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211.
212.
ZhengJunjie PengHong NieChongjun 《Acta Mechanica Solida Sinica》2004,17(4):353-360
Based on the results of conventional triaxial compression tests for a soil, a trilinear elasto-plastic model is proposed to simulate the stress-strain softening curve. According to this curve, the constitutive relation between the bulk strain and two pr… 相似文献
213.
Kyu Hyun Jung Gun Nam Manfred Wilhellm Kyung Hyun Ahn Seung Jong Lee 《Rheologica Acta》2006,45(3):239-249
Rheological properties of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer
solution in both linear and nonlinear regions have been investigated. PEO-PPO-PEO triblock copolymer solution shows a dramatic
change in mechanical properties as temperature changes. PEO-PPO-PEO triblock copolymer undergoes a transition from sol to
gel with increase of temperature. During this transition the copolymer solution passes through three different stages, namely
sol, soft gel, and hard gel. In our previous research (Hyun et al. in J Non-Newtonian Fluid Mech 55:51–65, 2002), large amplitude oscillatory shear (LAOS) behavior was found to be very sensitive to the generated microstructures. In this
study, we investigated the relationship between the LAOS type and the microdomain structure. Newtonian behavior is observed
in sol region, while there appear two kinds of LAOS types in the soft gel region. One is type I (G′, G′′ decreasing) and the other is a combination of type I and type IV (G′, G′′ increasing followed by decreasing). Type III (G′ decreasing, G′′ increasing followed by decreasing) is observed in the hard gel region. We compared the shape of stress curves, Lissajous
pattern, and Fourier transform (FT) rheology of hard gel and soft gel under LAOS, and tried to relate the complex LAOS behavior
with the microstructural change. From these investigations, it was found that the LAOS behavior and the stress pattern at
large strain are closely related to the microdomain structure of PEO-PPO-PEO triblock copolymer, and provide a lot of useful
information on the microstructures induced by large deformation. 相似文献
214.
An apparatus for the measurement of liquid complex shear viscosity in the frequency range 80–2500 Hz, with the use of a torsion pendulum operating in forced oscillation, is described. The drive and detection system consists of a magnet inside the pendulum, two excitation and two measuring coils. The determination of the complex shear viscosity is based on the measurement of the resonance frequency and the damping of the torsion pendulum.The feasibility of this method is demonstrated with a number of Newtonian liquids in the viscosity range 0.3 to 60 m Pa s. Results for a viscoelastic polymer solution are presented. A comparison is made with other apparatus working in the same frequency range.
a
coil height
-
A
apparatus constant
-
B
magnetic induction
-
C
1,C
2
apparatus constants
-
d
diameter torsion rod
-
D
pendulum damping
-
E
apparatus constant
-
F
0
top frequency
-
G
shear modulus torsion rod
-
G
* =G + iG
complex shear modulus
-
h
length torsion rod
-
H
transfer function
-
i
-
I
moment of inertia
-
J
0
excitation-current amplitude
-
J
exc
excitation current
-
K
torsion spring constant
-
l
length pendulum mass
-
M
torque
-
n
number of coil turns
-
p
dipole moment
-
Q =
0/
mechanical quality
-
r
radius pendulum mass
-
R
Re {Z}
-
t
time
-
T
temperature
-
U
induction voltage
-
U
0
induction-voltage amplitude
-
x
distance
-
X
Im {Z}
-
Z = R + iX
liquid impedance
-
Z
cyl
characteristic cylindrical impedance
-
Z
pl
characteristic plane impedance
-
angle
-
M
coefficient of linear expansion of the pendulum mass
-
R
coefficient of linear expansion of the torsion rod
-
rate of shear
-
penetration depth
-
steady-state viscosity
-
s
solvent viscosity
-
angular displacement
-
0
angular-displacement amplitude
-
µ
0
=4 10–7 Vs/Am
-
density
-
phase angle
-
angular frequency
-
0
top angular frequency
-
band-width 相似文献
215.
G-actin prepared from pork liver and purified to give a product of 95–98% purity was polymerized to F-actin in a rotational dynamic viscometer. The rheological properties were investigated during the course of polymerisation and after polymerisation.
G andG measured at frequencies around 0.1 Hz increased strongly during the first 3 hours of the reaction and then slowly approached a constant value in the range of 10–50 mPa. The rise during polymerisation was more than two orders of magnitude. When a solution of F-actin was subjected to steady shear at a high shear rate for a short period of time and subsequently dynamic measurements were performed, then a considerably smallerG (about 70% smaller) was observed immediately after cessation of the steady shear.G then increased with time and approached its initial value.When measuring the viscosity of F-actin solutions as a function of shear rate, a strong shear thinning effect was seen which did not vanish even at shear rates as low as 0.001 s–1. Even at this low shear rates, a pronounced yield maximum was observed before reaching the steady state. Oscillatory experiments showed a remarkably weak frequency dependence ofG.
The results imply that F-actin solutions are largely structured forming a weak temporary network which can be easily destroyed by application of high shear rates. It seems most likely that the destruction occurs by a reversible, shear induced depolymerisation process. 相似文献
216.
Suppose the principal stretches are all different at a point P in a deformed body. In this case, it has been shown [1] that generally there is an infinity of non coplanar infinitesimal
material line elements at P which remain unsheared following the deformation – that is, the angle between the arms of each pair of material line elements
forming the triad remains unchanged. Here it is shown that in this case when all three principal stretches at P are different, there is no set of four infinitesimal material line elements, no three of which are coplanar, and such that
the angle between each pair of the six pairs of material line elements is unchanged following the deformation. It is only
when all three principal stretches at P are equal to each other, that there are unsheared tetrads at P, and in that case all tetrads are unsheared.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
217.
Summary The paper presents a thermodynamically consistent constitutive model for elasto-plastic analysis of orthotropic materials at large strain. The elastic and plastic anisotropies are assumed to be persistent in the material but the anisotropy axes can undergo a rigid rotation due to large plastic deformations. The orthotropic yield function is formulated in terms of the generally nonsymmetric Mandel stress tensor such that its skew-symmetric part is additionally taken into account. Special attention is focused on the convexity of the yield surface resulting in the nine-dimensional stress space. Of particular interest are new convexity conditions which do not appear in the classical theory of anisotropic plasticity. They impose additional constraints on the material constants governing the plastic spin. The role of the plastic spin is further studied in simple shear accompanied by large elastic and large plastic deformations. If the plastic spin is neglected, the shear stress response is characterized by oscillations with an amplitude strictly dependent on the degree of the plastic anisotropy.accepted for publication 2 March 2004 相似文献
218.
219.
220.
C. -H. Chien Y. -C. Chen C. -C. Hsieh Y. -T. Chiou Y. -D. Wu T. -P. Chen 《Experimental Mechanics》2004,44(2):214-220
With the increasing application of flip-chip technology in the microelectronics industry, the adhesion strength of interfaces
in flip-chip microelectronic structures has become an important issue for manufacturing and operation. In this paper we present
an experimental investigation of the adhesive strength of underfill material to solder mask coated FR-4 substrate under thermal
cycling. The effects of the number of thermal cycles on interfacial strength were investigated by using the button shear test.
The relationship between interfacial strength and the thickness of solder mask was also examined. Furthermore, the morphologies
of fracture surfaces of the test specimens were analyzed by scanning electron microscopy. The results of this study show that
the interfacial strength of the underfill/solder mask/substrate joint was significantly reduced by thermal fatigue. Finally,
the degradation behavior and possible mechanisms were then determined on the basis of these observations. 相似文献