全文获取类型
收费全文 | 709篇 |
免费 | 146篇 |
国内免费 | 84篇 |
专业分类
化学 | 44篇 |
晶体学 | 5篇 |
力学 | 243篇 |
综合类 | 8篇 |
数学 | 79篇 |
物理学 | 560篇 |
出版年
2024年 | 3篇 |
2023年 | 7篇 |
2022年 | 12篇 |
2021年 | 24篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 26篇 |
2014年 | 36篇 |
2013年 | 42篇 |
2012年 | 19篇 |
2011年 | 50篇 |
2010年 | 43篇 |
2009年 | 40篇 |
2008年 | 31篇 |
2007年 | 41篇 |
2006年 | 51篇 |
2005年 | 42篇 |
2004年 | 41篇 |
2003年 | 47篇 |
2002年 | 34篇 |
2001年 | 32篇 |
2000年 | 41篇 |
1999年 | 30篇 |
1998年 | 20篇 |
1997年 | 33篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有939条查询结果,搜索用时 15 毫秒
711.
712.
预应力混凝土箱梁横向框架效应有限元分析 总被引:1,自引:1,他引:1
以预应力混凝土箱梁桥顶板纵向开裂为工程背景,以箱梁顶板与腹板交接处两个角点的转角为基本未知量,基于箱梁纵向一维单元,利用最小势能原理推导出箱梁横向框架效应有限单元法的单元刚度矩阵,及相应的单元等效节点力,对比计算表明,该有限单元法计算精度与理论分析基本一致。实桥分析表明:现行规范计算箱梁角点弯矩相对安全,对于中点弯矩相对偏于不安全,设计过程不充分考虑混凝土箱梁横向框架效应可能导致顶板的纵向开裂。本文提出的有限单元法具有概念简单、运算速度快等优点,弥补了目前商业程序的不足,对工程设计具有一定的参考意义和推广价值。 相似文献
713.
当材性试验数据有限时,为了研究各力学参数的离散性和不确定性对结构性能计算的影响,需要对材料参数采用随机变量建模并基于概率理论构建刚度矩阵的随机模型。为此,首先将随机弹性张量分解为一组基张量和由材料参数构成的随机系数的线性组合,以考虑刚度矩阵各分量间的统计相关性;并利用最大熵原理确定由上述随机系数组成的随机向量的概率密度函数。采用基于Metropolis-Hasting算法的马尔科夫链蒙特卡罗方法用于计算与之相关的概率模型的拉格朗日乘子,并通过Matlab生成材料参数的随机样本。最后采用蒙特卡罗随机有限元法对横观各向同性材料构成的板式结构在不同荷载下的力学行为进行了数值分析。以刨花板材料为典型案例,与试验结果对比,验证了本文方法的效果和实用性。 相似文献
714.
对开洞蒙皮体及未开洞蒙皮体蒙皮效应进行了对比试验,通过未开洞蒙皮体试件与开洞蒙皮体试件抗剪性能的比较,研究开洞后对蒙皮体蒙皮效应的影响. 相似文献
715.
本文研究了圆环膜的横向自由振动.利用该振动的数学模型,得到了其形式解以及固有频率和节线的计算公式.该结果可用于涉及圆环膜振动的领域,也可以用于某些乐器. 相似文献
716.
High-resolution solution NMR experiments are extremely useful to characterize the location and the dynamics of hydrating water molecules at atomic resolution. However, these methods are severely limited by undesired incoherent transfer pathways such as those arising from exchange-relayed intra-molecular cross-relaxation. Here, we review several complementary exchange network editing methods that can be used in conjunction with other types of NMR hydration experiments such as magnetic relaxation dispersion and 1JNC′ measurements to circumvent these limitations. We also review several recent contributions illustrating how the original solution hydration NMR pulse sequence architecture has inspired new approaches to map other types of non-covalent interactions going well beyond the initial scope of hydration. Specifically, we will show how hydration NMR methods have evolved and have been adapted to binding site mapping, ligand screening, protein-peptide and peptide-lipid interaction profiling. 相似文献
717.
Cor-Jacques Kat 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(4):353-370
This article considers the mathematical modelling of the spring force of three interconnected rolling diaphragm type air springs used on a 40-ton tri-axle semi-trailer. The aim of the air spring model is to obtain a validated mathematical model that can be used in full vehicle multi-body dynamic simulations. The model considers the flow effects in the pipes connecting the three air springs as well as the mass transfer between them. Comparisons with experimental results show that the proposed mathematical model of the interconnected air springs is indeed able to accurately predict the pressures and forces of the air springs. 相似文献
718.
Y.Miyachi 《中国物理C(英文版)》2010,34(9)
The HERMES measured azimuthal amplitudes of cross sections and their transverse target single spin asymmetries for hadron productions in semi-inclusive deep inelastic scattering.From the extracted amplitudes,novel patton distribution functions can be studied.The recent results related to Sivers and Boer-Mulders distribution functions are discussed. 相似文献
719.
The pressure sensitivity of a laboratory standard microphone is determined using a reciprocity technique that measures the electrical transfer impedance of two microphones connected acoustically by a coupler. The electrical transfer impedance is a function of the coupler volume and the equivalent volumes of the microphones. The equivalent volume given as a function of the frequency can be determined in experiments or can be calculated if the equivalent volume at a low frequency as well as the resonance frequency and loss factor of the microphone diaphragm are known. Therefore, it is necessary to determine the resonance frequency and the loss factor accurately to obtain an accurate reading of the pressure sensitivity.In this paper, a new method to determine the resonance frequency and loss factor of a microphone diaphragm is proposed. The frequency response of the diaphragm displacement is measured by a laser vibrometer and the part of the response near the resonance frequency is used to determine the microphone parameters via least square fitting with the equation of a vibration model with one degree-of-freedom. Since the values measured by this method are close to the nominal values and the repeatability is highly feasible, the proposed method will be useful to determine the resonance frequency and loss factor of a microphone diaphragm. 相似文献
720.
Dragomir Saric 《Transactions of the American Mathematical Society》2006,358(1):233-249
We consider (real) earthquakes and, by their extensions, complex earthquakes of the hyperbolic plane . We show that an earthquake restricted to the boundary of is a quasisymmetric map if and only if its earthquake measure is bounded. Multiplying an earthquake measure by a positive parameter we obtain an earthquake path. Consequently, an earthquake path with a bounded measure is a path in the universal Teichmüller space. We extend the real parameter for a bounded earthquake into the complex parameter with small imaginary part. Such obtained complex earthquake (or bending) is holomorphic in the parameter. Moreover, the restrictions to of a bending with complex parameter of small imaginary part is a holomorphic motion of in the complex plane. In particular, a real earthquake path with bounded earthquake measure is analytic in its parameter.