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   162026篇
  免费   10327篇
  国内免费   1205篇
耳鼻咽喉   2271篇
儿科学   3021篇
妇产科学   3741篇
基础医学   24046篇
口腔科学   3358篇
临床医学   15377篇
内科学   30911篇
皮肤病学   4343篇
神经病学   12106篇
特种医学   8091篇
外科学   21915篇
综合类   2163篇
现状与发展   5篇
一般理论   81篇
预防医学   9730篇
眼科学   4316篇
药学   13656篇
  36篇
中国医学   1602篇
肿瘤学   12789篇
  2024年   337篇
  2023年   1156篇
  2022年   2763篇
  2021年   4924篇
  2020年   2584篇
  2019年   3590篇
  2018年   4407篇
  2017年   3231篇
  2016年   4190篇
  2015年   5635篇
  2014年   6910篇
  2013年   8366篇
  2012年   12642篇
  2011年   12276篇
  2010年   7245篇
  2009年   6063篇
  2008年   9253篇
  2007年   9118篇
  2006年   8378篇
  2005年   7978篇
  2004年   7118篇
  2003年   6184篇
  2002年   5372篇
  2001年   4377篇
  2000年   4026篇
  1999年   3263篇
  1998年   1309篇
  1997年   989篇
  1996年   949篇
  1995年   862篇
  1994年   750篇
  1993年   642篇
  1992年   1572篇
  1991年   1569篇
  1990年   1353篇
  1989年   1236篇
  1988年   1154篇
  1987年   1031篇
  1986年   1010篇
  1985年   882篇
  1984年   644篇
  1983年   563篇
  1982年   399篇
  1981年   377篇
  1980年   338篇
  1979年   519篇
  1978年   406篇
  1977年   388篇
  1976年   342篇
  1974年   358篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
BackgroundTo determine whether 3D-CT imaging technique is valid and reproducible compared to conventional CT measurement technique (CCT) for the detection of a femoropatellar instability.MethodsPatients who had undergone surgery for femoropatellar instability (patellar instability group) between 2010 and 2016 (n = 37 knees of 35 patients) were retrospectively enrolled. For the matched control group, patients who had acute anterior cruciate ligament injury (< 4 weeks previously; n = 30) were recruited. Preoperative CT data had been obtained in all patients. Inter-rater reliability was calculated for both measurement protocols, and inter-method reliability was calculated between the two imaging modalities. The results are reported using intraclass correlation coefficients (ICCs) and Bland–Altman 95% limits of agreement.ResultsAll patients in the patellar instability group had femoral trochlear dysplasia (Dejour types A: four, B: 19, C: seven, and D: six), but no dysplasia was noted in the control group. In the patellar instability group, the CCT technique showed a poor inter-rater agreement (ICC = 0.74), and the 3D-CT technique still showed excellent inter-rater agreement (ICCs = 0.91). In the sub-analysis of the patellar instability group according to the trochlear dysplasia grade, ICCs were markedly decreased with severe trochlear dysplasia when using CCT technique; however, the 3D-CT technique could provide excellent reliability even with severe trochlear dysplasia.ConclusionThe 3D-CT imaging technique for the measurement of the TT–TG distance can be suggested as a better measurement technique for patellar instability patients with bone abnormality.  相似文献   
52.
PurposePatellofemoral arthroplasty (PFA) prosthesis with asymmetric trochlear component was introduced as an improvement from existing designs for surgical treatment of symptomatic isolated patellofemoral arthritis. The purpose of this study was to evaluate midterm results in patients who underwent PFA procedure using such prosthesis.MethodsOur study involved a continuous retrospective cohort of patients who underwent PFA using Journey PFA prosthesis with an asymmetric trochlear component, performed between June 2007 and July 2016 at a non-designer centre. The Patient Reported Outcome Measures and patient satisfaction questionnaires were collected for final evaluation.ResultsA total of 103 PFA performed on 79 patients were evaluated. Median age at the time of surgery was 58 years (range 42 to 78 years); the mean follow-up period was 6 years (range 2 to 11 years). Four knees were revised to Total Knee Arthroplasty for reasons not related to the implant. The cumulative survival estimated by the Kaplan–Meier method was 94.3% (95% confidence interval: 88.4%–100%). There were statistically significant improvements in functional outcome scores.ConclusionThis series of patients who underwent PFA with the asymmetric trochlear component has shown promising mid-term results with no implant-related complications.  相似文献   
53.
This work shows the sensing performance of conjugated microporous polymer (CMP) tubes. Aligned tubular CMP films (CMP‐AT) are synthesized by a template method. The Sonogashira coupling of tetra(4‐ethynyl)phenylethylene with 1,4‐diiodobenzene in the cylindrical pores of anodic aluminum oxide (AAO) plates and the etching of templates result in the CMP‐AT films. Due to the tetraphenylethylene moieties in the materials, the CMP‐AT films show aggregation‐induced emission (AIE). Based on emission‐quenching behavior, the sensing performance of CMP‐AT films toward model explosives, nitrotoluenes, is studied. The CMP‐AT films having longer CMP tubes with thinner wall thickness show better sensing performance with the Stern–Volmer constant (Ksv) values up to 92 400 M?1 toward 2,4‐dinitrotoluene. The reduced diffusion pathway of substrates by the thin wall of the CMP tubes is critical for the AIE quenching‐based sensing of nitrotoluenes. These observations indicate that the functionality of CMP materials can be further enhanced by their morphological engineering. Due to the chemical stability of CMP materials, the CMP‐AT‐5 film can be recycled at least five times, maintaining the original sensing performance and tubular morphology.  相似文献   
54.
55.
Objective: High- protein diets have become increasingly popular with various touted benefits. However, the extent to which protein quantity and source affects cognitive functioning through altering postprandial amino acid profiles has not been investigated. Further, whether all protein sources are similarly anorexigenic is uncertain. The objective of this study was to determine the influence of protein level and source on Barnes maze performance, satiety and plasma amino acid levels in male Sprague-Dawley rats.

Methods: Rats were entrained to a meal-feeding schedule consisting of a 30 minutes meal, equivalent to 20% of average daily intake, one hour into the dark phase then ad libitum access to food for 5 h. On test days, rats received one of three isocaloric diets as their first meal, hereafter referred to as Egg White (EW), Wheat Gluten (WG), or Basal, and then were measured for cognitive performance, feeding behavior, or plasma amino acid levels via jugular catheter. Percentage energy from protein was 35% for both EW and WG and 20% for Basal with equal amounts provided by EW and WG proteins.

Results: Rats provided EW performed similarly to Basal on the Barnes maze, whereas WG performed worse. EW increased satiety, whereas WG reduced satiety relative to Basal. Both EW and WG increased postprandial concentrations of large neutral and branched chain amino acids relative to Basal, but in EW, concentrations were slower to peak, and peaked to a higher level than WG.

Discussion: Results demonstrate the importance of protein source for cognition and satiety enhancing effects of a high-protein meal.  相似文献   

56.

Background

Venous thromboembolism (VTE) is common in cancer patients and its treatment is associated with a high risk of recurrent VTE (rVTE) and bleeding.

Objectives

To analyze data from the Comparison of Acute Treatments in Cancer Hemostasis (CATCH) trial to describe the impact of rVTE and bleeding events on health-related quality of life.

Methods

The three-level EuroQol five-dimensional questionnaire (EQ-5D) data were collected monthly for up to 7 months in patients starting anticoagulation for newly diagnosed VTE. Analyses were designed to describe the impact of rVTE and bleeding on EQ-5D scores while controlling for effects of covariates such as background and clinical variables and longitudinal changes. A repeated-measures model with specification of the variance-covariance matrix to characterize the intrapatient correlation was used to estimate the utility values. The impact of an rVTE or a bleeding event was assumed to be reflected in the utility value when it occurred within 2 weeks from a planned data collection point.

Results

Data were available from 883 patients. A total of 76 rVTE and 159 bleeding events occurred during follow-up. rVTE had a significant impact on EQ-5D scores, with a decrement of ?0.075 on the basis of our reference case (male, no metastasis, Eastern Cooperative Oncology Group score = 1, Western European), but different patients might have different decrements. Bleeding events had a smaller (nonstatistically significant) impact on EQ-5D scores.

Conclusions

This data set study has quantified the decline in EQ-5D scores associated with experiencing rVTE or bleeding events in cancer patients. These results indicate the net gain in quality of life and impact on cost-effectiveness of secondary VTE prevention.  相似文献   
57.
58.
Welding fume exposure can increase the risk of chronic obstructive pulmonary disease (COPD). The aim of this study was to evaluate the optimal grouping schemes of welding fume exposure in shipyard welders for future accurate examination of the association between welding fume exposure and COPD. Industrial hygiene records, including welding fume measurements between 2002 and 2009 were collected from a shipyard. A total of 2,360 personal welding fume measurements was compiled with a geometric mean of 1.66 mg/m3 and a geometric standard deviation of 4.02. Welding jobs were categorized into 8 groups. There were 9 working areas. To obtain the optimal grouping scheme, various grouping schemes were created using job, area, and job*area combination. To compare various grouping schemes, contrast and precision were calculated for each grouping scheme. For all measurement data, group mean ranking method created by ranking geometric means of the job*area combination into 3 groups (group mean ranking method) showed the best contrast and precision values among various grouping schemes, followed by grouping based on the job. For a subset of the data excluding job*area combinations with less than 10 measurements, grouping based on the job showed greater contrast than group mean ranking method, while for other subsets, including only repeated measurement data or further excluding job*area combinations with less than 10 measurements from the repeated measurement subset, group mean ranking method showed greater contrast than grouping based on the job. Our results showed that group mean ranking or grouping based on the job could be a candidate for the optimal grouping schemes in this shipyard. Our efforts for optimal grouping scheme may aid future cohort study to elucidate the association between welding fume exposure and COPD.  相似文献   
59.
60.

Background

The beryllium lymphocyte proliferation test (BeLPT), has become the principal clinical test for detecting beryllium sensitization and chronic beryllium disease. Uninterpretable BeLPT results can occur in a small but significant proportion of tests from poor lymphocyte growth (PG) or over proliferation of lymphocytes (OP). The clinical and laboratory causes of uninterpretable results are not known.

Methods

BeLPT data from the US Department of Energy‐supported Former Worker Screening Program were analyzed for a 10‐year period. Drivers of uninterpretable BeLPTs were investigated using multivariable models and classification techniques.

Results

Three participant attributes were significantly associated with PG, while OP showed no significant associations. Serum lot for the lymphocyte growth medium accounted for 21% of the variation in PG and 16% in OP.

Conclusion

Serum lots influence the likelihood of having uninterpretable BeLPT. To better understand uninterpretable results and possibly reduce their occurrence, additional laboratory‐related factors should be addressed.
  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