全文获取类型
收费全文 | 1008篇 |
免费 | 9篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 26篇 |
金属工艺 | 4篇 |
机械仪表 | 11篇 |
建筑科学 | 5篇 |
能源动力 | 1篇 |
轻工业 | 10篇 |
水利工程 | 1篇 |
无线电 | 53篇 |
一般工业技术 | 54篇 |
冶金工业 | 828篇 |
原子能技术 | 3篇 |
自动化技术 | 20篇 |
出版年
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 5篇 |
2011年 | 8篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 15篇 |
2007年 | 11篇 |
2006年 | 11篇 |
2005年 | 12篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 31篇 |
1998年 | 265篇 |
1997年 | 134篇 |
1996年 | 89篇 |
1995年 | 58篇 |
1994年 | 60篇 |
1993年 | 55篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 10篇 |
1978年 | 1篇 |
1977年 | 24篇 |
1976年 | 61篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1966年 | 1篇 |
1960年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有1017条查询结果,搜索用时 15 毫秒
51.
52.
EH Nielsen 《Canadian Metallurgical Quarterly》1976,173(2):179-191
Unilateral electrolytic lesions of the locus coeruleus in rats result in spontaneous ipsiversive rotation, which is then replaced by contraversive rotation. One week after lesioning, when spontaneous turning ceases, apomorphine and d-amphetamine elicit contraversive circling behaviour, which was not affected by noradrenergic receptor blockade but was abolished by dopamine receptor blockade. The drug-induced contraversive circling response was also reproduced by piribedil but not clonidine. Combined unilateral electrolytic locus coeruleus and substantia nigra lesions on the same side resulted in apomorphine- and d-amphetamine-induced ipsilateral rotational behaviour which was indistinguishable from that seen with substantia nigra lesions alone. In rats with unilateral locus coeruleus lesions, the dose of intrastriatally injected apomorphine required to produce circling was less on the lesioned than the non-lesioned side. Direct injection of noradrenaline into one substantia nigra caused contraversive circling. Direct injection of phenoxybenzamine into one substantia nigra followed by apomorphine caused ipsiversive circling. The results suggest that the circling behaviour seen after unilateral locus coeruleus lesions depends on an asymmetry of striatal dopamine receptor activity and are consistent with a proposed coeruleus-nigral noradrenergic pathway, which enhances impulse flow in the dopaminergic nigrostriatal system. 相似文献
53.
Mammalian cells have been classified as proficient (Mer(+)) or deficient (Mer(-)) in methyl excision repair in terms of their cytotoxic reactions to agents that form O(6)-alkylguanine and their abilities to reactivate alkylated adenoviruses. O(6)-Methylguanine (O(6)MeGua) is considered to be a lethal, mutagenic, and carcinogenic lesion. We measured the abilities of cell extracts to transfer the methyl group from an exogenous DNA containing O(6)MeGua to acceptor protein. The constitutive level of acceptor activity was independent of the Mer phenotype and was approximately 100,000 acceptor sites per cell. Treatment of cells with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) results in a dose-dependent decrease in the acceptor activity in extracts because the rapid reaction between endogenous O(6)MeGua and acceptor protein makes the latter unavailable for further reaction. Treatment of cells with 1 muM MNNG for 15 min or 2 muM for approximately 2 min uses up >95% of the constitutive activity. However, Mer(+) cells, which are resistant to MNNG, rapidly resynthesize new acceptor protein, and the activity returns to the basal level in approximately 90 min. In Mer(-) tumor cells and Chinese hamster cells, which are sensitive to MNNG, resynthesis is not detectable in 90 min. Mer(-) simian virus 40-transformed fibroblasts, known to have an intermediate sensitivity to MNNG, have an intermediate resynthesis rate. Treatment of cells with multiple low doses of MNNG results in the enhanced production of O(6)MeGua-accepting protein in levels 2.5-fold above the constitutive values for Mer(+) tumor cells and to approximately 1.5-fold for Mer(+) fibroblasts or Mer(-) simian virus 40-transformed cells. Such treatments reduce the activities in Mer(-) tumor cells and Chinese hamster cells. We conclude: (i) estimates of O(6)MeGua in cellular DNA shortly after treatment may be seriously in error because of the rapid repair of this lesion, and (ii) the adaptive resynthesis of acceptor protein, not its constitutive level, is the important correlate of cell resistance to methylating agents. 相似文献
54.
55.
56.
The effects of off-focusing and beam deflection on polarimetric stress measurements of optical fibers are investigated. A simple method for reducing the distortion of the phase retardation caused by unwanted beam deflections in residual stress measurement is introduced. The method is examined numerically by ray-tracing techniques and experimentally by use of hollow silica fibers into which various index-matching liquids have been inserted. An autofocusing technique is introduced. The error in stress measurement reproducibility was determined to be less than 4%. We tested the absolute error in measured stress by applying incremental external tension and determined that it is less than 0.464 MPa. 相似文献
57.
58.
J. W. Paek B. H. Kang S. Y. Kim J. M. Hyun 《International Journal of Thermophysics》2000,21(2):453-464
An experimental measurement program was performed to determine thermophysical properties of aluminum-based foam metals. The effective thermal conductivity k
e and permeability K were investigated in detail. Experimental facilities were fabricated, and the measurement procedures and methodologies were evaluated. One-dimensional heat conduction was considered to determine k
e . The results indicate that k
e increases as the porosity decreases. However, no noticeable changes in k
e were detected from variations of the cell size of the foam metal at a fixed porosity . The permeability K is substantially affected by both and the cell size. An empirical correlation for the friction factor f is proposed based on the concepts of K and inertial effect. 相似文献
59.
In a recent study, we discovered that many single load/store operations in embedded applications can be parallelized and thus encoded simultaneously in a single‐instruction multiple‐data instruction, called the multiple load/store (MLS) instruction. In this work, we investigate the problem of utilizing MLS instructions to produce optimized machine code, and propose an effective approach to the problem. Specifically, we formalize the MLS problem, that is, the problem of maximizing the use of MLS instructions with an unlimited register file size. Based on this analysis, we show that we can solve the problem efficiently by translating it into a variant of the problem finding a maximum weighted path cover in a dynamic weighted graph. To handle a more realistic case of the finite size of the register file, our solution is then extended to take into account the constraints of register sequencing in MLS instructions and the limited register resource available in the target processor. We demonstrate the effectiveness of our approach experimentally by using a set of benchmark programs. In summary, our approach can reduce the number of loads/stores by 13.3% on average, compared with the code generated from existing compilers. The total code size reduction is 3.6%. This code size reduction comes at almost no cost because the overall increase in compilation time as a result of our technique remains quite minimal. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
60.