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   1109篇
  免费   48篇
  国内免费   5篇
耳鼻咽喉   24篇
儿科学   31篇
妇产科学   26篇
基础医学   141篇
口腔科学   12篇
临床医学   93篇
内科学   281篇
皮肤病学   4篇
神经病学   78篇
特种医学   20篇
外科学   135篇
综合类   8篇
一般理论   1篇
预防医学   84篇
眼科学   18篇
药学   135篇
肿瘤学   71篇
  2024年   2篇
  2023年   12篇
  2022年   44篇
  2021年   86篇
  2020年   28篇
  2019年   39篇
  2018年   38篇
  2017年   30篇
  2016年   31篇
  2015年   33篇
  2014年   37篇
  2013年   50篇
  2012年   71篇
  2011年   85篇
  2010年   41篇
  2009年   40篇
  2008年   46篇
  2007年   50篇
  2006年   60篇
  2005年   56篇
  2004年   49篇
  2003年   32篇
  2002年   43篇
  2001年   11篇
  2000年   13篇
  1999年   11篇
  1998年   6篇
  1997年   3篇
  1996年   3篇
  1995年   5篇
  1994年   2篇
  1993年   4篇
  1992年   2篇
  1991年   8篇
  1990年   8篇
  1989年   7篇
  1988年   8篇
  1987年   7篇
  1986年   5篇
  1985年   5篇
  1984年   9篇
  1983年   6篇
  1982年   6篇
  1981年   4篇
  1980年   4篇
  1979年   3篇
  1978年   3篇
  1977年   4篇
  1973年   3篇
  1971年   2篇
排序方式: 共有1162条查询结果,搜索用时 15 毫秒
991.
Our objective was to derive the best glucose sensitivity factor (g-value) and the most discriminating standardized uptake value (SUV) normalized to glucose for classifying indolent and aggressive lymphomas. METHODS: The maximum SUV obtained from (18)F-FDG PET over the area of biopsy in 102 patients was normalized by serum glucose ([Glc]) to a standard of 100 mg/dL. Discriminant analysis was performed by using each SUV(100) (SUV x {100/[Glc]}(g), calculated using various g-values ranging from -3.0 to 0, one at a time) as a variable against the lymphoma grades, and plotting the percentage of correct classifications against g (g-plot) to search for the best g-value in normalizing SUV(100) for classifying grades. To address the influence of the extreme glucose conditions, we repeated the same analyses in 12 patients with [Glc] < or = 70 mg/dL or [Glc] > or = 110 mg/dL. RESULTS: SUV(100) correctly classified lymphoma grades ranging from 62% to 73% (P < 0.0005), depending on the g-value, with a maximum at a g-value of -0.5. For the subgroup with extreme glucose values, the g-plot also revealed higher and more optimal discrimination at a g-value of -0.5 (92%) than at a g-value of 0 (83%) (P = 0.03). The discrimination deteriorated at g < -1 in both analyses. The box plot for all cases using a g-value of -0.5 showed little overlap in classifying lymphoma grades. For a visually selected threshold SUV(100) of 7.25, the sensitivity, specificity, and accuracy of identifying aggressive grades were 82%, 79%, and 81%, respectively. CONCLUSION: The results suggest that metabolic discrimination between lymphoma grades using a glucose-normalized SUV from (18)F-FDG PET is improved by introducing g-value as an extra degree of freedom.  相似文献   
992.
The case of a 42-year-old woman with a persistent ganglion cyst of the dorsolateral aspect of the foot is presented. After multiple aspirations and 4 attempts at excision, the lesion degenerated into a painful, persistently draining wound with communication to the calcaneocuboid joint. The case was treated with dissection of the lesion to the joint, excision, and coverage of the defect with an extensor digitorum brevis muscle flap. The rationale for this surgical approach and the literature regarding recurrent ganglia are discussed.  相似文献   
993.
Background: Vitamin D plays pleiotropic roles in the body and hence, changes in its metabolism and distribution during starvation could play an important role in the adaptive response to famine. We aimed to identify the responses of some vitamin D metabolites to 8 d of fasting and exercise. Methods: A repeated-measures design was implemented, in which 14 male volunteers fasted for 8 d and performed an exercise test before and after fasting. Serum samples were collected on day 1 after night fasting and after 8 d of complete food restriction, before and 1 h and 3 h after exercise. Results: After 8 d of fasting, compared with baseline values, serum 24,25(OH)2D3 and 3-epi-25(OH)D3 levels significantly increased; those of 25(OH)D3 and 1,25(OH)2D3 were unaffected; and those of 25(OH)D2 decreased. Exercise on the first day of fasting induced an increase in serum 3-epi-25(OH)D3 levels, while exercise performed after 8 d of fasting induced an increase in 25(OH)D3, 24,25(OH)2D3, 25(OH)D2, and 3-epi-25(OH)D3 levels. Conclusion: Increases in 24,25(OH)2D3 and 3-epi-25(OH)D3 levels imply that fasting stimulates vitamin D metabolism. The effects of exercise on serum vitamin D metabolites, which are most pronounced after fasting and in subjects with serum 25(OH)D3 above 25 ng/mL, support the notion that fasting and exercise augment vitamin D metabolism.  相似文献   
994.

Despite the considerable amount of attention presently devoted to the high accessibility of online pornography, very little formal analyses have been carried out to show how the advent and proliferation of Internet technology has changed the prevalence of pornography use in populations. We conducted a preliminary analysis based on objective website traffic data, representing the changes in the number of (1) Internet users generally and (2) online pornography users specifically, between 2004 and 2016 in Poland. We observed a clear increase in the estimated number of people using online pornography in the analyzed period. The estimated number of general population members viewing pornography on the Internet increased over three times (310%) between October 2004 and October 2016–starting from an estimated 2.76 million in the first period to 8.54 million in the last. At the same time, we did not observe a clear increase in the percentage of Internet users who viewed online pornography in the same time period. Additionally, pornography viewership on the Internet was almost 2 times more prevalent among male (47%) than female Internet users (27%), and most popular in the 18–27 age group. Since our analysis is based on objective data, it does not share the limitations inherent in self-reports. However, our approach also has several important limitations (e.g., the analysis does not include online activity generated on mobile devices and under a private browsing mode); thus, the results should be interpreted with caution.

  相似文献   
995.

Introduction

The effect of germline BRCA mutations on the outcomes of patients with triple-negative breast cancer (TNBC) is not well understood.

Materials and Methods

The present retrospective study included women with newly diagnosed TNBC from January 1, 2004 to December 30, 2013. The demographic and tumor characteristics, genetic testing results, and outcomes were collected by a review of the patients’ medical records. The outcomes were compared between the BRCA+ and BRCA? women. Kaplan-Meier curves were plotted for survival analysis, and Cox proportional hazard regression was used to determine the predictors of recurrence-free survival.

Results

A total of 266 TNBC patients who had undergone BRCA testing were included in the final analysis. Of the 266 patients, 72 (27.0%) tested positive for a pathogenic BRCA mutation and 194 (73.0%) tested negative. BRCA+ women were more likely to be diagnosed with breast cancer at a younger age than were the BRCA? women. Mutation carriers were also more likely to undergo bilateral mastectomy and less likely to receive radiation. The 2- and 5-year overall survival in BRCA+ women was 97.1% and 83.1% and was 97.3% and 89.7% in the BRCA? women, respectively. No statistically significant difference was found in overall survival between the BRCA+ and BRCA? group. No statistically significant difference was noted in the rate of locoregional recurrence, distant recurrence, or recurrence-free survival between the BRCA+ and BRCA? women.

Conclusion

Our study has demonstrated that BRCA mutation carrier status does not affect overall survival or recurrence-free survival in patients with TNBC.  相似文献   
996.
997.
998.

Introduction

The proton pump inhibitor empirical trial, besides the analysis of symptoms, is the main method in the diagnosis of gastro-oesophageal reflux disease-related chest pain. β-Endorphin acts as an endogenous analgesia system. The aim of the study was verify whether β-endorphin plasma level is affected by omeprazole administration and influences the severity of anginal symptoms and outcome of the “omeprazole test” in patients with coronary artery disease (CAD) and chest pain of suspected non-cardiac origin.

Material and methods

Omeprazole was administered to 48 patients with CAD in a randomized, placebo-controlled, crossover study design. At the beginning of the study, and again after the 14-day omeprazole and placebo treatment, the β-endorphin plasma concentration was determined.

Results

The level of plasma β-endorphin after the administration of omeprazole was significantly greater than at the start of the study and following the placebo. Responders to omeprazole had an average lower β-endorphin plasma concentration than subjects who failed to respond to this therapy. Subjects with symptoms in class III (according to the Canadian Cardiovascular Society classification) after omeprazole administration had a greater β-endorphin plasma level than subjects in class II for anginal symptom severity.

Conclusions

Fourteen-day therapy with a double omeprazole dose significantly increases the β-endorphin plasma concentration in patients with CAD. Circulating β-endorphin does not seem to be involved in the mechanism for the “omeprazole test” outcome, although an individually different effect on pain threshold cannot be excluded.  相似文献   
999.
Body-worn kinematic sensors have been widely proposed as the optimal solution for portable, low cost, ambulatory monitoring of gait. This study aims to evaluate an adaptive gyroscope-based algorithm for automated temporal gait analysis using body-worn wireless gyroscopes. Gyroscope data from nine healthy adult subjects performing four walks at four different speeds were then compared against data acquired simultaneously using two force plates and an optical motion capture system. Data from a poliomyelitis patient, exhibiting pathological gait walking with and without the aid of a crutch, were also compared to the force plate. Results show that the mean true error between the adaptive gyroscope algorithm and force plate was −4.5 ± 14.4 ms and 43.4 ± 6.0 ms for IC and TC points, respectively, in healthy subjects. Similarly, the mean true error when data from the polio patient were compared against the force plate was −75.61 ± 27.53 ms and 99.20 ± 46.00 ms for IC and TC points, respectively. A comparison of the present algorithm against temporal gait parameters derived from an optical motion analysis system showed good agreement for nine healthy subjects at four speeds. These results show that the algorithm reported here could constitute the basis of a robust, portable, low-cost system for ambulatory monitoring of gait.  相似文献   
1000.
The aim of this study was to investigate the contralateral motor overflow in children during single-finger and multi-finger maximum force production tasks. Forty-five right handed children, 5–11 years of age produced maximum isometric pressing force in flexion or extension with single fingers or all four fingers of their right hand. The forces produced by individual fingers of the right and left hands were recorded and analyzed in four-dimensional finger force vector space. The results showed that increases in task (right) hand finger forces were linearly associated with non-task (left) hand finger forces. The ratio of the non-task hand finger force magnitude to the corresponding task hand finger force magnitude, termed motor overflow magnitude (MOM), was greater in extension than flexion. The index finger flexion task showed the smallest MOM values. The similarity between the directions of task hand and non-task hand finger force vectors in four-dimensional finger force vector space, termed motor overflow direction (MOD), was the greatest for index and smallest for little finger tasks. MOM of a four-finger task was greater than the sum of MOMs of single-finger tasks, and this phenomenon was termed motor overflow surplus. Contrary to previous studies, no single-finger or four-finger tasks showed significant changes of MOM or MOD with the age of children. We conclude that the contralateral motor overflow in children during finger maximum force production tasks is dependent upon the task fingers and the magnitude and direction of task finger forces.  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