全文获取类型
收费全文 | 1065篇 |
免费 | 0篇 |
专业分类
化学工业 | 6篇 |
无线电 | 2篇 |
一般工业技术 | 2篇 |
冶金工业 | 1050篇 |
自动化技术 | 5篇 |
出版年
2022年 | 1篇 |
2013年 | 3篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 1篇 |
1999年 | 28篇 |
1998年 | 337篇 |
1997年 | 170篇 |
1996年 | 139篇 |
1995年 | 72篇 |
1994年 | 55篇 |
1993年 | 65篇 |
1992年 | 5篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 37篇 |
1976年 | 54篇 |
1975年 | 1篇 |
排序方式: 共有1065条查询结果,搜索用时 0 毫秒
71.
BR Prestidge JJ Prete TA Buchholz JL Friedland RG Stock PD Grimm WS Bice 《Canadian Metallurgical Quarterly》1998,40(2):461-465
PURPOSE: To help establish standards of care for transperineal interstitial permanent prostate brachytherapy (TIPPB) by obtaining data regarding current clinical practice among the most experienced TIPPB brachytherapists in the United States. METHODS AND MATERIALS: The 70 brachytherapists who performed the greatest number of TIPPB cases in 1995 in the U.S. were surveyed. Each received a comprehensive four page questionnaire that included sections on training and experience, patient and isotope selection criteria, manpower, technique, and follow-up. Thirty-five (50%) surveys were ultimately returned after three mailings and follow-up phone calls. The cumulative experience of the 35 respondents represented approximately 45% of the total TIPPB volume in the U.S. for 1995. Respondents included 29 from the private sector and six from academic programs. RESULTS: The median physician experience with TIPPB was reported as 4.9 years. Each performed an average of 73 TIPPB procedures in 1995 (range 40-300). This represented an increase in volume for most (74%) of the respondents. Sixty-three percent of the respondents attended a formal training course, 54% had TIPPB-specific residency training, and 31% had been proctored (16 had received two or more types of training experience). The most commonly reported selection criteria for implant alone was on Gleason score < or = 7, PSA < 15, < or = Stage T2a, and gland size < or = 60 cc, although no clear consensus was found. Fifty-four percent considered a history of TURP to be a relative contraindication, while 34% considered TURP to have no impact on patient selection. Eighty-six percent of respondents combine brachytherapy with external beam radiation in an average of 32% of their patients. Boosts were given with both 125I prescribed to 120 Gy (75%) or 103Pd to 90 Gy (50%). Sixty percent reported using a Mick applicator, 46% prefer using preloaded needles, and (11%) use both techniques. Real-time imaging was usually performed with ultrasound (94%); most included fluoroscopy (60%). Definitions of PSA control varied widely. CONCLUSIONS: TIPPB clinical practice in the U.S. demonstrates similarities in technique, but differences in patient selection and definitions of biochemical control. It is, therefore, incumbent on those beginning TIPPB programs to carefully review the specific practice details of those institutions with a broad experience. 相似文献
72.
Prognostic risk stratification to identify perioperative and long-term cardiac risk in selected patients undergoing noncardiac surgery is part of good clinical practice. Exercise variables associated with significant increased risk include poor functional capacity (eg, <4 metabolic equivalents), marked exercise-induced ST segment shift or angina at low workloads, and inability to increase or actually decrease systolic blood pressure with progressive exercise. Approximately 40% of patients tested before peripheral vascular surgery will have an abnormal exercise electrocardiogram (ECG). The predictive value for a perioperative event, ie, death or myocardial infarction, ranges from 5% to 25% for a positive test and 90% to 95% for a negative test. Whereas exercise cardiac imaging is the modality of choice in patients with a noninterpretable exercise ECG, pharmacological stress imaging should be used in the 30% to 50% of patients who require perioperative noninvasive risk stratification and are unable to perform an adequate level of exercise to test cardiac reserve. Myocardial perfusion variables predictive of increased cardiac events include severity of the perfusion defect, number of reversible defects, extent of fixed and reversible defects, increased lung uptake of thallium-201, and marked ST segment changes associated with angina during the test. The reported sensitivity and specificity of dobutamine-induced echocardiographic wall motion abnormalities in patients with peripheral vascular disease is similar to myocardial perfusion scintigraphy, but the confidence limits are wider due to the smaller sample size in these more recent studies. In conclusion, noninvasive cardiac testing should be used selectively in patients undergoing noncardiac surgery; the results provide useful estimates of short- and long-term risk of cardiac events, and the magnitude of abnormal response on noninvasive testing should be used to formulate decisions regarding the need for coronary angiography and subsequent revascularization. 相似文献
73.
L Cohen FR Hendrickson AJ Lennox TK Kroc MA Hatcher BR Bennett 《Canadian Metallurgical Quarterly》1996,200(3):627-630
PURPOSE: To evaluate neutron irradiation alone and with chemotherapy to treat inoperable pancreatic cancer. MATERIALS AND METHODS: Between 1977 and 1994, 173 patients (60 men, 113 women, aged 43-77 years [mean, 59 years]) with unresectable adenocarcinoma of the exocrine pancreas were treated, 106 with neutron irradiation alone and 67 with concomitant chemotherapy (fluorouracil [5-FU]). At follow-up, which was performed at 2-month intervals until death (range, 4-64 months), clinical status was recorded, noting the presence of overt metastasis and the onset of any major complications. Actuarial (Kaplan-Meier) survival tables were computed for both groups. RESULTS: For neutron irradiation alone and neutron irradiation plus chemotherapy, median survival times were 6 months and 9 months, respectively; actuarial survival rates at 3 years were 0 and 7%, respectively; major reactions (grade 3 or higher [scale of the Radiation Therapy Oncology Group and European Organization for Research and Treatment of Cancer]) occurred in 19 (18%) and 17 (25%) patients, respectively; and severe complications (grade 4) occurred in five (5%) and four (6%) patients, respectively. Most deaths were due to metastatic disease rather than to failure of local control. CONCLUSIONS: Neutron irradiation obliterated pancreatic adenocarcinoma at the primary site but has no effect on long-term survival. With more effective concomitant chemotherapy to prevent metastasis, local control of pancreatic cancer with neutron irradiation could lead to increased long-term survival. 相似文献
74.
BR Clower Y Yamamoto L Cain DE Haines RR Smith 《Canadian Metallurgical Quarterly》1994,240(1):104-114
BACKGROUND: The leading cause of death and disability in patients suffering from aneurysmal subarachnoid hemorrhage (SAH) is cerebral vasospasm, a persistent, progressive, and often irreversible constriction of cerebral arteries. A wide array of pathological changes occur in cerebral arteries following SAH, with endothelial injury being the earliest and most consistent one. Since intact endothelium modulates many reflexes that influence vascular tone, damage to them may represent a significant contributor to cerebral vasospasm. METHODS: Changes in local cerebellar blood flow (LCBF) and pathological alterations in major cerebral arteries were studied and compared in rats at various time intervals following SAH. SAH induced by the subarachnoid injection of 0.3 ml of whole blood. Sham rats received a subarachnoid injection of 0.3 ml of isotonic saline. RESULTS: Except for an immediate but transient decrease, LCBF remained unchanged over a 3 day period following saline injection. Likewise, there were no pathological alterations in cerebral arteries of saline-injected rats. In contrast, the subarachnoid injection of whole blood produced significant changes in both LCBF and cerebral arteries. Within 30 minutes post-blood injection, LCBF became significantly decreased and remained so for 4 hours. However, within 24 hours, LCBF had returned to control levels where it remained for 3 days. Endothelial injury was observed in the basilar and middle cerebral arteries from 30 minutes through 4 hours, the same periods in which LCBF was significantly reduced. Within 24 hours, the time period in which LCBF had rebounded to control ranges, cerebral arteries showed no evidence of endothelial damage and resembled control cells. CONCLUSION: The results indicate a direct correlation between changes in LCBF and the structural integrity of endothelial cells in the early stages following SAH. The lack of chronically depressed LCBF (after 1 day) may be related to the quick structural repair of endothelium. 相似文献
75.
FD Brenneman D Katyal BR Boulanger M Tile DA Redelmeier 《Canadian Metallurgical Quarterly》1997,42(5):773-777
BACKGROUND: Open pelvic fractures represent one of the most devastating injuries in orthopedic trauma. The purpose of this study was to document the injury characteristics, complications, mortality, and long-term, health-related quality of life outcomes in patients with open pelvic fractures. METHODS: The trauma registry at an adult trauma center was used to identify all multiple system blunt trauma patients with a pelvic fracture from January of 1987 to August of 1995 (n = 1,179). Demographic data, mechanism of injury, and fracture type were determined from hospital records. Short-term outcome measures included infectious complications, mortality, and length of stay in hospital. Long-term outcomes of survivors were obtained by telephone interview using the SF-36 Health Survey and the Functional Independence Measure. RESULTS: Open pelvic fractures were uncommon, occurring in 44 patients (4%). Patients with open fractures were about 9 years younger, on average, than patients with closed fractures (30 vs. 39, p < 0.001). Similarly, patients with open fractures were more likely to be male (75 vs. 57%, p < 0.02), more likely to have been involved in a motorcycle crash (27 vs. 6%, p < 0.001), and more likely to have an unstable pelvic ring disruption (45 vs. 25%, p < 0.001). Open pelvic fracture patients required more blood than closed pelvic fracture patients, both in the first day (16 vs. 4 units, p < 0.001) and during the total hospital admission (29 vs. 9 units, p < 0.001). Five patients with perineal wounds did not receive a diverting colostomy; in turn, these individuals had a total of six pelvic infectious complications (one abscess, two with osteomyelitis, and three perineal wound infections). Overall, 11 patients died, six patients were lost to follow-up, and 27 were long-term survivors (mean duration of 4 years). Chronic disability was common after a pelvic fracture, with problems related to physical role performance and physical functioning, and was particularly severe after an open pelvic fracture (p < 0.05 for both as measured by the SF-36). CONCLUSIONS: Patients with open pelvic fractures often survive, need to be treated with massive blood transfusions, and often require a colostomy. They are frequently left with chronic pain and residual disabilities in physical functioning and physical roles, and many remain unemployed years after injury. 相似文献
76.
J Sanders Y Oda SA Roberts M Maruyama J Furmaniak BR Smith 《Canadian Metallurgical Quarterly》1997,11(3):451-479
The thyrotropin (TSH) receptor (TSHR) is a key protein in the control of thyroid function and a major thyroid autoantigen. Recently, molecular cloning of the receptor has been carried out and we now review the impact of this work on our understanding of the physiology and pathophysiology of the TSHR. Analysis of recombinant TSHR proteins expressed in prokaryotic and eukaryotic systems has indicated that post-translational processing is important for the formation of active receptors. Studies of TSHR glycosylation have shown that a 'mature' form of the receptor containing mainly complex-type sugar residues is principally involved in TSH and TSHR autoantibody (TRAb) binding. In addition, the processing of the TSHR peptide chain into two subunits observed with native TSHR has been confirmed using recombinant TSHR. However, despite considerable efforts in many laboratories, the binding site(s) for TSH and TRAb on the TSHR have not been well characterized as yet and lessons learned from the discovery of naturally occurring amino acid mutations of the TSHR confirm the complexity of the hormone and autoantibody binding sites. Future progress in producing large amounts of pure TSHR as well as monoclonal TRAbs, followed by crystallographic analysis of TSHR-TSH complexes and TSHR-TRAb complexes, should be helpful in providing a better insight into the relationship between TSHR structure and function. 相似文献
77.
With regard to its chemical structure, methcathinone is to cathinone what methamphetamine is to amphetamine. Although it is a drug of abuse outside the United States, methcathione is only recently making an appearance on the clandestine market in this country and has just been classified a Schedule I substance under the Emergency Scheduling Act. We have previously demonstrated that racemic methcathinone produces locomotor stimulation in mice, and substitutes for cocaine and (+)amphetamine in rats trained to discriminate either cocaine or (+)amphetamine, respectively, from saline in tests of stimulus generalization. Because an enantiomeric potency comparison has never been reported for the optical isomers of methcathinone, in the present investigation we synthesized samples of S(-)- and R(+)methcathinone and compared them for their ability: a) to produce locomotor stimulation in mice, b) to elicit cocaine-like responding in rats trained to discriminate 8.0 mg/kg of cocaine from saline vehicle, and c) to elicit (+)-amphetamine-appropriate responding in rats trained to discriminate 1.0 mg/kg of (+)amphetamine from saline vehicle. S(-)Methcathinone was about twice as potent as S(+)amphetamine and three to five times more potent than R(+)methcathinone in the three pharmacologic assays. We conclude that both optical isomers possess central stimulant character, but that S(-)methcathinone is somewhat more potent than R(+)methcathinone. 相似文献
78.
79.
H Linhart BR Gundlach S Sopper U Dittmer K M?tz-Rensing EM Kuhn J Müller G Hunsmann C Stahl-Hennig K Uberla 《Canadian Metallurgical Quarterly》1997,13(7):593-599
We examined the immunohistochemical expression of proliferating-cell nuclear antigen (PCNA) and p53 proteins in dysplasia and intramucosal carcinoma of the esophagus. Immunohistochemistry was performed with monoclonal antibodies directed against PCNA and p53. We used surgically resected specimens from 29 patients who had a total of 55 lesions of severe dysplasia (n = 16), intraepithelial carcinoma (n = 21), and mucosal carcinoma (n = 18). The mean PCNA index with immunoreactivity for p53 was 48.9 +/- 6.5 in areas of severe dysplasia (n = 7), 58.2 +/- 7.3 in areas of intraepithelial carcinoma (n = 10), and 71.4 +/- 9.3 in the invasive areas of mucosal carcinoma (n = 10). The mean PCNA index without immunoreactivity for p53 was 41.2 +/- 5.5 in areas of severe dysplasia (n = 9), 48.0 +/- 7.4 in areas of intraepithelial carcinoma (n = 11), and 63.7 +/- 9.1 in invasive areas of mucosal carcinoma (n = 8). The PCNA indices of the areas of severe dysplasia with immunoreactivity for p53 were significantly lower than those of intraepithelial carcinoma and mucosal carcinoma with immunoreactivity for p53. Similarly, the PCNA indices of severe dysplasia without immunoreactivity for p53 were significantly lower than those of intraepithelial carcinoma and mucosal carcinoma without immunoreactivity for p53. These results thus suggest that severe dysplasia has a lower proliferative potential than carcinoma and may therefore represent a precancerous lesion. 相似文献
80.