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   309796篇
  免费   3726篇
  国内免费   714篇
电工技术   6194篇
综合类   560篇
化学工业   46740篇
金属工艺   10323篇
机械仪表   8821篇
建筑科学   7904篇
矿业工程   862篇
能源动力   8568篇
轻工业   31082篇
水利工程   2532篇
石油天然气   3669篇
武器工业   8篇
无线电   39702篇
一般工业技术   58459篇
冶金工业   56653篇
原子能技术   5458篇
自动化技术   26701篇
  2021年   2277篇
  2019年   2140篇
  2018年   3609篇
  2017年   3449篇
  2016年   3540篇
  2015年   2540篇
  2014年   4443篇
  2013年   14273篇
  2012年   7363篇
  2011年   10114篇
  2010年   7901篇
  2009年   9131篇
  2008年   9600篇
  2007年   9578篇
  2006年   8505篇
  2005年   7887篇
  2004年   7760篇
  2003年   7499篇
  2002年   7333篇
  2001年   7543篇
  2000年   7208篇
  1999年   7548篇
  1998年   17660篇
  1997年   12835篇
  1996年   10098篇
  1995年   7873篇
  1994年   7205篇
  1993年   6904篇
  1992年   5287篇
  1991年   5066篇
  1990年   4933篇
  1989年   4781篇
  1988年   4673篇
  1987年   3888篇
  1986年   4011篇
  1985年   4717篇
  1984年   4275篇
  1983年   4021篇
  1982年   3601篇
  1981年   3764篇
  1980年   3456篇
  1979年   3418篇
  1978年   3226篇
  1977年   3814篇
  1976年   4849篇
  1975年   2781篇
  1974年   2660篇
  1973年   2675篇
  1972年   2215篇
  1971年   1964篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
61.
62.
63.
This investigation retrospectively examined changes in marital satisfaction following stroke. The relationship between such changes and other pertinent factors were also examined, including severity of aphasia, knowledge of aphasia, number of months after stroke, and length of the marriage. The subjects were 40 spouses of patients with aphasia grouped according to severity of the aphasia (mild, moderate, severe). Spouses completed two different measures of marital satisfaction--the Marital Satisfaction Scale (MSS) and the Marital Comparison Level Index (MCLI). These measures were completed in both a prestroke (retrospective reporting) and a poststroke format to allow for change to be assessed. In addition, a Knowledge of Aphasia questionnaire was completed by the normal spouses to evaluate their understanding of the disorder of aphasia. There was a significant difference between prestroke and poststroke scores on both the MSS and the MCLI, indicating a lower level of satisfaction following the stroke. The amount of change between prestroke and poststroke MSS and MCLI scores was not related to either number of months poststroke or number of years married. Although there was no relationship between changes in prestroke and poststroke scores on the MCLI and Knowledge of Aphasia scores, there was a significant correlation between changes in these scores on the MSS and Knowledge of Aphasia scores. Hence, the more knowledge spouses had regarding aphasia, the less the negative impact the stroke had on marital satisfaction, as measured by the MSS. Results are discussed in terms of the interdisciplinary treatment needs of aphasic patients and the implications for future investigations.  相似文献   
64.
65.
66.
This study contrasted six subscales of the Brief Psychiatric Rating Scale (BPRS) to determine their sensitivity to psychosocial treatment outcome. An expanded version of the BPRS was administered to 216 clients on admission to a day program. The subscale measuring hostility and suspiciousness discriminated at intake clients who were therapeutically discharged from clients who did not complete the program and predicted discharge status after the investigators controlled for the effects of demographic variables. Significant reductions in scores were obtained on five subscales for a subset of clients to whom the BPRS was readministered before discharge. The results support the use of the expanded BPRS as an evaluative tool in psychosocial rehabilitation programs.  相似文献   
67.
BACKGROUND: Gastric sucrose permeability is a noninvasive marker that reliably increases in association with gastrointestinal injury due to use of nonsteroidal antiinflammatory drugs. Despite the effect of Helicobacter pylori infection on the gastric mucosa, in a previous study we were unable to demonstrate that H. pylori infection was associated with abnormal gastric sucrose permeability. Our goal in this study was to explore further whether H. pylori infection changed gastric permeability; therefore, we evaluated the effect of treatment of H. pylori infection on gastric permeability to sucrose and the relation of sucrose permeability to density of polymorphonuclear leukocytes. MATERIALS AND METHODS: Five hundred milliliters of a solution containing 100 gm of sucrose was ingested by the subject at bedtime. Overnight urine was collected and assayed for sucrose by high-performance liquid chromatography. Sucrose permeability was assessed both before and approximately 4 weeks after anti-H. pylori therapy. RESULTS: Seventeen asymptomatic H. pylori-infected volunteers participated; 8 were cured. Sucrose permeability was in the range commonly found in normal controls both before and after anti-H. pylori therapy (mean excretion, 76.3 mg; range, 13-171 mg). Gastric sucrose permeability correlated with the density of polymorphonulcear cell infiltration of the mucosa. Cure of the H. pylori infection was associated with a small but significant decrease in sucrose permeability (98.8 +/- 18 mg to 51.7 +/- 9.8 mg (p = .01). Sucrose permeability was greater in those with a high density of mucosal polymorphonuclear cells compared to those with lower scores (119.5 +/- 4 vs 71.4 +/- 13 for those with scores > or = 5 compared to scores < or = 4; p = .023). Failed therapy resulted in an increase in the mucosal density of polymorphonuclear infiltration and sucrose permeability (56.4 +/- 13 mg-99.7 +/- 19 mg pretreatment vs posttreatment, respectively; p = .031). CONCLUSION: H. pylori gastritis causes a small but measurable increase in gastric permeability to sucrose that may reflect epithelial transmigration of neutrophils.  相似文献   
68.
69.
70.
BACKGROUND: Elevated serum sialic acids are associated with increased cardiovascular mortality, but sialic acid levels have not been studied in cardiac tissue. METHODS: Myocardial samples were obtained at the time of transplantation from 23 patients (age 54 +/- 12 years) with heart failure secondary to ischemic heart disease and 16 patients (age 51 +/- 7 years) with idiopathic dilated cardiomyopathy (DCM). A control group comprised postmortem samples obtained from 14 patients (age 70 +/- 5 years) who died of non-cardiovascular causes. Ventricular sialylation was quantitated using the sialic acid-specific lectins Maackia amurensis agglutinin (MAA) and Sambucus nigra agglutinin (SNA) using a chemiluminescence assay. Results are expressed as the percentage (+/-standard error of the mean) of the binding of lectin to a standardized control sample of human myocardium. RESULTS: Ventricular sialylation recognized by MAA was 55 +/- 7% in patients with heart failure secondary to ischemic heart disease compared with 26 +/- 7% for DCM (p = 0.006) and 32 +/- 8% for controls (p = 0.04), and that recognized by SNA was 69 +/- 7% in patients with heart failure secondary to ischemic heart disease compared with 42 +/- 6% for DCM (p = 0.006) and 38 +/- 7% for controls (p = 0.006). No significant difference in ventricular sialylation was observed between patients with DCM and controls. CONCLUSION: Myocardial levels of sialic acids are significantly increased in patients with heart failure secondary to ischemic heart disease compared with patients with idiopathic dilated cardiomyopathy and controls. Our findings are important in view of recent reports of an association between serum sialic acid concentration and cardiovascular mortality and require further investigation.  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