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   3919篇
  免费   13篇
  国内免费   4篇
电工技术   3篇
综合类   9篇
化学工业   24篇
金属工艺   9篇
机械仪表   15篇
建筑科学   12篇
矿业工程   5篇
能源动力   1篇
轻工业   12篇
水利工程   4篇
石油天然气   5篇
武器工业   1篇
无线电   17篇
一般工业技术   30篇
冶金工业   3761篇
原子能技术   1篇
自动化技术   27篇
  2019年   2篇
  2018年   3篇
  2017年   3篇
  2016年   3篇
  2015年   1篇
  2014年   4篇
  2013年   11篇
  2012年   11篇
  2011年   17篇
  2010年   6篇
  2009年   18篇
  2008年   15篇
  2007年   39篇
  2006年   4篇
  2005年   19篇
  2004年   5篇
  2003年   3篇
  2002年   7篇
  1999年   138篇
  1998年   1232篇
  1997年   665篇
  1996年   454篇
  1995年   253篇
  1994年   206篇
  1993年   237篇
  1992年   29篇
  1991年   41篇
  1990年   46篇
  1989年   48篇
  1988年   37篇
  1987年   29篇
  1986年   29篇
  1985年   29篇
  1983年   3篇
  1982年   22篇
  1981年   20篇
  1980年   24篇
  1979年   1篇
  1978年   4篇
  1977年   62篇
  1976年   147篇
  1975年   1篇
  1965年   1篇
  1964年   3篇
  1962年   1篇
  1955年   2篇
  1954年   1篇
排序方式: 共有3936条查询结果,搜索用时 15 毫秒
81.
INTRODUCTION: The development of susceptibility to atrial fibrillation (AF) is a common consequence of many forms of cardiovascular disease, especially heart failure. In this study we used a sheep model of pacing-induced stable early heart failure to describe, quantify, and relate the level of susceptibility to AF to changes in structural and electrophysiologic parameters. METHODS AND RESULTS: Epicardial electrodes were implanted on the atria and right ventricles of nine sheep. The AF threshold, atrial vulnerability period, atrial effective refractory period (ERP), and interatrial conduction time were examined during control and over a 6-week period of ventricular pacing at 190 beats/min. Left atrial (LA) area and left ventricular (LV) fractional shortening were monitored using echocardiography. There were significant increases in LA susceptibility to AF (P < 0.0003), LA area (P < 0.0002), and LA ERP400 (P < 0.0002). Rate of increase in LA area was related positively to AF susceptibility (P = 0.02) and inversely to LA ERP400 (P = 0.002). LV fractional shortening decreased to approximately 50% of control value (P < 0.00001). No changes were observed in right atrial electrophysiology. CONCLUSION: In this study, susceptibility (the ability of an extrastimulus to induce AF) was rigorously measured within a predetermined format. Significant relationships were found to exist between susceptibility, certain of the observed changes in atrial electrophysiology and structure.  相似文献   
82.
With increasing life expectancy over the past 50 years, screening for treatable illness and active measures to prevent disease and promote a healthy lifestyle have become increasingly important for older patients. In general, the benefits of such efforts have become more apparent, but depend also upon general health and life expectancy of the individual. Tests for malignancies of the breast, cervix, prostate, colon, skin, and oral cavity are considered to meet screening criteria. Immunization guidelines have been recently updated, and good evidence supports the benefit of protecting older patients from influenza and pneumococcal pneumonia. Counseling on prevention of falls and injuries in the home and on the highways can help reduce the risk of accidents.  相似文献   
83.
Plasma interleukin-1 beta (Il-1 beta) interleukin-6 (Il-6) and tumor necrosis factor-alpha (TNF-alpha) concentrations were measured in 26 women with Anorexia Nervosa (AN), nine of the restricted type (AN-R) and 17 of the binge-eating/purging type (AN-BP), in 24 women with Bulimia Nervosa (BN) and in 26 healthy age- and sex-matched controls. Concentrations of the cytokines were measured at the beginning of the study before starting any treatment and then after 1 and 3 months of combined cognitive-behavioral and pharmacological therapy (fluoxetine for AN-R and AN-BP, amineptine for AN-BP and BN, and fluvoxamine for BN). Basal values of Il-1 beta, Il-6 and TNF-alpha, were the same in patients and controls and did not change during treatments, in spite of the improvement of the mental disorders. This seems to exclude the possibility that alterations of basal plasma cytokine secretion are involved in the etiopathogenesis of AN and BN.  相似文献   
84.
85.
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   
86.
In a long-term rodent bioassay evaluating the carcinogenicity of triethanolamine, there was equivocal evidence of carcinogenic activity in male B6C3F1 mice, based on a marginal increase in the number of hepatocellular adenomas and hepatoblastomas. Interpretation was complicated by the presence of Helicobacter hepaticus in selected silver-stained liver sections which also had histological evidence of karyomegaly and oval cell hyperplasia. An increase in numbers of liver tumors, as evidence of carcinogenic activity, was also noted in female mice. However, H. hepaticus was not considered a complicating factor, because the livers of the female mice did not have histological features compatible with H. hepaticus infection. A retrospective analysis of 51 liver tissue samples from the original carcinogenicity study was conducted to determine the incidence of H. hepaticus infection and to evaluate different diagnostic approaches for assessing the presence of H. hepaticus in livers lacking characteristic lesions. In an initial evaluation of seven mice with liver tumors, argyrophilic bacteria resembling H. hepaticus were observed in liver sections, associated with characteristic liver lesions of hepatocytic karyomegaly and oval cell hyperplasia. Frozen liver tissue was available from four of these mice; all were confirmed to be infected with H. hepaticus by culture and PCR. In a larger subsequent analysis using frozen liver tissues from 44 mice without characteristic hepatic lesions, H. hepaticus-specific DNA was amplified from the livers of 21 of 44 of the mice (47%), compared to 14 of 44 of the mice (32%) having H. hepaticus cultured from their frozen liver tumors. The results of H. hepaticus culture and H. hepaticus-specific PCR concurred (i.e., both positive and negative results) in 84% of the cases. Microscopic detection of immunofluorescence-labeled or silver-stained bacteria in liver sections was relatively insensitive compared to either culture or PCR detection. This study confirms the widespread prevalence of H. hepaticus in mice, its potential to confound experimental results, and the need to include diagnostic testing for H. hepaticus in a murine health monitoring program.  相似文献   
87.
OBJECTIVE: To study the effect of adjuvant chemotherapy after curative hepatic resection in patients with hepatocellular carcinoma. DESIGN: A randomized controlled trial. SETTING: A tertiary referral center. PATIENTS: During a 54-month period, 142 patients with hepatocellular carcinoma underwent hepatic resection at 1 institution. Sixty-six patients who survived the operation and had no demonstrable evidence of residual disease on ultrasonographic examination and hepatic angiographic testing at 1 month after surgery agreed to participate in the study. The median follow-up time was 28.3 months. INTERVENTION: Thirty patients received a combination of intravenous epirubicin hydrochloride (8 doses of 40 mg/m2 each at 6-week intervals) and transarterial chemotherapy using an emulsion of iodized oil and cisplatin (3 courses with a maximum dose of 20 mL each at 2-month intervals). Thirty-six patients had no adjuvant treatment. MAIN OUTCOME MEASURES: Recurrence rate and disease-free survival. RESULTS: A total of 138 courses of intravenous epirubicin was given to the 30 patients. Sixty-one courses of transarterial chemotherapy were given to only 29 of the 30 patients assigned to the treatment group, because the hepatic artery in 1 patient was thrombosed. Six patients (20%) had chemotherapy-related complications with no mortality. Twenty-three of 30 patients in the treatment group and 17 of 36 patients in the control group had recurrences (P=.01). Patients who received adjuvant chemotherapy had a higher incidence of extrahepatic metastases (11 patients vs 5 patients; P=.03). The respective disease-free survival rates at 1, 2, and 3 years were 50%,36%, and 18% for the treatment group and 69%, 53%, and 48% for the control group (P=.04). CONCLUSION: In a group of patients who underwent curative resection of hepatocellular carcinoma, postoperative adjuvant chemotherapy using the present regimen was associated with more frequent extrahepatic recurrences and a worse outcome.  相似文献   
88.
Contribution of two cases of renal adenocarcinoma in pediatric patients. Comments on the most updated and relevant aspects of epidemiology, clinical manifestations, diagnosis, treatment, prognosis and follow-up. Comparison to nephroblastoma and renal adenocarcinoma of the adult.  相似文献   
89.
Using data from the Bremen Adolescent Study, this report presents findings on the frequency, comorbidity and psychosocial impairment of social phobia and social fears among 1035 German adolescents of 12-17 years of age. The adolescents were randomly selected from 36 schools in the city and provincial government area of Bremen, Germany. Social phobia and other psychiatric disorders were coded based on DSM-IV criteria using the computerized personal interview of the Munich version of the Composite International Diagnostic Interview. Seventeen (1.6%) of the adolescents had met the DSM-IV criteria for social phobia at some time in their life. More girls than boys were diagnosed as suffering from social phobia. The incidence of the disorder increased with age. The lifetime frequency of social fears is much higher. The most common types of feared social situations were fear of doing something in front of other people, followed by public speaking. Social phobia very often co-occurred with depressive disorders, somatoform disorders and disorders caused by excessive or inappropriate consumption of substances. Over 94% of those with social phobia and 54.4% with any social fears were severely impaired in their daily life during the worst episode. Despite the high level of psychosocial impairment, only a small portion of the cases received professional help.  相似文献   
90.
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