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   4521篇
  免费   1篇
综合类   1篇
化学工业   17篇
建筑科学   4篇
轻工业   3篇
无线电   3篇
一般工业技术   5篇
冶金工业   4477篇
自动化技术   12篇
  2024年   1篇
  2019年   1篇
  2014年   7篇
  2013年   2篇
  2012年   3篇
  2011年   1篇
  2009年   2篇
  2006年   3篇
  2004年   1篇
  2003年   9篇
  2000年   2篇
  1999年   127篇
  1998年   1388篇
  1997年   849篇
  1996年   490篇
  1995年   269篇
  1994年   251篇
  1993年   278篇
  1992年   35篇
  1991年   49篇
  1990年   73篇
  1989年   61篇
  1988年   69篇
  1987年   63篇
  1986年   46篇
  1985年   35篇
  1984年   1篇
  1983年   8篇
  1982年   12篇
  1981年   29篇
  1980年   44篇
  1979年   2篇
  1978年   7篇
  1977年   92篇
  1976年   203篇
  1975年   5篇
  1964年   1篇
  1955年   3篇
排序方式: 共有4522条查询结果,搜索用时 15 毫秒
51.
52.
BACKGROUND: The clinical significance of the 14 and 6 positive spikes (PS) electroencephalographic (EEG) phenomenon is not well established. This study was performed to provide further data regarding the clinical correlates of the PS, particularly attention-deficit/hyperactivity and somatic symptoms. METHODS: Diagnostic information gathered through structured interviews was compared among four groups of psychiatric inpatients aged 4-17 years who underwent an EEG examination over a 2-year period. Groups consisted of patients with: 1) 14 and 6 PS (n = 25); 2) epileptic discharges (n = 29); 3) slow-wave abnormalities (n = 23); and 4) a normal EEG group age and sex matched to the 14 and 6 PS group (n = 25). RESULTS: Attention-deficit hyperactivity disorder (ADHD) symptoms were significantly more frequent in the PS group (chi 2 = 2.96, p < .05) compared to the other three groups combined. Although somatic symptoms were not increased in the 14 and 6 PS group, anxiety symptoms tended to occur more in this group (chi 2 = 3.50, p < .06). CONCLUSIONS: The PS profile appears associated with ADHD symptoms. Possible treatment implications of this finding (e.g., use of anticonvulsants in ADHD patients with PS) need to be explored.  相似文献   
53.
PURPOSE: The CD20 antigen is expressed on more than 90% of B-cell lymphomas. It is appealing for targeted therapy, because it does not shed or modulate. A chimeric monoclonal antibody more effectively mediates host effector functions and is itself less immunogenic than are murine antibodies. PATIENTS AND METHODS: This was a multiinstitutional trial of the chimeric anti-CD20 antibody, IDEC-C2B8. Patients with relapsed low grade or follicular lymphoma received an outpatient treatment course of IDEC-C2B8 375 mg/m2 intravenously weekly for four doses. RESULTS: From 31 centers, 166 patients were entered. Of this intent-to-treat group, 48% responded. With a median follow-up duration of 11.8 months, the projected median time to progression for responders is 13.0 months. Serum antibody levels were sustained longer after the fourth infusion than after the first, and were higher in responders and in patients with lower tumor burden. The majority of adverse events occurred during the first infusion and were grade 1 or 2; fever and chills were the most common events. Only 12% of patients had grade 3 and 3% grade 4 toxicities. A human antichimeric antibody was detected in only one patient. CONCLUSION: The response rate of 48% with IDEC-C2B8 is comparable to results with single-agent cytotoxic chemotherapy. Toxicity was mild. Attention needs to be paid to the rate of antibody infusion, with titration according to toxicity. Further investigation of this agent is warranted, including its use in conjunction with standard chemotherapy.  相似文献   
54.
To examine the effects of recombinant human erythropoietin (rHuEPO) on hospital utilization, hospital costs, and Medicare reimbursements for hospital care, a longitudinal, matched cohort study was conducted using Medicare claims data of 23,806 Medicare-eligible, dialysis patients who received rHuEPO, did not have a transplant, and were alive for 18 mo or longer and 22,720 controls matched on age, sex, race, cause of ESRD, and dialysis modality. The relative odds (rHuEPO versus control) of admission for all causes and for specific causes over 9 mo, adjusted for admission in the prior 9 mo and the per patient change in total admissions, inpatient days, hospital costs, and Medicare hospital payments between the prior 9-mo period and the subsequent 9-mo period was examined. The adjusted relative odds (95% confidence interval) of admission (rHuEPO versus control) was: higher and statistically significant for all causes, 1.08 (1.03 to 1.14); seizure, 1.52 (1.28 to 1.75); vascular access revision, 1.11 (1.06 to 1.17), and heart failure, 1.17 (1.09 to 1.26); higher but not statistically significant for angina, 1.09 (0.99 to 1.20) and stroke, 1.08 (0.86 to 1.31); and lower but not statistically significant for myocardial infarction, 0.91 (0.72 to 1.10); peripheral vascular disease, 0.81 (0.60 to 1.02); anemia, 0.86 (0.56 to 1.17); and depression, 0.89 (0.37 to 1.40). The mean change per 1,000 patients in admissions was less by 38 (P = 0.03) because of fewer readmissions, and in days was 1,309 less (P < 0.001), for patients treated with rHuEPO versus controls. The mean change per patient in hospital costs was $371 less and was statistically significant (P = 0.03) and in Medicare hospital payments was $132 less but was not statistically significant (P = 0.43) for patients treated with rHuEPO versus controls. rHuEPO was associated with an increase in the probability of hospital admission (particularly admissions potentially related to adverse effects) but a decrease in readmissions, overall admissions, hospital days, and cost to hospitals in this cohort of patients surviving for 18 mo. Although not realized short term, Medicare savings from potential rHuEPO-related reductions in hospital care may be long term through future adjustments in diagnosis-related group-based hospital payment.  相似文献   
55.
The candidacy of angiotensinogen for a role in the genetic basis of hypertension is supported by the observation that plasma angiotensinogen levels track with raised blood pressure through families. In addition, transgenic mice with overexpression of a rat angiotensinogen gene develop hypertension, and knockout mice with a disrupted gene and absent angiotensinogen production develop low blood pressure. There are now two studies in populations of white European origin and one in African Caribbeans providing support for a role of the angiotensinogen gene locus in human essential hypertension.  相似文献   
56.
57.
58.
The mating pathway of Saccharomyces cerevisiae is widely used as a model system for G protein-coupled receptor-mediated signal transduction. Following receptor activation by the binding of mating pheromones, G protein betagamma subunits transmit the signal to a MAP kinase cascade, which involves interaction of Gbeta (Ste4p) with the MAP kinase scaffold protein Ste5p. Here, we identify residues in Ste4p required for the interaction with Ste5p. These residues define a new signaling interface close to the Ste20p binding site within the Gbetagamma coiled-coil. Ste4p mutants defective in the Ste5p interaction interact efficiently with Gpa1p (Galpha) and Ste18p (Ggamma) but cannot function in signal transduction because cells expressing these mutants are sterile. Ste4 L65S is temperature-sensitive for its interaction with Ste5p, and also for signaling. We have identified a Ste5p mutant (L196A) that displays a synthetic interaction defect with Ste4 L65S, providing strong evidence that Ste4p and Ste5p interact directly in vivo through an interface that involves hydrophobic residues. The correlation between disruption of the Ste4p-Ste5p interaction and sterility confirms the importance of this interaction in signal transduction. Identification of the Gbetagamma coiled-coil in Ste5p binding may set a precedent for Gbetagamma-effector interactions in more complex organisms.  相似文献   
59.
60.
OBJECTIVES: Several studies have noted the impact of socioeconomic factors on access to expensive medical care, but none of those studies controlled for self-reported health and functional status or attitudes about treatment alternatives when analyses were completed. Because these factors may be correlated with socioeconomic status, the failure to control for them may have led to bias in other studies. The authors merged data from secondary sources with telephone survey data from a national sample of 456 end-stage renal disease patients to show how estimates of the effects of socioeconomic factors change when self-reported health and functional status and attitudes about treatment are incorporated into statistical models. The authors also showed how kidney transplant rates would change if socioeconomic factors no longer influences organ allocation decisions. METHODS: Weibull proportional hazard analyses were used to show relationships between socioeconomic measures and waiting list entry and kidney transplant rates, before versus after accounting for self-reported health and functional status, attitudes about treatment, and other variables. Simulation analyses were used to estimate the number of waiting list spots and transplant operations that would move from economically advantaged to disadvantaged persons if socioeconomics no longer influenced organ allocation decisions. RESULTS: Incorporating information about health and functional status, attitudes about treatment, and other factors into the hazard models often reduced the estimated impact of socioeconomic measures on the odds of (1) being on a waiting list for a cadaver kidney transplant and (2) receiving a transplant. Simulations showed that 30 to 65 waiting list spots or transplant operations per 1,000 patients would shift from economically advantaged to disadvantaged persons if socioeconomics no longer influenced organ allocation decisions. CONCLUSIONS: Successful efforts to level the playing field would result in substantial redistributions of kidney transplants from economically advantaged to disadvantaged persons.  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