全文获取类型
收费全文 | 388594篇 |
免费 | 29852篇 |
国内免费 | 16536篇 |
专业分类
电工技术 | 22192篇 |
技术理论 | 49篇 |
综合类 | 26773篇 |
化学工业 | 64945篇 |
金属工艺 | 22116篇 |
机械仪表 | 23944篇 |
建筑科学 | 29169篇 |
矿业工程 | 12329篇 |
能源动力 | 10758篇 |
轻工业 | 26004篇 |
水利工程 | 7147篇 |
石油天然气 | 24221篇 |
武器工业 | 2923篇 |
无线电 | 43643篇 |
一般工业技术 | 43682篇 |
冶金工业 | 21094篇 |
原子能技术 | 3986篇 |
自动化技术 | 50007篇 |
出版年
2024年 | 1538篇 |
2023年 | 5886篇 |
2022年 | 10578篇 |
2021年 | 14803篇 |
2020年 | 11146篇 |
2019年 | 9162篇 |
2018年 | 10576篇 |
2017年 | 11822篇 |
2016年 | 10853篇 |
2015年 | 14758篇 |
2014年 | 18648篇 |
2013年 | 22790篇 |
2012年 | 24428篇 |
2011年 | 27219篇 |
2010年 | 23867篇 |
2009年 | 22766篇 |
2008年 | 22396篇 |
2007年 | 21313篇 |
2006年 | 21487篇 |
2005年 | 18802篇 |
2004年 | 12978篇 |
2003年 | 11793篇 |
2002年 | 11177篇 |
2001年 | 9899篇 |
2000年 | 9507篇 |
1999年 | 10035篇 |
1998年 | 8097篇 |
1997年 | 6782篇 |
1996年 | 6356篇 |
1995年 | 5223篇 |
1994年 | 4247篇 |
1993年 | 2941篇 |
1992年 | 2312篇 |
1991年 | 1779篇 |
1990年 | 1448篇 |
1989年 | 1187篇 |
1988年 | 992篇 |
1987年 | 674篇 |
1986年 | 537篇 |
1985年 | 385篇 |
1984年 | 315篇 |
1983年 | 238篇 |
1982年 | 198篇 |
1981年 | 134篇 |
1980年 | 175篇 |
1979年 | 90篇 |
1978年 | 77篇 |
1977年 | 80篇 |
1976年 | 104篇 |
1975年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
大型连杆流线简易试验方法 总被引:1,自引:1,他引:0
程里 《理化检验(物理分册)》2004,40(9):457-458
介绍了一种大型连杆流线的简易试验方法及其评价原则。该方法可清晰显示流线,并适合任何尺寸和形状的锻造连杆的流线试验。 相似文献
52.
VCOs fully integrated in an SiGe preproduction technology are presented. By cutting interconnection lines a wide frequency range can be covered, up to 88.4 GHz. Special effort has been made to meet the demands for 77 GHz automotive radar. In the corresponding tuning range from 75.3 to 79.6 GHz, an output power of about 11 dBm (with -2.2 dBm potential measurement uncertainty) was achieved for each of the two complementary outputs, i.e. in total 14 dBm. The phase noise is about -94 dBc/Hz at 1 MHz offset frequency. 相似文献
53.
This paper investigates the catalytic ignition of the H2/O2/CO2 mixture on platinum in a stagnation flow at atmospheric pressure experimentally and numerically. We measure the ignition temperatures of the gas mixtures flowing towards resistively heated platinum with various composition ratios and various diluent gases of N2, Ar and CO2. Compared with N2 or Ar, the CO2 dilution shows higher ignition temperature by about 50 K, even at the same composition ratio. The ignition temperature increase is proportional to the dilution ratio. Through the numerical simulation, it is illustrated that higher ignition temperature is caused by the adsorption of CO2 and following dissociation on platinum surface, which was to date considered negligible in catalytic combustion. 相似文献
54.
An adaptive p-persistent MAC scheme for multimedia WLAN 总被引:1,自引:0,他引:1
Chih-Ming Yen Chung-Ju Chang Yih-Shen Chen 《Communications Letters, IEEE》2006,10(11):737-739
The letter proposes an adaptive p-persistent-based (APP) medium access control (MAC) scheme for the IEEE 802.11e distributed WLAN supporting multimedia services. The APP MAC scheme adaptively gives differentiated permission probabilities to transmission stations which are in different access category and with various waiting delay. Simulation results show that the APP MAC scheme can improve the performance of multimedia WLAN, such as small voice packet dropping probability, low delay variation, and high system throughput, compared to conventional MAC algorithms 相似文献
55.
燕皮传统加工工艺中碱液对肉糜特性的影响 总被引:1,自引:1,他引:0
燕皮是以猪肉和甘薯粉为原料,手工制成的薄如纸且经煮不烂的传统食品。在传统制作燕皮过程中添加山榉灰配制的碱液是影响肉糜品质的关键步骤。通过测定制作燕皮过程中各工序样品的氮溶解指数、持水性、乳化稳定性、pH值和粘度,利用SDS-PAGE分析样品中的蛋白质组分、利用光学显微镜观察它们的结构变化,证实植物碱液能够提高样品的氮溶解指数、持水性和乳化稳定性并且延迟了肉糜硬化。同时实验证明碳酸碱(Na2CO3或K2CO3)可替代传统工艺中的植物碱,为后续标准化、工业化生产提供可行条件。 相似文献
56.
57.
58.
Ming-Dou Ker Chyh-Yih Chang Yi-Shu Chang 《Components and Packaging Technologies, IEEE Transactions on》2004,27(3):445-451
This paper reports a real case of electrostatic discharge (ESD) improvement on a complementary metal oxide semiconductor integrated circuit (IC) product with multiple separated power pins. After ESD stresses, the internal damage have been found to locate at the interface circuit connecting between different circuit blocks with different power supplies. Some ESD designs have been implemented to rescue this IC product to meet the required ESD specification. By adding only an extra ESD clamp N-channel metal oxide semiconductor with a channel width of 10 /spl mu/m between the interface node and the ground line, the human-body-model (HBM) ESD level of this IC product can be improved from the original 0.5 to 3 kV. By connecting the separated vertical sync signal (VSS) power lines through the ESD conduction circuit to a common VSS ESD bus realized by the seal ring, the HBM ESD level of the enhanced version IC product with 12 separated power supplies pairs can be significantly improved from original 1 kV up to > 5 kV, without the noise coupling issue. 相似文献
59.
Ching-Wen Tang Chi-Yang Chang 《Electronics letters》2002,38(15):801-803
A novel chip-type ceramic balun designed in the 2.4 GHz ISM band frequency is presented. A buried capacitor is included in the balun, so that the length of the coupled transmission lines can be reduced and can be designed very easily. A meander or spiral broadside coupled-line is adopted to realise the proposed LTCC multi-layer balun. The measured performances of phase and amplitude balance for this LTCC-MLC balun show a good match with computer simulation 相似文献
60.
文章简要分析了我国目前在中硬岩石爆破中工业炸药的使用情况,介绍了山西兴安化学材料厂新研制的一种适用于硬岩爆破的高爆速、高威力水胶炸药新品种,对其性能、爆破效果、经济实用性和安全性等进行了阐述。 相似文献