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   36801篇
  免费   2918篇
  国内免费   801篇
耳鼻咽喉   469篇
儿科学   732篇
妇产科学   757篇
基础医学   3076篇
口腔科学   552篇
临床医学   3330篇
内科学   6830篇
皮肤病学   653篇
神经病学   1009篇
特种医学   1601篇
外国民族医学   22篇
外科学   5865篇
综合类   3471篇
现状与发展   2篇
预防医学   2207篇
眼科学   597篇
药学   2378篇
  9篇
中国医学   395篇
肿瘤学   6565篇
  2024年   80篇
  2023年   1032篇
  2022年   1717篇
  2021年   2444篇
  2020年   2026篇
  2019年   2194篇
  2018年   2013篇
  2017年   1404篇
  2016年   1233篇
  2015年   1218篇
  2014年   2446篇
  2013年   2222篇
  2012年   1650篇
  2011年   1894篇
  2010年   1510篇
  2009年   1531篇
  2008年   1672篇
  2007年   1665篇
  2006年   1323篇
  2005年   1212篇
  2004年   1019篇
  2003年   886篇
  2002年   756篇
  2001年   589篇
  2000年   510篇
  1999年   449篇
  1998年   414篇
  1997年   340篇
  1996年   294篇
  1995年   268篇
  1994年   269篇
  1993年   211篇
  1992年   228篇
  1991年   206篇
  1990年   177篇
  1989年   157篇
  1988年   152篇
  1987年   130篇
  1986年   124篇
  1985年   147篇
  1984年   130篇
  1983年   88篇
  1982年   102篇
  1981年   82篇
  1980年   77篇
  1979年   61篇
  1978年   46篇
  1977年   52篇
  1976年   31篇
  1975年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This study aimed at evaluating how encapsulation in a regular nanocarrier (NC) (providing extended circulation time) or in a brain-targeting NC (providing prolonged circulation time and increased brain uptake) may influence the therapeutic index compared with the unformulated drug and to explore the key parameters affecting therapeutic performance using a model-based approach. Pharmacokinetic (PK) models were built with chosen PK parameters. For a scenario where central effect depends on area under the unbound brain concentration curve and peripheral toxicity relates to peak unbound plasma concentration, dose-effect and drug-side effect curves were constructed, and the therapeutic index was evaluated. Regular NC improved the therapeutic index compared with the unformulated drug due to reduced peripheral toxicity, while brain-targeting NC enhanced the therapeutic index by lowering peripheral toxicity and increasing central effect. Decreasing drug release rate or systemic clearance of NC with drug still encapsulated could increase the therapeutic index. Also, a drug with shorter half-life would therapeutically benefit more from a NC encapsulation. This work provides insights into how a NC for brain delivery should be optimized to maximize the therapeutic performance and is helpful to predict if and to what extent a drug with certain PK properties would obtain therapeutic benefit from nanoencapsulation.  相似文献   
52.
Accurately predicting the hepatic clearance of compounds using in vitro to in vivo extrapolation (IVIVE) is crucial within the pharmaceutical industry. However, several groups have recently highlighted the serious error in the process. Although empirical or regression-based scaling factors may be used to mitigate the common underprediction, they provide unsatisfying solutions because the reasoning behind the underlying error has yet to be determined. One previously noted trend was intrinsic clearance-dependent underprediction, highlighting the limitations of current in vitro systems. When applying these generated in vitro intrinsic clearance values during drug development and making first-in-human dose predictions for new chemical entities though, hepatic clearance is the parameter that must be estimated using a model of hepatic disposition, such as the well-stirred model. Here, we examine error across hepatic clearance ranges and find a similar hepatic clearance-dependent trend, with high clearance compounds not predicted to be so, demonstrating another gap in the field.  相似文献   
53.
IntroductionMuch controversy exists over whether to perform lateral neck dissection (LND) on patients with papillary thyroid carcinoma (PTC). This study aimed to build predictive nomograms that could individually estimate lateral neck metastasis (LNM) risk and help determine follow up intensity.Patients and methodsUnifocal PTC patients who underwent LND between April 2012 and August 2014 were identified. Clinical and pathological variables were retrospectively evaluated using univariate and stepwise multivariate logistic regression analysis. Variables that had statistical significance in final multivariate logistic models were chosen to build nomograms, which were further corrected using the bootstrap resampling method.ResultsIn all, 505 PTC patients were eligible for analysis. Among these, 178 patients (35.2%) had lateral neck metastasis. Two nomograms were generated: nomogram (c) and nomogram (c + p). Nomogram (c) incorporated four clinical variables: age, tumor size, tumor site, and extrathyroidal extension (ETE). It had a good discriminative ability, with a C-index of 0.79 (bootstrap-corrected, 0.78). Nomogram (c + p) incorporated two clinical variables and two pathological variables: tumor size, tumor site, extranodal extension (ENE), and number of positive nodes in the central compartment. Nomogram (c + p) showed an excellent discriminative ability, with a C-index of 0.86 (bootstrap-corrected, 0.85).ConclusionTwo predictive nomograms were generated. Nomogram (c) is a clinical model, whereas nomogram (c + p) is a clinicopathological model. Each nomogram incorporates only four variables and can give an accurate estimate of LNM risk in unifocal PTC patients, which may assist clinicians in patient counseling and decision making regarding LND.  相似文献   
54.
IntroductionLymph node yield (LNY) in neck dissection has been identified as a prognostic factor in oral cavity cancer. The purpose of this study was to investigate the impact of additional use of optical imaging on LNY in therapeutic ND in oral cancer.MethodsConsecutive patients with oral squamous cell carcinoma with clinical neck metastasis planned for primary tumor resection were randomized to conventional neck dissection or near-infrared fluorescence (NIRF)-guided neck dissection, respectively. In the intervention group, patients were injected with ICG-Nanocoll prior to surgery. Intraoperatively, an optical hand-held camera system was used for lymph node identification. Also, NIRF imaging of the neck specimen was performed, and optical signals were pinned with needle markings to guide the pathological examination. The endpoint of the study was LNY per neck side in levels Ib-III.Results31 patients were included with 18 neck sides in the control group and 18 neck sides in the intervention group for evaluation. During NIRF-guided ND, individual lymph nodes could be identified by a bright fluorescent signal and individual tumor-related drainage patterns could be observed in the neck. The LNY in the intervention group was significantly higher compared to the control group (p = 0.032) with a mean of 24 LN (range: 12–33 LN in levels Ib-III compared to 18 LN (range: 10–36 LN) in the control group, respectively.ConclusionsNIRF-guided ND significantly improved the nodal yield compared to the control group. Intraoperative real-time optical imaging enabled direct visualization of tumor-related drainage patterns within the neck lymphatics.  相似文献   
55.
目的 探讨中性粒细胞与淋巴细胞比值(neutrophil to lymphocyte ratio,NLR)对三阴性乳腺癌的临床预后影响及与Ki - 67表达的关系。方法 回顾性分析2006年1月 - 2012年12月于我院乳腺外科住院治疗的134例三阴性乳腺癌患者。NLR最佳临床分界值采用ROC曲线确定,并依此分NLR<2.64组和NLR≥2.64组。临床独立预后因素采用单因素和多因素Cox回归模型分析。术后生存时间和生存曲线比较采用Kaplan - Meier和log - rank方法。Ki - 67的表达采用免疫组织化学方法检测。结果 NLR是三阴性乳腺癌的独立预后因素,最佳临界值为2.64。NLR<2.64组术后中位DFS为39.10月,中位OS为52.30月;NLR≥2.64组术后中位DFS为27.35月,中位OS为37.35月。2组术后DFS和OS比较,差异具有统计学意义(P<0.05)。NLR低组伴Ki - 67表达阴性的三阴性患者术后中位DFS和OS生存时间显著高于其他情况。结论 NLR是三阴性乳腺癌的关键影响预后因素,具有重复性强、非侵袭性、方便实用等特性,可用于预测三阴性乳腺癌临床预后。  相似文献   
56.
Lingual lymph nodes are an inconstant group of in-transit nodes, which are located on the route of lymph drainage from the tongue mucosa to the regional nodes in neck levels I and II. There is growing academic data on the metastatic spread of oral cancer, particularly regarding the spreading of oral tongue squamous cell carcinoma to lingual nodes. These nodes are not currently included in diagnostic and treatment protocols for oral tongue cancer. Combined information on surgical anatomy, clinical observations, means of detection, and prognostic value is presented. Anatomically obtained incidence of lingual nodes ranges from 8.6% to 30.2%. Incidence of lingual lymph node metastasis ranges from 1.3% to 17.1%. It is clear that lymph nodes that bear intervening tissues from the floor of the mouth should be removed to improve loco-regional control. Extended resection volume, which is required for the surgical treatment of lingual node metastasis, cannot be implied to every tongue cancer patient. As these lesions significantly influence prognosis, special efforts of their detection must be made. Reasonably, every tongue cancer patient must be investigated for the existence of lingual lymph node metastasis. Lymphographic tracing methods, which are currently implied for sentinel lymph node biopsies, may improve the detection of lingual lymph nodes.  相似文献   
57.
58.
背景与目的:甲状腺乳头状癌(papillary thyroid carcinoma,PTC)和桥本甲状腺炎(Hashimoto’s thyroiditis,HT)的发病率均呈上升趋势,两者之间的关系已成为目前研究的热点。探讨PTC和HT之间的关系。方法:回顾性分析2014—2015年期间在中国科学院大学附属肿瘤医院头颈肿瘤外科行甲状腺癌手术治疗的首诊患者306例,术后病理学检查均明确诊断为PTC,其中术后病理学确诊伴发HT者42例,比较伴发HT与未伴发HT患者的临床病理学特征。结果:PTC患者女性发病年龄高于男性(46.2岁 vs 41.9岁)。相较于与未伴发HT的PTC患者,伴发HT的患者中女性比例更高(93% vs77%),中央区淋巴结数目较多[(5.0±3.4)枚 vs (2.5±2.7)枚],术前促甲状腺激素(thyroid-stimulating hormone,TSH)水平较高[(3.28±1.91)μU/mL vs (2.12±1.29)μU/mL],术前抗甲状腺过氧化物酶抗体(thyroid peroxidaseantibody,TPOAb)阳性率较高(55% vs 14%),术前甲状腺球蛋白抗体(thyroglobulin antibodies,TgAb)阳性率较高(69% vs 13%)。发生中央区淋巴结转移的患者中,中央区淋巴结转移数目与中央区淋巴结总数显著相关(Pearson相关系数=0.582)。多因素logistic回归分析发现,男性、低龄、被膜侵犯是PTC患者中央区淋巴结转移的独立危险因素。结论:伴发HT对PTC患者的预后无显著影响。伴发HT的PTC患者TSH水平显著偏高,提示HT可能是PTC发病风险因素之一。中央区淋巴结转移数目与中央区淋巴结总数相关,推测PTC淋巴结转移可能与淋巴结炎症反应相关。  相似文献   
59.
60.
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