全文获取类型
收费全文 | 3103篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
综合类 | 2篇 |
化学工业 | 104篇 |
金属工艺 | 19篇 |
机械仪表 | 16篇 |
建筑科学 | 41篇 |
矿业工程 | 3篇 |
能源动力 | 24篇 |
轻工业 | 144篇 |
水利工程 | 6篇 |
石油天然气 | 8篇 |
无线电 | 112篇 |
一般工业技术 | 158篇 |
冶金工业 | 2360篇 |
原子能技术 | 14篇 |
自动化技术 | 94篇 |
出版年
2022年 | 11篇 |
2021年 | 24篇 |
2018年 | 9篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 31篇 |
2012年 | 24篇 |
2011年 | 24篇 |
2010年 | 19篇 |
2009年 | 22篇 |
2008年 | 32篇 |
2007年 | 35篇 |
2006年 | 33篇 |
2005年 | 35篇 |
2004年 | 22篇 |
2003年 | 34篇 |
2002年 | 28篇 |
2001年 | 21篇 |
2000年 | 25篇 |
1999年 | 90篇 |
1998年 | 732篇 |
1997年 | 440篇 |
1996年 | 266篇 |
1995年 | 149篇 |
1994年 | 125篇 |
1993年 | 132篇 |
1992年 | 41篇 |
1991年 | 36篇 |
1990年 | 42篇 |
1989年 | 25篇 |
1988年 | 38篇 |
1987年 | 38篇 |
1986年 | 43篇 |
1985年 | 34篇 |
1984年 | 12篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 26篇 |
1980年 | 26篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 65篇 |
1976年 | 135篇 |
1975年 | 13篇 |
1974年 | 10篇 |
1973年 | 9篇 |
1972年 | 10篇 |
1970年 | 8篇 |
1926年 | 6篇 |
排序方式: 共有3119条查询结果,搜索用时 0 毫秒
31.
32.
One hundred and seven consecutive patients presenting with significant peptic ulcer haemorrhage were randomised to endoscopic injection with 3-10 ml of 1:100,000 adrenaline (55 patients, group 1) or to a combination of adrenaline and 5% ethanolamine (52 patients, group 2). All had major stigmata of haemorrhage and endoscopic injection was undertaken by a single endoscopist. The groups were well matched with regard to risk factors. Rebleeding occurred in eight of the group 1 patients and seven in the group 2 patients; surgical operation rates, median blood transfusion requirements, and hospital stay were similar in both groups. The efficacy of either form of injection was similar whether patients presented with active bleeding or a non-bleeding visible vessel. No complications occurred. In patients presenting with significant peptic ulcer bleeding, the addition of a sclerosant confers no advantage over injection with adrenaline alone. 相似文献
33.
Perchloric acid (70%) was used to create simulated periapical lesions in tooth sockets of 15 dentate cadaver jaw specimens. Using the Trophy USA direct digital radiographic system, linear images were captured at selected time intervals after initial acid application and altered by contrast reversal, pseudocolor enhancement, and two forms of histogram equalization. The 525 total images were randomized for display on a computer monitor for evaluation by five endodontists. Images were evaluated twice by each rater, with viewings 1 to 2 wk apart. Statistical analysis determined interrater variability, intrarater reproducibility, and the relative merits of each enhancement technique. At 8, 12, 16, and 24 h after acid application, both techniques of histogram equalization yielded a statistically significant improvement over reverse contrast in perception of periapical patholais. Linear and pseudocolor-enhanced images were also significantly more diagnostic than reverse contrast at 12, 16, and 24 h. Intrarater reproducibility showed moderate agreement, but analysis showed only a fair level of interrater agreement. 相似文献
34.
LM East CJ Savage JL Traub-Dargatz CE Dickinson RP Ellis 《Canadian Metallurgical Quarterly》1998,212(11):1751-1756
OBJECTIVE: To identify clinical signs, physical examination findings, results of diagnostic tests, treatments administered, and clinical outcome of neonatal foals with enterocolitis associated with Clostridium perfringens infection. DESIGN: Retrospective study. ANIMALS: 54 neonatal foals. RESULTS: Most foals had acute onset of obtunded mentation, colic, or diarrhea and developed leukopenia, neutropenia, an abnormally high number of band neutrophils, toxic WBC, and hypoproteinemia within 24 hours after admission, despite high serum IgG concentrations (> 800 mg/dl). Abdominocentesis and abdominal radiography of some foals revealed exudative peritonitis and gaseous distention of the small and large intestine, respectively. Cytologic examination of feces revealed spores or gram-positive rods in 8 of 10 foals. The most common genotypes of C perfringens isolates were type A and C, alone or in combination. Treatment did not alter mortality rate for most foals that had a positive culture for C perfringens type C. Of 54 foals, 29 (54%) that had C perfringens-associated enterocolitis died. Foals that had a culture that yielded C perfringens had higher sepsis scores, IgG concentrations, and mortality rates, compared with the overall hospital population of neonatal foals. CLINICAL IMPLICATIONS: Foals less than 7 days old that have enterocolitis associated with C perfringens infections, especially type C, have a guarded prognosis. Cytologic examination of feces to determine spore counts and detect rods may be a means for early identification of C perfringens infections. Polymerase chain reaction assays to determine genotype are important for designing preventive treatment regimens. 相似文献
35.
S Nielsen A Schmitz RE Knudsen J Dollerup CE Mogensen 《Canadian Metallurgical Quarterly》1994,87(12):747-754
In a double-blind, double-dummy, randomized, multi-centre study, the effects of bendroflumethiazide vs. enalapril on blood pressure, glycaemic control, lipoprotein concentrations and albuminuria were compared in non-proteinuric, hypertensive type 2 diabetic patients; they were treated for 20 weeks with either bendroflumethiazide 2.5-5.0 mg (n = 59) or enalapril 10-20 mg (n = 55). Age, fasting plasma glucose, HbA1c and BMI were similar in the groups. Systolic and diastolic blood pressure were reduced in both groups. Bendroflumethiazide was accompanied by minor but significant elevations in fasting plasma glucose and serum C-peptide. HbA1c was increased during both treatments. Lipoproteins and urinary albumin/creatinine ratio were stable. Bendroflumethiazide caused a decrease in serum potassium and an increase in serum urate. No significant correlations were observed between the decline in blood pressure and changes in the metabolic risk factors. Baseline levels of age, sex, BMI, blood pressure or urinary albumin/creatinine ratio were not related to changes in blood pressure, metabolic parameters or urinary albumin/creatinine ratio. 相似文献
36.
CE Boklage 《Canadian Metallurgical Quarterly》1996,11(10):2276-2284
This paper concerns a behaviour-driven weekday rhythm in conception rates in a large natural human population. From 1978 to 1991, North Carolina normal live single births arose from menstrual cycles which began on Monday in clear excess over other weekdays. Cycles beginning on Friday were also in excess. Cycles starting on Saturday and Sunday, or Wednesday and Thursday, each represented significantly less than one in seven of weekly totals. The source of the observed synchrony was a Sunday morning peak of coital frequency. Average cycles which began on Monday had their most fertile day on the most likely day for intercourse, translating a weekly insemination rhythm into a weekly conception rate rhythm. The secondary conception peak in Friday-onset cycles increased with age, to become the major peak for mothers aged > 30 years. We interpret this to represent a previously unreported second type of cycle with a modal follicular phase length of 10 days, the frequency of which increases with age. Several large groups of anomalous human births depart significantly from the weekday rhythm of normal conceptions. These outcomes parallel results of experimental interference with fertilization timing in estruative mammals. We believe that this implicates anomalous fertilization timing in several of the most numerous anomalies of human prenatal development. 相似文献
37.
Isolated left atrial mural endocarditis is rare. We report a case where the diagnosis was made clinically and supported by blood cultures and transoesophageal echocardiography. Appropriate intravenous antibiotics were administered and serial transoesophageal echocardiograms helped in monitoring the decrease in size and final disappearance of the vegetation, thus avoiding the need for surgical intervention. 相似文献
38.
39.
Collision Detection for Animation using Sphere-Trees 总被引:13,自引:0,他引:13
The detection of collisions between moving polyhedral objects is one of the most computationally intensive tasks in the computer animation process. The use of object-oriented techniques to encapsulate data within the objects' structures compounds this problem through the requirement for inter-object message passing in order to obtain geometric information for collision detection. The REALISM system decreases the time for collision detection by using a three stage process. The first stage identifies objects in the same locality using a global bounding volume table. The second stage locates regions of possible collision using a sphere-tree data structure (a hierarchical tree of spheres based on octree-type spatial subdivision). The final stage finds intersections between polygonal faces of the objects that are contained within the intersecting pairs of leaf nodes. Hence the algorithm uses a spherical geometry approximation rapidly to locate regions of potential collisions and then uses a local intersection test with actual object geometry information. The system is therefore fast and accurate. Tests for various geometric objects support this and show performance improvements of jive times over traditional polyhedral intersection tests. 相似文献
40.
CE Michel 《Canadian Metallurgical Quarterly》1996,114(9):1134-5; discussion 1135