed out" by the inclusion of less significant voxels (due to a smaller extent of activation in the elderly) or by the inclusion of negative-peaking voxels. We tested this hypothesis using event-related functional magnetic resonance imaging (fMRI ). While undergoing fMRI, subjects performed a simple visual and motor task, pressing with their index fingers in response to visual presentation of the word tap. Data from 18 subjects, 8 young and 10 elderly, were analyzed. For each subject, a visual and a motor ROI was selected by choosing the most significant positive voxels within the anatomically defined ROI. This individual subject approach excluded both low-significance and negative-peaking voxels. Similar peaks were found for the elderly and the young subjects in both motor and visual regions and a more sustained BOLD response was found for the elderly in both regions. Additionally, as predicted, a greater percentage of voxels with a negative HDR was found for the elderly in the visual region; this finding was also replicated in our reanalysis of an independent fMRI and aging study from the fMRI Data Center. Functional neuroimaging observations of negative HDRs in visual areas have been interpreted as the effect of unconstrained processing during rest. Our results suggest that the elderly may have more unconstrained visual processing during the rest condition in the scanner. The observation that the group differences in the BOLD response are sensitive to voxel selection (e.g., inclusion of low-significance and/or negative voxels) underscores the importance of ROI selection criteria in the interpretation of fMRI studies using elderly populations. 相似文献
35.
Mike Fruscione Russell Kirks Allyson Cochran Keith Murphy Erin H. Baker John B. Martinie David A. Iannitti Dionisios Vrochides 《HPB : the official journal of the International Hepato Pancreato Biliary Association》2018,20(8):721-728
Background
The American College of Surgeons NSQIP® Surgical Risk Calculator (SRC) was developed to estimate postoperative outcomes. Our goal was to develop and validate an institution-specific risk calculator for patients undergoing major hepatectomy at Carolinas Medical Center (CMC).Methods
Outcomes generated by the SRC were recorded for 139 major hepatectomies performed at CMC (2008–2016). Novel predictive models for seven postoperative outcomes were constructed and probabilities calculated. Brier score and area under the curve (AUC) were employed to assess accuracy. Internal validation was performed using bootstrap logistic regression. Logistic regression models were constructed using bivariate and multivariate analyses.Results
Brier scores showed no significant difference in the predictive ability of the SRC and CMC model. Significant differences in the discriminative ability of the models were identified at the individual level. Both models closely predicted 30-day mortality (SRC AUC: 0.867; CMC AUC: 0.815). The CMC model was a stronger predictor of individual postoperative risk for six of seven outcomes (SRC AUC: 0.531–0.867; CMC AUC: 0.753–0.970).Conclusion
Institution-specific models provide superior outcome predictions of perioperative risk for patients undergoing major hepatectomy. If properly developed and validated, institution-specific models can be used to deliver more accurate, patient-specific care. 相似文献36.
Role of glutathione metabolism of Treponema denticola in bacterial growth and virulence expression 下载免费PDF全文
Hydrogen sulfide (H(2)S) is a major metabolic end product detected in deep periodontal pockets that is produced by resident periodontopathic microbiota associated with the progression of periodontitis. Treponema denticola, a member of the subgingival biofilm at disease sites, produces cystalysin, an enzyme that catabolizes cysteine, releasing H(2)S. The metabolic pathway leading to H(2)S formation in periodontal pockets has not been determined. We used a variety of thiol compounds as substrates for T. denticola to produce H(2)S. Our results indicate that glutathione, a readily available thiol source in periodontal pockets, is a suitable substrate for H(2)S production by this microorganism. In addition to H(2)S, glutamate, glycine, ammonia, and pyruvate were metabolic end products of metabolism of glutathione. Cysteinyl glycine (Cys-Gly) was also catabolized by the bacteria, yielding glycine, H(2)S, ammonia, and pyruvate. However, purified cystalysin could not catalyze glutathione and Cys-Gly degradation in vitro. Moreover, the enzymatic activity(ies) in T. denticola responsible for glutathione breakdown was inactivated by trypsin or proteinase K, by heating (56 degrees C) and freezing (-20 degrees C), by sonication, and by exposure to N alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK). These treatments had no effect on degradation of cysteine by the purified enzyme. In this study we delineated an enzymatic pathway for glutathione metabolism in the oral spirochete T. denticola; our results suggest that glutathione metabolism plays a role in bacterial nutrition and potential virulence expression. 相似文献
37.
Tosatti S Schwartz Z Campbell C Cochran DL VandeVondele S Hubbell JA Denzer A Simpson J Wieland M Lohmann CH Textor M Boyan BD 《Journal of biomedical materials research. Part A》2004,68(3):458-472
Osteoblasts exhibit a more differentiated morphology on surfaces with rough microtopographies. Surface effects are often mediated through integrins that bind the RGD motif in cell attachment proteins. Here, we tested the hypothesis that modulating access to RGD binding sites can modify the response of osteoblasts to surface microtopography. MG63 immature osteoblast-like cells were cultured on smooth (Ti sputter-coated Si wafers) and rough (grit blasted/acid etched) Ti surfaces that were modified with adsorbed monomolecular layers of a comb-like graft copolymer, poly-(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG), to limit nonspecific protein adsorption. PLL-g-PEG coatings were functionalized with varying amounts of an integrin-receptor-binding RGD peptide GCRGYGRGDSPG (PLL-g-PEG/PEG-RGD) or a nonbinding RDG control sequence GCRGYGRDGSPG (PLL-g-PEG/PEG-RDG). Response to PLL-g-PEG alone was compared with response to surfaces on which 2-18% of the polymer sidechains were functionalized with the RGD peptide or the RDG peptide. To examine RGD dose-response, peptide surface concentration was varied between 0 and 6.4 pmol/cm(2). In addition, cells were cultured on uncoated Ti or Ti coated with PLL-g-PEG or PLL-g-PEG/PEG-RGD at an RGD surface concentration of 0.7 pmol/cm(2), and free RGDS was added to the media to block integrin binding. Analyses were performed 24 h after cultures had achieved confluence on the tissue culture plastic surface. Cell number was reduced on smooth Ti compared to plastic or glass and further decreased on surfaces coated with PLL-g-PEG or PLL-g-PEG/PEG-RDG, but was restored to control levels when PLL-g-PEG/PEG-RGD was present. Alkaline phosphatase specific activity and osteocalcin levels were increased on PLL-g-PEG alone or PLL-g-PEG/PEG-RDG, but PLL-g-PEG/PEG-RGD reduced the parameters to control levels. On rough Ti surfaces, cell number was reduced to a greater extent than on smooth Ti. PLL-g-PEG coatings reduced alkaline phosphatase and increased osteocalcin in a manner that was synergistic with surface roughness. The RDG peptide did not alter the PLL-g-PEG effect but the RGD peptide restored these markers to their control levels. PLL-g-PEG coatings also increased TGF-beta1 and PGE(2) in conditioned media of cells cultured on smooth or rough Ti; there was a 20x increase on rough Ti coated with PLL-g-PEG. PLL-g-PEG effects were inhibited dose dependently by addition of the RGD peptide to the surface. Free RGDS did not decrease the effect elicited by PLL-g-PEG surfaces. These unexpected results suggest that PLL-g-PEG may have osteogenic properties, perhaps correlated with effects that alter cell attachment and spreading, and promote a more differentiated morphology. 相似文献
38.
Expression of PKC-beta or cyclin D2 predicts for inferior survival in diffuse large B-cell lymphoma. 总被引:6,自引:0,他引:6
Christine P Hans Dennis D Weisenburger Timothy C Greiner Wing C Chan Patricia Aoun Gregory T Cochran Zenggang Pan Lynette M Smith James C Lynch Robert Gregory Bociek Philip J Bierman Julie M Vose James O Armitage 《Modern pathology》2005,18(10):1377-1384
We sought to determine whether identification of poor-risk subgroups of diffuse large B-cell lymphoma (DLBCL) using immunohistochemical stains would have practical utility with regard to prognosis and therapeutic decisions. Tissue microarray blocks were created using replicate samples of formalin-fixed, paraffin-embedded tissue from 200 cases of de novo DLBCL. The sections were stained with antibodies to proteins that are expressed by activated or proliferating B cells including MUM1, FOXP1, bcl-2, survivin, protein kinase C-beta (PKC-beta), cyclin D2, cyclin D3, and Ki-67. In univariate analysis, tumor expression of cyclin D2 (P = 0.025) or PKC-beta (P = 0.015) was associated with a worse overall survival, whereas none of the other markers was predictive of overall survival. Patients with DLBCL that expressed either cyclin D2 or PKC-beta had a 5-year overall survival of only 30% as compared to 52% for those who were negative for both markers (P = 0.0019). In multivariate analysis, the expression of cyclin D2 or PKC-beta was an independent predictor of poor overall survival (P = 0.035). Cyclin D2 and PKC-beta expression will be useful in designing a 'biological prognostic index' for patients with DLBCL. 相似文献
39.
Patricia A. Smiley Lindsey C. Partington Caroline R. Cochran Jessica L. Borelli 《Developmental psychobiology》2020,62(8):1134-1149
Parental socialization that infringes on children's autonomy may have consequences for physiological regulation, trait anxiety, and state distress. One such practice is the use of positive conditional regard (CR)—the provision of extra attention/affection when children meet parents’ expectations. Self-determination theory proposes that CR thwarts satisfaction of children's basic needs for relatedness and autonomy by placing these needs in conflict. We evaluate associations among children's (N = 106, 51% male, Mage = 10.27 years, SD = 1.09) reports of their mothers’ use of positive CR to suppress anger expression (PCR-anger), their physiological regulation (resting respiratory sinus arrhythmia, RSA), and their trait anxiety and state distress, in light of perceived relationship closeness. After controlling demographics, mothers’ reports of positive and negative CR-anger, children's reports of mothers’ negative CR-anger and depressive symptoms, greater child-reported positive CR-anger was significantly associated with greater child anxiety and with lower resting RSA. Resting RSA mediated associations of child-reported positive CR-anger with greater child anxiety and post-failure distress. These indirect effects were significant for children low or moderate in closeness to mother. We conclude that autonomy-restrictive socialization is a concurrent correlate of children's physiological regulation, anxiety, and state distress, with these associations dependent on relational distance. 相似文献
40.
A genomic map of infectious laryngotracheitis virus and the sequence and organization of genes present in the unique short and flanking regions 总被引:9,自引:0,他引:9
We present a genomic map of infectious laryngotracheitis virus (ILT) and an 18,912 bp sequence containing the entire unique short region and a portion of the flanking short repeats. In determining the genomic map, an 856 bp region repeated as many as 13 times was identified within the short repeats. The unique short sequence contains nine potential open reading frames (ORFs). Six of these ORFs show homology to other known herpesvirus unique short genes. Using the herpes simplex virus nomenclature, these genes are the US2, protein kinase, and glycoproteins G, D, I, and E (ORF 1, 2, 4, 6, 7, and 8, respectively). Interestingly, an open reading frame with homology to HSV-1 UL47 (ORF 3) is found in the unique short. One very large open reading frame (ORF 5) is present and contains a threonine-rich, degenerate repeat sequence. This gene appears to be unique to ILT among sequenced herpesviruses. Two ORFs were identified within the short repeat (SR) region. SRORF 1 is homologous to a gene (SORF3) found in the unique short region in both MDV and HVT, and appears to be specific to avian herpesviruses. SRORF 2 has homology to HSV US10.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence data-base and have been assigned the accession number U28832. 相似文献