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   24241篇
  免费   1326篇
  国内免费   277篇
耳鼻咽喉   474篇
儿科学   329篇
妇产科学   273篇
基础医学   4336篇
口腔科学   581篇
临床医学   2012篇
内科学   4625篇
皮肤病学   888篇
神经病学   1807篇
特种医学   1474篇
外科学   2958篇
综合类   157篇
现状与发展   1篇
一般理论   5篇
预防医学   1089篇
眼科学   448篇
药学   2101篇
中国医学   284篇
肿瘤学   2002篇
  2023年   154篇
  2022年   512篇
  2021年   820篇
  2020年   404篇
  2019年   570篇
  2018年   646篇
  2017年   533篇
  2016年   738篇
  2015年   1085篇
  2014年   1304篇
  2013年   1447篇
  2012年   2165篇
  2011年   2056篇
  2010年   1176篇
  2009年   1077篇
  2008年   1460篇
  2007年   1338篇
  2006年   1146篇
  2005年   1016篇
  2004年   865篇
  2003年   761篇
  2002年   655篇
  2001年   580篇
  2000年   483篇
  1999年   401篇
  1998年   193篇
  1997年   151篇
  1996年   120篇
  1995年   128篇
  1994年   82篇
  1993年   70篇
  1992年   149篇
  1991年   153篇
  1990年   116篇
  1989年   147篇
  1988年   125篇
  1987年   123篇
  1986年   103篇
  1985年   102篇
  1984年   73篇
  1983年   66篇
  1982年   57篇
  1981年   50篇
  1980年   47篇
  1979年   49篇
  1978年   57篇
  1977年   53篇
  1976年   39篇
  1974年   30篇
  1973年   34篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
241.
Alveolar soft part sarcoma: MR and angiographic findings   总被引:5,自引:5,他引:0  
Suh JS  Cho J  Lee SH  Shin KH  Yang WI  Lee JH  Cho JH  Suh KJ  Lee YJ  Ryu KN 《Skeletal radiology》2000,29(12):680-689
Objective. To present the MR and angiographic findings of alveolar soft part sarcoma (ASPS). Design and patients. MR examinations (12 tumors of 10 patients) of ASPS performed at multiple hospitals were retrospectively reviewed. The tumors were found in the thigh (n=4), lower leg (n=4), femur (n=2, local metastasis), scalp (n=1) and arm (n=1). The MR signal characteristics including signal intensity, homogeneity and signal void of lesions and bony invasion including direct invasion or local metastasis were evaluated. Angiographic findings (n=4) and post-embolotherapy follow-up MR imaging (n=2) findings were also assessed. Results. Local bony metastasis was found in two cases. Seven tumors showed heterogeneous high signal intensity on T1- and T2-weighted images with good enhancement. One tumor had a very high signal on T1-weighted images. Eight tumors (67%) showed numerous signal voids in or near the tumors. All four angiographic studies showed numerous enlarged vessels, arteriovenous shunts and delayed washout. Two cases mimicked arteriovenous malformations on angiographic studies but MR images demonstrated solid soft tissue components as well as tortuous vessels. Conclusions. High signal on T1-weighted image and numerous signal voids are highly suggestive of ASPS, although they are not universal as has been suggested and arteriovenous malformation should be included in the differential diagnosis. Local bony metastases in ASPS were seen in two cases and should be carefully investigated. Received: 12 April 2000 Revision requested: 27 June 2000, 8 August 2000 Revision received: 2 August 2000, 21 August 2000 Accepted: 22 August 2000  相似文献   
242.
243.
Background: Redistribution hypothermia caused by vasodilation during anesthesia is the primary cause of perioperative hypothermia. Propofol exerts a dose-dependent vasodilatory effect, whereas dexmedetomidine induces peripheral vasoconstriction at high plasma concentrations. This study compared the effects of dexmedetomidine and propofol on core temperature in patients undergoing surgery under spinal anesthesia.Methods: This prospective study included 40 patients (aged 19-70 years) with American Society of Anesthesiologists Physical Status class I-III who underwent elective orthopedic lower-limb surgery under spinal anesthesia. Patients were randomly allocated to a dexmedetomidine or propofol group (n = 20 per group). After induction of spinal anesthesia, patients received dexmedetomidine (loading dose: 1 μg/kg over 10 min; maintenance dose: 0.2-0.7 μg/kg/h) or propofol (loading dose: 75 μg/kg over 10 min; maintenance dose: 12.5-75 μg/kg/min). The doses of sedatives were titrated to maintain moderate sedation. During the perioperative period, tympanic temperatures, thermal comfort score, and shivering grade were recorded.Results: Core temperature at the end of surgery did not differ significantly between the groups (36.4 ± 0.4 and 36.1 ± 0.7°C in the dexmedetomidine and propofol groups, respectively; P = 0.118). The lowest perioperative temperature, incidence and severity of perioperative hypothermia, thermal comfort score, and shivering grade did not differ significantly between the groups (all P > 0.05).Conclusions: In patients undergoing spinal anesthesia with moderate sedation, the effect of dexmedetomidine on patients'' core temperature was similar to that of propofol.  相似文献   
244.
245.
BackgroundIt has been known that the fear of contagion during the coronavirus disease 2019 (COVID-19) creates time delays with subsequent impact on mortality in patients with acute myocardial infarction (AMI). However, difference of time delay and clinical outcome in patients with ST-segment elevation myocardial infarction (STEMI) or non-STEMI between the COVID-19 pandemic and pre-pandemic era has not been fully investigated yet in Korea. The aim of this study was to investigate the impact of COVID-19 pandemic on time delays and clinical outcome in patients with STEMI or non-STEMI compared to the same period years prior.MethodsA total of 598 patients with STEMI (n = 195) or non-STEMI (n = 403) who underwent coronary angiography during the COVID-19 pandemic (February 1 to April 30, 2020) and pre-pandemic era (February 1 to April 30, 2017, 2018, and 2019) were analyzed in this study. Main outcomes were the incidence of time delay, cardiac arrest, and in-hospital death.ResultsThere was 13.5% reduction in the number of patients hospitalized with AMI during the pandemic compared to pre-pandemic era. In patients with STEMI, door to balloon time tended to be longer during the pandemic compared to pre-pandemic era (55.7 ± 12.6 minutes vs. 60.8 ± 13.0 minutes, P = 0.08). There were no significant differences in cardiac arrest (15.6% vs. 10.4%, P = 0.397) and in-hospital mortality (15.6% vs. 10.4%, P = 0.397) between pre-pandemic and the pandemic era. In patients with non-STEMI, symptom to door time was significantly longer (310.0 ± 346.2 minutes vs. 511.5 ± 635.7 minutes, P = 0.038) and the incidence of cardiac arrest (0.9% vs. 3.5%, P = 0.017) and in-hospital mortality (0.3% vs. 2.3%, P = 0.045) was significantly greater during the pandemic compared to pre-pandemic era. Among medications, angiotensin converting enzyme inhibitors/angiotensin type 2 receptor blockers (ACE-I/ARBs) were underused in STEMI (64.6% vs. 45.8%, P = 0.021) and non-STEMI (67.8% vs. 57.0%, P = 0.061) during the pandemic.ConclusionDuring the COVID-19 pandemic, there has been a considerable reduction in hospital admissions for AMI, time delay, and underuse of ACE-I/ARBs for the management of AMI, and this might be closely associated with the excess death in Korea.  相似文献   
246.
Four new 3-methyl-4-ethylideneproline-containing peptides, lucentamycins A-D (1-4), have been isolated from the fermentation broth of a marine-derived actinomycete identified by phylogenetic methods as Nocardiopsis lucentensis (strain CNR-712). The planar structures of the new compounds were assigned on the basis of 1D and 2D NMR spectroscopic techniques, while the absolute configurations of the amino acid residues were determined by application of the advanced Marfey method. Lucentamycins A (1) and B (2) showed significant in vitro cytotoxicity against HCT-116 human colon carcinoma.  相似文献   
247.
248.
This study aims to compare the efficacy and safety between two different doses of intravitreal bevacizumab injection (IVB) with temporal retina-sparing laser photocoagulation (TRSL) for retinopathy of prematurity (ROP). We retrospectively evaluated 22 eyes of ROP infants who underwent IVB combined with partial TRSL for stage 3+ zone I or posterior zone II ROP. Laser photocoagulation was applied on the avascular retina, sparing two-disc-diameter width temporal avascular area anterior to ridge. A half dose (0.625 mg) or minimal dose (0.25 mg) of IVB was conducted. Four eyes in minimal dose group were retreated with IVB and laser photocoagulation on the spared retina. Of those 4 retreated eyes, three developed preretinal hemorrhage around the ridge after the first treatment, resulting in fibrotic macular dragging. A half dose of IVB may be more effective than a minimal dose with partial TRSL for ROP. Preretinal hemorrhage may be a harbinger of poor prognosis.  相似文献   
249.
250.

Study Objective

To evaluate the incidence of pelvic inflammatory disease (PID) in virgin women and investigate the clinical characteristics of the patients.

Design

Retrospective chart review and literature review.

Setting

Tertiary academic center.

Participants

Virgin women who were confirmed to have PID via surgery from 2002 to 2014.

Interventions

None.

Main Outcome Measures

The evaluation of medicosurgical history, clinical progress, surgical record, and pathologic reports.

Results

Of 122 patients diagnosed with PID via surgery, 5 women were virgins (4.1%). The median age was 21 years (range, 14-24 years), and all patients presented with abdominal pain. The median diameter of the pelvic abscess pocket on preoperative imaging was 4.5 cm (range, 2.6-15 cm). Only 1 case was preoperatively diagnosed as a tubo-ovarian abscess; the others were expected to be benign ovarian tumors, such as endometrioma and dermoid cysts. No possible source of infection was identified for any patient, except 1 who had a history of an appendectomy because of a ruptured appendix. The results of the histopathological analysis of the excisional biopsy performed during surgery in 4 cases were consistent with acute suppurative inflammation. After postoperative antibiotic use, the conditions of all patients stabilized, and they were discharged from the hospital on median postoperative day 9.

Conclusion

PID in virgin women is rare, but it should be considered in all women with abdominal pain, regardless of sexual history.  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