全文获取类型
收费全文 | 352351篇 |
免费 | 24356篇 |
国内免费 | 13105篇 |
专业分类
电工技术 | 18282篇 |
技术理论 | 56篇 |
综合类 | 19731篇 |
化学工业 | 58643篇 |
金属工艺 | 20243篇 |
机械仪表 | 21969篇 |
建筑科学 | 26116篇 |
矿业工程 | 10996篇 |
能源动力 | 10435篇 |
轻工业 | 19589篇 |
水利工程 | 5373篇 |
石油天然气 | 23275篇 |
武器工业 | 2604篇 |
无线电 | 39048篇 |
一般工业技术 | 44990篇 |
冶金工业 | 21748篇 |
原子能技术 | 3447篇 |
自动化技术 | 43267篇 |
出版年
2024年 | 1293篇 |
2023年 | 5250篇 |
2022年 | 8963篇 |
2021年 | 12671篇 |
2020年 | 9919篇 |
2019年 | 8178篇 |
2018年 | 9510篇 |
2017年 | 10666篇 |
2016年 | 9607篇 |
2015年 | 12490篇 |
2014年 | 16284篇 |
2013年 | 20372篇 |
2012年 | 20846篇 |
2011年 | 23558篇 |
2010年 | 20074篇 |
2009年 | 19360篇 |
2008年 | 18999篇 |
2007年 | 18395篇 |
2006年 | 19190篇 |
2005年 | 16995篇 |
2004年 | 11048篇 |
2003年 | 9779篇 |
2002年 | 8766篇 |
2001年 | 8078篇 |
2000年 | 8594篇 |
1999年 | 10279篇 |
1998年 | 9463篇 |
1997年 | 7705篇 |
1996年 | 7172篇 |
1995年 | 5834篇 |
1994年 | 4788篇 |
1993年 | 3419篇 |
1992年 | 2707篇 |
1991年 | 2201篇 |
1990年 | 1650篇 |
1989年 | 1396篇 |
1988年 | 1130篇 |
1987年 | 763篇 |
1986年 | 592篇 |
1985年 | 398篇 |
1984年 | 277篇 |
1983年 | 234篇 |
1982年 | 219篇 |
1981年 | 158篇 |
1980年 | 145篇 |
1979年 | 75篇 |
1978年 | 41篇 |
1977年 | 46篇 |
1976年 | 74篇 |
1975年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
印染废水处理工艺研究及实例 总被引:1,自引:0,他引:1
本文简要介绍了印染废水水质特征,提出了处理工艺,并利用两个工程实例说明了该工艺的可行性. 相似文献
32.
33.
氩等离子体辐照反相乳液接枝改性涤纶织物的研究 总被引:1,自引:0,他引:1
首次提出了在等离子体辐照后再用反相乳液接枝改性涤纶织物的新方法,探讨了接枝颗粒特征以及织物各项物理力学性能.接枝织物的结构及性能的测试结果表明:接枝物的尺寸远小于纤维的直径,在提高织物吸湿性的同时,对织物透气性能和强力等无明显影响;实验也证实了乳液中未接枝单体可以再次聚合. 相似文献
34.
针对烧结厂烧结电除尘灰的工况特性,介绍了输送烧结电除尘灰的正压气力输灰系统的特点、组成,还对在调试和试运行过程中遇到的故障进行了分析并制订了解决措施。 相似文献
35.
Xiaojun Xie Yonghong Cheng Hong Wang Qian Wang Xiaolin Chen Caixin Sun 《Ceramics International》2008,34(4):689-693
In the ideal A2B2O6O′ pyrochlore structure, the x-value of O atom position is a variable parameter. In Bi1.5ZnNb1.5−xTaxO7 (BZNT) cubic pyrochlores, the x-values alter with the different compositions of Nb/Ta. In this work, a series of initial models for BZNT were established by analyzing X-ray diffraction data. Then three structure modifying methods, including Rietveld refinement, Rietveld refinement with energy and geometry optimization based on quantum mechanics, were employed to obtain the precise models using Materials Studio. Moreover, the reflectivities of BZNT were computed by quantum mechanical simulation based on the refined models. Comparing the simulation results from different modifying models with the experimental results, it is found that Rietveld refinement with energy optimization is the most accurate method for BZNT pyrochlores. According to the simulation results, the different reflectivities correspond well with various x-values of O atom positions in BZNT pyrochlores. 相似文献
36.
37.
干凝胶作为一种新型的轻质多孔材料在工业生产和人们的生活中具有广泛的应用,但是其较低的强度和易碎裂的特点却限制了其实际应用.结合干凝胶的制备过程,总结了几种有效的降低结构破坏的途径,并对其机理做了简要分析,最后对干凝胶的应用前景做了展望. 相似文献
38.
39.
Lei Liu Ying Kong Hong Xu Jin P. Li Jin X. Dong Zhi Lin 《Microporous and mesoporous materials》2008,115(3):624-628
A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO4-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P2O5-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO4-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO4-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn3(PO4)2 · 4H2O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO4-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C). 相似文献
40.
A new torque estimator for switched reluctance motor (SRM) drives based on 2-D rotary regression analysis is presented in this paper. The proposed torque estimator is composed of a bicubic regressive polynomial as a function of rotor position and input current. The regressive coefficients can be computed offline or online from the torque characteristics acquired either experimentally or from numerical computation. Furthermore, a torque estimation method by taking mutual coupling into consideration is proposed. It can be seen that the estimated and experimentally obtained self-coupling and mutual-coupling torque characteristics are in good agreement with each other. In addition, the dynamic torque waveforms with and without the mutual coupling, estimated by the proposed estimator, are found to be virtually the same as those obtained from the bicubic spline interpolation for SRM drives with single-pulse voltage, hysteresis current chopping, as well as with voltage pulse width modulation control. The success of all the case studies being reported is a good validation of the usefulness and accuracy of the proposed real-time torque estimator that, as described in this paper, can be used to quickly estimate the instantaneous output torque of SRM drives. 相似文献