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   2405682篇
  免费   179679篇
  国内免费   4076篇
耳鼻咽喉   32870篇
儿科学   77853篇
妇产科学   64778篇
基础医学   354960篇
口腔科学   65434篇
临床医学   216187篇
内科学   468943篇
皮肤病学   53309篇
神经病学   190921篇
特种医学   90701篇
外国民族医学   506篇
外科学   363582篇
综合类   48801篇
现状与发展   12篇
一般理论   885篇
预防医学   185299篇
眼科学   55391篇
药学   180366篇
  11篇
中国医学   4859篇
肿瘤学   133769篇
  2021年   18598篇
  2019年   21108篇
  2018年   28964篇
  2017年   21823篇
  2016年   24380篇
  2015年   27511篇
  2014年   38580篇
  2013年   57344篇
  2012年   79367篇
  2011年   84269篇
  2010年   50103篇
  2009年   47258篇
  2008年   78682篇
  2007年   83733篇
  2006年   84253篇
  2005年   81548篇
  2004年   78359篇
  2003年   75368篇
  2002年   72832篇
  2001年   110528篇
  2000年   112950篇
  1999年   94350篇
  1998年   26067篇
  1997年   22527篇
  1996年   22844篇
  1995年   23092篇
  1994年   21230篇
  1993年   20018篇
  1992年   72818篇
  1991年   71017篇
  1990年   69132篇
  1989年   66437篇
  1988年   60940篇
  1987年   59748篇
  1986年   55852篇
  1985年   53572篇
  1984年   39696篇
  1983年   33729篇
  1982年   20057篇
  1979年   36134篇
  1978年   25826篇
  1977年   21349篇
  1976年   20482篇
  1975年   22048篇
  1974年   26415篇
  1973年   25063篇
  1972年   23460篇
  1971年   22274篇
  1970年   20449篇
  1969年   19521篇
排序方式: 共有10000条查询结果,搜索用时 47 毫秒
1.
2.
3.
The International Journal of Cardiovascular Imaging - Global longitudinal strain (GLS) has proven to be a powerful prognostic marker in various patient populations, but the prognostic value of...  相似文献   
4.
In the last decade, the development of new radiopharmaceuticals for the imaging and therapy of prostate cancer has been a highly active and important area of research, especially focusing on the prostate-specific membrane antigen (PSMA), an antigen which is upregulated in prostate, as well as in other tumor cells. A large variety of PSMA ligands have been radiolabeled, to date. Among the various derivatives, PSMA-617 resulted to be one of the most interesting in terms of interaction with the antigen and clinical properties, and its lutetium-177 labeled version has recently been approved by regulatory agencies for therapeutic purposes. For this reasons, the radiolabeling with fluorine-18 of a PSMA-617 derivative might be of interest. Beside other methodologies to radiolabel macromolecules with fluorine-18, the “click-chemistry” approach resulted to be very useful, and the copper-catalyzed azide-alkyne cycloaddition (CuAAC) is considered one of most efficient and reliable. This paper proposes the synthesis of a suitable precursor for the radiolabeling with fluorine-18 of a new PSMA-617 derivative. The whole radiosynthetic procedure has been fully automated, and the final product, which proved to be stable in plasma, has been obtained with radiochemical yield and purity suitable for subsequent preclinical studies.  相似文献   
5.
6.
Previous studies on the immunogenicity of SARS-CoV-2 mRNA vaccines showed a reduced seroconversion in cancer patients. The aim of our study is to evaluate the immunogenicity of two doses of mRNA vaccines in solid cancer patients with or without a previous exposure to the virus. This is a single-institution, prospective, nonrandomized study. Patients in active treatment and a control cohort of healthy people received two doses of BNT162b2 (Comirnaty, BioNTech/Pfizer, The United States) or mRNA-1273 (Spikevax, Moderna). Vaccine was administered before starting anticancer therapy or on the first day of the treatment cycle. SARS-CoV-2 antibody levels against S1, RBD (to evaluate vaccine response) and N proteins (to evaluate previous infection) were measured in plasma before the first dose and 30 days after the second one. From January to June 2021, 195 consecutive cancer patients and 20 healthy controls were enrolled. Thirty-one cancer patients had a previous exposure to SARS-CoV-2. Cancer patients previously exposed to the virus had significantly higher median levels of anti-S1 and anti-RBD IgG, compared to healthy controls (P = .0349) and to cancer patients without a previous infection (P < .001). Vaccine type (anti-S1: P < .0001; anti-RBD: P = .0045), comorbidities (anti-S1: P = .0274; anti-RBD: P = .0048) and the use of G-CSF (anti-S1: P = .0151) negatively affected the antibody response. Conversely, previous exposure to SARS-CoV-2 significantly enhanced the response to vaccination (anti-S1: P < .0001; anti-RBD: P = .0026). Vaccine immunogenicity in cancer patients with a previous exposure to SARS-CoV-2 seems comparable to that of healthy subjects. On the other hand, clinical variables of immune frailty negatively affect humoral immune response to vaccination.  相似文献   
7.
8.
The Earth’s mean surface temperature is already approximately 1.1°C higher than pre-industrial levels. Exceeding a mean 1.5°C rise by 2050 will make global adaptation to the consequences of climate change less possible. To protect public health, anaesthesia providers need to reduce the contribution their practice makes to global warming. We convened a Working Group of 45 anaesthesia providers with a recognised interest in sustainability, and used a three-stage modified Delphi consensus process to agree on principles of environmentally sustainable anaesthesia that are achievable worldwide. The Working Group agreed on the following three important underlying statements: patient safety should not be compromised by sustainable anaesthetic practices; high-, middle- and low-income countries should support each other appropriately in delivering sustainable healthcare (including anaesthesia); and healthcare systems should be mandated to reduce their contribution to global warming. We set out seven fundamental principles to guide anaesthesia providers in the move to environmentally sustainable practice, including: choice of medications and equipment; minimising waste and overuse of resources; and addressing environmental sustainability in anaesthetists’ education, research, quality improvement and local healthcare leadership activities. These changes are achievable with minimal material resource and financial investment, and should undergo re-evaluation and updates as better evidence is published. This paper discusses each principle individually, and directs readers towards further important references.  相似文献   
9.
Objective: Hepatocellular carcinoma (HCC) microenvironment has been recognized as a key contributor for cancer progression, metastasis, and drug resistance. The crosstalk between tumor cells, the vascular endothelial growth factor (VEGF), and the chemokine (C-C motif) ligand 2 (CCL2) signaling networks mediates immunoinhibitory impact and facilitates tumor angiogenesis. The current investigation aimed at exploring the potent anti-cancer activity of the newly designed nano-based anti-cancer therapy comprising anti-VEGF drug, avastin (AV), and CCR2 antagonist (CR) to counteract HCC and tracking its mode of action in vivo. Methods: The prepared AV, CR, and AVCR nanoprototypes were characterized by nanoscale characterization techniques in our previous work. Here, they are applied for unearthing their anti-cancer properties / mechanisms in hepatic cancer-induced rats via analyzing protein levels and genetic expression of the elements incorporated in the angiogenesis, apoptosis, and metastasis signalling pathways. Results: The present results revealed a significant down-regulation in the angiogenesis, survival and metastasis indices along with up-regulation in the pro-apoptotic mediators upon treatment of hepatic cancer-bearing rats with the novel synthesized nanomaterials when compared with the untreated counterparts. We showed across HCC model that anti-VEGF in combination with CCR2 antagonism therapy leads to sensitization and enhanced tumor response over anti-VEGF or CCR2 antagonism monotherapy, particularly in its nanoscale formulation. Conclusion: The present approach provides new mechanistic insights into the powerful anti-hepatic cancer advantage of the novel nanoprototypes which is correlated with modulating critical signal transduction pathways implicated in tumor microenviroment such as angiogenesis, apoptosis and metastasis. This research work presents a substantial foundation for future studies focused on prohibiting cancer progression and recovery by targeting tumor microenviroment.  相似文献   
10.
Bulletin of Experimental Biology and Medicine - We studied the effect of microalgae of various systematic groups added to the ration on the biochemical parameters of blood serum and liver and...  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