全文获取类型
收费全文 | 59601篇 |
免费 | 6177篇 |
国内免费 | 3552篇 |
专业分类
电工技术 | 1775篇 |
技术理论 | 1篇 |
综合类 | 4632篇 |
化学工业 | 10980篇 |
金属工艺 | 6306篇 |
机械仪表 | 6065篇 |
建筑科学 | 3805篇 |
矿业工程 | 2105篇 |
能源动力 | 1570篇 |
轻工业 | 8113篇 |
水利工程 | 1612篇 |
石油天然气 | 2072篇 |
武器工业 | 549篇 |
无线电 | 4545篇 |
一般工业技术 | 8270篇 |
冶金工业 | 2304篇 |
原子能技术 | 559篇 |
自动化技术 | 4067篇 |
出版年
2024年 | 364篇 |
2023年 | 1147篇 |
2022年 | 1640篇 |
2021年 | 1977篇 |
2020年 | 2275篇 |
2019年 | 2045篇 |
2018年 | 2086篇 |
2017年 | 2434篇 |
2016年 | 2436篇 |
2015年 | 2534篇 |
2014年 | 3344篇 |
2013年 | 4235篇 |
2012年 | 4344篇 |
2011年 | 4483篇 |
2010年 | 3124篇 |
2009年 | 3153篇 |
2008年 | 2930篇 |
2007年 | 3649篇 |
2006年 | 3333篇 |
2005年 | 2755篇 |
2004年 | 2267篇 |
2003年 | 1909篇 |
2002年 | 1734篇 |
2001年 | 1401篇 |
2000年 | 1299篇 |
1999年 | 1080篇 |
1998年 | 871篇 |
1997年 | 806篇 |
1996年 | 711篇 |
1995年 | 532篇 |
1994年 | 478篇 |
1993年 | 396篇 |
1992年 | 323篇 |
1991年 | 215篇 |
1990年 | 232篇 |
1989年 | 165篇 |
1988年 | 148篇 |
1987年 | 72篇 |
1986年 | 87篇 |
1985年 | 69篇 |
1984年 | 62篇 |
1983年 | 47篇 |
1982年 | 48篇 |
1981年 | 13篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1964年 | 5篇 |
1961年 | 4篇 |
1959年 | 8篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
31.
Application of high‐temperature Fenton oxidation for the treatment of sulfonation plant wastewater
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
32.
针对反射面成型的复杂影响因素,提出平面桁架构建的定日镜面形支撑结构优化技术路线. 利用模拟仿真、数值计算和优化算法等方法,解析20 m2定日镜面形定义技术路线的4个组成环节:面形规格及宽高比、上弦杆的截面矩、平面桁架组间距的最优值、机加工中工艺控制要点的量化. 试制小型定日镜进行实验,分析光斑形状和能流密度分布特性,并与理想球面形光斑比较,两者的拟合优度大于0.98. 实验结果表明,当反射镜宽高比取1.2,上弦杆截面矩取40 000 mm4,桁架组间距取950 mm,上弦杆和斜杆的开孔公差小于0.9 mm时,反射面形的质量提升. 研究从原理和实践上证明了该优化技术路线的可行性. 相似文献
33.
Alfredo M. Gravagnuolo Eden Morales‐Narváez Charlene Regina Santos Matos Sara Longobardi Paola Giardina Arben Merkoçi 《Advanced functional materials》2015,25(38):6084-6092
Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications. 相似文献
34.
35.
In this article, we study a linear array of bowtie nanoantennas placed between two metallic strips that can work from 800 to 1420 nm (600 nm linewidth), with an electric field enhancement factor close to 20. We study the dynamical change of the position of the electric field enhancement amongst different elements in the array and, at the same time, the effects of dispersion on the scalability of the array elements. A systematic analysis and methodology to produce an array that can operate over a large bandwidth whilst maintaining the electric field enhancement without significant variation is provided. 相似文献
36.
Defects are often present in rolled products, such as wire rod. The market demand for wire rod without any defects has increased. In the final wire rod products, defects originating from steel making, casting, pre‐rolling of billets and during wire rod rolling can appear. In this work, artificial V‐shaped longitudinal surface cracks have been analysed experimentally and by means of FEM. The results indicate that the experiments and FEM calculations show the same tendency except in two cases, where instability due to fairly “round” false round bars disturbed the experiment. FE studies in combination with practical experiments are necessary in order to understand the behaviour of the material flows in the groove and to explain whether the crack will open up as a V‐shape or if it will be closed as an I‐shape. 相似文献
37.
Beneficial effects of wettability altering surfactants in oil-wet fractured reservoirs 总被引:3,自引:0,他引:3
Subhash C. Ayirala Chandra S. Vijapurapu Dandina N. Rao 《Journal of Petroleum Science and Engineering》2006,52(1-4):261
In fractured reservoirs, an effective matrix-fracture mass transfer is required for oil recovery. Surfactants have long been considered for oil recovery enhancement, mainly in terms of their ability to reduce oil–water interfacial tension. These surfactants are effective when the fractured formations are water-wet, where capillary imbibition of surfactants from the fracture into the matrix contributes to oil recovery. However, another beneficial aspect of surfactants, namely their ability to alter wettability, remains to be explored and exploited. Surfactants capable of altering wettability can be especially beneficial in oil-wet fractured formations, where the surfactant in the fracture diffuses into the matrix and alters the wettability, enabling imbibition of even more surfactant into the matrix. This sequential process of initial diffusion followed by imbibition continues well into the matrix yielding significant enhancements in oil recovery.In order to test this hypothesis of sequential diffusion–imbibition phenomenon, Dual-Drop Dual-Crystal (DDDC) contact angle experiments have been conducted using fractured Yates dolomite reservoir fluids, two types of surfactants (nonionic and anionic) and dolomite rock substrates. A new experimental procedure was developed in which crude oil equilibrated with reservoir brine has been exposed to surfactant to simulate the matrix-fracture interactions in fractured reservoirs. This procedure enables the measurements of dynamic contact angles and oil–water interfacial tensions, in addition to providing the visual observations of the dynamic behavior of crude oil trapped in the rock matrix as it encounters the diffusing surfactant from the fractures. Both the measurements and visual observations indicate wettability alterations of the matrix surface from oil-wet to less oil-wet or intermediate wet by the surfactants. Thus this study is of practical importance to oil-wet fractured formations where surfactant-induced wettability alterations can result in significant oil recovery enhancements. In addition, this study has also identified the need to include contact angle term in the dimensionless Bond number formulations for better quantitative interpretation of rock–fluids interactions. 相似文献
38.
An optoelectronic method is considered for noncontacting reconstruction of the surface profile of three-dimensional objects of large dimensions. The optimal conditions for performing measurements are identified. It is shown that the proposed method, in contrast to the already known methods, does not require fine tuning of the equipment. A numerical method is given for compensating distortions caused by aberrations. A method is described for reconstructing the surface profile cell by cell which increases the accuracy of measurements. 相似文献
39.
Yu Zhao Zhigang Xu Zongshi Li Weihong Qiao Lubai Cheng 《Petroleum Science and Technology》2006,24(7):821-827
Heavy alkyl benzene sulfonates (HABS) were synthesized, and their interfacial tensions were measured and compared with those of petroleum sulfonates ORS-41. Effects of their coupling with lignosulfonate were also studied. The results showed that HABS exhibited good interfacial activities and the system of HABS blending with LS displayed better interfacial activities than ORS-41 and therefore reduced the prime cost. Their best proportions of synergism were from 3:1 to 4:1. HABS might be a more promising alkali-surfactant-polymer (ASP) flooding agent. 相似文献
40.
基于对比折射法的三维静校正技术及其应用 总被引:7,自引:0,他引:7
在地形起伏剧烈、速度和厚度横向变化大的地区,折射静校正技术的应用受到诸多限制,主要表现在不能准确地识别和拾取来自于地下连续地质界面的折射波,使得精确求取的长波长静校正量困难。为此,提出了一种基于对比折射法的三维静校正技术。介绍了这种静校正技术的方法原理和特点,基于对比折射法的折射波至拾取实质上是一个折射层的对比分析解释过程,因此能准确地拾取折射波至,精确地求解低速带的绝对延迟时;然后利用延迟时和近地表速度模型(等效,时深,空变)反演表层模型,最终一次性完成基准面静校正(包含低速带校正和高程校正)。在黄土塬、沙漠以及沙漠和山地的接合部等地区,利用基于对比折射法的三维静校正技术进行静校正处理,使资料的品质得到了明显改善,反射同相轴连续性好,信噪比和分辨率高,构造形态清晰可靠,提高了勘探精度。 相似文献