全文获取类型
收费全文 | 5227篇 |
免费 | 236篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 96篇 |
综合类 | 22篇 |
化学工业 | 1121篇 |
金属工艺 | 101篇 |
机械仪表 | 71篇 |
建筑科学 | 197篇 |
矿业工程 | 8篇 |
能源动力 | 174篇 |
轻工业 | 281篇 |
水利工程 | 38篇 |
石油天然气 | 17篇 |
无线电 | 567篇 |
一般工业技术 | 1027篇 |
冶金工业 | 842篇 |
原子能技术 | 50篇 |
自动化技术 | 865篇 |
出版年
2023年 | 74篇 |
2022年 | 147篇 |
2021年 | 186篇 |
2020年 | 129篇 |
2019年 | 124篇 |
2018年 | 131篇 |
2017年 | 146篇 |
2016年 | 162篇 |
2015年 | 120篇 |
2014年 | 192篇 |
2013年 | 265篇 |
2012年 | 287篇 |
2011年 | 297篇 |
2010年 | 194篇 |
2009年 | 206篇 |
2008年 | 236篇 |
2007年 | 177篇 |
2006年 | 164篇 |
2005年 | 105篇 |
2004年 | 108篇 |
2003年 | 97篇 |
2002年 | 109篇 |
2001年 | 80篇 |
2000年 | 77篇 |
1999年 | 95篇 |
1998年 | 241篇 |
1997年 | 170篇 |
1996年 | 134篇 |
1995年 | 79篇 |
1994年 | 87篇 |
1993年 | 65篇 |
1992年 | 51篇 |
1991年 | 45篇 |
1990年 | 47篇 |
1989年 | 32篇 |
1988年 | 54篇 |
1987年 | 38篇 |
1986年 | 25篇 |
1985年 | 35篇 |
1984年 | 28篇 |
1983年 | 27篇 |
1982年 | 27篇 |
1981年 | 26篇 |
1980年 | 24篇 |
1979年 | 19篇 |
1978年 | 29篇 |
1977年 | 38篇 |
1976年 | 56篇 |
1975年 | 28篇 |
1972年 | 22篇 |
排序方式: 共有5477条查询结果,搜索用时 15 毫秒
1.
2.
3.
Embedded computing moved beyond toasters quite some time ago, but there are still misconceptions about what embedded computers do. Some of those misconceptions come from an old-fashioned view of what a computer is. 相似文献
4.
S Modi DE Gilham MJ Sutcliffe LY Lian WU Primrose CR Wolf GC Roberts 《Canadian Metallurgical Quarterly》1997,36(15):4461-4470
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin that produces Parkinsonism symptoms in man, has been examined as a substrate of recombinant human cytochrome P450 2D6. When cumene hydroperoxide is used as an oxygen and electron donor, a single product is formed, identified as 4-phenyl-1,2,3,6-tetrahydropyridine. The K(m) for formation of this product (130 microM) is in agreement with the dissociation constants for MPTP binding to the enzyme determined by optical and nuclear magnetic resonance (NMR) spectroscopy. When the reaction is carried out with nicotinamide adenine dinucleotide phosphate (reduced) (NADPH) and recombinant human NADPH-cytochrome P450 reductase, a second product, identified as 1-methyl-4-(4'-hydroxyphenyl)-1,2,3,6-tetrahydropyridine, is formed in addition to 4-phenyl-1,2,3,6-tetrahydropyridine. The K(m) values for formation of these two products are 19 microM and 120 microM, respectively. Paramagnetic relaxation experiments have been used to measure distances between the protons of bound MPTP and the heme iron, and these have been used to construct models for the position and orientation of MPTP in the active site. For the cytochrome alone, a single mode of binding was observed, with the N-methyl close to the heme iron in a position appropriate for the observed N-demethylation reaction. In the presence of the reductase, the data were not consistent with a single mode of binding but could be explained by the existence of two alternative orientations of MPTP in the active site. One of these, characterized by a dissociation constant of 150 microM, is essentially identical to that observed in the absence of the reductase. In the second, which has a K(d) of 25 microM, the MPTP is oriented so that the aromatic ring is close to the heme iron, in a position appropriate for p-hydroxylation leading to the formation of the product seen only in the presence of the reductase. In the case of codeine, another substrate for cytochrome P450 2D6, the addition of reductase had no effect on the nature of the product formed, the dissociation constant, or the orientation in the binding site. These observations show that NADPH-cytochrome P450 reductase has an allosteric effect on the active site of cytochrome P450 2D6 that affects the binding of some substrates but not others. 相似文献
5.
This paper traces the development of engineering technology from bifurcation to the present time. They assert that ET desires to be distinguished more than it seeks to be distinct. This analysis of the successes and failures of bifurcation lead to a differentiation between engineering technology's being distinct as a discipline and becoming distinguished in its own right. They offer some conjecture about the bright future of ET as a partner with science and engineering in an atmosphere of increased technological development but intense international competition. 相似文献
6.
Yu Yang Hugo Bender Kai Arstila Bart Swinnen Bert Verlinden Ingrid De Wolf 《Microelectronics Reliability》2008,48(8-9):1517-1520
Focused ion beam (FIB) and nano-probing were applied for failure analysis of three-dimensional stacked circuits with copper through-silicon-vias between the stacked chips. The failure analysis was done after high temperature storage and thermal cycling tests. Passive voltage contrast in FIB allowed to pinpoint the open sites. FIB cross-sections showed the presence of opens at the bottom of the copper vias. The failure cause was suspected to be an interlayer particle, which was confirmed by optical profilometry. Nano-probing was used on another sample to pinpoint the failure location through the measurement of the local resistance within the daisy chains. The failure was traced out to be related with surface contamination. 相似文献
7.
The Karlsruhe Tritium Neutrino experiment (KATRIN) is going to use a very large electro-static tandem spectrometer to measure the electron spectrum from the tritium beta decay, where several kilometers of non-evaporable getter (NEG) strips (type ST707) are to be used to achieve the UHV requirements. Different geometrical configurations of the NEG strips have been studied by Monte Carlo simulations. It is shown that the resulting pumping speed of the getter pumps will allow to get a pressure below 10−11 mbar in the huge vessel with a volume of 1400 m3. By systematic assessment of the statistics of the pumping surfaces, it could be demonstrated that the design is sound. 相似文献
8.
PATIENT: A 14-year-old boy suffered from an acute bilateral blindness which occurred in 24-h time, accompanied by headache and raised temperature, with inconspicuous optic nerve head and fundus. After diagnosis of empyema with magnet resonance tomography (MRT) the sphenoid sinus was fenestrated and streptococcus pneumoniae isolated. Liquor and serology being inconspicuous, there was no evidence of leucaemic or autoimmune disease, intoxication or intracranial tumor. CLINICAL COURSE: The condition of the patient improved under systemic antibiotic therapy. The bilateral amaurosis remained and opticus atrophy developed. CONCLUSION: A bilateral amaurosis with descending opticus atrophy as a consequence of a sphenoiditis and spreading inflammation to the meninges and the optic nerve in the area of the chiasm is a rare event. The imaging technique of the MRT offers new opportunities for an early and more pointed diagnosis and therapy. 相似文献
9.
10.
M WünschB.A Wolf 《Polymer》2002,43(18):5027-5034
Vapor pressures, phase equilibria and interfacial tensions σ were measured for solutions of poly(dimethylsiloxane) (PDMS, Mw[equals]75 kg/mol and Mn[equals]50 kg/mol) in mixed solvents of toluene (TL) and ethanol (EtOH) at 30, 40, 50 and 60 °C. The experimental ternary phase diagrams can be modeled quantitatively from the determined concentration and temperature dependent binary interaction parameters χij if the experimentally inaccessible composition dependence of χEtOH/PDMS is adjusted. The relations between σ and the equation of state of the system differ from that applying to single solvents. The exponents as well as the amplitude prefactors of the corresponding scaling laws (e.g. the dependencies of σ on the length of the tie lines or on the hump energy, i.e. on the intrusion into the two phase regime quantified in terms of Gibbs energies) change considerably with temperature. However, this variation can be reduced significantly by normalizing the independent variables. Dividing the length of the tie lines by the length for the corresponding binary subsystem proves more efficient than the distance of these tie lines from the critical point of the ternary system relative to the maximum distance of the binary subsystem. A combined normalization does not improve the situation. 相似文献