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91.
RJ Rottier CN Hahn LW Mann M del Pilar Martin RJ Smeyne K Suzuki A d'Azzo 《Canadian Metallurgical Quarterly》1998,7(11):1787-1794
Protective protein/cathepsin A (PPCA) is a pleiotropic lysosomal enzyme that complexes with beta-galactosidase and neuraminidase, and possesses serine carboxypeptidase activity. Its deficiency in man results in the neurodegenerative lysosomal storage disorder galactosialidosis (GS). The mouse model of this disease resembles the human early onset phenotype and results in severe nephropathy and ataxia. To understand better the pathophysiology of the disease, we compared the occurrence of lysosomal PPCA mRNA and protein in normal adult mouse tissues with the incidence of lysosomal storage in PPCA(-/-) mice. PPCA expression was markedly variable among different tissues. Most sites that produced both mRNA and protein at high levels in normal mice showed extensive and overt storage in the knockout mice. However, this correlation was not consistent as some cells that normally expressed high levels of PPCA were unaffected in their storage capability in the PPCA(-/-) mice. In addition, some normally low expressing cells accumulated large amounts of undegraded products in the GS mouse. This apparent discrepancy may reflect a requirement for the catalytic rather than the protective function of PPCA and/or the presence of cell-specific substrates in certain cell types. A detailed map showing the cellular distribution of PPCA in nomal mouse tissues as well as the sites of lysosomal storage in deficient mice is critical for accurate assessment of the effects of therapeutic interventions. 相似文献
92.
CT Lai VA Tanay GA Rauw AN Bateson IL Martin GB Baker 《Canadian Metallurgical Quarterly》1997,704(1-2):175-179
Reported here is a rapid, sensitive and relatively inexpensive procedure using gas chromatography with nitrogen-phosphorus detection (GC-NPD) to quantify buspirone levels in brains of rats. The analyte was directly extracted from brain homogenate with toluene after basification and then subjected to GC-NPD analysis using a capillary column. The calibration curves were linear over the range of 10 to 320 ng per 2 ml of brain homogenate, with typical r2 values >0.99. The assay was highly reproducible and gave peaks with excellent chromatographic properties. 相似文献
93.
MJ Telford JW Martin BJ Rock LL Turik JE Hairfield 《Canadian Metallurgical Quarterly》1994,19(3):25-9, 33
Small local chapter groups can present quality cost effective regional seminars. Key components are dedication of members, teamwork, and a sense of direction. The following guidelines and information can provide a framework for planning and coordinating a seminar. 相似文献
94.
Martin Gneiser Julia Heidemann Mathias Klier Andrea Landherr Florian Probst 《Information Systems and E-Business Management》2012,10(1):61-84
Online social networks have been gaining increasing economic importance in light of the rising number of their users. Numerous
recent acquisitions priced at enormous amounts have illustrated this development and revealed the need for adequate business
valuation models. The value of an online social network is largely determined by the value of its users, the relationships
between these users, and the resulting network effects. Therefore, the interconnectedness of a user within the network has
to be considered explicitly to get a reasonable estimate for its economic value. Established standard business valuation models,
however, do not account for these aspects sufficiently. Thus, we propose an economic model for the valuation of online social
networks, which takes into account the users’ interconnectedness within the network. Furthermore, we analyze different centrality
measures, which can be used to quantify users’ interconnectedness in online social networks and propose a measure which is
based on the PageRank-algorithm. Finally, the practical application of the model is illustrated by an example of the European
online social network XING.com. 相似文献
95.
Obermaier H Mohring J Deines E Hering-Bertram M Hagen H 《IEEE transactions on visualization and computer graphics》2012,18(2):270-282
Crease surfaces describe extremal structures of 3D scalar fields. We present a new region-growing-based approach to the meshless extraction of adaptive nonmanifold valley and ridge surfaces that overcomes limitations of previous approaches by decoupling point seeding and triangulation of the surface. Our method is capable of extracting valley surface skeletons as connected minimum structures. As our algorithm is inherently mesh-free and curvature adaptive, it is suitable for surface construction in fields with an arbitrary neighborhood structure. As an application for insightful visualization with valley surfaces, we choose a low frequency acoustics simulation. We use our valley surface construction approach to visualize the resulting complex-valued scalar pressure field for arbitrary frequencies to identify regions of sound cancellation. This provides an expressive visualization of the topology of wave node and antinode structures in simulated acoustics. 相似文献
96.
Successful planning and control of robots strongly depends on the quality of kinematic models, which define mappings between
configuration space (e.g. joint angles) and task space (e.g. Cartesian coordinates of the end effector). Often these models
are predefined, in which case, for example, unforeseen bodily changes may result in unpredictable behavior. We are interested
in a learning approach that can adapt to such changes—be they due to motor or sensory failures, or also due to the flexible
extension of the robot body by, for example, the usage of tools. We focus on learning locally linear forward velocity kinematics
models by means of the neuro-evolution approach XCSF. The algorithm learns self-supervised, executing movements autonomously
by means of goal-babbling. It preserves actuator redundancies, which can be exploited during movement execution to fulfill
current task constraints. For detailed evaluation purposes, we study the performance of XCSF when learning to control an anthropomorphic
seven degrees of freedom arm in simulation. We show that XCSF can learn large forward velocity kinematic mappings autonomously
and rather independently of the task space representation provided. The resulting mapping is highly suitable to resolve redundancies
on the fly during inverse, goal-directed control. 相似文献
97.
Numerical modeling of multiphase flows in microfluidics and micro process engineering: a review of methods and applications 总被引:2,自引:1,他引:1
Martin Wörner 《Microfluidics and nanofluidics》2012,12(6):841-886
This article presents a comprehensive review of numerical methods and models for interface resolving simulations of multiphase
flows in microfluidics and micro process engineering. The focus of the paper is on continuum methods where it covers the three
common approaches in the sharp interface limit, namely the volume-of-fluid method with interface reconstruction, the level
set method and the front tracking method, as well as methods with finite interface thickness such as color-function based
methods and the phase-field method. Variants of the mesoscopic lattice Boltzmann method for two-fluid flows are also discussed,
as well as various hybrid approaches. The mathematical foundation of each method is given and its specific advantages and
limitations are highlighted. For continuum methods, the coupling of the interface evolution equation with the single-field
Navier–Stokes equations and related issues are discussed. Methods and models for surface tension forces, contact lines, heat
and mass transfer and phase change are presented. In the second part of this article applications of the methods in microfluidics
and micro process engineering are reviewed, including flow hydrodynamics (separated and segmented flow, bubble and drop formation,
breakup and coalescence), heat and mass transfer (with and without chemical reactions), mixing and dispersion, Marangoni flows
and surfactants, and boiling. 相似文献
98.
Here we investigate the problem of transforming a nonlinear system on the torusT
n
by using global feedback and global changes of coordinates into an invariant system (i.e., a control system
of whichf andg
i
are (left and right) invariant vector fields whenT
2 is considered as a Lie group). We provide a complete answer whenn=2 and give a sufficient condition and necessary conditions in the more general case. 相似文献
99.
It has been suggested by Kayser that finite-size effects associated with capillary waves might play a significant role in some surface tension measurements; for capillary rise between plates a distance D apart, an effect varying as 1/D and apparently observable in measurements, was proposed. In reconsidering this problem, one must analyze the thermodynamics of finite-size corrections to surface tension. In particular, one sees that capillary rise between plates does not measure the interfacial free energy density but, rather, a derivative of the interfacial free energy with respect to a system dimension. The quantity needed to draw definite conclusions, the finite-size residual free energy, can be calculated within the harmonic or Gaussian capillary wave model in d spatial dimensions with the aid of Poisson summation techniques and should yield the correct leading asymptotic behavior. For d=3 and experimentally relevant parameter values, the results are independent of the short-wavelength cutoff needed in the model and can be checked against the theory of conformai covariance at two-dimensional critical points. It is found that the finite-size effects in capillary-rise measurements of surface tension vary as 1/D
2 (with a universal coefficient) but are too small to be seen in current experiments.Invited paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
100.
A full profile X-ray powder diffraction structure refinement has been carried out on a sample of synthesized CuGaTe2 using graphite monocromatized CuK step-scan data and a profile shape of the Pearson VII type. The most satisfactory convergence was achieved at R
p = 0.0666, R
wp = 0.0884, R
B = 0.0106 and R
F = 0.0102. The derived structural parameters at 26.5°C are: a = 0.602348(7), c = 1.193979(2) nm and x(Te) = 0.256(6). The ratio between lattice parameters, = c/2a = 0.9911 (0), differs from 1.0, indicating a tetragonal distortion, and non-ideal anion displacements, x(Te)1/4, is manifested by the existence of bond alternation of Cu-Te and Ga-Te with interatomic distances of 0.262(5) and 0.2578(5) nm, respectively. These results show a light tetrahedral deformation produced by four-fold tetrahedra of the copper cation in the CuGaTe2 chalcopyrite-type structure. 相似文献