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   1190篇
  免费   63篇
  国内免费   56篇
耳鼻咽喉   2篇
儿科学   69篇
妇产科学   12篇
基础医学   148篇
口腔科学   21篇
临床医学   149篇
内科学   265篇
皮肤病学   51篇
神经病学   64篇
特种医学   299篇
外科学   46篇
综合类   23篇
预防医学   39篇
眼科学   5篇
药学   58篇
中国医学   3篇
肿瘤学   55篇
  2023年   4篇
  2021年   9篇
  2020年   9篇
  2019年   12篇
  2018年   18篇
  2017年   5篇
  2016年   8篇
  2015年   14篇
  2014年   16篇
  2013年   41篇
  2012年   31篇
  2011年   19篇
  2010年   39篇
  2009年   62篇
  2008年   23篇
  2007年   55篇
  2006年   23篇
  2005年   24篇
  2004年   12篇
  2003年   12篇
  2002年   14篇
  2001年   13篇
  2000年   19篇
  1999年   19篇
  1998年   71篇
  1997年   81篇
  1996年   103篇
  1995年   63篇
  1994年   60篇
  1993年   53篇
  1992年   18篇
  1991年   18篇
  1990年   21篇
  1989年   37篇
  1988年   38篇
  1987年   35篇
  1986年   48篇
  1985年   40篇
  1984年   11篇
  1983年   14篇
  1982年   13篇
  1981年   10篇
  1980年   11篇
  1979年   8篇
  1978年   13篇
  1977年   10篇
  1976年   13篇
  1975年   13篇
  1974年   2篇
  1973年   2篇
排序方式: 共有1309条查询结果,搜索用时 274 毫秒
81.
Weaver  DA; Hei  TK; Hukku  B; McRaven  JA; Willey  JC 《Carcinogenesis》1997,18(6):1251-1257
To establish a cell culture model for lung carcinogenesis, independent populations of the human papillomavirus 18-immortalized human bronchial epithelial cell line BEP2D were treated with high linear energy transfer radon-simulated alpha-particles, expanded and xenotransplanted into Nu/Nu mice. Six independent cell lines were established from tumors that developed from three separate radiation treatments as follows: treatment (Tx) 1 (30 cGy--two doses), H2BT, Tx 2 (30 cGy-- single dose), R30T1L, R30T2 and R30T3L, Tx 3 (30 cGy--single dose), H1ATN and H1ATBA1. Cytogenetic analysis revealed common changes in all tumor lines: loss of the Y chromosome (ch), one of three copies of ch8, one of three copies of ch14, and one of two copies of ch4p16-pter and ch11p15-pter. Analysis of polymerase chain reaction-amplified short tandem repeats of informative loci confirmed the loss of chY in all lines and loss of heterozygosity (LOH) at eight loci spanning the length of ch8 in all lines from Tx's 1 and 2. Our data support previous studies indicating the presence of tumor suppressor genes on ch8. LOH also was confirmed on ch14 at locus D14S306 in all cell lines from Tx 2 and in one of two lines from Tx 3. This region, 14q12-q13, may contain changes in one of the five known somatostatin receptor genes (SSTR1). No LOH was detected at any of the informative loci tested for on ch4 or ch11.   相似文献   
82.
Childhood tuberculosis is perceived by many as a disease of the past. Experience in a children's hospital serving a deprived population suggested that tuberculosis and other mycobacterial infections were not declining in clinical practice. Fifty three tuberculous and 11 atypical mycobacterial infections were identified between 1978 and 1992. There was no decline in tuberculosis and nine of the 11 atypical infections occurred in the last five years. Altogether 40% of cases of tuberculosis were in non-Asian children; 32% had arrived in the UK or visited family overseas in the previous year; and 38% had a history of tuberculosis contact, usually a close adult relative. Nationally, the previous decline in tuberculosis in all ages has reversed. In the local health districts in London's east end, childhood tuberculosis has also stopped declining and seems to be increasing. It is regrettable that BCG vaccination has been abolished by some districts in the UK, against current recommendations. Childhood tuberculosis is still common in the practice described here, including among children who do not fall into conventionally recognised high risk groups. Inner city dwellers and junior doctors are both highly mobile populations, adding to the risk that paediatricians, particularly those in training, may encounter tuberculosis with little or no previous experience of the condition.  相似文献   
83.
84.
85.
Multisection, dual-echo magnetic resonance (MR) transaxial images of blood vessels contain both anatomic and qualitative information about flow. Even so, the images are produced as a series of two-dimensional tomographic sections from which full visualization of connected structures is difficult. A computer algorithm was developed that automatically detects flowing blood based on pixel intensity and calculated T2 and provides reconstructed views of vessels while analyzing and displaying flow characteristics. Images of abdominal vessels, aortic aneurysms, and the heart were encoded by flow and color to demonstrate depth. In addition, these data were reconstructed to derive a more accurate assessment of patency. With this technique, transaxial images can be used to analyze flow patterns, determine patent areas, and visualize all levels of vessels in a single image.  相似文献   
86.
Background The well known global improvement of quality of life (QoL) after bilateral high frequency chronic deep brain stimulation of the subthalamic nucleus (STN DBS) in Parkinsons disease (PD) is in contrast to behavioral disturbances as observed after surgery. Indeed the impact of DBS on physical versus mental aspects of QoL in PD remains unknown. Objective To assess the influence of bilateral STN DBS on physical versus mental aspects of QoL in Parkinsons disease. Methods The results of 27 patients for the Unified Parkinsons disease Rating Scale (UPDRS), Parkinsons Disease Questionnaire 39 (PDQ39) and Short Form 36 health survey questionnaire (SF36) were compared before surgery and after 12 months of bilateral STN DBS. Results Comparing off–dopa conditions before versus 12 months after surgery, both UPDRS part II and part III significantly improved: 32.6% and 52%, respectively. UPDRS part I scores did not change significantly at 12 months. As for PDQ39, the global score significantly improved after surgery (21.1 %) as did four subscores: mobility (25.6 %), activity of daily living (34.5 %), stigma (40.1 %) and bodily discomfort (30 %). Three PDQ39 subscores, however, showed no significant changes: emotional well–being (10.7 %), social support (3.2%) and cognition (8.5 %) and one item even worsened: communication (–7.7 %). In SF36, only physical items significantly improved. Conclusion Using clinicians based rating scale, bilateral STN DBS showed significant improvement in PD patients at 12 month follow up. However, using patients self–assessment scales, the clinical benefit of STN DBS was more subtle: physical items of QoL significantly improved, whereas mental items such as emotional well–being, social support, cognition and communication showed no improvement. Our results are suggestive of a dissociation of motor and non–motor symptoms control after bilateral STN DBS in PD patients.  相似文献   
87.
OBJECTIVE: To determine whether children's food consumption is increased by the size of the group of children in which they are eating. DESIGN: Crossover study. SETTING: University based preschool. PARTICIPANTS: 54 children, aged 2.5-6.5 years. INTERVENTIONS: Each child ate a standardised snack in a group of three children, and in a group of nine children. MAIN OUTCOME MEASURES: Amount each individual child consumed, in grams. RESULTS: Amount eaten and snack duration were correlated (r = 0.71). The association between group size and amount eaten differed in the short (<11.4 min) versus the long (> or =11.4 min) snacks (p = 0.02 for the interaction between group size and snack duration). During short snacks, there was no effect of group size on amount eaten (16.7 (SD 11) g eaten in small groups vs 15.1 (6.6) g eaten in large groups, p = 0.42). During long snacks, large group size increased the amount eaten (34.5 (16) vs 26.5 (13.8), p = 0.02). The group size effect was partially explained by a shorter latency to begin eating, a faster eating rate and reduced social interaction in larger groups. CONCLUSIONS: Children consumed 30% more food when eating in a group of nine children than when eating in a group of three children during longer snacks. Social facilitation of food consumption operates in preschool-aged children. The group size effect merits consideration in creating eating behaviour interventions.  相似文献   
88.
Volumetric rendering of MR images   总被引:1,自引:0,他引:1  
The authors developed new techniques for three-dimensional display of magnetic resonance (MR) images that preserve soft-tissue definition, are fully automatic, and work with routinely used section thicknesses. MR images are segmented, selectively enhanced, and displayed by means of a volumetric rendering algorithm. These techniques were used to illustrate normal anatomy of the brain, knee, and liver. Three-dimensional rendering of balanced spin-echo images shows the ventricles and extracerebral veins and of T1-weighted images, the sulci and gyri. The large hepatic and portal vessels can be seen with these enhancement techniques. Three-dimensional views of the knee reveal articular surfaces of the tibia and clearly depict menisci and posterior and anterior cruciate ligaments. These techniques make it possible to image multiple soft tissues simultaneously while preserving the detail contained in the original images. Three-dimensional presentation of complex, overlapping anatomic regions is helpful in surgical planning and should lead to improved diagnosis.  相似文献   
89.
Digital beam attenuator technique for compensated chest radiography   总被引:1,自引:0,他引:1  
The feasibility of producing patient-specific beam attenuators for chest radiography has been investigated using an anthropomorphic phantom and a human volunteer. A low-dose test exposure is digitized, processed, and used to print a small cerium filter, which is placed in the x-ray beam near the collimator. The final radiograph is recorded on film. The technique results in relatively uniform film exposure, so that structures in all regions of the chest are simultaneously displayed with optimal film contrast. The equalized exposure improves image quality in the normally underpenetrated regions and reduces the role of cross-scatter from the lungs. The image is analogous to optical or computer-processed unsharp masking techniques, but the processing is accomplished in the x-ray beam and results in an improved exposure distribution, giving advantages that cannot be achieved with image processing techniques alone.  相似文献   
90.
The aim  of this study was to determine the frequency of body dysmorphic disorder (BDD) identified by Polish dermatologists and to evaluate the treatment modalities applied by them.
Methods  A specially designed questionnaire was distributed to 172 dermatologists. A total of 118 doctors responded (68.6%). The dermatologists were asked regarding demographic data, frequency of BDD in their everyday practice and methods of treatment they used in managing BDD patients.
Results  During the whole working period, over the half of dermatologists (64%) had observed at least one BDD patient in their practice. One fifth (20%) of the respondents observed 1 or 2 BDD cases during the past 5 years, 14% observed 3 to 5 such patients, 7% observed 5 to 10 BDD cases, and 5% of the doctors reported seeing more than 10 BDD patients within this period. Almost 18% of dermatologists were currently treating a BDD patient. Our data show that 40.7% of the respondents always ask and 28.8% often ask for a psychiatric opinion. More experienced dermatologists statistically more frequently ( P < 0.05) obtained a psychiatric opinion about their patients. Only a small group of dermatologists (15.3%) use their own pharmacological treatment. If they do so, they first use anxiety-relieving drugs and placebo.
Conclusion  BDD is a quite common disorder; however, not all dermatologists are sufficiently prepared to treat it. There is an urgent need for training of dermatologists on the effective approach to psychodermatoses.  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