全文获取类型
收费全文 | 30133篇 |
免费 | 1770篇 |
国内免费 | 1245篇 |
专业分类
电工技术 | 1212篇 |
技术理论 | 3篇 |
综合类 | 1177篇 |
化学工业 | 4524篇 |
金属工艺 | 2131篇 |
机械仪表 | 1435篇 |
建筑科学 | 1831篇 |
矿业工程 | 476篇 |
能源动力 | 1014篇 |
轻工业 | 1588篇 |
水利工程 | 378篇 |
石油天然气 | 1245篇 |
武器工业 | 110篇 |
无线电 | 3825篇 |
一般工业技术 | 6190篇 |
冶金工业 | 2466篇 |
原子能技术 | 355篇 |
自动化技术 | 3188篇 |
出版年
2024年 | 65篇 |
2023年 | 329篇 |
2022年 | 524篇 |
2021年 | 809篇 |
2020年 | 549篇 |
2019年 | 590篇 |
2018年 | 733篇 |
2017年 | 723篇 |
2016年 | 730篇 |
2015年 | 822篇 |
2014年 | 1085篇 |
2013年 | 1765篇 |
2012年 | 1571篇 |
2011年 | 1902篇 |
2010年 | 1595篇 |
2009年 | 1811篇 |
2008年 | 1665篇 |
2007年 | 1630篇 |
2006年 | 1617篇 |
2005年 | 1333篇 |
2004年 | 1098篇 |
2003年 | 948篇 |
2002年 | 869篇 |
2001年 | 822篇 |
2000年 | 844篇 |
1999年 | 845篇 |
1998年 | 1104篇 |
1997年 | 881篇 |
1996年 | 782篇 |
1995年 | 614篇 |
1994年 | 462篇 |
1993年 | 368篇 |
1992年 | 288篇 |
1991年 | 226篇 |
1990年 | 212篇 |
1989年 | 201篇 |
1988年 | 142篇 |
1987年 | 82篇 |
1986年 | 81篇 |
1985年 | 61篇 |
1984年 | 58篇 |
1983年 | 45篇 |
1982年 | 42篇 |
1981年 | 25篇 |
1980年 | 28篇 |
1979年 | 19篇 |
1978年 | 21篇 |
1977年 | 17篇 |
1974年 | 13篇 |
1970年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Baeyens Y. Georgiou G. Weiner J.S. Leven A. Houtsma V. Paschke P. Lee Q. Kopf R.F. Yang Yang Chua L. Chen C. Liu C.T. Young-Kai Chen 《Solid-State Circuits, IEEE Journal of》2002,37(9):1152-1159
The combination of device speed (f/sub T/, f/sub max/ > 150 GHz) and breakdown voltage (V/sub bceo/ > 8 V) makes the double heterojunction bipolar InP-based transistor (D-HBT) an attractive technology to implement the most demanding analog functions of 40-Gb/s transceivers. This is illustrated by the performance of a number of analog circuits realized in an InP D-HBT technology with an 1.2- or 1.6-/spl mu/m-wide emitter finger: a low phase noise push-push voltage-controlled oscillator with -7-dBm output power at 146 GHz, a 40-GHz bandwidth and low-jitter 40-Gb/s limiting amplifier, a lumped 40-Gb/s limiting driver amplifier with 4.5-V/sub pp/ differential output swing, a distributed 40-Gb/s driver amplifier with 6-V/sub pp/ differential output swing, and a number of distributed preamplifiers with up to 1.3-THz gain-bandwidth product. 相似文献
42.
Math1 is essential for genesis of cerebellar granule neurons 总被引:1,自引:0,他引:1
N Ben-Arie HJ Bellen DL Armstrong AE McCall PR Gordadze Q Guo MM Matzuk HY Zoghbi 《Canadian Metallurgical Quarterly》1997,390(6656):169-172
43.
Laparoscopic retroperitoneal lymph node dissection is a new surgical procedure used to enhance staging in men with clinical stage I nonseminomatous germ cell tumors of the testis. The procedure has been performed in a limited number of patients at several centers with extensive laparoscopic experience. Laparoscopic retroperitoneal lymphadenectomy is a technically demanding procedure which can be successfully completed in the majority of patients. However, the risk of complications is greater than in patients who undergo standard open retroperitoneal lymph node dissection. The primary advantage of a laparoscopic approach is shortened hospitalization and rapid return to normal activity. The role of laparoscopy in the management of patients with testis malignancy has not been defined. The use of this staging procedure may help minimize the need for surveillance studies following surgery and may be best utilized in men with a lower likelihood of nodal metastases. Ultimately, prospective study in large groups of patients will be necessary to determine the role of laparoscopic retroperitoneal lymph node dissection in patients with testis cancer. 相似文献
44.
Social burden caused by paralyzed poliomyelitis was analysed, using data from a Sampling Survey of Handicapped People in China, in 1987. The study results showed: 29.94% of 1707 handicapped polio victims aged 6 or over were not able to go to school; 44.23% of them could not take care of their daily life; 36.32% of them could not play out-door and do shopping; 2.58% of them could not normally communicate with others. 84.53% of the 1487 handicapped victims caused by polio aged 15 or over wholly or partly lost their working ability. We also compared handicapped people's employment rate and the status of marriage with non-handicapped people. Data showed that the employment rate and the number of married handicapped polio victims were remarkably lower then those non-handicapped people. 相似文献
45.
The robust Schur stability of a polynomial with uncertain coefficients will be investigated. A formula for the stability radius of a Schur polynomial is established. The result is the counterpart of [1] for linear discrete-time systems 相似文献
46.
本文介绍了Windows环境下基于消息的DDE和基于动态链接库的DDEML的区别,并详细叙述了如何使用DDEML编制Windows应用程序。 相似文献
47.
BP算法的改进及用模拟电路实现的神经网络分类器 总被引:1,自引:0,他引:1
基于用模拟电路实现神经网络分类器的目的,对多层静态前馈神经网络的BP算法做了改进,采用线性限幅函数代替Sigmoid函数作为神经元的激活函数,给出了改进的BP算法。对该算法性能的实验研究表明:这种改进算法不但方便了用线性模拟集成运算放大电路实现神经网络,而且具有学习速度快,映射能力强等优点。根据本文算法设计的神经网络分类器,无论是计算机仿真,还是模拟电路实现,都得到了比较高的识别率。 相似文献
48.
49.
50.
A method for modeling and analyzing vias the multilayered integrated circuits is presented. The model is based on microwave network theory. The whole via structure is divided into cascaded subnetworks, including a vertical via passing through different layers and transitions from the microstrip line and/or striplines to the vertical via. The parameters of each subnetwork are obtained from electromagnetic field analysis. Numerical results in the frequency domain and the time domain are presented. Validation of the model has been carried out by both measurements and finite-difference-time-domain (FDTD) modeling. The results show good agreement with the measurements in the frequency range for which the components of the experimental model are within specification. The time domain simulation results also agree well with the FDTD results 相似文献