全文获取类型
收费全文 | 3171篇 |
免费 | 456篇 |
国内免费 | 277篇 |
学科分类
工业技术 | 3904篇 |
出版年
2024年 | 5篇 |
2023年 | 43篇 |
2022年 | 44篇 |
2021年 | 60篇 |
2020年 | 53篇 |
2019年 | 42篇 |
2018年 | 51篇 |
2017年 | 76篇 |
2016年 | 91篇 |
2015年 | 95篇 |
2014年 | 165篇 |
2013年 | 184篇 |
2012年 | 231篇 |
2011年 | 247篇 |
2010年 | 212篇 |
2009年 | 218篇 |
2008年 | 247篇 |
2007年 | 283篇 |
2006年 | 240篇 |
2005年 | 231篇 |
2004年 | 222篇 |
2003年 | 170篇 |
2002年 | 120篇 |
2001年 | 90篇 |
2000年 | 78篇 |
1999年 | 63篇 |
1998年 | 54篇 |
1997年 | 38篇 |
1996年 | 38篇 |
1995年 | 38篇 |
1994年 | 37篇 |
1993年 | 28篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有3904条查询结果,搜索用时 15 毫秒
1.
2.
Dr. Héctor Zamora-Carreras Dr. Beatriz Maestro Dr. Jesús M. Sanz Dr. M. Angeles Jiménez 《Chembiochem : a European journal of chemical biology》2020,21(4):432-441
A common interpretation of Anfinsen's hypothesis states that one amino acid sequence should fold into a single, native, ordered state, or a highly similar set thereof, coinciding with the global minimum in the folding-energy landscape, which, in turn, is responsible for the function of the protein. However, this classical view is challenged by many proteins and peptide sequences, which can adopt exchangeable, significantly dissimilar conformations that even fulfill different biological roles. The similarities and differences of concepts related to these proteins, mainly chameleon sequences, metamorphic proteins, and switch peptides, which are all denoted herein “turncoat” polypeptides, are reviewed. As well as adding a twist to the conventional view of protein folding, the lack of structural definition adds clear versatility to the activity of proteins and can be used as a tool for protein design and further application in biotechnology and biomedicine. 相似文献
3.
Discretization of continuous time autoregressive (AR) processes driven by a Brownian motion and embedding of discrete time AR sequences driven by a Gaussian white noise are classical issues. The article aims at establishing and using such discretization and embedding formulae between extended AR continuous time processes and discrete time sequences. The continuous-time processes are driven by either Brownian or jump processes, and may have random coefficients depending on time; Lévy-driven processes are also considered. The innovation of the discrete time processes may be of many types – including Gaussian. In one way, observing the continuous time AR process at discrete times leads the AR dynamics of the discretized process to be characterized. The other way round, AR sequences can be embedded, in the almost sure sense, into continuous time AR processes with the same dynamics. Illustration is provided through many examples and simulation. 相似文献
4.
针对某型阻力伞性能鉴定试飞科目要求,需要精确测量阻力伞在稳定工作时的垂直、水平摆角,从而为该产品的技术鉴定提供依据。本文根据加装在飞机机背中段的高速摄像机,获取阻力伞的运动影像,通过图像分析处理识别特征点的亚象素坐标,采用摄影测量的解算算法,推导出数学解算模型,实现了阻力伞运动参数的最优解算。结合真实飞行试验对测量结果进行了分析,数据结论准确。 相似文献
5.
Reducing the complexity of distance measurement methods for circular turbo codes that use structured interleavers 下载免费PDF全文
Youssouf Ould‐Cheikh‐Mouhamedou 《International Journal of Communication Systems》2015,28(9):1572-1579
The knowledge of turbo code's minimum Hamming distance (dmin) and its corresponding codeword multiplicity (Amin) is of a great importance because the error correction capability of a code is strongly tied to the values of dmin and Amin. Unfortunately, the computational complexity associated with the search for dmin and Amin can be very high, especially for a turbo code that has high dmin value. This paper introduces some useful properties of turbo codes that use structured interleavers together with circular encoding. These properties allow for a significant reduction of search space and thus reduce significantly the computational complexity associated with the determination of dmin and Amin values. © 2014 The Authors. International Journal of Communication Systems published by John Wiley & Sons, Ltd. 相似文献
6.
ABSTRACTIn recent times, the applications of multimedia are rising in a greedy mode and hence the amount of video transactions is also increasing exponentially. This has shouted great demands on effective models on video encoding and also for reducing the transmission channel congestion. This research work introduces a managing technique termed weighted encoding for High-Efficiency Video Coding (HEVC). HEVC, also termed as MPEG-H Part 2 and H.265 is a video compression standard that is widely utilized AVC (H.264 or MPEG-4 Part 10). When compared to AVC, HEVC grants double the ratio of data compression at a similar level of quality of the video or considerably enhanced video quality at a similar bit rate. This work intends to optimize the weight that adopted in HEVC for encoding. For this, this paper proposes a new Iterative based propagation update in the water wave Optimization Algorithm (IPU-WWO), which is the improved form of Water wave Optimization (WWO). The performance of proposed IPU-WWO is compared over other conventional methods like Artificial Bee Colony (ABC), Firefly (FF), Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) with respect to Peak Signal to Noise Ratio (PSNR). By doing the encoding process, it minimizes the video size with perceptually better quality video or PSNR. 相似文献
7.
8.
经过野外观测和室内分析测试,认为阿尔泰南缘三个等间距斜列的麦兹、克朗、冲乎尔火山沉积盆地中,广泛分布着泥盆纪火山沉积建造,它们控制着阿尔泰南缘多金属矿带的展布 相似文献
9.
目的 快速响应矩阵码(quick response code,QR code)简称二维码,是一种由深色和浅色模块组成的正方形符号。给定输入数据,不同编码算法可能输出不同的位流。位流长度决定了二维码的版本,进而决定了二维码每条边上的模块数量。减小二维码的版本能够在不减小模块大小的前提下节省面积,或者在不改变面积的前提下增大模块大小。为了减小二维码面积、提高二维码识读率,本文提出了位流长度最小化算法。方法 首先,根据二维码位流可以分段切换编码模式的特点,归纳了6种编码状态;然后,根据二维码位流编码标准推导了状态转移关系,从而将位流长度最小化问题转换成动态规划问题;最后,通过求解动态规划问题,计算出最短位流。针对统一资源定位符(uniform resource locator,URL)类型数据,利用其部分字段对大小写不敏感、部分字段可以转义的性质,提出了统一资源定位符的最短位流计算算法,进一步缩短位流。结果 本文构建了一个测试集,包含603个编码了非URL数据的二维码,以及1 679个编码了URL数据的二维码。实验结果表明,本文算法与二维码标准相比,对于非URL测试集,位流长度减小的二维码占比9.1%,版本减小的二维码占比1.2%;对于URL测试集,位流长度减小的二维码占比98.4%,版本减小的二维码占比31.7%。结论 二维码位流长度最小化算法输出的位流长度最短,输出的二维码版本最小,能在兼容标准二维码解码器且不影响纠错能力的前提下提升二维码的数据容量。同时,本文算法运行速度快,易于使用,没有需要调节的参数。 相似文献
10.
This paper considers the state‐dependent interference relay channel (SIRC) in which one of the two users may operate as a secondary user and the relay has a noncausal access to the signals from both users. For discrete memoryless SIRC, we first establish the achievable rate region by carefully merging Han‐Kobayashi rate splitting encoding technique, superposition encoding, and Gelfand‐Pinsker encoding technique. Then, based on the achievable rate region that we derive, the capacity of the SIRC is established in many different scenarios including (a) the weak interference regime, (b) the strong interference regime, and (c) the very strong interference regime. This means that our capacity results contain all available known results in the literature. Next, the achievable rate region and the associated capacity results are also evaluated in the case of additive Gaussian noise. Additionally, many numerical examples are investigated to show the value of our theoretical derivations. 相似文献