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   5396篇
  免费   309篇
  国内免费   18篇
耳鼻咽喉   24篇
儿科学   192篇
妇产科学   91篇
基础医学   791篇
口腔科学   54篇
临床医学   604篇
内科学   1199篇
皮肤病学   93篇
神经病学   539篇
特种医学   123篇
外科学   605篇
综合类   54篇
一般理论   1篇
预防医学   561篇
眼科学   80篇
药学   408篇
中国医学   15篇
肿瘤学   289篇
  2024年   29篇
  2023年   86篇
  2022年   117篇
  2021年   233篇
  2020年   148篇
  2019年   208篇
  2018年   201篇
  2017年   148篇
  2016年   175篇
  2015年   189篇
  2014年   216篇
  2013年   282篇
  2012年   418篇
  2011年   447篇
  2010年   232篇
  2009年   193篇
  2008年   360篇
  2007年   316篇
  2006年   365篇
  2005年   321篇
  2004年   291篇
  2003年   265篇
  2002年   186篇
  2001年   27篇
  2000年   15篇
  1999年   33篇
  1998年   40篇
  1997年   30篇
  1996年   21篇
  1995年   29篇
  1994年   15篇
  1993年   11篇
  1992年   10篇
  1991年   10篇
  1990年   8篇
  1989年   11篇
  1987年   2篇
  1986年   2篇
  1984年   4篇
  1983年   4篇
  1982年   6篇
  1977年   2篇
  1976年   2篇
  1969年   1篇
  1967年   2篇
  1935年   1篇
  1934年   1篇
  1930年   1篇
  1924年   1篇
  1906年   1篇
排序方式: 共有5723条查询结果,搜索用时 15 毫秒
81.
An analysis is provided from 19,265 Physical Evaluation Board diagnoses from 10,406 Navy personnel from 1998 to 2000. The leading diagnostic categories were musculoskeletal and mental disorders as well as for subgroups of women and officers. Musculoskeletal conditions were 41.6% of the diagnoses and decreased with advancing age (42.9% for <30 years; 41.1% for 30-40 years; 37.6% for >40 years; chi2 for trend [1 df] = 26.4; p = 0.000). Mental disorders were 11.8% of the diagnoses and also decreased with advancing age (14.1% for <30 years; 10.4% for 30-40 years; 8.8% for >40 years; chi2 for trend [1 df] = 84; p = 0.000). Diagnoses for injury and poisoning (8.9%), nervous system (7.6%), and ill-defined conditions (4.7%) completed the top five categories below age 40 years, whereas circulatory disorders were evident after age 40 years. These findings suggest priorities for reducing overall medical disability losses in our active duty Navy forces.  相似文献   
82.
Thalidomide has previously been shown to have anti-angiogenic properties. More recently, clinical efficacy of this agent has been demonstrated in multiple myeloma and prostate cancer. Neuroblastoma is the most frequent solid tumor of the abdomen of childhood, yet children with this disease frequently have metastases at presentation. Such patients have a very poor prognosis with current therapies. Thus, new approaches are needed. We have previously shown that VEGF antagonists can inhibit neoangiogenesis and tumor growth in experimental neuroblastoma. In this study, we investigated the anti-angiogenic and anti-tumor properties of thalidomide in a xenograft model of human neuroblastoma. Tumors were induced in athymic mice using the human neuroblastoma cell line NGP. Intraperitoneal thalidomide (100 mg/kg/dose) or vehicle was administered beginning one week after implantation, and animals euthanized at six weeks. Thalidomide treatment did not significantly alter tumor growth as compared with controls. However, thalidomide suppressed angiogenesis, as demonstrated both by fluorescein angiography and immunohistochemical staining, and induced apoptosis of endothelial cells in neuroblastoma xenografts. Quantification of microvessel density demonstrated a significant reduction of vasculature in treated tumors (p<0.004). Thalidomide induced co-option of host vasculature, an effect noted previously after VEGF blockade. This study demonstrates that thalidomide has anti-angiogenic properties in experimental neuroblastoma.  相似文献   
83.
84.
Increased expression of CD38 on CD8(+) T cells is associated with activation of the immune system, progression of HIV disease, and death in adults. The prognostic significance of these cells in HIV-infected children, where the picture is complicated by age-related differences in CD38 expression, remains controversial. Measuring the unimodal expression of CD38 on CD8(+) T cells in adults and children by flow cytometry is best accomplished by quantitating the antigen on the cell surface. To our knowledge, this technique has not previously been reported in a pediatric population. Vertically HIV-infected children were age matched for mild (n = 26) and severe (n = 23) clinical disease. Eleven age-matched HIV-negative controls were included for comparison. Quantitation of CD38 on CD8(+) T cells was performed at baseline and 1 y later. The ages of the children in the three clinical groups did not differ significantly (p = 0.6004). HIV-infected children had significantly increased CD38 measurements in comparison with the HIV-negative controls (p = 0.0131), and the severe disease group tended to have higher measurements than the mild disease group. Increased CD38(+)CD8(+) T cells were significant predictors of death within the first year (p = 0.043). These findings support the view that increased CD38 expression on CD8(+) T cells has the same prognostic significance in pediatric as in adult HIV disease.  相似文献   
85.
86.
Atypical lipomatous tumors occur predominantly in middle-aged patients and often present as painless, slow-growing masses in the extremities. The clinical outcomes of surgically treated superficial or deep atypical lipomas of the extremities were reviewed. Thirty-one patients were included in this study. There were 16 men and 15 women, with an average age of 57 years (range, 32-87 years). The mean followup was 7 years (range, 1-28.8 years). Twenty-five tumors occurred in the lower extremity and six in the upper extremity. Sixteen patients (52%) had a recurrence at an average of 4.7 years after resection. Twelve (39%) patients required additional surgical procedures to treat their tumor. Occurrence of a deep lesion and positive margins at the time of the initial surgery correlated closely with the rate of recurrence and need for additional surgical treatment. Dedifferentiation to high-grade liposarcoma developed in four (13%) patients. Atypical lipomas have a high propensity for local recurrence and a potential for malignant dedifferentiation. Patients with atypical lipomas require careful evaluation, complete surgical excision when possible, and close clinical followup extending beyond 5 years.  相似文献   
87.
Concrete, highly imageable words (e.g. banana) are easier to understand than abstract words for which it is difficult to generate an image (e.g. justice). This effect of concreteness or imageability has been taken by some as evidence for the existence of separable verbal- and image-based semantic systems. Instead, however, effects of concreteness may result from better associations to relevant contextual representations for concrete than for abstract words within a single semantic system. In this study, target words of high and low imageability were preceded by supportive (related) or non-supportive (unrelated) context words. The influence of contextual support on the imageability effect was measured by recording event-related brain potentials (ERPs) to the high and low imageable target words in both context conditions. The topographic distributions of the ERPs elicited by the high versus low imageable target words were found to be different, and this effect was independent of contextual support. These data are consistent with the idea that distinct verbal- and image-based semantic codes exist for word representations, and that as a result, concrete words that are highly imageable can be understood more easily.  相似文献   
88.
Objective: To present our experience with 14 cases of fetal intracranial hemorrhage (ICH).

Methods: Cases of fetal ICH detected in our institution between 2005 and 2016 by ultrasonography. Maternal characteristics, ultrasound and MRI findings, and postnatal outcome were noted.

Results: Twelve cases (86.7%) were identified during a third trimester routine scan at a median gestational age of 30.6 weeks. The ICH was classified as Grade 2 in two cases, Grade 3 in three cases, and Grade 4 in nine cases. Nine cases were bilateral and five were unilateral (four left/one right). The 11 MRI available confirmed grade and location and, in six cases (54.5%), added new findings. There were six terminations of pregnancy, one intrauterine fetal death and seven babies born alive. These were followed up for 28 months (range 3–96). Some grade of neurologic impairment was observed in five children (71.4%, one Grade 3/four Grade 4), mainly mild to moderate motor sequelae.

Conclusion: Diagnosis of fetal ICH is amenable to antenatal US. Most of the cases identified are of high grade and usually detected during the third trimester. MRI is a valuable complementary tool in evaluating ICH. Conversely to that previously reported, postnatal survival is high but it entails the risk of adverse neurologic outcome in most neonates.  相似文献   

89.

Background

Burnout is prevalent among pediatric residents, and reducing burnout is a priority for pediatric residency programs. Understanding residents’ personal circumstances, including relationship satisfaction and perceived work-life conflict, may identify novel determinants of burnout.

Objectives

To describe intimate partner relationships among pediatric residents and examine associations among relationship satisfaction, work-life factors, and burnout.

Methods

We identified 203 partnered residents (married or in a self-identified committed, ongoing relationship) from a cross-sectional survey of 258 residents in 11 New England pediatric programs (response rate 54% of 486 surveys distributed), conducted from April through June of 2013. We analyzed associations among relationship satisfaction, work-life factors, and burnout using multivariable regression. Burnout was measured with the brief Maslach Burnout Inventory, and relationship satisfaction with the validated Relationship Assessment Scale.

Results

Burnout was reported by 40.9% of partnered respondents. The vast majority of partnered residents (n?=?167; 85.2%) reported high relationship satisfaction. Lower relationship satisfaction was not associated with burnout. Approximately half of the respondents (n?=?102; 51.5%) reported being satisfied with life as a resident. When controlling for common stressors, such as sleep deprivation, work-life measures associated with burnout included frequent perceived conflicts between personal and professional life (adjusted odds ratio, 4.35; 95% confidence interval, 1.91–9.88) and dissatisfaction with life as a resident (adjusted odds ratio, 11.74; 95% confidence interval, 4.23–32.57).

Conclusion

Low relationship satisfaction and common work-life stressors were not associated with burnout among partnered pediatric residents. However, perceived work-life conflict and dissatisfaction with resident life were strongly associated with burnout and are targets for residency programs seeking to ameliorate burnout.  相似文献   
90.
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