全文获取类型
收费全文 | 2037篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 106篇 |
金属工艺 | 11篇 |
机械仪表 | 18篇 |
建筑科学 | 60篇 |
矿业工程 | 1篇 |
能源动力 | 15篇 |
轻工业 | 104篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 73篇 |
一般工业技术 | 64篇 |
冶金工业 | 1493篇 |
原子能技术 | 6篇 |
自动化技术 | 84篇 |
出版年
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2018年 | 4篇 |
2017年 | 10篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 31篇 |
2012年 | 22篇 |
2011年 | 29篇 |
2010年 | 26篇 |
2009年 | 24篇 |
2008年 | 30篇 |
2007年 | 30篇 |
2006年 | 32篇 |
2005年 | 18篇 |
2004年 | 21篇 |
2003年 | 20篇 |
2002年 | 12篇 |
2001年 | 9篇 |
2000年 | 16篇 |
1999年 | 68篇 |
1998年 | 480篇 |
1997年 | 254篇 |
1996年 | 175篇 |
1995年 | 114篇 |
1994年 | 79篇 |
1993年 | 118篇 |
1992年 | 21篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 17篇 |
1988年 | 31篇 |
1987年 | 23篇 |
1986年 | 21篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 4篇 |
1978年 | 11篇 |
1977年 | 34篇 |
1976年 | 75篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1968年 | 3篇 |
1965年 | 2篇 |
排序方式: 共有2055条查询结果,搜索用时 187 毫秒
211.
PURPOSE: Extracorporeal membrane oxygenation (ECMO) is an accepted therapy for neonatal pulmonary failure, but its use in older children has been controversial. METHODS: Over 13 years, 55 children (ages, 3 months to 16 years) were treated with venoarterial or venovenous ECMO. The diagnoses were viral, bacterial, or fungal pneumonia (24 patients); hydrocarbon or gastric aspiration (n = 10); adult respiratory distress syndrome (ARDS), sepsis, near drowning (n = 15); pulmonary contusion (n = 2); airway obstruction (n = 3); pulmonary artery foreign body (n = 1). Pre-ECMO blood gas ranges (and means) were PO2, 21 to 100 (n = 44); PCO2, 23 to 125 (n = 72); pH, 6.81 to 7.55 (n = 7.11). RESULTS: All patients received inotropes, and 38 required dialysis or hemofiltration. ECMO was used for 20 to 613 hours (mean, 196 hours). Patient complications included cannulation site hemorrhage (n = 40), renal failure (n = 10), seizures (n = 8), stroke (n = 3), and cerebral hemorrhage (n = 2). Twenty-five patients (45%) survived ECMO, with 21 long-term survivors (10 pneumonia, five aspiration, five ARDS, one pulmonary contusion), five of whom have mild to moderate neurological deficit. Patients with combinations of pulmonary, cardiac, and renal failure, or sepsis did not survive. CONCLUSIONS: ECMO is an invasive technique that can be life saving in the child with isolated respiratory failure, but its usefulness in children with multiorgan failure is less certain. 相似文献
212.
213.
The assessment of the performance of organic and mineral-based insulation products used in exterior walls and attics in traditional Danish housing estate was evaluated. The assessment covered the ability of the materials to be handled on site as well as measurements of the performance of the materials once installed and exposed to normal use of the dwellings and Danish weather conditions over a 2-year period. Evaluations were based on, on-site observations, thermographic observations and measurements of temperature and moisture conditions within the different materials used. Eight different products were used for thermal insulation including six organic and two mineral fibre materials. Loose-fill material and predefined fixed-shape products were used. The eight different products were installed in 16 dwellings, two neighbouring dwellings were insulated with each product. Exterior walls were constructed without PE vapour barriers while ceilings were constructed with PE vapour barriers. 相似文献
214.
P Vestergaard RW Licht A Brodersen NA Rasmussen H Christensen T Arngrim B Gr?nvall E Kristensen I Poulstrup R Wentzer Licht 《Canadian Metallurgical Quarterly》1998,98(4):310-315
Recently, the availability of 5-hydroxytryptamine-3 antagonists has provided better protection from chemotherapy-induced emesis. These drugs, in combination with dexamethasone, are more expensive but more cost-effective than the alternative antiemetic regimens in the prevention of acute emesis induced by high single dose and low and repeated doses of cisplatin and, probably, of acute emesis induced by moderately emetogenic chemotherapy. In the prevention of emesis induced by oral cyclophosphamide-methotrexate-fluorouracil and in the prevention of delayed emesis induced by cisplatin and moderately emetogenic chemotherapy, the most cost-effective choices are represented, respectively, by a combination of intravenous dexamethasone on day 1 and 8 plus 14-day oral metoclopramide (a combination of oral dexamethasone plus metoclopramide and oral dexamethasone alone). In all cases, the 5-hydroxytryptamine-3 antagonists should be used only in patients in whom the most cost-effective antiemetic regimens either fail or are not tolerated. 相似文献
215.
216.
SV Kuruttukulam S Krishnaswami ST Chandy TR Muralidharan 《Canadian Metallurgical Quarterly》1995,47(5):477-480
Seventy two consecutive patients without a history of diabetes and normal fasting plasma glucose were included in this study of insulin levels. Standard oral glucose tolerance test with 75 gm glucose and fasting and two hour insulin levels were estimated in all patients. Coronary artery disease (CAD) was confirmed or excluded by selective coronary arteriography. In 20 patients, CAD was diagnosed by electrocardiographic (ECG) and clinical evidence of earlier myocardial infarction. Mean fasting plasma insulin was 31.40 +/- 22.2 IU/dl in the CAD positive and 32.3 +/- 13.6 IU/dl in the CAD negative group. The mean two hour plasma insulin was 274.6 +/- 301.1 IU/dl in the CAD positive and 104.8 +/- 74.9 IU/dl in the CAD negative group (p < 0.04). Two hour plasma insulin levels were significantly higher in patients with atherosclerotic coronary artery disease. It is concluded that the estimation of a two hour plasma insulin level after 75 gm of glucose load, could help differentiate CAD from normals. 相似文献
217.
G Ntirampemba BE Langlois DD Archbold TR Hamilton-Kemp MM Barth 《Canadian Metallurgical Quarterly》1998,61(10):1352-1357
OBJECTIVE: The authors tested the hypothesis that eye tracking disorder in schizophrenia is associated with neurological signs. METHOD: The subjects were 93 normal comparison subjects and 59 schizophrenic patients. They were evaluated with the Neurological Evaluation Scale, a standardized rating instrument that assesses sensory integration, motor coordination, sequencing of complex motor acts, and other neurological signs. Also, the schizophrenic patients' smooth-pursuit eye movements were tested in response to a 0.3-Hz sinusoidal target by means of infrared oculography. They were divided into those with (N=18) and without (N=41) eye tracking disorder by using a previously described method, which was based on mixture analysis of the distribution of position root mean square error. RESULTS: The patients with eye tracking disorder had significantly worse performance than the patients without eye tracking disorder with respect to sensory integration, and the effect size was moderate to large. In comparison with the normal subjects, both patient subgroups had significantly worse performance on all of the Neurological Evaluation Scale subscales. CONCLUSIONS: Although neurological signs are present generally in schizophrenia, poor sensory integration is particularly pronounced in patients with eye tracking disorder. A review of the literature shows that the two abnormalities have strikingly similar patterns of validators, including 1) familial aggregation, 2) premorbid presence, 3) syndromal specificity, 4) trait status, and 5) association with the deficit syndrome. Poor sensory integration and eye tracking disorder in schizophrenia may be various manifestations of a common, underlying pathophysiological process. 相似文献
218.
LW Ruddock HM Webb SP Ruston C Cheesman RB Freedman TR Hirst 《Canadian Metallurgical Quarterly》1996,35(50):16069-16076
The non-covalently associated B-subunit moieties of AB5 toxins, such as cholera toxin and related diarrheagenic enterotoxins, exhibit exceptional pH stability and remain pentameric at pH values as low as 2.0. Here, we investigate the structural basis of a pH-dependent conformational change which occurs within the B5 structure of Escherichia coli heat-labile enterotoxin (EtxB) at around pH 5.0. The use of far-UV CD and fluorescence spectroscopy showed that EtxB pentamers undergo a fully reversible pH-dependent conformational change with a pKa of 4.9 +/- 0.1 (R2 = 0.999) or 5.13 +/- 0.01 (R2 = 0.999), respectively. This renders the pentamer susceptible to SDS-mediated disassembly and decreases its thermal stability by 18 degrees C. A comparison of the pH-dependence of the structural change in EtxB5, with that of a mutant containing a Ser substitution at His 57, revealed that the pKa of the conformational change was shifted from ca. 5.1 to 4.4. This finding suggests that protonation of the imidazole side chain of His 57 might facilitate disruption of a spatially adjacent salt bridge, located between Glu 51 and Lys 91 in each B-subunit, thus triggering the conformational change in the pentameric structure. The pH-dependent conformational change was found to be inhibited when B-subunits bound to monosialoganglioside, GMI; and to have no effect on the stability of interaction between A- and B-subunits within the AB5 complex. This suggests that the conformational change is unlikely to have a direct involvement in toxicity. Conservation of the pH-dependent conformational change in the AB5 toxin family, combined with the potential exposure of the hydrophobic core of beta-barrel in the monomeric units, leads to the proposal that the conformational change may be the common feature that ensures the secretion of these proteins from the Vibrionaceae. 相似文献
219.
220.
As part of a prospective survey of medical students' conditions and of the different kinds of influence they are subjected to during their study periods, we looked into the question of from which social strata the students were recruited. Two hundred and fifty-four (79%) of 323 medical students matriculated during the summer of 1992 answered a structured questionnaire forwarded to them. One hundred and thirty-one (52%) medical students were recruited from the highest social class (I), whereas only 19 (7%) were recruited from the lowest social class (V). In comparison, the underlying population in the age groups relevant for the survey is made up as follows: 7% in social class I and 20% in social class V. A comparison with earlier surveys shows that only insignificant changes in the medical students' social class profiles have taken place in spite of the introduction of better possibilities of financing medical studies irrespective of social class affiliations. 相似文献