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   6881篇
  免费   279篇
  国内免费   28篇
耳鼻咽喉   26篇
儿科学   128篇
妇产科学   105篇
基础医学   897篇
口腔科学   182篇
临床医学   400篇
内科学   1834篇
皮肤病学   89篇
神经病学   501篇
特种医学   268篇
外科学   1263篇
综合类   48篇
预防医学   214篇
眼科学   74篇
药学   427篇
中国医学   48篇
肿瘤学   684篇
  2023年   33篇
  2022年   63篇
  2021年   126篇
  2020年   80篇
  2019年   82篇
  2018年   113篇
  2017年   84篇
  2016年   86篇
  2015年   114篇
  2014年   144篇
  2013年   186篇
  2012年   351篇
  2011年   393篇
  2010年   214篇
  2009年   224篇
  2008年   362篇
  2007年   440篇
  2006年   439篇
  2005年   467篇
  2004年   450篇
  2003年   474篇
  2002年   460篇
  2001年   108篇
  2000年   121篇
  1999年   148篇
  1998年   118篇
  1997年   115篇
  1996年   102篇
  1995年   85篇
  1994年   61篇
  1993年   61篇
  1992年   75篇
  1991年   68篇
  1990年   66篇
  1989年   67篇
  1988年   62篇
  1987年   40篇
  1986年   58篇
  1985年   59篇
  1984年   43篇
  1983年   40篇
  1982年   19篇
  1981年   34篇
  1980年   27篇
  1979年   22篇
  1978年   24篇
  1977年   21篇
  1976年   21篇
  1975年   18篇
  1974年   19篇
排序方式: 共有7188条查询结果,搜索用时 21 毫秒
81.
An autopsy case of abnormal Intracranial vascular networks at the base of the brain corresponding to so-called rete mirabile, associated with occlusion of bilateral internal carotid arteries was reported. This patient was a 62 year-old female who died about two months after sudden onset of subarachnoid hemorrhage. At autopsy, abnormal vascular networks termed as rete mirabile were observed to be collateral blood supplies among the cerebral regions with flow of the anterior, middle, and posterior cerebral arteries, caused by long-stading obstruction of bilateral internal carotid arteries at the syphon level. Morphometrical analysis was done by measuring the length of internal elastic membrane of the internal carotid arteries in cross section, and comparing it with those of controlled persons of the same sex and age without any intracranial disorders and hypertensive histories. The result that no significant difference was observed between the former and the latter values suggested that the unusual cerebro-vascular disorder of this case developed not on the base of congenital anomaly including hypoplasia of internal carotid arteries or arteriovenous malformation but as an acquired lesion established for a long time.  相似文献   
82.
Background: We previously reported that the homozygous mutation of Otx2 gene, a mouse cognate of the Drosophila head gap gene orthodenticle , causes failure in the development of the rostral head anterior to rhombomere 3, which may correspond to earlier Otx2 expression in cells destined for the anterior mesoendoderm. At the same time, the Otx2 heterozygous mutation displayed a phenotype characterized as otocephaly, probably related to expression in the anterior neuroectoderm at the subsequent pharyngula stage. Defects were characteristic in the most anterior and posterior regions of Otx2 expression where Otx1 , another mouse cognate of orthodenticle , is not or weakly expressed. They were not found in the region where Otx1 is expressed.
Results: In the present work, Otx1 null mutant mice were generated by gene targeting in embryonic stem cells. No defects were apparent in the regionalization of the early embryonic rostral brain. The newborn brain defects were subtle and most likely related to later Otx1 -unique expression. Otx1 and Otx2 double heterozygous mutant brains, however, exhibited marked defects throughout the fore- and midbrains, where defects were not apparent with a single mutation alone.
Conclusions: Otx1 and Otx2 play synergistic roles in the development of the forebrain and midbrain where both genes are expressed.  相似文献   
83.
BACKGROUND: Atopic dermatitis (AD) is a common skin disease characterized by chronic recurrent eczematous lesions, but its exact etiology and mechanism are unclear. We found that beige rats (DAbg/bg), a mutant model of Chediak-Higashi syndrome, develop skin lesions characterized by pruritus, excoriation, erosion and alopecia. We describe the beige rat and examine its possible usefulness as an AD model. METHODS: Beige rats of 4, 8, 13, 16, 26 and 52 weeks were used. Histological analysis of the skin was performed. Plasma IgE and cytokines were measured. Th1 and Th2 cytokines and RANTES mRNA expression of skin and lymph nodes were evaluated. Passive cutaneous anaphylaxis (PCA) reactions were examined, and maximization tests were conducted. RESULTS: Skin lesions begin to develop with increases in serum IgE levels and the expression of IL-4 mRNA in the lymph node and skin. Histologically, skin lesions are characterized by acanthosis, ulceration and inflammatory cell infiltration in the dermis. Inflammatory cells consist of CD3+, CD4+, ED1+, ED2+ and I-A+ mononuclear cells, eosinophils, degranulated mast cells and neutrophils accompanying interleukin (IL)-4, interferon (IFN)-gamma and RANTES mRNA expressions of the skin. Inflammatory cells are reduced during chronification with decreased expressions of IL-4, IFN-gamma and RANTES mRNA. In addition, the rats show a high sensitivity to PCA reactions and maximization tests. CONCLUSIONS: Our results show that some of the skin lesions of beige rats are morphologically similar to human AD, being characterized by inflammatory cell composition in the acute phase, and increased IgE and RANTES levels. However, the inflammatory process and cytokine expression pattern are different from those in human AD.  相似文献   
84.
CENP-A, a centromere-specific histone H3, is conserved throughout eukaryotes, and formation of CENP-A chromatin defines the active centromere region. Here, we report the isolation of CENP-A chromatin from HeLa interphase nuclei by chromatin immunoprecipitation using anti-CENP-A monoclonal antibody, and systematic identification of its components by mass spectrometric analyses. The isolated chromatin contained CENP-B, CENP-C, CENP-H, CENP-I/hMis 6 and hMis 12 as well as CENP-A, suggesting that the isolated chromatin may represent the centromere complex (CEN-complex). Mass spectrometric analyses of the CEN-complex identified approximately 40 proteins, including the previously reported centromere proteins and the proteins of unknown function. In addition, we unexpectedly identified a series of proteins previously reported to be related to functions other than chromosome segregation, such as uvDDB-1, XAP8, hSNF2H, FACTp180, FACTp80/SSRP1, polycomb group proteins (BMI-1, RING1, RNF2, HPC3 and PHP2), KNL5 and racGAP. We found that uvDDB-1 was actually localized to the centromeric region throughout cell cycle, while BMI-1 was transiently co-localized with the centromeres in interphase. These results give us new insights into the architecture, dynamics and function of centromeric chromatin in interphase nuclei, which might reflect regulation of cell proliferation and differentiation.  相似文献   
85.
86.
Summary In a study of 277 patients with breast carcinomas, the PAP immunoperoxidase method for demonstrating endogenous estrogen was correlated with the sucrose density gradient (SDG) assay and with histologic and clinical features. The results from the PAP method and SDG assay agreed in 59 of 84 patients (82.1%) on whom both methods were performed. Histologically, the PAP method was positive in 7 of 7 patients with non-invasive carcinomas, in 164 of 233 patients (70.4%) with common invasive ductal carcinoma, and in 21 of 22 of those with special histological types of invasive carcinomas not including Paget's disease, medullary or apocrine carcinoma, where only 5 of 14 were positive. Clinically, 15 of 18 patients with positive endogenous estrogen showed a response to endocrine therapy as opposed to 1 of 9 patients with a negative endogenous estrogen. The mean survival was 31.2 and 15.6 months, respectively for patients with positive and negative endogenous estrogen. Remission for longer than 2 years was seen more often in patients with positive endogenous estrogen. These results suggest a clinical utility of the present PAP method which, therefore, deserves a further trial as an alternative to histochemical methods aiming at the estrogen receptors.This work was supported by Grants-in Aid for Scientific Research from the Ministry of Education, Science, and Culture of Japan (No. 56480119).This paper was presented at the 72nd Annual Meeding of International Academy of Pathology (United States-Canadian Division), Atlanta, Georgia, March 1, 1983.  相似文献   
87.
(1) The spread of epidural analgesia following injection of 15ml of 2% mepivacaine was 17.3 ± 0.6, 14.3 ± 0.4, and 13.3 ± 0.7 spinal segments in cervical, thoracic, and lumbar epidural analgesia, respectively. The patients age showed significant correlation with the spread of epidural analgesia in cervical (r = 0.5776, p < 0.001), thoracic (r = 0.3758, p < 0.01), and lumbar area (r = 0.8195, p < 0.001). The spread of cervical epidural analgesia was more caudad than cephalad (p < 0.05), but in lumbar epidural analgesia it was more cephalad than caudad (p < 0.05). There was no difference between the cephalad and caudad spread in thoracic epidural analgesia.(2) The epidural pressure immediately after injection of 15ml of 2% mepivacaine into the lumbar epidural space at a constant pressure (80mmHg) correlated to the patients age (r = –0.5714, p < 0.001) and the spread of analgesia (r = –0.3904, p < 0.05). The lower epidural pressure associated with higher age, the wider spread of analgesia. There was no significant correlation between the residual pressure at 60 seconds and the age or the spread of analgesia.(Hirabayashi Y et al.: Spread of epidural analgesia following a constant pressure injection: an investigation of relationships between locus of injection, epidural pressure and spread of analgesia. J Anesth 1: 44–50, 1987)  相似文献   
88.
The relationships between the epidural pressures following the injection of local anesthetic solution and the spread of epidural analgesia were investigated. In 46 patients, 15ml of 2% mepivacaine was injected into the lumbar epidural space at a constant rate (1ml/sec) using an electropowered syringe pump. Injection pressures and residual pressures were recorded and the spread of analgesia to pinprick was assessed. The changes of the epidural pressures during and following the injection of a volume of local anesthetic solution in old subjects were significantly smaller than those in young subjects (P < 0.05). The spread of analgesia closely correlated with the epidural pressures during and following the injection of local anesthetic solution. The most close correlation was found between the epidural pressure immediately after the completion of injection and the spread of analgesia (r = –0.5659, P < 0.001). In conclusion, the lower the terminal injection pressure and the residual pressures associated with higher age, the wider the spread of epidural analgesia.(Hirabayashi Y, Matsuda I, Inoue S et al.: Epidural pressure and its relation to spread of epidural analgesia. J Anesth 1: 168–172, 1987)  相似文献   
89.
90.
Pharyngeal cancer patients treated with intensity-modulated proton therapy (IMPT) using a model-based approach were retrospectively reviewed, and acute toxicities were analyzed. From June 2016 to March 2019, 15 pharyngeal (7 naso-, 5 oro- and 3 hypo-pharyngeal) cancer patients received IMPT with robust optimization. Simulation plans for IMPT and intensity-modulated X-ray therapy (IMXT) were generated before treatment. We also reviewed 127 pharyngeal cancer patients with IMXT in the same treatment period. In the simulation planning comparison, all of the normal-tissue complication probability values for dysphagia, dysgeusia, tube-feeding dependence and xerostomia were lower for IMPT than for IMXT in the 15 patients. After completing IMPT, 13 patients completed the evaluation, and 12 of these patients had a complete response. The proportions of patients who experienced grade 2 or worse acute toxicities in the IMPT and IMXT cohorts were 21.4 and 56.5% for dysphagia (P < 0.05), 46.7 and 76.3% for dysgeusia (P < 0.05), 73.3 and 62.8% for xerostomia (P = 0.43), 73.3 and 90.6% for mucositis (P = 0.08) and 66.7 and 76.4% for dermatitis (P = 0.42), respectively. Multivariate analysis revealed that IMPT was independently associated with a lower rate of grade 2 or worse dysphagia and dysgeusia. After propensity score matching, 12 pairs of IMPT and IMXT patients were selected. Dysphagia was also statistically lower in IMPT than in IMXT (P < 0.05). IMPT using a model-based approach may have clinical benefits for acute dysphagia.  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