全文获取类型
收费全文 | 34968篇 |
免费 | 3620篇 |
国内免费 | 2181篇 |
专业分类
电工技术 | 2834篇 |
技术理论 | 4篇 |
综合类 | 2770篇 |
化学工业 | 4999篇 |
金属工艺 | 2172篇 |
机械仪表 | 2224篇 |
建筑科学 | 3193篇 |
矿业工程 | 998篇 |
能源动力 | 1114篇 |
轻工业 | 2250篇 |
水利工程 | 653篇 |
石油天然气 | 1706篇 |
武器工业 | 345篇 |
无线电 | 4208篇 |
一般工业技术 | 4169篇 |
冶金工业 | 1455篇 |
原子能技术 | 398篇 |
自动化技术 | 5277篇 |
出版年
2024年 | 137篇 |
2023年 | 654篇 |
2022年 | 1106篇 |
2021年 | 1785篇 |
2020年 | 1273篇 |
2019年 | 959篇 |
2018年 | 1057篇 |
2017年 | 1218篇 |
2016年 | 1061篇 |
2015年 | 1445篇 |
2014年 | 1774篇 |
2013年 | 2341篇 |
2012年 | 2462篇 |
2011年 | 2561篇 |
2010年 | 2334篇 |
2009年 | 2105篇 |
2008年 | 2132篇 |
2007年 | 2035篇 |
2006年 | 1923篇 |
2005年 | 1644篇 |
2004年 | 1172篇 |
2003年 | 1061篇 |
2002年 | 1191篇 |
2001年 | 1034篇 |
2000年 | 828篇 |
1999年 | 712篇 |
1998年 | 481篇 |
1997年 | 442篇 |
1996年 | 394篇 |
1995年 | 337篇 |
1994年 | 262篇 |
1993年 | 182篇 |
1992年 | 154篇 |
1991年 | 139篇 |
1990年 | 104篇 |
1989年 | 65篇 |
1988年 | 46篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1973年 | 4篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
恶意代码数量已经呈现爆炸式增长,对于恶意代码的检测防护显得尤为重要.近几年,基于深度学习的恶意代码检测方法开始出现,基于此,提出一种新的检测方法,将恶意代码二进制文件转化为十进制数组,并利用一维卷积神经网络(1 Dimention Convolutional Neural Networks,1D CNN)对数组进行分类和识别.针对代码家族之间数量不平衡的现象,该算法选择在分类预测上表现良好的XGBoost,并对Vision Research Lab中的25个不同恶意软件家族的9458个恶意软件样本进行了实验.实验结果表明,所提的方法分类预测精度达到了97%. 相似文献
3.
4.
Dong Liu Xia Ke Zhong-Ce Hu Yu-Guo Zheng 《Journal of Bioscience and Bioengineering》2021,131(5):518-524
5.
Zhenkun Ke Xin Cao Chuanli Shan Lifen Shi Pingping Wang Yong Yang Fengyang Zhao Jiedong Cui Jinwei Li Gang Zhou Min Guan Tao Yu 《Ceramics International》2021,47(14):19605-19613
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased. 相似文献
6.
Fangjun Zhu You Shi Guorong Hu Zhongdong Peng Yanbing Cao Qian Sun Zhichen Xue Yinjia Zhang Ke Du 《Ceramics International》2021,47(3):3070-3078
Titanium and boron are simultaneously introduced into LiNi0.8Co0.1Mn0.1O2 to improve the structural stability and electrochemical performance of the material. X-ray diffraction studies reveal that Ti4+ ion replaces Li+ ion and reduces the cation mixing; B3+ ion enters the tetrahedron of the transition metal layers and enlarges the distance of the [LiO6] layers. The co-doped sample has spherical secondary particles with elongated and enlarged primary particles, in which Ti and B elements distribute uniformly. Electrochemical studies reveal the co-doped sample has improved rate performance (183.1 mAh·g-1 at 1 C and 155.5 mAh·g-1 at 10 C) and cycle stability (capacity retention of 94.7% after 100 cycles at 1 C). EIS and CV disclose that Ti and B co-doping reduces charge transfer impedance and suppresses phase change of LiNi0.8Co0.1Mn0.1O2. 相似文献
7.
Pu Mao Jiping Wang Peng Xiao Lixue Zhang Fang Kang Hao Gong 《Ceramics International》2021,47(1):111-120
In this work, we developed a novel system of isovalent Zr4+ and donor Nb5+ co-doped CaCu3Ti4O12 (CCTO) ceramics to enhance dielectric response. The influences of Zr4+ and Nb5+ co-substituting on the colossal dielectric response and relaxation behavior of the CCTO ceramics fabricated by a conventional solid-phase synthesis method were investigated methodically. Co-doping of Zr4+ and Nb5+ ions leads to a significant reduction in grain size for the CCTO ceramics sintered at 1060 °C for 10 h. XRD and Raman results of the CaCu3Ti3.8-xZrxNb0.2O12 (CCTZNO) ceramics show a cubic perovskite structure with space group Im-3. The first principle calculation result exhibits a better thermodynamic stability of the CCTO structure co-doped with Zr4+ and Nb5+ ions than that of single-doped with Zr4+ or Nb5+ ion. Interestingly, the CCTZNO ceramics exhibit greatly improved dielectric constant (~105) at a frequency range of 102–105 Hz and at a temperature range of 20–210 °C, indicating a giant dielectric response within broader frequency and temperature ranges. The dielectric properties of CCTZNO ceramics were analyzed from the viewpoints of defect-dipole effect and internal barrier layer capacitance (IBLC) model. Accordingly, the immensely enhanced dielectric response is primarily ascribed to the complex defect dipoles associated with oxygen vacancies by co-doping Zr4+ and Nb5+ ions into CCTO structure. In addition, the obvious dielectric relaxation behavior has been found in CCTZNO ceramics, and the relaxation process in middle frequency regions is attributed to the grain boundary response confirmed by complex impedance spectroscopy and electric modulus. 相似文献
8.
Sheng Mingming Yang Rongkun Gong Hongyu Zhang Yujun Lin Xiao Jing Jie 《Journal of Materials Science》2022,57(10):5805-5824
Journal of Materials Science - With the extensive use of high-power electronic appliances, polymer-based thermal insulation composites with excellent thermal properties are utilized in the field of... 相似文献
9.