全文获取类型
收费全文 | 16252篇 |
免费 | 836篇 |
国内免费 | 428篇 |
专业分类
电工技术 | 5232篇 |
技术理论 | 1篇 |
综合类 | 682篇 |
化学工业 | 516篇 |
金属工艺 | 343篇 |
机械仪表 | 871篇 |
建筑科学 | 607篇 |
矿业工程 | 195篇 |
能源动力 | 1489篇 |
轻工业 | 121篇 |
水利工程 | 579篇 |
石油天然气 | 101篇 |
武器工业 | 68篇 |
无线电 | 2259篇 |
一般工业技术 | 439篇 |
冶金工业 | 206篇 |
原子能技术 | 449篇 |
自动化技术 | 3358篇 |
出版年
2024年 | 29篇 |
2023年 | 145篇 |
2022年 | 192篇 |
2021年 | 315篇 |
2020年 | 312篇 |
2019年 | 252篇 |
2018年 | 221篇 |
2017年 | 379篇 |
2016年 | 441篇 |
2015年 | 461篇 |
2014年 | 845篇 |
2013年 | 697篇 |
2012年 | 815篇 |
2011年 | 1254篇 |
2010年 | 936篇 |
2009年 | 947篇 |
2008年 | 956篇 |
2007年 | 1051篇 |
2006年 | 1168篇 |
2005年 | 1415篇 |
2004年 | 1117篇 |
2003年 | 681篇 |
2002年 | 390篇 |
2001年 | 293篇 |
2000年 | 267篇 |
1999年 | 303篇 |
1998年 | 302篇 |
1997年 | 218篇 |
1996年 | 236篇 |
1995年 | 191篇 |
1994年 | 168篇 |
1993年 | 157篇 |
1992年 | 107篇 |
1991年 | 67篇 |
1990年 | 39篇 |
1989年 | 33篇 |
1988年 | 37篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 19篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 8篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
介绍采用射线方法检测功率管芯片与基座之间的焊接质量。试验证明,选用合适的透照参数可使X射线照相和X射线实时成像对焊接部位的检测均得到较高的对比灵敏度,但X射线照相法成本低廉,一次可透照多个工件,效率高,为该功率管焊接质量的理想检测方法。 相似文献
72.
73.
74.
The paper shows that an analytical evaluation of the power coefficient Cp for an ideal horizontal-axis wind turbine can be made via an expression giving the direct relationship of Cp and the axial induction factor a. The results obtained agree closely with those obtained numerically from the usual integral expression involving several variables. 相似文献
75.
Mesopore nickel-based mixed rare-earth oxide (NMRO) and activated carbon (AC) with rich oxygen-contained groups were prepared as electrode materials in a supercapacitor using room temperature ionic liquid (RTIL) electrolyte. These electrode materials were characterized by XPS, XRD, N2 adsorption, SEM as well as various electrochemical techniques, and showed good properties and operated well with RTIL electrolyte. A 3 V asymmetrical supercapacitor was fabricated, which delivered a real power density of 458 W kg−1 as well as a real energy density of 50 Wh kg−1, and during a 500-cycle galvanostatic charge/discharge measurement, no capacity decay was visible. Such promising energy-storage performance was to a large extent ascribed to nonvolatile RTIL electrolyte with wide electrochemical windows and high stable abilities worked with both electrode materials. 相似文献
76.
Liaqat A. Khan Edward A. Wicklein E. C. Teixeira 《Canadian Metallurgical Quarterly》2006,132(7):741-746
A three-dimensional (3D) computational fluid dynamics (CFD) model of a contact tank is presented in this paper. The model results are compared against 3D velocities and flow through curve (FTC) data, representing a tracer concentration profile, from a 1:8 scale physical model. The objective is to demonstrate that CFD models can simulate both the FTC and the 3D velocity field quite well. Simultaneous validation of velocities and FTC is important in ascertaining the predictive capabilities of CFD models, as physical model studies indicate that different baffle arrangements can lead to similar FTCs. Therefore, a good prediction of only FTC, as presented in previous 3D CFD model studies, does not necessarily imply a correct simulation of the flow field. 相似文献
77.
The irradiation with high-energy (7.35 MeV) protons through a set of energy degraders was used to suppress leakage of the silicon power diodes subjected to local lifetime control. The aim was to modify the profile of recombination centers and to reduce production of vacancy complexes. The high-energy proton irradiation was compared with standard local lifetime killing by high-energy alphas. Recombination centers arising from irradiation were characterized after irradiation and subsequent annealing at 220 and 350 °C by deep level transient spectroscopy and I-V profiling. Static and dynamic parameters of irradiated diodes were also measured and compared. Results show that the applied irradiation with protons provides 3-10 times lower leakage compared to standard alphas for equivalent reduction of the reverse recovery current maximum. On the other hand, the excessive formation of hydrogen donors at high proton fluences and their diffusion during annealing at 350° decreases diode blocking capability. 相似文献
78.
Tsuyoshi Takahashi Masahito Kitou Michio Asai Mitsuyasu Kido Tomio Chiba Junzou Kawakami Yoshiaki Matsui 《Electrical Engineering in Japan》1994,114(2):18-33
Power system control equipment needs higher sensitivity and operational reliability. Advanced voltage control equipment is needed for reducing the frequency of tap changes and improving the characteristics (the relationship between the actual voltage and reference voltage) of the voltage to meet today's power system requirements. However, these objectives are in a trade-off relationship. Studies of voltage control derived from a knowledge base suitable for electric power systems can satisfy these objectives using fuzzy inference. Compared with corresponding conventional equipment, the new equipment improved the deviation of 30 min average voltage of 30 percent. This paper describes the design concept of new voltage control equipment using fuzzy inference. In addition, field test results are described along with rules of fuzzy inference, membership functions, and the deviation of 30 min average voltage through detailed simulation. 相似文献
79.
胡志勇 《电子工业专用设备》2003,32(3):83-86
叙述了先进再流焊接技术的新发展,描述了提高BGA再流焊接效果的工艺要点,优化倒装芯片再流焊接和固化的新方法。最后,讲述了先进的降低氮消耗量的方法即:通过最大限度地提高潜在收益,以促进再流焊接技术的发展,以此来满足装配厂商的需要。 相似文献
80.
Since the energy budget of mobile nodes is limited, the performance of a networking protocol for such users should be evaluated in terms of its energy efficiency, in addition to the more traditional metrics such as throughput. In this paper, two topology-unaware MAC protocols—in which the scheduling time slots are allocated irrespectively of the underline topology—are considered and their energy consumption is derived. It turns out that the per frame power consumption is lower for the less throughput-efficient protocol, suggesting that energy savings are achieved at the expense of throughput.A finer energy consumption study is carried out in the sequel, focusing on the amount of energy consumed to successfully transmit a certain number of packets, or equivalently, on the per successful transmission power consumption. It is shown that the more throughput-efficient protocol consumes less energy per successful transmission under certain conditions (which are derived), due to the lower number of transmission attempts before a data packet is successfully transmitted. The same energy-efficiency relation is observed under certain conditions (which are derived) when data packets are delay constrained and, thus, may become obsolete if not transmitted successfully within a specific time interval. The conditions under which the per successful transmission power consumption is minimized for delay-constrained packets, are also established in this work and it is observed that when the system throughput is maximized, the power consumed is close to the minimum. Simulation results support the claims and the expectations of the aforementioned analysis. 相似文献