全文获取类型
收费全文 | 991篇 |
免费 | 19篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 1011篇 |
出版年
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.
Ford Julian D.; Racusin Robert; Daviss William B.; Ellis Cynthia G.; Thomas Julie; Rogers Karen; Reiser Jessica; Schiffman Jill; Sengupta Anjana 《Canadian Metallurgical Quarterly》1999,67(5):786
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.
Increased milk production versus reproductive and energy status of high producing dairy cows 总被引:5,自引:0,他引:5
R O Harrison S P Ford J W Young A J Conley A E Freeman 《Journal of dairy science》1990,73(10):2749-2758
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.
Lin Lin Low Brian O'Neill Chris Ford Jim Godden Mark Gishen & Christopher Colby 《International Journal of Food Science & Technology》2008,43(7):1202-1216
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.