全文获取类型
收费全文 | 263492篇 |
免费 | 5653篇 |
国内免费 | 2475篇 |
专业分类
电工技术 | 6439篇 |
技术理论 | 1篇 |
综合类 | 1828篇 |
化学工业 | 38447篇 |
金属工艺 | 11959篇 |
机械仪表 | 8426篇 |
建筑科学 | 7842篇 |
矿业工程 | 1120篇 |
能源动力 | 6926篇 |
轻工业 | 25471篇 |
水利工程 | 2433篇 |
石油天然气 | 2238篇 |
武器工业 | 169篇 |
无线电 | 33626篇 |
一般工业技术 | 47175篇 |
冶金工业 | 50871篇 |
原子能技术 | 4265篇 |
自动化技术 | 22384篇 |
出版年
2021年 | 2477篇 |
2020年 | 1724篇 |
2019年 | 2065篇 |
2018年 | 2897篇 |
2017年 | 2896篇 |
2016年 | 3112篇 |
2015年 | 2720篇 |
2014年 | 4265篇 |
2013年 | 12008篇 |
2012年 | 6796篇 |
2011年 | 9323篇 |
2010年 | 7696篇 |
2009年 | 8299篇 |
2008年 | 8790篇 |
2007年 | 8837篇 |
2006年 | 8238篇 |
2005年 | 7412篇 |
2004年 | 7007篇 |
2003年 | 7046篇 |
2002年 | 7168篇 |
2001年 | 7097篇 |
2000年 | 6290篇 |
1999年 | 6857篇 |
1998年 | 16830篇 |
1997年 | 11800篇 |
1996年 | 9122篇 |
1995年 | 6826篇 |
1994年 | 6028篇 |
1993年 | 5821篇 |
1992年 | 4131篇 |
1991年 | 4061篇 |
1990年 | 3644篇 |
1989年 | 3545篇 |
1988年 | 3484篇 |
1987年 | 2922篇 |
1986年 | 2859篇 |
1985年 | 3420篇 |
1984年 | 3058篇 |
1983年 | 2747篇 |
1982年 | 2553篇 |
1981年 | 2569篇 |
1980年 | 2434篇 |
1979年 | 2279篇 |
1978年 | 2241篇 |
1977年 | 2811篇 |
1976年 | 4174篇 |
1975年 | 1899篇 |
1974年 | 1796篇 |
1973年 | 1785篇 |
1972年 | 1461篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
本文将完全互补码(Complete Complementary Code, CCC)应用于多输入多输出(Multiple Input Multiple Output, MIMO)雷达目标探测中,针对具有非零多普勒的多目标检测问题,提出一种基于广义普洛黑-修-莫尔斯(Generalized Prouhet-Thue-Morse, GPTM)序列和二项式系数加权的信号处理方法。该方法分别在发射端和接收端进行处理,在发射端采用GPTM序列设计方法调整脉冲的发射顺序,以降低由多普勒引起的距离旁瓣;在接收端通过二项式设计(Binomial Design, BD)方法为各接收脉冲加上不同权重,扩大目标多普勒附近的清洁区。为综合上述两次处理的优势,将两次处理得到的距离多普勒谱进行逐点最小化处理,得到最终的距离多普勒谱,然后进行有序恒虚警检测。仿真结果表明,本文所提的信号处理方法具有良好的旁瓣抑制效果和多普勒分辨率,能够有效检测出非零多普勒目标。 相似文献
2.
3.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration. 相似文献
4.
Wireless Personal Communications - Besides anti-malware usage for the eradication of malicious attacks, researchers have developed epidemic models in order to gain more insights into the spread... 相似文献
5.
A. Nakano T. Shimazaki M. Sekiya H. Shiozawa K. Ohtsuka A. Aoyagi T. Iwakiri Z. Mikami M. Sato Y. Sugino K. Kinoshita T. Matsuoka T. Imamura Y. Takayama K. Yamamoto 《International Journal of Hydrogen Energy》2021,46(29):15649-15659
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa. 相似文献
6.
Abulyazied Dalia E. Alturki Asma M. Youness Rasha A. Abomostafa H. M. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):4077-4092
Journal of Inorganic and Organometallic Polymers and Materials - In this work, a borosilicate glass sample (5SiO2–45B2O3–20Na2O–25CaO–5Ag2O) was added to nano-sized... 相似文献
7.
Dr. Thomas Le Bihan Dr. Cathryn H. S. Driver Dr. Thomas Ebenhan Dr. Nathalie Le Bris Dr. Jan Rijn Zeevaart Prof. Dr. Raphaël Tripier 《ChemMedChem》2021,16(5):809-821
An improved glucose-chelator-albumin bioconjugate (GluCAB) derivative, GluCAB-2Mal, has been synthesized and studied for in vivo 64Cu-PET/CT imaging in breast cancer mice models together with its first-generation analogue GluCAB-1Mal. The radioligand works on the principle of tumor targeting through the enhanced permeability and retention (EPR) effect with a supportive role played by glucose metabolism. [64Cu]Cu-GluCAB-2Mal (99 % RCP) exhibited high serum stability with immediate binding to serum proteins. In vivo experiments for comparison between tumor targeting of [64Cu]Cu-GluCAB-2Mal and previous-generation [64Cu]Cu-GluCAB-1Mal encompassed microPET/CT imaging and biodistribution analysis in an allograft E0771 breast cancer mouse model. Tumor uptake of [64Cu]Cu-GluCAB-2Mal was clearly evident with twice as much accumulation as compared to its predecessor and a tumor/muscle ratio of up to 5 after 24 h. Further comparison indicated a decrease in liver accumulation for [64Cu]Cu-Glu-CAB-2Mal. 相似文献
8.
9.
10.
Felipe A. Perdomo Siti H. Khalit Claire S. Adjiman Amparo Galindo George Jackson 《American Institute of Chemical Engineers》2021,67(3):e17194
The SAFT-γ Mie group-contribution equation of state is used to represent the fluid-phase behavior of aqueous solutions of a variety of linear, branched, and cyclic amines. New group interactions are developed in order to model the mixtures of interest, including the like and unlike interactions between alkyl primary, secondary, and tertiary amine groups (NH2, NH, N), cyclic secondary and tertiary amine groups (cNH, cN), and cyclic methine-amine groups (cCHNH, cCHN) with water (H2O). The group-interaction parameters are estimated from appropriate experimental thermodynamic data for pure amines and selected mixtures. By taking advantage of the group-contribution nature of the method, one can describe the fluid-phase behavior of mixtures of molecules comprising those groups over broad ranges of temperature, pressure, and composition. A number of aqueous solutions of amines are studied including linear, branched aliphatic, and cyclic amines. Liquid–liquid equilibria (LLE) bounded by lower critical solution temperatures (LCSTs) have been reported experimentally and are reproduced here with the SAFT-γ Mie approach. The main feature of the approach is the ability not only to represent accurately the experimental data employed in the parameter estimation, but also to predict the vapor–liquid, liquid–liquid, and vapor–liquid–liquid equilibria, and LCSTs with the same set of parameters. Pure compound and binary phase diagrams of diverse types of amines and their aqueous solutions are assessed in order to demonstrate the main features of the thermodynamic and fluid-phase behavior. 相似文献