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   18305篇
  免费   1390篇
  国内免费   49篇
耳鼻咽喉   149篇
儿科学   688篇
妇产科学   373篇
基础医学   2732篇
口腔科学   314篇
临床医学   1848篇
内科学   4109篇
皮肤病学   251篇
神经病学   1964篇
特种医学   722篇
外国民族医学   4篇
外科学   2310篇
综合类   241篇
一般理论   7篇
预防医学   1177篇
眼科学   660篇
药学   836篇
中国医学   18篇
肿瘤学   1341篇
  2021年   210篇
  2020年   132篇
  2019年   242篇
  2018年   290篇
  2017年   232篇
  2016年   273篇
  2015年   283篇
  2014年   367篇
  2013年   548篇
  2012年   798篇
  2011年   845篇
  2010年   504篇
  2009年   480篇
  2008年   688篇
  2007年   822篇
  2006年   786篇
  2005年   742篇
  2004年   763篇
  2003年   665篇
  2002年   706篇
  2001年   609篇
  2000年   600篇
  1999年   481篇
  1998年   225篇
  1997年   199篇
  1996年   176篇
  1995年   202篇
  1994年   167篇
  1993年   156篇
  1992年   435篇
  1991年   411篇
  1990年   412篇
  1989年   369篇
  1988年   360篇
  1987年   346篇
  1986年   360篇
  1985年   319篇
  1984年   277篇
  1983年   240篇
  1982年   173篇
  1981年   170篇
  1980年   149篇
  1979年   223篇
  1978年   195篇
  1977年   136篇
  1976年   146篇
  1975年   145篇
  1974年   166篇
  1973年   163篇
  1972年   133篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Acute appendicitis in the pregnant patient   总被引:6,自引:0,他引:6  
I L Tamir  F S Bongard  S R Klein 《American journal of surgery》1990,160(6):571-5; discussion 575-6
Acute appendicitis is the most common surgical problem in pregnancy requiring emergent intervention. To establish a contemporary patient profile and formulate an effective management strategy, a retrospective review was conducted of 84 pregnant patients who underwent laparotomy with a preoperative diagnosis of acute appendicitis. Gestational stage at presentation included the first trimester in 27 patients (32%), the second trimester in 37 patients (44%), the third trimester in 13 patients (16%), and the puerperium in 7 patients (8%). Fifty-four patients (64%) had pathologically proven acute appendicitis; the incidence did not vary by trimester. Other intra-abdominal conditions were detected in 15 patients (18%). There were no significant differences between patients with positive and negative laparotomies (or among trimesters) regarding frequency of presenting symptoms and signs or laboratory results. Operation occurred within 24 hours of symptom onset in 19 of 54 (35%) instances of proven acute appendicitis. Perforation occurred in 23 of 54 patients (43%), all of whom had symptoms exceeding 24 hours (p less than 0.0005). Five instances of perinatal death and one case of extreme perinatal morbidity were associated with negative laparotomies; only one of these was attributed to operation itself. No adverse long-term maternal morbidity or mortality occurred. Wound infection developed in seven cases of acute appendicitis (six perforated) and two negative explorations. We conclude that (1) gestational physiologic changes obscure the accurate diagnosis of acute appendicitis; (2) the natural history of acute appendicitis is not affected by trimester of presentation; and (3) adverse sequelae of acute appendicitis are obviated by prompt operative exploration and prevention of appendiceal perforation.  相似文献   
32.
Summary Medullary nails have only been used with reluctance in the treatment of open fractures since reaming interferes with the cortical circulation. The technique of interlocking offers the interesting possibility of inserting a relatively stiff nail which does not necessarily require reaming. The effects of reaming prior to nail insertion upon the cortical circulation was investigated in the canine tibia. Intravital staining with procion red was used to trace areas of disturbed circulation. Nail insertion without reaming provided clear advantages for the bone's blood supply, while reaming disturbed perfusion in two-thirds of the cortical area and regionally extended through the entire thickness of the cortex. The disturbance without reaming was limited to the inner layer of the cortex and involved only one-third of the cortical cross-section.  相似文献   
33.
We have treated 39 infants and children with congenital heart disease with extracorporeal membrane oxygenation during the past 5 years. Thirty-six were treated for low cardiac output or pulmonary vasoreactive crisis after repair of congenital heart defects. Twenty-two (61%) survived. Most patients were cannulated from the neck via the right internal jugular vein and the right common carotid artery. Six patients were cannulated from the chest, including three who had separate drainage of the left side of the heart with a left atrial cannula. Two of these patients survived and were the only survivors of the nine patients cannulated in the operating room because they could not be weaned from cardiopulmonary bypass after open cardiac operations. We also reviewed 312 patients (the predictor study series) having open cardiac operations before the availability of extracorporeal membrane oxygenation; 27 of these patients died. Data were collected at 1 and 8 hours postoperatively to determine if any parameters might predict early mortality. With these parameters used as criteria, patients who went on extracorporeal membrane oxygenation were as sick as those who died before extracorporeal membrane oxygenation was available. The most common complication was bleeding related to heparinization. The mean transfusion requirement in survivors was 1.50 +/- 1.13 ml/kg/hr, 5.63 +/- 7.0 ml/kg/hr in the nonsurvivors, and 7.46 +/- 8.29 ml/kg/hr in those cannulated in the operating room because they could not be weaned from bypass. Four children had intracranial hemorrhage, and two of them died. There was one late death. Nine of the 22 survivors are entirely normal. All survivors who do not have Down's syndrome are considered to have normal central nervous system function. We conclude that extracorporeal membrane oxygenation can improve survival in patients with both pulmonary artery hypertension and low cardiac output after operations for congenital heart disease.  相似文献   
34.
35.
36.
Background: Volatile anesthetics are commonly used for general anesthesia. However, these can induce profound cardiovascular alterations. Xenon is a noble gas with potent anesthetic and analgesic properties. However, it is uncertain whether xenon alters myocardial function. The aim of this study was therefore to investigate left ventricular function during anesthesia with xenon compared with isoflurane.

Methods: The authors performed a randomized multicenter trial to compare xenon with isoflurane with respect to cardiovascular stability and adverse effects in patients without cardiac diseases scheduled for elective surgery. Two hundred fifty-nine patients were enrolled in this trial, of which 252 completed the study according to the protocol. Patients were anesthetized with xenon or isoflurane, respectively. Before administration of the study drugs and at four time points, the effects of both anesthetics on left ventricular function were investigated using transesophageal echocardiography.

Results: Global hemodynamic parameters were significantly altered using isoflurane (P < 0.05 vs. baseline), whereas xenon only decreased heart rate (P < 0.05 vs. baseline). In contrast to xenon, left ventricular end-systolic wall stress decreased significantly in the isoflurane group (P < 0.05 vs. baseline). Velocity of circumferential fiber shortening was decreased significantly in the xenon group but showed a more pronounced reduction during isoflurane administration (P < 0.05 vs. baseline). The contractile index (difference between expected and actually measured velocity of circumferential fiber shortening) as an independent parameter for left ventricular function was significantly decreased after isoflurane (P < 0.0001) but unchanged using xenon.  相似文献   

37.
Over 3 years, 972 families participated in an after-school asthma program at their child's school. Parents and children attended concurrent 21/2 -hour workshops. Parents were 74% Latino; 45% non-English speaking, with 77% of children on Medicaid. Asthma symptoms were significantly reduced, from multiple times per week to less than once per week on average. Oral steroid use decreased to one third of baseline use. Hospital days decreased from 11% to 2%; emergency visits decreased 35% to 4%; and school days missed decreased 48% to 20%. This program has now become sustainable with both private and Medicaid insurance coverage.  相似文献   
38.
39.
We describe the clinical courses of 3 patients with hematologic malignancies (2 with acute myelogenous leukemia and 1 with multiple myeloma) who developed invasive fungal infections due to uncommon molds (Alternaria spp., Paecilomyces lilacinus, and Zygomycetes). Breakthrough invasive fungal infections of the sinus (n=1), lung (n=3), and pericardium (n=1) developed despite fluconazole prophylaxis and failed to respond to treatment with other licensed antifungal therapies, including amphotericin B (n=3), caspofungin (n=2), and voriconazole (n=3), and surgical intervention (n=2). Salvage therapy with posaconazole oral suspension resulted in successful outcomes in all 3 patients, who subsequently underwent allogeneic hematopoietic stem cell transplantation (HSCT) while on continued posaconazole therapy. The median duration of posaconazole treatment before HSCT was 5 months (range: 1.5-6 months). Posaconazole salvage therapy allowed successful allogeneic HSCT in 3 patients with refractory invasive mold infections.  相似文献   
40.
Drug use and HIV infection may affect sex hormone levels in women. One hundred and ninety-six women with and without a history of illicit drug use (50 HIV-negative and 148 HIV-infected), with regular menses, who never used antiretrovirals, were evaluated. Luteinizing hormone levels were significantly higher in women with a CD4 cell count <200/microl (p < 0.002). Current methadone use was associated with lower levels of total testosterone (p = 0.03) and higher levels of prolactin (p = 0.002); mean estradiol levels were 43% lower in women who used intravenous drugs (p < 0.001). Alcohol and crack cocaine use was not associated with sex hormone levels. Age, race, body mass index and degree of HIV immunosuppression were also associated with differences in sex hormone levels.  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