首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   520篇
  免费   31篇
  国内免费   3篇
耳鼻咽喉   3篇
儿科学   14篇
妇产科学   15篇
基础医学   87篇
口腔科学   16篇
临床医学   62篇
内科学   79篇
皮肤病学   7篇
神经病学   44篇
特种医学   52篇
外科学   79篇
综合类   4篇
预防医学   16篇
眼科学   4篇
药学   18篇
中国医学   2篇
肿瘤学   52篇
  2024年   2篇
  2023年   6篇
  2022年   6篇
  2021年   20篇
  2020年   6篇
  2019年   14篇
  2018年   28篇
  2017年   15篇
  2016年   9篇
  2015年   12篇
  2014年   21篇
  2013年   21篇
  2012年   36篇
  2011年   42篇
  2010年   24篇
  2009年   15篇
  2008年   41篇
  2007年   30篇
  2006年   28篇
  2005年   23篇
  2004年   30篇
  2003年   28篇
  2002年   19篇
  2001年   8篇
  2000年   3篇
  1999年   4篇
  1998年   3篇
  1997年   2篇
  1996年   3篇
  1995年   1篇
  1994年   3篇
  1993年   1篇
  1992年   4篇
  1991年   2篇
  1990年   3篇
  1989年   2篇
  1988年   1篇
  1987年   5篇
  1986年   4篇
  1985年   1篇
  1984年   2篇
  1983年   2篇
  1982年   2篇
  1981年   5篇
  1980年   6篇
  1979年   2篇
  1978年   3篇
  1977年   3篇
  1937年   2篇
  1936年   1篇
排序方式: 共有554条查询结果,搜索用时 15 毫秒
101.
Objective. The spread of malignant neoplasms is closely associated with matrix and basement membrane degradation, mediated by various classes of proteolytic enzymes. Matrix metalloproteinases (MMP) appear to have a key role in the sequence of events that lead to local invasion and metastasis. The present study evaluated the role of matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinases-2 (TIMP-2), and membrane-type metalloproteinase (MT1-MMP) in cervical neoplasia.Methods. We have analyzed 49 uterine cervical squamous cell carcinomas, 10 cases of high-grade cervical intraepithelial neoplasia (CIN II–III), and 10 control cervices for the presence of MMP-2, TIMP-2, and MT1-MMP using in situ hybridization. MMP-2 protein expression was evaluated using immunohistochemistry. Results were analyzed for possible correlation with disease outcome.Results. MMP-2, TIMP-2, and MT1-MMP mRNA were localized to both stromal and tumor cells. However, an intense signal for MMP-2 was detected almost exclusively in tumor cells and was uniformly absent from CIN lesions and control cervices. Conversely, intense signals for TIMP-2 and MT1-MMP were detected in both stromal and tumor cells of invasive carcinomas, more often for the former. As with MMP-2, they were absent from CIN lesions. MMP-2 protein expression was enhanced in tumor cells compared to CIN cases and controls, significantly compared to the latter (P = 0.01). The presence of both MMP-2 and TIMP-2 mRNA in tumor cells correlated with advanced stage (P = 0.003 for MMP-2, P = 0.002 for TIMP-2) and with poor survival (P = 0.003 for MMP-2, P = 0.002 for TIMP-2) in univariate analysis. In addition, their presence in tumor cells intercorrelated (P = 0.002). In multivariate survival analysis, MMP-2 presence retained its association with survival (P = 0.004), in addition to patient age (P = 0.027) and advanced stage (P = 0.0002).Conclusions. Both MMP-2 and TIMP-2 have a key role in extracellular matrix invasion in cervical carcinoma, largely through their elaboration by tumor cells. The presence of mRNA for both proteins is interrelated and is associated with poor survival.  相似文献   
102.
In contrast to previous studies, Ljung et al. provide evidence of permanent cognitive consequences of bilateral intrahippocampal depth electrodes for verbal memory in patients who were not operated or operated in the right temporal lobe. Stimulated by this, we provide historical confirmatory and supplementary evidence of the detrimental effect of bilateral depth electrodes implanted along the longitudinal axis of the hippocampus on verbal learning and especially on delayed verbal memory and recognition performance. This is demonstrated in 31 patients with memory assessments before implantation, after explantation, and 3 months later after left/right temporal lobe surgery. After surgery, significant recovery from postimplantation impairment is found in right temporal patients. Left temporal resection patients stay on the level seen after implantation and do not recover. Surgery, however, has its own effects in addition to the implantation. Intracranial electrodes for electroencephalographic monitoring or electrical stimulation are commonly and increasingly used for diagnosis or treatment in pharmacoresistant epilepsies. Thus, the monitoring of invasive stereotactic approaches is recommended to find safe procedures for the patients. In response to the findings, we restricted indications and used different implantation schemes, different trajectories, and targets to minimize the risk of additional damage.  相似文献   
103.
104.
Culicoides debilipalpis, C insignis, C. lahillei, and C venezuelensis are reported for the first time for Bolivia. The geographical distribution of C. paraensis extends to the Tarija Department.  相似文献   
105.

Introduction

Previous studies demonstrated that the lactose-binding protein (hepatocellular carcinoma?Cintestine?Cpancreas and pancreatitis-associated proteins (HIP/PAP)) is upregulated >130 times in peritumoral pancreatic tissue as compared to normal pancreatic tissue. Therefore, we developed a new radiolabeled ligand of HIP/PAP, the ethyl-??-d-galactopyranosyl-(1,4??)-2??-deoxy-2??-[18F]fluoro-??-d-glucopyranoside (Et-[18F]FDL) for noninvasive imaging of pancreatic carcinoma using positron emission tomography and computerized tomography (PET/CT).

Methods

The novel precursor and radiolabeling methods for synthesis of Et-[18F]FDL produced no isomers; the average decay-corrected radiochemical yield was 68%, radiochemical purity >99%, and specific activity >74 GBq/µmol. The radioligand properties of Et-[18F]FDL were evaluated using an ex vivo autoradiography and immunohistochemistry in pancreatic tissue sections obtained from mice-bearing orthotopic pancreatic tumor xenografts.

Results and Discussion

Et-[18F]FDL binding to peritumoral pancreatic tissue sections strongly correlated with HIP/PAP expression (r?=?0.81) and could be completely blocked by treatment with 1 mM lactose.

Conclusion

These results suggest that Et-[18F]FDL is a promising agent which should be evaluated for detection of early pancreatic carcinomas by PET/CT imaging.  相似文献   
106.
The purpose of this study was to evaluate poly(L ‐glutamic acid)‐benzyl‐DTPA–Gd (PG–Gd), a new biodegradable macromolecular magnetic resonance imaging contrast agent, for its pharmacokinetics and MRI enhancement in nonhuman primates. Studies were performed in rhesus monkeys at intravenous doses of 0.01, 0.02 and 0.08 mmol Gd/kg. T1‐weighted MR images were acquired at 1.5 T using fast spoiled gradient recalled echo and fast spin echo imaging protocols. The small‐molecule contrast agent Magnevist was used as a control. PG–Gd in the monkey showed a bi‐exponential disposition. The initial blood concentrations within 2 h of PG–Gd administration were much higher than those for Magnevist. The high blood concentration of PG–Gd was consistent with the MR imaging data, which showed prolonged circulation of PG–Gd in the blood pool. Enhancement of blood vessels and organs with a high blood perfusion (heart, liver, and kidney) was clearly visualized at 2 h after contrast injection at the three doses used. A greater than proportional increase of the area under the blood concentration–time curve was observed when the administered single dose was increased from 0.01 to 0.08 mmol/kg. By 2 days after PG–Gd injection, the contrast agent was mostly cleared from all major organs, including kidney. The mean residence time was 15 h at the 0.08 mmol/kg dose. A similar pharmacokinetic profile was observed in mice, with a mean residence time of 5.4 h and a volume of distribution at steady‐state of 85.5 ml/kg, indicating that the drug was mainly distributed in the blood compartment. Based on this pilot study, further investigations on the potential systemic toxicity of PG–Gd in both rodents and large animals are warranted before testing this agent in humans. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
107.
Analysis of images from live-cell experiments is a central activity to studying the effects of stimulation on neuronal behavior. Image analysis techniques currently used to study these effects rely for the most part on the salience of the neuronal structures within the image. In both fluorescent and electron microscopy, neuronal structures are enhanced and therefore easy to distinguish in an image. Unlike images obtained via fluorescent or electron microscopy, however, images produced via transmission microscopy (e.g., bright field, phase contrast, DIC) are significantly more difficult to analyze because there is little contrast between the object-of-interest and the image background. This difficulty is amplified when a time-dependent sequence of images are to be analyzed, because of the corresponding large data sets. To address this problem, we introduce a novel approach to the analysis of images of live cells captured via transmission microscopy that takes advantage of commercially available software and the Fourier transform. Specifically, our approach utilizes several morphological functions in MATLAB to enhance the contrast of the cells with respect to the background, which is followed by 2-D Fourier analysis to generate a spectrum from which the orientation and alignment of cells and their processes can be measured. We show that this method can be used to simplify the interpretation of complex structure in images of live neurons obtained via transmission microscopy and consequently, discover trends in neurite development following different types of stimulation. This approach provides a consistent and reliable tool for analyzing changes in cell structure that occurs during live-cell experiments.  相似文献   
108.
Gemcitabine, while a standard treatment of advanced pancreatic cancer (PaCa), alone is not very effective. New agents that are safe and effective are highly needed. Resveratrol is one such agent which is safe and multitargeted; and has been linked with suppression of survival, proliferation, invasion and angiogenesis of cancer. Whether resveratrol can sensitize PaCa to gemcitabine in vitro and in vivo was investigated. We established PaCa xenografts in nude mice, randomized into 4 groups, and treated with vehicle, gemcitabine, resveratrol and with combination. Modulation of NF‐κB and markers of proliferation, angiogenesis and invasion were ascertained using electrophoretic mobility shift assay (EMSA), immunohistochemistry and western blot analysis. Resveratrol inhibited the proliferation of 4 different human PaCa cell lines, synergized the apoptotic effects of gemcitabine, inhibited the constitutive activation of NF‐κB and expression of bcl‐2, bcl‐xL, COX‐2, cyclin D1 MMP‐9 and VEGF. In an orthotopic model of human PaCa, we found that resveratrol significantly suppressed the growth of the tumor (p < 0.001) and this effect was further enhanced by gemcitabine (p < 0.001). Both the markers of proliferation index Ki‐67 and the micro vessel density CD31 were significantly downregulated in tumor tissue by the combination of gemcitabine and resveratrol (p < 0.001 vs. control; p < 0.01 vs. gemcitabine). As compared to vehicle control, resveratrol also suppressed the NF‐κB activation and expression of cyclin D1, COX‐2, ICAM‐1, MMP‐9 and survivin. Overall our results demonstrate that resveratrol can potentiate the effects of gemcitabine through suppression of markers of proliferation, invasion, angiogenesis and metastasis.  相似文献   
109.
110.
Despite the current standard of multimodal management, glioblastoma (GBM) inevitably recurs and effective therapy is not available for recurrent disease. A subset of tumor cells with stem‐like properties, termed GBM stem‐like cells (GSCs), are considered to play a role in tumor relapse. Although oncolytic herpes simplex virus (oHSV) is a promising therapeutic for GBM, its efficacy against recurrent GBM is incompletely characterized. Transforming growth factor beta (TGF‐β) plays vital roles in maintaining GSC stemness and GBM pathogenesis. We hypothesized that oHSV and TGF‐β inhibitors would synergistically exert antitumor effects for recurrent GBM. Here we established a panel of patient‐derived recurrent tumor models from GBMs that relapsed after postsurgical radiation and chemotherapy, based on GSC‐enriched tumor sphere cultures. These GSCs are resistant to the standard‐of‐care temozolomide but susceptible to oHSVs G47Δ and MG18L. Inhibition of TGF‐β receptor kinase with selective targeted small molecules reduced clonogenic sphere formation in all tested recurrent GSCs. The combination of oHSV and TGF‐βR inhibitor was synergistic in killing recurrent GSCs through, in part, an inhibitor‐induced JNK‐MAPK blockade and increase in oHSV replication. In vivo, systemic treatment with TGF‐βR inhibitor greatly enhanced the antitumor effects of single intratumoral oHSV injections, resulting in cures in 60% of mice bearing orthotopic recurrent GBM. These results reveal a novel synergistic interaction of oHSV therapy and TGF‐β signaling blockade, and warrant further investigations aimed at clinical translation of this combination strategy for GBM patients.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号