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   1612072篇
  免费   126030篇
  国内免费   4147篇
耳鼻咽喉   20513篇
儿科学   51750篇
妇产科学   44834篇
基础医学   225737篇
口腔科学   41628篇
临床医学   146894篇
内科学   325887篇
皮肤病学   36224篇
神经病学   137402篇
特种医学   62633篇
外国民族医学   477篇
外科学   241554篇
综合类   34970篇
现状与发展   4篇
一般理论   655篇
预防医学   124441篇
眼科学   36381篇
药学   111988篇
  2篇
中国医学   3638篇
肿瘤学   94637篇
  2021年   15259篇
  2019年   15848篇
  2018年   21631篇
  2017年   16457篇
  2016年   18417篇
  2015年   20803篇
  2014年   29613篇
  2013年   43110篇
  2012年   59955篇
  2011年   63139篇
  2010年   36758篇
  2009年   34977篇
  2008年   57872篇
  2007年   61074篇
  2006年   61315篇
  2005年   59669篇
  2004年   56797篇
  2003年   53627篇
  2002年   51628篇
  2001年   74695篇
  2000年   75769篇
  1999年   63285篇
  1998年   19376篇
  1997年   17329篇
  1996年   17217篇
  1995年   16312篇
  1994年   14752篇
  1993年   13892篇
  1992年   46692篇
  1991年   44296篇
  1990年   42154篇
  1989年   40174篇
  1988年   36761篇
  1987年   35888篇
  1986年   33420篇
  1985年   31886篇
  1984年   24606篇
  1983年   20715篇
  1982年   13115篇
  1981年   11621篇
  1979年   21120篇
  1978年   15038篇
  1977年   12482篇
  1976年   11737篇
  1975年   11904篇
  1974年   14263篇
  1973年   13773篇
  1972年   12789篇
  1971年   11613篇
  1970年   11011篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
CONTEXT: The physician assistant profession has been moving toward requiring master's degrees for new practitioners, but some argue this could change the face of the discipline. PURPOSE: To see if there is an association between physician assistants' academic degrees and practice in primary care, in rural areas, and with the medically underserved. METHODS: Surveys were sent to 880 graduates of the first 32 University of Washington physician assistant classes through 2000. Respondents noted their academic degree at program entry and the highest degree attained at any time up to the time of survey. Relationships between practice characteristics and academic degree levels were tested by unadjusted odds ratios and logistic regression after controlling for year of graduation and sex. RESULTS: Of the 478 respondents, 54% worked in primary care, about 30% practiced in nonmetropolitan communities, and 42% reported providing care for the medically underserved. Respondents with no degree (33% of total at entry, 24% at survey) were significantly more likely than degree holders to work in primary care and nonmetropolitan areas. Respondents with no degree at program entry were significantly more likely, and those with no degree at the time of the survey were marginally more likely, to self-report work with the medically underserved. CONCLUSION: Respondents with no academic degree are significantly more likely to demonstrate a commitment to primary, rural, and underserved health care. These findings may inform the national debate about the impact of required advanced degrees on the practice patterns of nonphysician providers.  相似文献   
72.
AIMS: To establish all-cause and cause-specific death rates, and risk factors for mortality in insulin-treated diabetic individuals living in the province of Canterbury, New Zealand. METHODS: Insulin-treated diabetic subjects (n = 995) on the Canterbury Diabetes Registry were followed up over 15 years and vital status determined. Death rates were standardized and hazard regression was used to model the effects of demographic covariates on relative survival time. RESULTS: There were 419 deaths in 11 226.3 person-years of follow-up with a standardized mortality ratio (SMR) of 2.0 (95% confidence interval (CI) 1.8-2.2). Relative mortality was greatest for the group aged 0-29 years (SMR 3.0 (95% CI 2.4-3.7)). After controlling for diabetes duration and gender, a 10-year increment in age of onset was associated with a 33% decrease in relative hazard (95% CI 29-36%), indicating that excess mortality due to diabetes declines with rising age of onset. After controlling for age of onset and gender, each 10-year increment in duration of diabetes is associated with a 26% decrease in relative hazard (95% CI 24-29%), indicating that with longer survival the mortality hazard approaches the general population hazard. Relative mortalities were increased for cardiovascular, renal and respiratory disease, but not malignancy. Relative mortality from acute metabolic complications was increased in the subgroup with age of onset of diabetes < 30 years and requiring insulin within 1 year of diagnosis. CONCLUSIONS: Mortality rates are high for insulin-treated diabetic individuals relative to the general population.  相似文献   
73.
The incidence of asthma has been reported to be associated with obesity. An alternative analysis, of net change in prevalence, does not require exclusion of those with asthma at baseline. Follow-up data were obtained from 9,552 participants in the European Community Respiratory Health Survey and the Swiss cohort Study on Air Pollution and Lung Disease in Adults. Incidence of asthma was analysed by proportional hazards regression, and net changes in symptoms and asthma status by generalised estimating equations, by obesity group. Incidence and net change in ever having had asthma were greater in females than in males, and in participants who remained obese compared with those who were never obese (hazard ratio 2.00, 95% confidence interval 1.25-3.20; excess net change 2.8%, 0.4-5.3% per 10 yrs). The effect of being obese on net change in diagnosed asthma was greater in females than in males, but for net change in wheeze without a cold it was greater in males. The present results are consistent with asthma being more frequently diagnosed in females, especially obese females. These findings may help to explain the reports of a stronger association between asthma and obesity in females than in males.  相似文献   
74.
The finer branches of the biliary tree (FBBT) contain a regenerative compartment. We hypothesized that preservation of the FBBT together with its microvasculature will lead to recovery of biliary damage and prolonged preservation of bile ductules during the development of chronic liver allograft rejection. The interlobular bile ducts, portal bile ductules and extraportal biliary cells with and without microvessels were studied in sequential biopsies in five patients who fulfilled the Banff criteria of early chronic rejection (CR) (imminence group). Biopsies of CR patients (n = 12) served as controls. Biopsies were double immunostained with CD34 (microvessels) and cytokeratin 7 (biliary structures). Proliferation and proangiogenic activity were assessed with Ki67 and VEGF-A immunostaining. Severe damage of bile ducts in the imminence group did not progress to significant bile duct loss. This was associated with a high proliferative activity in all biliary structures and preservation of the microvascular compartment. VEGF-A expression was increased in all but the reperfusion biopsies. In conclusion, both regenerative activity of the FBBT and an intact microvascular compartment are associated with less damage of the biliary tree and could therefore be prerequisites for biliary regeneration.  相似文献   
75.
76.
To understand in situ behavior of osteocytes, we characterized a model of osteocytes in their native bone matrix and demonstrated real-time biologic activity of osteocytes while bending the bone matrix. Using 43 male Sprague-Dawley rats, dumbbell-shaped explants were harvested from stainless steel femoral implants after 6-12 weeks and incubated in culture medium or fixed. Sixteen specimens were used to determine bone volume density (BV/TV), volumetric bone mineral density (BMD) and histology for different implantation periods. Osteocyte viability was evaluated by L-lactate dehydrogenase (LDH) activity in 12 cultured explants. Confocal microscopy was used to assess tracer diffusion in three explants and changes in osteocyte pH of a mechanically loaded explant. From 6 to 12 weeks, explant BV/TV and volumetric BMD trended up 92.5% and 101%, respectively. They were significantly and highly correlated. Tissues were uniformly intramembranous and all bone cell types were present. Explants maintained LDH activity through culture day 8. Diffusion at 200 microM was limited to 1,209 Da. Explants appeared capable of reproducing complex bone biology. This model may be useful in understanding osteocyte mechanotransduction in the context of a physiologically relevant bone matrix.  相似文献   
77.
A fall onto the hand can be followed by ligament ruptures, bone fractures or dislocated fractures of the carpus. The diagnosis is based on history, clinical evaluation, and X-ray examination in two perpendicular planes, followed if necessary by CT scan or MRI scan. Lesions of the scapholunate ligaments cannot be definitely excluded except by arthroscopy. As well as fractures of the carpometacarpal joints, fractures involving the ring structure of the carpus or ligament ruptures between carpal bones are frequently observed, and these lead to significantly impaired biomechanics. The prognosis is poor. The discontinuity of the ring must be repaired by means of osteosynthesis and/or suturing ligaments, with the carpal bones held in place by temporary arthrodesis using K-wires. Dislocation in this region requires rapid realignment, as untreated perilunate dislocation or dislocation of the lunate bone will lead to serious secondary damage, which can only be treated by salvage operations involving loss of function. Inappropriate treatment of an injury to the heel of the hand can lead to carpal collapse.  相似文献   
78.
79.
80.
Thoraxtrauma     
Chest injuries can be sustained in isolation or in association with multiple injuries. Life-threatening complications may ensue because organs that are vital to survival of the organism are situated within the thoracic cavity. These complications include airway obstruction, tension pneumothorax, wide open pneumothorax, flail chest, cardiac tamponade and massive hemothorax. The mortality of patients hospitalized with chest injury can be as high as 10%. Clinical examination and awareness of the possibility of other injuries (high level of suspicion) are essential, and standard chest X-ray, ultrasound and thoracic computed tomography may also be needed for the diagnosis. The first part of this serial paper on the management of chest injuries focuses on anatomical aspects, pathophysiology and symptoms, but mainly on the indications for the standard diagnostic procedures and further high-tech examinations.  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