全文获取类型
收费全文 | 2121篇 |
免费 | 2篇 |
专业分类
化学工业 | 11篇 |
金属工艺 | 2篇 |
机械仪表 | 1篇 |
建筑科学 | 9篇 |
矿业工程 | 1篇 |
轻工业 | 4篇 |
水利工程 | 1篇 |
无线电 | 5篇 |
一般工业技术 | 9篇 |
冶金工业 | 2066篇 |
自动化技术 | 14篇 |
出版年
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 8篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 1篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 8篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 59篇 |
1998年 | 627篇 |
1997年 | 369篇 |
1996年 | 221篇 |
1995年 | 153篇 |
1994年 | 111篇 |
1993年 | 136篇 |
1992年 | 22篇 |
1991年 | 34篇 |
1990年 | 29篇 |
1989年 | 31篇 |
1988年 | 26篇 |
1987年 | 23篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 49篇 |
1976年 | 85篇 |
1975年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有2123条查询结果,搜索用时 15 毫秒
991.
992.
In patients with diabetes mellitus, heart disease is more common that in the background populations and has a more serious prognosis. The reasons are only partially understood. Whether patients with diabetes mellitus have a more diffuse and pronounced coronary atherosclerosis has been the subject of many investigations with diverging results. However, the larger studies suggest that coronary atherosclerosis is more pronounced and diffuse in diabetics compared with non-diabetic patients. The pathoanatomic picture of the atherosclerotic process seems to be identical in patients with and without diabetes mellitus. A number of structural abnormalities in the intramural vessels and interstitial tissue of the heart have been demonstrated in diabetics. However, similar abnormalities have also been reported in non-diabetic patients. With respect to where "diabetic cardiomyopathy" is a specific entity, the existing data are not confirmative. Whether diabetes mellitus per se induces functional changes in the coronary vascular system leading to myocardial ischaemia and dysfunction is a subject for future investigations. 相似文献
993.
Cocaine and heroin often are abused together in a combination known as a "speedball," but relatively little is known about ways in which cocaine and heroin may interact to modify each other's abuse-related effects. The present study evaluated the discriminative stimulus effects of a speedball combination of cocaine and heroin. Three rhesus monkeys were trained to discriminate vehicle from a 10:1 ratio of cocaine (0.4 mg/kg) in combination with heroin (0.04 mg/kg). Both cocaine alone and heroin alone substituted completely for the cocaine/heroin combination, although cocaine and heroin were more potent when administered together than when administered alone. Combined pretreatment with the dopamine antagonist flupenthixol and the opioid antagonist quadazocine dose-dependently antagonized the discriminative stimulus effects of the cocaine/heroin combination, but pretreatment with either antagonist alone was less effective. These findings suggest that either cocaine or heroin alone was sufficient to substitute for the cocaine/heroin training combination. To characterize the discriminative stimulus properties of this speedball more fully, a series of cocaine-like and heroin-like agonists were studied in substitution tests. The indirect dopamine agonists CFT, amphetamine and bupropion and the mu opioid agonists alfentanil, fentanyl and morphine produced high levels of speedball-appropriate responding. However, the indirect dopamine agonist GBR12909, the D1 dopamine agonist SKF82958, the D2 dopamine agonist quinpirole and the partial mu opioid agonist nalbuphine did not substitute for the cocaine/heroin combination. Because these compounds produce discriminative stimulus effects similar to either cocaine or mu opioid agonists alone, these findings suggest that the discriminative stimulus effects of the cocaine/heroin combination do not overlap completely with the effects of cocaine and heroin alone. Finally, a series of compounds that produce partial or no substitution for cocaine or mu agonists alone also did not substitute for the cocaine/heroin combination, which indicates that the discriminative stimulus effects of the combination were pharmacologically selective. Taken together, these findings suggest that a combination of cocaine and heroin produces a pharmacologically selective discriminative stimulus complex that includes aspects of both component drugs. 相似文献
994.
R Sylla A Diouf B Niane B Ndiaye MB Guisse A Diop M Ciss D Ba 《Canadian Metallurgical Quarterly》1994,39(2):223-226
This survey which involved 6 salesman and 159 women, allowed us to carry out a study on the different cosmetic products used by women in Dakar to artificially bleach their skin. An analytical study has been conducted on those skin bleaching products through colorimetric identifications of hydroquinone, corticoids and mercurial derivates and the dosage of hydroquinone by High Performance Liquid Chromatography (HPLC). It was established that those products were essentially corticoids and hydroquinone based products and could induce serious dermatological troubles to users. This phenomenon, known in Wolof "xessal", and motivated by various factors, is facilitated by easy access to skin bleaching products available in the town market places. It affects an important part of the female population of all ages (educated, illiterate, married and single). In view of the importance of the phenomenon, emergency actions must be taken to eradicate it. 相似文献
995.
996.
To determine whether an absence of leukocytes in semen and urine predicts an absence of Chlamydia trachomatis in asymptomatic infertile men, chlamydial DNA was detected in subjects' semen and urine by ligase chain reaction (LCR). Ninety-eight infertile men were studied, including 39 cases of oligozoospermia, 19 of azoospermia, 16 of asthenozoospermia, and 24 of normozoospermia. None of the subjects had pyospermia or pyuria. C. trachomatis was detected by LCR. Antichlamydial and antisperm antibody were also measured. C. trachomatis was detected by LCR in the semen of only 1 of 98 patients (1.02%), but not in the urine samples. In C. trachomatis-positive patients LCR, IgG, and IgA levels were higher than normal. No antisperm antibody was detected. Even if leukocytes are not observed in the semen and urine of asymptomatic infertile men, the presence of C. trachomatis in semen specimens is rarely observed. Therefore, it should be noted that the presence of C. trachomatis in such cases is addressed in the context of artificial insemination and other assisted reproductive technologies. 相似文献
997.
RW Hobson JE Goldstein Z Jamil BC Lee FT Padberg AK Hanna GA Gwertzman PJ Pappas MB Silva 《Canadian Metallurgical Quarterly》1999,29(2):228-35; discussion 235-8
PURPOSE: Surgical management of carotid restenosis (CR) after carotid endarterectomy (CEA) has been associated with a higher perioperative complication rate than that of primary CEA. We recently used carotid angioplasty-stenting (CAS) as an alternative to operative management in patients who had undergone CEA within three years, and we retrospectively compared these results with those of operative management of CR and the overall results of CEA. METHODS: CEA was performed on 1065 adult patients (58% symptomatic, 42% asymptomatic), 62% of whom were men (n = 660) and 38% of whom were women (n = 405), from 1989 to 1997. Before our initiation of a program of CAS, 16 operative procedures (1.9% of CEAs) were performed for CR in 14 adult patients (7 women and 7 men). During the last 20 months, CAS was used in the management of 17 CRs (16 patients; 9 women and 7 men). RESULTS: The 30-day stroke morbidity-death rate for all CEAs (n = 1065) was 1.4%; 11 strokes (1. 0%) occurred (4 major strokes with disability and 7 strokes with minor or no disability), and 4 deaths (0.4%) occurred (2 deaths caused by myocardial infarction, 1 caused by intracranial hemorrhage, and 1 caused by stroke). Operative management of CR (n = 16) included patch angioplasty in 12 cases (autologous vein patches in 10 cases and synthetic patches in 2 cases), whereas interposition grafting was used in 4 cases (saphenous vein in 3 instances and synthetic [polytetrafluoroethylene] in one case). No strokes or deaths were observed. One recurrent laryngeal nerve palsy occurred (6.2%). Among the 16 patients undergoing 17 CAS procedures, the technical procedures were accomplished in all patients. No strokes or deaths occurred. No recurrent restenoses (50% or greater) have been identified within or adjacent to the CAS procedures. CONCLUSION: CR caused by myointimal hyperplasia can be managed by operative techniques or CAS with comparable periprocedural complications. Although long-term follow-up will be required to determine the incidence of recurrent restenosis, CAS may become the preferred procedure in these cases. A randomized clinical trial ultimately will be necessary to determine the role of CAS, as compared with that of operative management. 相似文献
998.
MB Katan JP Deslypere AP van Birgelen M Penders M Zegwaard 《Canadian Metallurgical Quarterly》1997,38(10):2012-2022
Tissue levels of n-3 fatty acids reflect dietary intake, but quantitative data about rate of incorporation and levels as a function of intake are scarce. We fed 58 men 0, 3, 6, or 9 g/d of fish oil for 12 months and monitored fatty acids in serum cholesteryl esters, erythrocytes, and subcutaneous fat during and after supplementation. Eicosapentaenoic acid (EPA) in cholesteryl esters plateaued after 4-8 weeks; the incorporation half-life was 4.8 days. Steady-state levels increased by 3.9 +/- 0.3 mass % points (+/- SE) for each extra gram of EPA eaten per day. Incorporation of docosahexaenoic acid (DHA) was erratic; plateau values were 1.1 +/- 0.1 mass % higher for every g/d ingested. Incorporation of EPA into erythrocyte membranes showed a half-life of 28 days; a steady state was reached after 180 days. Each g/d increased levels by 2.1 +/- 0.1 mass %. C22:5n-3 levels increased markedly. Changes in DHA were erratic and smaller. EPA levels in adipose tissue rose also; the change after 6 months was 67% of that after 12 months in gluteal and 75% in abdominal fat. After 12 months each gram per day caused an 0.11 +/- 0.01 mass % rise in gluteal fat for EPA, 0.53 +/- 0.07 for C22:5n-3, and 0.14 +/- 0.03 for DHA. Thus, different (n-3) fatty acids were incorporated with different efficiencies, possibly because of interconversions or different affinities of the enzymatic pathways involved. EPA levels in cholesteryl esters reflect intake over the past week or two, erythrocytes over the past month or two, and adipose tissue over a period of years. These findings may help in assessing the intake of (n-3) fatty acids in epidemiological studies. 相似文献
999.
D Jourd''heuil CT Mai FS Laroux DA Wink MB Grisham 《Canadian Metallurgical Quarterly》1998,246(3):525-530
The gut peptide glucagon-like peptide 1(7-36) amide (GLP-1) is released into the circulation after food intake. GLP-1 has been shown to have an incretin effect and inhibits gastrointestinal motility in humans. In rats, intracerebral administration of GLP-1 results in reduced food intake. Obese humans have been found to have an attenuated plasma GLP-1 response to a mixed meal. To approximate the physiologic state, GLP-1 or saline was administered intravenously and randomly at the beginning of a test meal served on a universal eating monitor to 6 obese subjects to test our hypothesis that GLP-1 influences termination of food intake (and thus food intake during a meal) and feelings of satiety in humans. As a marker for gastric emptying, 1.5 g acetaminophen was given at the start of the meal. Blood samples for analysis of acetaminophen, insulin, glucose, glucagon, and C-peptide were obtained. Hunger, fullness, and food choice were assessed with visual analogue scales and food-choice questionnaires. GLP-1 infusion resulted in a prolonged period of reduced feelings of hunger, desire to eat, and prospective consumption after the meal. The rate of gastric emptying was slower during infusion of GLP-1. Postprandial blood glucose concentrations were reduced during the GLP-1 infusion, but the amount of energy consumed, eating rate, and plasma concentrations of insulin, glucagon, and C-peptide were unchanged. GLP-1 given exogenously at the start of a meal did not seem to affect meal termination or the amount of food eaten. However, postprandial feelings of hunger decreased, suggesting that exogenous GLP-1 may influence feelings of hunger and satiety in humans. 相似文献
1000.
NG Velitchkov GK Kirov JE Losanoff KT Kjossev GI Grigorov MB Mironov IS Klenov 《Canadian Metallurgical Quarterly》1997,40(5):530-533
PURPOSE: We sought to evaluate a new technique for creation of a continent perineal colostomy following abdominoperineal resection (APR) of the rectum for low rectal cancer. METHODS: Nine selected patients with low rectal cancer (two males; median age, 55.6 years; classified as Dukes A, 6 patients and as Dukes B, 3 patients) underwent APR. Following this, the original Lazaro da Silva technique was used as follows: 1) for performance of three circular myotomies in the distal sigmoid with a distance between each couple of no more than 8 cm; 2) repair of the myotomies, thus creating three circular colonic valves, the most distal of which remained extraperitoneally; 3) for construction of a perineal colostomy lying flush with the perineal skin; 4) after the patient starts consuming a regular diet, enemas through the perineal stoma are done, usually twice per week, to achieve defecation. Functional outcome was assessed by evaluation of bowel movements and neoanal continence. RESULTS: There were no deaths. From January 1994 until October 1995, no tumor recurrence has occurred, and fecal continence has been good. Four of the patients were able to defecate without enemas (2-4 times per week), and in five patients the self-administration of enemas (2-4 times a week) were necessary to accomplish defecation. CONCLUSION: Initial results with the Lazaro da Silva technique have been encouraging. 相似文献