全文获取类型
收费全文 | 2464篇 |
免费 | 38篇 |
专业分类
电工技术 | 9篇 |
综合类 | 4篇 |
化学工业 | 149篇 |
金属工艺 | 19篇 |
机械仪表 | 14篇 |
建筑科学 | 43篇 |
矿业工程 | 2篇 |
能源动力 | 28篇 |
轻工业 | 125篇 |
水利工程 | 15篇 |
石油天然气 | 33篇 |
无线电 | 102篇 |
一般工业技术 | 176篇 |
冶金工业 | 1627篇 |
原子能技术 | 13篇 |
自动化技术 | 143篇 |
出版年
2022年 | 8篇 |
2019年 | 12篇 |
2018年 | 15篇 |
2017年 | 13篇 |
2016年 | 14篇 |
2015年 | 15篇 |
2014年 | 26篇 |
2013年 | 66篇 |
2012年 | 17篇 |
2011年 | 27篇 |
2010年 | 38篇 |
2009年 | 31篇 |
2008年 | 45篇 |
2007年 | 34篇 |
2006年 | 56篇 |
2005年 | 26篇 |
2004年 | 33篇 |
2003年 | 36篇 |
2002年 | 35篇 |
2001年 | 27篇 |
2000年 | 20篇 |
1999年 | 77篇 |
1998年 | 475篇 |
1997年 | 267篇 |
1996年 | 170篇 |
1995年 | 108篇 |
1994年 | 96篇 |
1993年 | 92篇 |
1992年 | 33篇 |
1991年 | 39篇 |
1990年 | 36篇 |
1989年 | 37篇 |
1988年 | 36篇 |
1987年 | 24篇 |
1986年 | 32篇 |
1985年 | 32篇 |
1984年 | 8篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1978年 | 14篇 |
1977年 | 52篇 |
1976年 | 97篇 |
1975年 | 15篇 |
1973年 | 9篇 |
1972年 | 9篇 |
1970年 | 7篇 |
1969年 | 7篇 |
排序方式: 共有2502条查询结果,搜索用时 15 毫秒
21.
22.
G Arepally C Reynolds A Tomaski J Amiral A Jawad M Poncz DB Cines 《Canadian Metallurgical Quarterly》1995,104(6):648-654
The diagnosis of heparin-induced thrombocytopenia (HIT) may be affirmed by demonstrating heparin-dependent anti-platelet antibodies using the 14C-serotonin release assay (SRA). In this study, results of the SRA was compared with the recently described platelet factor 4 (PF4)/heparin enzyme-linked immunosorbent assay (ELISA). Compared with the SRA, the sensitivity and specificity of a PF4/heparin ELISA was 87% and 92%, respectively, using an assay developed in our laboratory; and 90% and 98%, respectively, using a commercially developed kit (Diagnostica Stago, Asnieres, France). However, antibodies to PF4/heparin were also detected in up to 8% of patients whose plasma was negative by SRA, and 23% of patients receiving heparin who were not thrombocytopenic. These data indicate that results obtained with the PF4/heparin ELISA and the SRA are generally in accord in patients with a clinical diagnosis of HIT. However, discrepant results occur in approximately 20% of cases because of the greater sensitivity of ELISA and the possible involvement of other heparin-binding proteins. The fact that each assay contributes independent information in some cases must be considered in the sequence of test performance and in providing consultation to the practicing hematologist. 相似文献
23.
24.
Giboney K.S. Nagarajan R.L. Reynolds T.E. Allen S.T. Mirin R.P. Rodwell M.J.W. Bowers J.E. 《Photonics Technology Letters, IEEE》1995,7(4):412-414
Results of the first fabrication and measurement of travelling-wave photodetectors are reported. The devices have bandwidths as high as 172 GHz, the highest reported for a p-i-n photodetector, and bandwidth-efficiency products as large as 76 GHz, the largest reported for any photodetector without gain. Comparisons with vertically illuminated and waveguide photodetectors fabricated on the same wafer establish the superior performance of travelling-wave photodetectors. Microwave loss on the travelling-wave photodetector structure is identified as a bandwidth limitation 相似文献
25.
26.
27.
28.
We consider the problem of turbo multiuser detection for synchronous and asynchronous code-division multiple-access (CDMA) in the presence of unknown users. Turbo multiuser detectors, as previously developed, typically require knowledge of the signature waveforms of all of the users in the system and ignore users whose signature sequences are unknown, e.g., users outside the cell. We develop turbo multiuser detection for CDMA uplink systems and other environments in which the receiver has knowledge of the signature waveforms of only K˘⩽ K users. Subspace techniques are used to estimate the interference from the unknown-users and the interference estimate is subtracted from the received signal. We see that the new receiver significantly outperforms the conventional turbo multiuser receiver for moderate and high signal-to-noise ratios. It is also seen that the traditional turbo receiver provides little gain through iteration when unknown users are present 相似文献
29.
T Reynolds 《Canadian Metallurgical Quarterly》1993,85(17):1366-1368
30.
The effects of not breastfeeding on mortality due to diarrhea and acute lower respiratory infection (ALRI) in children under 2 years of age were examined using data from a 1988-1991 longitudinal study of 9,942 children in Metro Cebu, The Philippines. Cox regression methods were used to study the magnitude of the risks, possible interactions with birth weight and nutritional status, and the effect of additional confounding factors. Not breastfeeding had a greater effect on diarrheal mortality than on ALRI mortality. In the first 6 months of life, failing to initiate breastfeeding or ceasing to breastfeed resulted in an 8- to 10-fold increase in the rate of diarrheal mortality. The rate of mortality associated with both ALRI and diarrhea was increased nearly six times by not breastfeeding, but the rate of ALRI mortality alone was not increased. The data also suggested that the risk of mortality associated with not breastfeeding was greater for low birth weight infants and infants whose mothers had little formal education. After age 6 months, the protective effects of breastfeeding dropped dramatically. These findings underscore the importance of promoting breastfeeding, especially during the first 6 months of life, and of targeting high risk groups such as low birth weight babies and those of low socioeconomic status. 相似文献