全文获取类型
收费全文 | 6329篇 |
免费 | 857篇 |
国内免费 | 578篇 |
专业分类
化学 | 3466篇 |
晶体学 | 50篇 |
力学 | 283篇 |
综合类 | 51篇 |
数学 | 486篇 |
物理学 | 1804篇 |
无线电 | 1624篇 |
出版年
2024年 | 27篇 |
2023年 | 210篇 |
2022年 | 209篇 |
2021年 | 271篇 |
2020年 | 287篇 |
2019年 | 212篇 |
2018年 | 182篇 |
2017年 | 190篇 |
2016年 | 263篇 |
2015年 | 236篇 |
2014年 | 317篇 |
2013年 | 373篇 |
2012年 | 506篇 |
2011年 | 478篇 |
2010年 | 354篇 |
2009年 | 395篇 |
2008年 | 395篇 |
2007年 | 363篇 |
2006年 | 368篇 |
2005年 | 266篇 |
2004年 | 189篇 |
2003年 | 160篇 |
2002年 | 154篇 |
2001年 | 121篇 |
2000年 | 133篇 |
1999年 | 154篇 |
1998年 | 126篇 |
1997年 | 125篇 |
1996年 | 101篇 |
1995年 | 120篇 |
1994年 | 101篇 |
1993年 | 70篇 |
1992年 | 82篇 |
1991年 | 63篇 |
1990年 | 52篇 |
1989年 | 33篇 |
1988年 | 19篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有7764条查询结果,搜索用时 15 毫秒
61.
In recent years, research on applications of three-way decision (e.g., TWD) has attracted the attention of many scholars. In this paper, we combine TWD with multi-attribute decision-making (MADM). First, we utilize the essential idea of TOPSIS in MADM theory to propose a pair of new ideal relation models based on TWD, namely, the three-way ideal superiority model and the three-way ideal inferiority model. Second, in order to reduce errors caused by the subjectivity of decision-makers, we develop two new methods to calculate the state sets for the two proposed ideal relation models. Third, we employ aggregate relative loss functions to calculate the thresholds of each object, divide all objects into three different territories and sort all objects. Then, we use a concrete example of building appearance selection to verify the rationality and feasibility of our proposed models. Furthermore, we apply comparative analysis, Spearman’s rank correlation analysis and experiment analysis to illustrate the consistency and superiority of our methods. 相似文献
62.
63.
64.
65.
66.
采用TEOS源LPCVD法制备了SiO2薄膜,采用膜厚仪对薄膜的厚度进行测试.通过不同条件下SiO2薄膜的厚度变化,讨论了TEOS源温度、反应压力及反应温度等工艺条件对淀积速率和均匀性的影响.结果表明,在40℃,50 Pa左右,淀积速率随TEOS源温度、反应压力基本呈线性增大.通过多次试验改进,提出了SiO2膜淀积的典... 相似文献
67.
68.
Deep submicron n-channel metal-oxide-semiconductor field-effect transistors (NMOSFETs) with shallow trench isolation (STI) are exposed to ionizing dose radiation under different bias conditions.The total ionizing dose radiation induced subthreshold leakage current increase and the hump effect under four different irradiation bias conditions including the worst case (ON bias) for the transistors are discussed.The high electric fields at the corners are partly responsible for the subthreshold hump effect.Charge trapped in the isolation oxide,particularly at the Si/SiO 2 interface along the sidewalls of the trench oxide creates a leakage path,which becomes a dominant contributor to the offstate drain-to-source leakage current in the NMOSFET.Non-uniform charge distribution is introduced into a threedimensional (3D) simulation.Good agreement between experimental and simulation results is demonstrated.We find that the electric field distribution along with the STI sidewall is important for the radiation effect under different bias conditions. 相似文献
69.
Load optimal design for a primary test stand facility based on a zero-dimensional load model 下载免费PDF全文
In order to couple the numerical simulation of a primary test stand driver with an optimal load design, a zero-dimensional wire array load model is designed based on the Saturn load model using PSPICE, which is an upgraded version of the Simulation Program with Integrated Circuit Emphasis (SPICE) designed by the ORCAD Corporation to perform circuit simulations. This paper calculates different load parameters and discusses factors influencing the driving current curve. With appropriate driving current curves chosen, further magneto-hydrodynamic calculations are carried out and discussed to provide the best results for experiments. The suggested optimal load parameters play an important role in experimental load design. 相似文献
70.
We represent a design of a 20 W, fiber-coupled diode laser module based on 26 single emitters at 520 nm. The module can produce more than 20 W output power from a standard fiber with core diameter of 400 μm and numerical aperture (NA) of 0.22. To achieve a 20 W laser beam, the spatial beam combination and polarization beam combination by polarization beam splitter are used to combine output of 26 single emitters into a single beam, and then an aspheric lens is used to couple the combined beam into an optical fiber. The simulation shows that the total coupling efficiency is more than 95%. 相似文献