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161.
Sourabh Dongaonkar Muhammad A. Alam 《Progress in Photovoltaics: Research and Applications》2015,23(2):170-181
Partial shading in photovoltaic modules is an important reliability and performance concern for all photovoltaic technologies. In this paper, we show how cell geometry can be used as a design variable for improved shade tolerance and performance in monolithic thin film photovoltaic modules (TFPV). We use circuit simulations to illustrate the geometrical aspects of partial shading in typical monolithic TFPV modules with rectangular cells, and formulate rules for shade tolerant design. We show that the problem of partial shading can be overcome by modifying the cell shape and orientation, while preserving the module shape and output characteristics. We discuss two geometrical designs with cells arranged in radial and spiral patterns, which (i) prevent the reverse breakdown of partially shaded cells, (ii) improve the overall power output under partial shading, and (iii) in case of spiral design, may additionally improve the module efficiency by reducing sheet resistance losses. We compare these designs quantitatively using realistic parameters and discuss the practical aspects for their implementation. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
162.
基于Solidworks三维平台,采用Access,Sql Server及VB编程语言,通过调用SolidWorks的API应用编程接口进行客车件冲压成形模具软件系统的设计和开发。论述了三维冲压成形模具的设计过程,并给出了三维冲压成形模具设计系统的体系结构和系统的设计实例。 相似文献
163.
介绍了输出脉冲电压600kV、脉冲电流6kA、高功率强流脉冲系统,分析双路并联Blumlein形成线和集中式结构的优越性及仿真结果。 相似文献
164.
Constant modulus algorithm (CMA) is an adaptive technique for correcting multipath and interference-induced degradations in
constant envelope waveforms. The algorithm exploits the fact that both multipath and additive interference can disrupt the
constant envelope of the received signal. By detecting the received envelope variations, the adaptive algorithm has the ability
to reset the coefficients vector so as to remove the variations, and in the process, reject the various interference components
from the desired signal. If both the interferer and the signal of interest have constant envelope and are spectrally non-overlapped,
it is possible to find two different solutions for the coefficient vector, in which one suppresses the interferer and the
other “captures” the interferer. The problem of how “capture” can occur and how it may be prevented in Gaussian noise environment
has been perfectly developed in the previous work (Treichler, Larimore, IEEE Trans Acoust Speech Signal Process, 33:946–958,
1985). However, recent investigation on the physical channels in wireless communication shows that there is aggregate noise
component exhibiting high amplitudes for small duration time interval. This paper proposes a GCMA (Generalized CMA) which
generalizes the CMA by introducing the α-stable distribution as the noise model. Here the original CMA is only a special case of the GCMA. In order to describe the
average behavior of the GCMA, a simple model consisting of only two sinusoids is presented. As assuming slow adaptation, the
adaptive weight recursion is shown to compress into a two-by-two recursion in the tone output amplitudes. The simplified recursion
is analyzed to determine what combination of signals power and initialization on coefficient vectors leads to “lock” and what
leads to the capture of the interferer. The method to determine lock and capture zone boundaries is analyzed. These convergence
properties of the GCMA are studied by computer simulations.
相似文献
Ting LiEmail: |
165.
激光快速成形过程中熔池形态的演化 总被引:7,自引:0,他引:7
采用高速摄影技术对激光快速成形过程中液态熔池的形成及其演化过程进行了实时观察。结果发现,以一定速度向前运动的激光束辐照基材时,基材表面开始熔化并形成液态熔池,经过一个较短的时间间隔(约1.0 s)后熔池深度增大至一定值,熔池长度则围绕一恒定值波动。以恒定送粉率向熔池中连续送进金属粉末时,熔池的长度和宽度逐渐减小,熔池寿命缩短。同时熔池后沿不断抬高即熔覆层厚度不断增加,最大熔深处熔池自由表面法向和激光束轴线之间的夹角由几度逐渐增大到20°~30°左右。熔池自由表面发生周期性的变化,实验观察到熔池后沿有周期性的“岛状凸起”出现和消失现象。数值计算结果证实这主要是熔池中熔体在表面张力梯度下引起的强制对流作用的结果。 相似文献
166.
以氧为辅助气体的激光切割工艺切割不锈钢等特种钢板时容易产生挂渣现象,因此大多采用高压高纯度氮气或惰性气体辅助激光切割不锈钢。在对熔渣形成原因及规律进行实验研究的前提下,提出了仍以氧辅助切割以降低激光切割功率,通过在工件底部加设旋风除渣器,形成旋转气流控制熔渣流向以去除熔渣的方法。实验证明,当同轴辅助切割气体为氧气,气体压力降低为300 kPa,旋转气流引导装置气体压力为100 kPa,激光功率为500 W,模式为TEM01,焦点位于0.5 mm厚硅钢片工件上表面,切割速度为3 m/min时,可获得光滑的高质量切口。 相似文献
167.
Rake接收机在3G系统中已被广泛使用,实际应用证明它能够有效对抗移动无线信道中的多径衰落。传统Rake接收机有其时域一维处理的局限性,为获得更好的系统性能,本文在分析空时信道模型的基础上提出一种新的空时2D-Rake接收机算法,它将波束形成技术与Rake相结合。这种波束形成算法能够在干扰方向上完全陷零,其权重仅与阵列天线的导向矢量有关,与接收信号无关。最后简要分析了所提出的2D-Rake接收机的性能。仿真结果表明,这种空时2D-Rake接收机与传统Rake接收机相比,具有较好的性能,而且该算法对噪声具有鲁棒性。 相似文献
168.
169.
170.
Youn Tae Kim Chi Hoon Jun Jong-Tae Baek Hyung Joun Yoo Sang-Koo Chung 《Journal of Electronic Materials》1995,24(10):1413-1417
In this study, we have investigated sensitivities of the ion implanted silicon wafers processed by rapid thermal annealing
(RTA), which can reveal the variation of sheet resistance as a function of annealing temperature as well as implantation parameters.
All the wafers were sequentially implanted by the arsenic or phosphorous implantations at 40, 80, and 100 keV with the dose
level of 1014 to 2 × 1016 ions/cm2. Rapid thermal annealing was carried out for 10 s by the infrared irradiation at a temperature between 850 and 1150°C in
the nitrogen ambient. The activated wafer was characterized by the measurements of the sheet resistance and its uniformity
mapping. The values of sensitivities are determined from the curve fitting of the experimental data to the fitting equation
of correlation between the sheet resistance and process variables. From the sensitivity values and the deviation of sheet
resistance, the optimum process conditions minimizing the effects of straggle in process parameters are obtained. As a result,
a strong dependence of the sensitivity on the process variables, especially annealing temperatures and dose levels is also
found. From the sensitivity analysis of the 10 s RTA process, the optimum values for the implant dose and annealing temperature
are found to be in the range of 1016 ions/cm2 and 1050-1100°C, respectively. The sensitivity analysis of sheet resistance will provide valuable data for accurate activation
process, offering a guideline for dose monitoring and calibration of ion implantation process. 相似文献