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   1718篇
  免费   78篇
  国内免费   75篇
耳鼻咽喉   1篇
儿科学   102篇
妇产科学   19篇
基础医学   162篇
口腔科学   17篇
临床医学   178篇
内科学   494篇
皮肤病学   36篇
神经病学   51篇
特种医学   281篇
外科学   241篇
综合类   31篇
预防医学   79篇
眼科学   24篇
药学   66篇
中国医学   3篇
肿瘤学   86篇
  2023年   9篇
  2022年   9篇
  2021年   16篇
  2020年   16篇
  2019年   14篇
  2018年   24篇
  2017年   14篇
  2016年   28篇
  2015年   19篇
  2014年   27篇
  2013年   31篇
  2012年   56篇
  2011年   41篇
  2010年   47篇
  2009年   69篇
  2008年   45篇
  2007年   86篇
  2006年   39篇
  2005年   63篇
  2004年   49篇
  2003年   49篇
  2002年   43篇
  2001年   37篇
  2000年   42篇
  1999年   22篇
  1998年   87篇
  1997年   75篇
  1996年   62篇
  1995年   57篇
  1994年   47篇
  1993年   46篇
  1992年   30篇
  1991年   29篇
  1990年   37篇
  1989年   45篇
  1988年   48篇
  1987年   44篇
  1986年   38篇
  1985年   35篇
  1984年   35篇
  1983年   24篇
  1982年   24篇
  1981年   15篇
  1980年   23篇
  1979年   21篇
  1978年   13篇
  1977年   27篇
  1976年   19篇
  1975年   18篇
  1972年   7篇
排序方式: 共有1871条查询结果,搜索用时 11 毫秒
121.
BACKGROUND: Scientific and courtroom debate exists regarding the timing of onset of symptoms and the mechanism of injury in infants and children with inflicted traumatic brain injury (ITBI). OBJECTIVES: To determine the time interval between ITBI and the onset of symptoms and to explore the mechanism of ITBI. DESIGN, SETTING, AND PATIENTS: Retrospective review of all cases of pediatric ITBI admitted between January 1, 1981, and July 31, 2001, to a large academic medical center and cases admitted to 2 additional academic institutions between January 1, 1996, and August 31, 2000, and January 1, 2001, and July 31, 2001, comparing 81 cases of ITBI in which perpetrators admitted to abuse with 90 cases in which no abuse admission was made. The patients with perpetrator admissions to ITBI consisted of 53 boys (65%) and 28 girls (35%). Their ages ranged from 2 weeks to 52 months. MAIN OUTCOME MEASURES: Characteristics associated with perpetrator admissions to ITBI in children. RESULTS: Shaking was the most common mechanism of injury among all cases with perpetrator admissions: 55 (68%) of the 81 perpetrators admitted to shaking the children. Impact was not described in 44 (54%) of the 81 cases. In cases in which only impact was described, 60% (12/20) of the children showed skull or scalp injury, compared with 12% (4/32) with skull or scalp injury in the shake only group. In 52 (91%) of 57 cases in which the time to the onset of symptoms was described, symptoms appeared immediately after the abuse. In 5 cases (9%), the timing of symptoms was less clear, but they occurred within 24 hours. None of the children were described as behaving normally after the event. CONCLUSIONS: The symptoms of inflicted head injury in children are immediate. Most perpetrators admitted to shaking without impact. These data, combined with the relative lack of skull and scalp injury, suggest that shaking alone can produce the symptoms seen in children with ITBI.  相似文献   
122.
123.
OBJECTIVES: Activation of the neuroendocrine axis in congestive heart failure is of prognostic significance, and neurohumoral blocking therapy prolongs survival. The hypothesis that surgical reduction of left ventricular size and function decreases neuroendocrine activation is less established. We evaluated the neurohormonal response to left ventricular reconstruction surgery in ischemic cardiomyopathy. METHODS: Norepinephrine, plasma renin activity, and angiotensin II were measured in 10 patients before and 12 months after left ventricular reconstruction. In an additional 5 patients, brain natriuretric peptide was measured before and 3 months postoperatively. Three-dimensional cardiovascular imaging was used to assess ejection fraction and left ventricular end-diastolic volume index. RESULTS: Concurrent with improvements of New York Heart Association functional class (2.9 +/- 0.5 preoperatively vs 2.0 +/- 0.4 postoperatively, P <.001), ejection fraction (23.9% +/- 6.6% vs 36.2% +/- 6.2%, P <.01), and left ventricular end-diastolic volume index (140.8 +/- 33.8 mL/m(2) vs 90.6 +/- 18.3 mL/m(2), P <.01), considerable reductions were observed for median plasma profiles of norepinephrine (562.0 pg/mL vs 319.0 pg/mL, P <.05), plasma renin activity (5.75 microg/L/h vs 3.45 microg/L/h, P <.05), angiotensin II (41.0 ng/mL vs 23.0 ng/mL, P =.051), and brain natriuretric peptide (771.0 pg/mL vs 266.0 pg/mL, P <.05). The more plasma renin activity or angiotensin II decreased after left ventricular reconstruction, the higher was the increase in ejection fraction (R = -.745, P <.05 [plasma renin activity]; R = -.808, P <.05 [angiotensin II]). CONCLUSIONS: Surgical improvements of ejection fraction and left ventricular end-diastolic volume index by left ventricular reconstruction were accompanied by improvement of both the neuroendocrine activity and the functional status in patients with congestive heart failure. Whether this favorable neurohormonal response is predictive of an improved survival requires further evaluation.  相似文献   
124.
125.
The objective of the paper was to compare provider practices in prescribing antiretroviral (ARV) drug regimens and use of laboratory monitoring at three health care facilities and to determine whether Brazilian national guidelines are being followed. A retrospective, cross-sectional survey was employed. We selected a sequential sample of patients on ARV therapy who registered at three health care facilities in Rio de Janeiro, Brazil, during 2001. We abstracted 2001 patient visit data from medical records using standardized data forms. Provider practice was compared to the 2000 Brazil national guidelines for ARV use. Providers who prescribed recommended or acceptable regimens were considered as having conformed to guidelines. Only 2% of patient records (N=984) reported use of inappropriate regimens as defined by the Brazil 2000 national ARV guidelines. Forty-nine per cent of patients at the Evandro Chagas hospital, 17% of those at Hospital Geral, and 57% of those at Centro da Saude were prescribed recommended therapies. Twenty per cent of patients seen at the public district hospital received dual ARV therapy, an acceptable regimen at the time. Although the national guidelines do not provide recommendations on laboratory monitoring, during the 1 year study period a majority of patients had at least one CD4+ cell count (92%) or viral load measurement (86%). Providers' practices in prescribing ARV regimens at these Rio de Janeiro facilities conform to national guidelines. Physicians would benefit from Brazilian ARV guidelines which incorporate the international consensus on the frequency of laboratory monitoring appropriate for patients in resource-constrained settings.  相似文献   
126.
The release of soluble forms of CD80 provides a potentially powerful mechanism for the modulation of anti-tumor responses. In this report we investigated whether a soluble form of CD80 (sCD80) circulates in vivo and whether levels are altered in patients with hematological malignancies. Circulating sCD80 was detected by ELISA in all normal donor (0.024-0.318 ng/ml) and patient (0.02-3.75 ng/ml) blood analyzed. The majority of acute myeloid leukemia (13/17) and multiple myeloma (11/12) patients had normal sCD80 levels. Significantly elevated levels were detected in chronic lymphocytic leukemia (CLL, P = 0.0001) and mantle cell lymphoma (MCL, P = 0.0002) patients. MCL patients had the highest levels with 8/9 having levels > 0.318 ng/ml. Increased sCD80 levels in CLL were significantly associated with poor prognosis markers such as low platelet (P = 0.01) and hemoglobin (P = 0.002) levels, elevated WBC counts (P = 0.03) and expression of CD38 (P = 0.048). The immunoreactivity of the sCD80 in both normal and patient plasma was inhibited by the presence of CTLA-4-Ig, suggesting sCD80 is functional. Comparison of sCD80 and soluble CD86 levels demonstrated that these molecules were independently elevated in 39% of patients. The finding that a proportion of CLL and the majority of MCL patients contain elevated levels of sCD80 and the demonstration that sCD80 can interact with CTLA-4-Ig suggests a potential role for sCD80 in modulating anti-tumor responses during the malignant process.  相似文献   
127.
BACKGROUND: We investigated the occurrence of apoptosis during and after resolution of cardiac allograft rejection. Apoptosis could play different roles in graft survival depending on the target cells; thus, we also determined the cell types involved. METHODS: Endomyocardial biopsy specimens were evaluated during the first 6 months after transplantation as follows: group I, no current or prior rejection; group II, during an episode of moderate rejection; and group III, histologic resolution after an episode of moderate rejection. RESULTS: Groups II and III showed significantly increased apoptotic activity, indicated by increased caspase-8 and caspase-3 activity; however, activated caspase-3 was undetectable in group I. Activated caspase-3 was detected only in groups II and III. Terminal deoxynucleotide transferase-mediated dUTP nick-end labeling was detected in groups II and III but not group I and predominantly in inflammatory cells. CONCLUSIONS: Increased caspase activity and apoptosis of infiltrating cells not only occurs during acute cardiac allograft rejection but persists after histologic resolution. Thus, programmed cell death occurs beyond the period of histologic resolution and may play a role in regulation of the rejection process.  相似文献   
128.
BACKGROUND: Abusive head trauma accounts for significant morbidity and mortality in infants. We compared a Southern population of victims with those in a previous study of a Western population, which found that men, particularly fathers and mothers' boyfriends, are the most common perpetrators. METHODS: All cases of child abuse identified in a teaching hospital were prospectively reviewed for cases of abusive head trauma, and the perpetrators were identified. RESULTS: Of the 76 cases of head trauma identified, 27 met the criteria for the study. The demographics of the perpetrators closely match those of the Western group. Men are the predominant perpetrators, with fathers committing 45% and boyfriends 25% of these injuries. CONCLUSIONS: Despite the differences in study design and population demographics, men are the most common perpetrators of abusive head trauma in both populations.  相似文献   
129.
甲硝唑葡萄糖注射液细菌内毒素检查法的研究   总被引:1,自引:0,他引:1  
目的;以细菌内毒素检查法对甲硝唑葡萄糖注射液进行试验研究。方法;采用抑制或增强试验,并将细菌内毒素检查法与家兔法检测结果作对比。结果:该注射液经一定稀释后对测定无干扰。结论:细菌内毒素检查法适用于检测该注射液。  相似文献   
130.
Eleven patients with osteogenic sarcoma (9), Hodgkin disease (1), and mesenchymal sarcoma (1), were treated with 5-fluorouracil (5-FU) and cisplatin (DDP). Myelosuppression and vomiting of variable degrees occurred in all. No responses were seen.  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