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   701篇
  免费   53篇
  国内免费   2篇
耳鼻咽喉   16篇
儿科学   26篇
妇产科学   7篇
基础医学   70篇
口腔科学   6篇
临床医学   64篇
内科学   167篇
皮肤病学   21篇
神经病学   25篇
特种医学   32篇
外科学   68篇
综合类   20篇
预防医学   14篇
眼科学   57篇
药学   81篇
中国医学   3篇
肿瘤学   79篇
  2023年   5篇
  2022年   13篇
  2021年   16篇
  2020年   14篇
  2019年   11篇
  2018年   12篇
  2017年   13篇
  2016年   16篇
  2015年   27篇
  2014年   24篇
  2013年   32篇
  2012年   45篇
  2011年   59篇
  2010年   38篇
  2009年   23篇
  2008年   38篇
  2007年   51篇
  2006年   42篇
  2005年   23篇
  2004年   27篇
  2003年   26篇
  2002年   17篇
  2001年   15篇
  2000年   18篇
  1999年   22篇
  1998年   6篇
  1997年   8篇
  1996年   6篇
  1995年   4篇
  1994年   4篇
  1993年   3篇
  1992年   6篇
  1991年   7篇
  1990年   8篇
  1987年   3篇
  1986年   3篇
  1985年   6篇
  1983年   2篇
  1979年   3篇
  1978年   6篇
  1977年   2篇
  1975年   2篇
  1974年   2篇
  1973年   3篇
  1971年   8篇
  1970年   8篇
  1969年   5篇
  1968年   2篇
  1967年   3篇
  1966年   6篇
排序方式: 共有756条查询结果,搜索用时 15 毫秒
91.

Objective:

To evaluate the in vitro cytotoxicity and antibacterial properties of Cassia occidentalis (whole plant) via alcoholic, hydro-alcoholic, and aqueous extracts against eight human cancer cell lines from six different tissues and four bacterial strains.

Material and Methods:

in vitro cytotoxicity against the human cancer cells, cultured for 48h in presence of different concentrations C. occidentalis extracts and percentage of cell viability, was evaluated using the sulforhodamine-B (SRB) assay. The antibacterial activity was performed using the standard protocol against bacterial strains.

Results:

It was observed that aqueous extract of C. occidentalis (whole plant) had more potential than hydro-alcoholic and alcoholic extracts against HCT-15, SW-620, PC-3, MCF-7, SiHa, and OVCAR-5 human cancer cell lines at 100, 30, and 10 μg/ml in a dose-dependent manner. The hydro-alcoholic extract showed potential against Bacillus subtillis.

Conclusion:

The plant can be explored for the possible development of lead molecules for drug discovery.  相似文献   
92.
PurposeTo evaluate demographic trends of open globe injuries (OGIs) using a large dataset representative of United States population.MethodsRetrospective cross-sectional observational study using the National Inpatient Sample (NIS) database from 2002 to 2013. Only patients with a primary admitting diagnosis of OGI were included. Data included age (in years), gender, race, type of OGI, death rate and length and cost of stay.ResultsDuring the 12-year period, 27,467 adults (age > 20) with acute OGIs were admitted to the US hospitals. The incidence of OGIs in the adult US population was 10.6 cases per 1,000,000 persons. The mean age was 50.4 years (SD 21.52); the average ages of men and women were 44.34 (SD 17.63) and 65.69 (SD 22.77), respectively. Men accounted for 71% of all cases, with 84% of patients under 60. A decrease in the number of OGIs was seen with advancing age in men, whereas the opposite was true for women. Men, elderly over 80 and Blacks were at the highest risk of sustaining an OGI. The most and least common types of injuries were penetrating injuries (73%) and IOFBs (11%), respectively. Over half of young adults in the 21–40 cohort and 43% of men were uninsured (p < 0.001). The average length of hospital stay increased with age and was significantly much higher in women than men (3.4 vs 2.5 days).ConclusionsRacial, gender and age disparities are prevalent in patients with OGIs. Although the majority of cases were seen in Whites and young men age 21–40 years, the incidence of OGIs per 1,000,000 persons per year was the highest in Blacks and Hispanics, elderly over 80, and men. One-third of all cases were uninsured. These disparities should be the basis of future public health safety measures.Subject terms: Epidemiology, Education  相似文献   
93.
94.
95.

Purpose

To assess the performance of a 3D fast spin echo (FSE) pulse sequence utilizing out‐of‐slab cancellation through phase alternation and micro‐magnetic resonance imaging (μMRI)‐based virtual bone biopsy processing methods to probe the serial reproducibility and sensitivity of structural and mechanical parameters of the distal tibia at 7.0T.

Materials and Methods

The distal tibia of five healthy subjects was imaged at three timepoints with a 3D FSE sequence at 137 × 137 × 410 μm3 voxel size. Follow‐up images were retrospectively 3D registered to baseline images. Coefficients of variation (CV) and intraclass correlation coefficients (ICCs) for measures of scale and topology of the whole tibial trabecular bone (TB) cross‐section as well as finite‐element‐derived Young's and shear moduli of central cuboidal TB subvolumes (8 × 8 × 5 mm3) were evaluated as measures of reproducibility and reliability. Four additional cubic TB subregions (anterior, medial, lateral, and posterior) of similar dimensions were extracted and analyzed to determine associations between whole cross‐section and subregional structural parameters.

Results

The mean signal‐to‐noise ratio (SNR) over the 15 image acquisitions was 27.5 ± 2.1. Retrospective registration yielded an average common analysis volume of 67% across the three exams per subject. Reproducibility (mean CV = 3.6%; range, 1.5%–5%) and reliability (ICCs, 0.95–0.99) of all parameters permitted parameter‐based discrimination of the five subjects in spite of the narrow age range (26–36 years) covered. Parameters characterizing topology were better able to distinguish two individuals who demonstrated similar values for scalar measurements (≈34% difference, P < 0.001). Whole‐section axial stiffness encompassing the cortex was superior at distinguishing two individuals relative to its central subregional TB counterpart (≈8% difference; P < 0.05). Interregion comparisons showed that although all parameters were correlated (mean R2 = 0.78; range 0.57–0.99), the strongest associations observed were those for the erosion index (mean R2 = 0.95, P ≤ 0.01).

Conclusion

The reproducibility and structural and mechanical parameter‐based discriminative ability achieved in five healthy subjects suggests that 7T‐derived μMRI of TB can be applied towards serial patient studies of osteoporosis and may enable earlier detection of disease or treatment‐based effects. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.  相似文献   
96.

Purpose

To assess the relationship between sodium signal intensity changes and oligemia, measured with perfusion‐weighted imaging (PWI), in ischemic stroke patients.

Materials and Methods

Nine ischemic stroke patients (55 ± 13 years), four with follow‐up scans, underwent sodium and proton imaging 4–32 hours after symptom onset. Relative sodium intensity was calculated as the ratio of signal intensities in core (identified as hypertintense lesions on diffusion‐weighted imaging [DWI]) or putative penumbra (PWI‐DWI mismatch) to contralateral homologous regions.

Results

Sodium intensity increases in the core were not correlated with the severity of hypoperfusion, measured with either cerebral blood flow (rho = 0.157; P = 0.61) or cerebral blood volume (rho = ?0.234; P = 0.44). In contrast, relative sodium intensity was not elevated (4–7 hours 0.96 ± 0.07; 17–32 hours 1.00 ± 0.07) in PWI‐DWI mismatch regions.

Conclusion

Sodium signal intensity cannot be predicted by the degree of hypoperfusion acutely. Sodium intensity also remains unchanged in PWI‐DWI mismatch tissue, indicating preservation of ionic homeostasis. Sodium magnetic resonance imaging (MRI), in conjunction with PWI and DWI, may permit identification of patients with viable tissue, despite an unknown symptom onset time. J. Magn. Reson. Imaging 2011;33:41–47. © 2010 Wiley‐Liss, Inc.
  相似文献   
97.

Purpose of Review

To provide an update on the pathogenesis of enteropathy-associated T cell lymphoma (EATL) and its relationship with refractory celiac disease (RCD), in light of current knowledge of immune, genetic, and environmental factors that promote neoplastic transformation of intraepithelial lymphocytes (IELs).

Recent Findings

EATL frequently evolves from RCD type II (RCD II) but can occur “de novo” in individuals with celiac disease. Recurrent activating mutations in members of the JAK/STAT pathway have been recently described in EATL and RCD II, which suggests deregulation of cytokine signaling to be an early event in lymphomagenesis. Intraepithelial T cells are presumed to be the cell of origin of EATL (and RCD II). Recent in vitro molecular and phenotypic analyses and in vivo murine studies, however, suggest an origin of RCD II from innate IELs (NK/T cell precursors), which could also be the cell of origin of RCD II-derived EATL.

Summary

The immune microenvironment of the small intestinal mucosa in celiac disease fosters the development of EATL, often in a multistep pathway.
  相似文献   
98.
Breast cancer is becoming a major concern for many South Asian women. Clinical observations of women from a South Asian community living in Canada revealed an under use of early detection strategies. The purpose of this qualitative ethnoscience study was to examine breast health practices from the perspective of South Asian women to provide a foundation for the development of culturally suitable breast health services for this group. Open-ended interviews were conducted with a convenience sample of 50 South Asian women over the age of 30 who had not been diagnosed with breast cancer. Adequate representation of the main religious groups (i.e. Sikh, Hindu, Muslim and Christian) was ensured through sampling techniques. Analysis of translated interviews involved identification of themes and the development of a taxonomy to represent relationships among emerging cultural themes and domains. Four central domains of beliefs related to breast health practices were identified: beliefs about a woman's calling, beliefs about cancer, beliefs about taking care of your breasts and beliefs about accessing services. These beliefs hold important implications for how health promotion strategies should be structured and offered, In particular, attention must be paid to the language that is used to talk about breast cancer, the importance of the role of the family in women's health decisions and traditions related to using narratives to share information and advice.  相似文献   
99.
ObjectiveThis study seeks to develop a fully automated method of generating synthetic data from a real dataset that could be employed by medical organizations to distribute health data to researchers, reducing the need for access to real data. We hypothesize the application of Bayesian networks will improve upon the predominant existing method, medBGAN, in handling the complexity and dimensionality of healthcare data.Materials and MethodsWe employed Bayesian networks to learn probabilistic graphical structures and simulated synthetic patient records from the learned structure. We used the University of California Irvine (UCI) heart disease and diabetes datasets as well as the MIMIC-III diagnoses database. We evaluated our method through statistical tests, machine learning tasks, preservation of rare events, disclosure risk, and the ability of a machine learning classifier to discriminate between the real and synthetic data.ResultsOur Bayesian network model outperformed or equaled medBGAN in all key metrics. Notable improvement was achieved in capturing rare variables and preserving association rules.DiscussionBayesian networks generated data sufficiently similar to the original data with minimal risk of disclosure, while offering additional transparency, computational efficiency, and capacity to handle more data types in comparison to existing methods. We hope this method will allow healthcare organizations to efficiently disseminate synthetic health data to researchers, enabling them to generate hypotheses and develop analytical tools. ConclusionWe conclude the application of Bayesian networks is a promising option for generating realistic synthetic health data that preserves the features of the original data without compromising data privacy.  相似文献   
100.
Oligonucleotides are being employed for gene-silencing activity by a variety of mechanisms, including antisense, ribozyme, and siRNA. In the present studies, we designed novel oligonucleotides complementary to targeted mRNAs and studied the effect of 3'-end exposure and oligonucleotide length on gene-silencing activity. We synthesized both oligoribonucleotides (RNAs) and oligodeoxynucleotides (DNAs) with phosphorothioate backbones, consisting of two identical segments complementary to the targeted mRNA attached through their 5'-ends, thereby containing two accessible 3'-ends; these compounds are referred to as gene-silencing oligonucleotides (GSOs). RNA and/or DNA GSOs targeted to MyD88, VEGF, and TLR9 mRNAs had more potent gene-silencing activity than did antisense phosphorothioate oligonucleotides (PS-oligos) in cell-based assays and in vivo. Of the different lengths of GSOs evaluated, 19-mer long RNA and DNA GSOs had the best gene-silencing activity both in vitro and in vivo. These results suggest that GSOs are novel agents for gene silencing that can be delivered systemically with broader applicability.  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