全文获取类型
收费全文 | 228315篇 |
免费 | 18635篇 |
国内免费 | 9205篇 |
专业分类
电工技术 | 13145篇 |
技术理论 | 14篇 |
综合类 | 13386篇 |
化学工业 | 37764篇 |
金属工艺 | 11895篇 |
机械仪表 | 13759篇 |
建筑科学 | 18660篇 |
矿业工程 | 5624篇 |
能源动力 | 6570篇 |
轻工业 | 14479篇 |
水利工程 | 3813篇 |
石油天然气 | 12195篇 |
武器工业 | 1668篇 |
无线电 | 28595篇 |
一般工业技术 | 29192篇 |
冶金工业 | 11815篇 |
原子能技术 | 2480篇 |
自动化技术 | 31101篇 |
出版年
2024年 | 382篇 |
2023年 | 3478篇 |
2022年 | 5468篇 |
2021年 | 8669篇 |
2020年 | 6575篇 |
2019年 | 5637篇 |
2018年 | 6207篇 |
2017年 | 6957篇 |
2016年 | 6353篇 |
2015年 | 8384篇 |
2014年 | 10943篇 |
2013年 | 13895篇 |
2012年 | 14165篇 |
2011年 | 15942篇 |
2010年 | 13597篇 |
2009年 | 13224篇 |
2008年 | 12604篇 |
2007年 | 12118篇 |
2006年 | 12358篇 |
2005年 | 10870篇 |
2004年 | 7473篇 |
2003年 | 6720篇 |
2002年 | 6310篇 |
2001年 | 5623篇 |
2000年 | 5393篇 |
1999年 | 5971篇 |
1998年 | 5484篇 |
1997年 | 4490篇 |
1996年 | 4047篇 |
1995年 | 3445篇 |
1994年 | 2868篇 |
1993年 | 2278篇 |
1992年 | 1744篇 |
1991年 | 1292篇 |
1990年 | 1028篇 |
1989年 | 899篇 |
1988年 | 696篇 |
1987年 | 497篇 |
1986年 | 380篇 |
1985年 | 326篇 |
1984年 | 199篇 |
1983年 | 186篇 |
1982年 | 159篇 |
1981年 | 145篇 |
1980年 | 135篇 |
1979年 | 100篇 |
1978年 | 63篇 |
1977年 | 63篇 |
1976年 | 77篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Applied Composite Materials - The paper presents a study on the ballistic performance of 3D woven wadded through-the-thickness angle-interlock fabrics (TTAI) fabric reinforced composites. Their... 相似文献
3.
Xiao-Mei Sha Li-Jun Zhang Wen-Mei Chen Guang-Yao Wang Jin-Lin Li Zi-Zi Hu Zong-Cai Tu 《International Journal of Food Science & Technology》2022,57(3):1573-1586
Thermal action in extraction process had effects on characteristic tryptic peptides identification and gelling properties of porcine gelatin. SDS-PAGE, HPLC-LTQ/Orbitrap high-resolution mass spectrometry, texture analyser and rheometer were used to evaluate collagen depolymerisation degree, characteristic tryptic peptides and gelling properties of gelatins prepared in various thermal actions. Results showed that with increasing temperature and time, depolymerisation degree enlarged, while gel strength, gelling and melting temperature decreased. Mass spectra showed that 47 and 49 common characteristic tryptic peptides were identified in gelatins extracted at 50 °C and 100 °C with various times, respectively. Moreover, 34 common characteristic tryptic peptides were identified in all gelatin samples. Further comparison between this work and our previous investigations yielded 20 common characteristic tryptic peptides, which stably exist in various thermal actions. These common characteristic tryptic peptides may be very helpful for the accurate authentication of porcine gelatin. 相似文献
4.
Hua Yang Shi-Xiao Wei Han Chen Lang Chen Chak-Tong Au Ting-Liang Xie Shuang-Feng Yin 《American Institute of Chemical Engineers》2022,68(10):e17810
A high-throughput (105.5 g/h) passive four-stage asymmetric oscillating feedback microreactor using chaotic mixing mechanism was developed to prepare aggregated Barium sulfate (BaSO4) particles of high primary nanoparticle size uniformity. Three-dimensional unsteady simulations showed that chaotic mixing could be induced by three unique secondary flows (i.e., vortex, recirculation, and oscillation), and the fluid oscillation mechanism was examined in detail. Simulations and Villermaux–Dushman experiments indicate that almost complete mixing down to molecular level can be achieved and the prepared BaSO4 nanoparticles were with narrow primary particle size distribution (PSD) having geometric standard deviation, σg, less than 1.43 when the total volumetric flow rate Qtotal was larger than 10 ml/min. By selecting Qtotal and reactant concentrations, average primary particle size can be controlled from 23 to 109 nm as determined by microscopy. An average size of 26 nm with narrow primary PSD (σg = 1.22) could be achieved at Qtotal of 160 ml/min. 相似文献
5.
Guishang Pei Junyi Xiang Qingyun Huang Xuewei Lv 《Journal of the American Ceramic Society》2022,105(10):6359-6369
A double pyrovanadate CaMgV2O7 sample was synthesized via a facile solid-state route under an air atmosphere. The nonequilibrium formation pathways of the CaMgV2O7 were investigated via powder X-ray diffraction. A multistep reactions path (metavanadates–pyrovanadates–double pyrovanadate CaMgV2O7) was proposed to describe the formation of the CaMgV2O7 considering the thermodynamic and kinetic factors. The cell unit parameters of the CaMgV2O7 sample indicated the crystallization according to a monoclinic system with space group P12/c1(14), and the lattice parameters of a = 6.756 Å, b = 14.495 Å, c = 11.253 Å, β = 99.12, and V = 108.806 Å3. X-ray photoelectron spectroscopy also confirmed the +5 oxidation state vanadium in CaMgV2O7. The endothermic effects at 1033 and 1143 K were related to the incongruent melting and liquidus temperatures of CaMgV2O7, respectively. The comprehensive thermodynamic properties of CaMgV2O7 were established in both low- and high-temperature regions, utilizing a physical property measurement system and multi-high-temperature calorimetry (96 lines). The heat capacity (200 J mol K−1) and entropy (198 J mol K−1) at 298.15 K were computed based on the low-temperature heat capacity values, and the enthalpy of formation at 298.15 K was also estimated. The fitted high-temperature capacity can be used to obtain the changes in the enthalpy, entropy, and Gibbs free energy. This study is part of building a reliable thermodynamic database of the CaO–MgO–V2O5 system. 相似文献
6.
7.
8.
使用结构为42°Y-X LiTaO3(600 nm)/SiO2(500 nm)/Si的SOI衬底,通过抑制横向模式等优化设计,研制了单端谐振器和声表面波滤波器。经测试,谐振器的谐振频率为1.5 GHz,品质因数(Q)值高达4 000;滤波器的中心频率为1 370 MHz,插入损耗为-1.2 dB,1 dB带宽为74 MHz,相对带宽达到5.4%,阻带抑制大于40 dB,且温度系数在-55~+85 ℃时优于-9×10-6/℃。该产品具有高频、宽带、低损耗、低温漂、高阻带抑制的特点,其性能指标优异,具有很好的实用性。 相似文献
9.
Xu Cheng Rong Jiawei Chen Yulin Wu Hang Duan Shihong 《International Journal of Wireless Information Networks》2022,29(1):1-13
International Journal of Wireless Information Networks - Source seeking problem has been faced in many fields, especially in search and rescue applications. We proposed a virtual structure-based... 相似文献
10.