全文获取类型
收费全文 | 434800篇 |
免费 | 42912篇 |
国内免费 | 18512篇 |
专业分类
电工技术 | 24480篇 |
技术理论 | 47篇 |
综合类 | 29272篇 |
化学工业 | 80982篇 |
金属工艺 | 23438篇 |
机械仪表 | 25627篇 |
建筑科学 | 33235篇 |
矿业工程 | 12993篇 |
能源动力 | 11803篇 |
轻工业 | 33873篇 |
水利工程 | 7977篇 |
石油天然气 | 25514篇 |
武器工业 | 3124篇 |
无线电 | 49579篇 |
一般工业技术 | 53166篇 |
冶金工业 | 20806篇 |
原子能技术 | 4211篇 |
自动化技术 | 56097篇 |
出版年
2024年 | 1670篇 |
2023年 | 6280篇 |
2022年 | 11152篇 |
2021年 | 15771篇 |
2020年 | 12918篇 |
2019年 | 12300篇 |
2018年 | 13676篇 |
2017年 | 15363篇 |
2016年 | 14599篇 |
2015年 | 19024篇 |
2014年 | 22890篇 |
2013年 | 27789篇 |
2012年 | 27628篇 |
2011年 | 29939篇 |
2010年 | 27187篇 |
2009年 | 25651篇 |
2008年 | 24858篇 |
2007年 | 23631篇 |
2006年 | 23670篇 |
2005年 | 20685篇 |
2004年 | 14772篇 |
2003年 | 14027篇 |
2002年 | 14043篇 |
2001年 | 12342篇 |
2000年 | 11051篇 |
1999年 | 10801篇 |
1998年 | 7774篇 |
1997年 | 6685篇 |
1996年 | 6309篇 |
1995年 | 5175篇 |
1994年 | 4225篇 |
1993年 | 2852篇 |
1992年 | 2267篇 |
1991年 | 1695篇 |
1990年 | 1337篇 |
1989年 | 1074篇 |
1988年 | 889篇 |
1987年 | 558篇 |
1986年 | 448篇 |
1985年 | 289篇 |
1984年 | 224篇 |
1983年 | 177篇 |
1982年 | 135篇 |
1981年 | 83篇 |
1980年 | 107篇 |
1979年 | 49篇 |
1978年 | 18篇 |
1977年 | 24篇 |
1976年 | 28篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
H. Fan A. Wright J. Gabaldon A. Rodriguez C.J. Brinker Y.‐B. Jiang 《Advanced functional materials》2006,16(7)
The synthesis of three‐dimensionally ordered, transparent gold‐nanocrystal (NC)/silica superlattice thin films using the self‐assembly (by spin‐coating) of water‐soluble gold nanocrystal micelles and soluble silica is reported by Fan and co‐workers on p. 891. The robust, 3D NC/silica superlattice films are of interest for the development of collective optical and electronic phenomena, and, importantly, for the integration of NC arrays into device architectures. Nanocrystals and their ordered arrays hold many important applications in fields such as catalysis, surface‐enhanced Raman spectroscopy based sensors, memory storage, and electronic and optical nanodevices. Herein, a simple and general method to synthesize ordered, three‐dimensional, transparent gold nanocrystal/silica superlattice thin films by self‐assembly of gold nanocrystal micelles with silica or organosilsesquioxane by spin‐coating is reported. The self‐assembly process is conducted under acidic sol–gel conditions (ca. pH 2), ensuring spin‐solution homogeneity and stability and facilitating the formation of ordered and transparent gold nanocrystal/silica films. The monodisperse nanocrystals are organized within inorganic host matrices as a face‐centered cubic mesostructure, and characterized by transmission electron spectroscopy and X‐ray diffraction. 相似文献
992.
993.
在社会主义市场经济条件下,朔州市桑干河流域原有的分市县管辖的8处大中型灌区的管理体制和运行机制已不适应水管单位生存发展的需求.从解决长期以来水管单位面临的诸多实际问题出发,按照程序报请各级政府批准后,原分散管理的8处灌区统一划归桑干河水利管理局管理.该改革以理顺关系、设置机构为突破口,建立起了以流域为建制的新型水管体制,在运行过程中不断探索和解决改革中出现的新情况和新问题,有利于维护水资源的可持续利用和生态与环境的协调发展. 相似文献
994.
X.B. Tu B. Jian S.J. Wang H.Y. Bian J. Wang S.G. Li 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2005,20(4):1106
Granite is commonly recognized as an ideal medium for underground construction. However, in the site investigation for Heimifeng Pumped Storage Power Station project, it was found that there are swelling behaviors induced by alteration in granite and eventually causing slaking and disintegration of rock blocks. The study shows that hydrothermal alteration in granite is primarily due to the intrusion of multi-phase igneous magma. The clay minerals, such as montmorillonite, chlorite, kaolinite, are the main causes for the swelling behavior of granite. In the exploratory adits, alteration was observed to occur mainly along faults or fractures in the rock masses and resulted in roof caving if water is present. Some of the highly altered borehole cores swell and crack within 24 h in water and eventually disintegrate completely. From the testing results on the samples, the maximum axial free swelling strain is about 1.2%, while the maximum axial confined swelling strain is around 0.1% with swelling stress less than 25 kPa. Under free swelling tests, 80% of swelling is completed within 24 hours. Under confined swelling condition, swelling process is completed within 1 h for some samples, with 80% of maximum swelling strain finished within around 22 h for most of the samples. Contraction of samples occurs after swelling completed. The strength of granite, reflected by deformation and elastic moduli, shear strength, decreases due to alteration. The deformation and elastic moduli are even lower compared to highly weathered rock. The shear strength is between that for highly weathered and slightly weathered rocks. The swelling characteristics of the altered rock present great challenges for support or lining during construction and operation stages. Support or lining shall be in place immediately after excavation. Since the rock may swell when encountering water, the shotcrete shall be designed accordingly. During the construction of access tunnel and caverns, water shall be drained in time. Drainage directly from surface shall be avoided so as to prevent floor heave. 相似文献
995.
The growth of Li1+xMn2O4 via detonation reaction was investigated with respect to the presence of an energetic precursor, such as the metallic nitrate and the degree of confinement of the explosive charge. The detonation products were characterized by scanning electron microscopy. Powder X-ray diffraction and transmission electron microscopy were used to characterize the products. Li1+xMn2O4 with 1-2 μm spherical morphology and more uniform secondary particles, but with smaller primary particles of diameters from 20 to 60 nm and a variety of morphologies were found. The oxides produced by this cheap method affirmed the validity of detonation synthesis of nano-size powders. 相似文献
996.
The electron spin resonance (ESR) spectra of end‐group spin labelled poly(ethylene oxide) (SLPEO) using 2,2,6,6‐tetramethyl‐piperdine‐1‐oxyl nitroxide and its blends with poly(styrene‐co‐4‐vinylphenol) (STVPhs) of different hydroxyl contents were recorded over a wide temperature range. For a blend of SLPEO and pure polystyrene (PS), the ESR spectrum was composed of a single motion component, indicating that PS was immiscible with PEO. For blends composed of SLPEO and different‐hydroxyl‐content STVPhs, two spectral components with different motion rates were observed over a certain temperature range. The difference between the motion rates should be attributed to micro‐heterogeneity in the blends, with the faster rate corresponding to a nitroxide radical motion trapped in the PEO‐rich domain and the slower rate corresponding to a nitroxide radical motion trapped in the STVPh‐rich domain. Variations in the values of a number of the ESR parameters (Ta, Td and T50G) and the apparent activation energy (Ea) with hydroxyl content in the blends indicated that the miscibility of the blends increased with increasing hydrogen‐bonding density due to specific interactions between the hydroxyl groups in STVPh and the ether oxygens in PEO. Copyright © 2004 Society of Chemical Industry 相似文献
997.
浅谈小型局域网的组建与应用 总被引:1,自引:0,他引:1
李科峰 《网络安全技术与应用》2007,(3):31-32
随着计算机应用技术与通讯技术的发展以及在实践中的广泛应用,智能化和网络化成为必然趋势,局域网的应用可以营造一个现代化的高效、快捷、安全的环境,也可以使计算机以及其他硬件的功能得到充分的发挥。 相似文献
998.
对转炉炼钢实现低铁耗和高碳低磷工艺进行了分析,介绍了南钢公司转炉炼钢实践低铁耗条件下高碳低磷工艺的具体应用措施。 相似文献
999.
强夯法处理大块填石地基的应用实践 总被引:3,自引:0,他引:3
对用大块填石的地基,通过试验,采用合适能量的夯锤进行强夯处理,改变地基结构排列、使其致密,从而提高地基承载力,是一种经济有效的地基处理方法。 相似文献
1000.