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   6810篇
  免费   452篇
  国内免费   129篇
耳鼻咽喉   59篇
儿科学   245篇
妇产科学   322篇
基础医学   843篇
口腔科学   195篇
临床医学   897篇
内科学   1356篇
皮肤病学   185篇
神经病学   392篇
特种医学   224篇
外科学   885篇
综合类   236篇
一般理论   2篇
预防医学   298篇
眼科学   201篇
药学   569篇
中国医学   91篇
肿瘤学   391篇
  2023年   50篇
  2022年   68篇
  2021年   156篇
  2020年   90篇
  2019年   149篇
  2018年   189篇
  2017年   127篇
  2016年   139篇
  2015年   199篇
  2014年   227篇
  2013年   328篇
  2012年   484篇
  2011年   446篇
  2010年   263篇
  2009年   240篇
  2008年   366篇
  2007年   379篇
  2006年   335篇
  2005年   304篇
  2004年   268篇
  2003年   232篇
  2002年   193篇
  2001年   188篇
  2000年   214篇
  1999年   139篇
  1998年   70篇
  1997年   101篇
  1996年   69篇
  1995年   59篇
  1994年   59篇
  1993年   46篇
  1992年   129篇
  1991年   91篇
  1990年   104篇
  1989年   97篇
  1988年   86篇
  1987年   65篇
  1986年   56篇
  1985年   57篇
  1984年   41篇
  1983年   30篇
  1982年   31篇
  1981年   23篇
  1979年   24篇
  1978年   21篇
  1977年   22篇
  1976年   20篇
  1971年   18篇
  1970年   18篇
  1966年   17篇
排序方式: 共有7391条查询结果,搜索用时 15 毫秒
11.
Immunomodulators from Paris formosana Hayata.   总被引:1,自引:0,他引:1  
Eight glycosides PF-1 to PF-8 were isolated from the leaves and stems of Paris formosana Hayata (Liliaceae), of which PF-3 (III) was the main compound. It was found that PF-1 to PF-3 (I-III) caused proliferative responses of mouse lymphocytes to concanavalin A and augmentation of mouse granulocyte/macrophage colony forming cells in mouse fibroblast cell L929 conditioned medium. PF-4(IV) and PF-8 showed significant immunomodulatory effects with very low toxicity: they not only caused the same immune responses as PF-1, 2 & 3 but also enhanced the proliferative response of human peripheral whole blood to phytohemagglutinin. PF-5 (V) also increased 3H-thymidine incorporation in ConA-stimulated lymphocytes and in PHA-stimulated human peripheral whole blood, and enhanced the proliferative response of granulocyte/macrophage colony stimulating activity. PF-6(VI) and PF-7(VII) augmented 3H-thymidine incorporation in granulocyte/macrophage colony-forming cells and mitogenic response of PHA-stimulated human peripheral whole blood cells from healthy adults. However, PF-1, 2 and 3 showed hemolytic action, while PF-4 to PF-8 had no hemolytic action at all. On the other hand, the hemolytic action of PF-3 derivatives was reduced as compared with PF-3 but their immune responses did not equal those of PF-3, only showing granulocyte/macrophage colony stimulating activity.  相似文献   
12.
BACKGROUND AND PURPOSE: Odontoma is the most common odontogenic tumor. It includes 2 types, the compound and complex odontomas. There has not been a series study of the clinical and histologic features of odontomas from Taiwan. This study evaluated the clinicopathologic features of odontoma in Taiwanese. METHODS: Cases of odontoma treated from 1998 to 2002 identified from medical records were included. The microscopic features, radiographic features, and clinical history of the patients were reviewed and analyzed. RESULTS: A total of 81 odontomas in 81 patients (36 males and 45 females) were included. There were 62 compound and 19 complex odontomas. The mean age of the patients was 18 years with the majority of odontomas occurring in the first (32%) and second decade (38%) of life. Odontomas had a marked predilection for the maxilla (70%) and for the anterior region of the jaw (83%), particularly for the anterior maxilla (62%). Sixty four (79%) of the 81 odontomas were associated with 80 impacted teeth, including 71 permanent teeth, 2 deciduous teeth, and 7 supernumerary teeth. Of the 71 impacted permanent teeth, the maxillary central incisor (27%) was most commonly affected, followed by the maxillary canine (26%) and mandibular canine (24%). Histologic examination revealed enamel matrix in 90%, dentin in 100%, cementum in 88%, pulp tissue in 96%, fibrous capsule in 93%, ghost cells in 83%, reduced enamel epithelium in 86%, and nests of odontogenic epithelium in 58% of odontomas. Dentigerous cyst was associated with 9% of odontomas. CONCLUSIONS: In this series, odontomas occurred most often in the first and second decade of life. Although complex odontomas are usually found in the posterior jaw, in this Taiwanese series they were most commonly found in the anterior maxilla. Odontoma is frequently associated with an impacted tooth and occasionally with a dentigerous cyst. No recurrence of odontomas was found after surgical excision with follow-up of 1 to 15 years.  相似文献   
13.
Physalins B and F were isolated and characterized from the ethanolic extract of the whole plant of Physalis angulata L. (Solanaceae). Both physalin B and physalin F inhibited the growth of several human leukemia cells: K562 (erythroleukemia), APM1840 (acute T lymphoid leukemia), HL-60 (acute promyelocytic leukemia), KG-1 (acute myeloid leukemia), CTV1 (acute monocytic leukemia) and B cell (acute B lymphoid leukemia). Physalin F showed a stronger activity against these leukemia cells than physalin B, especially against acute myeloid leukemia (KG-1) and acute B lymphoid leukemia (B cell). From the structural features, the active site seems to be the functional epoxy group for physalin F and the double bond for physalin B located at carbon 5 and 6; the former is much more active than the latter as regards anti-leukemic effects.  相似文献   
14.
For many years, parts of the large or small bowel have been used for bladder augmentation and substitution. Recent controversy over the advantages and disadvantages of continent urinary diversion using detubularized ileum (the Kock pouch) and tubular ileum (the Camey procedure) focussed on how a highly compliant urinary reservoir should be formed. We compared the compliance of isolated intact ileal segments and ileal pouches constructed after transection of the antimesenteric border. Hydrodynamic data was obtained at four different points in time: acute (immediately after pouch construction), and after two, six and twelve weeks. Over the first six weeks the reservoirs were connected to the bladder for drainage. At six weeks, subtotal cystectomy and separate anastomosis of the tubular ileal loop and the detubularized ileal pouch to the trigone was performed to study the influence of cyclic reservoir distention. Statistical analysis of the pressure-volume curves revealed significantly better compliance of the detubularized ileal pouch as compared to the intact ileal segments. The area under the pressure curve values (AUC) were p less than 0.025, p less than 0.02, p less than 0.005 and p less than 0.02 for the acute experiment, after two weeks, after six weeks, and after 12 weeks respectively. Our findings suggest that transection of the circular intestinal wall is an important step in the creation of a good-compliant urinary reservoir.  相似文献   
15.
The aim of this study was to investigate the pathological and cellular basis for radiation-induced myelopathy in guinea pigs by monitoring biochemical alterations in levels of myelin basic protein and 2',3'-cyclic nucleotide phosphohydrolase. Guinea pigs were irradiated to the lumbar region with various doses of neutrons or cobalt gamma irradiation. The ED50s for paralysis were 17.2 Gy and 67.5 Gy for neutron and cobalt irradiation, respectively, and was histologically associated with demyelination. In spinal cords taken from animals at the onset of paralysis myelin basic protein levels were decreased in direct relationship to the radiation dose. The lowest doses to cause paralysis led to a 25% decrease in MBP levels. In a separate experiment, alterations in MBP were measured in the spinal cords over the time period leading up to paralysis. Surprisingly, decreases in MBP were found immediately after the end of the 4 week irradiation period. These early changes in MBP were not markedly dose dependent and occurred with nonparalyzing doses. Dose-dependent decreases were found only just before the onset of paralysis. CNPase activity measured in the same specimens showed changes that were essentially similar to those for MBP. In the CSF, MBP levels were essentially constant until onset of paralysis. This study showed that demyelination, as assessed by the levels of the myelin-associated proteins MBP and CNPase, can occur soon after spinal cord irradiation but that profound dose-dependent changes are seen only immediately preceding the onset of paralysis. Although increases in MBP in the CSF were associated with the onset of radiation-induced myelopathy, its assay is unlikely to predict this complication of irradiation.  相似文献   
16.
Severe aortic regurgitation was discovered in a young man 21 days after blunt chest trauma and after a prolonged febrile state with positive blood cultures. Using transoesophageal echocardiography (TEE), it was possible to make the differential diagnosis between traumatic rupture and endocarditis as the cause of valvular insufficiency. The use of TEE in the initial evaluation of severe thoracic trauma with an unclear clinical picture is recommended. This method is easy to use at the bedside and gives precise information on the aortic valve and the ascending aorta.  相似文献   
17.
BACKGROUND AND PURPOSE: Mycoplasma pneumoniae infection is a frequent cause of community-acquired respiratory infections in children and adults. However, standardized, rapid, specific methods for its diagnosis are lacking. The relationship between M. pneumoniae infection and asthma exacerbation has been recently discussed in the literature. We investigated the accuracy of rapid detection of mycoplasma infection by cold hemagglutination test compared to conventional enzyme immunoassays. The clinical characteristics of mycoplasma infection seen during emergent visits in asthmatic children were reviewed. METHODS: We retrospectively reviewed medical records of patients with asthma exacerbation visiting the Department of Pediatric Emergency, National Taiwan University Hospital, over a 12-month period. Subjects 2-18 years of age diagnosed with asthma at our outpatient clinic were included in this study. Patients with immunodeficiency, congenital anomalies, neurological diseases and irregular follow-up were excluded. RESULTS: A total of 269 children (174 males and 95 females) with a mean (+/- standard deviation) age of 6.15 +/- 3.08 years were included. The prevalence of asthma exacerbation in regular follow-up patients was 13.4%, and as many as 19.6% of cases (74/378 person-times) required hospitalization. Asthma attacks were most prevalent during December. 126 patients had both rapid cold hemagglutination testing and mycoplasma immunoglobulin M titers determined using acute blood samples drawn in the emergency room; 46 (36.5%) of these patients demonstrated mycoplasma infection. Sensitivity and specificity of the rapid cold hemagglutination test was 78.3% and 41.3%, respectively. The positive predictive value was 43.4%. Comparison of patients with or without mycoplasma infection revealed no differences in gender, age, chest X-ray findings, and most symptoms/signs and laboratory data, except that more signs of fever and auscultatory rales were seen in the non-mycoplasma infection group. CONCLUSIONS: Mycoplasma infections could be an exacerbating factor for asthma, and the rapid cold hemagglutination test should not be a guideline for prescribing macrolides in the emergency room.  相似文献   
18.
We have investigated the use of a cationic lipid preparation to enhance antisense oligonucleotide activity in human umbilical vein endothelial cells. A liposomal preparation containing the cationic lipid N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) was found to increase by at least 1000-fold the potency of an antisense oligonucleotide (ISIS 1570) that hybridizes to the AUG translation initiation codon of human intercellular adhesion molecule-1. In the presence of 8 microM DOTMA, 6-15-fold more 35S-ISIS 1570 associated with cells, at oligonucleotide concentrations from 0.01 to 5 microM, than did in the absence of DOTMA. Both 35S-ISIS 1570 association with cells and antisense activity were increased as a function of DOTMA concentration and with increasing time of incubation with the cationic lipid. Fluorescein-labeled ISIS 1570 was used to assess the intracellular distribution of the oligonucleotide in the presence and absence of DOTMA. In the absence of DOTMA, the oligonucleotide localized to discrete structures in the cytoplasm of the cell, resulting in a punctate fluorescence pattern. In the presence of DOTMA, cellular fluorescence markedly increased and the oligonucleotide localized within the nucleus, as well as to discrete structures in the cytoplasm. Accumulation of the oligonucleotide in the nucleus in the presence of DOTMA was time and temperature dependent. Nuclear accumulation was inhibited by preincubation of the cells with monensin but not chloroquine, NH4Cl, nocodazole, colcemid, or brefeldin A. These data demonstrate that cationic lipids increase antisense activity by increasing the amount of oligonucleotide associated with cells and altering intracellular distribution of the oligonucleotide.  相似文献   
19.
Clinical and histological patterns of dermatofibromas of the nail apparatus   总被引:1,自引:0,他引:1  
True fibromas develop as painless slow-growing nodular tumours. They may appear in any portion of the nail apparatus. The clinical features vary according to their anatomical site. In contrast, the histological features, consisting of a dermal hypocellular reticular nodule with ill-defined demarcation, were similar in all our patients, and factor XIIIa was negative.  相似文献   
20.
OBJECTIVES: To examine patient satisfaction with and recommendation of a hospital, with a special focus on the correlation of these measures to patient ratings of interpersonal and technical performance of the hospital. DESIGN: Telephone survey of patients with four specific conditions after their discharge from hospitals. SETTING: Accredited district teaching hospitals and above, nationwide in Taiwan. PARTICIPANTS: A total of 4945 patients from 126 hospitals diagnosed with or undergoing procedures related to stroke, diabetes mellitus, Caesarean section, or appendectomy were interviewed by telephone. MAIN OUTCOME MEASURES: Overall patient satisfaction and recommendation were measured by single-item questions. Interpersonal skills were measured by three items: doctors' explanation, attitude, and caring. Technical skills were measured by another three items: hospital equipment, clinical competence, and outcome of treatment. RESULTS: Interpersonal skills were as influential or more influential than clinical competence on patient satisfaction for three of the four disease categories. In contrast, technical competence was a more influential predictor for recommendation for patients in all four disease categories. CONCLUSION: The preliminary results imply that a hospital with high percentage of patient satisfaction does not necessarily receive a high level of recommendation. This finding provides new insights for researchers and for hospital managers who devote resources exclusively for achieving the highest possible levels of patient satisfaction.  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