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   15102篇
  免费   880篇
  国内免费   101篇
耳鼻咽喉   153篇
儿科学   292篇
妇产科学   161篇
基础医学   2117篇
口腔科学   217篇
临床医学   1542篇
内科学   3762篇
皮肤病学   329篇
神经病学   1812篇
特种医学   986篇
外科学   2292篇
综合类   74篇
一般理论   7篇
预防医学   618篇
眼科学   225篇
药学   749篇
中国医学   7篇
肿瘤学   740篇
  2023年   140篇
  2022年   178篇
  2021年   403篇
  2020年   242篇
  2019年   326篇
  2018年   372篇
  2017年   266篇
  2016年   387篇
  2015年   385篇
  2014年   553篇
  2013年   759篇
  2012年   1200篇
  2011年   1184篇
  2010年   735篇
  2009年   692篇
  2008年   1072篇
  2007年   1061篇
  2006年   1015篇
  2005年   1003篇
  2004年   898篇
  2003年   793篇
  2002年   719篇
  2001年   158篇
  2000年   119篇
  1999年   145篇
  1998年   153篇
  1997年   131篇
  1996年   77篇
  1995年   75篇
  1994年   55篇
  1993年   45篇
  1992年   51篇
  1991年   42篇
  1990年   52篇
  1989年   37篇
  1988年   25篇
  1987年   29篇
  1986年   27篇
  1985年   20篇
  1984年   26篇
  1983年   23篇
  1982年   22篇
  1980年   15篇
  1979年   16篇
  1978年   15篇
  1977年   22篇
  1975年   18篇
  1974年   20篇
  1973年   15篇
  1930年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
OBJECTIVE: The study's objective was to test the tolerability and efficacy of the endogenous antiseptic N-chlorotaurine (NCT) in comparison with a standard clinical treatment according to a phase IIb clinical trial protocol. STUDY DESIGN: The antimicrobial agent NCT was compared with the antibiotic component drops Otosporin (containing neomycin, polymyxin B, and hydrocortisone) for topical treatment of acute otitis externa in a randomized and rater-blinded clinical study. METHODS: Fifty patients suffering from acute otitis externa were divided into two groups according to a randomized list. The test group was treated with 1 mL of 1% aqueous NCT solution, the reference group with 1 mL of Otosporin. The substances were applied to the external ear canal at one daily session until the signs of infection disappeared. Efficacy and tolerability were evaluated daily by visual analogue scale and a six-step infection score. In addition, smears were analyzed to identify the causative pathogens. RESULTS: Both medications were equally well tolerated by the patients. The treatment was successful for all patients of the NCT group, whereas in one patient from the reference group, the infection did not disappear. The inflammation score improved more rapidly in the NCT group, which resulted in an earlier termination of the therapy. This difference became highly significant on days 4 to 7 (P <.01 each). Time needed for disappearance of inflammation (score 0) was 5.6 +/- 1.6 (mean +/- SD, range 3-9) days in the NCT group and 7.4 +/- 1.6 (range 4-10) days in the Otosporin group (P <.001). As expected, microbiologic cultures from ear swabs revealed Pseudomonas aeruginosa (58%) followed by Staphylococcus aureus (18%) as the main causative pathogens. CONCLUSIONS: NCT appears to be well tolerated and more effective than the therapy using antibiotic component drops. Because of its endogenous nature and its higher efficacy, NCT appears to be a good choice for topical treatment of acute otitis externa.  相似文献   
972.
OBJECTIVE: We tested if fetal pulse oximetry in addition to electronic fetal monitoring (CTG) and scalp blood sampling improves the accuracy of fetal assessment and allows safe reduction of operative deliveries (-50%) and scalp blood sampling (-50%) performed because of nonreassuring fetal status.Study design A randomized controlled trial was conducted in 146 patients with term pregnancies in active labor and abnormal fetal heart rate patterns: 73 had electronic fetal heart rate monitoring (CTG) and fetal scalp blood sampling (control group), 73 had CTG, fetal scalp blood sampling, and continuous fetal pulse oximetry (study group). RESULTS: There was a reduction of -50% in operative deliveries and fetal scalp blood sampling performed because of nonreassuring fetal status in the study group: operative deliveries, study versus control 25/49 (P 相似文献   
973.
Hemisphere asymmetry was explored in normal healthy subjects and in patients with schizophrenia using a novel voxel-based tensor analysis applied to fractional anisotropy (FA) of the diffusion tensor. Our voxel-based approach, which requires precise spatial normalization to remove the misalignment of fiber tracts, includes generating a symmetrical group average template of the diffusion tensor by applying nonlinear elastic warping of the demons algorithm. We then normalized all 32 diffusion tensor MRIs from healthy subjects and 23 from schizophrenic subjects to the symmetrical average template. For each brain, six channels of tensor component images and one T2-weighted image were used for registration to match tensor orientation and shape between images. A statistical evaluation of white matter asymmetry was then conducted on the normalized FA images and their flipped images. In controls, we found left-higher-than-right anisotropic asymmetry in the anterior part of the corpus callosum, cingulum bundle, the optic radiation, and the superior cerebellar peduncle, and right-higher-than-left anisotropic asymmetry in the anterior limb of the internal capsule and the anterior limb's prefrontal regions, in the uncinate fasciculus, and in the superior longitudinal fasciculus. In patients, the asymmetry was lower, although still present, in the cingulum bundle and the anterior corpus callosum, and not found in the anterior limb of the internal capsule, the uncinate fasciculus, and the superior cerebellar peduncle compared to healthy subjects. These findings of anisotropic asymmetry pattern differences between healthy controls and patients with schizophrenia are likely related to neurodevelopmental abnormalities in schizophrenia.  相似文献   
974.
BACKGROUND: Heat shock protein 70 (Hsp70) is essential for cellular recovery, survival and maintenance of cellular function. Research into the possible use of Hsp70 as a cytoprotective therapeutic agent is ongoing. Chronic heart failure (CHF) is a state associated with systemic inflammation, particularly in patients with cardiac cachexia. We hypothesised that circulating Hsp70 levels are elevated in patients with CHF, more so in cachechtic patients, and that Hsp70 levels would relate to mortality. METHODS AND RESULTS: We studied 107 patients (28 female, age 67+/-1 years, NYHA class 2.6+/-0.6 and LVEF 29+/-1%, mean+/-SEM) and 21 controls. Cardiac cachexia was present in 32 patients. Hsp70 was detectable in 41% of CHF patients and in only 10% of controls. Overall serum levels were significantly higher in CHF patients vs. controls (7.13+/-1.34 vs. 0.38+/-0.26 ng/ml, p=0.004). Hsp70 levels were also higher in patients with advanced CHF according to NYHA class or the presence of cachexia (all p<0.05). There was no relation between Hsp70 and left ventricular ejection fraction, maximal oxygen consumption and several inflammatory cytokines (all p>0.05). During a median follow-up of 208 days (range 4-2745 days) 38 patients died. Cox proportional hazards analysis showed that increased Hsp70 did not predict survival (p=0.17). CONCLUSION: Hsp70 levels are elevated in CHF patients, particularly in those with cardiac cachexia and Hsp70 relates to disease severity but not to survival. The significance of the relationship of Hsp70 expression and morbidity in CHF needs further evaluation.  相似文献   
975.
BACKGROUND: Lumbar facet nerve (medial branch) block for pain relief in facet syndrome is currently performed under fluoroscopic or computed tomography scan guidance. In this three-part study, the authors developed a new ultrasound-guided methodology, described the necessary landmarks and views, assessed ultrasound-derived distances, and tested the clinical feasibility. METHODS: (1) A paravertebral cross-axis view and long-axis view were defined under high-resolution ultrasound (15 MHz). Three needles were guided to the target point at L3-L5 in a fresh, nonembalmed cadaver under ultrasound (2-6 MHz) and were subsequently traced by means of dissection. (2) The lumbar regions of 20 volunteers (9 women, 11 men; median age, 36 yr [23-67 yr]; median body mass index, 23 kg/m2 [19-36 kg/m2]) were studied with ultrasound (3.5 MHz) to assess visibility of landmarks and relevant distances at L3-L5 in a total of 240 views. (3) Twenty-eight ultrasound-guided blocks were performed in five patients (two women, three men; median age, 51 yr [31-68 yr]) and controlled under fluoroscopy. RESULTS: In the cadaver, needle positions were correct as revealed by dissection at all three levels. In the volunteers, ultrasound landmarks were delineated as good in 19 and of sufficient quality in one (body mass index, 36 kg/m2). Skin-target distances increased from L3 to L5, reaching statistical significance (*, **P < 0.05) between these levels on both sides: L3r, 45+/-6 mm*; L4r, 48+/-7 mm; L5r, 50+/-6 mm*; L3l, 44+/-5 mm**; L4l, 47+/-6 mm; L5l, 50+/-6 mm**. In patients, 25 of 28 ultrasound-guided needles were placed accurately, with the remaining three closer than 5 mm to the radiologically defined target point. CONCLUSION: Ultrasound guidance seems to be a promising new technique with clinical relevance and the potential to increase practicability while avoiding radiation in lumbar facet nerve block.  相似文献   
976.
977.
978.
RATIONALE AND OBJECTIVES: Both single-shot diffusion-weighted echo-planar imaging (EPI) and line scan diffusion imaging (LSDI) can be used to obtain magnetic resonance diffusion tensor data and to calculate directionally invariant diffusion anisotropy indices, ie, indirect measures of the organization and coherence of white matter fibers in the brain. To date, there has been no comparison of EPI and LSDI. Because EPI is the most commonly used technique for acquiring diffusion tensor data, it is important to understand the limitations and advantages of LSDI relative to EPI. MATERIALS AND METHODS: Five healthy volunteers underwent EPI and LSDI diffusion on a 1.5 Tesla magnet (General Electric Medical Systems, Milwaukee, WI). Four-mm thick coronal sections, covering the entire brain, were obtained. In addition, one subject was tested with both sequences over four sessions. For each image voxel, eigenvectors and eigenvalues of the diffusion tensor were calculated, and fractional anisotropy (FA) was derived. Several regions of interest were delineated, and for each, mean FA and estimated mean standard deviation were calculated and compared. RESULTS: Results showed no significant differences between EPI and LSDI for mean FA for the five subjects. When intersession reproducibility for one subject was evaluated, there was a significant difference between EPI and LSDI in FA for the corpus callosum and the right uncinate fasciculus. Moreover, errors associated with each FA measure were larger for EPI than for LSDI. CONCLUSION: Results indicate that both EPI- and LSDI-derived FA measures are sufficiently robust. However, when higher accuracy is needed, LSDI provides smaller error and smaller inter-subject and inter-session variability than EPI.  相似文献   
979.
Tsui BC  Malherbe S  Koller J  Aronyk K 《Anesthesia and analgesia》2004,98(2):434-6, table of contents
In this case report, we describe the use of cerebrospinal fluid lavage as a successful treatment of an inadvertent intrathecally placed epidural catheter in a 14-yr-old girl who underwent a combination of epidural anesthesia and general anesthesia for orthopedic surgery. In this case, a large amount of local anesthetic was injected (the total possible intrathecal injection was 200 mg of lidocaine and 61 mg of bupivacaine), resulting in apnea and fixed dilated pupils in the patient at the end of surgery. Twenty milliliters of cerebrospinal fluid was replaced with 10 mL of normal saline and 10 mL of lactated Ringer's solution from the "epidural" catheter. Spontaneous respiration returned 5 min later, and the patient was tracheally extubated after 30 min. No signs of neurological deficit or postdural puncture headache were noted after surgery. IMPLICATIONS: Cerebrospinal lavage may be a helpful adjunct to the conventional supportive management of patients in the event of an inadvertent total spinal.  相似文献   
980.
Marsch SC  Sluga M  Studer W  Barandun J  Scharplatz D  Ummenhofer W 《Anesthesia and analgesia》2004,98(6):1789-93, table of contents
In this randomized prospective double-blind study we tested the hypothesis that compared with 40 mL chloroprocaine 0.5%, 40 mL chloroprocaine 1% results in an earlier onset to analgesia duration and improves distal tourniquet tolerance in 150 patients undergoing forearm surgery under IV regional anesthesia using a double-cuff technique, switching from the proximal to the distal cuff was performed if pain scores increased above 4 of 10. Switching to the distal cuff resulted in pain scores below 4 in 69% of patients in the 0.5% group and in 88% of patients in the 1% group (P = 0.047). In addition, both groups differed in the sustained effect on distal tourniquet pain (P = 0.020). Time between injection and onset to analgesia duration was 13 +/- 1 min in the 0.5% group and 11 +/- 1 min in the 1% group (P = 0.0006). On release of the tourniquet, signs of systemic local anesthetic toxicity occurred in 6 patients of the 0.5% group and 28 of the 1% group (P < 0.0001). We conclude that chloroprocaine 1% resulted in an earlier onset of analgesia and improved distal tourniquet tolerance. However, these beneficial effects must be weighed against a fourfold increase in side effects. IMPLICATIONS: Compared to a standard dose of 40 mL 0.5% chloroprocaine, 40 mL 1% chloroprocaine resulted in an earlier onset of analgesia duration and improved distal tourniquet tolerance during IV regional anesthesia. These beneficial effects must be weighed against a fourfold increase in signs of systemic local anesthetic toxicity.  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