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   1506篇
  免费   86篇
  国内免费   13篇
耳鼻咽喉   28篇
儿科学   52篇
妇产科学   42篇
基础医学   283篇
口腔科学   25篇
临床医学   88篇
内科学   389篇
皮肤病学   23篇
神经病学   175篇
特种医学   14篇
外科学   107篇
综合类   7篇
预防医学   131篇
眼科学   21篇
药学   141篇
中国医学   1篇
肿瘤学   78篇
  2024年   2篇
  2023年   13篇
  2022年   89篇
  2021年   111篇
  2020年   28篇
  2019年   39篇
  2018年   45篇
  2017年   34篇
  2016年   39篇
  2015年   34篇
  2014年   47篇
  2013年   74篇
  2012年   105篇
  2011年   122篇
  2010年   66篇
  2009年   54篇
  2008年   75篇
  2007年   81篇
  2006年   100篇
  2005年   72篇
  2004年   75篇
  2003年   71篇
  2002年   57篇
  2001年   16篇
  2000年   24篇
  1999年   19篇
  1998年   5篇
  1997年   9篇
  1996年   3篇
  1995年   6篇
  1994年   5篇
  1993年   5篇
  1992年   2篇
  1991年   2篇
  1990年   6篇
  1989年   6篇
  1988年   8篇
  1987年   7篇
  1986年   5篇
  1985年   8篇
  1984年   5篇
  1982年   2篇
  1981年   2篇
  1980年   3篇
  1977年   3篇
  1976年   3篇
  1973年   2篇
  1972年   5篇
  1970年   2篇
  1969年   2篇
排序方式: 共有1605条查询结果,搜索用时 15 毫秒
1.
OBJECTIVE: To compare perceived quality of life (QoL) in patients diagnosed with seasonal affective disorder (SAD) during the winter and summer months. METHODS: Twenty-six patients who were enrolled in an ongoing multicentre study in Canada completed 2 measures of QoL (the 20-item Medical Outcomes Study Short-Form General Health Survey [SF-20] and the Quality of Life Enjoyment and Satisfaction Questionnaire, [Q-LES-Q]) during the winter, when suffering from depression, and again during the summer months. RESULTS: Both general and health-related QoL scores were significantly improved in patients with SAD during the summer months, with scores for the most part falling within normal range. CONCLUSIONS: Perceived QoL in patients with SAD is markedly impaired during the winter months but shows a substantial rebound during the summer months. The findings of this study provide further evidence that SAD is a distinct diagnostic entity.  相似文献   
2.
3.
Extracellular calreticulin (CRT) as well as anti‐CRT antibodies have been reported in patients with various autoimmune disorders and CRT has been implicated in ‘epitope spreading’ to other autoantigens such as the Ro/SS‐A complex. In addition, antibodies against parasite forms of the endoplasmic reticulum chaperone, CRT, have been found in patients suffering from onchocerciasis and schistosomiasis. In this study, we screened sera for anti‐CRT antibodies from patients with active and inactive systemic lupus ertythematosus (SLE) and primary or secondary Sjögren’s syndrome. Approximately 40% of all SLE patients were positive for anti‐CRT antibodies. The antigenic regions of CRT were determined using full length CRT and fragments of CRT prepared in yeast and Escherichia coli, respectively. Synthetic 15mer peptides corresponding to the major autoantigenic region of CRT (amino acids 1–289), each one overlapping by 12 amino acids, were used to map the B cell epitopes on the CRT protein recognized by autoimmune sera. Major antigenic epitopes were found to be associated with the N‐terminal half of the protein in 69% of the SLE sera from active disease patients, while the C‐domain was not antigenic. Major epitopes were found to be reactive with antibodies in sera from SLE patients with both active and inactive disease, spanning different regions of the N and P‐domains. Sera from both healthy and disease controls and primary Sjögren’s syndrome patients were non‐reactive to these sequences. Limited proteolysis of CRT with two major leucocyte serine proteases, elastase and cathepsin G, demonstrated that an N‐terminal region of CRT is resistant to digestion. Interestingly, some of the epitopes with the highest reactivity belong to the fragments of the protein which bind to C1q and inhibit complement activation. Whether C1q association with CRT is a pathological or protective interaction between these two proteins is currently under investigation.  相似文献   
4.
5.
Premalignant cervical lesions occur at the squamo-columnar junction and in endocervical epithelium and squamous ectocervical epithelium, in descending order of frequency. However, previously only ectocervical cells have been clearly shown to be immortalized in vitro by the oncogenic human papillomaviruses (HPVs). This report describes the immortalization of normal human ecto- and endocervical epithelial cells by the intact HPV 16 genome. Ectocervical epithelial cells (HEC) became immortalized (HEC-16) without crisis while endocervical cells (HEN) were immortalized (HEN-16) after undergoing crisis. HEN-16 and HEC-16 contained integrated HPV 16 DNA, expressed E6 and E7 mRNA, and were aneuploid and nontumorigenic. They also expressed cytokeratins in a pattern similar to their distinct normal parental cells. These results suggest that both squamous and simple epithelial cells of uterine cervix are targets for immortalization by HPV 16.  相似文献   
6.
BACKGROUND: Chronic inflammation with tissue eosinophilia plays a key role in the pathogenesis of asthma and nasal polyps in patients with aspirin hypersensitivity. OBJECTIVE: To evaluate the expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule I (ICAM-1) and their ligands (the integrins lymphocyte function-associated antigen 1 and very late-activation antigen 4 [VLA-4]) in nasal polyps of patients with aspirin hypersensitivity compared with aspirin-tolerant individuals. METHODS: Immunohistochemical studies were performed using a peroxidase method and monoclonal antibodies on 6-microm-thick cryostat sections cut from frozen polyps collected during elective surgery from 21 aspirin-sensitive and 23 aspirin-tolerant patients. RESULTS: The mean +/- SD values of the semiquantitatively evaluated immunoexpression of ICAM-1, VCAM-1, and VLA-4 were significantly increased in patients with aspirin hypersensitivity compared with aspirin-tolerant patients (1.7 +/- 0.8 vs 0.9 +/- 0.8, P < .003; 1.8 +/- 0.8 vs 0.8 +/- 0.8, P < .001; and 2.2 +/- 0.7 vs 1.3 +/- 0.7, P < .001, respectively), whereas the mean +/- SD values of the expression of lymphocyte function-associated antigen 1 did not differ significantly (2.4 +/- 0.5 vs 2.2 +/- 0.9; P = .57). We found a correlation between the immunoexpression of VCAM-1 and its ligand VLA-4 in all studied tissue samples (r = 0.4; P < .02). CONCLUSIONS: In nasal polyps of aspirin-hypersensitive patients, up-regulation of the adhesion molecules ICAM-1 and VCAM-1 and the integrin VLA-4 may play an important role in the development of chronic eosinophilic inflammation.  相似文献   
7.
Angiogenesis, the formation of new blood vessels, is tightly regulated by growth factors, such as vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). The authors hypothesize that nerve growth factor (NGF), a well known neurotrophin, may play a direct angiogenic role. To test this hypothesis, the authors measured the effects of NGF on the natural vascularization of the quail chorioallantoic membrane (CAM). The angiogenic effect of NGF was compared to that of human recombinant VEGF165 (rhVEGF) and basic FGF (rhbFGF). In comparison to phosphate-buffered saline-treated controls, NGFs from different biological sources (mouse, viper, and cobra) increased the rate of angiogenesis in a dose-dependent fashion from 0.5 to 5 microg. For quantitative morphometry, grayscale images of the blood vessels end points of the CAM arteries were binarized for visualization and skeletonized for quantization by fractal analysis. In mouse NGF-treated embryos the fractal dimension (Df), indicative of arterial vessel length and density, increased to 1.266 +/- 0.021 compared to 1.131 +/- 0.018 (p < .001) for control embryos. This effect was similar to that of 0.5 microg rhVEGF (1.290 +/- 0.021, p < .001) and 1.5 microg rhbFGF (1.264 +/- 0.028, p < .001). The mouse NGF-induced angiogenic effect was blocked by 1 microM K252a (1.149 +/- 0.018, p < .001), an antagonist of the NGF/trkA receptor, but not by 1 microM SU-5416 (1.263 +/- 0.029, p < .001), the VEGF/Flk1 receptor antagonist, indicating a direct, selective angiogenic effect of NGF via quail embryo trkA receptor activation. These results confirm previous observations that NGF has angiogenic activity and suggest that this neurotrophin may also play an important role in the cardiovascular system, besides its well-known effects in the nervous system. The angiogenic properties of NGF may be beneficial in engineering new blood vessels and for developing novel antiangiogenesis therapies for cancer.  相似文献   
8.
INTRODUCTION: The purpose of this study was to determine the effect of repeated infusions of infliximab, a chimeric anti-tumor necrosis factor (anti-TNF)-alpha antibody, on the levels of soluble adhesion molecules and vascular endothelial growth factor (VEGF) in patients with active rheumatoid arthritis (RA). MATERIALS AND METHODS: The treatment design consisted of 9 infusions of infliximab (3 mg/kg) at weeks 0, 2, 6, and every 8 weeks thereafter. All patients had been receiving methotrexate (MTX; 7.5-20 mg/week). Serum levels of soluble intercellular adhesion molecule (sICAM)-1, vascular cell adhesion molecule (sVCAM)-1, E-selectin (sE-selectin), and VEGF were measured by ELISA at weeks 0, 2, 6, 14, and 38 prior to infusion, and at week 62. RESULTS: A remarkable decrease in serum sICAM-1 (p<0.001), sVCAM-1 (p<0.01), sE-selectin (p<0.01) and VEGF (p<0.001) levels was observed in RA patients after the initial dose of infliximab. The second administration of the drug was followed by an even more significant suppression of serum sICAM-1, sVCAM-1, sE-selectin, and VEGF (p<0.001 in all cases). Further infliximab infusions also significantly reduced serum soluble adhesion molecules and VEGF concentrations, although these were less effective. Infliximab treatment induced a significant decrease in the number of monocytes observed until the end of the study. CONCLUSIONS: Our study, besides a rapid suppression of disease activity, showed that serum soluble adhesion molecules and VEGF concentrations are down-regulated following anti-TNF-alpha antibody therapy combined with MTX. Repeated doses of infliximab sustained the reductions in the soluble adhesion molecules and VEGF concentrations, although they were less effective than the first and second infusions of infliximab.  相似文献   
9.
A 51-year-old man, heavy cigarette smoker, a homeless alcoholic, with disseminated lesions in lungs and with ulceration and infiltration of the tongue is presented. Treatment with antibiotics was ineffective. He was admitted to the otolaryngological department because of suspicion of the tongue cancer. The histological examination of the tongue biopsy revealed tuberculous granuloma. In the pulmonological department, on admission the patient was cachectic, with massive oedema and ulceration of the tongue, and enlargement of the cervical lymph nodes. He was fed through the gastric tube. He had severe pain of the tongue demanding treatment with opiates analgesics. Chest x-ray revealed disseminated lesions in lungs. Antituberculous therapy was administered because of suspicion of tuberculosis of the tongue and lungs. During the treatment clinical improvement was observed. Tubercule bacilli were grown in the sputum culture after 6 weeks of observation. After 8 weeks of antituberculous therapy regression of lung lesions and healing of the tongue were observed. The patient continued treatment for 6 months in the Lung Disease Outpatient Clinic.  相似文献   
10.
This paper continues the systematic review on proanthocyanidins and flavan-3-ols in the prevention and treatment of periodontal disease and covers the immunomodulatory effects, and animal- and clinical studies, while the other part discussed the direct antibacterial properties. Inflammation as a major response of the periodontal tissues attacked by pathogenic microbes can significantly exacerbate the condition. However, the bidirectional activity of phytochemicals that simultaneously inhibit bacterial proliferation and proinflammatory signaling can provide a substantial alleviation of both cause and symptoms. The modulatory effects on various aspects of inflammatory and overall immune response are covered, including confirmed and postulated mechanisms of action, structure activity relationships and molecular targets. Further, the clinical relevance of flavan-3-ols and available outcomes from clinical studies is analyzed and discussed. Among the numerous natural sources of flavan-3-ols and proanthocyanidins the most promising are, similarly to antibacterial properties, constituents of various foods, such as fruits of Vaccinium species, tea leaves, grape seeds, and tannin-rich medicinal herbs. Despite a vast amount of in vitro and cell-based evidence of immunomodulatory there are still only a few animal and clinical studies. Most of the reports, regardless of the used model, indicated the efficiency of these phytochemicals from cranberries and other Vaccinium species and tea extracts (green or black). Other sources such as grape seeds and traditional medicinal plants, were seldom. In conclusion, the potential of flavan-3-ols and their derivatives in prevention and alleviation of periodontal disease is remarkable but clinical evidence is urgently needed for issuing credible dietary recommendation and complementary treatments.  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