首页 | 官方网站   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   991篇
  免费   19篇
  国内免费   1篇
工业技术   1011篇
  2022年   5篇
  2020年   6篇
  2019年   5篇
  2018年   8篇
  2017年   16篇
  2016年   13篇
  2015年   8篇
  2014年   10篇
  2013年   24篇
  2012年   20篇
  2011年   29篇
  2010年   11篇
  2009年   20篇
  2008年   38篇
  2007年   27篇
  2006年   19篇
  2005年   38篇
  2004年   26篇
  2003年   16篇
  2002年   19篇
  2001年   17篇
  2000年   19篇
  1999年   28篇
  1998年   102篇
  1997年   60篇
  1996年   45篇
  1995年   38篇
  1994年   31篇
  1993年   30篇
  1992年   9篇
  1991年   10篇
  1990年   17篇
  1989年   14篇
  1988年   20篇
  1987年   18篇
  1986年   19篇
  1985年   15篇
  1984年   19篇
  1983年   8篇
  1982年   11篇
  1981年   11篇
  1979年   8篇
  1978年   11篇
  1977年   11篇
  1976年   18篇
  1973年   7篇
  1972年   7篇
  1970年   6篇
  1968年   4篇
  1967年   4篇
排序方式: 共有1011条查询结果,搜索用时 15 毫秒
81.
OBJECTIVES: The aim of this study was to evaluate the sealing ability and physical and chemical properties of glass ionomer cement (GIC) and mineral trioxide aggregate (MTA) using Rhodamine B at different pHs as tracer. METHODS: Chemical analysis, pH and micro-hardness of GIC and MTA were performed. In addition dye leakage was assessed by tracer leakage using Tandem Scanning Confocal Microscope (TSM) after immersion of premolar teeth in a stock and a buffered fluorescent Rhodamine B for 24 h. Ultra-structural changes within the materials were evaluated by viewing under the field emission scanning electron microscope (FESEM). RESULTS: GIC and MTA showed elemental peaks for silicon, aluminium and calcium while MTA also had bismuth. GIC was acidic (P = 0.001) and caused an increase in dye pH (P = 0). Immersion of MTA in any of the test solutions resulted in an increase in the pH of the solution (P < 0.05). Use of a dye solution of lower pH than the material under test increased the cement micro-hardness. GIC demonstrated marginal leakage on TSM and both increase in marginal leakage and material porosity on FESEM. MTA was not affected by the use of acidic dye but showed a tendency to take up dye within the material shown on TSM. CONCLUSIONS: Evaluation of marginal adaptation of dental materials was shown to be dependent on the technique used for viewing the material to tooth interface, the properties of the material under study and the pH of the dye used.  相似文献   
82.
83.
Consecutive admissions to an outpatient child psychiatry clinic diagnosed with oppositional defiant disorder (ODD), attention deficit-hyperactivity disorder (ADHD), or adjustment disorder were assessed for trauma exposure by a structured clinical interview and parent report. Controlling for age, gender, severity of internalizing behavior problems, social competence, family psychopathology, and parent–child relationship quality (assessed by parent report), an ODD diagnosis, with or without comorbid ADHD, was associated with increased likelihood of prior victimization (but not nonvictimization) trauma. ADHD alone was not associated with an increased likelihood of a history of trauma exposure Traumatic victimization contributed uniquely to the prediction of ODD but not ADHD diagnoses. Children in psychiatric treatment who are diagnosed with ODD, but not those diagnosed solely with ADHD, may particularly require evaluation and care for posttraumatic sequelae. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
84.
Two groups of 10 Holstein cows were chosen by pairs from a 20-yr genetic selection project that used either breed average or breed high sires chosen only for Predicted Differences in milk production. Milk production (305-d mature equivalent) was 10,814 kg and 6912 kg for the high and average groups of cows. Days to first visual estrus and number of ovulations before first visual estrus were greater for the high versus the average group (66 vs. 43 d and 1.6 vs. .7 ovulations). No differences were significant between groups for the interval from parturition to uterine involution or for days to first ovulation. Energy balance was less for the high group during wk 1, 2, 10, and 11. Plasma glucose concentration was lowest during wk 2 for both groups, and nonesterified fatty acids and beta-hydroxybutyrate were greatest for both groups during wk 1 and 2. Liver glycogen content was lower at d 15 postpartum for the high group, and liver triglyceride content was greater on d 30 for the high group. The data for reproductive functions support the concept that high milk production is antagonistic to expression of estrous behavior but not to reactivation of ovarian function.  相似文献   
85.
Comments that J. Seeman's (see record 1989-40866-001) model of positive health is a constructive step toward the creation of a larger conceptual framework for health psychology. However, Seeman's model lacks a propositional "glue" that links subsystems into coordinated functioning in a larger system of concern: the person-in-context. As such, the model is a partial taxonomy of relevant phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
86.
87.
Cold stabilisation is a widely used industrial process to prevent tartrate instability in bottled wines. In this article, current knowledge regarding performance and cost of cold stabilisation and alternative technologies for tartrate stabilisation is reviewed. Whilst there have been occasional cost comparisons between cold stabilisation and alternative technologies published in the literature, existing data is not satisfactory to permit an accurate economic evaluation of the different process options. Therefore, alternative technologies to cold stabilisation, including the Westfalia process, nanofiltration and electrodialysis were compared for both technical and economic performance. The engineering calculations and conceptual cost estimates were based on real world data from an Australian winery. Product loss was a key cost driver in differentiating tartrate stabilisation processes. Cold stabilisation was found to be the most economic treatment process irrespective of scale or winery size. Westfalia process and nanofiltration were the next most cost effective options.  相似文献   
88.
History of early childhood trauma was prevalent and highly correlated with Disorders of Extreme Stress Not Otherwise Specified (DESNOS) in a sample of veterans in inpatient treatment for chronic posttraumatic stress disorder (PTSD). DESNOS predicted reliable change on a variety of measures of psychiatric symptomatology (including PTSD) and psychosocial functioning independently of the effects of PTSD diagnosis and early childhood trauma history. DESNOS also predicted treatment outcome on PTSD and quality of life measures after controlling for the effects of ethnicity, war zone trauma exposure severity, initial level of symptomatic severity or quality of life, Axis I (PTSD and major depression) and Axis II (personality disorder) diagnostic status, and early childhood trauma history. Early childhood trauma was not predictive of outcome. DESNOS appears to play an important role in assessment and treatment planning for psychotherapeutic rehabilitation of chronic PTSD.  相似文献   
89.
Bleeding stomal varices is a rare complication of portal hypertension. We report the case of a cirrhotic patient, with a history of colonic adenocarcinoma, who had recurrent bleeding stomal varices. Treatment with transjugular intrahepatic portosystemic shunt and stomal varice embolization was performed because failure of medical treatment of portal hypertension and sclerotherapy. Twenty six months later only one stomal hemorrhage was noted. This suggests that transjugular intrahepatic portosystemic shunt and stomal varice embolization is effective in case of recurrent bleeding of stomal varices.  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-23

京公网安备 11010802026262号