全文获取类型
收费全文 | 23833篇 |
免费 | 2931篇 |
国内免费 | 1898篇 |
专业分类
电工技术 | 1748篇 |
技术理论 | 6篇 |
综合类 | 2053篇 |
化学工业 | 2491篇 |
金属工艺 | 1280篇 |
机械仪表 | 1762篇 |
建筑科学 | 3686篇 |
矿业工程 | 1565篇 |
能源动力 | 733篇 |
轻工业 | 678篇 |
水利工程 | 1081篇 |
石油天然气 | 1479篇 |
武器工业 | 186篇 |
无线电 | 1675篇 |
一般工业技术 | 2252篇 |
冶金工业 | 1319篇 |
原子能技术 | 194篇 |
自动化技术 | 4474篇 |
出版年
2024年 | 77篇 |
2023年 | 276篇 |
2022年 | 553篇 |
2021年 | 674篇 |
2020年 | 777篇 |
2019年 | 649篇 |
2018年 | 561篇 |
2017年 | 787篇 |
2016年 | 943篇 |
2015年 | 1039篇 |
2014年 | 1771篇 |
2013年 | 1441篇 |
2012年 | 1992篇 |
2011年 | 2011篇 |
2010年 | 1600篇 |
2009年 | 1666篇 |
2008年 | 1452篇 |
2007年 | 1741篇 |
2006年 | 1495篇 |
2005年 | 1170篇 |
2004年 | 983篇 |
2003年 | 860篇 |
2002年 | 744篇 |
2001年 | 681篇 |
2000年 | 525篇 |
1999年 | 434篇 |
1998年 | 331篇 |
1997年 | 270篇 |
1996年 | 208篇 |
1995年 | 207篇 |
1994年 | 152篇 |
1993年 | 92篇 |
1992年 | 74篇 |
1991年 | 57篇 |
1990年 | 63篇 |
1989年 | 40篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 17篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1964年 | 12篇 |
1958年 | 7篇 |
1957年 | 11篇 |
1956年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
961.
MARIO BUNGE 《国际通用系统杂志》2013,42(3):181-182
Van Rootselaar criticizes some points in my theory of things for being allegedly trivial, others for being mistaken. While some results are indeed mathematically trivial they are not so philosophically. As for the mistakes, some arc undoubtedly there, most can be corrected easily, and others require changes that have been introduced in the final version of the theory. The rest arc not mistakes but misunderstandings, perhaps unavoidable given the brevity of the original paper. 相似文献
962.
本文结合温福铁路昆阳特大桥主跨钻孔灌注桩施工,介绍了大直径、深孔钻孔桩的施工方法,主要从钻孔、清孔、钢筋笼制安、水下混凝土灌注等几个方面进行了论述。 相似文献
963.
The current investigation examines suitability of the hydraulic analog for analysis of fire-induced dispersion within a complex enclosure. This analog has been implemented using salt-water modeling and planar laser induced fluorescence (PLIF) diagnostics providing quantitative visualization of simulated fire-induced flows. The non-intrusive PLIF diagnostics are used to temporally and spatially characterize dispersion from a buoyant source within a 1/7th scale room–corridor–room enclosure. This configuration is geometrically similar to a full-scale fire test facility, where local fire conditions were characterized near five ionization type smoke detectors placed throughout the enclosure. The full-scale fire and salt-water model results were scaled according to the dimensionless fundamental equations that govern source dispersion.An evaluation of the local conditions and dispersive event times for both the systems was used to explore the ability of the hydraulic analog to predict smoke detector response times. The dispersive event (front arrival) times predicted by the salt-water model, which represents a necessary event for detector activation, were in excellent agreement with the fire test data. A methodology using these front arrival times along with local conditions at the detector location is introduced in this paper. However, the complex nature of detector response and fidelity limitations of the analog make precise predictions of detector response time challenging. The predicted dimensionless response times were within 25% for all detector locations, with the exception of the first-room ceiling detector location. For this latter, a shorter dimensionless response time by less than 40% of that in the actual fire was predicted. 相似文献
964.
965.
概述了出口巴西大跨越输电导线用超高强度钢绞线的生产,通过生产工艺的控制、原材料的选用及设备的购置,所生产的产品完全满足工程技术条件要求。 相似文献
966.
本文以海峡国际会展中心景观设计为例,探讨如何通过延伸城市空间机理与职能、与建筑空间形态密接、合理组织交通活动与停留空间、有机融合自然景观等方式,实现大型公建入口外部空间与城市空间的景观一体化设计。 相似文献
967.
Dr Inayat B. Pathan Mr Santosh J. Munde Dr Santosh Shelke Professor Wahid Ambekar Dr C. Mallikarjuna Setty 《国际聚合物材料杂志》2019,68(4):165-174
The objective of the present investigation was to formulate curcumin loaded fish scale collagen (FSC)-hydroxypropyl methyl cellulose (HPMC K100) nanogel (CNG) for wound healing application. The curcumin nanoemulsion was prepared, characterized and loaded in FSC-HPMC nanogel. The nanogel was evaluated for ex-vivo permeation, in-vivo, skin irritation, and stability study. Ex-vivo permeation study demonstrated that CNG prolonged release and exhibited higher percent contraction value of wound compared to other formulations. In skin irritation study, formulation produced the score of less than 2 compared to control. It concluded that curcumin loaded FSC-HPMC nanogel could be prepared for wound healing applications. 相似文献
968.
Rice straw is a promising renewable energy source because it is abundantly available in Asia. This study conducted a case study of logistics cost analysis for rice straw pellets by considering all stages in the supply chain to define the main factors affecting the selling price of rice straw pellets: collection (job-commission or employment of part-time workers), transportation, storage (vinyl greenhouses or storage buildings with larger capacity), pelletizing, and delivery to users with biomass boilers. The selling price was found to be strongly dependent on the production capacity because the investment cost for the pellet production facility had a significant effect of economies of scale. A production capacity of larger than 1500 t y−1 is required for rice straw pellets to compete with wood pellets and fossil fuels in the studied Japanese context if the subsidy rate for the investment is 50%, part-time workers conduct the collection, and rice straw is stored in the storage buildings. Our sensitivity analysis also showed an economically feasible spatial scale: for example, rice straw should be collected within a 20 km radius and the users should be within a 38 km radius when the production capacity is 1500 t y−1. In addition, other critical factors related to the collection of rice straw from the paddy fields and transportation of rice straw rolls to storage were identified as planning factors to further reduce the total logistics cost of rice straw pellets. 相似文献
969.
Factory management plays an important role in improving the productivity and quality of service in the production process. In particular, the distributed permutation flow shop scheduling problem with multiple factories is considered a priority factor in the factory automation. This study proposes a novel model of the developed distributed scheduling by supplementing the reentrant characteristic into the model of distributed reentrant permutation flow shop (DRPFS) scheduling. This problem is described as a given set of jobs with a number of reentrant layers is processed in the factories, which compromises a set of machines, with the same properties. The aim of the study is to determine the number of factory needs to be used, jobs assignment to certain factory and sequence of job assigned to the factory in order to simultaneously satisfy three objectives of minimizing makespan, total cost and average tardiness. To do this, a novel multi-objective adaptive large neighborhood search (MOALNS) algorithm is developed for finding the near optimal solutions based on the Pareto front. Various destroy and repair operators are presented to balance between intensification and diversification of searching process. The numerical examples of computational experiments are carried out to validate the proposed model. The analytical results on the performance of proposed algorithm are checked and compared with the existing methods to validate the effectiveness and robustness of the proposed potential algorithm in handling the DRPFS problem. 相似文献
970.
This work presents a varying trend of impact ignition threshold denoted by minimum impact velocity to trigger an ignition when the scale of the explosive changes. The effects of explosive scale factors on impact-induced reaction degree were investigated using Steven tests and numerical simulation for polymer-bonded explosive-C03 (a cyclotetramethylene tetranitramine [HMX]-based explosive) impacted by projectiles of various velocities. Two scale factors—that is, axial thickness and radius—were studied through various scale samples including Φ98 mm × 13 mm, Φ98 mm × 39 mm, Φ140 mm × 13 mm, and Φ140 mm × 39 mm. The velocities of projectiles and the impact and ignition processes were analyzed using a high-speed camera. The pressure histories were measured by embedded manganin pressure gauges and poly vinylidene fluoride stress gauges. The reaction overpressures of the explosive were obtained by blast pressure gauges to evaluate the reaction degree. The effects of explosive scale factor on reaction degree and characteristics under mild impact were summarized. In a certain range (larger than the diameter of the impact projectile), different sample diameters do not influence the velocity threshold, but the thickness of the samples does; that is, the velocity threshold increases with the thickness of the sample. The study also indicates that the ignition and explosion in Steven tests are mainly triggered by the overlapping of direct impact and reflected stress waves. Our numerical simulations results of pressure and ignition times are consistent with the experimental data. The obtained knowledge can be used to evaluate the safety of different scale HMX-based explosives under accidental impact or falls. 相似文献