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   3880篇
  免费   269篇
  国内免费   16篇
耳鼻咽喉   72篇
儿科学   183篇
妇产科学   192篇
基础医学   526篇
口腔科学   69篇
临床医学   348篇
内科学   750篇
皮肤病学   67篇
神经病学   342篇
特种医学   169篇
外科学   582篇
综合类   51篇
一般理论   6篇
预防医学   203篇
眼科学   92篇
药学   304篇
中国医学   11篇
肿瘤学   198篇
  2023年   17篇
  2021年   59篇
  2020年   38篇
  2019年   66篇
  2018年   84篇
  2017年   58篇
  2016年   73篇
  2015年   91篇
  2014年   126篇
  2013年   138篇
  2012年   246篇
  2011年   265篇
  2010年   159篇
  2009年   151篇
  2008年   255篇
  2007年   259篇
  2006年   247篇
  2005年   231篇
  2004年   202篇
  2003年   204篇
  2002年   195篇
  2001年   24篇
  2000年   23篇
  1999年   30篇
  1998年   49篇
  1997年   41篇
  1996年   20篇
  1995年   30篇
  1994年   34篇
  1993年   23篇
  1992年   12篇
  1989年   18篇
  1988年   14篇
  1987年   13篇
  1986年   13篇
  1985年   14篇
  1984年   16篇
  1983年   23篇
  1982年   35篇
  1981年   23篇
  1980年   25篇
  1976年   13篇
  1973年   19篇
  1972年   11篇
  1968年   12篇
  1965年   11篇
  1933年   11篇
  1928年   12篇
  1923年   16篇
  1922年   12篇
排序方式: 共有4165条查询结果,搜索用时 421 毫秒
101.
102.
103.
104.
The purpose of this work was to investigate the volumetric bone mineral density (vBMD), bone microstructure, and mechanical indices of the distal radius in female patients with rheumatoid arthritis (RA). We report a cross‐sectional study of 66 middle‐aged female RA patients and 66 age‐matched healthy females. Areal BMD (aBMD) of the hip, lumbar spine, and distal radius was measured by dual‐energy X‐ray absorptiometry (DXA). High‐resolution peripheral quantitative computed tomography (HR‐pQCT) was performed at the distal radius, yielding vBMD, bone microstructure, and mechanical indices. Cortical and trabecular vBMD were 3.5% and 10.7% lower, respectively, in RA patients than controls, despite comparable aBMD. Trabecular microstructural indices were –5.7% to –23.1% inferior, respectively, in RA patients compared to controls, with significant differences in trabecular bone volume fraction, separation, inhomogeneity, and structural model index. Cortical porosity volume and percentage were 128% and 93% higher, respectively, in RA patients, with stress being distributed more unevenly. Fourteen RA patients had exaggerated periosteal bone apposition primarily affecting the ulnovolar aspect of the distal radius. These particular patients were more likely to have chronic and severe disease and coexisting wrist deformity. The majority of the differences in density and microstructure between RA patients and controls did not depend on menstrual status. Recent exposure to glucocorticoids did not significantly affect bone density and microstructure. HR‐pQCT provides new insight into inflammation‐associated bone fragility in RA. It detects differences in vBMD, bone microstructure, and mechanical indices that are not captured by DXA. At the distal radius, deterioration in density and microstructure in RA patients involved both cortical and trabecular compartments. Excessive bone resorption appears to affect cortical more than trabecular bone at distal radius, particularly manifested as increased cortical porosity. Ulnovolar periosteal apposition of the distal radius is a feature of chronic, severe RA with wrist deformity. © 2013 American Society for Bone and Mineral Research.  相似文献   
105.
The medial prefrontal cortex (mPFC) of humans and macaques is an integral part of the default mode network and is a brain region that shows increased activation in the resting state. A previous paper from our laboratory reported significantly increased firing rates of neurons in the macaque subgenual cingulate cortex, Brodmann area (BA) 25, during disengagement from a task and also during slow wave sleep [E.T. Rolls et al. (2003) J. Neurophysiology, 90, 134–142]. Here we report the finding that there are neurons in other areas of mPFC that also increase their firing rates during disengagement from a task, drowsiness and eye‐closure. During the neurophysiological recording of single mPFC cells (n = 249) in BAs 9, 10, 13 m, 14c, 24b and especially pregenual area 32, populations of neurons were identified whose firing rates altered significantly with eye‐closure compared with eye‐opening. Three types of neuron were identified: Type 1 cells (28.1% of the total population) significantly increased (mean + 329%; P ? 0.01) their average firing rate with eye‐closure, from 3.1 spikes/s when awake to 10.2 spikes/s when asleep; Type 2 cells (6.0%) significantly decreased (mean ?68%; < 0.05) their firing rate on eye‐closure; and Type 3 cells (65.9%) were unaffected. Thus, in many areas of mPFC, implicated in the anterior default mode network, there is a substantial population of neurons that significantly increase their firing rates during periods of eye‐closure. Such neurons may be part of an interconnected network of distributed brain regions that are more active during periods of relaxed wakefulness than during attention‐demanding tasks.  相似文献   
106.
It has been shown that delayed consumable rewards are discounted to a higher degree than money, which has been referred to as the “domain effect”. Until now the effects of reward type on temporal discounting (TD) have mainly been studied in adults. Although there is evidence that children with attention-deficit/hyperactivity disorder (ADHD) tend to show steeper TD of money than typically developing peers or children with autism spectrum disorders (ASD), it remains untested whether the domain effect is also seen in children with ADHD and ASD. To explore this we compared TD of children (8–16 year) with ADHD, ASD and typically developing controls with five different reward types. Seventy-two participants with ADHD, 69 with ASD and 130 controls performed two hypothetical TD-tasks: a monetary TD-task and a TD-task with one of four alternative rewards (material rewards, rewarding activities, food, social rewards). TD was seen for all reward types, but the rate of discounting was steeper for food, praise and rewarding activities compared to money, and for food and praise compared to material rewards. For the ADHD and control groups, but not the ASD group, money and material rewards were equally highly discounted. High correlations between TD of money and of activities, food and material rewards were found. In conclusion, a domain effect was observed in typically developing children, as well as in children with ADHD or ASD, although the pattern was somewhat different for ASD children. Despite this domain effect, there is also evidence for a domain-general aspect in TD.  相似文献   
107.
108.

Introduction

Cervicovaginal decubitus ulceration is a well-known complication of advanced pelvic organ prolapse (POP). There is no consensus for its management. This case series describes the outcome of using repeated vaginal packs soaked with oestrogen cream to reduce POP and promote decubitus ulcer healing. We aimed to investigate the speed of ulcer healing and endometrial safety with this regimen.

Methods

This was a retrospective study of patients with stage 3 or 4 POP and intact uterus with decubitus ulcer who were planned for surgery that included hysterectomy after ulcer healing. Vaginal packs are replaced at least biweekly—or more frequently if extruded—until ulcer resolution.

Results

Thirteen patients were studied. Mean age was 69?±?6 years and mean duration of menopause was 19?±?6 years. Nine patients had a single ulcer and four had multiple ulcers. Mean ulcer diameter was 2.8?±?1.5 cm and mean duration for ulcer healing was 26?±?14 days. Hysterectomy and pelvic floor reconstruction was performed a median of 5 (range 0–153) days after ulcer healing was first noted. Histopathological examination of the endometrium following hysterectomy showed three specimens with endocervical hyperplasia; one had concurrent proliferative endometrium, two had simple endometrial hyperplasia and another two had proliferative endometrium.

Conclusion

Oestrogen-soaked vaginal packing is a viable option for managing a decubitus ulcer in advanced POP. We document a measurable impact on the endometrium with this short-term preoperative regimen. Further research is needed to evaluate its efficacy in promoting ulcer healing and endometrial safety.
  相似文献   
109.

Background

Femoral shaft fractures are one of the most common injuries seen by surgeons in low- and middle-income countries (LMICs). Surgical repair in LMICs is often dismissed as not being cost-effective or unsafe, though little evidence exists to support this notion. Therefore, the goal of this study is to determine the cost of intramedullary nailing of femoral shaft fractures in Tanzania.

Methods

We used micro-costing methods to estimate the fixed and variable costs of intramedullary nailing of femoral shaft fractures. Variable costs assessed included medical personnel costs, ward personnel costs, implants, medications, and single-use supplies. Fixed costs included costs for surgical instruments and administrative and ancillary staff.

Results

46 adult femoral shaft fracture patients admitted to Muhimbili Orthopaedic Institute between June and September 2014 were enrolled and treated with intramedullary fixation. The total cost per patient was $530.87 (SD $129.99). The mean variable cost per patient was $419.87 (SD $129.99), the largest portion coming from ward personnel $144.47 (SD $123.30), followed by implant $134.10 (SD $15.00) medical personnel $106.86 (SD $28.18), and medications/supplies $30.05 (SD $12.28). The mean fixed cost per patient was $111.00, consisting of support staff, $103.50, and surgical instruments, $7.50.

Conclusions

Our study provides empirical information on the variable and fixed costs of intramedullary nailing of femoral shaft fractures in LMICs. Importantly, the lack of surgical capacity was the primary driver of the largest cost for this procedure, preoperative ward personnel time. Our results provide the cost data for a formal cost-effectiveness analysis on this intervention.
  相似文献   
110.
Among infertile men, a diagnosis of unilateral varicocele is made in 90% of varicocele cases and bilateral in the remaining varicocele cases. However, there are reports of under-diagnosis of bilateral varicocele among infertile men and that its prevalence is greater than 10%. In this prospective study, we aimed to examine the differentially expressed proteins (DEP) extracted from spermatozoa cells of patients with bilateral varicocele and fertile donors. Subjects consisted of 17 men diagnosed with bilateral varicocele and 10 proven fertile men as healthy controls. Using the LTQ-orbitrap elite hybrid mass spectrometry system, proteomic analysis was done on pooled samples from 3 patients with bilateral varicocele and 5 fertile men. From these samples, 73 DEP were identified of which 58 proteins were differentially expressed, with 7 proteins unique to the bilateral varicocele group and 8 proteins to the fertile control group. Majority of the DEPs were observed to be associated with metabolic processes, stress responses, oxidoreductase activity, enzyme regulation, and immune system processes. Seven DEP were involved in sperm function such as capacitation, motility, and sperm-zona binding. Proteins TEKT3 and TCP11 were validated by Western blot analysis and may serve as potential biomarkers for bilateral varicocele. In this study, we have demonstrated for the first time the presence of DEP and identified proteins with distinct reproductive functions which are altered in infertile men with bilateral varicocele. Functional proteomic profiling provides insight into the mechanistic implications of bilateral varicocele-associated male infertility.  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