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   137836篇
  免费   12371篇
  国内免费   3631篇
耳鼻咽喉   1064篇
儿科学   1938篇
妇产科学   1378篇
基础医学   12238篇
口腔科学   4561篇
临床医学   22093篇
内科学   15234篇
皮肤病学   1457篇
神经病学   12073篇
特种医学   24894篇
外国民族医学   304篇
外科学   12379篇
综合类   18102篇
现状与发展   11篇
预防医学   5172篇
眼科学   1947篇
药学   8122篇
  72篇
中国医学   3972篇
肿瘤学   6827篇
  2024年   134篇
  2023年   1988篇
  2022年   2810篇
  2021年   4812篇
  2020年   4931篇
  2019年   4720篇
  2018年   4741篇
  2017年   4865篇
  2016年   5152篇
  2015年   5109篇
  2014年   12325篇
  2013年   11270篇
  2012年   9332篇
  2011年   9727篇
  2010年   9583篇
  2009年   9356篇
  2008年   7627篇
  2007年   6447篇
  2006年   5622篇
  2005年   4922篇
  2004年   4196篇
  2003年   3399篇
  2002年   2688篇
  2001年   2526篇
  2000年   2022篇
  1999年   1631篇
  1998年   1458篇
  1997年   1363篇
  1996年   1146篇
  1995年   1146篇
  1994年   956篇
  1993年   790篇
  1992年   685篇
  1991年   598篇
  1990年   493篇
  1989年   373篇
  1988年   370篇
  1987年   318篇
  1986年   254篇
  1985年   301篇
  1984年   263篇
  1983年   189篇
  1982年   203篇
  1981年   214篇
  1980年   175篇
  1979年   128篇
  1978年   107篇
  1977年   77篇
  1976年   103篇
  1975年   39篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
前列腺癌(prostate cancer, PCa)是中老年男性常见恶性肿瘤之一,目前尚缺乏有效的晚期癌症治疗方法,因此早期诊断对于降低PCa死亡率至关重要。近年来,较多研究开发出多种新型诊断方法以改善对PCa诊断的准确性,同时避免过度诊疗,但其有效性及实用性尚需进一步验证。本文对目前新型生物标志物、联合成像技术及风险预测模型等的早期诊断技术进行总结,以期为临床研究提供指导作用。  相似文献   
73.
目的 分析超声及应变式弹性成像预测超声引导下置入腘静脉血管鞘治疗下肢深静脉血栓形成(DVT)成功与否的价值。方法 回顾性分析103例接受超声引导下置入患侧腘静脉血管鞘的DVT患者的术前超声资料,比较置入血管鞘失败与成功病例腘静脉超声及应变式弹性成像表现差异;绘制差异有统计学意义超声参数的受试者工作特征曲线,获得其预测血管鞘置入失败的阈值,对每个参数阈值赋值1分,得到联合超声评分,以实际置入结果为标准,评价超声单一参数及联合评分的预测效能。结果 103例中,对100例行单侧、3例行双侧腘静脉置入血管鞘,包括左侧腘静脉71支、右侧35支,共106支腘静脉;对其中95支腘静脉置入血管鞘成功(成功组),11支失败(失败组)。相比成功组,失败组腘静脉内径及腘静脉与腘动脉内径比值均较小,血栓为等或高回声,与血管壁边界模糊,腘静脉应变式弹性评分为硬。以超声单一参数及联合评分预测置入血管鞘成功与否的曲线下面积分别为0.909、0.926、0.865、0.899、0.958及0.940(P均<0.001)。结论 患侧腘静脉超声及应变式弹性成像能有效预测对下肢DVT患者行超声引导下置入腘静脉血管鞘成功与否。  相似文献   
74.
目的基于功能磁共振成像分析肝豆状核变性(Wilson disease, WD)患者纹状体亚区神经功能损害及其与临床相关分析,探讨其神经心理学症状可能的致病机制。方法收集WD患者29例和健康志愿者30例,进行3.0 T磁共振功能磁共振成像及临床量表测试,采用mICA工具箱的group ICA功能将壳核和尾状核分成8个亚区,做全脑功能连接,提取功能连接异常区域的值与临床量表测试结果做相关性分析。结果与对照组相比,WD患者左侧尾状核中部与全脑未发现功能增强或减弱区域,余感兴趣区与全脑功能连接不同程度减弱。左侧尾状核前部(ROI5)-中扣带回功能连接值与简易智能状态量表(MMSE)值呈显著负相关(r=-0.47,P=0.009);右侧尾状核前部(ROI6)-中扣带回功能连接值与MMSE值呈显著负相关(r=-0.46,P=0.011);右侧尾状核中部(ROI8)-右侧岛叶功能连接值与MMSE值呈显著负相关(r=-0.38,P=0.041)。结论右侧尾状核前中部与背外侧前额叶功能连接减弱,双侧壳核前部与丘脑功能连接减弱,可能破坏皮质-纹状体-丘脑回路引起认知功能损害;参与记忆及动作相关认知的突显网络、默认模式网络的通路连接受阻则可能是WD患者认知障碍的神经病理机制。  相似文献   
75.
This study explores the feasibility of using diffusion kurtosis imaging (DKI) in the pelvic floor region and assesses the water diffusivity of the pubovisceral muscle. Twenty-seven healthy young nulliparous females underwent DKI at 3.0 T that included 15 gradient directions and three b values (0, 750, and 1500 s/mm2). The diffusion tensor and diffusion kurtosis metrics values of the pubovisceral muscle were measured after image processing. Two independent sample t-tests, a paired-samples t-test, and a nonparametric hypothesis test were performed as appropriate to compare the differences among different metrics. Twenty-six subjects (mean ± standard deviation age, 25 ± 2 years) were successfully analyzed by measuring the diffusion tensor and diffusion kurtosis metrics of the bilateral pubovisceral muscles. The metrics included mean kurtosis, axial kurtosis, radial kurtosis, fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. We found no statistically significant differences for these measurement values between the left and right pubovisceral muscles (p = 0.271–0.931). However, radial kurtosis was greater than axial kurtosis in both pubovisceral muscles (p < 0.001) and axial diffusivity was lower than radial diffusivity in both pubovisceral muscles (p < 0.001). We deem the application of DKI technology to the pelvic floor region to be feasible.  相似文献   
76.
Quantitative susceptibility mapping (QSM) has the potential for being a biomarker for various diseases because of its ability to measure tissue susceptibility related to iron deposition, myelin, and hemorrhage from the phase signal of a T2*-weighted MRI. Despite its promise as a quantitative marker, QSM is faced with many challenges, including its dependence on preprocessing of the raw phase data, the relatively weak tissue signal, and the inherently ill posed relationship between the magnetic dipole and measured phase. The goal of this study was to evaluate the effects of background field removal and dipole inversion algorithms on noise characteristics, image uniformity, and structural contrast for cerebral microbleed (CMB) quantification at both 3T and 7T. We selected four widely used background phase removal and five dipole field inversion algorithms for QSM and applied them to volunteers and patients with CMBs, who were scanned at two different field strengths, with ground truth QSM reference calculated using multiple orientation scans. 7T MRI provided QSM images with lower noise than did 3T MRI. QSIP and VSHARP + iLSQR achieved the highest white matter homogeneity and vein contrast, with QSIP also providing the highest CMB contrast. Compared with ground truth COSMOS QSM images, overall good correlations between susceptibility values of dipole inversion algorithms and the COSMOS reference were observed in basal ganglia regions, with VSHARP + iLSQR achieving the susceptibility values most similar to COSMOS across all regions. This study can provide guidance for selecting the most appropriate QSM processing pipeline based on the application of interest and scanner field strength.  相似文献   
77.
78.

Background

Limited data exist on the clinical behavior of pediatric non-rhabdomyosarcoma soft tissue sarcomas (NRSTS) with distant metastases at onset, and a clear standard of care has not yet been defined.

Methods

This cohort study reports on pediatric adult-type metastatic NRSTS enrolled in two concurrent prospective European studies, i.e., the randomized BERNIE study and the single-arm MTS 2008 study developed by the European paediatric Soft tissue sarcoma Study Group. Treatment programs were originally designed for patients with metastatic rhabdomyosarcoma, i.e., nine courses of multidrug chemotherapy (with or without bevacizumab in the BERNIE study), followed by 12 cycles of maintenance therapy, whereas radiotherapy and/or surgery (on primary tumor and/or metastases) were delayed until after seven courses of chemotherapy had been administered.

Results

The study included 61 patients <21 years old treated from July 2008 to December 2016. The lung was the site of metastases in 75% of the cases. All patients received multi-agent chemotherapy, 44% had local therapy to primary tumor, and 18% had treatment of metastases. Median time to progression/relapse was 6 months. A high rate of tumor progression was observed during the initial part of the chemotherapy program. With a median follow-up of 41.5 months (range, 2–111 months), 3-year event-free survival and overall survival were 15.4% (95% confidence interval [CI], 7.6–25.7) and 34.9% (95% CI, 22.7–47.5), respectively. There were no statistically significant differences in outcome depending on the type of treatment administered.

Conclusions

The study confirmed the overall poor outcome for patients with metastatic NRSTS, whose treatment remains a challenge.

Plain Language Summary

  • Pediatric non-rhabdomyosarcoma soft tissue sarcomas form a heterogeneous group of rare tumors.
  • Although recent international studies have defined the standard of care for patients with localized disease, limited data are available on the clinical behavior of patients with distant metastases.
  • This study on 61 metastatic cases treated on two prospective European protocols confirms that the chances of survival of such patients are often dismal and a standard treatment is still lacking.
  相似文献   
79.
80.
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