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   3879篇
  免费   254篇
  国内免费   8篇
耳鼻咽喉   46篇
儿科学   150篇
妇产科学   114篇
基础医学   551篇
口腔科学   189篇
临床医学   282篇
内科学   944篇
皮肤病学   153篇
神经病学   206篇
特种医学   233篇
外科学   583篇
综合类   33篇
一般理论   2篇
预防医学   273篇
眼科学   24篇
药学   169篇
中国医学   21篇
肿瘤学   168篇
  2023年   14篇
  2022年   30篇
  2021年   88篇
  2020年   66篇
  2019年   87篇
  2018年   95篇
  2017年   73篇
  2016年   83篇
  2015年   85篇
  2014年   93篇
  2013年   136篇
  2012年   148篇
  2011年   182篇
  2010年   133篇
  2009年   112篇
  2008年   167篇
  2007年   174篇
  2006年   174篇
  2005年   141篇
  2004年   157篇
  2003年   138篇
  2002年   134篇
  2001年   118篇
  2000年   129篇
  1999年   100篇
  1998年   74篇
  1997年   69篇
  1996年   71篇
  1995年   56篇
  1994年   41篇
  1993年   37篇
  1992年   82篇
  1991年   66篇
  1990年   70篇
  1989年   74篇
  1988年   96篇
  1987年   68篇
  1986年   76篇
  1985年   67篇
  1984年   42篇
  1983年   38篇
  1982年   23篇
  1981年   25篇
  1979年   19篇
  1978年   22篇
  1977年   16篇
  1975年   13篇
  1974年   13篇
  1972年   20篇
  1971年   18篇
排序方式: 共有4141条查询结果,搜索用时 15 毫秒
51.
We conducted a multicentre study, divided into a retrospective and a prospective portion. The retrospective study evaluated osteoporotic hip fractures that occurred during 2002. The prospective study evaluated osteoporotic hip fractures that occurred during May 2003. The study was conducted in 77 hospitals in Spain and comprised patients 60 years of age and over. In the retrospective study we registered 13,195 hip fractures. Of the patients, 74% were women and 26% were men. The mean age was 80.7+/-8.4 years. The average incidence was 6.94+/-0.44 hip fractures per 1,000 inhabitants/year (95% CI, 6.07-7.82). In the prospective study, we registered 1,399 hip fractures. This represents a monthly incidence of 0.60+/-0.04 hip fractures per 1,000 inhabitants/year (95% CI, 0.51-0.69). Of the subjects, 74% were women and 26% were men. The mean age was 81.4+/-8.1 years. Using these data, we calculated the average annual prevalence in 2003 to be 7.20 fractures per 1,000 inhabitants. Thirty-three percent had previously suffered a hip fracture. Prior to the fracture, only 18% had received medical treatment for osteoporosis. After discharge from the hospital, only 26% were receiving pharmacological treatment for osteoporosis.  相似文献   
52.
Concentrations of 16 elements from 14 serpentinitic samples from Basilio and Cantel petroleum fields were obtained by instrumental neutron activation analysis (INAA): Cr, Co, Ni, La, Nd, Sm, Eu, Gd, Tb, Ce Yb, Lu, Rb, Cs, Hf and Th. Relative INAA was performed using certified reference materials and laboratory standards. Average elemental concentrations showed that the ophiolites have a basic character, suggesting the use of a well-logging method designed for volcano-sedimentary petroleum fields.  相似文献   
53.
BackgroundFemoral intramedullary nailing is currently one of the most frequent surgical treatments for extracapsular hip-fracture fixation. Cutting-out of the lag screw is the main complication of this technique, but only few studies have approached the cutting-out focussed on femoral nailing. The aim of this study was to confirm in patients treated with intramedullary nailing not only with regard to previous reports about the association of cutting-out with technical factors, but also with regard to clinical factors not previously studied.MethodsCase–control study of all patients sustaining a cut-out of the femoral nail was carried out and a control sample was randomly selected among all extracapsular hip-fracture patients during the study period (2005–2008). All clinical and technical variables were collected from medical records. Orthopaedic Trauma Association (AO/OTA) fracture classification, Singh Osteoporosis Index of the contralateral hip and the American Society of Anaesthesiology (ASA) criteria for preoperative clinical status were used. Statistical assessment included bivariant analysis and multivariant logistic regression analysis.ResultsA total of 916 hip-fracture cases were treated in the study period: 33 of them (3.6%) were identified as suffering cutting-out, and 315 controls fulfilling inclusion criteria were also recruited. No statistical differences were found in age, sex or other socio-demographic variables between the two groups. Bivariant analysis showed significant differences between groups in technical variables (tip-apex distance, suboptimal placement of lag screw, fracture diastasis, inadequate fixation quality and distal static locking) and in clinical variables (osteoporosis severity, right hip affected, better previous ability for walking and better preoperative ASA status). Multivariant logistic regression analysis showed significant association only for tip-apex distance and inadequate fixation quality. Differences in distal static locking were close to statistical significance.ConclusionsThe strongest predictor of cutting-out in femoral nailing is tip-apex distance. This study suggests that distal static locking and other clinical conditions play an important role in this fixation failure.  相似文献   
54.
Summary We report an unusual case of bilateral anterior shoulder dislocation and right greater tuberosity fracture, following electric shock. Previously reported cases were bilateral fracture dislocations. The patient was treated by closed reduction of both dislocations followed by immobilization for 3 weeks and subsequent rehabilitation, with an excellent result.  相似文献   
55.
Guest J  Herrera LP  Qian T 《Spinal cord》2006,44(3):135-142
STUDY DESIGN: Case report. OBJECTIVE: Report rapid neurological changes in a complete tetraplegic following a cell injection procedure. SETTING: Beijing, China. METHODS: ASIA/IMSOP neurological scale. Immunostaining of cell cultures. Cellular transplantation to effect functional restoration following spinal cord injury (SCI) has been hypothesized to cause improvements through axonal regeneration, increased plasticity, or axonal remyelination. Several human trials are in preliminary phases. We report a rapid improvement in motor and sensory functions in the segment adjacent to the level of complete SCI within days following cellular transplantation of cultured fetal olfactory bulb-derived cells. The patient was an 18-year-old C3 ASIA A complete tetraplegic 18 months post-injury who had been neurologically stable for more than 6 months. RESULTS: Within 48 h of cell transplantation, the patient improved one ASIA motor grade in the left elbow flexors and began to show right wrist extensor function. Descent of the sensory level occurred within 4 days and then the rate of change slowed. He is now a C5 motor and C4 sensory complete tetraplegic. Cellular cultures prepared in the same facility showed viable human cells that labeled for nestin and GFAP. CONCLUSION: We hypothesize that improved transmission in intact fibers subserving the zone of partial preservation accounts for these early improvements. We emphasize the need for further independent analysis of the outcomes of this and other preliminary cell transplant studies.  相似文献   
56.
Impact of clinical history on fracture detection with radiography   总被引:3,自引:0,他引:3  
The effect of knowledge of localizing symptoms and signs in the detection of fractures was studied. Forty radiographs of the extremities were examined twice by seven radiologists; the sessions were separated by 4 months. In 26 cases, a subtle fracture was present; 14 cases were normal. In half of the cases at each session, the precise location of pain, tenderness, or swelling was provided. The observer was asked to determine if the case was normal or abnormal (provide the exact location of the fracture) and to indicate the degree of confidence in the diagnosis. Responses were converted to a numeric scale for analysis. Analysis of receiver operator characteristic parameters indicates that clues regarding location of trauma facilitate detection of fractures. The improvement is based largely on an increased true-positive rate without an increased false-positive rate, regardless of the decision criteria of the radiologist (overall willingness to "overread" or "underread"). This has direct clinical applicability and reinforces the plea of radiologists for precise clinical information.  相似文献   
57.
Proliferative fasciitis: ultrastructure and histogenesis   总被引:1,自引:0,他引:1  
The ultrastructure was studied of 2 cases of proliferative fasciitis (PF) which affected the fascia and subcutaneous fat. Two basic cell types were observed in the lesions: fibroblast-like, and giant cells. The fibroblast-like cells had myofibroblastic ultrastructural characteristics. The giant cells showed a well-developed, rough endoplasmic reticulum, irregularly distributed filaments and clear lipid droplets in their cytoplasms. Ultrastructurally, the giant cells seemed to belong to a cellular line capable of synthesizing ground substances and extracellular fibers, but with a modified phenotype. A consistent feature was the presence of nodular aggregates of numerous proliferating perivascular cells. Transitional forms between perivascular, fibroblast-like, and giant cells were observed. Our hypothesis is that perivascular cells (activated pericytes) are the source of the fibroblast-like and giant cells in proliferative fasciitis.  相似文献   
58.
59.
Evans  EA; Mohandas  N 《Blood》1987,70(5):1443-1449
Micropipette aspiration tests on single erythrocytes have previously shown that the static rigidity (membrane shear modulus) of oxygenated sickle cells increased with increasing hemoglobin concentration, whereas the rigidity of normal cells was independent of hemoglobin concentration. Moreover, it was observed that after mechanical extension, sickle cells exhibited persistent deformation more frequently and to a greater extent than normal cells. To ascertain if differences in association of normal and sickle hemoglobin with the membrane could account for these observations, we measured rheologic properties of normal membranes reconstituted with sickle hemoglobin and sickle membranes reconstituted with normal hemoglobin. The static rigidity of normal ghosts reloaded with sickle hemoglobin was higher than those of either normal ghosts reloaded with normal hemoglobin or native normal cells. On the other hand, the increased rigidity of native sickle cells decreased to near-normal values following reconstitution with normal hemoglobin. Furthermore, we observed that normal ghosts reconstituted with sickle hemoglobin exhibited persistent bumps after mechanical extension, but no bumps formed on normal ghosts reconstituted with normal hemoglobin. Moreover residual bumps were not produced on sickle cells reloaded with normal hemoglobin. Since mechanical characteristics peculiar to sickle cells could be induced in normal cells by incorporation of sickle hemoglobin, and since normal characteristics could be restored to sickle cells by incorporation of normal hemoglobin, we suggest that the interaction of sickle hemoglobin with the cell membrane is responsible for augmented static rigidity of oxygenated sickle erythrocytes.  相似文献   
60.
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