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   190445篇
  免费   1888篇
  国内免费   91篇
耳鼻咽喉   1313篇
儿科学   7013篇
妇产科学   3379篇
基础医学   18369篇
口腔科学   1861篇
临床医学   13829篇
内科学   34137篇
皮肤病学   877篇
神经病学   18089篇
特种医学   9585篇
外科学   31127篇
综合类   2373篇
一般理论   6篇
预防医学   19110篇
眼科学   3026篇
药学   10279篇
中国医学   657篇
肿瘤学   17394篇
  2023年   204篇
  2022年   298篇
  2021年   536篇
  2020年   406篇
  2019年   498篇
  2018年   22376篇
  2017年   17731篇
  2016年   19962篇
  2015年   1400篇
  2014年   1465篇
  2013年   1603篇
  2012年   8310篇
  2011年   22278篇
  2010年   19460篇
  2009年   12075篇
  2008年   20452篇
  2007年   22636篇
  2006年   1401篇
  2005年   3037篇
  2004年   4130篇
  2003年   4983篇
  2002年   3069篇
  2001年   377篇
  2000年   492篇
  1999年   274篇
  1998年   340篇
  1997年   288篇
  1996年   191篇
  1995年   171篇
  1994年   154篇
  1993年   125篇
  1992年   106篇
  1991年   140篇
  1990年   163篇
  1989年   124篇
  1988年   92篇
  1987年   68篇
  1986年   49篇
  1985年   62篇
  1984年   41篇
  1983年   56篇
  1982年   41篇
  1980年   50篇
  1970年   31篇
  1969年   30篇
  1968年   37篇
  1938年   61篇
  1934年   31篇
  1932年   62篇
  1930年   49篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.

Background  

It has been observed that ras-transformed cell lines in culture have a higher phosphatidylcholine (PC) biosynthesis rate as well as higher PC-degradation rate (increased PC-turnover) than normal cells. In correspondence to these findings, the concentrations of the PC-degradation product lyso-phosphatidylcholine (LPC) in cancer patients were found to be decreased. Our objective was the systematic investigation of the relationship between LPC and inflammatory and nutritional parameters in cancer patients. Therefore, plasma LPC concentrations were assessed in 59 cancer patients and related to nutritional and inflammatory parameters. To determine LPC in blood plasma we developed and validated a HPTLC method.  相似文献   
103.
104.
The depth and extent of the invasion of the skull base by a tumor are the most critical information for successful en bloc resection of the tumor. The only means available for the evaluation of these factors are CT or MRI images. In order to clarify the ability of these imaging modes to delineate the invasion of the skull base, preoperative images of ten patients who underwent en bloc resection of skull base tumors at Kobe University Hospital were compared with the histopathological findings of the resected specimens. CT proved to be superior to MRI for evaluating bone destruction of the skull base. On the other hand, MRI provided more useful information about intracranial invasion than CT. As a hypertrophic linear shadow on Gd-enhanced MRI represented dural invasion or thickened dura mater adjacent to the tumor, this technique should be taken into consideration to determine the dural resection. We concluded that preoperative evaluation of the depth of skull base invasion by both CT and Gd-enhanced MRI is essential for planning complete tumor resection.  相似文献   
105.
106.
Summary To investigate the distribution of possible novel mutations from parkin gene in variant subset of patients with Parkinson’s disease (PD) in China and explore whether parkin gene plays an important role in the pathogenesis of PD, 70 patients were divided into early-onset group and late-onset group; 70 healthy subjects were included as controls. Genomic DNA from 70 normal controls and from those of PD patients were extracted from peripheral blood leukocytes by using standard procedures. Mutations of parkin gene (exon 1–12) in all the subjects were screened by PCR-single strand conformation polymorphism (SSCP), and further sequencing was performed in the samples with abnormal SSCP results, in order to confirm the mutation and its location. A new missense mutation Gly284Arg in a patient and 3 abnormal bands in SSCP electrophoresis from samples of another 3 patients were found. All the DNA variants were sourced from the samples of the patients with early-onset PD. It was concluded that Parkin point mutation also partially contributes to the development of early-onset Parkinson’s disease in Chinese. WANG Tao, male, born in 1961, Associate Professor This work was supported by grants from the key program of the special scientific project of Scientific & Technologic Agency of Hubei Province (Serial No. 2001AA308B01) and the Hygienic Research Project of Hygienic Agency of Hubei province (Serial No. WJ 01529).  相似文献   
107.
Unilateral asterixis developed in a 56 year old man, 5 months after an infarct in the posterior cerebral artery territory, involving the posterolateral nuclear complex of the thalamus, documented by CT-scan and MRI. Unilateral asterixis in rarely reported in association with thalamic lesions and usually develops as an immediate postictal phenomenon. We discuss possible physiopathological mechanisms explaining the occurrence and the delayed onset of these involuntary movements.
Sommario Un uomo di 56 anni ha sviluppato un'asterixis unilaterale, 5 mesi dopo aver presentato un infarto nel territorio dell'arteria cerebrale posteriore, che coinvolgeva i nuclei postero-laterali del talamo, come evidenziato dalla TC e dalla MRI. Asterixis unilaterali si sviluppano raramente in seguito a lesioni vascolari a livello del talamo e generalmente rappresentano un evento immediatamente successivo all'ictus. Nel caso descritto invece, i movimenti involontari si sono manifestati a notevole distanza di tempo. Gli autori discutono i possibili meccanismi fisiopatologici alla base di questi movimenti involontari e della loro insorgenza a distanza di tempo dall'ictus.
  相似文献   
108.
Lymph node (LN) metastases represent the most important negative prognostic factor in squamous cell carcinoma (SCC) of the oral cavity, even though controversies still exist regarding their management. The aim of this study was to retrospectively analyze our experience in surgical management of SCC of the oral cavity with particular focus on the prevalence and localization of lymph nodal metastases and recurrences. The clinical records of 89 consecutive patients treated from 1983 to 2002 by concomitant surgery on both the T and N sites, excluding those undergoing salvage surgery, were reviewed. A total of 119 neck dissections (ND) were performed. Survival outcomes were calculated by the Kaplan–Meier method, while univariate comparisons by the log-rank and non-parametric tests were performed between different groups of patients. Five-year overall and determinate survivals were 50 and 57%, respectively. LN metastases were observed in 52% (56% of these showing extracapsular spread) and their presence strongly correlated with determinate survival (p < 0.0001). The prevalence of clinical and occult nodal disease was not related to the pT status. Neck levels II (59%) and I (56%) were most frequently involved. Metastases to level IV accounted for 15% of positive LN, even though 28% of them turned out to be skip metastases. Five neck recurrences were observed, only one of which was salvaged by surgery. The high prevalence of clinical and occult LN metastases in this setting suggests that ND should be performed on a nearly routine basis, even for lesions with a low-T category and a cN0 neck. Moreover, ND should always encompass level IV due to the possibility of skip metastases, particularly in tumors involving the oral tongue. In patients with a cN+ neck, levels from I to V should be addressed, particularly in the presence of metastases at levels III and IV.  相似文献   
109.
110.
Recently, enormous efforts to measure the quality of healthcare have been made to attain information on ways to improve the quality of healthcare. However, this area of research is still at an early stage of development and more research is required. This article outlines a framework by which the quality of healthcare can be analyzed on the basis of the three quality dimensions introduced by Donabedian. The article then goes on to test the validity of this (theoretical) framework within an empirical analysis.Because of increasing financial shortages within health systems, this article focuses on the treatment of myocardial infarction, which is one of the costliest and most prevalent diseases. This approach establishes a link between medical and economic problems. The variables for structure quality (i.e. number of cardiologists, number of catheterization facilities) were sourced and evaluated from the ‘Herzberichte der Jahrgänge’ (‘heart reports’) compiled by Bruckenberger for the period 1994–2004 for the 16 German federal states. Data from the Federation of Quality Assurance (BQS) were used for the evaluation of process quality (i.e. adequacy of indication for coronary angiography). Finally, administrative data from the German Federal Statistical office for 1994–2004 were used to determine the variables of outcome quality (i.e. standardized mortality rate due to myocardial infarction, potential years of life lost <70 years due to myocardial infarction).Three hypotheses were tested using panel data: (i) a better structure and/or process quality increases the probability of getting a better outcome quality for the clinical picture under observation; (ii) by employing additional input factors (such as additional catheterization facilities), the probability of getting a good outcome quality is increased; and (iii) in addition to structure quality and process quality, factors lying outside of the sphere of influence of the health system have an additional influence on outcome quality (marginal gains would decrease in this case). Three models were used to test these hypotheses using fixed effects estimation.The empirical analysis produced three results. First, the analysis confirms the predicted causality between the different dimensions of quality of care for the German federal states. Notably, the number of catheterization facilities has a highly significant positive influence on the outcome quality. Second, support is found for decreasing marginal gain of inputs. Third, a good structure and a good process quality alone cannot guarantee good outcome quality. However, the analysis also showed that, in addition to healthcare provided, there are other determinants that also affect the outcome quality of healthcare. Further empirical investigation regarding the influence of these factors on the outcome dimension could elaborate on our findings and deliver additional insights.  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