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   10398篇
  免费   695篇
  国内免费   56篇
耳鼻咽喉   56篇
儿科学   283篇
妇产科学   292篇
基础医学   1658篇
口腔科学   221篇
临床医学   1086篇
内科学   2107篇
皮肤病学   230篇
神经病学   1084篇
特种医学   354篇
外国民族医学   7篇
外科学   992篇
综合类   46篇
一般理论   2篇
预防医学   823篇
眼科学   114篇
药学   810篇
中国医学   30篇
肿瘤学   954篇
  2024年   13篇
  2023年   78篇
  2022年   153篇
  2021年   297篇
  2020年   190篇
  2019年   249篇
  2018年   270篇
  2017年   231篇
  2016年   285篇
  2015年   319篇
  2014年   430篇
  2013年   517篇
  2012年   837篇
  2011年   967篇
  2010年   501篇
  2009年   466篇
  2008年   743篇
  2007年   776篇
  2006年   709篇
  2005年   679篇
  2004年   581篇
  2003年   487篇
  2002年   482篇
  2001年   87篇
  2000年   65篇
  1999年   89篇
  1998年   94篇
  1997年   87篇
  1996年   81篇
  1995年   54篇
  1994年   50篇
  1993年   35篇
  1992年   38篇
  1991年   22篇
  1990年   19篇
  1989年   18篇
  1988年   11篇
  1987年   12篇
  1986年   11篇
  1985年   10篇
  1984年   10篇
  1983年   12篇
  1982年   8篇
  1981年   10篇
  1980年   7篇
  1978年   4篇
  1977年   6篇
  1974年   4篇
  1973年   6篇
  1970年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
PURPOSE: For the first time a large number (563) of non-small cell lung cancer (NSCLC) samples was used to compare three different technologies for the assessment of HER2 status. Fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) were used for tumor tissue samples, and ELISA for serum samples. The results were compared with other tumor entities, mainly breast. EXPERIMENTAL DESIGN: Samples (563) from patients suffering from primary advanced or metastatic NSCLC were evaluated. RESULTS: HER2 overexpression was demonstrated using IHC in 20% (83 of 410) of the specimens, whereas 2% (7 of 378) were positive by FISH and 6% (31 of 511) showed elevated serum HER2 levels (>15 ng/ml) by ELISA. Sixty-six specimens were positive by IHC only and 13 by ELISA only, whereas none of the specimens was positive only by FISH. Concordance between all of the techniques was seen for only 3 specimens. Of 7 IHC 3+ specimens, 4 showed gene amplification by FISH, and 3 were positive by ELISA (>15 ng/ml), whereas of 76 IHC 2+ cases only 2 were amplified by FISH, and 4 were positive by ELISA. HER2 positivity by at least one of the three techniques was most common in adenocarcinomas, at 29% (42 of 143). CONCLUSION: Gene amplification and HER2 protein overexpression at the 3+ level appear to be uncommon in NSCLC. The concordance between FISH and IHC 3+ disease was good in this study, in addition, ELISA would have detected several patients without IHC/FISH-positive disease.  相似文献   
73.
Angiogenesis in Vulvar Intraepithelial Neoplasia   总被引:1,自引:0,他引:1  
Vulvar intraepithelial neoplasia (VIN) has been reported to be a precursor of invasive vulvar cancer. Switching to the angiogenic phenotype is considered a key step in tumor growth. Microvessel density (MVD) and vascular endothelial growth factor (VEGF), a highly angiogenic peptide, are important parameters of tumor angiogenesis. Forty-three histologic slides with 38 VIN I–III lesions were immunohistochemically stained for factor VIII-related antigen (F8-RA) and 44 slides with 37 VIN I–III for VEGF, since F8-RA reliably highlights tumor microvessels. Determination of MVD and VEGF expression was done by counting microvessels and VEGF-positive cells at a magnification of 200× and 400×. The highest concentration of F8-RA-stained MVD and VEGF expression was found at a small subepithelial area at the border of the VIN lesion to the stroma underneath but concentrations were low in all specimens of normal epithelium. High VEGF expression was significantly correlated to high MVD. For both MVD and VEGF expression the differences between VIN I and VIN III and between VIN II and VIN III were statistically significant (P< 0.0001). VIN III lesions are the clinical relevant precursors of invasive cancer of the vulva, as outlined by intense expression of VEGF protein and a highly dense network of microvessels underlying the dysplastic epithelium.  相似文献   
74.
Objective: The combination of transvaginal sonography and serum hCG measurement is reliable in the diagnosis of ectopic pregnancy (EP) in spontaneous pregnancies. In patients who became pregnant through IVF-ET, transfer of multiple embryos after IVF could be responsible for the different performance of these tests. We evaluated the discriminative capacity of transvaginal sonography in combination with hCG measurement in the diagnosis of EP after IVF-ET.

Design: Prospective cohort study.

Setting and Patient(s): Consecutive patients, pregnant through IVF-ET, who presented with clinically suspected EP.

Intervention(s): Transvaginal sonography, serum hCG measurement at 6, 9, and 15 days after ET and after a negative transvaginal sonography.

Main Outcome Measure(s): Ectopic pregnancy confirmed at laparoscopy.

Result(s): Between September 1993 and May 1996, 86 women were included in the study, of whom 24 had an EP. Transvaginal sonography identified 46 intrauterine pregnancies and 5 EPs, but serum hCG could not diagnose EPs in patients in whom transvaginal sonography did not show a gestational sac. Serum hCG measurement 9 days after ET could identify pregnancy failure with 100% specificity at a cut-off value of 18 IU/L, but it could not identify patients with EP with enough certainty to justify immediate treatment.

Conclusion(s): We recommend single serum hCG measurement 9 days after ET to discriminate between viable and nonviable pregnancies. Transvaginal sonography can be postponed until 5 weeks after ET, except for patients with abdominal pain and/or vaginal bleeding, or patients with a serum hCG level of <18 IU/L.  相似文献   

75.
76.
BACKGROUND AND PURPOSE: In 1990 the skin source measuring bridge was proposed as a tool to measure (1) the distance between the interstitial implant and the overlying skin during brachytherapy boost treatment as well as (2) the distances between the lateral source end and the exit point of the guide needle. The present study reports on the clinical experience using the source skin measuring bridge with respect to incidence and grade of teleangiectasia, and their relation to source skin distances and doses. PATIENTS AND METHODS: Two hundred and twenty-two breast cancer patients (229 breasts) treated between 1983 and 1996 with breast conserving therapy including a brachytherapy boost were scored on the occurrence of teleangiectasia. The minimum distance between the sources (above implant and laterally) and the skin surface were measured. RESULTS: If no bridge was used the appearance of teleangiectasia in the epiderm above the implant is 77, 63 and 50% for boost doses of 25, 20 and 15 Gy, respectively. For brachytherapy boost doses of 25 and 20 Gy and distances smaller than 10mm between the implant and the overlying epiderm, as determined with the skin source measuring bridge, the appearance of teleangiectasia was 78 and 46%, respectively. When respecting provisional dosimetry to spare the skin for a boost dose of 15 Gy, resulting in distances between 10 and 15 mm for the implant overlying skin and distances between 5 and 10 mm for the lateral skin, teleangiectasia can be reduced to a minimum (6.3% above and 3.3% laterally). While in a univariate analysis several parameters (use of the bridge, boost dose, boost modality, external beam therapy modality) were predictive factors, the use of the bridge remained the only significant variable in a multivariate analysis. CONCLUSIONS: The skin source measuring bridge reduces teleangiectasia after interstitial brachytherapy boost treatment. A hypothesis made previously relating teleangiectasia and source skin distances was verified and extended. Even when 3D planning is used, the bridge allows for a provisional calculation of the security margins between source positions and the skin at the time of BT implantation to assure a correct needle positioning from the beginning, instead of correcting dwell times later on to avoid unnecessary high skin doses.  相似文献   
77.
PURPOSE: A phase III study to determine whether a weekly docetaxel schedule improves the therapeutic index compared with the classic 3-weekly schedule. PATIENTS AND METHODS: Patients with stage IIIB-IV non-small-cell lung cancer (NSCLC) were randomly assigned to docetaxel 75 mg/m2 on day 1 every 3 weeks (3-weekly) and 35 mg/m2 on days 1, 8, and 15 (weekly) for < or = eight cycles. End points included survival (primary), toxicity, and response. RESULTS: Of 215 patients enrolled, 208 (103 in the 3-weekly arm and 105 in the weekly arm) were assessable for response. At baseline, 24.5% of patients (51 out of 208) had received prior paclitaxel therapy and 43.3% of patients (90 out of 208) had been progression-free for more than 3 months after first-line therapy. After 12 months' follow-up, median survival was 6.3 months (95% CI, 4.68 to 7.84 months) with 3-weekly docetaxel and 9.2 months (95% CI, 5.83 to 12.59 months) with weekly docetaxel (P = .07) after a median of four (range, one to eight) and two (range, one to eight) treatment cycles, respectively. Overall, response rates were 12.6% v 10.5% with 3-weekly versus weekly docetaxel. Significantly fewer patients reported grade 3 to 4 toxicities with weekly docetaxel versus 3-weekly docetaxel (P < or = .05). There were significantly lower rates of grade 3 to 4 anemia (P < or = .05), leucopenia (P < .0001), and neutropenia (P < or = .001) with weekly versus 3-weekly treatment. No grade 3 to 4 thrombocytopenia or mucositis was reported. CONCLUSION: Weekly docetaxel 35 mg/m2 demonstrated similar efficacy and better tolerability than standard 3-weekly docetaxel 75 mg/m2 and can be recommended as a feasible alternative second-line treatment option for patients with advanced NSCLC.  相似文献   
78.
79.
BackgroundThe question of how to deal with B3 lesions is of emerging interest.MethodsIn the breast diagnostics of 192 patients between 2009 and 2016, a minimally invasive biopsy revealed a B3 lesion with subsequent resection. This study investigates the malignancy rate of different B3 subgroups and the risk factors that play a role in obtaining a malignant finding.ResultsThe distribution of B3 lesions after minimally invasive biopsy was as follows: atypical ductal hyperplasia (ADH), 7.3%; flat epithelial atypia (FEA), 7.8%; lobular neoplasia (LN), 7.8%; papilloma (Pa), 49.5%; phylloidal tumour (PT), 8.9%; radial sclerosing scar (RS), 3.1%; mixed findings, 10.4%; and other B3 lesions, 5.2%. Most B3 lesions were detected by stereotactic vacuum-assisted biopsy (44.3%), 36.5% by ultrasound-assisted biopsy, and 19.3% by magnetic resonance imaging-assisted biopsy. Most B3 lesions (55.2%) were verified by surgical resection, whereas 30.7% were downgraded to a benign lesion. About 14.1% of the cases were upgraded to malignant lesions, 9.4% to ductal carcinoma in situ and 4.7% to invasive carcinoma. In relation to individual B3 lesions, the following malignancy rates were found: 28.6% (ADH), 13.3% (FEA), 33.3% (LN), 12.6% (Pa), 5.9% (PT), and 0% (RS). The most important risk factor was increasing age. Postmenopausal status was considered an increased risk for an upgrade (p = 0.015). A known malignancy in the ipsilateral breast was a significant risk factor for a malignant upgrade (p = 0.003).ConclusionIncreasing knowledge about B3 lesions allows us to develop a “lesion-specific” therapy approach in the heterogeneous group of B3 lesions, with follow-up imaging for some lesions with less malignant potential and concordance with imaging or further surgical resection in cases of disconcordance with imaging or higher malignant potential.  相似文献   
80.
Flavonoids are found universally in plants and act as free radical scavenging and chelating agents with antiinflammatory, antiischemic, vasodilating and chemoprotective properties. In this study, the antilipoperoxidative and cytoprotective effects of apigenin, baicalein, kaempferol, luteolin and quercetin against doxorubicin-induced oxidative stress were investigated in isolated rat heart cardiac myocytes, mitochondria and microsomes. After preincubation of cardiomyocytes with the test compounds for 1 h the cardiomyocytes were treated with the toxic agent, doxorubicin (100 micro M for 8 h). Cardiomyocyte protection was assessed by extracellular LDH and cellular ADP and ATP production. Cytoprotection was concentration dependent for baicalein > luteolin congruent with apigenin > quercetin > kaempferol. All test compounds had signi fi cantly better protective effects than dexrazoxan, an agent currently used for adjuvant therapy during anthracycline antibiotic therapy. In microsomes/mitochondria the IC(50) values of lipid peroxidation inhibition for quercetin, baicalein, kaempferol, luteolin, and apigenin were 3.1 +/- 0.2/8.2 +/- 0.6, 3.3 +/- 0.3/9.6 +/- 0.5, 3.9 +/- 0.3/10.1 +/- 0.8, 22.9 +/- 1.7/18.2 +/- 0.7, and 338.8 +/- 23.1/73.1 +/- 6.4 mM, respectively. The antilipoperoxidative activity of apigenin differed from its cytoprotective effects, but correlated with the free radical scavenging of 2,2-diphenyl-1-picrylhydrazyl radical and half peak oxidation potential (E(p/2)). Apigenin was the least effective of the flavonoids studied in all models except the cardiomyocyte model where its cardiomyocyte cytoprotective effect was comparable to other compounds.  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