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81.
D. C. Dunand J. L. Sommer A. Mortensen 《Metallurgical and Materials Transactions A》1993,24(10):2161-2170
Preforms of nickel powder or nickel/alumina powder blends were infiltrated with molten aluminum to produce nickel aluminides.
Application of a pressure of 3.6 and 6.9 MPa on the melt allowed infiltration of preforms with nickel powder particles between
5 and 15 μm in diameter, which could not be infiltrated under the sole action of capillary forces. By varying the initial
preform temperature from 705 °C to 280 °C, the diameter of nickel powder particles from 15 to 150 μm, and the volume fraction
of alumina from 0 to 34 vol pct, pressure-infiltrated samples with large variations in the extent of reaction between nickel
and aluminum were pro- duced. The range of microstructure extended from fully reacted nickel aluminide to essentially unreacted
nickel/aluminum samples containing low levels of final porosity. In particular, it was found that reducing the initial preform
temperature below the melting point of aluminum results in a reduction of the rate and extent of aluminide formation, allowing,
in turn, reduction of macrosegregation within the resulting infiltrated material.
Formerly Research Assistant, Department of Materials Science and
Formerly Research Assistant, Department of Materials Science and 相似文献
82.
We performed 25 fresh cadaver dissections to describe the anatomy of the superficial and deep circumflex iliac artery and the superficial inferior epigastric artery to determine how they could least to used as donor vessels for the free transfer of groin flaps and living iliac bone. With injection of ink the capillary region of these vessels was stained in (iliac crest) bone, the internal oblique muscle and skin of the groin and thigh. The superficial and deep circumflex iliac artery were shown to be the main supply vessels of the groin and thigh and could be found in 96%-100% of cases. The venous drainage of this region followed from a superficial system (superficial circumflex iliac veins) and a deep venous system (Vv. comitantes accompanying arterial branches). Both venous systems could always be found. The superficial circumflex iliac artery was shown to only supply the skin and was the main donor vessel to the skin and soft tissue transplants. The deep circumflex iliac artery supplied the pelvic bone, the internal oblique muscle and a small constant area of skin above the iliac crest. Bone, muscle and bone, muscle and skin transplants could be obtained with this donor vessel, with enlargement of the skin area possible by combining two arterial branches combined in one transplant. With an average vessel diameter of 1.5 mm (superficial circumflex iliac artery) and 3 mm (deep circumflex iliac artery) both vessels could be used satisfactorily for microvascular transplantation. Different tissues including muscle, bone and skin could be obtained in adequate amounts to replace composite defects in the upper aerodigestive tract. 相似文献
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Discusses what it means to be a department chairperson, based on the author's 6.5 yrs of experience in this position. The frustrations and compensations of the job are considered. It is noted that administrative concerns come to replace concerns about the direction of the department. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
86.
A. H. Sommer 《JOM Journal of the Minerals, Metals and Materials Society》1959,11(9):623-627
A pioneer of basic construction in the open-hearth furnace sketches its history from wartime Germany to the present, with emphasis on US developments. The reasons why the future of basic construction has not been completely established are outlined. 相似文献
87.
Bodo?RosenhahnEmail author Gerald?Sommer 《Journal of Mathematical Imaging and Vision》2005,22(1):27-48
2D-3D pose estimation means to estimate the relative position and orientation of a 3D object with respect to a reference camera system. This work has its main focus on the theoretical foundations of the 2D-3D pose estimation problem: We discuss the involved mathematical spaces and their interaction within higher order entities. To cope with the pose problem (how to compare 2D projective image features with 3D Euclidean object features), the principle we propose is to reconstruct image features (e.g. points or lines) to one dimensional higher entities (e.g. 3D projection rays or 3D reconstructed planes) and express constraints in the 3D space. It turns out that the stratification hierarchy [11] introduced by Faugeras is involved in the scenario. But since the stratification hierarchy is based on pure point concepts a new algebraic embedding is required when dealing with higher order entities. The conformal geometric algebra (CGA) [24] is well suited to solve this problem, since it subsumes the involved mathematical spaces. Operators are defined to switch entities between the algebras of the conformal space and its Euclidean and projective subspaces. This leads to another interpretation of the stratification hierarchy, which is not restricted to be based solely on point concepts. This work summarizes the theoretical foundations needed to deal with the pose problem. Therefore it contains mainly basics of Euclidean, projective and conformal geometry. Since especially conformal geometry is not well known in computer science, we recapitulate the mathematical concepts in some detail. We believe that this geometric model is useful also for many other computer vision tasks and has been ignored so far. Applications of these foundations are presented in Part II [36].Bodo Rosenhahn gained his diploma degree in Computer Science in 1999. Since then he has been pursuing his Ph.D. at the Cognitive Systems Group, Institute of Computer Science, Christian-Albrechts University Kiel, Germany. He is working on geometric applications of Clifford algebras in computer vision.Prof. Dr. Gerald Sommer received a diploma degree in physics from the Friedrich-Schiller-Universität Jena, Germany, in 1969, a Ph.D. degree in physics from the same university in 1975, and a habilitation degree in engineering from the Technical University Ilmenau, Germany, in 1988. Since 1993 he is leading the research group Cognitive Systems at the Christian-Albrechts-Universität Kiel, Germany. Currently he is also the scientific coordinator of the VISATEC project. 相似文献
88.
Epitope tagging is a powerful method for the rapid analysis of protein function. In Saccharomyces cerevisiae epitope tags are introduced easily into chromosomal loci by homologous recombination using a simple PCR-based strategy. Although quite a number of tools exist for C-terminal tagging as well as N-terminal tagging of proteins expressed by heterologous promoters, there are only very limited possibilities to tag proteins at the N-terminus and retain the endogenous expression level. Furthermore, no PCR-templates for internal tagging have been reported. Here we describe new modules that are suitable for both the repeated N-terminal and internal tagging of proteins, leaving their endogenous promoters intact. The tags include 6xHA, 9xMyc, yEGFP, TEV-GST-6xHIS, ProtA, TEV-ProtA and TEV-ProtA-7xHIS in conjunction with different heterologous selection markers. 相似文献
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The techniques of digital image analysis and enhancement have been applied to TEM micrographs. Digitized micrographs of irradiated A1 and Mo containing cavities were enhanced by applying digital unsharp masking and thresholding techniques. These techniques produce enhanced images that allow for more effective analysis of image features using conventional analysis methods as well as computer methods. For the Mo data, a template-matching algorithm was applied to thresholded data and a computer-generated void histogram was obtained. The computer analysis gives results that are in agreement with conventional analysis of the same data. It is concluded that computer methods for cavity/void analysis can be successfully developed. 相似文献