全文获取类型
收费全文 | 2218篇 |
免费 | 36篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 10篇 |
综合类 | 16篇 |
化学工业 | 25篇 |
金属工艺 | 16篇 |
机械仪表 | 7篇 |
建筑科学 | 6篇 |
矿业工程 | 6篇 |
能源动力 | 1篇 |
轻工业 | 15篇 |
水利工程 | 8篇 |
石油天然气 | 4篇 |
无线电 | 14篇 |
一般工业技术 | 56篇 |
冶金工业 | 2061篇 |
自动化技术 | 17篇 |
出版年
2024年 | 3篇 |
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 12篇 |
2011年 | 18篇 |
2010年 | 13篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 14篇 |
2006年 | 5篇 |
2005年 | 13篇 |
2004年 | 2篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 73篇 |
1998年 | 631篇 |
1997年 | 364篇 |
1996年 | 234篇 |
1995年 | 135篇 |
1994年 | 121篇 |
1993年 | 142篇 |
1992年 | 13篇 |
1991年 | 18篇 |
1990年 | 9篇 |
1989年 | 16篇 |
1988年 | 27篇 |
1987年 | 21篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1980年 | 21篇 |
1978年 | 4篇 |
1977年 | 63篇 |
1976年 | 112篇 |
1975年 | 7篇 |
1973年 | 1篇 |
1966年 | 2篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2262条查询结果,搜索用时 0 毫秒
101.
102.
103.
DE Holt TA Ryder A Fairbairn R Hurley D Harvey 《Canadian Metallurgical Quarterly》1997,16(10):570-576
1 Chloramphenicol is used extensively in non-industrialized countries for the treatment of life-threatening infections because it is cheap and effective, despite its known hemotoxicity and linkage to fatal aplastic anaemia. It is important to define the mechanism of toxicity so that means can be devised to ameliorate the toxic effects in order to produce safer usage. 2 Chloramphenicol, at concentrations from 5 mM to 2 mM initiated apoptosis in dividing cells from a monkey kidney-derived cell line and in haematopoietic progenitor cells from human neonatal cord blood. 3 Growth of progenitor cells was suppressed at concentrations of chloramphenicol which would be considered less than therapeutic during patient treatment. 4 These effects could be ameliorated in progenitor cells by co-culture with the antioxidant mercaptoethylamine and in monkey kidney cells by co-culture with vitamin C. 5 This is the first report of apoptosis in chloramphenicol toxicity and suggests a possible link between a metabolic event i.e. the production of free radicals; a morphological effect, apoptosis; and a clinical effect, bone marrow suppression and aplastic anaemia. 相似文献
104.
105.
A case is reported of a woman with an ischemic arm as a result of damage to the subclavian artery by the clavicular anomaly associated with cleidocranial dysostasis. Only one similar case has been reported previously. 相似文献
106.
107.
Being a foreign body, intrauterine coil causes decubitus and inflammation of the adjacent tissues. Long-term carriage of the coil may give rise to endometritis, myometritis, parametritis, salpingo-oophoritis, tubo-ovarian inflammatory infiltrates. These infiltrates invade retroperitoneal pelvic fat and may obstruct pelvic ureters. Ureteral obstruction may bring about ureterohydronephrosis, pyelonephritis and renal calculi. The coil may be also responsible for chronic pyelonephritis. The authors have treated 64 females aged 18-45 years with urological complications due to intrauterine coils which stayed from 6 months to 14 years. 34 of them presented with attack of acute pyelonephritis, 29 with renal colic and acute pyelonephritis, 26 with renal calculi. To arrest renal colic and attack of acute pyelonephritis ureteral catheterization and renal pelvis drain were performed in 31 patients. One patient has undergone ureterolithotomy. 8 patients rejected removal of the coil and had recurrent renal colics and acute pyelonephritis attacks. Removal of the coil arrested pyelonephritis and lithogenesis in the kidney. In one case of coil removal there was injury to the uterine cervix and urinary bladder eventuating in vesicovaginal fistula. 相似文献
108.
Early surgery in patients with mitral regurgitation due to flail leaflets: a long-term outcome study
LH Ling M Enriquez-Sarano JB Seward TA Orszulak HV Schaff KR Bailey AJ Tajik RL Frye 《Canadian Metallurgical Quarterly》1997,96(6):1819-1825
BACKGROUND: The optimal timing for surgery in patients with mitral regurgitation is disputed. Because of the frequency of left ventricular dysfunction, which is difficult to predict, early surgery has been recommended, but its potential benefits have not been demonstrated. METHODS AND RESULTS: The outcomes of 221 patients (mean age, 65 +/- 13 years; 71% males) with flail leaflets diagnosed with two-dimensional echocardiography between 1980 and 1989 who were eligible for operation were analyzed. Group I comprised 63 patients who had early mitral valve surgery (within 1 month after diagnosis). Group II comprised 158 patients initially treated conservatively (80 of whom were operated on later). Group I patients were younger (P=.009), had more symptoms (P<.0001), and were more frequently in atrial fibrillation (P=.023) than group II patients. There was no difference in ejection fraction between the groups. The early surgery strategy was followed by an improved overall survival rate (P=.028) and a lower incidence of cardiovascular deaths (P=.025), congestive heart failure (P=.046), and new chronic atrial fibrillation (P=.032), as confirmed by multivariate analysis (adjusted risk ratios of 0.31, 0.18, 0.38, and 0.05, respectively; all P<.02). CONCLUSIONS: In patients with mitral regurgitation due to flail leaflets, the strategy of early surgery versus conservative management is associated with an improved long-term survival rate, decreased cardiac mortality, and decreased morbidity after diagnosis. This outcome advantage suggests that early surgery is a reasonable treatment option to be considered in low-risk candidates with repairable valves and severe mitral regurgitation. 相似文献
109.
PA Robertson JS Brown TA Flanagan ME Goldman LA Learman AE Stevens N Wilcox 《Canadian Metallurgical Quarterly》1997,176(6):1368-1373
OBJECTIVES: Our objectives were to (1) expand and strengthen the women's health curriculum at the University of California, San Francisco, and (2) evaluate the responses of both medical students and faculty to this curriculum. STUDY DESIGN: A written evaluation of the curriculum in women's health was completed by both students and faculty. Variables studied included mean scores of cases, the overall course score, and the preferences of medical students for faculty specialty in teaching the small groups. RESULTS: The overall course evaluation score was 7.81 (range 1 to 10). For those students who had both faculty from internal medicine or family medicine and obstetrics and gynecology, there was a strong preference that obstetrician-gynecologists teach the majority of the cases. CONCLUSIONS: The new case-based curriculum in women's health was enthusiastically received by both medical students and faculty. 相似文献
110.
The inclusion of people with developmental disabilities in managed care as part of general efforts by states to enroll and Medicaid recipients in such plans was reviewed. Managed care was defined and the processes by which managed care organizations deliver services were explained. Escalating costs and utilization were discussed as the primary reason for the shift to managed care. The use of Medicaid Section 1115 waivers by states to include Medicaid recipients was explored. The relation between acute health care and long-term care, and the utilization patterns in each, were briefly described. Finally, elements of managed care that are particularly important to people with developmental disabilities, such as care coordination, maintenance of quality, and individual and family support, were discussed. 相似文献