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   952篇
  免费   71篇
  国内免费   5篇
耳鼻咽喉   7篇
儿科学   20篇
妇产科学   31篇
基础医学   183篇
口腔科学   3篇
临床医学   114篇
内科学   216篇
皮肤病学   10篇
神经病学   76篇
特种医学   30篇
外科学   119篇
综合类   5篇
一般理论   1篇
预防医学   33篇
眼科学   13篇
药学   49篇
中国医学   1篇
肿瘤学   117篇
  2023年   5篇
  2022年   6篇
  2021年   13篇
  2020年   7篇
  2019年   12篇
  2018年   26篇
  2017年   16篇
  2016年   14篇
  2015年   19篇
  2014年   29篇
  2013年   47篇
  2012年   57篇
  2011年   57篇
  2010年   41篇
  2009年   41篇
  2008年   67篇
  2007年   40篇
  2006年   39篇
  2005年   40篇
  2004年   44篇
  2003年   41篇
  2002年   35篇
  2001年   34篇
  2000年   53篇
  1999年   32篇
  1998年   11篇
  1997年   6篇
  1996年   8篇
  1995年   5篇
  1994年   8篇
  1993年   13篇
  1992年   10篇
  1991年   17篇
  1990年   13篇
  1989年   14篇
  1988年   9篇
  1987年   10篇
  1986年   5篇
  1985年   6篇
  1984年   10篇
  1983年   4篇
  1980年   6篇
  1979年   11篇
  1978年   9篇
  1977年   3篇
  1976年   5篇
  1975年   6篇
  1974年   6篇
  1973年   5篇
  1969年   3篇
排序方式: 共有1028条查询结果,搜索用时 62 毫秒
991.
Prediction of common bile duct stones by noninvasive tests   总被引:5,自引:0,他引:5       下载免费PDF全文
OBJECTIVE: To define accurate and useful predictors of common bile duct stones (CBDS). SUMMARY BACKGROUND DATA: The ability to predict CBDS with noninvasive tests can avoid unnecessary, costly, or risky procedures. METHODS: All patients referred for examination for CBDS by endoscopic ultrasonography (EUS) from 1993-1996 were prospectively entered in a database. In a first sample selected randomly from the whole population, predictors of CBDS were determined by univariate analysis and logistic regression. Predictors were subsequently tested in that sample and in the rest of the population. A separate analysis was done for patients planned for cholecystectomy. RESULTS: Eight hundred and eighty patients (328 men, 552 women), aged 57.8 +/- 17 years (range 16-94), were included. The prevalence of CBDS was 18.8%. Age, serum levels of bilirubin, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase (GGT), and alkaline phosphatase, and the existence of jaundice and fever, a dilated bile duct, and a pathologic gallbladder were found to be associated with CBDS. Logistic regression was undertaken separately for patients younger than 70 years (predictors: GGT >7 x normal; pathologic gallbladder; dilated bile duct) and older than 70 years (predictors: GGT >7 x normal; fever > 38 degrees C; dilated bile duct). Odds ratios were 3 to 6.7. The model was satisfactorily applicable to the second sample; age <70 years: chi2 = 3.3 (NS); age >70 years: chi2 = 3.8 (NS). In patients younger than age 70 and planned for cholecystectomy, the combination of the level of GGT and dilated bile duct predicted CBDS accurately. CONCLUSIONS: A simple screening of patients at risk for CBDS can be achieved with three predictive criteria adapted for the patient's age.  相似文献   
992.
Limited success with antigen-specific immunotherapies has led to the identification of novel approaches which consider the degeneracy of the T cell response, i.e. their ability to respond to multiple antigenic peptides. Random complex mixtures of polypeptides such as glatiramer acetate (GA) were among the first to be applied as immunodulators that take into account T cell degeneracy. While the mechanisms of action are not completely understood, the immunogenicity of GA, its strong major histocompatability complex (MHC) binding, immune deviation and bystander suppression all appear to be important. In the present study we have designed peptidic complex mixtures (CM) of varied lengths and compositions to test their potential as immunomodulating agents. CM were synthesized that had defined lengths and contained aa corresponding to binding motifs of MHC class II molecules relevant in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), specifically HLA-DRB1*1501 and HLA-DRB5*0101, which are related to MS, and H2-IA(s) associated with EAE in SJL mice. Additional CM were designed based on specificity profiles derived from positional scanning synthetic combinatorial library (PS-SCL) testing of a GA-specific T cell clone (TCC). Several mixtures were strongly stimulatory for peripheral blood mononuclear cells (PBMC) from MS patients and healthy donors suggesting a high degree of cross-reactivity with other peptide antigens. A subset of these mixtures exhibited cross-reactivity to myelin antigens and prophylactic efficacy in reducing the severity of EAE. Based on these observations we envision mixture-based peptidic compounds can be developed not only for immunotherapeutic purposes in autoimmune diseases and cancer, but also in vaccine development.  相似文献   
993.
The expression and distribution of ret proto-oncogene mRNA were investigated in five phaeochromocytomas of both familial and sporadic types by in situ hybridization (ISH) using digoxigenin-labelled cRNA probes and Northern blot (NB) analysis with random priming labelled cDNA probes. The probes corresponded to the tyrosine kinase domain of the gene. An excellent correlation was found between the ISH and NB results. By both techniques, the expression of the ret proto-oncogene was detected in three of the five cases, two of four familial tumours, and the only sporadic tumour that was studied. The results confirm that ret is frequently expressed in phaeochromocytomas and suggest that it might be an important event in their development and/or progression.  相似文献   
994.
Summary We describe an ovarian mucinous cystadenocarcinoma with several sarcoma-like mural nodules (SLMN). The distinction between these lesions and foci of anaplastic carcinoma is important because of the poor prognosis of the latter. We have studied the potential value of immunohistochemistry in the differential diagnosis of these two lesions. In contrast to an anaplastic carcinoma, which was largely composed of keratin-positive cells, SLMN were negative or only focally positive. Therefore, in distinguishing SLMN from foci of anaplastic carcinoma, keratin stains may be added to other gross and microscopical differential features, such as size, demarcation, and presence or lack of obvious carcinomatous elements.  相似文献   
995.
The tyrosine kinase receptor encoded by the MET oncogene has the unusual property of mediating the invasive growth of epithelial cells upon binding with the hepatocyte growth factor (HGF). The MET/HGF receptor is known to be overexpressed in thyroid carcinomas originated from follicular cells, but has not been reported in C cell tumors. To investigate the role of HGF and of its receptor (encoded by MET oncogene) in medullary carcinoma of the thyroid (MCT), we studied the expression of HGF and MET in 20 cases by means of different techniques. By RT-PCR, HGF mRNA was found in 10/20 cases, while MET mRNA presence was demonstrated in 8/20, of which 7 also expressed HGF. Northern blot analysis and in situ hybridization were performed in selected cases and confirmed RT-PCR data in some cases, although the lower sensitivity of these procedures did not allow the identification of all RT-PCR positive cases. By immunohistochemistry (using specific monoclonal antibodies) HGF was demonstrated in 8/9 RT-PCR positive cases ald a monoclonal to MET immunostained 5/6 RT-PCR positive cases. All receptor positive cases also expressed the ligand in the same tumor cell population. These findings demonstrate MET and HGF co-expression in a subset of MCT, in which autocrine/paracrine circuits may be active. No correlation was found between HGF/MET expression and clinico-pathological parameters, except for the more common multifocality of HGF/MET positive MCT. Whether the potential activation of MET in MCT is responsible for local invasion and malignant evolution is to be further investigated, especially in multifocal and aggressive tumors.  相似文献   
996.
The present study has investigated the functional role of the Met receptor in primary cultures of 20 papillary carcinomas and of normal thyroid cells obtained from the same patients. Normal and tumour cells grew as adherent cells, formed a confluent monolayer after 10-20 days, had epithelial morphology, and were immunoreactive for cytokeratin, vimentin, and thyroglobulin. The potential effect of hepatocyte growth factor (HGF) on cell invasiveness was investigated in Boyden chambers, using a nucleopore filter coated with Matrigel as the barrier and HGF as the chemoattractant. Tumour cells of five out of seven cases of papillary carcinoma were more responsive to HGF than the corresponding normal cells in terms of the number of migrated cells per mm(2). Involvement of the Met receptor in the HGF-induced migratory response was suggested by the observation that the agonistic anti-Met monoclonal antibody (MAb) DO-24 was equally effective. HGF did not affect the proliferative activity of thyroid cells. Under the same experimental conditions, 10 per cent fetal bovine serum (FBS) induced a two-fold increase in [(3)H]thymidine incorporation into normal cells and tumour cells. These findings are consistent with the possibility that HGF plays a crucial role in determining the invasiveness of tumour cells in papillary carcinoma of the thyroid.  相似文献   
997.
A patient with carcinoid syndrome was treated with the somatostatin analogue (SMS 201-995). The drug significantly improved the symptoms of the patient, flushing and diarrhea, and reduced urinary excretion of 5-hydroxyindole acetic acid. However, hepatic metastases remained unchanged. Clinical or biochemical adverse effects were not present during the treatment period.  相似文献   
998.
999.
French hospital database, called Programme de Médicalisation des Systèmes d'Information (PMSI), covers all hospital stays in France (>66 million inhabitants). The aim of this study was to estimate the positive predictive values (PPVs) of primary diagnosis codes of peripheral arterial and venous thrombosis codes in the PMSI, encoded with the International Classification of Diseases, 10th revision. Data were extracted from the PMSI database of Toulouse University Hospital, south of France. We identified all the hospital stays in 2015 with a code of peripheral arterial or venous thrombosis as primary diagnosis. We randomly selected 100 stays for each category of thrombosis and reviewed the corresponding medical charts. The PPV of peripheral arterial thrombosis codes was 83.0%, 95% confidence interval (CI): 73.9–89.1, and the PPV of correct location of thrombosis was 81.0%, 95% CI: 72.2–87.5. The PPV of pulmonary embolism was 99.0%, 95% CI: 93.8–99.9. The PPV of peripheral venous thrombosis was 95.0%, 95% CI: 88.2–98.1, and the PPV of correct location of thrombosis was 85.0%, 95% CI: 76.7–90.7. Primary diagnoses of peripheral arterial and venous thrombosis demonstrated good PPVs in the PMSI.  相似文献   
1000.
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