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   4219篇
  免费   244篇
  国内免费   34篇
耳鼻咽喉   19篇
儿科学   112篇
妇产科学   101篇
基础医学   563篇
口腔科学   101篇
临床医学   569篇
内科学   711篇
皮肤病学   59篇
神经病学   298篇
特种医学   226篇
外科学   483篇
综合类   76篇
一般理论   12篇
预防医学   489篇
眼科学   52篇
药学   305篇
中国医学   1篇
肿瘤学   320篇
  2023年   15篇
  2022年   26篇
  2021年   63篇
  2020年   43篇
  2019年   80篇
  2018年   96篇
  2017年   79篇
  2016年   90篇
  2015年   98篇
  2014年   141篇
  2013年   201篇
  2012年   272篇
  2011年   267篇
  2010年   187篇
  2009年   161篇
  2008年   276篇
  2007年   311篇
  2006年   254篇
  2005年   285篇
  2004年   255篇
  2003年   257篇
  2002年   220篇
  2001年   54篇
  2000年   29篇
  1999年   45篇
  1998年   75篇
  1997年   81篇
  1996年   63篇
  1995年   61篇
  1994年   48篇
  1993年   50篇
  1992年   24篇
  1991年   12篇
  1990年   19篇
  1989年   21篇
  1988年   26篇
  1987年   26篇
  1986年   20篇
  1985年   28篇
  1984年   28篇
  1983年   12篇
  1982年   23篇
  1981年   11篇
  1980年   13篇
  1979年   5篇
  1978年   10篇
  1977年   3篇
  1976年   6篇
  1975年   12篇
  1970年   4篇
排序方式: 共有4497条查询结果,搜索用时 15 毫秒
911.
Muitidrug resistant tuberculosis has shown an alarming increase and this assumes added importance in view of the increasing number of HIV infected patients. This article reviews the biomechanism of resistance and discusses the present stategies that are available and recommended to tackle the rising incidence of tuberculosis due to resistant mycobacteria.KEYWORDS: Antitubereular drugs, Drug resistance, Mycobacterium tuberculosis  相似文献   
912.
OBJECTIVE: To estimate prevalence of xerophthalmia and to assess dietary intake of vitamin A in Indian children aged under 6 y. DESIGN: Cross sectional study. STUDY SETTING: Urban slums under Urban Health Centre affiliated to Department of Preventive and Social Medicine, Government Medical College, Nagpur, India. PARTICIPANTS: The study included 1094 all children under 6 y of age, from two randomly selected urban slums. METHODS: Xerophthalmia was diagnosed on the basis of ocular signs and symptoms (WHO recommendations). Dietary intake of vitamin A was assessed by using one year recall method recommended by International Vitamin A Consultative Group. RESULTS: Prevalence of xerophthalmia was estimated to be 8.7%. Nine hundred and ninety-five (90.9%) study subjects were identified as inhabitants consuming dietary vitamin A at below recommended levels. (UPF score < 210). Five hundred and ninety-three (54.2%) study subjects were consuming dietary vitamin A at approximately less than 200 RE/d (UPF score < 120) while 402 (36.2%) were consuming approximately 200-300 RE/d (UPF score 120-210). The prevalence of xerophthalmia was found to be decreasing as the score of usual pattern of food consumption (UPF) increased. CONCLUSIONS: Children with a dietary intake represented by a UPF score of less than 120 were at high risk of developing xerophthalmia, whereas, those consuming vitamin A equal to a UPF score greater than 120 were at comparatively less risk despite being below the recommended levels.  相似文献   
913.

Background

Fractures of the proximal humerus are common and most often treated non-operatively. However, long-term follow-up studies focusing on functional results and quality of life in patients after this type of fracture are scarce. The primary aim of this study is to report the long-term functional and quality of life outcome in patients with a proximal humeral fracture.

Materials and methods

A retrospective analysis of all consecutive patients undergoing non-operative treatment for a proximal humeral fracture in a level 2 trauma centre between January 2000 and December 2013 was performed. A database consisting of all relevant demographic, patient and fracture characteristics was created. Subsequently, a questionnaire containing the DASH (Disabilities of the Arm, Shoulder and Hand) score, EuroQol-5D (EQ-5D), VAS (visual analogue scale) score, and subjective questions was sent to all patients.

Results

A total of 410 patients (65 male, 345 female) were included for analyses. Average follow-up was 90 ± 48 months. DASH-scores <15 were considered as good. A median DASH-score of 6.67 [0.83–22.50] was found. A significant lower DASH-score was seen in patients under the age of 65 compared to older patients (p < 0.001). In comparison to an age-matched general Dutch population, Health related Quality of Life (HrQoL) on the EQ-us was not significantly worse in our study population (difference 0.02). Strong (negative) correlation was found between DASH-score and VAS-score, and DASH-score and HrQoL, respectively ρ = ?0.534 and ρ = ?0.787.

Conclusion

Long-term functional and quality of life outcomes are good in most patients after proximal humeral fractures, but negatively correlated to each other.

Level of evidence

Level III.
  相似文献   
914.
915.

Objective

The purpose of this study was to identify factors associated with mental health (MH) problems in prostate cancer (PC) survivors. Toward this end, we evaluated (1) differences in the prevalence of MH problems between PC survivors and age-matched men from the general population (GenPop) and (2) correlates of MH in PC survivors and the GenPop.

Methods and materials

In this observational case-control study, we age-matched PC survivors (n = 644, alive≥5 y after diagnosis of a stage I–IV carcinoma) recruited from Dutch community hospitals (Patient Reported Outcomes Following Initial treatment and Long-term Evaluation of Survivorship registry) with GenPop peers (n = 644) selected from a population-based sample recruited in general practices (NIVEL). MH was operationalized using the 5-item Mental Health Inventory of the Short Form Health Survey (SF-36). Potential correlates of MH included sociodemographic characteristics, health-related quality of life scores, and clinical characteristics (PC survivors only). We used analysis of (co)variance and chi-square tests to address the 2 research questions.

Results

We observed clinically relevant MH symptoms in 14% of the PC survivors and 6% of the GenPop controls (P<0.01, odds ratio = 2.45 [1.66–3.62]). The most important correlates of lower MH scores in the PC survivors were being widowed, a lower educational level, lower general health perceptions, more bodily pain and urinary bother, and less sexual satisfaction. The most important correlates of lower MH scores in the GenPop were as follows: lower general health perceptions, more role limitations because of physical problems, and more bodily pain.

Conclusions

Our results indicate that long-term PC survivors have poorer MH, as assessed by the 5-item Mental Health Inventory questionnaire, than men of a comparable age from the GenPop without a history of PC. Attention to potentially modifiable factors associated with MH problems in PC survivors, such as urinary function and its related bother, bodily pain, and sexual satisfaction, may help to prevent or limit MH problems in this survivor population.  相似文献   
916.
917.
918.
Summary The Aspergillus nidulans pyruvate kinase gene was isolated by heterologous hybridization using the corresponding yeast gene as a probe. A 2.9 kb EcoRI/BamHI fragment, which exclusively hybridized to the yeast gene, was subcloned in pBR322. This clone was used to transform an A. nidulans pkiA deletion mutant to PKI+. The analysis of transformants with respect to the kind of integration revealed about 80% homologous integration – 55% by a double cross-over event (type III integration), 25% by a single cross-over event (type I integration). Type II transformants (20%) that arise by non-homologous integration have not been further characterized with respect to the sites of integration.A direct correlation between the number of copies of the gene integrated into the genome and the measured pyruvate kinase activity was found after growth on a glycolytic carbon source. From this, it was concluded that the 2.9 kb EcoRI/BamHI fragment contains the complete pyruvate kinase structural gene, including the promoter region.However, after growth on a gluconeogenic carbon source, the regulation of gene expression was found to be disturbed. On acetate an increase in activity per gene copy (0.2 IU) was found in the transformants, as compared with wild-type levels. It is suggested that the pyruvate kinase gene is regulated by negative control, and that some sequences involved in this regulation are missing in the cloned fragment.Abbreviations ATP Adenosinetriphosphate - MM Minimal medium - PEP Phosphoenolpyruvate  相似文献   
919.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is known for inducing cortical atrophy in the rat thymus. The present study was conducted to provide ultrastructural evidence for the cortical epithelium to be a target for TCDD in vivo. Juvenile male Wistar rats were orally intubated once with either 50 or 150 g/kg TCDD and killed 4 or 10 days thereafter. Major changes were found in the cortical thymic epithelium. First, a relative shift occurred from pale to darker cortical epithelial cell types, as judged by their nuclear and cytoplasmic electron density. This effect was most prominent at 10 days after exposure to 150 g/kg TCDD. The increased electron density of the cortical epithelium indicates an altered state of cellular differentiation. Secondly, at the 150 g/kg dose level focal epithelial cell aggregates were seen both at day 4 and day 10 after administration. This aggregation may either be compound induced or represent a secondary event to the collapse of the thymic stroma. Thirdly, increased vacuolation of cortical epithelial cells was apparent. This effect is interpreted as a consequence rather than a cause of thymocyte depletion from the cortex. This study indicates that TCDD exposure affects the cortical epithelium of the rat thymus at a high dose level. Electron microscopy reveals that the differentiation of epithelial cells is altered. In addition, epithelial cell aggregates are formed.  相似文献   
920.
We studied the relationships of the dendrites of ventral striatomesencephalic projection neurons with the compartmental structure of the ventral striatum, as revealed by enkephalin immunohistochemistry. Lightly fixed slices were employed in which Lucifer yellow was intracellulary injected into neurons that were retrogradely labelled following Fast Blue injections in the ventral tegmental area. Double immunohistochemical staining was carried out using antisera to Lucifer yellow and Leu-enkephalin. Most of the 226 injected cells were located in the core region of the nucleus accumbens. All these neurons were of the small- to medium-sized spiny type. The dendritic arborizations of over 90% of the cells remained within the compartment in which the parent cell bodies resided. The dendrites of most of these neurons abutted the border of the compartment, whereas a smaller number of neurons had dendrites that were distant from any compartmental boundary. The dendrites of fewer than 10% of the neurons crossed the borders of compartments. Only a few cells were injected in the shell region of the nucleus accumbens. None of these neurons extended its dendrites into the core region of the nucleus or into the territory of the clusters of small cells which characterize the shell. The present results demonstrate that the dendrites of the great majority of ventral striatomesencephalic neurons comply with the boundaries of ventral striatal enkephalin compartments. Together with the results of previous studies showing that such compartments are selectively innervated by thalamic and cortical afferents, and have outputs to different areas in the ventral mesencephalon, the present data suggest the existence of discrete channels through the ventral striatum.  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