全文获取类型
收费全文 | 1551篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 5篇 |
金属工艺 | 1篇 |
轻工业 | 5篇 |
水利工程 | 1篇 |
无线电 | 2篇 |
一般工业技术 | 5篇 |
冶金工业 | 1528篇 |
原子能技术 | 1篇 |
自动化技术 | 3篇 |
出版年
2021年 | 1篇 |
2017年 | 1篇 |
2013年 | 1篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2005年 | 1篇 |
2003年 | 2篇 |
1999年 | 37篇 |
1998年 | 466篇 |
1997年 | 275篇 |
1996年 | 174篇 |
1995年 | 101篇 |
1994年 | 71篇 |
1993年 | 109篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 20篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 28篇 |
1985年 | 18篇 |
1983年 | 2篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1978年 | 3篇 |
1977年 | 39篇 |
1976年 | 84篇 |
1975年 | 3篇 |
1969年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1552条查询结果,搜索用时 15 毫秒
91.
DP McHale S Mitchell S Bundey L Moynihan DA Campbell CG Woods NJ Lench RF Mueller AF Markham 《Canadian Metallurgical Quarterly》1999,64(2):526-532
Cerebral palsy has an incidence of approximately 1/500 births, although this varies between different ethnic groups. Genetic forms of the disease account for approximately 1%-2% of cases in most countries but contribute a larger proportion in populations with extensive inbreeding. We have clinically characterized consanguineous families with multiple children affected by symmetrical spastic cerebral palsy, to locate recessive genes responsible for this condition. The eight families studied were identified from databases of patients in different regions of the United Kingdom. After ascertainment and clinical assessment, we performed a genomewide search for linkage, using 290 polymorphic DNA markers. In three families, a region of homozygosity at chromosome 2q24-q25 was identified between the markers D2S124 and D2S148. The largest family gave a maximum LOD score of 3.0, by multipoint analysis (HOMOZ). The maximum combined multipoint LOD score for the three families was 5.75. The minimum region of homozygosity is approximately 5 cM between the markers D2S124 and D2S2284. We have shown that a proportion of autosomal recessive symmetrical spastic cerebral palsy maps to chromosome 2q24-25. The identification of genes involved in the etiology of cerebral palsy may lead to improved management of this clinically intractable condition. 相似文献
92.
93.
V Mooser A Maillard C Bonny M Steinmann P Shaw DP Yarnall DK Burns DF Schorderet P Nicod G Waeber 《Canadian Metallurgical Quarterly》1999,55(2):202-208
Islet-brain 1 (IB1), a regulator of the pancreatic beta-cell function in the rat, is homologous to JIP-1, a murine inhibitor of c-Jun amino-terminal kinase (JNK). Whether IB1 and JIP-1 are present in humans was not known. We report the sequence of the 2133-bp human IB1 cDNA, the expression, structure, and fine-mapping of the human IB1 gene, and the characterization of an IB1 pseudogene. Human IB1 is 94% identical to rat IB1. The tissue-specific expression of IB1 in human is similar to that observed in rodent. The IB1 gene contains 12 exons and maps to chromosome 11 (11p11.2-p12), a region that is deleted in DEFECT-11 syndrome. Apart from an IB1 pseudogene on chromosome 17 (17q21), no additional IB1-related gene was found in the human genome. Our data indicate that the sequence and expression pattern of IB1 are highly conserved between rodent and human and provide the necessary tools to investigate whether IB1 is involved in human diseases. 相似文献
94.
95.
96.
JB Prins CU Niesler CM Winterford NA Bright K Siddle S O'Rahilly NI Walker DP Cameron 《Canadian Metallurgical Quarterly》1997,46(12):1939-1944
Tumor necrosis factor-alpha (TNF-alpha) production by adipocytes is elevated in obesity, as shown by increased adipose tissue TNF-alpha mRNA and protein levels and by increased circulating concentrations of the cytokine. Furthermore, TNF-alpha has distinct effects on adipose tissue including induction of insulin resistance, induction of leptin production, stimulation of lipolysis, suppression of lipogenesis, induction of adipocyte dedifferentiation, and impairment of preadipocyte differentiation in vitro. Taken together, these effects all tend to decrease adipocyte volume and number and suggest a role for TNF-alpha in limiting increase in fat mass. The aim of the present study was to determine if TNF-alpha could induce apoptosis in human adipose cells, hence delineating another mechanism by which the cytokine could act to limit the development of, or extent of, obesity. Cultured human preadipocytes and mature adipocytes in explant cultures were exposed in vitro to human TNF-alpha at varying concentrations for up to 24 h. Apoptosis was assessed using morphological (histology, nuclear morphology following acridine orange staining, electron microscopy) and biochemical (demonstration of internucleosomal DNA cleavage by gel electrophoresis and of annexin V staining using immunocytochemistry) criteria. In control cultures, apoptotic indexes were between 0 and 2.3% in all experiments. In the experimental systems, TNF-alpha induced apoptosis in both preadipocytes and adipocytes, with indexes between 5 and 25%. Therefore, TNF-alpha induces apoptosis of human preadipocytes and adipocytes in vitro. In view of the major metabolic role of TNF-alpha in human adipose tissue, and the knowledge that adipose tissue is dynamic (with cell acquisition via preadipocyte replication/differentiation and cell loss via apoptosis), these findings describe a further mechanism whereby adipose tissue mass may be modified by TNF-alpha. 相似文献
97.
98.
G. A. Carini G. S. Camarda Z. Zhong D. P. Siddons A. E. Bolotnikov G. W. Wright B. Barber C. Arnone R. B. James 《Journal of Electronic Materials》2005,34(6):804-810
High-energy transmission x-ray diffraction techniques have been applied to investigate the crystal quality of CdZnTe (CZT).
CdZnTe has shown excellent performance in hard x-ray and gamma detection; unfortunately, bulk nonuniformities still limit
spectroscopic properties of CZT detectors. Collimated high-energy x-rays, produced by a superconducting wiggler at the National
Synchrotron Light Source’s X17B1 beamline, allow for a nondestructive characterization of thick CZT samples (2–3 mm). In order
to have complete information about the defect distribution and strains in the crystals, two series of experiments have been
performed. First, a monochromatic 67 keV x-ray beam with the size of 300×300 μm2 was used to measure the rocking curves of CZT crystals supplied by different material growers. A raster scan of a few square
centimeter area allowed us to measure the full-width at half-maximum (FWHM) and shift in the peak position across the crystal.
The rocking curve peak position and its FWHM can be correlated with local stoichiometry variations and other local defects.
Typically, the FWHM values ranging from 8.3 arcsec to 14.7 arcsec were measured with the best crystal used in these measurements.
Second, transmission white beam x-ray topography (WBXT) was performed by using a 22 mm×200 μm beam in the energy range of 50 keV to 200 keV. These types of measurements allowed for large area, high-resolution (50 μm) scans of the samples. Usually, this technique is used to visualize growth and process-induced defects, such as dislocations,
twins, domains, inclusions, etc. the difference in contrast shows different parts of the crystal that could not be shown otherwise.
In topography, good contrast is indicative of a high quality of the sample, while blurred gray shows the presence of defects.
Correlation with other techniques (e.g., infrared (IR) mapping and gamma mapping) was also attempted. Our characterization
techniques, which use highly penetrating x-rays, are valid for in-situ measurements, even after electrical contacts have been
formed on the crystal in a working device. Thus, these studies may lead to understanding the effects of the defects on the
device performance and ultimately to improving the quality of CZT material required for device fabrication. It is important
to study crystals from different ingot positions (bottom, center, and top); consequently, more systematic studies involving
scans from center to border are planned. 相似文献
99.
100.
The interactions between the tumor and its host are complex, and many aspects of the immune system appear to be adversely affected directly or indirectly by the presence of the tumor. Virtually all of the processes involved in immune induction and action have been implicated in the observed deficient response in tumor-bearing patients. Improved understanding and molecular analysis of the mechanisms underlying the escape of tumors from immune surveillance may lead to the development of novel strategies for the prevention of T-cell immunosuppression in cancer patients, the development of novel immunotherapeutic strategies, and potentially prevention of tumor progression or development. 相似文献