全文获取类型
收费全文 | 1517篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 4篇 |
综合类 | 3篇 |
化学工业 | 88篇 |
金属工艺 | 5篇 |
机械仪表 | 12篇 |
建筑科学 | 27篇 |
矿业工程 | 1篇 |
能源动力 | 5篇 |
轻工业 | 59篇 |
水利工程 | 18篇 |
石油天然气 | 1篇 |
无线电 | 43篇 |
一般工业技术 | 83篇 |
冶金工业 | 1093篇 |
原子能技术 | 2篇 |
自动化技术 | 85篇 |
出版年
2023年 | 3篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 20篇 |
2012年 | 12篇 |
2011年 | 21篇 |
2010年 | 19篇 |
2009年 | 19篇 |
2008年 | 23篇 |
2007年 | 31篇 |
2006年 | 31篇 |
2005年 | 16篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 7篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 27篇 |
1998年 | 282篇 |
1997年 | 175篇 |
1996年 | 130篇 |
1995年 | 69篇 |
1994年 | 57篇 |
1993年 | 74篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 23篇 |
1989年 | 13篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 25篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 50篇 |
1976年 | 91篇 |
1975年 | 11篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1961年 | 2篇 |
1930年 | 2篇 |
1927年 | 2篇 |
排序方式: 共有1529条查询结果,搜索用时 15 毫秒
1.
Presented here are details of the development of a novel membrane integrated circuit (IC) probe card structure based on microsystems technology. The device design allows probing of both solder bumps and pads. A self-limiting sensor was integrated to prolong device lifetime. Comparison with and discussion of the use of modelling is made. Possible enhancements to the probing structure are discussed to improve alignment and measurements. Also shown is data using our microsystems probe card to access a simple IC device. Our device has a contact resistance of less than 0.5 Ω for a force of 0.004 N. A method to implement our probing structure for commercial application and the potential developments which can be made to improve its ease of use are then discussed. 相似文献
2.
3.
The indications and results of single and double lung transplantation are described on the basis of 66 operations performed by the authors and on the background of the world literature. Lung transplantation is considered a new and promising therapeutic mode for treating patients with end-stage pulmonary failure related to fibrosis, emphysema, infective conditions, and pulmonary hypertension yielding satisfactory early results. The long-term prognosis of patients undergoing lung transplantation, like that of any other organ transfer, remains guarded. 相似文献
4.
DNA of plasmid pBR322 irradiated with laser at a wavelength of 193 mm was treated with an extract containing proteins from E.coli K12 AB1157 (wild-type). The enzymes were found to produce single- and double-strand DNA breaks, which was interpreted as a transformation of a portion of cyclobutane pyrimidine dimers and (6-4) photoproducts into nonrepairable single-strand DNA breaks. The products resulted from ionization of DNA, in particular, single-strand breaks, transform to double-strand breaks. A comparison of these data with the data on survival of plasmid upon transformation of E.coli K12 AB1157 enables one to assess the biological significance of single- and double-strand breaks. The inactivation of the plasmid (in AB1157) is mainly determined by the number of directly formed laser-induced single-strand breaks, whereas the contribution of enzymatically produced single- and double-strand breaks is insignificant. 相似文献
5.
6.
Scanning electron microscopy was used to study the effect of cyclophosphamide (Cy) on molar development in 18 Sprague-Dawley rats from 15 to 48 days of age after birth. Doses of 30 mg/kg body weight of Cy dissolved in 1 ml 0.9% NaCl were given to the rats at 10 and 13 days of age. Eighteen control rats had injections of 1 ml 0.9% NaCl at the same ages. The most obvious changes in the experimental teeth were found in the developing roots of the first and second molars and in both the crown and roots of the third molar. The roots of the first and second molars were short and showed apical closure in the experimental rats. In addition to the disturbances in crown and root formation, the third molars were also significantly reduced in total size as compared with the third molars in the control rats. 相似文献
7.
An extensive study of road traffic accident cases occurring within eastern suburban Calcutta during April 1992 to March 1993 was done. Of which 276 fatal cases having minimum medical aids were taken into consideration to avoid erroneous interpretation. Male pedestrians of age group of 50 years and above were mostly involved during the time period of 5 A.M. to 12 Noon. Fatal Accidents mostly occurred during winter and on the broader roads (Highways) and in majority of cases victims were at fault. 相似文献
8.
JH Winstanley SJ Leinster TG Cooke BR Westley AM Platt-Higgins PS Rudland 《Canadian Metallurgical Quarterly》1993,67(4):767-772
The expression of the protease cathepsin-D has been evaluated using an immunohistochemical technique with a polyclonal antibody in paraffin-embedded tissue from 359 patients treated between the years 1975-1981 for Stage I and II breast cancer. One hundred and twenty seven patients (35%) have strongly positive, granular staining, 138 (38%) are intermediately stained in the cytoplasm, and in 94 (26%) no staining is observed. There is a strong positive association between expression of cathepsin-D and the presence of tumour in axillary lymph nodes (P < 0.006). Expression of the protease is associated with significantly poorer survival of patients in univariate analysis (P = 0.025); however, this is not independent of other tumour variables. 相似文献
9.
F Buntinx HJ Schouten JA Knottnerus HF Crebolder GG Essed 《Canadian Metallurgical Quarterly》1993,46(4):367-370
The present study was carried out to investigate the biochemical and morphological changes in the liver after ligation of the hepatic artery (HA) in the presence and in the absence of extrahepatic cholestasis (EHC). The study was conducted on 100 rats divided into four groups of 25 animals each: group 1, sham operation; group 2, hepatic artery ligation (HAL); group 3, bile duct ligation (BDL); and group 4, HAL plus BDL. All animals were sacrificed 7 days after surgery when total bilirubin and fractions, alkaline phosphatase (AP), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured in serum and on the inner hepatocyte mitochondrial membrane (IHMM); the incidence of necrosis and the volume fractions of vessels, bile ducts and hepatocytes in the liver were also determined. HAL reduces the relative volumes of bile ducts, with no changes in levels of bilirubin and fractions, AP, ALT, AST and IHMM, but HAL associated with EHC reduces duct proliferation and the liver becomes more vulnerable to necrosis. In conclusion, the normal liver depends on HA flow and this dependence is more evident in the presence of EHC. 相似文献
10.
The Mus terricolor complex displays a stable homozygous arrangement of autosomal heterochromatin variations in the form of accretion of definitive autosomal short arms among three nonoverlapping populations, in concert with an expeditious evolutionary differentiation into three chromosomal species: M. terricolor I, II, and III. In contrast to the highly conservative M. musculus-like chromosomes in the coexisting sibling species, M. booduga, reshuffling and differentiation of centric heterochromatin has occurred in harmony with a revision of centric configurations, resulting in acrocentric and submetacentric autosomes. The chromosomal distribution of the prevalent vertebrate telomeric sequence (TTAGGG)n was examined by fluorescence in situ hybridization to metaphase cells of M. terricolor I, II, and III. An unusual centric organization of internal telomeric sequences was detected in all the submetacentric and acrocentric autosomes. An auxiliary role of these presumably fragile, recombinogenic telomeric sequences in the evolutionary revision of centric configurations in the terricolor complex is hypothesized. 相似文献