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31.
32.
针对建立抗滑群桩的设计方法问题,分析了抗滑群桩在水平推力作用下的力学行为.以重庆江东边坡的典型断面为例,应用有限元程序CORE3D分析了群桩的桩间颗粒土的土拱区域,结合桩的荷载位移曲线、土拱效应解释了土体应力传递到抗滑桩的规律,通过对影响土拱效应的参数,如桩间距、土体厚度、抗滑桩嵌入深度和桩径等的深入研究,提出了相应的群桩布置参数估算公式.研究成果在重庆江东边坡的防护工程设计中得到了应用,并取得了较好的效果. 相似文献
33.
Multiple functional and hard-to-quantify sensorial product attributes that can be satisfied by a large number of cosmetic ingredients are required in the design of cosmetics. To overcome this problem, a new optimization-based approach for expediting cosmetic formulation is presented. It exploits the use of a hierarchy of models in an iterative manner to refine the search for creating the highest-quality cosmetic product. First, a systematic procedure is proposed for optimization problem formulation, where the cosmetic formulation problem is defined, design variables are specified, and a set of models for sensorial perception and desired product properties are identified. Then, a solution strategy that involves iterative model adoption and two numerical techniques (i.e., generalized disjunctive programming reformulation and model substitution) is applied to improve the efficiency of solving the optimization problem and to find better solutions. The applicability of the proposed procedure and solution strategy is illustrated with a perfume formulation example. 相似文献
34.
In this paper, we propose a new compact fourth-order accurate method for solving the two-dimensional fourth-order elliptic boundary value problem with third-order nonlinear derivative terms. We use only 9-point single computational cell in the scheme. The proposed method is then employed to solve Navier–Stokes equations of motion in terms of streamfunction–velocity formulation, and the lid-driven square cavity problem. We describe the derivation of the method in details and also discuss how our streamfunction–velocity formulation is able to handle boundary conditions in terms of normal derivatives. Numerical results show that the proposed method enables us to obtain oscillation-free high accuracy solution. 相似文献
35.
36.
Flexible-body modeling with geometric nonlinearities remains a hot topic of research by applications in multibody system dynamics
undergoing large overall motions. However, the geometric nonlinear effects on the impact dynamics of flexible multibody systems
have attracted significantly less attention. In this paper, a point-surface impact problem between a rigid ball and a pivoted
flexible beam is investigated. The Hertzian contact law is used to describe the impact process, and the dynamic equations
are formulated in the floating frame of reference using the assumed mode method. The two important geometric nonlinear effects
of the flexible beam are taken into account, i.e., the longitudinal foreshortening effect due to the transverse deformation,
and the stress stiffness effect due to the axial force. The simulation results show that good consistency can be obtained
with the nonlinear finite element program ABAQUS/Explicit if proper geometric nonlinearities are included in the floating
frame formulation. Specifically, only the foreshortening effect should be considered in a pure transverse impact for efficiency,
while the stress stiffness effect should be further considered in an oblique case with much more computational effort. It
also implies that the geometric nonlinear effects should be considered properly in the impact dynamic analysis of more general
flexible multibody systems. 相似文献
37.
We present a novel approach for extreme simplification of point set models, in the context of real-time rendering. Point sets
are often rendered using simple point primitives, such as oriented discs. However, this requires using many primitives to
render even moderately simple shapes. Often, one wishes to render a simplified model using only a few primitives, thus trading
accuracy for simplicity. For this goal, we propose a more complex primitive, called a splat, that is able to approximate larger and more complex surface areas than oriented discs. We construct our primitive by decomposing
the model into quasi-flat regions, using an efficient algebraic multigrid algorithm. Next, we encode these regions into splats
implemented as planar support polygons textured with color and transparency information and render the splats using a special
blending algorithm. Our approach combines the advantages of mesh-less point-based techniques with traditional polygon-based
techniques. We demonstrate our method on various models. 相似文献
38.
Marco Franchini 《Water Resources Management》1994,8(3):225-238
With reference to the kinematic wave theory coupled with the hypothesis of constant linear velocity for the rating curve, rising limb analytical solutions have been calculated for overland flow, over an Hortonian-infiltrating surface, and sediment discharge. These analytical solutions are certainly easier to use than the numerical integration of the basic equations and they may be used to obtain an initial evaluation of the parameters of more complex models generally devised for complicated cases.Notation
a
exponent of the Horton law [T–1]
-
b
exponent of the rill erosion equation
-
B
inter-rill erosion coefficient [ML–m–2T
m–1]
-
c
sediment concentration [ML–3]
-
c
o
reference sediment concentration [ML–3]
-
E
I
inter-rill erosion [ML–2T–1]
-
E
R
rill erosion [ML–2T–1]
-
f
c
final infiltration rate of the soil [LT–1]
-
f
o
initial infiltration rate of the soil [LT–1]
-
h
flow depth [L]
-
h
o
reference flow depth [L]
-
i
infiltration rate [LT–1]
-
k
rill erosion coefficient [ML–1–b
T–1]
-
K
integration constant
-
L()
Laplace transformation
-
m
exponent of the inter-rill erosion equation
-
n
Manning's coefficient [L–1/3T]
-
p
rainfall intensity [LT–1]
-
q
water discharge per unit width [L2T–1]
-
q
s
sediment discharge per unit width [ML–1T–1]
-
t
time [T]
-
t
p
ponding time [T]
-
x
distance along the flow direction [L]
Greek Letters
coefficient of the stage-discharge equation [L2–T–1]
-
exponent of the stage-discharge equation
-
rill erosion coefficient [L–1] 相似文献
39.
Exploring the power of shared memory communication objects and models, and the limits of distributed computability are among the most exciting research areas of distributed computing. In that spirit, this paper focuses on a problem that has received considerable interest since its introduction in 1987, namely the renaming problem. It was the first non-trivial problem known to be solvable in an asynchronous distributed system despite process failures. Many algorithms for renaming and variants of renaming have been proposed, and sophisticated lower bounds have been proved, that have been a source of new ideas of general interest to distributed computing. It has consequently acquired a paradigm status in distributed fault-tolerant computing.In the renaming problem, processes start with unique initial names taken from a large name space, then deciding new names such that no two processes decide the same new name and the new names are from a name space that is as small as possible.This paper presents an introduction to the renaming problem in shared memory systems, for non-expert readers. It describes both algorithms and lower bounds. Also, it discusses strong connections relating renaming and other important distributed problems such as set agreement and symmetry breaking. 相似文献
40.
The spectral properties of the incidence matrix of the communication graph are exploited to provide solutions to two multi-agent control problems. In particular, we consider the problem of state agreement with quantized communication and the problem of distance-based formation control. In both cases, stabilizing control laws are provided when the communication graph is a tree. It is shown how the relation between tree graphs and the null space of the corresponding incidence matrix encode fundamental properties for these two multi-agent control problems. 相似文献