全文获取类型
收费全文 | 274291篇 |
免费 | 75271篇 |
国内免费 | 48459篇 |
专业分类
电工技术 | 32520篇 |
技术理论 | 15篇 |
综合类 | 25947篇 |
化学工业 | 39523篇 |
金属工艺 | 29430篇 |
机械仪表 | 12127篇 |
建筑科学 | 19702篇 |
矿业工程 | 14938篇 |
能源动力 | 10887篇 |
轻工业 | 25717篇 |
水利工程 | 8853篇 |
石油天然气 | 17032篇 |
武器工业 | 4128篇 |
无线电 | 40462篇 |
一般工业技术 | 41442篇 |
冶金工业 | 11511篇 |
原子能技术 | 2211篇 |
自动化技术 | 61576篇 |
出版年
2024年 | 1781篇 |
2023年 | 5650篇 |
2022年 | 6650篇 |
2021年 | 8646篇 |
2020年 | 11076篇 |
2019年 | 20049篇 |
2018年 | 21750篇 |
2017年 | 23289篇 |
2016年 | 22884篇 |
2015年 | 22531篇 |
2014年 | 22362篇 |
2013年 | 22624篇 |
2012年 | 22205篇 |
2011年 | 18976篇 |
2010年 | 16835篇 |
2009年 | 13646篇 |
2008年 | 11578篇 |
2007年 | 10924篇 |
2006年 | 10241篇 |
2005年 | 9295篇 |
2004年 | 10531篇 |
2003年 | 8910篇 |
2002年 | 8356篇 |
2001年 | 7370篇 |
2000年 | 7226篇 |
1999年 | 7262篇 |
1998年 | 6543篇 |
1997年 | 5606篇 |
1996年 | 5276篇 |
1995年 | 5044篇 |
1994年 | 4198篇 |
1993年 | 3569篇 |
1992年 | 3261篇 |
1991年 | 2438篇 |
1990年 | 1905篇 |
1989年 | 1754篇 |
1988年 | 1374篇 |
1987年 | 498篇 |
1986年 | 427篇 |
1985年 | 305篇 |
1984年 | 233篇 |
1983年 | 156篇 |
1982年 | 202篇 |
1981年 | 193篇 |
1980年 | 135篇 |
1976年 | 242篇 |
1975年 | 219篇 |
1972年 | 247篇 |
1971年 | 138篇 |
1960年 | 206篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
2.
3.
通过固液掺杂、等静压压制、中频烧结的方法,制备了不同的氧化镧、氧化钇、氧化锆三元掺杂成分比例的钨电极材料烧结棒材,探究了不同成分配比对样品显微组织、第二相粒子分布以及宏观力学性能的影响。结果表明,氧化镧、氧化钇、氧化锆三元复合添加能够有效改善第二相粒子在钨基体中的分布形态,降低第二相在晶界的过度富集,提高钨电极材料的综合力学性能。并且当添加成分镧、钇、锆质量比为3:1:1时,材料具有最好的综合力学性能,致密度可达96.04%,显微硬度可达549.37HV0.3,抗压强度可达3785MPa,原因是此配比下第二相粒子最为细小均匀,弥散程度最高,对基体晶粒的细化作用最好,该配比下钨基体平均晶粒尺寸达到10.3μm。 相似文献
4.
Shanshan Zhuang Wenxiong Zheng Yunong Na Naiyi Chen Fan Gong Bingxuan Huang Stephen Brennan Charles Congyi Liu Jian Cheng Lukai Ma Huifan Liu 《International Journal of Food Science & Technology》2022,57(2):1093-1103
The β-Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat-soluble and has low bioavailability. In previous in-vitro assays evaluating antioxidant and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco-2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high-performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results. 相似文献
5.
Peng Wang Yan Li Yujiao Qu Baowei Wang Jingxin Sun Chunwei Miao Ming Huang He Huang Congxiang Zhang 《International Journal of Food Science & Technology》2022,57(6):3428-3439
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP. 相似文献
6.
7.
Fan Deng-Ping Huang Ziling Zheng Peng Liu Hong Qin Xuebin Van Gool Luc 《国际自动化与计算杂志》2022,19(4):257-287
Machine Intelligence Research - This paper aims to conduct a comprehensive study on facial-sketch synthesis (FSS). However, due to the high cost of obtaining hand-drawn sketch datasets, there is a... 相似文献
8.
边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明:和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。 相似文献
9.
Multimedia Tools and Applications - The study presents a new approach to automate segmentation of clinically significant brain tumor and, to a certain extent, addresses two major issues associated... 相似文献
10.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献