全文获取类型
收费全文 | 3690篇 |
免费 | 755篇 |
国内免费 | 463篇 |
专业分类
化学 | 1691篇 |
晶体学 | 66篇 |
力学 | 135篇 |
综合类 | 58篇 |
数学 | 298篇 |
物理学 | 1034篇 |
无线电 | 1626篇 |
出版年
2024年 | 19篇 |
2023年 | 117篇 |
2022年 | 163篇 |
2021年 | 177篇 |
2020年 | 207篇 |
2019年 | 147篇 |
2018年 | 142篇 |
2017年 | 156篇 |
2016年 | 168篇 |
2015年 | 196篇 |
2014年 | 225篇 |
2013年 | 242篇 |
2012年 | 272篇 |
2011年 | 259篇 |
2010年 | 241篇 |
2009年 | 268篇 |
2008年 | 255篇 |
2007年 | 231篇 |
2006年 | 217篇 |
2005年 | 216篇 |
2004年 | 138篇 |
2003年 | 117篇 |
2002年 | 103篇 |
2001年 | 116篇 |
2000年 | 98篇 |
1999年 | 68篇 |
1998年 | 42篇 |
1997年 | 46篇 |
1996年 | 44篇 |
1995年 | 26篇 |
1994年 | 22篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 16篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1965年 | 2篇 |
排序方式: 共有4908条查询结果,搜索用时 390 毫秒
111.
Acta Mathematicae Applicatae Sinica, English Series - This paper summarizes the parameter estimation of systems with set-valued signals, which can be classified to three catalogs: one-time... 相似文献
112.
Hang Liu Juan Zhang Prof. Xinxin Xu Prof. Qiang Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4403-4409
Capacitive deionization is a promising technique in sea water desalination. Compared with common electrodes, mixed capacitive-deionization electrodes exhibit better performance in sea water desalination because they integrate pseudocapacitance and electric double-layer capacitance in one system. Herein, a 3D binder-free mixed capacitive-deionization electrode was fabricated by direct electrodeposition of SiW12O404− and polyaniline on a 3D exfoliated graphite carrier. In this electrode, SiW12O404−/polyaniline composite particles with a size of about 100–120 nm are dispersed homogenously on the 3D exfoliated graphite carrier. Its specific capacitance reaches 352 F g−1 at 1 A g−1. With increasing current from 1 to 20 A g−1, the specific capacitance only decays by 32 %. When employed in sea water desalination, the performance of this mixed capacitive-deionization electrode is also excellent. At 1.2 V, the salt adsorption capacity of this mixed electrode reaches 23.1 mg g−1 with a salt adsorption rate of 1.38 mg g−1 min−1 in 500 mg L−1 NaCl. The performance of this electrode is well retained after 30 cycles. The excellent sea water desalination performance originates from the synergistic effect between SiW12O404− and polyaniline. This work has developed polyoxometalate as a new material for capacitive-deionization electrodes. 相似文献
113.
Fangyuan Zhou Lesong Li Kao Lin Feng Zhang Prof. Dr. Guo-Jun Deng Dr. Hang Gong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4246-4250
The radical–radical coupling reaction is an important synthetic strategy. In this study, the iron-catalyzed radical–radical cross-coupling reaction based on the decarboxylation of keto acids and decarbonylation of aliphatic aldehydes to obtain valuable aryl ketones is reported for the first time. Remarkably, when tertiary aldehydes were used as carbonyl sources, ketone esters were selectively obtained instead of ketones. The gram-scale preparation of aryl ketone through this strategy was easily achieved by using only 3 mol % of the iron catalyst. As a proof-of-concept, the bioactive molecule flurprimidol was synthesized in two steps by using this strategy. 相似文献
114.
115.
116.
The design of thermoelastic damping (TED) affected by the phase-lagging non-Fourier heat conduction effects becomes significant but challenging for enlarging the quality factor of widely-used microresonators operating in extreme situations, including ultra-high excitation frequency and ultra-low working temperature. However, there does not exist a rational method for designing the TED in the framework of non-Fourier heat conduction law. This work, therefore, proposes a design framework to achieve low thermoelastic dissipation of microresonators governed by the phase-lagging heat conduction law. The equation of motion and the heat conduction equation for phase-lagging TED microresonators are derived first, and then the non-Fourier TED design problem is proposed. A topology optimization-based rational design method is used to resolve the design problem. What is more, a two-dimensional (2D) plain-strain-based finite element method (FEM) is developed as a solver for the topology optimization process. Based on the suggested rational design technique, numerical instances with various phase lags are investigated. The results show that the proposed design method can remarkably reduce the dissipation of microresonators by tailoring their substructures. 相似文献
117.
Necessary optimality conditions for efficient solutions of unconstrained and vector equilibrium problems with equality and inequality constraints are derived. Under assumptions on generalized convexity, necessary optimality conditions for efficient solutions become sufficient optimality conditions. Note that it is not required here that the ordering cone in the objective space has a nonempty interior. 相似文献
118.
We solve the connectedness problem for a class of nests of order type ω with finite dimensional atoms. 相似文献
119.
为了保证卫星发射前的地面姿轨控半物理试验的顺利进行,研制了姿轨控分系统半物理仿真地面测试系统。为了满足相关类似卫星型号的通用化测试,本套仿真测试系统采用通用模块化的设计架构,同时采用现今主流的PXI总线测试技术(配合VPC转接电路板)。使用标准通用cPCI总线板卡以及部分自制FPGA可编程cPCI总线板卡实现各测试模块的功能。这种架构不仅能实现功能模块化,便于后续的功能扩展及维修,同时具有可靠性高、搭建时间快、可维护性强的优点,且体积小,稳定性强,能适应不同测试对象的测试环境条件,适合长途运输。本文介绍了系统的总体设计结构,重点介绍了模拟总体电源、动力学仿真机、电信号源、程序加载以及外围设备等硬件系统功能,以及相关配套软件的基本功能。测试系统经过与卫星的星地联试,功能性及使用性均得到了验证,测试结论符合设计之初功能性及通用化的构想。 相似文献
120.