全文获取类型
收费全文 | 2891篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 11篇 |
综合类 | 1篇 |
化学工业 | 116篇 |
金属工艺 | 8篇 |
机械仪表 | 9篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 9篇 |
轻工业 | 52篇 |
水利工程 | 2篇 |
石油天然气 | 10篇 |
无线电 | 38篇 |
一般工业技术 | 33篇 |
冶金工业 | 2554篇 |
原子能技术 | 6篇 |
自动化技术 | 45篇 |
出版年
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2017年 | 6篇 |
2014年 | 9篇 |
2013年 | 24篇 |
2012年 | 13篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 19篇 |
2007年 | 11篇 |
2006年 | 14篇 |
2005年 | 10篇 |
2004年 | 13篇 |
2003年 | 18篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 71篇 |
1998年 | 845篇 |
1997年 | 456篇 |
1996年 | 294篇 |
1995年 | 166篇 |
1994年 | 121篇 |
1993年 | 154篇 |
1992年 | 21篇 |
1991年 | 22篇 |
1990年 | 23篇 |
1989年 | 26篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1986年 | 28篇 |
1985年 | 19篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 54篇 |
1976年 | 158篇 |
1975年 | 7篇 |
1966年 | 10篇 |
1965年 | 13篇 |
1964年 | 7篇 |
1963年 | 11篇 |
1962年 | 11篇 |
1961年 | 12篇 |
1960年 | 11篇 |
排序方式: 共有2905条查询结果,搜索用时 15 毫秒
31.
Rett syndrome (RS), a neurodevelopmental disorder of unknown etiology occurring almost exclusively in females, is characterized by autistic-like behavior, motor dysfunction, loss of language skills, dementia, and microcephaly. This study is a follow-up and extension of a previously reported neuroimaging study of patients with RS. We replicated previously reported findings with a larger patient population, and the volumetric MRI analysis was extended to include an analysis of neuroanatomy of the posterior fossa. Twenty girls with RS were compared with individually age- and gender-matched normal controls. Patients with RS showed global reduction in gray- and white-matter volumes. The prefrontal, posterior-frontal, and anterior-temporal regions showed the largest bilateral decrease in gray-matter volume, whereas white-matter volume was uniformly reduced throughout the brain. We found confirmation for the preferential reduction in caudate nucleus volume. However, we observed no preferential reduction in midbrain volume despite a preferential reduction in the midsagittal area of this region. We also present an individual case comparison between monozygotic twins discordant for RS. 相似文献
32.
33.
Burkholderia pseudomallei is the causative agent of melioidosis, a disease increasingly recognized as an important cause of morbidity and mortality in many regions of the world. B. pseudomallei is a facultative intracellular pathogen capable of invading eukaryotic cells. We used Tn5-OT182 mutagenesis to generate mutants deficient in the ability to invade a human type II pneumocyte cell line (A549 cells). One of these mutants, AJ1D8, exhibited approximately 10% of the ability of the parental strain, 1026b, to invade A549 cells. There was no difference in the abilities of 1026b and AJ1D8 to resist killing by RAW macrophages or the human defensin HNP-1. The nucleotide sequence flanking the Tn5-OT182 integration in AJ1D8 was determined, and two open reading frames were identified. The predicted proteins shared considerable homology with two-component regulatory systems involved in the regulation of heavy-metal resistance in other organisms. AJ1D8 was 16-fold more sensitive to Cd2+ and twofold more sensitive to Zn2+ than was 1026b but was not sensitive to any of the other heavy metals examined. The B. pseudomallei two-component regulatory system, termed irlRS, complemented the invasion-deficient and heavy-metal-sensitive phenotype of AJ1D8 in trans. There was no significant difference between the virulence of AJ1D8 and that of 1026b in infant diabetic rats and Syrian hamsters, suggesting that the irlRS locus is probably not a virulence determinant in these animal models of acute B. pseudomallei infection. 相似文献
34.
MJ Prado AL Nicastri PL Costa T Rockman IL Tersariol HB Nader RT Barros EB Prado 《Canadian Metallurgical Quarterly》1997,30(7):865-872
The aim of the present study was to evaluate renal and liver distribution of two monoclonal immunoglobulin light chains. The chains were purified individually from the urine of patients with multiple myeloma and characterized as lambda light chains with a molecular mass of 28 kDa. They were named BJg (high amount of galactose residues exposed) and BJs (sialic acid residues exposed) on the basis of carbohydrate content. A scintigraphic study was performed on male Wistar rats weighing 250 g for 60 min after i.v. administration of 1 mg of each protein (7.4 MBq), as the intact proteins and also after carbohydrate oxidation. Images were obtained with a Siemens gamma camera with a high-resolution collimator and processed with a MicroDelta system. Hepatic and renal distribution were established and are reported as percent of injected dose. Liver uptake of BJg was significantly higher than liver uptake of BJs (94.3 vs 81.4%) (P < 0.05). This contributed to its greater removal from the intravascular compartment, and consequently lower kidney accumulation of BJg in comparison to BJs (5.7 vs 18.6%) (P < 0.05). After carbohydrate oxidation, there was a decrease in hepatic accumulation of both proteins and consequently a higher renal overload. The tissue distribution of periodate-treated BJg was similar to that of native BJs: 82.7 vs 81.4% in the liver and 17.3 vs 18.6% in the kidneys. These observations indicate the important role of sugar residues of Bence Jones proteins for their recognition by specific membrane receptors, which leads to differential tissue accumulation and possible toxicity. 相似文献
35.
36.
YT van der Schouw WA van den Beld GA van der Sanden RA Binkhorst FJ Gabre?ls AL Verbeek 《Canadian Metallurgical Quarterly》1993,35(7):608-613
The authors conducted an assessment study of newly developed motor performance items for the diagnosis of myopathy. 17 children who had had muscle biopsy for this diagnosis in the recent past were administered 14 items based on the measurement of static, dynamic and explosive muscle strength and muscle endurance. Individual items did not have perfect discriminative power, but the results were encouraging enough to warrant detailed study with combinations of the items, so that in future fewer children will have to undergo unnecessary muscle biopsies. 相似文献
37.
This paper presents the results of a longitudinal psychosocial study of 22 cranial trauma patients and 14 stroke patients from the time preceding injury (using retrospective data), through a 4-5 month intensive rehabilitation programme, to a follow-up 1 year after completion of the programme. Although the two groups of patients differed on several demographic and medical characteristics, essentially similar patterns for psychosocial decline following injury and improvement following rehabilitation could be observed. For both groups, the proportion in marital or cohabitational relationships returned to pre-injury levels, and for both groups the proportion requiring assistance in their living situation declined following rehabilitation, as did use of the health services. Virtually all patients in both groups had been in employment or undergoing education at the time of the injury, and although this percentage declined in practice to a small minority of both groups post-injury, there was a significant increase in the proportions working or in education following the rehabilitation programme. Similarly, the pattern of leisure-time activities in both groups declined post-injury and was restored following rehabilitation. Since both groups entered the programme at over 2.5 years post-injury, these generally encouraging results seem less likely to reflect spontaneous recovery than a beneficial effect of the programme itself. 相似文献
38.
39.
Detecting Deception in Children: Event Familiarity Affects Criterion-Based Content Analysis Ratings.
40.
In a study of how aviation expertise influences age differences in narrative processing, young and older pilots and nonpilots read and recalled aviation and general narratives. They chose referents for sentences referring to a protagonist or minor character mentioned 1 sentence (recent character) or 3 sentences (distant character) before this target sentence. All groups chose referents less accurately for sentences about distant and minor characters than about recent and protagonist characters, perhaps because these referents were less likely to be in working memory. Young readers and pilots were more accurate for distant and minor character target sentences in aviation narratives and recalled aviation narratives more accurately. Expertise did not reduce age differences. Expertise differences may reflect decreased demands on working memory capacity, and age declines may reflect reduced capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献