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   23604篇
  免费   1802篇
  国内免费   96篇
耳鼻咽喉   259篇
儿科学   446篇
妇产科学   277篇
基础医学   3235篇
口腔科学   444篇
临床医学   2967篇
内科学   5366篇
皮肤病学   447篇
神经病学   2334篇
特种医学   728篇
外国民族医学   3篇
外科学   3446篇
综合类   243篇
现状与发展   1篇
一般理论   10篇
预防医学   1570篇
眼科学   374篇
药学   1547篇
中国医学   68篇
肿瘤学   1737篇
  2023年   145篇
  2022年   321篇
  2021年   566篇
  2020年   385篇
  2019年   606篇
  2018年   695篇
  2017年   507篇
  2016年   535篇
  2015年   655篇
  2014年   839篇
  2013年   1116篇
  2012年   1787篇
  2011年   1956篇
  2010年   940篇
  2009年   898篇
  2008年   1476篇
  2007年   1488篇
  2006年   1386篇
  2005年   1415篇
  2004年   1271篇
  2003年   1129篇
  2002年   1153篇
  2001年   278篇
  2000年   249篇
  1999年   278篇
  1998年   232篇
  1997年   191篇
  1996年   134篇
  1995年   135篇
  1994年   104篇
  1993年   104篇
  1992年   183篇
  1991年   168篇
  1990年   151篇
  1989年   138篇
  1988年   142篇
  1987年   137篇
  1986年   142篇
  1985年   145篇
  1984年   116篇
  1983年   97篇
  1982年   101篇
  1981年   98篇
  1980年   83篇
  1979年   78篇
  1978年   72篇
  1977年   65篇
  1976年   51篇
  1975年   47篇
  1974年   48篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The MIC of pefloxacin against all the strains (3122) isolated in an intensive care unit during 18 months was studied. The MIC of pefloxacin was estimated by standard agar diffusion method in Mueller-Hinton agar. All the strains with a MIC lower than 2 mg/l were considered as sensitive, between 2 and 4 mg/l as "intermediary" and over 4 mg/l as resistant. Geometrical means of MICs were calculated for each month and for different species. The study continued for 18 months from the introduction of the drug which was in widespread and constant use as a first-choice antibiotic. No significant increase was detected in the incidence of resistant strains during the study; on the other hand, small, limited clusters of resistant strains were observed during minor nosocomial epidemics. The general features of quinolone activity, the spectrum of this new quinolone and the slow evolution of the bacterial population are discussed.  相似文献   
102.
Anti-acetylcholine receptor (AChR) antibody was undetectable in 26/153 (17%) sera from myasthenia gravis patients assayed by standard RIA using human acetylcholine receptor. Eight of these were found to be positive with a modified protocol using a mixture of normal and denervated AChR, reducing the proportion of "negative" sera to 12%. Many of these were from patients with a short history; two such patients later developed low positive values. Anti-AChR without clinical evidence of myasthenia was found in one of three monozygotic twins of myasthenia gravis patients, and in one of thirty other first degree relatives of a further 17 patients. Anti-AChR is a valuable and highly specific diagnostic test which, with the assay used here, is positive in about 88% of patients with clinical features of myasthenia gravis.  相似文献   
103.
Resorbable suture support for ventricular aneurysmectomy   总被引:1,自引:0,他引:1  
The edge of tissue left after ventricular aneurysmectomy requires very careful placement and tying of the sutures. The use of Teflon felt as a support appears to redistribute the pressure and thus prevent the sutures from cutting through the vulnerable tissue. In many cases, Teflon felt reinforcement is preferred to direct unsupported closure because of perioperative of immediately postoperative bleeding complications. However, the unavoidable full immobilization of the sutured area, the possible risk of foreign body infection, and the extensive adhesions and calcification in the long term compelled us to search for a better alternative, combining the convenience of both methods and limiting the risks. PDS (polydioxine) resorbable pledgets and strips, provided by Ethicon GmbH, were used as a suture support during the past 2 years for closure of 29 ventricular aneurysmectomies and four ischemic ventricular septal defects, all except one in combination with coronary bypass grafting. The PDS material was easy and efficient to apply and caused no complications during and after the operation. In one case, we had the opportunity to review the supported scar during a second operation for new coronary grafts after 18 months. The formerly feared "linear scar petrification," usual after use of Teflon felt, was absent. The scar was free from difficult adhesions. Our initial experience suggests the further extensive use of this resorbable material as a support for various sutures at risk.  相似文献   
104.
35 ANUG patients were examined and compared clinically and demographically. Plaque removed from ulcerated sites in 20 patients was cultured using quantitative anaerobic procedures and examined by electron and darkfield microscopy. Patients were classified as having ANUG when presenting with ulceration and necrosis of interproximal papillae, pain and bleeding. The clinical symptoms of fetid odor, pseudomembrane formation, lymphadenopathy and elevated body temperature were present in 97%, 85%, 61% and 39% of the ANUG patients, respectively. 83% of the patients were smokers. The ANUG patients demonstrated a lower average age (24 years) than the general clinic population (32 years). There was a slightly higher % of male (54%) than female (46%) and the % of Caucasian (51%) and black (49%) ANUG patients were almost equal. Cultural studies revealed that gram-negative rods were the predominant cultivable micro-organisms present in the plaque, representing 78.2% of the total recoverable count. Of these, nearly half were strict anaerobes with Bacteroides gingivalis and Fusobacterium nucleatum accounting for 7.8% and 3.4%, respectively. Anaerobic and facultative gram-positive cocci (15.5%), gram-negative cocci (3.5%) and gram-positive rods (2.8%) were also isolated. Microscopic analysis of the morphologic composition of plaque revealed that rods (43%) constituted the greatest % of the total microorganisms observed followed by spirochetes (30%) and cocci (27%). 8 distinct types of spirochetal periplasmic flagellar arrangement were observed by electron microscopy, the "2-4-2" periplasmic flagellar arrangement being most numerous.  相似文献   
105.
From July 1979 to December 1985 we observed 51 patients with traumatic lesions of the descending thoracic aorta. Twenty-nine had acute ruptures, mostly accompanied by multiple injuries, and 27 had to be operated upon immediately. Twenty-two patients (19 males, 3 females) had chronic traumatic aneurysms of the descending thoracic aorta (more than six weeks after trauma). Mean age at the time of trauma was 24 years. Mean age at time of surgery was 36.5 years. Twelve patients were symptomatic. All were treated surgically. At surgery, complete aortic disruption was found in 15 patients and partial rupture in seven. We did not use aortic shunting of any kind, only aortic cross-clamping. Hypertension was controlled by intravenous drug infusion. The ruptured aortic segment was replaced in all cases by prosthetic Dacron graft. There were no operative deaths. One patient (age 77) died 11 weeks after surgery from multiple organ failure. One case of postoperative paraplegia was observed. This patient recovered almost completely from his neurological deficit.  相似文献   
106.
Summary Twenty-six adult patients with astrocytomas were treated with BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) 180–240 mg/m2 1.V. every 6–9 weeks, with metronidazole 1.5 g/m2 p. o. 12 h and 1 h before BCNU and again 6 h and 24 h after BCNU. Of twenty-two evaluable patients, 9 (41%) responded with evidence of reduced tumor size on CT scan, 3 (14%) stabilized and 10 (45%) failed. Patients with no prior chemotherapy or radiotherapy, good performance. status, low grade tumors, and age 50 years had the highest response rates, although differences were not statistically significant. Median survival and duration of response have not been reached with a median follow-up time of ten months. Hematological toxicity was dose-limiting and was probably not augmented by the metronidazole. There was one death from infection that was possibly drug-related. Gastrointestinal toxicity was substantial, and was probably increased by the metronidazole.While the combination of BCNU and metronidazole were tolerable, the response rate seen was no higher than that noted for BCNU alone, and further studies using this dose-schedule are not recommended in astrocytomas.Presented at the 13th International Congress of Chemotherapy, Vienna Austria, August 1983.  相似文献   
107.
108.
Background

Accurate accelerometer-based methods are required for assessment of 24-h physical behavior in young children. We aimed to summarize evidence on measurement properties of accelerometer-based methods for assessing 24-h physical behavior in young children.

Methods

We searched PubMed (MEDLINE) up to June 2021 for studies evaluating reliability or validity of accelerometer-based methods for assessing physical activity (PA), sedentary behavior (SB), or sleep in 0–5-year-olds. Studies using a subjective comparison measure or an accelerometer-based device that did not directly output time series data were excluded. We developed a Checklist for Assessing the Methodological Quality of studies using Accelerometer-based Methods (CAMQAM) inspired by COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN).

Results

Sixty-two studies were included, examining conventional cut-point-based methods or multi-parameter methods. For infants (0—12 months), several multi-parameter methods proved valid for classifying SB and PA. From three months of age, methods were valid for identifying sleep. In toddlers (1—3 years), cut-points appeared valid for distinguishing SB and light PA (LPA) from moderate-to-vigorous PA (MVPA). One multi-parameter method distinguished toddler specific SB. For sleep, no studies were found in toddlers. In preschoolers (3—5 years), valid hip and wrist cut-points for assessing SB, LPA, MVPA, and wrist cut-points for sleep were identified. Several multi-parameter methods proved valid for identifying SB, LPA, and MVPA, and sleep.

Despite promising results of multi-parameter methods, few models were open-source. While most studies used a single device or axis to measure physical behavior, more promising results were found when combining data derived from different sensor placements or multiple axes.

Conclusions

Up to age three, valid cut-points to assess 24-h physical behavior were lacking, while multi-parameter methods proved valid for distinguishing some waking behaviors. For preschoolers, valid cut-points and algorithms were identified for all physical behaviors. Overall, we recommend more high-quality studies evaluating 24-h accelerometer data from multiple sensor placements and axes for physical behavior assessment. Standardized protocols focusing on including well-defined physical behaviors in different settings representative for children’s developmental stage are required. Using our CAMQAM checklist may further improve methodological study quality.

PROSPERO Registration number

CRD42020184751.

  相似文献   
109.
High-risk combinations of recipient and graft characteristics are poorly defined for liver retransplantation (reLT) in the current era. We aimed to develop a risk model for survival after reLT using data from the European Liver Transplantation Registry, followed by internal and external validation. From 2006 to 2016, 85 067 liver transplants were recorded, including 5581 reLTs (6.6%). The final model included seven predictors of graft survival: recipient age, model for end-stage liver disease score, indication for reLT, recipient hospitalization, time between primary liver transplantation and reLT, donor age, and cold ischemia time. By assigning points to each variable in proportion to their hazard ratio, a simplified risk score was created ranging 0–10. Low-risk (0–3), medium-risk (4–5), and high-risk (6–10) groups were identified with significantly different 5-year survival rates ranging 56.9% (95% CI 52.8–60.7%), 46.3% (95% CI 41.1–51.4%), and 32.1% (95% CI 23.5–41.0%), respectively (< 0.001). External validation showed that the expected survival rates were closely aligned with the observed mortality probabilities. The Retransplantation Risk Score identifies high-risk combinations of recipient- and graft-related factors prognostic for long-term graft survival after reLT. This tool may serve as a guidance for clinical decision-making on liver acceptance for reLT.  相似文献   
110.
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