全文获取类型
收费全文 | 2533篇 |
免费 | 43篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 31篇 |
综合类 | 1篇 |
化学工业 | 251篇 |
金属工艺 | 38篇 |
机械仪表 | 13篇 |
建筑科学 | 46篇 |
矿业工程 | 2篇 |
能源动力 | 37篇 |
轻工业 | 88篇 |
水利工程 | 12篇 |
石油天然气 | 2篇 |
无线电 | 146篇 |
一般工业技术 | 210篇 |
冶金工业 | 1522篇 |
原子能技术 | 9篇 |
自动化技术 | 172篇 |
出版年
2023年 | 15篇 |
2022年 | 25篇 |
2021年 | 38篇 |
2020年 | 29篇 |
2019年 | 33篇 |
2018年 | 34篇 |
2017年 | 38篇 |
2016年 | 30篇 |
2015年 | 18篇 |
2014年 | 34篇 |
2013年 | 66篇 |
2012年 | 56篇 |
2011年 | 57篇 |
2010年 | 44篇 |
2009年 | 44篇 |
2008年 | 62篇 |
2007年 | 44篇 |
2006年 | 28篇 |
2005年 | 32篇 |
2004年 | 29篇 |
2003年 | 27篇 |
2002年 | 20篇 |
2001年 | 22篇 |
2000年 | 17篇 |
1999年 | 70篇 |
1998年 | 457篇 |
1997年 | 261篇 |
1996年 | 150篇 |
1995年 | 100篇 |
1994年 | 84篇 |
1993年 | 79篇 |
1992年 | 12篇 |
1991年 | 34篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 27篇 |
1987年 | 27篇 |
1986年 | 26篇 |
1985年 | 18篇 |
1984年 | 12篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 19篇 |
1980年 | 22篇 |
1979年 | 9篇 |
1978年 | 14篇 |
1977年 | 50篇 |
1976年 | 100篇 |
1975年 | 10篇 |
1974年 | 12篇 |
排序方式: 共有2580条查询结果,搜索用时 15 毫秒
1.
Using an integrated process of data and modeling in HRA 总被引:1,自引:0,他引:1
John Wreathall Dennis Bley Emilie Roth Jordan Multer Thomas Raslear 《Reliability Engineering & System Safety》2004,83(2):221
The paper describes an approach taken to estimate the probabilities of failure associated with various railroad tasks to prevent accidents (principally collisions and derailments). These probabilities were estimated using an expert elicitation process that used partially relevant data available from a variety of databases and that were filtered and scaled to make them more directly relevant to the analyses being performed. Extensive qualitative studies were performed prior to the elicitation process to identify relevant contexts under which the tasks can be performed. 相似文献
2.
A cost comparison of balloon angioplasty and stenting versus endarterectomy for the treatment of carotid artery stenosis 总被引:1,自引:0,他引:1
WD Jordan GD Roye WS Fisher D Redden HA McDowell 《Canadian Metallurgical Quarterly》1998,27(1):16-22; discussion 22-4
PURPOSE: Percutaneous transluminal angioplasty with stenting (PTAS) of the carotid artery has been advocated as an alternative treatment for high-grade stenosis. Rationale for this approach includes less morbidity, shorter recovery, and lower cost when compared with carotid endarterectomy (CEA). METHODS: The clinical results and hospital charges of patients who underwent elective treatment for carotid stenosis were reviewed. During a concurrent 14-month period, 218 patients were admitted 229 times for 234 procedures for the treatment of 239 carotid bifurcation stenoses, 109 by PTAS and 130 by CEA. Hospital charges were reviewed for each hospitalization and were categorized according to radiology, operating room, cardiac catheterization laboratory, and all other hospital charges. RESULTS: The combined incidence of postprocedure strokes and deaths were: PTAS, eight strokes (7.7%) and one death (0.9%); CEA, two strokes (1.5%) and two deaths (1.5%). Total hospital charges per admission for the two groups were $30,140 for PTAS and $21,670 for CEA. The average postprocedure length of stay for PTAS was 2.9 days (median, 2 days) and for CEA was 3.1 days (median, 3 days). Cardiac catheterization laboratory charges for the PTAS group were $12,968, whereas the operating room charges for the CEA group were $4263. When hospitalizations that were extended by complications were excluded, the average total charges for the PTAS group (n = 84) dropped to $24,848 (mean length of stay, 1.9 days) and for the CEA group (n = 111) to $19,247 (mean length of stay, 2.6 days). CONCLUSIONS: After evaluating hospital charges, PTAS for the treatment of carotid stenosis cannot currently be justified on the basis of reduced costs alone. With future cost-containing measures, total hospital charges can be reduced in both groups. 相似文献
3.
IG Sumner A Vaughan R Eisenthal RW Pickersgill AJ Owen PW Goodenough 《Canadian Metallurgical Quarterly》1993,1164(3):243-251
Papaya proteinase omega (pp omega) has been purified from dried latex both by immunoaffinity and traditional methods. Kinetic analysis revealed that (1), the pp omega-catalysed hydrolysis of N-benzoyl-L-arginine p-nitroanilide (BApNA) has a lower specificity (kcat/Km) than the same reaction catalysed by papain; (2), the pp omega-catalysed hydrolysis of a tripeptide substrate having phenylalanine at the second position (S2-site) showed a more similar specificity to that catalysed by papain; (3), the significant difference between the two enzymes is that steady state kinetics with both L-BApNA and a tripeptide enables the identification in pp omega of other ionizations affecting binding. The active sites of papain and pp omega can therefore be distinguished by pH-dependence of kcat/Km. 相似文献
4.
Off-Site Exposure to Respirable Aerosols Produced during the Disk-Incorporation of Class B Biosolids
Swee Yang Low Tania Paez-Rubio Carolina Baertsch Matthew Kucharski Jordan Peccia 《Canadian Metallurgical Quarterly》2007,133(10):987-994
Field experiments were conducted at a Class B biosolids land application site in central Arizona to measure, model, and source-track the off-site transport of aerosols emitted when biosolids were disk-incorporated into soils. Real-time PM10 monitoring provided time-resolved aerosol information sufficient for verifying both off-site concentration and off-site exposure time model results. Under the conditions considered and at a distance of 165?m from the aerosol source, biosolids disk-incorporation resulted in an intermittent exposure to biosolids-derived aerosol concentration between 15 and 40?μg/m3 and an inhalable biosolids dose between 2 and 8?μg. Transport modeling predicted that these doses will decrease with increasing wind speed. In addition, three DNA sequence-based biosolids source tracking methods were applied to aerosol samples and confirmed the presence of biosolids in aerosols at 5, 65, and 165?m from the aerosol source. Field measurements and modeling indicate that the nature of biosolids-derived aerosol exposure is a series of intermittent high concentration puffs, rather than a continuous low concentration. 相似文献
5.
Renal length has been measured by ultrasound in 237 subjects with homozygous sickle cell (SS) disease, 147 with sickle cell-hemoglobin C (SC) disease, and in 78 age-matched controls with a normal hemoglobin (AA) genotype. As expected, renal length increased with age in all genotypes but mean length was significantly greater in SS disease compared with SC disease (mean difference 4.3 mm after adjustment for height) and significantly greater in both genotypes than in AA controls (SS/AA difference 9.2 mm, SC/AA difference 5.0 mm after adjustment for height). Examination of relationships between renal length and some hematological indices (hemoglobin, fetal hemoglobin, reticulocyte counts, alpha thalassemia status) in SS or SC disease showed only a significant negative correlation with hemoglobin and positive correlation with reticulocyte count in SS disease. Further analysis suggested that the stronger relationship was between renal length and high reticulocyte count. The mechanism of renal enlargement is unknown although glomerular hypertrophy and increased renal blood volume are likely contributors. 相似文献
6.
VC Jordan 《Canadian Metallurgical Quarterly》1997,6(3):257-259
INTRODUCTION: Parvovirus B19 infection is frequent. Primary infection leads to diverse skin manifestations including the recently described gloves-and-socks papulopurpura. CASE REPORT: A patient presented with a papulopurpuric eruption on the nose, hands, feet and perineum with cheilitis and high-grade fever. Parvovirus B19 serology showed characteristic IgG on the 15th day after the initial eruption demonstrating the seroconversion. Cold agglutinins were positive during the eruption and negative after regression. DISCUSSION: The gloves-and-socks papulopurpura syndrome was initially described in 1990. Since that time 20 cases have been reported. In 7 cases, primary parvovirus B19 infection was proven and viral infections were suspected in the others (measles, coxsackie B6, hepatitis B, Epstein-Barr virus). Our case evidenced here to undescribed skin manifestations and the development of cold agglutinins. The presence of cold agglutinins at eruption could explain the acral localizations observed in this syndrome. 相似文献
7.
MP Armon SW Yusuf K Latief SC Whitaker RH Gregson PW Wenham BR Hopkinson 《Canadian Metallurgical Quarterly》1997,84(2):178-180
BACKGROUND: Aortic aneurysm anatomy is crucial when considering patients for endovascular repair. The aim of this study was to determine the proportion of patients with aortic aneurysm suitable for endovascular repair with three different graft-stent systems. METHODS: Spiral computed tomographic angiography was used to assess the anatomy of 154 abdominal aortic aneurysms. Measurements were made of aneurysm neck length and diameter, renal artery to aortic bifurcation length, common iliac artery diameter and length, and external iliac artery diameter. Aneurysms were assessed for anatomical suitability for currently available aortoaortic, aortobi-iliac and aortouni-iliac devices. RESULTS: Six patients (4 per cent) had a distal aortic neck suitable for implantation of a straight aortic graft. Fifteen patients (10 per cent) had arterial anatomy suitable for implantation of a bifurcated graft and 85 (55 per cent) patients were suitable for endovascular repair with an aortouni-iliac graft. The primary reasons for unsuitability were: proximal neck length less than 1.5 cm (44 patients), proximal neck diameter greater than 3.0 cm (12), and angulation of the proximal neck (three). A further ten patients were considered unsuitable for an aortouni-iliac graft because of bilateral common iliac artery aneurysms (four), tortuous iliac arteries (four) and narrow external iliac arteries (two). CONCLUSION: The aortouni-iliac device has the widest applicability of the currently available endovascular systems but open repair remains the only option for a large proportion of patients. 相似文献
8.
9.
Previous research shows letter-fragment masks and non-letter-fragment fields have different effects on performance with briefly presented alphabetic targets. However, popular accounts of these differences ignore mask configuration. Over a series of experiments, configurational effects of letter-fragment (LF) and non-letter-fragment (NLF) masks were compared. When the configuration of LF masks matched word boundaries, performance with exterior letter pairs from words improved, whereas performance with illegal exterior-letter pairs and single letters was unaffected. When the same changes were made to NLF masks, only an overall drop in performance occurred, with no selective effect on target type. Although LF mask configuration selectively affected lexical processing, NLF mask configuration produced substantially different effects, indicating problems with contemporary accounts of masking differences that ignore influences of mask configuration. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
The effectiveness of a combined regimen of mifepristone and vaginal misoprostol for termination of pregnancies of 9-13 weeks of gestation was investigated in 120 UK abortion patients (median age, 22.1 years; median duration of amenorrhea, 10.3 weeks). Each woman received a single oral dose of 200 mg of mifepristone 36-48 hours before admission, at which time 800 mcg of misoprostol was administered vaginally. Where indicated, a further two doses of 400 mcg of misoprostol (vaginal or oral) were provided every 3 hours. All 120 women aborted on the day of prostaglandin administration; however, 6 women (5%) required exploratory curettage after the procedure for retained placenta. The median prostaglandin dose was 1200 mcg (range, 800-1600 mcg). The median time from misoprostol administration to abortion was 4.33 hours (range, 1.3-16.0 hours). 60 women (50%) required oral analgesics and 26 (22%) received parenteral analgesia. Diarrhea occurred in 38 women (32%). The median duration of bleeding after abortion was 12.5 days (range, 3-43 days). In questionnaires administered to 73 women, only 3 (4%) expressed dissatisfaction with medical abortion, because of pain or prolonged bleeding. The relatively high dose of misoprostol used in this study and the vaginal route of administration are presumed to account for the 95% success rate. Extension of medical abortion to later gestation times would decrease the need for surgery and expand women's choice of methods of pregnancy termination. 相似文献