全文获取类型
收费全文 | 44973篇 |
免费 | 4371篇 |
国内免费 | 2338篇 |
专业分类
电工技术 | 3216篇 |
技术理论 | 2篇 |
综合类 | 3455篇 |
化学工业 | 6688篇 |
金属工艺 | 2427篇 |
机械仪表 | 2707篇 |
建筑科学 | 3422篇 |
矿业工程 | 1233篇 |
能源动力 | 1158篇 |
轻工业 | 3713篇 |
水利工程 | 829篇 |
石油天然气 | 2232篇 |
武器工业 | 462篇 |
无线电 | 5187篇 |
一般工业技术 | 4459篇 |
冶金工业 | 3845篇 |
原子能技术 | 758篇 |
自动化技术 | 5889篇 |
出版年
2024年 | 256篇 |
2023年 | 823篇 |
2022年 | 1714篇 |
2021年 | 2178篇 |
2020年 | 1680篇 |
2019年 | 1355篇 |
2018年 | 1472篇 |
2017年 | 1569篇 |
2016年 | 1419篇 |
2015年 | 1862篇 |
2014年 | 2317篇 |
2013年 | 2556篇 |
2012年 | 2903篇 |
2011年 | 3010篇 |
2010年 | 2728篇 |
2009年 | 2620篇 |
2008年 | 2621篇 |
2007年 | 2423篇 |
2006年 | 2365篇 |
2005年 | 2020篇 |
2004年 | 1352篇 |
2003年 | 1258篇 |
2002年 | 1335篇 |
2001年 | 1191篇 |
2000年 | 947篇 |
1999年 | 872篇 |
1998年 | 1147篇 |
1997年 | 821篇 |
1996年 | 678篇 |
1995年 | 423篇 |
1994年 | 389篇 |
1993年 | 342篇 |
1992年 | 204篇 |
1991年 | 131篇 |
1990年 | 108篇 |
1989年 | 99篇 |
1988年 | 89篇 |
1987年 | 53篇 |
1986年 | 43篇 |
1985年 | 31篇 |
1984年 | 18篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 28篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 43篇 |
1976年 | 109篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Xingliang Chen Xingwei Wang Lindong Li Shuhua Qi 《Journal of Materials Science: Materials in Electronics》2016,27(6):5607-5612
Electric conductive and microwave absorbing material PANI/Ni/CF was prepared by in situ polymerization of polyaniline on the surface of nickel-coated carbon fiber (Ni/CF). The morphologies and structures of CF, Ni/CF, PANI and PANI/Ni/CF were characterized by scanning electron microscope and X-ray diffraction. Results show that the CF was wrapped tightly around the nickel layer, and the Ni/CF was coated by PANI. Measurement of four probes resistance tester indicates that the electrical conductivity of PANI/Ni/CF was great improved compared with PANI and PANI/CF. Vibrating sample magnetometry shows that the magnetic saturation intensity of Ni/CF and PANI/Ni/CF was 13.8 and 2.3 emu/g, respectively. According to the vector network analyzer, the microwave absorbing properties of PANI/Ni/CF were better than those of PANI and PANI/CF, and its minimum loss value is ?12.4 dB at 8.8 GHz. 相似文献
53.
Zixuan Wang Dongzhao Hao Yuefei Wang Jinwu Zhao Jiaxing Zhang Xi Rong Jiaojiao Zhang Jiwei Min Wei Qi Rongxin Su Mingxia He 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(1):2204959
The self-assembly of peptidyl virus-like nanovesicles (pVLNs) composed of highly ordered peptide bilayer membranes that encapsulate the small interfering RNA (siRNA) is reported. The targeting and enzyme-responsive sequences on the bilayer's surface allow the pVLNs to enter cancer cells with high efficiency and control the release of genetic drugs in response to the subcellular environment. By transforming its structure in response to the highly expressed enzyme matrix metalloproteinase 7 (MMP-7) in cancer cells, it helps the siRNA escape from the lysosomes, resulting in a final silencing efficiency of 92%. Moreover, the pVLNs can serve as reconfigurable “Trojan horse” by transforming into membranes triggered by the MMP-7 and disrupting the cytoplasmic structure, thereby achieving synergistic anticancer effects and 96% cancer cell mortality with little damage to normal cells. The pVLNs benefit from their biocompatibility, targeting, and enzyme responsiveness, making them a promising platform for gene therapy and anticancer therapy. 相似文献
55.
李琦 《数码设计:surface》2010,(1):125-127
博物馆建筑,是一个城市文化的象征,如何使博物馆具有文化感,体现传统的审美文化,又具有新的设计元素,引导人类审美意识,苏州博物馆与宁波博物馆做了比较好的探索。 相似文献
56.
提出一种以词性为参考值的文本挖掘算法,能有效挖掘与种子词有关的关联规则。基于Bootstrapping算法思想,既减少了预处理阶段对于词根还原的依赖,能处理日志中出现的中文词汇。增加了对于日志文本上下的理解,提高了关联规则的有效性,并应用与IDS日志挖掘之中,有效改善挖掘效率,为规则库提供关联规则。 相似文献
57.
Bin Li Hong-Wei Wang Jian-Bo Yang Min Guo Chao Qi 《Expert systems with applications》2011,38(12):14997-15008
This paper is devoted to investigating inventory control problems under nonstationary and uncertain demand. A belief-rule-based inventory control (BRB-IC) method is developed, which can be applied in situations where demand and demand-forecast-error (DFE) do not follow certain stochastic distribution and forecasting demand is given in single-point or interval styles. The method can assist decision-making through a belief-rule structure that can be constructed, initialized and adjusted using both manager’s knowledge and operational data. An extended optimal base stock (EOBS) policy is proved for initializing the belief-rule-base (BRB), and a BRB-IC inference approach with interval inputs is proposed. A numerical example and a case study are examined to demonstrate potential applications of the BRB-IC method. These studies show that the belief-rule-based expert system is flexible and valid for inventory control. The case study also shows that the BRB-IC method can compensate DFE by training BRB using historical demand data for generating reliable ordering policy. 相似文献
58.
Visual media data such as an image is the raw data representation for many important applications. Reducing the dimensionality of raw visual media data is desirable since high dimensionality degrades not only the effectiveness but also the efficiency of visual recognition algorithms. We present a comparative study on spatial interest pixels (SIPs), including eight-way (a novel SIP detector), Harris, and Lucas‐Kanade, whose extraction is considered as an important step in reducing the dimensionality of visual media data. With extensive case studies, we have shown the usefulness of SIPs as low-level features of visual media data. A class-preserving dimension reduction algorithm (using GSVD) is applied to further reduce the dimension of feature vectors based on SIPs. The experiments showed its superiority over PCA.
相似文献
Chandra KambhamettuEmail: |
59.
60.
Perthes' disease treated by prolonged recumbency and femoral head containment: a long-term appraisal
The results of a long-term review of 102 hips in eighty-seven patients with Perthes' disease are described, the mean follow-up interval being seventeen years. All had been treated by an extremely rigorous conservative regime in which the patients were kept in hospital for an average period of twenty-six months, during which time they were confined to bed with the legs in wide abduction, first in traction and later in "broomstick" plasters to ensure "containment" of the femoral head. The patients were assessed by the joint clincial and radiological method described by Ratliff (1956). The results were very satisfactory, with only 2 per cent poor results and 10 per cent fair. The remaining 88 per cent were good. The radiological results at the end of treatment have also been compared with control series described by Catterall (1972) and with the osteotomy series of Lloyd-Roberts, Catterall and Salamon (1976). From this it appears that the described regime offers no benefit compared with the natural history in Catterall's Groups I and II, and in Group III the results were only marginally better than those following osteotomy. In Group IV cases, however, where the femoral head was totally involved, the benefit was important, and since these are the cases which carry the worst natural prognosis it is suggested that the use of the method described in such instances must be seriously considered in spite of its social disadvantages. The theoretical implications of the findings are considered, and it is concluded that the benefits of the method cannot be ascribed wholly to the application of the "containment" principle. 相似文献