全文获取类型
收费全文 | 33663篇 |
免费 | 5162篇 |
国内免费 | 3983篇 |
专业分类
化学 | 23595篇 |
晶体学 | 461篇 |
力学 | 2069篇 |
综合类 | 335篇 |
数学 | 3739篇 |
物理学 | 12609篇 |
出版年
2024年 | 97篇 |
2023年 | 619篇 |
2022年 | 1093篇 |
2021年 | 1183篇 |
2020年 | 1313篇 |
2019年 | 1256篇 |
2018年 | 1108篇 |
2017年 | 1109篇 |
2016年 | 1516篇 |
2015年 | 1680篇 |
2014年 | 1836篇 |
2013年 | 2488篇 |
2012年 | 2914篇 |
2011年 | 3016篇 |
2010年 | 2102篇 |
2009年 | 2034篇 |
2008年 | 2301篇 |
2007年 | 2075篇 |
2006年 | 1841篇 |
2005年 | 1525篇 |
2004年 | 1178篇 |
2003年 | 979篇 |
2002年 | 942篇 |
2001年 | 677篇 |
2000年 | 669篇 |
1999年 | 631篇 |
1998年 | 503篇 |
1997年 | 506篇 |
1996年 | 531篇 |
1995年 | 442篇 |
1994年 | 435篇 |
1993年 | 328篇 |
1992年 | 291篇 |
1991年 | 269篇 |
1990年 | 197篇 |
1989年 | 154篇 |
1988年 | 156篇 |
1987年 | 107篇 |
1986年 | 116篇 |
1985年 | 98篇 |
1984年 | 69篇 |
1983年 | 63篇 |
1982年 | 52篇 |
1981年 | 36篇 |
1980年 | 46篇 |
1979年 | 34篇 |
1978年 | 30篇 |
1977年 | 16篇 |
1974年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
RNA-cleaving DNAzymes possess important roles in DNAzymes and have been widely used in the biosensors,DNA nanomachines owing to their ion-specific dependence.However,there are still challenges in constructing universal but versatile stimuli-responsive strategies of RNA-cleaving DNAzymes.Herein,a stimuli-responsive strategy for RNA-cleaving DNAzyme is proposed by the artful design of hairpin nanostructure,in which the activities of DNAzyme(Pb~(2+) -dependent DNAzyme as a model) in the hairpin's loop are p H-regulated by using the triplex stem as the "lock".Upon introducing the "key",p H values,the DNAzyme will be activated and fragment the substrate of it in the presence of Pb~(2+),accompanied by the turn-on of the fluorescence quenched by fluorescence resonance energy transfer(FRET).The regulation ability of p H can be controlled by the length and sequence of the triplex stem,and the wide p H regulation range may be helpful for the application of DNAzymes in biological medicine delivery systems. 相似文献
952.
In this study, single‐mode microwave heating was applied in epitaxial growth of b‐oriented MFI seed monolayer prepared by facile manual assembly, resulting in the formation of well‐intergrown and highly b‐oriented MFI film with few twins. It exhibited a precise molecular sieving property at a reaction temperature no higher than 100 °C within 2 hours, therefore making it possible for easy operation in an open environment. The capability for concurrent suppression of undesired out‐of‐plane twin growth and promotion of in‐plane epitaxial growth rate under mild reaction conditions was attributed to the obvious superiority of single‐mode microwave heating in comparison with conventional multi‐mode microwave heating in aspects of microwave field uniformity and intensity. Our research indicated that the single‐mode microwave heating technique could potentially be a useful tool for improving the microstructure and therefore the performance of diverse zeolite films. 相似文献
953.
The dielectric elastomer (DE) has attracted significant attention due to its desired features, including large deformation, fast response, and high energy density. However, for a DE actuator (DEA) utilizing a snap-through deformation mode, most existing theoretical models fail to predict its deformation path. This paper develops a new finite element method (FEM) based on the three-parameter Gent-Gent model suitable for capturing strain-stiffening behaviors. The simulation results are verified by experiments, indicating that the FEM can accurately characterize the snap-through path of a DE. The method proposed in this paper provides theoretical guidance and inspiration for designing and applying DEs and bistable electroactive actuators. 相似文献
954.
提出一种基于车桥耦合动力学理论的梁式桥阻尼比识别方法. 首先按照动力学理论将测试车设计为单自由度体系, 然后利用安装在测试车上的传感器采集信号, 从测试车与桥梁接触点响应信号中得到梁式桥响应的信号, 基于车桥耦合动力学原理滤波处理得到包含梁式桥第一阶频率的信号, 最后假定梁式桥阻尼比值, 通过假定的梁式桥阻尼比值获取假定的梁式桥第一阶振型, 不断循环直至假定的阻尼比值下计算的第一阶振型最大值点居中, 即为识别的梁式桥真实阻尼比. 本文首先从车桥耦合动力学理论推导上说明了该方法的可行性, 然后考虑在不同车速与非恒定车速、路面粗糙度、环境噪音等影响因素下进行车桥耦合动力学模型分析, 最后通过实桥试验进行了初步验证. 研究结果表明: 该方法能一定程度上克服外界不利因素的影响, 达到识别梁式桥阻尼比的目的, 为识别梁式桥阻尼比提供一种更优方法, 其具有参数设置较少、操作简单方便以及更高测试精度等优点, 同时有助于推动基于车桥耦合的车桥耦合动力学理论技术在梁式桥模态参数识别工作中的实际工程应用. 相似文献
955.
Nonlinear Dynamics - This article investigates the issue of hybrid-triggered control for fuzzy Markov jump system under input saturation. First, a hybrid-triggered control scheme is presented,... 相似文献
956.
Zeng Liangwei Belić Milivoj R. Mihalache Dumitru Shi Jincheng Li Jiawei Li Siqi Lu Xiaowei Cai Yi Li Jingzhen 《Nonlinear dynamics》2022,108(2):1671-1680
Nonlinear Dynamics - We demonstrate the existence of various types of gap localized modes, including one- and two-dimensional (1D and 2D) single solitons and soliton clusters, as well as the... 相似文献
957.
Nonlinear Dynamics - A time-delayed proportional–derivative controller is applied to suppress the nonlinear vibration of a rigid rotor suspended by the active magnetic bearing (AMB) subjected... 相似文献
958.
The relative stability of the 3A2, 1A2, and 1A1 states of phenylnitrene is evaluated by means of ab initio calculations followed by difference-dedicated configuration interaction (DDCI). This approach is based on effective Hamiltonian theory at a low order of perturbation to select rationally the determinants which contribute to the energy difference. The CI space built on this criterion is then treated variationally. The method allows a considerable reduction of the CI space compared with a complete CAS*SDCI calculation (where CAS stands for complete active space). Depending on the concerned energy difference, different model spaces may be chosen, as illustrated in the 3A2 → 1A2 and the 3A2 → 1A1 transitions in phenylnitrene. Since the CI space may reach considerable dimensions, a direct CI algorithm for selected CI spaces, the SCIEL algorithm, has been used to perform the calculations. The results are in excellent agreement with previous calculations and with available experimental data. © 1996 by John Wiley & Sons, Inc. 相似文献
959.
A new series of sulfur-containing side-chain liquid crystalline polymer is described. Mesomorphic side chains with methylene spacers of different lengths have been synthesized, and their structures were identified by nuclear magnetic resonance, infrared and mass spectrometry. The liquid crystalline nature of the polymers was characterized by microscopy and differential scanning calorimetry. 相似文献
960.