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81.
Allele frequency of D17S855 microsatellite locus, an intragenic polymorphic cytosine-adenine repeat located in the BRCA1 gene, was analyzed in 456 normal tissues of Japanese adults. The frequency of D17S855 microsatellite polymorphism was 77.9% (335/456). The size of D17S855 PCR fragments ranged from 137 to 157 bp. The most frequent allele was 151 bp (29.9%) followed by 149-bp (19.3%), 145-bp (17.5%), and 147-bp (17.0%) fragments. The observed allele distribution of this microsatellite was similar to that of Southern Swedes, while it was quite different from that of European Caucasian specimens deposited in the Genome Database.  相似文献   
82.
A secondary electron detection scheme for the distributed axis, fixed-aperture system is described. It employs a multi-channel detector array with a through-hole for a primary beamlet on each channel, a field terminator installed between the detector array and sample, and a deflector forming a static transverse electric field between the field terminator and sample. These elements enable detection of the secondary electrons stimulated by the primary beamlet. In order to achieve a high detection rate, small separation of the primary beamlets, and small aberrations, the size and the layout of the through-holes of the field terminator are studied. The equation of motion in an ideal field distribution is analytically solved and the dispersion of the secondary electrons caused by the helical motion in an axial magnetic field and chromatic variation of deflection are calculated. Aberrations are calculated by using numerical simulation. On the basis of these calculations, two types of the field terminator are proposed. One has a single through-hole, which is shared by a primary beamlet and the secondary electrons stimulated by the primary beamlet, per primary beamlet. The other has a through-hole exclusively for a primary beamlet and an extra slot for the secondary electrons, per primary beamlet. Simulations reveal that the former achieves a secondary electron detection rate of 99.7% and aberrations smaller than 4.6 nm, but doesn’t enable the separation of the primary beamlet to be smaller than 1000 μm. In contrast, the latter achieves a secondary electron detection rate of 95.0%, aberrations smaller than 9.7 nm. Furthermore, it also enables the separation of the primary beamlet to be as small as 250 μm, the same as in our detector array at this moment.  相似文献   
83.
For the original article see ibid., vol. 31, no. 2, p. 271-4 (1996). In the aforementioned paper the authors consider the advantages of laying out matched pairs of transistors, resistors, capacitors, etc., with interdigitated geometries and common centroid. Then they show six examples of “matched devices”. However, the commenters point out that not one has a common centroid. This leads to the conclusion that the computer program ALAS! seems to have a remarkable consistency in making layouts where the centroids are never in common. In reply, the authors thanks R.A. Pease for his comments on their paper and respond to his concerns, especially clarifying the issues regarding common-centroid versus interdigitated layout  相似文献   
84.
Modeling aerial images has recently become a crucial component of semiconductor manufacturing. As all steppers employ partially coherent illumination, such modeling has been computationally intensive for all but elementary patterns. In this paper we describe a fast computational method for calculating aerial images of integrated circuit masks produced by a partially coherent optical projection system. The method described relies on two tools to realize fast computation: (1) coherent decompositions of partially coherent imaging system models as proposed by Pati and Kailath (1994), and (2) the use of “basis” (or building block) images that are well-suited to describe integrated circuit patterns. Examples are presented in which aerial images are computed for large mask areas. The proposed method represents a speed improvement of several orders of magnitude over a more traditional, and more general, approach (SPLAT from the University of California, Berkeley)  相似文献   
85.
Pease  R. F. W. 《Spectrum, IEEE》1967,4(10):96-102
The scanning electron microscope combines the techniques of the cathode-ray tube and the conventional electron microscope?both considered indispensable to modern technology. The SEM, which presents a picture having a distinct three-dimensional appearance, is finding application in the examination of wood fibers in connection with paper manufacture, of surfaces undergoing ionic bombardment, and of corrosion. At the present time, one of the most pressing problems is to reduce its total cost.  相似文献   
86.
During development, progenitor cells follow timetables for differentiation that span many cell generations. These developmental timetables are robustly encoded by the embryo, yet scalably adjustable by evolution, facilitating variation in organism size and form. Epigenetic switches, involving rate-limiting activation steps at regulatory gene loci, control gene activation timing in diverse contexts, and could profoundly impact the dynamics of gene regulatory networks controlling developmental lineage specification. Here, we develop a mathematical framework to model regulatory networks with genes controlled by epigenetic switches. Using this framework, we show that such epigenetic switching networks uphold developmental timetables that robustly span many cell generations, and enable the generation of differentiated cells in precisely defined numbers and fractions. Changes to epigenetic switching networks can readily alter the timing of developmental events within a timetable, or alter the overall speed at which timetables unfold, enabling scalable control over differentiated population sizes. With their robust, yet flexibly adjustable nature, epigenetic switching networks could represent central targets on which evolution acts to manufacture diversity in organism size and form.  相似文献   
87.
The question of how mask dimensional errors impact yield is becoming increasingly critical to VLSI manufacturing. Both the magnitude and the spatial correlation of CD and registration errors are believed important to this issue. As part of a program to characterize these errors, we have had one identical test mask made on 6 different state-of-the-art mask pattern generators with widely different architectures. The test mask provides information on both registration and feature-size errors in both x- and y-directions, and does so over distances of several centimeters with spacing between measurements as small as 1 μm. More than 100000 data points have been collected from these test plates using a LMS2000 optical metrology system, and are analyzed in the spatial frequency domain where error contributors as small as 1 nm can be identified. All systems were found to have similar characteristics in that most error contributors occur at a number of machine-specific spatial frequencies correlated to the particular architecture and printing strategy of the machine. Comparison of raster to vector machines show that vector machines tend to have more periodic error contributors, especially in the high spatial frequency range, which is consistent with the more complex writing fields used to achieve higher throughput  相似文献   
88.
Activation of a T cell in response to peptide bound to class I MHC occurs by the sum of interactions across the area of contact between the TCR, the peptide, and class I MHC. It has been observed recently that substitution of the peptide residue at a position that is not accessible from the exterior of the class I molecule modulates T cell responses, raising the possibility that there may be indirect structural effects in the peptide-class I complex as a consequence of peptide binding. This report describes the use of mAbs to probe the conformation of the alpha 1 and alpha 2 domains of the mouse class I molecule Kb when bound to ovalbumin peptide and a panel of 19 peptide analogues that differ at position 2 (P2). By crystallographic data, side chains of this position are buried in the Ag binding cleft and have no direct access to the TCR. Substitution of position 2 results in a measurable change in conformation of the class I molecule, a change that correlates with the ability to stimulate T cells. This leads to a model that T cell activation by the peptide-class I complex may occur in three ways: 1) direct interaction of the TCR with the class I heavy chain, 2) direct interaction of the TCR with solvent-accessible peptide side chains, and 3) indirect interaction of peptide with TCR mediated via conformational perturbations in the class I complex.  相似文献   
89.
90.
We developed a technique using nonlinear correlation of photoluminescence (PL) to characterize midwave infrared lasers by extracting the density and temperature dependence of the carrier lifetime and its exact branching into radiative and nonradiative processes. This was accomplished, without time resolving the PL recovery, through mathematical optimization. We extracted this information by using a laser source that can be operated in both continuous-wave and short pulse modes. Through fitting of the PL signal and its nonlinear correlation for both laser modes of operation, the carrier lifetime as a function of density is extracted. As a proof of principle, we investigated a midinfrared Sb based laser and showed that the radiative branching ratio drops from approximately 54% at 80 K to about 3% at room temperature, resulting from an order of magnitude increase in the nonradiative rate coupled with a factor of 2 reduction in the radiative rate. We believe that this is a very generic approach and can be extended to various luminescing material systems.  相似文献   
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