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   121617篇
  免费   10590篇
  国内免费   2852篇
耳鼻咽喉   954篇
儿科学   2732篇
妇产科学   2196篇
基础医学   9333篇
口腔科学   2159篇
临床医学   22105篇
内科学   13541篇
皮肤病学   1016篇
神经病学   11348篇
特种医学   24571篇
外国民族医学   36篇
外科学   8944篇
综合类   17425篇
现状与发展   12篇
一般理论   2篇
预防医学   4259篇
眼科学   2121篇
药学   4103篇
  128篇
中国医学   1504篇
肿瘤学   6570篇
  2024年   224篇
  2023年   1805篇
  2022年   2978篇
  2021年   5120篇
  2020年   5062篇
  2019年   4356篇
  2018年   4248篇
  2017年   4627篇
  2016年   5153篇
  2015年   4823篇
  2014年   8426篇
  2013年   7834篇
  2012年   7223篇
  2011年   7825篇
  2010年   6442篇
  2009年   6513篇
  2008年   6406篇
  2007年   6407篇
  2006年   5798篇
  2005年   5036篇
  2004年   4368篇
  2003年   3553篇
  2002年   2852篇
  2001年   2682篇
  2000年   2141篇
  1999年   1741篇
  1998年   1607篇
  1997年   1534篇
  1996年   1332篇
  1995年   1154篇
  1994年   979篇
  1993年   850篇
  1992年   673篇
  1991年   570篇
  1990年   473篇
  1989年   362篇
  1988年   384篇
  1987年   324篇
  1986年   235篇
  1985年   214篇
  1984年   141篇
  1983年   91篇
  1982年   99篇
  1981年   86篇
  1980年   86篇
  1979年   67篇
  1978年   43篇
  1977年   25篇
  1976年   28篇
  1975年   27篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
91.
高龄妊娠是指孕妇妊娠年龄≥35岁,近年来其发生率不断增高,已经逐步成为目前我国围产医学关注的热点问题。针对高龄妊娠中的生殖遗传问题,需特别关注女性的生育力下降的情况,其自然流产发生率升高,胎儿染色体异常和胎儿结构畸形的发生率增加,这就更加强调了产前筛查和诊断的重要性,以及需要关注常常与高龄妊娠相伴随的男性高龄生育的问题。做好上述问题的咨询和管理是完成高质量高龄妊娠围产保健的关键。  相似文献   
92.
93.
The purpose of the work was to set‐up a simple method to evaluate the contribution of Mn2+ ions in the intra‐ and extracellular tumor compartments in a MEMRI experiment. This task has been tackled by “silencing” the relaxation enhancement arising from Mn2+ ions in the extracellular space. In vitro relaxometric measurements allowed assessment of the sequestering activity of DO2A (1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid) towards Mn2+ ions, as the addition of Ca‐DO2A to a solution of MnCl2 causes a drop of relaxivity upon the formation of the highly stable and low‐relaxivity Mn‐DO2A. It has been proved that the sequestering ability of DO2A towards Mn2+ ions is also fully effective in the presence of serum albumin. Moreover, it has been shown that Mn‐DO2A does not enter cell membranes, nor does the presence of Ca‐DO2A in the extracellular space prompt migration of Mn ions from the intracellular compartment. On this basis the in vivo, instantaneous, drop in SE% (percent signal enhancement) in T1‐weighted images is taken as evidence of the sequestration of extracellular Mn2+ ions upon addition of Ca‐DO2A. By applying the method to B16F10 tumor bearing mice, T1 decrease is readily detected in the tumor region, whereas a negligible change in SE% is observed in kidneys, liver and muscle. The relaxometric MRI results have been validated by ICP‐MS measurements. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
94.
95.
Mesoporous silica nanoparticles (MSNs) can provide a structural foundation for a new generation of nanocarriers with a broad range of functionalities. Multifunctional MSNs can serve as all-in-one diagnostic and therapeutic tools that can be used to simultaneously visualize and treat various diseases, such as cancer. This research study is the first time that two lanthanide-based imaging systems have been combined to incorporate controlled drug release and targeted tracing into a single MSN-based nano-platform for a novel theranostic drug delivery system. Doping lanthanide ions, i.e., europium (Eu) and gadolinium (Gd) ions, into an MSN structure (EuGd-MSNs) imparts fluorescence and magnetism to the nanostructure that can be used to develop magnetic resonance imaging (MRI) and biological fluorescence tools. Current cancer research has revealed that most human cancer cells express a large number of folate receptors on their surface. Grafting folic acid (FA) onto the EuGd-MSN surface (EuGd-FA-MSNs) imparts a targeting function to the MSN because of the specificity of the binding of FA to cell surface receptors. Furthermore, grafting anticancer drugs, such as camptothecin (CPT), onto the surface of these MSNs by forming disulfide bonds (EuGd-SS-CPT-FA-MSNs) enables intracellular controlled drug release. A high concentration of intracellular glutathione cleaves the disulfide bond to release the drug and treat the disease. The results of in vitro and in vivo studies show that the functionalized MSNs can be successfully used as a platform to integrate dual-imaging, targeting, and therapeutic treatment in multifunctional diagnosis drug delivery systems.  相似文献   
96.
97.
98.
Background and purposeAutomated synthetic magnetic resonance imaging (MRI) provides qualitative, weighted image contrasts as well as quantitative information from one scan and is well-suited for various applications such as analysis of white matter disorders. However, the synthesized contrasts have been poorly evaluated in pediatric applications. The purpose of this study was to compare the image quality of synthetic T2 to conventional turbo spin-echo (TSE) T2 in pediatric brain MRI.Materials and methodsThis was a mono-center prospective study. Synthetic and conventional MRI acquisitions at 1.5 Tesla were performed for each patient during the same session using a prototype accelerated T2 mapping sequence package (TAsynthetic = 3:07 min, TAconventional = 2:33 min). Image sets were blindly and randomly analyzed by pediatric neuroradiologists. Global image quality, morphologic legibility of standard structures and artifacts were assessed using a 4-point Likert scale. Inter-observer kappa agreements were calculated. The capability of the synthesized contrasts and conventional TSE T2 to discern normal and pathologic cases was evaluated.ResultsSixty patients were included. The overall diagnostic quality of the synthesized contrasts was non-inferior to conventional imaging scale (P = 0.06). There was no significant difference in the legibility of normal and pathological anatomic structures of synthetized and conventional TSE T2 (all P > 0.05) as well as for artifacts except for phase encoding (P = 0.008). Inter-observer agreement was good to almost perfect (kappa between 0.66 and 1).ConclusionsT2 synthesized contrasts, which also provides quantitative T2 information that could be useful, could be suggested as an equivalent technique in pediatric neuro-imaging, compared to conventional TSE T2.  相似文献   
99.
ObjectiveThe purpose of this study was to evaluate the visibility of the anterolateral ligament (ALL) by magnetic resonance imaging (MRI) in patients with chronic anterior cruciate ligament (ACL) rupture.Materials and methodsThis retrospective case – control study compared 1.5 - T MRI scans for 50 patients with a chronic ACL rupture with those of a control group of 50 patients with an intact ACL. The ALL was evaluated in three portions: femoral, meniscal, and tibial. The status of each portion was classified as visualized or non-visualized. Two radiologists separately reviewed all the MRI scans to evaluate interobserver reliability.ResultsAt least one portion of the ALL was visualized in 100% of the control group and 72% of the chronic ACL rupture group. All three portions of the ALL were identified in 72% of the control group but only 10% of the chronic ACL rupture group. In both groups, the most commonly visualized portion was the meniscal portion and the least visualized was the tibial portion. In 18% of the chronic ACL rupture group, no portion of the ALL was visualized.ConclusionsThe visibility of the ALL of the knee was significantly lower in patients with a chronic ACL rupture than in those with an intact one.  相似文献   
100.
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   
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