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   12312篇
  免费   1078篇
  国内免费   14篇
耳鼻咽喉   106篇
儿科学   511篇
妇产科学   398篇
基础医学   1923篇
口腔科学   355篇
临床医学   1233篇
内科学   2581篇
皮肤病学   121篇
神经病学   1317篇
特种医学   548篇
外科学   1285篇
综合类   149篇
一般理论   7篇
预防医学   1104篇
眼科学   195篇
药学   853篇
中国医学   17篇
肿瘤学   701篇
  2022年   101篇
  2021年   169篇
  2020年   131篇
  2019年   195篇
  2018年   226篇
  2017年   202篇
  2016年   224篇
  2015年   239篇
  2014年   285篇
  2013年   451篇
  2012年   619篇
  2011年   720篇
  2010年   359篇
  2009年   346篇
  2008年   588篇
  2007年   545篇
  2006年   552篇
  2005年   530篇
  2004年   504篇
  2003年   455篇
  2002年   427篇
  2001年   438篇
  2000年   422篇
  1999年   400篇
  1998年   166篇
  1997年   145篇
  1996年   122篇
  1995年   130篇
  1994年   141篇
  1993年   113篇
  1992年   277篇
  1991年   288篇
  1990年   228篇
  1989年   239篇
  1988年   227篇
  1987年   185篇
  1986年   170篇
  1985年   154篇
  1984年   146篇
  1983年   116篇
  1982年   70篇
  1981年   81篇
  1979年   92篇
  1978年   76篇
  1977年   86篇
  1975年   85篇
  1974年   98篇
  1973年   63篇
  1972年   65篇
  1971年   77篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
In a retrospective study, which comprised the whole Dutch childhood population of approximately 3 million children, the authors assessed the influence of an isolated meningeal relapse, occurring as first relapse, together with some patient and treatment characteristics on prognosis in 142 children with acute lymphoblastic leukemia (ALL). Until their first relapse, patients were initially treated according to standard protocols, whereas the treatment for relapse was heterogeneous. Concerning the probability of achieving a second complete remission (CR) it appears that the duration of the first CR is the single most important prognostic factor. The duration of the first CR is also the most important factor with regard to the duration of the second CR, upon which also age and sex have a significant influence. Concerning the survival from the time of central nervous system (CNS) relapse, again the duration of the first CR appears to be the most important prognostic factor, followed by age and the institution of systemic reinduction treatment. Other factors, such as initial leukocyte count, attainment of first CR within 48 days, type of reinduction treatment, and the cerebral spinal fluid (CSF) blast count at the time of relapse, have a less important, but nevertheless significant influence on survival. The median survival from the time of CNS relapse is 25 months, the 5-year survival is 25%, whereas the ultimate survival will be less than 20%. From 90 patients who developed second or subsequent relapses, 75% experienced a bone marrow relapse during the follow-up period. From this study the authors conclude that CNS relapse in children with ALL carries a grave prognosis, which requires the institution of intensive retreatment programs.  相似文献   
53.
Cells of Escherichia coli deleted for genes that code for the transducers and all the known cytoplasmic Che proteins except CheY responded reversibly to the addition of acetate by spinning their flagellar motors clockwise. By varying growth conditions and using metabolic inhibitors and mutants deficient in acetate metabolism, this effect was shown to require acetate-CoA synthetase [acetate:CoA ligase (AMP-forming); EC 6.2.1.1], an enzyme that catalyzes the formation of acetyl-CoA from acetate by an acetyladenylate intermediate. A mutant deficient in this enzyme but retaining the chemotaxis genes was deficient for chemotaxis. Thus, acetyladenylate appears to play a role in generating clockwise rotation at the level of CheY or the motor.  相似文献   
54.
经盲肠造口顺行性结肠灌洗术可作为重度排便障碍患儿的一种治疗选择。该研究目的是报道31例有功能性便秘(n=9)、Hirschsprung病(n=2)、肛门闭锁(n=5)、脊柱异常(n=8)、肛门闭锁合并脊髓栓系综合征(n=7)患儿行盲肠造口术的4年临床经验。回顾性收集包括并发症、顺行性结肠灌洗术的应用、症状与生活质量等各方面资料。31例患儿中有30例成功地安置了盲肠造口导管。功能性便秘(P=0.01)、肛门闭锁(P〈0.01)及脊髓异常(P=0.04)患儿便秘的发生率明显降低。功能性便秘及肛门闭锁患儿的生活质量有所提高。经皮及外科置管的并发症无显性差异。对于各种原因造成排便障碍的患儿,通过盲肠造口的顺行性结肠灌洗术可使患儿的症状与生活质量得到明显改善。  相似文献   
55.
56.
A review of the literature shows adenocarcinoma of the anal canal to have a poor outcome. Radical surgery is the treatment of choice for this disease.  相似文献   
57.
We evaluated the sensitivity and specificity of positron emission tomography for diagnosis of probable Alzheimer's disease under conditions similar to those encountered in the routine clinical practice of nuclear medicine. We obtained tomographic images of regional cerebral blood flow from three groups of subjects: (1) 13 subjects, ages 69 to 84, who had probable Alzheimer's disease diagnosed by validated clinical criteria; (2) 15 subjects, ages 57 to 77, who had Parkinson's disease without dementia; and (3) 11 subjects, ages 65 to 83, who were normal. Three blinded reviewers, who had not previously seen the images, categorized them as normal, bilateral temporoparietal flow defects typical of Alzheimer's disease, or other abnormality. Consensus interpretation demonstrated sensitivity of 0.38 (5/13) and specificity of 0.88 (23/26) for identifying patients with probable Alzheimer's disease. Thus, the criterion of bilateral temporoparietal reduction in cerebral blood flow used in this study did not have sufficient sensitivity to be of clinical value. While other criteria may be developed to improve diagnostic accuracy, clinical utility can be established only by testing for validity in patients with a full spectrum of complicating neurologic and psychiatric conditions for whom diagnosis is uncertain and who are then followed longitudinally to determine clinical outcome or pathologic findings.  相似文献   
58.
The nutritional status (assessed by anthropometric indices, and biochemical and hematological variables in blood) of three groups of elderly women (aged > or = 65 years) was evaluated within the framework of the Dutch Nutrition Surveillance System. The groups were composed of women living in a nursing home (n = 51), women living in service flats and receiving their dinners from the nursing home kitchen (n = 29), and women living independently (n = 52). Mean blood levels of folate, pyridoxal 5'-phosphate, 25-hydroxyvitamin D, alpha-tocopherol, vitamin C, albumin, selenium and total cholesterol were significantly (p < 0.05) lower among nursing home women. Among these women a biochemical deficiency was frequently found for 25-hydroxyvitamin D (73%), pyridoxal 5'-phosphate (57%), vitamin C (38%), selenium (30%) and folate (28%). These nutritional risks were largely independent of each other. Since folate and pyridoxal 5'-phosphate were associated with several clinicochemical indicators, health status may be an important determining factor for this unfavorable situation. Low 25-hydroxyvitamin D concentrations were associated with limited exposure to ultraviolet radiation and nonusage of vitamin D supplements. We conclude that dietary intake variables are not the only determinants of a marginal nutritional status among nursing home women. Use of foods with a high nutrient density should be encouraged, whereas other preventive measures are needed to improve vitamin D status.  相似文献   
59.
OBJECTIVE: Multi-vessel Doppler ultrasonography and biophysical profile scoring (BPS) are used in the surveillance of growth restricted fetuses (IUGR). The interpretation of both tests performed concurrently may be complex. This study examines the relationship between Doppler ultrasonography and biophysical test results in IUGR fetuses. METHODS: Three hundred and twenty-eight IUGR fetuses (abdominal circumference < 5th percentile, elevated umbilical artery (UA) pulsatility index (PI)) had concurrent surveillance with UA, middle cerebral artery (MCA) and ductus venosus (DV) Doppler ultrasonography and BPS (fetal tone, movement, breathing, maximal amniotic fluid pocket and fetal heart rate). Patients were stratified into three groups according to their Doppler examination: (1) abnormal UA alone; (2) brain sparing (MCA-PI > 2 SD below mean for gestational age); and (3) abnormal DV (PI > 2 SD above the mean for gestational age) and BPS groups: (1) normal (> 6/10); (2) equivocal (6/10); and (3) abnormal (< 6/10). Predictions of short-term perinatal outcomes by both modalities were compared for stratification. The distribution and concordance of Doppler and BPS test results were examined for the whole patient group and based on delivery prior to 32 weeks' gestation. RESULTS: Abnormal UA Doppler results alone were observed in 109 fetuses (33.2%), brain sparing in 87 (26.5%) and an abnormal DV in 132 (40.2%). The BPS was normal in 158 (48.2%), equivocal in 68 (20.7%) and abnormal in 102 (31.1%). Both testing modalities stratified patients into groups with comparable acid-base disturbance and perinatal outcome. Of the nine possible test combinations the largest subgroups were: abnormal UA alone/normal BPS (n = 69; 21%) and abnormal DV Doppler/abnormal BPS (n = 62; 18.9%). Assessment of compromise by both testing modalities was concordant in 146 (44.5%) cases. In 182 fetuses with discordant results the BPS grade was better in 115 (63.2%, P < 0.0001). Marked disagreement of test abnormality was present in 57 (17.4%) fetuses. Of these, abnormal venous Doppler in the presence of a normal BPS constituted the largest group (Chi-square P < 0.002). Stratification was not significantly different in patients delivered prior to 32 weeks' gestation. CONCLUSION: Doppler ultrasonography and BPS effectively stratify IUGR fetuses into risk categories, but Doppler and BPS results do not show a consistent relationship with each other. Since fetal deterioration appears to be independently reflected in these two testing modalities further research is warranted to investigate how they are best combined.  相似文献   
60.
SRTR Center-Specific Reporting Tools: Posttransplant Outcomes   总被引:3,自引:2,他引:1  
Measuring and monitoring performance—be it waiting list and posttransplant outcomes by a transplant center, or organ donation success by an organ procurement organization and its partnering hospitals—is an important component of ensuring good care for people with end-stage organ failure. Many parties have an interest in examining these outcomes, from patients and their families to payers such as insurance companies or the Centers for Medicare and Medicaid Services; from primary caregivers providing patient counseling to government agencies charged with protecting patients.
The Scientific Registry of Transplant Recipients produces regular, public reports on the performance of transplant centers and organ procurement organizations. This article explains the statistical tools used to prepare these reports, with a focus on graft survival and patient survival rates of transplant centers—especially the methods used to fairly and usefully compare outcomes of centers that serve different populations. The article concludes with a practical application of these statistics—their use in screening transplant center performance to identify centers that may need remedial action by the OPTN/UNOS Membership and Professional Standards Committee.  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