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   3605篇
  免费   213篇
  国内免费   14篇
耳鼻咽喉   41篇
儿科学   98篇
妇产科学   67篇
基础医学   366篇
口腔科学   158篇
临床医学   274篇
内科学   930篇
皮肤病学   50篇
神经病学   350篇
特种医学   83篇
外科学   644篇
综合类   25篇
一般理论   1篇
预防医学   215篇
眼科学   88篇
药学   205篇
中国医学   14篇
肿瘤学   223篇
  2023年   22篇
  2022年   54篇
  2021年   105篇
  2020年   69篇
  2019年   109篇
  2018年   108篇
  2017年   85篇
  2016年   90篇
  2015年   86篇
  2014年   130篇
  2013年   154篇
  2012年   267篇
  2011年   258篇
  2010年   164篇
  2009年   151篇
  2008年   248篇
  2007年   230篇
  2006年   244篇
  2005年   236篇
  2004年   194篇
  2003年   168篇
  2002年   161篇
  2001年   26篇
  2000年   18篇
  1999年   41篇
  1998年   35篇
  1997年   48篇
  1996年   35篇
  1995年   26篇
  1994年   17篇
  1993年   18篇
  1992年   16篇
  1991年   12篇
  1990年   9篇
  1989年   10篇
  1988年   11篇
  1987年   8篇
  1986年   11篇
  1985年   14篇
  1984年   12篇
  1983年   9篇
  1982年   20篇
  1981年   16篇
  1980年   12篇
  1979年   9篇
  1978年   7篇
  1977年   7篇
  1975年   8篇
  1974年   6篇
  1973年   9篇
排序方式: 共有3832条查询结果,搜索用时 15 毫秒
41.

Background

Despite the emergence of new therapies for respiratory failure of the newborn with meconium aspiration syndrome (MAS), extracorporeal membrane oxygenation (ECMO) has a significant role as a rescue modality in these infants. Our objective was to compare the use of venovenous (VV) vs venoarterial (VA) ECMO in newborns with MAS who need ECMO and to ascertain the impact of new therapies in these infants during the last decade. We also evaluated how disease severity or time of ECMO initiation affected mortality and morbidity.

Methods

A report of 12 years experience (1990-2002) of a single center, comparing VV and VA ECMO, is given. Venovenous ECMO was the preferred rescue modality for respiratory failure unresponsive to maximal medical therapy. Venoarterial ECMO was used only when the placement of a VV ECMO 14-F catheter was not possible; 128 patients met ECMO criteria, 114 were treated with VV ECMO, and 12 with VA ECMO. Two patients were converted from VV to VA ECMO.

Results

Venovenous and VA ECMO patients had comparable birth weight (mean ± SEM, 3.48 ± 0.05 vs 3.35 ± 0.15 kg) and gestational age (40.3 ± 0.1 vs 40.7 ± 0.3 weeks). Before ECMO, there was no difference between VV and VA ECMO patients in oxygenation index (60 ± 3 vs 63 ± 8), mean airway pressure (19.5 ± 0.4 vs 20.8 ± 1.5 cm H2O), alveolar-arterial O2 gradient (630 ± 2 vs 632 ± 4 torr), ECMO cannulation age (median [25th-75th percentiles], 23 [14-47] vs 26 [14-123] hours), or in the % of patients who needed vasopressors/inotropes (98% vs 100%). From November 1994, inhaled nitric oxide (NO) was available. Before VV ECMO, 67% of the patients received NO, 24% received surfactant, and 48% were treated with high-frequency ventilation (HFV). There was no significant difference between VV and VA ECMO patients in survival rate (94% vs 92%), ECMO duration (88 [64-116] vs 94 [55-130] hours), time of extubation (9 [7-11] vs 14 [9-15] days), age at discharge (23 [18-30] vs 27 [15-41] days), or incidence of short-term intracranial complications (5.3% vs 16.7%). For the total cohort of 126 infants, indices of disease severity (oxygenation index, alveolar-arterial O2 gradient, mean airway pressure) did not correlate with outcome measures. Delay in ECMO initiation (>96 hours) was associated with prolonged mechanical ventilation and hospitalization (P < .01). New therapies (NO, HFV, surfactant) in the second part of the decade were associated with a longer ECMO duration (98 [80-131] vs 87 [60-116] hours; P < .05), no delay in ECMO initiation time (23 [10-40] vs 24 [14-52] hours), and no significant change in survival (97% vs 92.5%). No patient was treated with VA ECMO after 1994.

Conclusions

Venovenous ECMO is as reliable as VA ECMO in newborns with MAS in severe respiratory failure who need ECMO. Delay in ECMO initiation may result in prolonged mechanical ventilation and increased length of hospital stay. The emergence of new conventional therapies (NO, HFV, surfactant) and particularly increased experience enable sole use of VV ECMO with no significant change in survival in infants with MAS.  相似文献   
42.
Background: Gout is associated with increased body weight. We evaluated the prevalence of gout and acute gouty attacks in the morbidly obese population who underwent bariatric surgery. Methods: The medical records and operative reports of 1,240 patients who underwent bariatric surgery were reviewed retrospectively for weight parameters, BMI, weight loss, medical history of gout, and onset of acute gouty attacks. Results: Of the 1,240 patients, 5 (0.4%) had been previously diagnosed with gout. 2 of these 5 had acute attacks during the postoperative period, and responded succesfully to intravenous colchicine. Conclusion: Although rare, gout must be considered a co-morbid illness in obese and morbidly obese patients. Surgeons should be familiar with the signs and symptoms of attacks in the postoperative period, and be knowledgeable in the management.  相似文献   
43.
Background: The cardiotoxic mechanism of local anesthetics may include interruption of cardiac sympathetic reflexes. The authors undertook this investigation to determine if clinically relevant concentrations of bupivacaine and levobupivacaine interfere with exocytotic norepinephrine release from cardiac sympathetic nerve endings.

Methods: Rat atria were prepared for measurements of twitch contractile force and 3[H]-norepinephrine release. After nerve endings were loaded with 3[H]-norepinephrine, the tissue was electrically stimulated in 5-min episodes during 10 10-min sampling periods. After each period, a sample of bath fluid was analyzed for radioactivity and 3[H]-norepinephrine release was expressed as a fraction of tissue counts. Atria were exposed to buffer alone during sampling periods 1 and 2 (S1 and S2). Control atria received saline (100 [mu]l each, n = 6 atria) in S3-S10. Experimental groups (n = 6 per group) received either bupivacaine or levobupivacaine at concentrations (in [mu]M) of 5 (S3-S4), 10 (S5-S6), 30 (S7-S8), and 100 (S9-S10).

Results: Bupivacaine and levobupivacaine decreased stimulation-evoked fractional 3[H]-norepinephrine release with inhibitory concentration 50% values of 5.1 +/- 0.5 and 6.1 +/- 1.3 [mu]m. The inhibitory effect of both local anesthetics (~70%) approached that of tetrodotoxin. Local anesthetics abolished the twitch contractions of atria with inhibitory concentration 50% values of 12.6 +/- 5.0 [mu]m (bupivacaine) and 15.7 +/- 3.9 [mu]m (levobupivacaine). In separate experiments, tetrodotoxin inhibited twitch contractile force by only 30%.  相似文献   

44.
Context  Abciximab infusion and uncoated-stent implantation is a complementary treatment strategy to reduce major adverse cardiac events in patients undergoing angioplasty for ST-segment elevation myocardial infarction (STEMI). It is uncertain whether there may be similar benefits in replacing abciximab with high-dose bolus tirofiban. Similarly, the use of drug-eluting stents in this patient population is currently discouraged because of conflicting results on efficacy reported in randomized trials and safety concerns reported by registries. Objective  To evaluate the effect of high-dose bolus tirofiban and of sirolimus-eluting stents as compared with abciximab infusion and uncoated-stent implantation in patients with STEMI undergoing percutaneous coronary intervention. Design, Setting, and Patients  An open-label, 2 x 2 factorial trial of 745 patients presenting with STEMI or new left bundle-branch block at 16 referral centers in Italy, Spain, and Argentina between October 2004 and April 2007. Interventions  High-dose bolus tirofiban vs abciximab infusion and sirolimus-eluting stent vs uncoated stent implantation. Main Outcome Measures  For drug comparison, at least 50% ST-segment elevation resolution at 90 minutes postintervention with a prespecified noninferiority margin of 9% difference (relative risk, 0.89); for stent comparison, the rate of major adverse cardiac events, defined as the composite of death from any cause, reinfarction, and clinically driven target-vessel revascularization within 8 months. Results  ST-segment resolution occurred in 302 of 361 patients (83.6%) who had received abciximab infusion and 308 of 361 (85.3%) who had received tirofiban infusion (relative risk, 1.020; 97.5% confidence interval, 0.958-1.086; P < .001 for noninferiority). Ischemic and hemorrhagic outcomes were similar in the tirofiban and abciximab groups. At 8 months, major adverse cardiac events occurred in 54 patients (14.5%) with uncoated stents and 29 (7.8%) with sirolimus stents (P = .004), predominantly reflecting a reduction of revascularization rates (10.2% vs 3.2%). The incidence of stent thrombosis was similar in the 2 stent groups. Conclusions  In patients with STEMI undergoing percutaneous coronary intervention, compared with abciximab, tirofiban therapy was associated with noninferior resolution of ST-segment elevation at 90 minutes following coronary intervention, whereas sirolimus-eluting stent implantation was associated with a significantly lower risk of major adverse cardiac events than uncoated stents within 8 months after intervention. Trial Registration  clinicaltrials.gov Identifier: NCT00229515   相似文献   
45.
Objective: We propose and validate a computer—aided system to measure three different mandibular indexes: cortical width, panoramic mandibular index and, mandibular alveolar bone resorption index. Study Design: Repeatability and reproducibility of the measurements are analyzed and compared to the manual estimation of the same indexes. Results: The proposed computerized system exhibits superior repeatability and reproducibility rates compared to standard manual methods. Moreover, the time required to perform the measurements using the proposed method is negligible compared to perform the measurements manually. Conclusions: We have proposed a very user friendly computerized method to measure three different morphometric mandibular indexes. From the results we can conclude that the system provides a practical manner to perform these measurements. It does not require an expert examiner and does not take more than 16 seconds per analysis. Thus, it may be suitable to diagnose osteoporosis using dental panoramic radiographs. Key words:Osteoporosis, panoramic mandibular index, cortical width, mandibular alveolar bone resorption index.  相似文献   
46.
PURPOSE: To characterize the clinical and imaging features of orbital leukemic tumors in 27 patients seen and treated at St. Jude Children's Research Hospital. METHODS: A retrospective review was performed on the clinical and imaging records of 27 consecutive patients with a diagnosis of orbital leukemic tumors. The following data were extracted from the patients' records: age at diagnosis of orbital leukemic tumors, sex, race, national origin, type of leukemia, temporal relationship of orbital disease to diagnosis of leukemia, survival from diagnosis of orbital leukemic tumor, laterality of the orbital disease, location of the mass within the orbit, imaging features of the mass, chemotherapeutic protocol, treatment with bone marrow transplant, and orbital radiation. RESULTS: The median age at diagnosis of orbital leukemic tumor was 8 years (range, 1-18 years). Nineteen of the 27 patients were male, and 21 patients were born and lived in the United States. Twenty-one patients had acute myeloid leukemia, five had acute lymphoblastic leukemia, and one had chronic myelogenous leukemia. In 85% of patients (n = 23), the diagnosis of leukemia was based on the bone marrow examination findings. Orbital imaging revealed homogenous masses that molded to one or more orbital walls without bony destruction. Nine patients had bilateral orbital involvement. All patients received multiagent systemic chemotherapy, and 14 underwent bone marrow transplantation. Five patients received external beam radiation for the treatment of orbital disease. Fifteen (55.6%) of the 27 patients were alive at the time of the study. The median survival for all patients was 4.75 years (range, 0.1-24 years) after the diagnosis of orbital disease. CONCLUSIONS: Orbital leukemic tumors occur most commonly in the first decade of life, in association with acute myeloid leukemia. They appear as homogenous masses along the orbital walls. Although the overall survival rate for patients with leukemia has improved over the past 3 decades, the mortality of patients who develop orbital leukemic tumors remains high.  相似文献   
47.
Treatment abandonment, the failure to complete therapy that is required for definitive disease control, frequently causes treatment failure for pediatric patients in low‐ and middle‐income countries with chronic conditions, particularly cancer. Other forms of incomplete treatment affecting children in all settings, such as nonadherence and loss to follow‐up, are often confused with treatment abandonment. Unclear definitions of incomplete treatment dramatically affect reported outcomes. To facilitate disease‐specific and cross‐sector analyses, we outline a practical approach to categorize forms of incomplete treatment, present distinct semantic categories with case examples and provide an algorithm that could be tailored to disease‐ and context‐specific needs. Pediatr Blood Cancer 2015;62:565–570. © 2015 Wiley Periodicals, Inc.  相似文献   
48.
49.
Ecotoxicology - Azadirachtin is a biorational insecticide commonly reported as selective to a range of beneficial insects. Nonetheless, only few studies have been carried out with pollinators,...  相似文献   
50.
Clinical Rheumatology - To compare long-term clinical, immunological, and radiographic outcomes between five sets of remission criteria (four clinical and one ultrasound (US)-based) in a cohort of...  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