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51.
One of the major effects of heavy doping in semiconductors is that the dielectric constant κ changes with impurity density and thus with position. The change is significant for impurity densities N greater than 1017 cm?3. The low temperature classical relation of Castellan and Seitz is modified by including the contribution to the local field at the atomic site by the polarization of the host atoms due to an electric field. This correction makes an appreciable difference in κ(N). A new model for the polarizability of the impurity atoms is also developed. It is found that there is good agreement between the values of the dielectric constant of Si doped with As, P and Sb predicted by this theory and those found experimentally by Bethin et al. The critical impurity concentration for the metal-nonmetal transition found from this theory is however higher than that given by Castner et al. Reasons for this discrepancy are given. 相似文献
52.
S. Velicu T. S. Lee C. H. Grein P. Boieriu Y. P. Chen N. K. Dhar J. Dinan D. Lianos 《Journal of Electronic Materials》2005,34(6):820-831
The cost and performance of hybrid HgCdTe infrared (IR) focal plane arrays are constrained by the necessity of fabricating
the detector arrays on a CdZnTe substrate. These substrates are expensive, fragile, available only in small rectangular formats,
and are not a good thermal expansion match to the silicon readout integrated circuit. We discuss in this paper an IR sensor
technology based on monolithically integrated IR focal plane arrays that could replace the conventional hybrid focal plane
array technology. We have investigated the critical issues related to the growth of HgCdTe on Si read-out integrated circuits
and the fabrication of monolithic focal plane arrays: (1) the design of Si read-out integrated circuits and focal plane array
layouts; (2) the low-temperature cleaning of Si(001) wafers; (3) the growth of CdTe and HgCdTe layers on read-out integrated
circuits; (4) diode creation, delineation, electrical, and interconnection; and (4) demonstration of high yield photovoltaic
operation without limitation from earlier preprocessing such as substrate cleaning, molecular beam epitaxy (MBE) growth, and
device fabrication. Crystallographic, optical, and electrical properties of the grown layers will be presented. Electrical
properties for diodes fabricated on misoriented Si and readout integrated circuit (ROIC) substrates will be discussed. The
fabrication of arrays with demonstrated I–V properties show that monolithic integration of HgCdTe-based IR focal plane arrays
on Si read-out integrated circuits is feasible and could be implemented in the third generation of IR systems. 相似文献
53.
54.
By alloying boron with RPd3 (R=rare earth) compounds, new ternary alloys of the formula RPd3B
x
(0 ≤x ≤ 1) have been prepared. The parent RPd3 compounds crystallise in the cubic AuCu3 type structure. The addition of boron does not change the structure but results in an expansion of the lattice. Therefore,
it is likely that the small boron atoms occupy the vacant body centred position in AuCu3 type structure. It is also observed that compounds of the composition RRh3B can be formed in the cubic structure for all rare earths R though the parent RRh3 compounds exist only for R=Ce (AuCu3 type) and La, Sm, Nd and Gd (all hexagonal CeNi3 type). This points out the role of boron in stabilising new crystallographic phases. The results of susceptibility measurements
on some of the RPd3B and RRh3B compounds are presented. In particular, it is noted that while GdPd3 orders antiferromagnetically withT
N=6 K, GdPd3B does not order magnetically down to 4.2 K. 相似文献
55.
The maintenance of large information systems involves continuous modifications in response to evolving business conditions or changing user requirements. Based on evidence from a case study, it is shown that the system maintenance activity would benefit greatly if the process knowledge reflecting the teleology of a design could be captured and used in order to reason about he consequences of changing conditions or requirements, A formalism called REMAP (representation and maintenance of process knowledge) that accumulates design process knowledge to manage systems evolution is described. To accomplish this, REMAP acquires and maintains dependencies among the design decisions made during a prototyping process, and is able to learn general domain-specific design rules on which such dependencies are based. This knowledge cannot only be applied to prototype refinement and systems maintenance, but can also support the reuse of existing design or software fragments to construct similar ones using analogical reasoning techniques 相似文献
56.
An appraisal of the use of mixed refrigerants is presented following an investigation on the performance of a window air conditioner. This system was chosen because the temperature changes are comparatively large. The important results of the study and proposals to reduce power consumption and achieve optimum performance are described. 相似文献
57.
58.
59.
We have defined special conditions for the preparation of an acetone powder of rat liver microsomes which is capable of converting
squalene to cholesterol in high yield. This preparation is also useful for the demonstration of cofactor requirements for
certain reactions in sterol biosynthesis. Buffer washed acetone powders are virtually completely dependent upon the 105,000
×g supernatant of rat liver (S105) for activity, yet S105 by itself is inert in sterol synthesis. The ability of S105 to stimulate sterol synthesis is heat liable, nondialyzable, trypsin sensitive, and has been partially purified by ammonium
sulfate precipitation and chromatography on Sephadex G-200. These results plus other experiments support the following hypothesis:
the 105,000 ×g supernatant of rat liver (S105) contains a noncatalytic carrier protein (Sterol Carrier Protein or SCP) which originates from the endoplasmic reticulum,
binds the substrate, and makes the substrate reactive to the sterol synthesizing enzymes present in the acetone powder of
liver microsomes. The participation of SCP may be an important general mechanism in the biological synthesis of cholesterol.
One of 12 papers to be published from the Sterol Symposium presented at the AOCS Meeting, New Orleans, April, 1970. 相似文献
60.