全文获取类型
收费全文 | 7041篇 |
免费 | 439篇 |
国内免费 | 305篇 |
专业分类
化学 | 486篇 |
晶体学 | 20篇 |
力学 | 1948篇 |
综合类 | 27篇 |
数学 | 423篇 |
物理学 | 1504篇 |
综合类 | 3377篇 |
出版年
2024年 | 9篇 |
2023年 | 55篇 |
2022年 | 93篇 |
2021年 | 101篇 |
2020年 | 113篇 |
2019年 | 101篇 |
2018年 | 107篇 |
2017年 | 169篇 |
2016年 | 180篇 |
2015年 | 201篇 |
2014年 | 284篇 |
2013年 | 296篇 |
2012年 | 296篇 |
2011年 | 329篇 |
2010年 | 288篇 |
2009年 | 313篇 |
2008年 | 362篇 |
2007年 | 430篇 |
2006年 | 411篇 |
2005年 | 364篇 |
2004年 | 415篇 |
2003年 | 352篇 |
2002年 | 304篇 |
2001年 | 285篇 |
2000年 | 239篇 |
1999年 | 203篇 |
1998年 | 179篇 |
1997年 | 161篇 |
1996年 | 186篇 |
1995年 | 124篇 |
1994年 | 153篇 |
1993年 | 128篇 |
1992年 | 110篇 |
1991年 | 112篇 |
1990年 | 75篇 |
1989年 | 74篇 |
1988年 | 63篇 |
1987年 | 37篇 |
1986年 | 24篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1973年 | 1篇 |
1971年 | 5篇 |
1957年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有7785条查询结果,搜索用时 15 毫秒
951.
根据桥检报告,确定桥梁桥墩裂缝的位置及性质,采用ANSYS有限元方法对桥墩进行受力分析,探讨其裂缝产生的原因,并提出加固方案。 相似文献
952.
Flow and fracture of rocks under general triaxial compression 总被引:1,自引:0,他引:1
Recent laboratory studies of the flow and fracture of rocks under general triaxial compression are reviewed. New developments in laboratory techniques have made it possible to measure three principal stresses and strains under general triaxial stress states, in which all three principal stresses are different.Strength and ductility of isotropic rocks are markedly affected not only by the least compression 3, but also by the intermediate compression 2, although these two effects are rather additional in strength, but opposite in ductility. The experimental results show that dilatancy is highly anisotropic under the general triaxial stress states.Deformational properties of anisotropic rocks have been also measured under the general triaxial compression. In this case, the effect of the intermediate compression markedly depends on the orientations of the weak planes. 相似文献
953.
Nonlinear bending of circular sandwich plates 总被引:2,自引:0,他引:2
刘人怀 《应用数学和力学(英文版)》1981,2(2):189-208
In this paper, fundamental equations and boundary conditions of nonlinear axisymmetrical bending theory for the circular sandwich plates with a soft core are derived by means of the method of calculus of variations. Especially in the case of very thin faces, the preceding fundamental epuations and boundary conditions simplity considerably. For example, a circular sandwich plate with edge clamped but free to siip under the action of uniform lateral load is considered. A more accurate solution of this problem has been obtained by means of the modified iteration method.Notation
r, ,z
system of cylindrical coordinates
-
a
radius of plate boundary
-
t
thickness of the face
-
h
thickness of the core
-
h
0
distance from middle of thickness of lower face to middle of thickness of upper face
-
E
Young's modulus of the face
-
Poisson's ratio of the face
-
G
2
shear modulus of the core
-
D
f
flexural rigidity of the face
-
D
flexural rigidity of the plate
-
C
shear rigidity of the plate
-
q
uniform lateral load
-
u
i
,v
i
,w
i(i=1, 2, 3)
radial, tangential and normal displacement of upper face, core and lower face, respectively
-
u
radial displacement of the middle plane of the plate
-
w
deflection of the middle plane of the plate
-
rotation of connecting line of corresponding points in middle planes of two faces
-
1i
,
i
,
zi
,
ri
,
zi
,
rzi (i=1,2,3)
strains at a point of upper face, core and lower face
-
ri
,
i
,
zi
,
ri
,
zi
,
rzi(i=1,2,3)
stresses at a point of upper face, core and lower face
-
r
,
0
radial and tangential stress of the middle plane of the plate, respectively
-
U
i(i
=1, 2, 3)
strain energy of upper face, core and lower face, respectively
-
V
work done by the external force
-
U
total potential energy of the plate
-
M
r
radial moment of the plate
-
Q
r
shearing force of the plate
-
m
radial moment of the face
-
stress function
-
dimensionless radial coordinate
-
k
dimensionless characteristic parameter
-
W
dimensionless deflection
-
W
0
dimensionless center deflection
-
S
r
,S
0
dimensionless radial and tangential stress, respectively
-
S
r
(0),S
0 (0)
dimensionless radial and tangential stress at center, respectively
-
S
0(1)
dimensionless tangential stress at edge
-
P
dimensionless uniform lateral load
-
A
2,A
3,B
2,B
3,a
1,.....,a
2,
1,
2,l
1,1,...l
1 1,3,m
1,...,m
33,n
0,2,...n
22,6,R
1,,...R
33
auxiliary quantity
-
L
differential operator 相似文献
954.
牛庠均 《应用数学和力学(英文版)》1983,4(3):449-462
This paper discusses the fundamental assumptions,the differen-tial equations,and the variational principles of discontinuousform belonging to a new developing branch of science-the solidmechanics of discrete form.The solid mechanics of discrete formbelongs to the branch of science of discrete medium mechanicswhich is the developing direction of the mechanics for the pre-sent.Based on the solid system with discretization and sepa-rability,the unknown functions with discontinuity in definedregions and the defined regions with variable boundaries,themechanics systems to solve the solid displacements,strains andstresses in various cases are called the solid mechanics of dis-crete form.when the unknown functions are sufficiently smooth func-tions in the whole defined region and the effects of the vari-able boundaries are disregarded,the solid mechanics of discreteform will degenerate into the classical solid mechanics belong-ing to continuum.mechanics:Its variational principles will de-generate into the clas 相似文献
955.
江福汝 《应用数学和力学(英文版)》1982,3(5):683-695
In this paper we consider the nonlinear and unsymmetrical bendings of annular and circular thin plates under various supports. The uniformly valid asymptotic solutions have been derived by means of the perturbation method presented in [7]. 相似文献
956.
内部压力作用下矩形板中源于椭圆孔的分支裂纹应力强度因子的一种数值分析 总被引:1,自引:0,他引:1
应用一种边界元方法来研究内部压力作用下矩形板中源于椭圆孔的分支裂纹。该边界元方法由Crouch与Starfied建立的常位移不连续单元和笔者最近提出的裂尖位移不连续单元构成。在该边界元方法的实施过程中,左、右裂尖位移不连续单元分别置于裂纹的左、右裂尖处,而常位移不连续单元则分布于除了裂尖位移不连续单元占据的位置之外的整个裂纹面及其它边界。本数值结果进一步证实这种数值方法对计算有限大板中复杂裂纹的应力强度因子的有效性,同时该数值结果可以揭示裂纹体几何对应力强度因子的影响。 相似文献
957.
958.
959.
The spectra of transmission and reflection are measured in the region of 0.4–2.5 μm on thin silver selenium indate films obtained
by means of pulse laser vaporization. The magnitudes of the refractive index and absorption coefficient are calculated. The
energies of interband transitions and the values of crystalline and spin-orbit splitting are determined. The experimental
results for the AgInSe2 films agree with the data for bulk crystals.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 512–514, July–August, 2000. 相似文献
960.
大体积混凝土温度场计算与测试分析 总被引:9,自引:1,他引:8
建立了大体积混凝土温度场的数学模型,在一维散热情况下,用差分方法给出了数值解。在天津奥林匹克工地进行了现场测试,分析了理论与实际测试的区别,并提出了在施工中控制裂缝所采取的措施。 相似文献