全文获取类型
收费全文 | 84920篇 |
免费 | 10259篇 |
国内免费 | 6935篇 |
专业分类
电工技术 | 8199篇 |
技术理论 | 2篇 |
综合类 | 7691篇 |
化学工业 | 10928篇 |
金属工艺 | 5321篇 |
机械仪表 | 5778篇 |
建筑科学 | 6643篇 |
矿业工程 | 3015篇 |
能源动力 | 2417篇 |
轻工业 | 8189篇 |
水利工程 | 2530篇 |
石油天然气 | 3515篇 |
武器工业 | 1143篇 |
无线电 | 10458篇 |
一般工业技术 | 7894篇 |
冶金工业 | 3213篇 |
原子能技术 | 1431篇 |
自动化技术 | 13747篇 |
出版年
2024年 | 544篇 |
2023年 | 1555篇 |
2022年 | 3244篇 |
2021年 | 4413篇 |
2020年 | 3133篇 |
2019年 | 2412篇 |
2018年 | 2510篇 |
2017年 | 2902篇 |
2016年 | 2709篇 |
2015年 | 4100篇 |
2014年 | 4999篇 |
2013年 | 5938篇 |
2012年 | 7147篇 |
2011年 | 7392篇 |
2010年 | 6849篇 |
2009年 | 6652篇 |
2008年 | 6424篇 |
2007年 | 6270篇 |
2006年 | 5579篇 |
2005年 | 4347篇 |
2004年 | 3112篇 |
2003年 | 2080篇 |
2002年 | 2067篇 |
2001年 | 1686篇 |
2000年 | 1363篇 |
1999年 | 736篇 |
1998年 | 383篇 |
1997年 | 288篇 |
1996年 | 263篇 |
1995年 | 226篇 |
1994年 | 162篇 |
1993年 | 96篇 |
1992年 | 95篇 |
1991年 | 73篇 |
1990年 | 59篇 |
1989年 | 45篇 |
1988年 | 29篇 |
1987年 | 18篇 |
1986年 | 23篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 23篇 |
1979年 | 17篇 |
1977年 | 9篇 |
1976年 | 18篇 |
1959年 | 13篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
多关系群体挖掘是近年来快速发展的重要的数据挖掘领域之一.传统的群体挖掘方法是假定网络中只有一种关系,并且挖掘结果与用户需求无关.但现实中的社会网络中存在着多种关系.基于用户查询,不同的关系表现出不同的重要性.分析了多关系群体挖掘中关系提取的问题,提出一种新算法对满足用户期望的关系进行最优线性合并.利用获得的合并关系提高群体挖掘的精准性. 相似文献
82.
Wang Z Zeng F Li H Ye Z Bai Y Xia W Liang B 《Computer methods and programs in biomedicine》2007,86(1):39-44
Evaluation of renal vasculature was necessary for preoperative donor assessment in living donor kidney transplantation, and the ability to view the vascular imaging in three-dimensional (3D) space should be helpful undoubtedly. Considering the widespread use of personal computer (PC) systems, we aimed to find a handy way to display the anatomy of the renal arterial and venous systems of potential donors on PC-Windows platform. Ten living-related donors were included in this study. Serial computed tomography (CT) images were loaded into Amira 3.1 running on a PC with Windows XP. Following image crop, segmentation and 3D reconstruction, we got the 3D images and the video clips. According to the displays which were confirmed by latter intraoperative findings, eight donors had single renal vessels, one had a left accessory renal artery and one had a right accessory renal artery. This project offered a new approach to evaluate the renal vessel anatomy in living donor kidney transplantation, and it was favorable for accuracy and popularizing. 相似文献
83.
The prototype of a CO2 sensor made of CuO–BaTiO3, which has capacitance sensitive effect, is designed based on the pn heterojunctions of CuO and BaTiO3 semiconductors. The preparation of BaTiO3 semiconductor powders is pointed out, using the coprecipitation and semiconducting techniques. The characteristic quantities relating to the capacitance sensitive effect of the sensor are studied systematically with the aid of a gas tester. A reasonable mechanism of the sensor is proposed. 相似文献
84.
85.
水和甲醇存在下MAMS的消失反应动力学研究 总被引:1,自引:0,他引:1
通过实验研究了甲基丙烯酰胺硫酸盐(MAMS)与甲醇、水进行反应的动力学,并对该反应的机理进行了探讨。 相似文献
86.
Due to overvoltage produced by inverter output,inverter-fed motor insulation systems often experience fast electrical aging process,especially when partial discharge(PD) is incepted.Before putting into use,the PD detection should be performed on inverter-fed motors at repetitive square voltages to avoid the PD caused insulation deterioration when the motors are collected to inverters having specific characteristics.However,unlike PD tests at AC/DC voltages proposed in IEC 60270,the PD detection at repetitive square voltages is much more complex because of serious interference generated by impulse generator.To solve the problem,ultra-high frequency(UHF) method seems recommendable for its preferable signal-to-noise ratio(SNR).The chief aim of this study is to investigate PD pulse and statistical characteristics of turn-to-turn insulation for inverter-fed traction motors.A square-shaped Archimedes antenna,specially designed for the PD detection at repetitive square voltages of fast rise times,was used to perform PD tests on turn-to-turn insulation models.Time and frequency analysis results indicate that energy component of generator disturbance and PD pulses are mainly distributed in the 0-0.5 GHz and 0.6-1.5 GHz range,respectively.Based on the results,suitable filter was designed for power disturbance suppression.Additionally,resorting to the sensor unit(i.e.antenna and filter) and the PD test system,the PD statistical features at square voltages of different frequencies were obtained.Experimental results show that higher frequency will give rise,statistically,to PD of lower magnitudes distributing at smaller phases.A reasonable interpretation of this phenomenon was presented.Lastly,according to the PD statistical features,some suggestions for the PD detection system design,generator parameter optimization and the PD pulse extracting were given.The results of this work would be beneficial to the increase of the sensitivity when performing the PD detection on insulation systems for inverter-fed motors at repetitive square voltages and thus,improving the reliability of inverter-fed motors. 相似文献
87.
The objective of this study was to investigate if coexisting compounds could affect the fate of pharmaceuticals in surface water under solar irradiation. The degradation of metronidazole (MET) in the presence of different coexisting pharmaceuticals was investigated in batch experiments with exposure to sunlight. Tinidazole, which has a similar structure to MET, was employed as an analogue. The results indicated that the presence of an analogue with a similar photosensitive group to MET could inhibit the photodegradation of MET. In addition, the effect of coexisting pharmaceuticals with different absorption spectra on the degradation of MET was investigated. The results showed that the effect depended on the degree of overlapping absorption spectra between MET and the coexisting pharmaceuticals. The relationship between the degree of the influence and the ultraviolet absorption spectra of coexisting pharmaceuticals found in this study could give guidance in assessing the fate of pharmaceuticals in environmental water. 相似文献
88.
曾明凤 《成都纺织高等专科学校学报》2013,30(1):55-58
通过我国高职院校(以成职院为例)与新加坡南洋理工学院在公共基础课的教学模式、课程设置、课程与专业结合的针对性以及学生全面素质培育方面,进行思考和分析,提出了结合我国高等职业教育实际情况的思考和建议。 相似文献
89.
An accurate closed form solution is proposed to estimate camera pose by several mirrored reference object images acquired via a planar mirror under different unknown poses. Compared with state-of-the-art methods, our method is more accurate when there are more than three images and has explicit geometric meanings. This method also properly handles cases in which some of the mirror poses are parallel. The central idea is to minimize an error metric based on all reflections of rotation, which enables the camera rotation to be estimated directly by SVD of sum of mirrored camera rotations. After that, the camera translation is computed by solving a large system of linear equations to minimize object space collinearity error. Both synthesized data and real data experiments show the advantages of our approach. 相似文献
90.
海面高程的传递是水准测量中的难题.以宁波市象山县某围堤工程变形测量为例,对全站仪进行跨海面高程测量进行了成功应用,并用GPS拟合高程测量方法和平均海平面法进行了验证,结果合理. 相似文献