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   8273篇
  免费   450篇
  国内免费   27篇
耳鼻咽喉   114篇
儿科学   281篇
妇产科学   155篇
基础医学   1045篇
口腔科学   523篇
临床医学   542篇
内科学   1575篇
皮肤病学   189篇
神经病学   663篇
特种医学   163篇
外科学   1056篇
综合类   96篇
一般理论   5篇
预防医学   921篇
眼科学   159篇
药学   867篇
中国医学   62篇
肿瘤学   334篇
  2023年   75篇
  2022年   61篇
  2021年   156篇
  2020年   118篇
  2019年   147篇
  2018年   285篇
  2017年   232篇
  2016年   226篇
  2015年   291篇
  2014年   276篇
  2013年   415篇
  2012年   659篇
  2011年   726篇
  2010年   335篇
  2009年   227篇
  2008年   581篇
  2007年   496篇
  2006年   438篇
  2005年   475篇
  2004年   456篇
  2003年   381篇
  2002年   303篇
  2001年   205篇
  2000年   187篇
  1999年   145篇
  1998年   33篇
  1997年   30篇
  1996年   25篇
  1995年   20篇
  1994年   24篇
  1993年   14篇
  1992年   70篇
  1991年   66篇
  1990年   46篇
  1989年   49篇
  1988年   50篇
  1987年   41篇
  1986年   39篇
  1985年   31篇
  1984年   26篇
  1983年   16篇
  1977年   13篇
  1974年   21篇
  1973年   18篇
  1972年   18篇
  1971年   15篇
  1970年   14篇
  1969年   18篇
  1967年   19篇
  1966年   17篇
排序方式: 共有8750条查询结果,搜索用时 15 毫秒
21.
INTRODUCTION: In patients (pts) with atrial fibrillation (AF) of more than 48 hours' duration, electrical cardioversion (ECV) should only be performed after 3 weeks of effective anticoagulation. Transesophageal echocardiography (TEE) allows earlier ECV; however, despite exclusion of thrombi in the atrium and left atrial appendage (LAA), cases of thromboembolism related to ECV have been documented in AF. To define a low-risk group for cardioversion without previous anticoagulation, pts were selected for immediate ECV if no thrombi or dynamic spontaneous echo contrast (auto-contrast) were found after TEE and if LAA velocity was more than 0.25 m/sec. METHODS AND RESULTS: We performed TEE in 31 consecutive pts referred for ECV for AF of more than 48 hours' duration and without previous anticoagulation. After TEE the pts eligible for immediate ECV began anticoagulation with low molecular weight heparin (enoxaparin), subcutaneously in therapeutic doses, together with warfarin immediately before cardioversion. Enoxaparin was continued until an INR of over 2 was reached. Based on the TEE findings, the pts were divided in 2 groups: immediate ECV, group A, 20 pts with a mean age of 62 +/- 13 years, 6 female; and conventional therapy with warfarin before ECV, group B, 11 pts, mean age of 67 +/- 10 years (p < 0.05), 2 female. None of the pts in either group had mitral stenosis or previous episodes of thromboembolism. The mean transverse diameter of the left atrium in the 31 pts was 47 +/- 4.5 mm, without statistically significant differences between the 2 groups. Of the 11 pts in group B, 3 had a thrombus in the LAA, 6 dynamic spontaneous echo contrast and the remainder LAA velocities of less than 0.25 m/sec. ECV was achieved in all the pts, with no complications. Oral anticoagulation was maintained for at least a month. At one month, sinus rhythm was maintained in 75% of group A and 45% of group B (p < 0.01). CONCLUSION: In pts with AF of more than 48 hours' duration and no previous history of thromboembolism, the use of our exclusion criteria during TEE enabled stratification of a low-risk population for immediate ECV, which was accomplished effectively and safely in 2/3 of the pts. This strategy is associated with early symptomatic improvement, and may contribute to maintenance of sinus rhythm after one month, which was significantly better than in the pts who had prolonged therapy with warfarin before ECV, despite the differences found in age and left ventricular function.  相似文献   
22.
Pulmonary embolism (PE) is an important health problem and often a major clinical challenge, not only because of the low specificity of its clinical manifestations but also because of the increasing number of medical circumstances that are risk factors for this illness and the importance of early identification, since prompt and appropriate treatment can decrease mortality from this disease by about 25%. In recent years research on PE has been extensive, directed mainly at trying to determine and characterize its risk factors, establish new clinical probability algorithms, develop new diagnostic methods and put existing ones into perspective, seek new therapeutic approaches (pharmacological and non-pharmacological), and above all establish protocols that can guide the clinician from the stage of clinical suspicion to measures to prevent recurrence. It was the authors' aim to review the most significant literature on this subject, in order to produce a text that reflects the state of the art concerning PE and that can be used as a guide in the clinical approach to this pathology.  相似文献   
23.
OBJECTIVE: To test the hypothesis that short stature is associated with abdominal obesity, insulin resistance and lipid profile changes. METHODS: Anthropometric data were collected from 237 women (18-60 years old), residents of a shantytown in Maceió. Biochemical profiles of 60 individuals drawn from this population were determined. RESULTS: Total and low-density lipoprotein (LDL) cholesterol levels and insulin resistance rose with increasing waist : hip circumference ratio, particularly in women. Short, overweight individuals exhibited larger biochemical alterations than overweight individuals of average stature. CONCLUSION: Short stature, when associated with overweight, is a risk factor for increased insulin resistance and alterations in lipid profile.  相似文献   
24.
We observed histopathological and ultrastructural hepatic changes following the intracardiac inoculation ofLeishmania donovani amastigotes into inbred LHC hamsters (group I). Since granuloma formation is known to be T-cell-dependent, we also examined infected hamsters under cyclophosphamide immunosuppressive treatment (group ICy) and evaluated the production of interleukin-2 (IL-2) by their cells. Group I showed more intense hepatocyte and endothelial cell clasmatosis as well as hepatocyte degeneration and necrosis, deposits of connective tissue fibers, granulomas with multinucleated giant cells (MGCs) of foreign-body and Langhans' types and reduced production of IL-2 by spleen cells. In contrast, group ICy hamsters exhibited larger eosinophil and lymphocyte populations within sinusoids and peri-sinusoidal areas but showed no MGCs in granulomas. A striking decline in IL-2 production was noted. These results suggest that cyclophosphamide induces a delay in the natural evolution ofL. donovani-induced granulomatous hepatic inflammation.  相似文献   
25.
Zusammenfassung Viele Herzerkrankungen k?nnen heute im Rahmen von Schwangerschaftsvorsorgeuntersuchungen frühzeitig diagnostiziert werden. So ist in vielen F?llen, besonders bei Herzrhythmusst?rungen, eine kurative pr?natale Therapie m?glich. Bei strukturellen Herzfehlern ist eine Therapie jedoch, abgesehen von der Behandlung einer m?glichen Herzinsuffizienz oder begleitender Herzrhythmusst?rungen, h?ufig erst nach der Geburt m?glich. Ist der Herzfehler bereits pr?natal erkannt, so kann das herzkranke Neugeborene ohne Zeitverz?gerung in einer kinderkardiologischen Klinik weiter betreut werden. Neben medikament?sen Behandlungsm?glichkeiten ist in vielen F?llen eine frühzeitige interventionelle und/oder chirurgische Therapie für die Prognose des herzkranken Neugeborenen besonders wichtig. Im folgenden werden aktuelle Behandlungsmethoden für angeborene Herzfehler anhand einiger typischer Beispiele mit besonderer Berücksichtigung von herzkranken Neugeborenen und S?uglingen aufgezeichnet.  相似文献   
26.
27.
28.
Ischemia negatively affects mitochondrial function by inducing the mitochondrial permeability transition (MPT). The MPT is triggered by oxidative stress, which occurs in mitochondria during ischemia as a result of diminished antioxidant defenses and increased reactive oxygen species production. It causes mitochondrial dysfunction and can ultimately lead to cell death. Therefore, drugs able to minimize mitochondrial damage induced by ischemia may prove to be clinically effective. We analyzed the effect of carvedilol, a beta-blocker with antioxidant properties, on mitochondrial dysfunction. Carvedilol decreased levels of TBARS (thiobarbituric acid reactive substances), an indicator of oxidative stress, which is consistent with its antioxidant properties. Regarding cell death by apoptosis, although ischemia did increase caspase-8-like activity, there were no changes in caspase-3-like activity, which is activated downstream of caspase-8; this may indicate that the apoptotic cascade is not activated by 60 minutes of ischemia. We conclude that carvedilol protects ischemic mitochondria by preventing oxidative mitochondrial damage, and, by so doing, it may also inhibit the formation of the MPT pore.  相似文献   
29.
BACKGROUND: Some skin carcinomas may be very aggressive. Increased expression of the protein p53 has been associated with tumor aggressiveness. In this study, p53 expression was evaluated in basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) with skull base invasion, and was compared to tumors with good outcome. STUDY DESIGN AND SETTING: Expression of p53 was immunohistochemically analyzed and it was reported as present or absent in 24 BCC and 11 SCC with skull base invasion. Control group (good outcome) included 23 BCC and 10 SCC. RESULTS: Expression of p53 was noted in 70.83% of BCC with skull base invasion, compared to 43.48% in the control group (P = 0.058). Regarding SCC, p53 positivity was noted in only 9.09% of SCC with skull base invasion, compared to 40.00% in the control group (P = 0.149). CONCLUSIONS: In this study, p53 expression was more common among BCC with skull base invasion, compared to controls with good outcome, and the difference was considered marginally significant. This proportion was reversed in SCC, but the difference was not statistically significant. EBM rating: B-3b.  相似文献   
30.
We reviewed the charts of 39 patients (45 eyes) with uveitis who underwent cataract extraction (intracapsular or extracapsular) with or without implantation of a posterior chamber intraocular lens (IOL) at the Royal Victoria Hospital, Montreal, between 1981 and 1990. The nine eyes with Fuchs' iridocyclitis in which an IOL was implanted had good visual results and few postoperative complications. The 18 eyes with uveitis other than Fuchs' iridocyclitis that received an IOL did not show a greater risk of postoperative complications than those left aphakic (n = 17), and the postoperative visual acuity was comparable to that of the aphakic eyes. Although the numbers are small, we conclude that the presence of uveitis does not automatically exclude posterior chamber pseudophakia.  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