全文获取类型
收费全文 | 20720篇 |
免费 | 1547篇 |
国内免费 | 672篇 |
专业分类
电工技术 | 976篇 |
技术理论 | 3篇 |
综合类 | 1238篇 |
化学工业 | 3723篇 |
金属工艺 | 988篇 |
机械仪表 | 1254篇 |
建筑科学 | 1603篇 |
矿业工程 | 431篇 |
能源动力 | 552篇 |
轻工业 | 1453篇 |
水利工程 | 329篇 |
石油天然气 | 1055篇 |
武器工业 | 153篇 |
无线电 | 2170篇 |
一般工业技术 | 3055篇 |
冶金工业 | 1227篇 |
原子能技术 | 248篇 |
自动化技术 | 2481篇 |
出版年
2024年 | 73篇 |
2023年 | 281篇 |
2022年 | 441篇 |
2021年 | 578篇 |
2020年 | 488篇 |
2019年 | 444篇 |
2018年 | 465篇 |
2017年 | 589篇 |
2016年 | 527篇 |
2015年 | 698篇 |
2014年 | 836篇 |
2013年 | 1088篇 |
2012年 | 1162篇 |
2011年 | 1241篇 |
2010年 | 1057篇 |
2009年 | 1025篇 |
2008年 | 1096篇 |
2007年 | 1048篇 |
2006年 | 1128篇 |
2005年 | 1098篇 |
2004年 | 691篇 |
2003年 | 653篇 |
2002年 | 604篇 |
2001年 | 522篇 |
2000年 | 671篇 |
1999年 | 724篇 |
1998年 | 639篇 |
1997年 | 560篇 |
1996年 | 496篇 |
1995年 | 466篇 |
1994年 | 337篇 |
1993年 | 250篇 |
1992年 | 209篇 |
1991年 | 171篇 |
1990年 | 134篇 |
1989年 | 125篇 |
1988年 | 96篇 |
1987年 | 47篇 |
1986年 | 49篇 |
1985年 | 44篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1970年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
991.
992.
采用熔融急冷法制备Na2 O -Bi2 O3-B2 O3体系玻璃。X射线粉末衍射表明该体系的成玻性能较好 ,成玻范围较宽 ;密度、粉末透红外光谱和TSDC研究表明 ,玻璃中的硼元素具有“硼反常”现象 ,铋元素有〔BiO3〕和〔BiO6 〕两种微结构 ,玻璃中的碱金属离子以及硼元素和铋元素的微结构在外场作用下定向排列 ,表现出明显的SHG效应。 相似文献
993.
Dong‐Jun Wang Chen‐Bin Gu Peng‐Lei Chen Shi‐Xiong Liu Zhen Zhen Jian‐Cheng Zhang Xin‐Hou Liu 《应用聚合物科学杂志》2003,87(2):280-283
Using the interfacial gel polymerization method, a heat‐resistant gradient‐index polymer optical fiber (GI POF) was developed based on the copolymer of methyl methacrylate (MMA) and N‐isopropylmaleimide (IPMI) as the matrix material and bromobenzene (BB) as dopant. The gradient distribution of IPMI in the GI POF rod was determined by element analysis. IPMI had great advantage in improving glass transition temperature (Tg) and forming a gradient‐index profile. There was a significant enhancement in the heat‐resistant property in comparison with a conventional GI POF rod. The combination of high thermal stability and easy fabrication makes the novel BB–IPMI–MMA system very suitable for heat‐resistant GI POF. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 280–283, 2003 相似文献
994.
Junxia Wang Genshui Wang Hengchang Nie Xuefeng Chen Fei Cao Xianlin Dong Yan Gu Hongliang He 《Journal of the American Ceramic Society》2013,96(8):2370-2373
The low‐temperature sintering and electric properties of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 (PZTN 95/5) ferroelectric ceramics with CuO addition was investigated. The CuO addition significantly promoted the densification and reduced the sintering temperature of PZTN 95/5 ceramics by more than 200°C. The 0.2 wt% CuO‐added sample sintered at 1150°C exhibited the optimum relative density of 96.7% and excellent electric properties with values of Pr = 37.80 μC/cm2, TC = 223°C, εr = 329, and tan δ = 0.016, which were superior to that of PZTN 95/5 ceramics sintered at 1350°C. 相似文献
995.
Yu Gu Yang Cao Huijuan Chi Qing Liang Yongji Zhang Youyi Sun 《International journal of molecular sciences》2013,14(7):14204-14213
The FeCo/Fe3O4 nanocomposite was synthesized using the hydrothermal approach, in which the FeCo alloy and Fe3O4 are formed by one step. The structure of the FeCo/Fe3O4 nanocomposite was characterized by means of Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray energy-dispersive spectrometer spectroscopy (EDX). They show that the mass ratio of FeCo/Fe3O4 strongly depends on the reaction temperature. Such various architectures follow a stepwise growth mechanism of the composites prepared in various reaction temperatures were also discussed. It indicates that this strategy is facile, effective and controllable for the synthesis of FeCo/Fe3O4 by the one-step method. Furthermore, the magnetic and wave-absorbing properties of the nanocomposites with various structures were investigated in detail. The results show that the FeCo/Fe3O4 with higher mass ratio has higher magnetic properties. Moreover, the FeCo/Fe3O4 nanocomposite shows high wave-absorbing properties (e.g., −37.9 dB), which are expected to apply in microwave absorbing materials. 相似文献
996.
Gaoyuan Ge Hengfang Wu Fei Xiong Yu Zhang Zhirui Guo Zhiping Bian Jindan Xu Chunrong Gu Ning Gu Xiangjian Chen Di Yang 《Nanoscale research letters》2013,8(1):215
One major obstacle for successful application of nanoparticles in medicine is its potential nanotoxicity on the environment and human health. In this study, we evaluated the cytotoxicity effect of dimercaptosuccinic acid-coated iron oxide (DMSA-Fe2O3) using cultured human aortic endothelial cells (HAECs). Our results showed that DMSA-Fe2O3 in the culture medium could be absorbed into HAECs, and dispersed in the cytoplasm. The cytotoxicity effect of DMSA-Fe2O3 on HAECs was dose-dependent, and the concentrations no more than 0.02 mg/ml had little toxic effect which were revealed by tetrazolium dye assay. Meanwhile, the cell injury biomarker, lactate dehydrogenase, was not significantly higher than that from control cells (without DMSA-Fe2O3). However, the endocrine function for endothelin-1 and prostacyclin I-2, as well as the urea transporter function, was altered even without obvious evidence of cell injury in this context. We also showed by real-time PCR analysis that DMSA-Fe2O3 exposure resulted in differential effects on the expressions of pro- and anti-apoptosis genes of HAECs. Meanwhile, it was noted that DMSA-Fe2O3 exposure could activate the expression of genes related to oxidative stress and adhesion molecules, which suggested that inflammatory response might be evoked. Moreover, we demonstrated by in vitro endothelial tube formation that even a small amount of DMSA-Fe2O3 (0.01 and 0.02 mg/ml) could inhibit angiogenesis by the HAECs. Altogether, these results indicate that DMSA-Fe2O3 have some cytotoxicity that may cause side effects on normal endothelial cells. 相似文献
997.
998.
以AAS法测定空气中锌为例,应用数理统计学中最小二乘法建立回归方程,在回归方程基础上建立数学模型,针对整个分析过程找出不确定度的来源,并加以评定分析。 相似文献
999.
:研究了气泡在毛细管端形成的基本规律 ,对于半径较小的毛细管 ,理论计算与实验结果是基本一致的。借助于高速摄像机进行液下气泡法检漏可以定量测出泄漏率 ,实验结果具有较好的重复性。探讨了介质物性、试验压力、加载方式等对气泡形成的影响 相似文献
1000.
过氧酸和DMD的性能及其在纸浆漂白中的应用 总被引:1,自引:0,他引:1
过氧酸和二氧环丙酮是类强的亲电氧化试剂 ,在反应中可有效转移氧原子。文章综述了这类氧化剂的性能及在纸浆漂白中的作用 ,作为可替代传统氯气漂白的最有希望的无污染漂剂 ,采用过氧酸和二氧环丙酮可实现纸浆的全无氯漂白 相似文献