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   7741篇
  免费   722篇
  国内免费   62篇
耳鼻咽喉   120篇
儿科学   254篇
妇产科学   202篇
基础医学   1030篇
口腔科学   204篇
临床医学   762篇
内科学   1486篇
皮肤病学   249篇
神经病学   477篇
特种医学   477篇
外科学   774篇
综合类   90篇
一般理论   2篇
预防医学   969篇
眼科学   156篇
药学   562篇
中国医学   13篇
肿瘤学   698篇
  2022年   48篇
  2021年   98篇
  2020年   84篇
  2019年   129篇
  2018年   141篇
  2017年   111篇
  2016年   139篇
  2015年   158篇
  2014年   177篇
  2013年   246篇
  2012年   357篇
  2011年   295篇
  2010年   215篇
  2009年   222篇
  2008年   317篇
  2007年   378篇
  2006年   356篇
  2005年   346篇
  2004年   292篇
  2003年   280篇
  2002年   258篇
  2001年   229篇
  2000年   245篇
  1999年   222篇
  1998年   160篇
  1997年   160篇
  1996年   155篇
  1995年   127篇
  1994年   122篇
  1993年   108篇
  1992年   145篇
  1991年   175篇
  1990年   176篇
  1989年   176篇
  1988年   186篇
  1987年   148篇
  1986年   141篇
  1985年   146篇
  1984年   107篇
  1983年   76篇
  1982年   61篇
  1981年   61篇
  1979年   82篇
  1978年   60篇
  1977年   55篇
  1976年   60篇
  1975年   67篇
  1974年   56篇
  1973年   54篇
  1972年   44篇
排序方式: 共有8525条查询结果,搜索用时 15 毫秒
21.
Centrally and locally mediated vasomotor activities in Raynaud's phenomenon   总被引:3,自引:0,他引:3  
A selective review on the attack of Raynaud's phenomenon in primary Raynaud's phenomenon and vibration-induced white finger is presented with special reference to the location of the primary vasospasm, the nature of the dominant pathophysiological mechanism, and the anatomic location of the abnormal link in this mechanism. It is suggested that the primary vasospasm is a total closure of the main digital arteries, that the arterial spasm is mainly mediated through an exaggerated central sympathetic reflex mechanism, and that the abnormal link in this reflex arch could be the smooth muscle cells of the digital arteries. Other anatomic locations of the abnormal link can however not be excluded as yet.  相似文献   
22.
Summary Total parotidectomy causes a significant postoperative concave deformity in the retromandibular, preauricular, and infra-auricular regions of the face; many patients are concerned about this defect. Frey's syndrome (gustatory sweating) is also a well-recognized postoperative entity following parotid surgery. The incidence of Frey's syndrome ranges from 10–90%, depending on the type and complexity of the investigation used to diagnose it [5, 11]. Numerous methods have been described to correct these problems. Patients requiring total parotidectomy were recently offered the option of immediate reconstruction of the contour defect with microvascular transfer of a tailored gracilis muscle flap. Four patients are included in this preliminary series; all are extremely satisfied with the postoperative result. The defect following total parotidectomy can be reconstructed immediately with gratifying cosmetic results, a hidden donor site scar, and to date no operative morbidity.  相似文献   
23.
OBJECTIVE: This study proposes a method for self-report health questionnaires to adjust test-retest reliability for changes during the test-retest interval based on an external measure, and to distinguish such changes from random response errors. METHODS: In our application, eighty participants completed the Symptoms of Illness Checklist (SIC) on two occasions, two weeks apart, immediately before interviews given on each occasion by one of two physicians in a crossover design. The physician interview scores served as external measures, and structural equation modeling was used to estimate the parameters of a model that corrected for the occasion-specific effect of participants' responses using information from the interviews. RESULTS: Correcting for changes in symptoms during the test-retest interval increased SIC test-retest reliability from .744 to .804 and significantly improved model fit (chi2(diff)(1) = 30.78, p < .001). CONCLUSIONS: The results suggest methods that can improve the evaluation of self-report health questionnaire test-retest reliability by identifying changes using an external measure, and distinguishing these from random response errors; these increased the estimated SIC test-retest reliability and indicated that the SIC was indeed able to measure changes over the studied time interval. This method can be applied across a broad range of questionnaires.  相似文献   
24.
Birnholz  JC 《Radiology》1986,158(3):805-807
Ultrasound (US) can be used to visualize vertebral segments, suggesting a quantitative means of studying vertebral column growth in utero and thus a means of detecting developmental abnormalities. US images of the lumbar spine were obtained in 128 clinically normal fetuses between the gestational age of 11 through 41 weeks. A large-aperture, dynamically focused US system capable of regional magnification was used. Average lumbar spacing was calculated from distance between centrums of at least four lumbar bodies. The average distance between lumbar centrums increased nearly linearly throughout the second and third trimesters (r2 = 0.98). Enhanced anatomic display implies new capabilities for recognizing developmental abnormalities antenatally.  相似文献   
25.
26.
Phosphorus-31 nuclear magnetic resonance techniques using shallow penetrating coils have been used to noninvasively monitor severity and metabolic changes over time in skin wounds in rats. Ratios of phosphocreatine (PCr) to inorganic phosphate (Pi) indicate energy status in both thermal wounds and surgical flaps. In partial and full-thickness scald wounds, reductions in PCr/Pi ratios correlated with burn depth and improved over time postinjury, suggesting wound revascularization. No decrease in intracellular pH was noted in these wounds; the phosphate shifts may be primarily the result of tissue degradation followed by restoration of the microvasculature. Distal regions of caudally based dorsal 3 x 10 cm full-thickness skin flaps reveal progressively lower PCr/Pi ratios to 3-6 hours after elevation as well as drops in pH up to 0.5 units, presumably as a result of anaerobic glycolysis in these tissues. After 24 hours, the intracellular pH returned to normal (7.1-7.2) and the PCr/Pi ratios approached 70%-90% of the well-perfused proximal regions within 3-7 days. These results indicate the establishment of a microvasculature from the underlying bed as the distal regions survive as free grafts. The data demonstrate the potential usefulness of the technique in noninvasive measurement of the biochemical response to injury and wound healing in living organisms.  相似文献   
27.
Between March 1985 and December 1991, mediastinitis developed in 12 of 420 cardiac transplantation patients (2.8%). The mortality rate in this group of patients was 8.3% (1/12). Actuarial survival (1 year, 75%; and 5 years, 65%) was not significantly different from that of the group without mediastinitis (1 year, 88%; and 5 years, 75%). A higher percentage of the patients in the group with mediastinitis were listed as UNOS status 1 (50% versus 35%) and had a history of previous sternotomies (58% versus 44%). The presentation of mediastinitis was typical. Computed tomographic scanning with or without aspiration was a valuable adjunct in the diagnosis of mediastinitis. Induction immunotherapy with minimal steroids in the perioperative period was used in all patients. This may contribute to the patients' ability to mount an appropriate and effective response to infection, permitting earlier diagnosis. The debridement irrigation technique used in 8 of 12 patients had a low success rate of 33%, whereas the debridement muscle flap technique used in 4 of 12 was 100% successful in eliminating infection.  相似文献   
28.
Bradykinin B1 receptors are exclusively expressed in inflamed tissues. For this reason, they have been related with the outcomes of several pathologies. Ischemia–reperfusion injury is caused by the activation of inflammatory and cytoprotective genes, such as macrophage chemoattractant protein-1 and heme oxygenase-1, respectively. This study was aimed to analyze the involvement of bradykinin B1 and B2 receptors (B1R and B2R) in tissue response after renal ischemia–reperfusion injury. For that, B1R (B1−/−), B2R (B2−/−) knockout animals and its control (wild-type mice, B1B2+/+) were subjected to renal bilateral ischemia, followed by 24, 48 and 120 h of reperfusion. At these time points, blood serum samples were collected for creatinine and urea dosages. Kidneys were harvested for histology and molecular analyses by real-time PCR. At 24 and 48 h of reperfusion, B1−/− group resulted in the lowest serum creatinine and urea levels, indicating less renal damage, which was proved by renal histology. Renal protection associated with B1−/− mice was also related with higher expression of HO-1 and lower expression of MCP-1. In conclusion, the absence of B1R had a protective role against inflammatory responses developed after renal ischemia–reperfusion injury.  相似文献   
29.
Male genital oedema can be defined as swelling or the appearance of swelling of the scrotum and/or the penile shaft and prepuce. Despite the various causes of genital oedema reported in the published work, a concise approach to the evaluation and management has not been sufficiently addressed.  相似文献   
30.
BACKGROUND: The occurrence of small vessel arteriosclerosis in the myocardium, kidney, and lung in dogs with naturally occurring myxomatous mitral valve disease has not been previously investigated systematically. METHODS: Twenty-one dogs with naturally occurring congestive heart failure and 21 age-matched, sex-matched, and weight-matched control dogs underwent extensive pathological and histopathological examination. Morphometry and scoring of tissue sections were used to measure arterial narrowing and fibrosis in the myocardium, kidney, and lung; and intimal thickness and plaque formation in the aorta and pulmonary artery. RESULTS: Dogs with congestive heart failure had significantly more arterial narrowing in the left ventricle (P < .003), lung (P < .0001), and kidney (P < .02); intimal-medial thickening in the pulmonary artery (P = .04); and fibrosis in the left ventricle (P < .0001) than control dogs. However, they did not have more plaque formation or intimal-medial thickening in the aorta than controls. There was significantly more arterial narrowing in papillary muscles than in all other locations in dogs with congestive heart failure (P < .002). In control dogs, arterial changes were less pronounced and did not differ in different locations. CONCLUSIONS: Dogs with naturally occurring myxomatous mitral valve disease have significantly more arterial changes in the myocardium, lung, and kidney, and significantly more fibrosis in the myocardium than control dogs. This could have important implications in the management of myxomatous mitral valve disease and raises interesting questions about the occurrence and importance of intramural small vessel disease in humans with primary mitral valve prolapse.  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