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   11799篇
  免费   830篇
  国内免费   205篇
耳鼻咽喉   309篇
儿科学   135篇
妇产科学   156篇
基础医学   2000篇
口腔科学   169篇
临床医学   856篇
内科学   2540篇
皮肤病学   433篇
神经病学   875篇
特种医学   977篇
外科学   1444篇
综合类   48篇
一般理论   2篇
预防医学   359篇
眼科学   392篇
药学   994篇
中国医学   151篇
肿瘤学   994篇
  2024年   5篇
  2023年   78篇
  2022年   333篇
  2021年   490篇
  2020年   237篇
  2019年   340篇
  2018年   440篇
  2017年   311篇
  2016年   569篇
  2015年   722篇
  2014年   741篇
  2013年   853篇
  2012年   1243篇
  2011年   1135篇
  2010年   674篇
  2009年   561篇
  2008年   749篇
  2007年   695篇
  2006年   534篇
  2005年   507篇
  2004年   414篇
  2003年   332篇
  2002年   249篇
  2001年   132篇
  2000年   131篇
  1999年   85篇
  1998年   46篇
  1997年   19篇
  1996年   14篇
  1995年   19篇
  1994年   12篇
  1993年   16篇
  1992年   18篇
  1991年   15篇
  1990年   11篇
  1989年   22篇
  1988年   8篇
  1987年   16篇
  1986年   8篇
  1985年   6篇
  1984年   4篇
  1983年   5篇
  1982年   4篇
  1979年   9篇
  1978年   3篇
  1977年   3篇
  1976年   6篇
  1975年   4篇
  1969年   2篇
  1967年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
Brenner tumor of the ovary: CT and MR findings   总被引:4,自引:0,他引:4  
PURPOSE: The purpose of this study was to determine the CT and MR characteristics of Brenner tumors, rare epithelial neoplasms of the ovary. METHOD: CT and MR scans of eight pathologically proven Brenner tumors of the ovary (seven benign, one malignant, and one associated with mucinous cystadenoma) were retrospectively reviewed. The masses were analyzed for location, size, external configuration, internal architecture, enhancement pattern, presence of calcification, and metastatic spread. RESULTS: The patients' median age was 63 years (range 39-79 years), and the mean size of the tumors was 11.4 cm (7.5-17 cm). All tumors were unilateral and had a well-defined margin. The mass was mostly solid in three, mostly cystic in one, and "mixed" solid and cystic in four cases. The tumors with cystic components (n = 5) were mostly multilocular in appearance (n = 4). All the solid components showed mild homogeneous enhancement on postcontrast CT and MRI. Extensive amorphous calcification within the solid component on CT was seen in five of six cases (83%). No characteristic findings discriminating malignancy from benign Brenner tumor could be found. CONCLUSION: Extensive amorphous calcification in a solid mass or solid component in a multilocular cystic mass is a characteristic finding of Brenner tumor of the ovary on CT and MRI.  相似文献   
103.
104.
DNA methylation changes are associated with cigarette smoking. We used the Illumina Infinium HumanMethylation450 array to determine whether methylation in DNA from pre‐diagnostic, peripheral blood samples is associated with lung cancer risk. We used a case‐control study nested within the EPIC‐Italy cohort and a study within the MCCS cohort as discovery sets (a total of 552 case‐control pairs). We validated the top signals in 429 case‐control pairs from another 3 studies. We identified six CpGs for which hypomethylation was associated with lung cancer risk: cg05575921 in the AHRR gene (p‐valuepooled = 4 × 10?17), cg03636183 in the F2RL3 gene (p‐valuepooled = 2 × 10 ? 13), cg21566642 and cg05951221 in 2q37.1 (p‐valuepooled = 7 × 10?16 and 1 × 10?11 respectively), cg06126421 in 6p21.33 (p‐valuepooled = 2 × 10?15) and cg23387569 in 12q14.1 (p‐valuepooled = 5 × 10?7). For cg05951221 and cg23387569 the strength of association was virtually identical in never and current smokers. For all these CpGs except for cg23387569, the methylation levels were different across smoking categories in controls (p‐valuesheterogeneity ≤ 1.8 x10 ? 7), were lowest for current smokers and increased with time since quitting for former smokers. We observed a gain in discrimination between cases and controls measured by the area under the ROC curve of at least 8% (p‐values ≥ 0.003) in former smokers by adding methylation at the 6 CpGs into risk prediction models including smoking status and number of pack‐years. Our findings provide convincing evidence that smoking and possibly other factors lead to DNA methylation changes measurable in peripheral blood that may improve prediction of lung cancer risk.  相似文献   
105.
We retrospectively investigated the incidence, risk factors, and outcomes of SOS (sinusoidal obstruction syndrome; previously veno-occlusive disease [VOD]) after allogeneic hematopoietic stem cell transplantation (alloHSCT) in aplastic anemia. Two hundred and sixty patients were included in the analysis. SOS developed in 7.3% (n = 19/260) of patients. Classical Cy (200 mg/m2)-ATG was the most common conditioning regimen (84.2%) in the SOS group. The SOS mortality rate was 4/19 (21.1%). Univariate analyses revealed that Cy 200 mg/m2 conditioning (p = 0.035), classical Cy-ATG conditioning (p = 0.007), and horse ATG conditioning (p < 0.001) were significant risk factors for developing SOS. Multivariate analysis revealed that only horse ATG conditioning was a poor prognostic factor (HR = 3.484; 95% CI 1.226–9.904; p = 0.002). Rabbit ATG (HR 12.719; 95% CI 2.332–69.373; p = 0.003) and weight gain > 10% (HR 35.655; 95% CI 2.208–575.805; p = 0.012) were risk factors in the overall SOS group. Both rabbit ATG conditioning and weight gain of more than 10% were associated with poor overall survival with a median of 1.2 months (5Y survival rate, any risk factor vs. none: 74.6% vs. 0.0%; p < 0.001; Fig. 2) in the SOS group.  相似文献   
106.

Background

Somatic v-Raf murine sarcoma viral oncogene homolog B (BRAF) mutation, present in approximately 10% of metastatic colorectal cancer (mCRC) cases, is associated with poor prognosis. Patient outcome outside of clinical trials has only been reported in small series. We report real-world data on treatment and survival for BRAF-mutated (MT) patients at a single tertiary center, compared with a matched BRAF wild type (WT) control group.

Patients and Methods

All colorectal cancer patients tested for BRAF mutation, from October 2010 to November 2014 were identified. BRAF-MT mCRC cases were compared with an age and sex-matched BRAF-WT control group. Clinicopathological data were collected and survival calculated using the Kaplan–Meier method and comparisons made using Cox regression.

Results

Forty-three of 503 patients (8.5%) tested had BRAF-MT mCRC and were compared with 88 BRAF-WT controls. Median overall survival (mOS) was 18.2 months for BRAF-MT and 41.1 months for BRAF-WT mCRC patients (hazard ratio, 2.74; 95% confidence interval, 1.60-4.70; P < .001). Progression-free survival for BRAF-MT and WT patients, respectively, was: 8.1 months versus 9.2 months (P = .571) first-line, 5.5 months versus 8.3 months (P = .074) second-line, and 1.8 months versus 5.6 months (P = .074) third-line. Treatment using sequential fluoropyrimidine-based doublet chemotherapy was similar between both groups. Anti-epidermal growth factor receptor (EGFR) therapy was mainly given third-line with progressive disease in 90% (n = 9 of 10) of BRAF-MT patients at first restaging.

Conclusion

In this case-control study, the poor mOS of BRAF-MT mCRC was associated with reduced treatment benefit beyond first-line. Sequential doublet chemotherapy remains a reasonable option in appropriately selected patients. BRAF-MT patients did not benefit from anti-EGFR therapy in this study. Recruitment to clinical trials is recommended to improve outcomes in BRAF-MT mCRC.  相似文献   
107.
Chemotherapy, one of the principal approaches for cancer patients, plays a crucial role in controlling tumor progression. Clinically, tumors reveal a satisfactory response following the first exposure to the chemotherapeutic drugs in treatment. However, most tumors sooner or later become resistant to even chemically unrelated anticancer agents after repeated treatment. The reduced drug accumulation in tumor cells is considered one of the significant mechanisms by decreasing drug permeability and/or increasing active efflux (pumping out) of the drugs across the cell membrane. The mechanisms of treatment failure of chemotherapeutic drugs have been investigated, including drug efflux, which is mediated by extracellular vesicles (EVs). Exosomes, a subset of EVs with a size range of 40–150 nm and a lipid bilayer membrane, can be released by all cell types. They mediate specific cell‐to‐cell interactions and activate signaling pathways in cells they either fuse with or interact with, including cancer cells. Exosomal RNAs are heterogeneous in size but enriched in small RNAs, such as miRNAs. In the primary tumor microenvironment, cancer‐secreted exosomes and miRNAs can be internalized by other cell types. MiRNAs loaded in these exosomes might be transferred to recipient niche cells to exert genome‐wide regulation of gene expression. How exosomal miRNAs contribute to the development of drug resistance in the context of the tumor microenvironment has not been fully described. In this review, we will highlight recent studies regarding EV‐mediated microRNA delivery in formatting drug resistance. We also suggest the use of EVs as an advancing method in antiresistance treatment.  相似文献   
108.
109.
The purpose of this study was to confirm the association between the serum vitamin D levels and ischemic stroke lesion size, functional ability, and cognitive function in elderly ischemic stroke patients. This study included Korean ischemic stroke patients aged 65 to 85 years. The size of the lesion was measured in brain images taken within 24 hours of hospitalization. The level of 25-(OH) Vitamin D (ng/mL), a metabolite of vitamin D, in the serum collected within 48 hours of hospitalization, and the modified Barthel index (MBI), gait performance, the muscle power of hip and knee extensors on the hemiplegic side, and mini-mental status examination (MMSE) were recorded within 1 week of the onset of the disease. Each factor was compared through correlation analysis, and the significance was confirmed using the Spearman correlation coefficient method. The association between the serum vitamin D levels and the size of the ischemic stroke lesion, the MBI, gait performance, the muscle power of hip and knee extensors on the hemiplegic side, and the MMSE were analyzed. It was confirmed that there was a significant correlation between all the factors (P < .005). In patients with serum vitamin D levels of ≥ 30 ng/mL, both the functional ability and cognitive functions were better than in patients lower than 30 ng/mL. We confirmed the lower the level of serum vitamin D levels, the larger the size of the ischemic stroke lesion when it occurred in elderly Koreans. And we confirmed that serum vitamin D levels affected the functional ability and cognitive function. And we recommend that elderly Koreans should maintain their blood vitamin D level above 30 ng/mL. We believe that this will help preserve the functional ability and cognitive function when ischemic stroke occurred.  相似文献   
110.
This study aimed to compare and analyze the prognosis after lipectomy with respect to the difference in time required for indocyanine green (ICG) to reach the axilla in patients with advanced unilateral upper extremity lymphedema. The study population was divided into 2 groups, according to the time required by ICG to reach the axilla after injection, that is, <1 hour (<1 hour; n = 9) and over 1 hour (>1 hour; n = 8). The patient’s arm volume was examined before surgery and up to 12 months after surgery. The volume difference between the 2 groups was compared using the excess volume ratio. Statistically significant differences were not observed before surgery (P = .847) and 1 month (P = .336), 3 months (P = .630), and 6 months after surgery (P = .124) between the excess volume ratio values of the < 1 hour and > 1 hour groups. A statistically significant difference was confirmed 12 months after surgery (P = .034). The difference in the time when ICG reached the axilla in patients with lymphedema was associated with prognosis after lipectomy. The difference in time could possibly be used as a variable to classify the progress of lymphedema in the future.  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