全文获取类型
收费全文 | 6953篇 |
免费 | 257篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 99篇 |
综合类 | 8篇 |
化学工业 | 1864篇 |
金属工艺 | 130篇 |
机械仪表 | 157篇 |
建筑科学 | 355篇 |
矿业工程 | 16篇 |
能源动力 | 219篇 |
轻工业 | 499篇 |
水利工程 | 33篇 |
石油天然气 | 11篇 |
无线电 | 704篇 |
一般工业技术 | 1215篇 |
冶金工业 | 660篇 |
原子能技术 | 89篇 |
自动化技术 | 1162篇 |
出版年
2023年 | 36篇 |
2022年 | 90篇 |
2021年 | 147篇 |
2020年 | 81篇 |
2019年 | 96篇 |
2018年 | 121篇 |
2017年 | 135篇 |
2016年 | 191篇 |
2015年 | 138篇 |
2014年 | 174篇 |
2013年 | 346篇 |
2012年 | 320篇 |
2011年 | 400篇 |
2010年 | 322篇 |
2009年 | 314篇 |
2008年 | 319篇 |
2007年 | 308篇 |
2006年 | 325篇 |
2005年 | 232篇 |
2004年 | 249篇 |
2003年 | 190篇 |
2002年 | 188篇 |
2001年 | 150篇 |
2000年 | 135篇 |
1999年 | 119篇 |
1998年 | 197篇 |
1997年 | 169篇 |
1996年 | 134篇 |
1995年 | 125篇 |
1994年 | 121篇 |
1993年 | 104篇 |
1992年 | 77篇 |
1991年 | 61篇 |
1990年 | 66篇 |
1989年 | 58篇 |
1988年 | 56篇 |
1987年 | 59篇 |
1986年 | 32篇 |
1985年 | 92篇 |
1984年 | 67篇 |
1983年 | 65篇 |
1982年 | 58篇 |
1981年 | 91篇 |
1980年 | 59篇 |
1979年 | 61篇 |
1977年 | 47篇 |
1976年 | 52篇 |
1975年 | 55篇 |
1974年 | 46篇 |
1973年 | 33篇 |
排序方式: 共有7221条查询结果,搜索用时 15 毫秒
951.
952.
HF L?hr C Elste HP Dienes G Michel HB Braun KH Meyer zum Büschenfelde G Gerken 《Canadian Metallurgical Quarterly》1996,25(3):292-300
BACKGROUND/AIM: Virus-host interactions may have pathogenetic significance in chronic hepatitis. Thus the humoral immune response was evaluated during the clinical course of HCV-infected patients. METHODS: Eighteen selected chronic HCV patients received three doses of 3 or 6 MU interferon-alpha 2a weekly for 6 to 12 months and were followed up for 6 to 60 months. Anti-HCV antibody levels were serially measured either in end-point diluted sera with the Matrix-Assay or with quantitative anti-HC34-IgG and -IgM ELISA. Circulating immune complexes were assessed by flow cytometry and the results were correlated with histology, quantitative HCV-RNA levels and genotypes. RESULTS: Nine complete responders (CR; genotypes 1a n = 4; 1b n = 1; 2a n = 1; 3a n = 3) showing sustained virus elimination and ALT normalisation had low HCV-RNA pretreatment levels (mean 14 x 10(3) copies/ml) compared to six nonresponders and three partial responders (NR/PR; genotypes 1a n = 2; 1b n = 7) who had significantly higher HCV-RNA pretreatment levels (mean 254 x 10(3) copies/ml; p < 0.01). In untreated NR/PR the HC34 core-antigen was most immunogenic, in CR the NS3-derived HC29-antigen. Pre-treatment levels of anti-HC 34-IgG and -IgM antibody levels in NR/PR were higher than in CR (IgM/IgG p = 0.05, n.s.) and these differences became significant during or after therapy (3 months therapy: IgM p < 0.02/IgG p < 0.07; end of therapy: IgM 0.006/IgG p < 0.04; 6 months post-therapy: IgM p < 0.002/IgG p < 0.004). The PR patients showed recurrent anti-HC34 antibody levels that preceded disease reactivation and detectable HCV-RNA in serum. Immune complex formation increased in some patients during treatment but did not correlate with disease activity, quantitative viraemia, antibody levels or therapy outcome. CONCLUSION: Anti-HC34 antibodies, i.e. of the IgM-subtype, correlated quantitatively with viraemia and disease activity. Monitoring the antibody levels may predict the long-term therapy outcome during interferon-alpha treatment. 相似文献
953.
TP Duprez M Gille BC Vande Berg J Malghem CB Grandin P Michel S Ghariani BE Maldague 《Canadian Metallurgical Quarterly》1996,38(6):511-515
Low back pain is caused by a variety of etiologies. Some clinicians have postulated that much low back pain is due to trauma to the iliolumbar ligament. The iliolumbar ligament is one of the three pelvic-lumbar ligaments and develops during the 12th week of gestation. The iliolumbar ligament appears to be a major stabilizing component between the vertebral spine and the pelvis. The innervation of the iliolumbar ligament appears similar to the posterior lumbar ligaments. Our hypothesis is: micro-trauma to the iliolumbar ligament is the primary cause of many cases of chronic low back pain because (1) it is the weakest component of the multifidus triangle; (2) there is increased susceptibility to injury due to its angulated attachment; (3) it is a primary inhibitor of excess sacral flexion; (4) it is a highly innervated nociceptive tissue; and (5) it plays an increased role with progressive disc degeneration. 相似文献
954.
955.
956.
The prophylactic use of antibiotics for various surgical procedures was studied in six surgical departments of the Hadassah University Hospital over an 18-month period between January 1972 and June 1973. A total of 7,339 patients was discharged from the six departments during this period. Antibiotics had been used prophylactically in 17.7% of these patients and in 20.4% of the 6,313 patients in whom there was no evidence of infection on admission. The rate of prophylactic use varied from 12.8 to 47.8% in different departments. Different prophylactic regimes were used in the various departments, but there was a tendency for the same regime to be used within one department, irrespective of the nature of the surgical procedure. The antibiotics were usually started postoperatively. The duration of the prophylactic courses varied but there was a general tendency to continue for more than five days, often up to 10 or more days. The frequency of use seemed to be related to the presence of factors regarded as carrying a high risk of infection, such as advanced age, operation through a contaminated field and the presence of malignancy. The association between prophylactic use and subsequent wound infection was examined. The importance of continuous surveillance of the prophylactic use of antibiotics and the role of the infection-control unit in this surveillance is stressed. 相似文献
957.
Michel Borgne 《电信纪事》1983,38(9-10):411-423
The implementation of high capacity (140 Mbit/s) digital radio links leads to the use of high level modulation schemes in order to reduce spectrum occupation. A comparison between these modulations (with 16, 32, 64 and 128 levels) in the presence of impairments of a real channel is interesting to determine the spectral efficiency we can reach. The error probability is given by a method based upon a Gram-Charlier expansion using only the moments of the intersymbol interference random variable. 相似文献
958.
959.
The Sixty-Fifth Annual Meeting of the Southern Society for Philosophy and Psychology was held on April 19-21, 1973, at the Regency-Hyatt House in Knoxville, Tennessee. Approximately 200 members, friends, and guests were in attendance. The Program consisted of 41 papers in philosophy and 47 in psychology, in addition to 4 symposia in psychology, including 1 in honor of H. M. Johnson, and 3 joint sessions. As usual, a social hour and business session were included in the program. The Convention program is presented here in its entirety. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
960.
Michel Mandel 《大分子材料与工程》1984,123(1):63-83
Some physical properties of aqueous solutions containing linear, flexible, polyelectrolytes are reviewed in order to emphasize the role of charge interactions in these systems which strongly depend on the charge of the macromolecular chain and the concentration of low molar mass electrolyte in solution. Particular emphasis is put on polyelectrolyte solutions containing an excess of added salt, which from a theoretical point of view are easier to understand. Both the dilute and the semi-dilute case will be discussed. In the former the problem of the electrostatic potential around the macromolecular chain is briefly reviewed as well as the use of a wormlike chain model to derive average dimensions of polyelectrolytes in solutions. In the latter the scaling approach to concentration effects in polyelectrolyte solutions is briefly discussed. The pecularities of the semi-dilute regime in polyelectrolyte solutions is illustrated with the help of results obtained with dynamic light scattering and the time dependent decay of electric birefringence. 相似文献