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   13160篇
  免费   1263篇
  国内免费   40篇
耳鼻咽喉   178篇
儿科学   368篇
妇产科学   331篇
基础医学   1814篇
口腔科学   752篇
临床医学   1133篇
内科学   3054篇
皮肤病学   286篇
神经病学   1131篇
特种医学   509篇
外科学   1891篇
综合类   84篇
一般理论   5篇
预防医学   1071篇
眼科学   241篇
药学   718篇
中国医学   41篇
肿瘤学   856篇
  2023年   55篇
  2022年   81篇
  2021年   308篇
  2020年   232篇
  2019年   370篇
  2018年   464篇
  2017年   342篇
  2016年   368篇
  2015年   402篇
  2014年   506篇
  2013年   603篇
  2012年   865篇
  2011年   833篇
  2010年   554篇
  2009年   449篇
  2008年   668篇
  2007年   749篇
  2006年   645篇
  2005年   616篇
  2004年   524篇
  2003年   477篇
  2002年   417篇
  2001年   346篇
  2000年   316篇
  1999年   332篇
  1998年   112篇
  1997年   112篇
  1996年   87篇
  1995年   92篇
  1994年   90篇
  1993年   88篇
  1992年   229篇
  1991年   208篇
  1990年   174篇
  1989年   197篇
  1988年   167篇
  1987年   146篇
  1986年   155篇
  1985年   151篇
  1984年   109篇
  1983年   89篇
  1982年   49篇
  1981年   55篇
  1979年   70篇
  1978年   59篇
  1976年   45篇
  1975年   50篇
  1974年   40篇
  1973年   54篇
  1972年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.

Background

Hepatic resection has evolved to become safer, thereby making it possible to expand the indications.

Aim

To assess the results from a group of patients presenting these expanded indications.

Method

Were prospectively studied all the hepatectomy procedures performed for hepatic tumor resection. Patients with benign and malignant primary and secondary tumors were included. Were included variables such as age, gender, preoperative diagnosis, preoperative treatment, type of operation performed, need for transfusion, final anatomopathological examination and postoperative evolution. The patients were divided into two groups: group A, with a traditional indication for hepatectomy; and group B, with an expanded indication (tumors in both hepatic lobes, extensive resection encompassing five or more segments, cirrhotic livers and postoperative chemotherapy using hepatotoxic drugs).

Results

Were operated 38 patients, and 40 hepatectomies were performed: 28 patients in group A and 10 in group B. The mean age was 57.7 years, and 25 patients were women. Three in group B were operated as two separate procedures. Groups A and B received means of 1.46 and 5.5 packed red blood cell units per operation, respectively. There were three cases with complications in group A (10.7%) and six in group B (60%). The mortality rate in group A was 3.5% (one patient) and in groups B, 40% (four patients). The imaging examinations were sensitive for the presence of tumors but not for defining the type of tumor. The blood and derivative transfusion rates, morbidity and mortality were greater in the group with expanded indications and more extensive surgery.

Conclusion

The indications for liver biopsy and portal vein embolization or ligature can be expanded, with special need of cooperation of the anesthesiology department and the use of hepatic resection devices to diminish blood transfusion.  相似文献   
92.

OBJECTIVE:

To describe the pathogens found in home nebulizers and in respiratory samples of cystic fibrosis (CF) patients, and to evaluate the effect that a standardized instruction regarding cleaning and disinfection of nebulizers has on the frequency of nebulizer contamination.

METHODS:

We included 40 CF patients (22 males), all of whom used the same model of nebulizer. The median patient age was 11.2 ± 3.74 years. We collected samples from the nebulizer mouthpiece and cup, using a sterile swab moistened with sterile saline. Respiratory samples were collected by asking patients to expectorate into a sterile container or with oropharyngeal swabs after cough stimulation. Cultures were performed on selective media, and bacteria were identified by classical biochemical tests. Patients received oral and written instructions regarding the cleaning and disinfection of nebulizers. All determinations were repeated an average of two months later.

RESULTS:

Contamination of the nebulizer (any part) was detected in 23 cases (57.5%). The nebulizer mouthpiece and cup were found to be contaminated in 16 (40.0%) and 19 (47.5%), respectively. After the standardized instruction had been given, there was a significant decrease in the proportion of contaminated nebulizers (43.5%).

CONCLUSIONS:

In our sample of CF patients, nebulizer contamination was common, indicating the need for improvement in patient practices regarding the cleaning and disinfection of their nebulizers. A one-time educational intervention could have a significant positive impact.  相似文献   
93.
Obesity is linked to the development of cancer. Previous studies have suggested that there is a relationship between bariatric surgery and reduced cancer risk. Data sources were from Medline, Embase, and Cochrane Library. From 951 references, 13 studies met the inclusion criteria (54,257 participants). In controlled studies, bariatric surgery was associated with a reduction in the risk of cancer. The cancer incidence density rate was 1.06 cases per 1000 person-years within the surgery groups. In the meta-regression, we found an inverse relationship between the presurgical body mass index and cancer incidence after surgery (beta coefficient ?0.2, P?相似文献   
94.
The aim of this study was to investigate patterns of cortical atrophy associated with mild cognitive impairment in a large sample of nondemented Parkinson's disease (PD) patients, and its relation with specific neuropsychological deficits. Magnetic resonance imaging (MRI) and neuropsychological assessment were performed in a sample of 90 nondemented PD patients and 32 healthy controls. All underwent a neuropsychological battery including tests that assess different cognitive domains: attention and working memory, executive functions, memory, language, and visuoperceptual‐visuospatial functions. Patients were classified according to their cognitive status as PD patients without mild cognitive impairment (MCI; n = 43) and PD patients with MCI (n = 47). Freesurfer software was used to obtain maps of cortical thickness for group comparisons and correlation with neuropsychological performance. Patients with MCI showed regional cortical thinning in parietotemporal regions, increased global atrophy (global cortical thinning, total gray matter volume reduction, and ventricular enlargement), as well as significant cognitive impairment in memory, executive, and visuospatial and visuoperceptual domains. Correlation analyses showed that all neuropsychological tests were associated with cortical thinning in parietotemporal regions and to a lesser extent in frontal regions. These results provide neuroanatomic support to the concept of MCI classified according to Movement Disorders Society criteria. The posterior pattern of atrophy in temporoparietal regions could be a structural neuroimaging marker of cognitive impairment in nondemented PD patients. All of the neuropsychological tests reflected regional brain atrophy, but no specific patterns were seen corresponding to impairment in distinct cognitive domains. © 2014 International Parkinson and Movement Disorder Society  相似文献   
95.
96.
The persistence of proliferative cells, which could correspond to progenitor populations or potential cells of origin for tumors, has been extensively studied in the adult mammalian forebrain, including human and nonhuman primates. Proliferating cells have been found along the entire ventricular system, including around the central canal, of rodents, but little is known about the primate spinal cord. Here we describe the central canal cellular composition of the Old World primate Macaca fascicularis via scanning and transmission electron microscopy and immunohistochemistry and identify central canal proliferating cells with Ki67 and newly generated cells with bromodeoxyuridine incorporation 3 months after the injection. The central canal is composed of uniciliated, biciliated, and multiciliated ependymal cells, astrocytes, and neurons. Multiciliated ependymal cells show morphological characteristics similar to multiciliated ependymal cells from the lateral ventricles, and uniciliated and biciliated ependymal cells display cilia with large, star‐shaped basal bodies, similar to the Ecc cells described for the rodent central canal. Here we show that ependymal cells with one or two cilia, but not multiciliated ependymal cells, proliferate and give rise to new ependymal cells that presumably remain in the macaque central canal. We found that the infant and adult human spinal cord contains ependymal cell types that resemble those present in the macaque. Interestingly, a wide hypocellular layer formed by bundles of intermediate filaments surrounded the central canal both in the monkey and in the human, being more prominent in the stenosed adult human central canal. J. Comp. Neurol. 522:1800–1817, 2014. © 2013 Wiley Periodicals, Inc.  相似文献   
97.
This study examined the role of inter-organizational collaboration in implementing new evidence-based practices for addressing problem behaviors in at-risk youth. Semi-structured interviews were conducted with 38 systems leaders of probation, mental health, and child welfare departments of 12 California counties participating in a large randomized controlled trial to scale-up the use of Multidimensional Treatment Foster Care. Three sets of collaboration characteristics were identified: (1) characteristics of collaboration process, (2) characteristics of the external environment, and (3) characteristics of participating organizations and individuals. Inter-organizational collaboration enables an exchange of information and advice and a pooling of resources individual agencies may require for successful implementation.  相似文献   
98.

Purpose

The aim of the present study was to test whether the first use of an illicit drug increases the chance of first use of other illicit drugs.

Method

The transitions from the first use of a drug to the first use of another drug were analyzed. Comparisons were made between first drug users and non-users. Survival analysis methods were used to compare the cumulative probability of second drug use after adjusting for socio-demographic covariates and the intermediate use of alcohol and/or tobacco. A total of 12,721 Brazilian university students participated in this study.

Results

Inhalants and marijuana were used prior to the use of several other drugs, whereas the opposite pattern was not found. Ecstasy was used before other drugs in several instances. Other well-examined drugs, such as amphetamines, cocaine and hallucinogens, were used both before and after other illicit drugs without any marked predominance for either of the two roles.

Conclusions

This study supports the role of the use of marijuana and inhalants almost exclusively before the use of other illicit drugs, whereas the use of ecstasy has an opposite role. These roles could be linked to the prevalence of lifetime use and whether individuals were at an earlier or later age during experimentation.  相似文献   
99.
In cases of suspected duodenal ischemia during pancreas transplantation, surgical decisions severely affect the outcome of the patient and the graft. The use of a nontoxic intravenous tracer, indocyanine green, allows the surgeon to evaluate the perfusion of tissues within seconds of injection. Its application to pancreas transplantation has not been reported previously.  相似文献   
100.
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