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   7124篇
  免费   16篇
  国内免费   1篇
电工技术   2篇
化学工业   108篇
金属工艺   27篇
机械仪表   5篇
建筑科学   7篇
矿业工程   2篇
能源动力   8篇
轻工业   73篇
水利工程   3篇
石油天然气   4篇
无线电   32篇
一般工业技术   55篇
冶金工业   6771篇
原子能技术   2篇
自动化技术   42篇
  2023年   2篇
  2022年   4篇
  2021年   12篇
  2020年   4篇
  2019年   2篇
  2018年   8篇
  2017年   8篇
  2016年   7篇
  2015年   10篇
  2014年   12篇
  2013年   18篇
  2012年   14篇
  2011年   15篇
  2010年   10篇
  2009年   21篇
  2008年   18篇
  2007年   24篇
  2006年   15篇
  2005年   12篇
  2004年   13篇
  2003年   23篇
  2002年   12篇
  2001年   9篇
  2000年   14篇
  1999年   228篇
  1998年   2330篇
  1997年   1294篇
  1996年   819篇
  1995年   426篇
  1994年   340篇
  1993年   424篇
  1992年   41篇
  1991年   47篇
  1990年   57篇
  1989年   51篇
  1988年   56篇
  1987年   59篇
  1986年   55篇
  1985年   39篇
  1983年   20篇
  1982年   25篇
  1981年   31篇
  1980年   61篇
  1979年   3篇
  1978年   14篇
  1977年   137篇
  1976年   279篇
  1975年   11篇
  1973年   2篇
  1955年   3篇
排序方式: 共有7141条查询结果,搜索用时 15 毫秒
61.
PURPOSE: To demonstrate a superselective intraarterial chemotherapy as a therapeutic alternative in the treatment of previously treated recurrent lymph node metastases in breast cancer. METHODS: 14 patients with recurrent lymph node metastases in cases of breast cancer were presented to be treated by intraarterial chemotherapy of 25 mg mitoxantrone/m2 over a period of 24 hours. In two patients with superclavicular lymph node involvement an intraarterial therapy could not be carried out because of a vascular connection to the anterior spinal artery. Involved lymph stations could be reached in superselective technique by side branches of the subclavian artery. Heparin coverage was given intravenously. Every patient had had surgery, radiation, systemic chemo- and hormonal therapy before and was now graded as inoperable. Therapy indication was given by local tumour-induced symptoms. RESULTS: In the 12 treated cases complete remission was seen in three, partial remission in 4, a steady state in two and a progressive disease in three. There were no complications or severe side effects. CONCLUSION: Intraarterial chemotherapy is an effective and well tolerated treatment in recurrent lymph node metastases in cases of breast cancer even if conventional therapies can no longer be used.  相似文献   
62.
63.
The author describes a patient who has a successful coronary artery bypass. Six weeks later, after a physical examination of the chest, she had unbearable sharp, stabbing pain around the incision which was not responding to nerve blocks, analgesics, nonsteroidal anti inflammatory agents, and epidural blocks. The pain was responsive to mexilitine and disappeared after three weeks of treatment.  相似文献   
64.
Traffic accidents are a well-known public health problem worldwide. In Mexico research into risk factors for motor involving vehicles accidents and their consequences has recently been taken into account. The relevant literature does not normally describe the methodological aspects involved in the collection of primary data, since most studies have used secondary data the good quality and validity of which are assumed. The paper presented seeks to discuss and share with researchers in this field, some of the methodological aspects to be considered in the attempt to recreate the scene of the accident and obtain information approximating to reality. The measurements in situ of, such traffic accident variables as injury, use of seat belt, speed and alcohol intake are discussed.  相似文献   
65.
OBJECTIVE: Retrospective study of urological complications in our series of reno-pancreatic transplants. MATERIAL AND METHODS: Between February 1983 and May 1994 our group has conducted 93 RPT, 80 of which, mean age 36 +/- 6 years (24-54 years), are studied in this paper: 57 male and 23 female with an average time in dialysis of 20 +/- 15 months (0-84 months) and diabetes evolution of 21 +/- 5 years (11-37 years). RESULTS: Actuarial annual survival of patient, renal graft and pancreatic graft has been 85%, 79% and 74% respectively. Haematuria: 25% incidence, with graft pancreatitis etiology in 16 cases, rejection in 8 and urinary fistula in 6. Urinary infection: 85% incidence, symptomatic in 23 patients (29%) and asymptomatic in the remaining cases. Dysuria, urethritis and urethral stenosis: 14 patients, all male, most with both conditions associated. Reconversion of pancreatic exocrine secretion by intestinal route was performed in 7 patients. Urinary fistula: secondary to surgery in 9 cases and rejection in 4. Etiology of one case remained unknown. In 4 cases it was resolved with conservative treatment, and with surgical correction in 8. One patient required pancreatic transplantectomy and one patient died of AMI. CONCLUSIONS: Urological complication in RPT account for a significant morbidity, urinary fistula being the one with greater repercussion on the patient and pancreatic graft survival.  相似文献   
66.
MT Massie  MJ Rohrer  JA Leppo  BS Cutler 《Canadian Metallurgical Quarterly》1997,25(6):975-82; discussion 982-3
PURPOSE: Because dipyridamole thallium (DT) scanning is a useful predictor of perioperative cardiac events, a positive results of a DT scan is frequently the basis for performing more invasive cardiac evaluation and for consideration for performing coronary revascularization procedures before performing peripheral vascular surgery. The rationale for this approach has been that the treatment of anatomically significant coronary artery disease would lower the risk of performing a subsequent vascular operation. However, the benefit of performing aggressive diagnostic and therapeutic cardiac procedures in such patients remains unproved. To examine this issue, data from patients who underwent coronary angiography because of thallium redistribution were compared with data from matched control subjects who underwent peripheral vascular operations without further cardiac evaluation. METHODS: The medical records of 70 consecutive patients who underwent coronary angiography because of the presence of two or more segments of redistribution on DT scan were reviewed and compared with 70 other patients matched with respect to age, gender, peripheral vascular operation, and number of segments of redistribution on DT scan who did not undergo additional cardiac evaluation. RESULTS: DT scans were performed on 934 preoperative peripheral vascular surgery patients to help in the assessment of operative risk. Ischemic responses, defined as two or more segments of redistribution, were observed in 297. Of these, 70 underwent cardiac catheterization and 25 underwent coronary revascularization procedures. Adverse outcomes affected 46% of the coronary angiography group and 44% of the control group (p = NS). Patients who underwent coronary angiography and were considered for myocardial revascularization had fewer cardiac events with a subsequent vascular operation than did the control subjects. However, any possible benefit from invasive cardiac evaluation was offset by the three deaths and two myocardial infarctions (MIs) that complicated the cardiac evaluation. There was no significant difference between the angiography group and the matched control subjects with respect to perioperative nonfatal MI (13% vs 9%), fatal MI (4% vs 3%), late nonfatal MI (16% vs 19%), or late cardiac death (10% vs 13%). In long-term follow-up, MIs occurred later in patients who underwent coronary angiography than the control subjects (p = 0.049), but this difference was not associated with an improvement in the overall survival rate. CONCLUSIONS: The risks of extended cardiac evaluation and treatment did not produce any improvement in either the perioperative or the long-term survival rate. For most vascular surgery patients who have a positive result of a DT scan, coronary angiography does not provide any additional useful information.  相似文献   
67.
OBJECTIVES: Market forces make it essential to know what policies and actions influence patients' reports of hospital services. No studies have examined the role of patient characteristics, labor quality and staff characteristics, nonlabor resources, managerial practices, and employee attitudes within a single investigation. METHODS: The authors collected, simultaneously, data about labor, management and service processes, nonlabor resources, and employee attitudes on 117 nonintensive medical-surgical inpatient units in 17 hospitals selected from a pool of 69 institutions within a metropolitan area by a stratified random sample. Of the 2,595 patients who agreed to participate, 2,051 (79%) completed telephone interviews regarding their experiences with physical care, education, and pain management services within 26 days of hospital discharge. RESULTS: A significant amount of variation in patients' service reports was explained (adjusted R2 = 0.41 physical care, 0.35 pain management, 0.44 education). Although the predictors varied for each service report, patient characteristics, especially those related to personal resources, had a large explanatory role. A labor assignment pattern that could explain why earlier studies found labor quality and staff characteristics to have only a weak role in the prediction of patients' service reports was noted. CONCLUSIONS: The results related to patient characteristics may indicate opportunities to improve care by confronting service design strategies that erroneously rely on a homogeneous patient population. Measurement challenges identified by this study must be addressed to determine the role of labor quantity and staff characteristics.  相似文献   
68.
1. We investigated the effect of exercise on plasma adrenomedullin, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations and studied the relationship between these peptides and haemodynamic parameters in nine patients with old myocardial infarction (MI) and in eight normal subjects. 2. The exercise protocol consisted of two fixed work loads (40 and 80 W) for 4 min each and venous blood samples were taken at rest, during each exercise stage and after exercise while monitoring the mean arterial pressure (MAP) and heart rate (HR). In MI, pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP), left ventricular end-diastolic pressure (LVEDP) and cardiac output (CO) were measured throughout exercise. 3. Adrenomedullin levels did not significantly increase with exercise. Adrenomedullin levels correlated with PAP and PCWP at rest (P < 0.05). Atrial natriuretic peptide levels correlated with PAP, PCWP and LVEDP throughout exercise (P < 0.05) but, on multiple regression analysis, PCWP correlated only with ANP (P < 0.01). Brain natriuretic peptide levels correlated with LVEDP throughout exercise (P < 0.01) and its increment correlated closely with basal BNP levels at rest (P < 0.01). 4. These results suggest that adrenomedullin does not respond to the acute haemodynamic changes of exercise, whereas ANP responds to it and PCWP is the major stimulus factor. Brain natriuretic peptide responds to exercise in proportion to the basal synthesis of BNP in patients with left ventricular dysfunction and LVEDP may play a role in increasing BNP during exercise.  相似文献   
69.
70.
Hereditary susceptibility to sarcoidosis is suggested by ethnic preponderance, familial clustering, and multigenerational involvement. The genetics of sarcoidosis cannot be adequately addressed in small samples of patients; a large-scale study with stratification for patient phenotypic differences is necessary. A study that uses both genetic marker and environmental data would be able to control for and examine different causative mechanisms. Until such a well-designed, comprehensive study is carried out, we are left with interesting patterns of disease in families and uncertain allelic associations.  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