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   7585篇
  免费   347篇
  国内免费   43篇
耳鼻咽喉   75篇
儿科学   150篇
妇产科学   94篇
基础医学   1285篇
口腔科学   111篇
临床医学   672篇
内科学   1934篇
皮肤病学   104篇
神经病学   653篇
特种医学   217篇
外科学   988篇
综合类   38篇
一般理论   3篇
预防医学   435篇
眼科学   42篇
药学   565篇
中国医学   8篇
肿瘤学   601篇
  2023年   13篇
  2022年   19篇
  2021年   80篇
  2020年   40篇
  2019年   61篇
  2018年   76篇
  2017年   51篇
  2016年   63篇
  2015年   116篇
  2014年   145篇
  2013年   217篇
  2012年   462篇
  2011年   484篇
  2010年   246篇
  2009年   269篇
  2008年   475篇
  2007年   542篇
  2006年   589篇
  2005年   649篇
  2004年   602篇
  2003年   625篇
  2002年   539篇
  2001年   99篇
  2000年   66篇
  1999年   97篇
  1998年   157篇
  1997年   118篇
  1996年   102篇
  1995年   94篇
  1994年   116篇
  1993年   85篇
  1992年   65篇
  1991年   58篇
  1990年   64篇
  1989年   39篇
  1988年   39篇
  1987年   45篇
  1986年   41篇
  1985年   39篇
  1984年   30篇
  1983年   20篇
  1982年   43篇
  1981年   45篇
  1980年   34篇
  1979年   13篇
  1978年   23篇
  1977年   15篇
  1976年   10篇
  1973年   10篇
  1969年   7篇
排序方式: 共有7975条查询结果,搜索用时 93 毫秒
11.
背景:儿童和青少年超重和肥胖正迅速增加。在该人群,单纯行为疗法减肥及维持体重下降的效果有限,但是对药物治疗尚未进行广泛的研究。 目的:确定奥利州他(Orlistat)在青少年体重治疗方面的效果及其安个性。 设计、地点和病例:于美国和加拿大32个中心、539例肥胖青少年(12—16岁;体重指数[body mass index,BMI]在第95百分化之上≥2单位)进行的多ln0、54剧(2000年8月至2002年10月)随机双盲研究。 干预:给予奥利司他(n=357)或安慰剂(n=182)120mg,每口3次,持续1年;加适度低热卡饮食(脂肪占30%)、运动和行为治疗。 主要观察指标:BMI变化;二级指标包括腰围和髋用、体重下降、脂质测量以及机体对口服葡萄糖的血糖和胰岛素反心。 结果:至12周时,两组BMI均有下降;此后,奥利司他组体重维持稳定而安慰剂组则超过基线。研究结束时,奥利司他组BMI下降0.55。而安慰剂组则增加0.31(P=0.001)。与安慰剂组的15.7%相比,奥利司他组26.5%的病例BMI下降≥5%(P=0.005);BMI下降≥10%者分别为4.5%和13.3%(P=0.002)。在研究结束时,奥利司他组体重增加0.53kg,安慰剂组增加3.14kg(P〈0.001)。双能X线吸收测量娃示,这种差异可用脂肪体再的变化解释。奥利司他组腰围下降,安慰剂组腰围上升(-1.33cm比+0.12cm;P〈0.05)。奥利司他组发生轻至中度胃肠道不良事件者为9%-50%,安慰剂组为1%~13%。 结论:与安慰剂比较,奥利司他与饮食、运动和行为改善联合可显著改善肥胖青少年体重的治疗。在这个青少年人群,连续使用奥利司他1年并无重要安全问题,尽管奥利司他组胃肠道不良事件较为常见。  相似文献   
12.
In a prospective study of the effect of postoperative radiation therapy for the prevention of reproliferation of membranes and recurrent proliferative vitreoretinopathy (PVR) two similar groups of patients with retinal detachment and PVR grade D1 to D3 in one eye were compared. Half the eyes (30) received a total dose of 3000 cGy after surgery; the other half remained untreated. After a followup of 6 months and 14 months or more (maximum 36 months) the anatomical and functional results of each group were compared. After 6 months in the unirradiated group 57% (17/30) remained attached and 43% (13/30) had detached again. In the irradiated group 63% (19/30) were attached and 37% (11/30) had detached. However, there was no statistically significant difference between the two groups (P=0.479, Fisher's Exact Test). After 14 months the number of cured and uncured eyes remained the same in the unirradiated group, while in four of the eyes in the irradiated group a later onset of reproliferation and detachment occurred (after 7, 8, 12 and 14 months, respectively). A final cure rate of 57% (17/30) was achieved in the unirradiated group and a 50% (15/30) cure rate in the irradiated group. Thus the failure rate was 43% (13/30) in the unirradiated group and 50% (15/30) in the irradiated group (P=0.473, Fisher's Exact Test). No side effects from the radiation were observed in any case and no radiation retinopathy occurred during an observation period of up to 3 years. The visual acuity of the cured treated and cured untreated eyes was similar in the two groups. From these results we conclude that immediate radiation treatment does not improve the long-term results and does not reduce the number of reoperations. In a considerable number of treated eyes the onset of reproliferation was delayed from 7 to 14 months, whereas in the untreated group reproliferation was always observed during the first 6 months. A combination of various antiproliferative and antiinflammatory therapies are needed to suppress recurrent PVR after succesful vitreoretinal surgery and to minimize the side effects of these treatments.Presented in part at the XVIIth Meeting of the Club Jules Gonin, 1–6 September 1990, Lausanne  相似文献   
13.
14.
15.
16.
BACKGROUND: Conventional and atypical antipsychotics have different affinities for D2 receptors, and these receptors are principally located in the striatum. Given that this cerebral structure was previously found to play a major role in procedural learning, the antipsychotic treatment in schizophrenia may be determinant for the procedural learning profile of these patients. OBJECTIVE: The current study was aimed at verifying whether procedural learning differs in patients with schizophrenia treated with conventional antipsychotics and patients treated with atypical antipsychotics. METHOD: Forty-five patients with schizophrenia were divided into 3 different groups according to their pharmacologic treatment: (1) haloperidol, a classical neuroleptic with high D2 receptor affinity; (2) clozapine, an atypical neuroleptic with practically no D2 receptor affinity; and (3) risperidone, an atypical neuroleptic that nevertheless shows high D2 receptor affinity. Patients were compared to 35 control subjects on a visuomotor procedural learning task (mirror drawing). RESULTS: All patients were able to learn the task. However, those treated with haloperidol showed some degree of learning impairment, while those treated with clozapine or risperidone did not show this impairment. In addition, performance per se, regardless of the learning, was found to be affected in the haloperidol and risperidone, but not in the clozapine groups. CONCLUSION: Procedural learning in schizophrenia may be differentially affected, depending on the pharmacologic profiles of the antipsychotics used for the treatment of this illness.  相似文献   
17.
18.
Ferroquine (SSR97193) has been shown to be a promising antimalarial, both on laboratory clones and on field isolates. So far, no resistance was documented in Plasmodium falciparum. In the present work, the metabolic pathway of ferroquine, based on experiments using animal and human hepatic models, is proposed. Ferroquine is metabolized mainly via an oxidative pathway into the major metabolite mono-N-demethyl ferroquine and then into di-N,N-demethyl ferroquine. Some other minor metabolic pathways were also identified. Cytochrome P450 isoforms 2C9, 2C19, and 3A4 and, possibly in some patients, isoform 2D6, are mainly involved in ferroquine oxidation. The metabolites were synthesized and tested against the 3D7 (chloroquine-sensitive) and W2 (chloroquine-resistant) P. falciparum strains. According to the results, the activity of the two main metabolites decreased compared with that of ferroquine; however, the activity of the mono-N-demethyl derivative is significantly higher than that of chloroquine on both strains, and the di-N-demethyl derivative remains more active than chloroquine on the chloroquine-resistant strain. These results further support the potential use of ferroquine against human malaria.  相似文献   
19.
Transcutaneous oximetry has been used to define the level of amputation in arteritic patients, with discrepant results. We have studied preoperative statix oximetry in 33 arteritic patients at the Leriche-Fontaine Stage IV, who underwent 36 amputations (thighs = 6, Legs+Symes = 14, transmetatarsal = 7, toes = 9). Oximetry included the measurement, at the level of amputation, of the transcutaneous partial oxygen pressure (tc pO2), of the tissue oxygenation ratio (TOR), preferably with a precordial electrode, of the tc pO2 gain after oxygen inhalation and of the gain ratio with the reference electrode. Two patients died postoperatively, the amputation stump did not heal in another 8 patients. The tc pO2 value was 36.6 +/- 16.2 mm Hg in the healed group and 21.1 +/- 19.9 mm Hg in the non healed group. The TOR respectively was 71.2 +/- 32.7% and 38.6 +/- 29.9% in these two groups. These differences were statistically significant. The difference between the two groups in the measurements made after the oxygenation test was not statistically significant. With a tc pO2 threshold at 26 mm Hg, the sensitivity was 73% and the specificity 75%, the positive predictive value 90%, the negative predictive value 46% and the value of the test 73.5%. The thresholds calculated to be 56% for TOR, 11 mm Hg for the gain and 32% for the gain ratio, did not improve the performances of oximetry. In our study, the tc pO2 was the parameter that best allowed predicting healing was obtained with smaller values than the threshold. Other elements such as the general condition and diabetes have played a role in the prognosis.  相似文献   
20.
Background: Percutaneous coronary intervention (PCI) is performed in patients with coronary artery disease who are undergoing major noncardiac procedures to reduce perioperative cardiac morbidity and mortality. However, the impact of this approach on postoperative outcome remains controversial.

Methods: The authors analyzed a cohort of 1,152 patients after abdominal aortic surgery in which 78 patients underwent PCI. A propensity score analysis was performed. Also, using a logistic regression model, the authors determined variables associated with a severe postoperative coronary event or a death in patients without PCI. Then, in patients with PCI, they compared the expected and observed outcome.

Results: Five variables (age > 75 yr, blood transfusion > 3 units, repeated surgery, preoperative hemodialysis, and previous cardiac failure) independently predicted (with 94% correctly classified) a severe postoperative coronary event, and five variables (age > 75 yr, repeated surgery, previously abnormal ST segment/T waves, previous hypertension, and previous cardiac failure) independently predicted (with 97% correctly classified) postoperative death. In the PCI group, the observed percentages of patients with a severe postoperative coronary event (9.0% [95% confidence interval, 4.4-17.4]) or death (5.1% [95% confidence interval, 2.0-12.5]) were not significantly different from the expected percentages (8.2 and 6.9%, respectively). When all patients were pooled together, the odds ratios of PCI were not significant. The propensity score analysis provided a similar conclusion.  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