全文获取类型
收费全文 | 260057篇 |
免费 | 3191篇 |
国内免费 | 823篇 |
专业分类
电工技术 | 5130篇 |
综合类 | 330篇 |
化学工业 | 37219篇 |
金属工艺 | 10252篇 |
机械仪表 | 8486篇 |
建筑科学 | 6102篇 |
矿业工程 | 1076篇 |
能源动力 | 6389篇 |
轻工业 | 22851篇 |
水利工程 | 2561篇 |
石油天然气 | 3908篇 |
武器工业 | 68篇 |
无线电 | 34720篇 |
一般工业技术 | 50061篇 |
冶金工业 | 46528篇 |
原子能技术 | 5418篇 |
自动化技术 | 22972篇 |
出版年
2021年 | 2037篇 |
2019年 | 2032篇 |
2018年 | 3468篇 |
2017年 | 3533篇 |
2016年 | 3728篇 |
2015年 | 2319篇 |
2014年 | 4047篇 |
2013年 | 11283篇 |
2012年 | 6562篇 |
2011年 | 8874篇 |
2010年 | 6981篇 |
2009年 | 7848篇 |
2008年 | 8676篇 |
2007年 | 8614篇 |
2006年 | 7802篇 |
2005年 | 7139篇 |
2004年 | 6885篇 |
2003年 | 6731篇 |
2002年 | 6370篇 |
2001年 | 6469篇 |
2000年 | 6169篇 |
1999年 | 6252篇 |
1998年 | 14240篇 |
1997年 | 10268篇 |
1996年 | 8110篇 |
1995年 | 6411篇 |
1994年 | 5710篇 |
1993年 | 5581篇 |
1992年 | 4551篇 |
1991年 | 4211篇 |
1990年 | 4048篇 |
1989年 | 3779篇 |
1988年 | 3624篇 |
1987年 | 3170篇 |
1986年 | 3065篇 |
1985年 | 3610篇 |
1984年 | 3382篇 |
1983年 | 3031篇 |
1982年 | 2850篇 |
1981年 | 2951篇 |
1980年 | 2760篇 |
1979年 | 2648篇 |
1978年 | 2499篇 |
1977年 | 2945篇 |
1976年 | 3554篇 |
1975年 | 2316篇 |
1974年 | 2312篇 |
1973年 | 2318篇 |
1972年 | 1849篇 |
1971年 | 1745篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
71.
72.
The effect of high oxide field stress is studied using capacitance-time (C-t) measurements of MOS capacitors. The stress results in parallel shifts of the C-t curve along the time axis. The flatband voltage shift ΔVFB obtained from the initial deep depletion capacitance C(t=0+) follows the same trend as that from the high-frequency C-V characteristics. However, the discrepancy between the two flatband voltages becomes larger as the stress increases due to the effect of interface charges on C-t characteristics. The flatband voltage difference is converted to interface trap density, showing a steady increase of interface trap density with stress, similar to that from low-frequency C-V measurements 相似文献
73.
74.
A new method based on a two-wire line has been developed for noncontact diagnostics of a low-temperature plasma and its fluxes
in channels with complex profiles. This method provides good spatial and time resolution.
Pis’ma Zh. Tekh. Fiz. 23, 1–7 (July 26, 1997) 相似文献
75.
BACKGROUND: Home parenteral nutrition (HPN) is used to treat intestinal failure. A minority of HPN patients are dependent on opiates and benzodiazepines to control pain and anxiety. The aim of this study was to determine what effects such drug dependence had on patient outcomes. METHODS: Ten dependent patients were prospectively compared with 10 well-matched, nondependent HPN patients for the same 12-month period. Episodes of line sepsis and other complications were documented and the cost of treatment estimated. Health status was measured using the SF36 and EuroQol instruments. RESULTS: The dependent group had significantly more episodes of central line sepsis (p = .0007) as well as other complications (p = .0002). This led to significantly longer periods of inpatient care (p = .0004) and therefore higher costs of treatment. Health status was lower in the dependent group; they reported more pain (p = .04) and less energy (p = .04). CONCLUSIONS: The complication rate and increased cost of treatment for opiate- and sedative-dependent patients receiving HPN significantly detract from the overall outcome of this therapy. 相似文献
76.
77.
78.
79.
ME Sutherlin I Nishimori T Caffrey EP Bennett H Hassan U Mandel D Mack T Iwamura H Clausen MA Hollingsworth 《Canadian Metallurgical Quarterly》1997,57(21):4744-4748
The levels of mRNA expression of three UDP-N-acetyl-alpha-D-galactosamine:polypeptide GalNAc N-acetylgalactosaminyltransferases (GalNAc-transferases) were quantified for human adenocarcinoma cell lines from pancreas, colon, stomach, and breast. Two of the GalNAc-transferases, GalNAc-T1 and GalNAc-T2, were expressed constitutively and at low levels in most or all cell lines examined. A third GalNAc-transferase, GalNAc-T3, was differentially expressed. Well-differentiated adenocarcinoma cell lines expressed high levels and moderately differentiated cell lines expressed lower levels of GalNAc-T3. Cell lines classified as poorly differentiated failed to express GalNAc-T3 mRNA at levels that could be detected by Northern blot analysis. Differential expression of the GalNAc-T3 protein was confirmed in these cell lines by Western blotting. We propose that glycosylation in tumor cell lines may be regulated in part by differential expression of GalNAc-transferases, and we suggest that GalNAc-T3 gene expression may be a molecular indicator of differentiated adenocarcinoma. 相似文献
80.