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   8824篇
  免费   395篇
  国内免费   67篇
耳鼻咽喉   96篇
儿科学   165篇
妇产科学   64篇
基础医学   1060篇
口腔科学   201篇
临床医学   560篇
内科学   2620篇
皮肤病学   123篇
神经病学   520篇
特种医学   322篇
外科学   1492篇
综合类   24篇
一般理论   1篇
预防医学   142篇
眼科学   121篇
药学   480篇
中国医学   12篇
肿瘤学   1283篇
  2024年   18篇
  2023年   79篇
  2022年   191篇
  2021年   299篇
  2020年   149篇
  2019年   197篇
  2018年   224篇
  2017年   188篇
  2016年   239篇
  2015年   226篇
  2014年   290篇
  2013年   359篇
  2012年   647篇
  2011年   702篇
  2010年   423篇
  2009年   333篇
  2008年   564篇
  2007年   587篇
  2006年   583篇
  2005年   547篇
  2004年   523篇
  2003年   505篇
  2002年   496篇
  2001年   71篇
  2000年   74篇
  1999年   78篇
  1998年   101篇
  1997年   74篇
  1996年   41篇
  1995年   58篇
  1994年   48篇
  1993年   45篇
  1992年   35篇
  1991年   49篇
  1990年   25篇
  1989年   26篇
  1988年   24篇
  1987年   9篇
  1986年   20篇
  1985年   16篇
  1984年   18篇
  1983年   10篇
  1982年   16篇
  1981年   10篇
  1980年   8篇
  1979年   12篇
  1978年   6篇
  1977年   14篇
  1976年   5篇
  1969年   4篇
排序方式: 共有9286条查询结果,搜索用时 15 毫秒
991.
Mast cells (MCs) are common components of inflammatory infiltrates and a source of proangiogenic factors. Inflammation is often accompanied by vascular changes. However, little is known about modulation of MC-derived proangiogenic factors during inflammation. In this study, we evaluated the effects of the proinflammatory mediator prostaglandin E2 (PGE2) on MC expression and release of proangiogenic factors. We report that PGE2 dose-dependently induces primary MCs to release the proangiogenic chemokine monocyte chemoattractant protein-1 (MCP-1). This release of MCP-1 is complete by 2 h after PGE2 exposure, reaches levels of MCP-1 at least 15-fold higher than background, and is not accompanied by degranulation or increased MCP-1 gene expression. By immunoelectron microscopy, MCP-1 is detected within MCs at a cytoplasmic location distinct from the secretory granules. Dexamethasone and cyclosporine A inhibit PGE2-induced MCP-1 secretion by approximately 60%. Agonists of PGE2 receptor subtypes revealed that the EP1 and EP3 receptors can independently mediate MCP-1 release from MCs. These observations identify PGE2-induced MCP-1 release from MCs as a pathway underlying inflammation-associated angiogenesis and extend current understanding of the activities of PGE2.  相似文献   
992.
Anti-glucose-6-phosphate isomerase (GPI) antibodies (Abs) solely induce arthritis in mice. High titers of anti-GPI Abs are found in some patients with rheumatoid arthritis (RA), but their pathogenic role remains elusive. The aim of this study was to evaluate the pathogenic role of anti-GPI Abs in cynomolgus monkeys. IgG fractions were separated from sera of anti-GPI Abs-positive RA patients and healthy subjects and directly injected into the metacarpophalangeal joints of 4 cynomolgus monkeys. At day 16, the joints were harvested and examined histologically and immunohistochemically. The expression of C5a receptor (C5aR) molecule in the synovium was quantified by real-time PCR using cDNA from monkey joints. In monkey joints, IgG including anti-GPI Abs resulted in recruitment of granulocytes and mononuclear cells, strong deposition of human IgG on the articular surface, and overexpression of C5aR, but no joint swelling. No infiltrated cells or IgG deposition were observed in monkeys injected with IgGs from healthy subjects. Our results suggest that IgG fraction from RA patients including anti-GPI Abs may play a crucial role in the generation of synovitis in monkeys, although the pathogenesis of anti-GPI Abs in RA patients is still uncertain.  相似文献   
993.
Alpha rhythm is one of the most prominent electromagnetic changes in the brain, and electroencephalography (EEG) alpha reactivity disturbance may sometimes represent an early sign of cerebral dysfunction. Although magnetoencephalography (MEG) has a better spatial resolution than EEG, it has not extensively been used to explore alpha-power change deficits in schizophrenia as a possible neurophysiological marker of the disease. The purpose of this study was to use MEG to identify abnormalities in alpha synchronization induced by eye-closing in schizophrenia patients compared to healthy controls, and to investigate whether alpha reactivity deficits correlate with clinical features of the disorder. MEG data were recorded in 22 schizophrenia patients and 20 age- and gender-matched controls during eyes-open/eyes-closed resting states. Cortical sources of event-related synchronization (ERS) were estimated using multiple source beamformer, and BrainVoyager was used for statistic group analysis. A significant decrease in ERS in the upper alpha band (10–13 Hz) was found in the left posterior temporal region in schizophrenia patients relative to controls, and this activity showed correlation with visual memory scores. This upper alpha ERS deficit may indicate left temporal dysfunction and visual-information processing impairment in schizophrenia, and upon further confirmation it might represent a neurophysiological state marker of the disorder.  相似文献   
994.
995.
We investigated the distribution of T-type Ca(2+) channel mRNAs in the mouse embryonic heart. Cav3.2, but not Cav3.1, was expressed in the E8.5 embryonic heart along with cardiac progenitor markers (Nkx2.5, Tbx5, Isl-1) and contractile proteins (alpha and beta MHC). In the E10.5 heart, the distribution of Cav3.1 mRNA was confirmed in the AV-canal and overlapped with that of MinK or Tbx2. Cav3.2 mRNA was observed not only in the AV-canal but also in the outflow tract, along with MinK and Isl-1, indicating the expression of Cav3.2 in the secondary heart field. Thus, Cav3.2 may contribute to the development of the outflow tract from the secondary heart field in the embryonic heart, whereas Cav3.1 may be involved in the development of the cardiac conduction-system together with Cav3.2.  相似文献   
996.
Gastrointestinal stromal tumors (GISTs) have been reported to occasionally occur in patients with neurofibromatosis type 1 (NF-1), and many cases have had multiple lesions predominantly involving the small intestine. We report herein a case of multiple GISTs associated with NF-1 from whom laparoscopic surgery was beneficial. In a 79-year-old female admitted with anemia and melena, the abdominal computed tomography revealed a tumor arising from the small intestine. Laparoscopic surgery was performed, and another small tumor was revealed during laparoscopic observation. Extracorporeal partial and wedge resection of the small intestine were undertaken. Both lesions were diagnosed as typical GISTs of low risk. Laparoscopic surgery would be useful for examination and a minimally invasive approach to tumors of the small intestine, especially on cases with the possibility of multiple tumors.  相似文献   
997.
The development of a rapid and sensitive system for detecting influenza viruses is a high priority for controlling future epidemics and pandemics. Quantitative real-time PCR is often used for detecting various kinds of viruses; however, it requires more than 2h per run. Detection assays were performed with super high-speed RT-PCR (SHRT-PCR) developed according to a newly designed heating system. The new method uses a high-speed reaction (18s/cycle; 40 cycles in less than 20min) for typing influenza viruses. The detection limit of SHRT-PCR was 1 copy/reaction and 10(-1) plaque-forming unit/reaction for viruses in culture supernatants during 20min. Using SHRT-PCR, 86 strains of influenza viruses isolated by the Tokyo Metropolitan Institute of Public Health were tested; the results showed 100% sensitivity and specificity for each influenza A and B virus, and swine-origin influenza virus. Twenty-seven swabs collected from the pharyngeal mucosa of outpatients were also tested, showing positive signs for influenza virus on an immunochromatographic assay; the results between SHRT-PCR and immunochromatography exhibited 100% agreement for both positive and negative results. The rapid reaction time and high sensitivity of SHRT-PCR makes this technique well suited for monitoring epidemics and pre-pandemic influenza outbreaks.  相似文献   
998.
Tumor protrusion in hepatocellular carcinoma (HCC) is one of the risk signs of tumor rupture. Despite curative tumor treatments, HCC recurrences sometimes occur with rapidly growing humped or ruptured HCC in small sized tumors. The aim of this study was to clarify the characteristics of humped HCC clinically and radiologically associated with tumor progression, liver damage, and treatment. The subjects were 179 consecutive HCC patients who underwent angiographic examination. Dynamic studies, using helical computed tomography and magnetic resonance imaging were assessed, and the HCC area were measured. The tumor-node-metastasis (TNM) stage differed significantly between the humped and non-humped HCC groups. Humped HCC was more frequently observed in the right lobe (29.3% of right-lobe HCCs) than in the left (10.1%; p=0.003). Analysis of recurrent HCC revealed that patients with multiple treatments of >4 sessions had more humped HCC (33.8%) than those with 1-3 sessions (16.7%; p=0.042). Multivariate regression analysis revealed that tumor invasion in the portal vein, rather than large tumor size, was significantly associated with tumor protrusion. HCC recurrence with humped HCC occurs often in patients with multiple treatments. Tumor factors of the TNM classification, especially tumor invasion in the portal vein, might be associated with the mechanisms of tumor protrusion.  相似文献   
999.
The authors investigated psychiatric consultation in two hospitals, one in the United States, the other in Japan. They examined similarities and differences, and drew inferences on possible cross-cultural values and/or temporary cultural conditions. As compared with the Japanese consultation patients, the Americans had more mood disorders, including anxiety and chemical-dependency problems, in respective diagnostic classifications. Patients in the United States also showed more acute as well as more serious chronic conditions. These differences may relate to disorder base-rates in the respective countries. In general, psychosocial problems emerged as ascendant in Japan, as compared with chemical-dependency difficulties among American patients. The results are discussed in terms of current conditions in Japan that affect the mental health professions, together with attempts by Japanese clinicians to protect collective mores by ascribing causation for disorders to the individual, rather than the societal conditions often invoked in the United States.  相似文献   
1000.

Purpose  

The aim of this study is to investigate clinical characteristics and genetic backgrounds of Mendelian susceptibility to mycobacterial diseases (MSMD) in Japan.  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