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   12041篇
  免费   774篇
  国内免费   32篇
耳鼻咽喉   79篇
儿科学   434篇
妇产科学   355篇
基础医学   1624篇
口腔科学   363篇
临床医学   1745篇
内科学   2033篇
皮肤病学   168篇
神经病学   1156篇
特种医学   225篇
外科学   1132篇
综合类   134篇
一般理论   16篇
预防医学   1741篇
眼科学   166篇
药学   738篇
  1篇
中国医学   20篇
肿瘤学   717篇
  2023年   68篇
  2022年   128篇
  2021年   261篇
  2020年   189篇
  2019年   258篇
  2018年   329篇
  2017年   220篇
  2016年   281篇
  2015年   302篇
  2014年   444篇
  2013年   613篇
  2012年   932篇
  2011年   965篇
  2010年   536篇
  2009年   506篇
  2008年   840篇
  2007年   860篇
  2006年   816篇
  2005年   746篇
  2004年   711篇
  2003年   599篇
  2002年   583篇
  2001年   111篇
  2000年   87篇
  1999年   124篇
  1998年   114篇
  1997年   103篇
  1996年   77篇
  1995年   68篇
  1994年   60篇
  1993年   59篇
  1992年   73篇
  1991年   50篇
  1990年   44篇
  1989年   52篇
  1988年   61篇
  1987年   53篇
  1986年   33篇
  1985年   41篇
  1984年   47篇
  1983年   45篇
  1982年   29篇
  1981年   35篇
  1980年   36篇
  1979年   39篇
  1978年   38篇
  1977年   25篇
  1976年   16篇
  1975年   18篇
  1973年   18篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Current digital information systems in radiology are insufficient to accommodate the retrieval needs of academicians. Significant efforts are required in retrieving clinical cases for teaching and research. We describe a prototype system that supports intelligent case retrieval based on a combined specification of patient demographics, radiologic findings, and pathologic diagnoses. The documents for these cases can be distributed among multiple heterogeneous data bases. The system features automatic indexing of radiology and pathology reports, a comprehensive lexicon for thoracic radiology, an interface to a hospital information system, radiology information system, and picture archiving and communication systems, and a graphical user interface for query formulation and results visualization. The prototype system was developed within the domain of thoracic radiology involving patients with lung cancer.  相似文献   
42.
A barrier to the appropriate provision of antiretroviral therapy to treat immunosuppressed HIV-infected persons in resource-poor countries is identifying who requires treatment. The World Health Organization (WHO) has suggested using a clinical algorithm combined with a total lymphocyte count (TLC) < 1200 cells/mm as a surrogate for a CD4 count less than 200 cells/mm when it is not possible to measure the CD4 count. We evaluated various TLC levels, anemia, and body mass index and compared our data with the WHO criteria to develop a more sensitive algorithm to predict CD4 counts of < 200 cells/mm and < 350 cells/mm in 839 men and women from Thailand infected with HIV-1 subtype E (CRF01_AE). The December 2003 WHO guidelines had a sensitivity of 34.1% in men and 31.8% in women to detect persons with a CD4 count < 200 cells/mm in this HIV-infected population from Thailand. The use of a TLC < 1500 cells/mm or TLC < 2000 cells/mm combined with anemia or WHO stage II infection doubled the sensitivity to detect persons with a CD4 count < 200 (63.0% in men, 68.2% in women) with less than a 6% decrease in specificity.  相似文献   
43.
Although mucoepidermoid carcinoma is the most common primary malignancy of the salivary glands, the sclerosing morphologic variant of this tumor is extremely rare, with only 6 reported cases. As its name suggests, sclerosing mucoepidermoid carcinoma is characterized by an intense central sclerosis that occupies the entirety of an otherwise typical tumor, frequently with an inflammatory infiltrate of plasma cells, eosinophils, and/or lymphocytes at its peripheral regions. The sclerosis associated with these tumors may obscure their typical morphologic features and result in diagnostic difficulties. Tumor infarction and extravasation of mucin eventuating in reactive fibrosis are 2 mechanisms of formation that have been suggested as underlying this morphologic variant. We describe herein another case of sclerosing mucoepidermoid carcinoma that was diagnosed in a 44-year-old woman and review the relevant literature. Morphologic evidence in support of the mucin extravasation hypothesis was identified, as small pools of mucin were present throughout the tumor. However, there was no concentration of the mucin pools near the areas with the most viable tumor cells, which would have provided evidence for a temporal sequence that eventuates in lack of mucin in the most sclerotic regions.  相似文献   
44.
West Nile virus (WNV) is an emerging flavivirus that has caused frequent epidemics since 1996. Besides natural transmission by mosquitoes, WNV can also be transmitted through blood transfusion and organ transplantation, thus heightening the urgency of development of a specific and rapid serologic assay of WNV infection. The current immunoassays lack specificity because they are based on detection of antibodies against WNV structural proteins and immune responses to structural proteins among flaviviruses cross-react to each other. Here, we describe microsphere immunoassays that detect antibodies to nonstructural proteins 3 and 5 (NS3 and NS5). In contrast to immunoassays based on viral envelope and NS3 proteins, the NS5-based assay (i) reliably discriminates between WNV infections and dengue virus or St. Louis encephalitis virus infections, (ii) differentiates between flavivirus vaccination and natural WNV infection, and (iii) indicates recent infections. These unique features of the NS5-based immunoassay will be very useful for both clinical and veterinary diagnosis of WNV infection.  相似文献   
45.
46.
The enhancement of eosinophil function by lymphocyte supernatants   总被引:1,自引:1,他引:1       下载免费PDF全文
Supernatants obtained from non-stimulated lymphocytes, lymphocytes stimulated with phytohaemagglutinin and lymphocytes from patients with schistosomiasis that were stimulated with Schistosomiasis haematobium ova were shown to enhance a number of eosinophil functions. Eosinophil chemotaxis, phagocytosis, microbicidal activity, Nitro blue tetrazolium reduction, hexose monophosphate shunt activity and glycolysis were increased. Eosinophil iodination was not affected. Only those supernatants obtained from phytohaemagglutinin stimulated lymphocytes and lymphocytes from patients with schistosomiasis that were stimulated with S. haematobium ova showed eosinophil chemotactic activity. The active factor was found to be heat stable, and had no effect on cAMP and cGMP metabolism. The most likely mechanism of enhanced eosinophil function is through the increased activity of the hexose monophosphate shunt activity and glycolysis.  相似文献   
47.
To date, only one complete genome screen for obsessive-compulsive disorder (OCD) has been published. That study identified a region of suggestive linkage (maximum lod score of 2.25) with a relatively small sample size (N = 56; 27 with OCD). Additional complete genome screens are needed to confirm this finding and identify other regions of linkage. We present the clinical characteristics and power to detect linkage of 11 multigenerational families with OCD and hoarding (N = 92; 44 with OCD), as well as heritability estimates for several quantitative traits. Families with at least two individuals with OCD were identified through probands with childhood-onset OCD. Expected lod scores were calculated for simulated genetic marker data under an additive and two dominant models assuming a dense SNP marker map. All affected individuals had an early age of onset (18 or younger). Hoarding was present in 46% of subjects. Obsessive-compulsive symptoms and hoarding were highly heritable. The maximum mean expected lod score was 3.31 for OCD and 1.39 for hoarding. We found reasonable power to detect regions of interest (lod = 2) for OCD in these families, but will need to expand our family collection to have adequate power to detect regions of interest for hoarding.  相似文献   
48.
Endemic pemphigus foliaceus (EPF) is an autoimmune disease characterized by blister formation with a loss of cohesion and infiltration of inflammatory cells. We observed that supernatants of peripheral blood mononuclear cells from patients produced significantly more interleukin-1beta (IL-1beta) than those from stimulated healthy controls. Furthermore, a Th2 bias was observed in EPF patients when the IL-5/gamma interferon ratio was analyzed. These results indicate that cells from pemphigus patients react with a vigorous proinflammatory response.  相似文献   
49.
Mammalian sex chromosomes evolved from an ancient autosomal pair. Mapping of human X- and Y-borne genes in distantly related mammals and non-mammalian vertebrates has proved valuable to help deduce the evolution of this unique part of the genome. The platypus, a monotreme mammal distantly related to eutherians and marsupials, has an extraordinary sex chromosome system comprising five X and five Y chromosomes that form a translocation chain at male meiosis. The largest X chromosome (X1), which lies at one end of the chain, has considerable homology to the human X. Using comparative mapping and the emerging chicken database, we demonstrate that part of the therian X chromosome, previously thought to be conserved across all mammals, was lost from the platypus X1 to an autosome. This region included genes flanking the XIST locus, and also genes with Y-linked homologues that are important to male reproduction in therians. Since these genes lie on the X in marsupials and eutherians, and also on the homologous region of chicken chromosome 4, this represents a loss from the monotreme X rather than an additional evolutionary stratum of the human X.  相似文献   
50.

Introduction

Total Lymphocyte Count (TLC) has been found to be an inexpensive and useful marker for staging disease, predicting progression to AIDS and death and monitoring response to ART. However, the correlation between TLC and CD4 has not been consistent. Access to HAART is expanding in Kampala, Uganda, yet there are no published data evaluating the utility of TLC as inexpensive surrogate marker of CD4 cell count to help guide therapeutic decisions.

Objective

To evaluate clinical illnesses and total lymphocyte count (TLC) as surrogate markers of the CD4 cell count in HIV infected persons being considered for ART.

Methods

A total of 131 patients were enrolled and evaluated by clinical assessment, TLC and CD4 count. Clinical illnesses and TLC dichotomized at various cut-point values were used to determine the sensitivity, specificity, and positive and negative predictive values (PPV and NPV) for the diagnosis of CD4 count <200 cells/mm3 among 100 participants fulfilling criteria for WHO clinical stage 2 and 3.

Results

A strong correlation was observed between TLC and CD4 (r = 0.73, p<0.0001). For all clinical syndromes, except pulmonary tuberculosis, the positive predictive values (PPV) for a CD4 count <200 cells/mm3 were high (>80%) but the negative predictive values (NPV) were low. Using the WHO recommended TLC cut-off of 1200 cells/mm3 to diagnose a CD4 less than 200 cells/mm3, the PPV was 100%, and the NPV was 32%.

Conclusion

Our data showed a good correlation between TLC and CD4 cell count. However, the WHO recommended TLC cutoff of 1200 did not identify the majority of WHO stage 2 and 3 patients with CD4 counts less than 200 cells/mm3. A more rational use of TLC counts is to treat all patients with WHO stage 2 and 3 who have a TLC <1200 and to limit CD4 counts to patients who are symptomatic but have TLC of >1200.  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