首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9998篇
  免费   237篇
  国内免费   33篇
电工技术   92篇
综合类   23篇
化学工业   1212篇
金属工艺   203篇
机械仪表   196篇
建筑科学   152篇
矿业工程   19篇
能源动力   447篇
轻工业   594篇
水利工程   77篇
石油天然气   94篇
武器工业   3篇
无线电   695篇
一般工业技术   1306篇
冶金工业   4466篇
原子能技术   71篇
自动化技术   618篇
  2023年   104篇
  2022年   197篇
  2021年   250篇
  2020年   219篇
  2019年   196篇
  2018年   280篇
  2017年   238篇
  2016年   230篇
  2015年   159篇
  2014年   229篇
  2013年   475篇
  2012年   251篇
  2011年   309篇
  2010年   235篇
  2009年   242篇
  2008年   237篇
  2007年   180篇
  2006年   174篇
  2005年   123篇
  2004年   97篇
  2003年   99篇
  2002年   86篇
  2001年   61篇
  2000年   74篇
  1999年   197篇
  1998年   1434篇
  1997年   850篇
  1996年   537篇
  1995年   343篇
  1994年   274篇
  1993年   293篇
  1992年   100篇
  1991年   83篇
  1990年   91篇
  1989年   96篇
  1988年   93篇
  1987年   80篇
  1986年   87篇
  1985年   101篇
  1984年   48篇
  1983年   59篇
  1982年   71篇
  1981年   75篇
  1980年   75篇
  1979年   46篇
  1978年   38篇
  1977年   121篇
  1976年   194篇
  1975年   28篇
  1974年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Wireless Personal Communications - In the present scenario, there is a boom in the demand of the users to achieve increased capacity, high data, low latency, and high-performance rates. 5G New...  相似文献   
2.

In this paper, we propose to use Artificial Bee Colony (ABC) optimization to solve the joint mode selection, channel assignment, and power allocation (JMSCPA) problem to maximize system throughput and spectral efficiency. JMSCPA is a problem where the allocation of channel and power depends on the mode selection. Such problems require two step solution and are called bi-level optimization problems. As bi-level optimization increases the complexity and computational time, we propose a modified version of single-level ABC algorithm aided with the adaptive transmission mode selection algorithm to allocate the cellular, reuse, and dedicated modes to the DUs along with channel and power allocation based on the network traffic load scenarios. A single variable, represented by the users (CUs and DUs) is used to allocate mode selection, and channel allocation to solve the JMSCPA problem, leading to a simpler solution with faster convergence, and significant reduction in the computational complexity which scales linearly with the number of users. Further, the proposed solution avoids premature stagnation of conventional ABC into local minima by incorporating a modification in its update procedure. The efficacy of the ABC-aided approach, as compared to the results reported in the literature, is validated by extensive numerical investigations under different simulation scenarios.

  相似文献   
3.
Multimedia Tools and Applications - In this paper, a hashing based watermarking technique for the protection and authentication of document image is proposed. Message Digest 5 (MD5) hashing is...  相似文献   
4.
Food Science and Biotechnology - The process of cellular senescence is rapidly emerging as a modulator of organismal aging and disease. Targeting the development and removal of senescent cells is...  相似文献   
5.

A fuzzy set based cost model for additive manufacturing is proposed. The model is illustrated through an example of selective laser sintering (SLS), a commonly used additive manufacturing (AM) process. Initially, a deterministic cost model is developed. It is then converted to a fuzzy set based model by considering uncertainty in build time estimation and cost components. For the specific case of SLS, a build time estimation procedure is developed as a part of the cost model. A method to evaluate the reliability of the cost estimate in AM and its significance is also introduced. The cost model is illustrated through two examples of products manufactured by SLS.

  相似文献   
6.
Wireless Personal Communications - This article presents a microstrip-fed octagonal shaped monopole antenna with dual band notched characteristics for UWB applications. Partial ground plane has...  相似文献   
7.
When Streptomyces violaceoruber grows together with Streptomyces sp. MG7-G1, it reacts with strongly induced droplet production on its aerial mycelium. Initially the metabolite profile of droplets from S. violaceoruber in co-culture with Streptomyces sp. MG7-G1 was compared to samples from S. violaceoruber in single-culture by using high-performance liquid chromatography-mass spectrometry (HPLC-MS). Then, the exudate from agar plates of co-cultures and single cultures (after freezing and thawing) was also analysed. Several compounds were only observed when S. violaceoruber was grown in co-culture. Based on their high-resolution ESI mass spectra and their comparable retention times to the calcium-dependent antibiotics (CDAs) produced by S. violaceoruber, the new compounds were suspected to be deacylated calcium-dependent antibiotics (daCDAs), lacking the 2,3-epoxyhexanoyl residue of CDAs. This was verified by detailed analysis of the MS/MS spectra of the daCDAs in comparison to the CDAs. The major CDA compounds present in calcium ion-supplemented agar medium of co-cultures were daCDAs, thus suggesting that Streptomyces sp. MG7-G1 expresses a deacylase that degrades CDAs.  相似文献   
8.
The principles and design of “active” self‐propelling particles that can convert energy, move directionally on their own, and perform a certain function is an emerging multidisciplinary research field, with high potential for future technologies. A simple and effective technique is presented for on‐demand steering of self‐propelling microdiodes that move electroosmotically on water surface, while supplied with energy by an external alternating (AC) field. It is demonstrated how one can control remotely the direction of diode locomotion by electronically modifying the applied AC signal. The swimming diodes change their direction of motion when a wave asymmetry (equivalent to a DC offset) is introduced into the signal. The data analysis shows that the ability to control and reverse the direction of motion is a result of the electrostatic torque between the asymmetrically polarized diodes and the ionic charges redistributed in the vessel. This novel principle of electrical signal‐coded steering of active functional devices, such as diodes and microcircuits, can find applications in motile sensors, MEMs, and microrobotics.  相似文献   
9.
10.
本实验采用4D-非标记蛋白质组学技术研究秦川牛肉贮藏过程中(0~8 d)肌红蛋白含量及其衍生物的转化情况,阐释冷却秦川牛肉中肌红蛋白含量及其衍生物转化的分子机制。结果表明:贮藏过程中,肌红蛋白表达量在宰后0~4 d上升、4~8 d下降,利用非标记蛋白质组学技术鉴定出与肌红蛋白及其衍生物相关的差异蛋白14 种,具体包括代谢酶、氧化还原酶、过氧化物酶、伴侣蛋白4 类,这4 类蛋白的表达共同调控贮藏过程中肌红蛋白含量的变化及其3 种衍生物之间的转化,具体表现为贮藏过程中肌红蛋白表达量整体呈下降趋势,氧合肌红蛋白相对含量持续下降,脱氧肌红蛋白、高铁肌红蛋白相对含量逐渐增加,导致肉色发生褐变。本研究结果有利于理解秦川牛肉贮藏过程肉类变色的复杂生化变化机制。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号