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   2156篇
  免费   188篇
  国内免费   14篇
电工技术   27篇
综合类   11篇
化学工业   511篇
金属工艺   59篇
机械仪表   56篇
建筑科学   34篇
矿业工程   3篇
能源动力   59篇
轻工业   152篇
水利工程   7篇
石油天然气   25篇
无线电   352篇
一般工业技术   423篇
冶金工业   235篇
原子能技术   4篇
自动化技术   400篇
  2023年   16篇
  2022年   29篇
  2021年   50篇
  2020年   38篇
  2019年   61篇
  2018年   41篇
  2017年   63篇
  2016年   73篇
  2015年   60篇
  2014年   98篇
  2013年   195篇
  2012年   114篇
  2011年   130篇
  2010年   115篇
  2009年   123篇
  2008年   93篇
  2007年   115篇
  2006年   88篇
  2005年   64篇
  2004年   61篇
  2003年   42篇
  2002年   52篇
  2001年   41篇
  2000年   36篇
  1999年   48篇
  1998年   79篇
  1997年   56篇
  1996年   55篇
  1995年   27篇
  1994年   30篇
  1993年   32篇
  1992年   21篇
  1991年   38篇
  1990年   22篇
  1989年   19篇
  1988年   17篇
  1987年   9篇
  1986年   6篇
  1985年   13篇
  1984年   4篇
  1983年   11篇
  1982年   8篇
  1981年   10篇
  1980年   5篇
  1979年   6篇
  1978年   6篇
  1977年   5篇
  1976年   11篇
  1974年   3篇
  1973年   6篇
排序方式: 共有2358条查询结果,搜索用时 0 毫秒
31.
A new kind of terpolymer membrane was employed to separate a permselective water–alcohol mixture. This membrane was prepared via the copolymerization of acrylonitrile, sodium salt styrene sulfonic acid (SStSA), and hydroxyethyl methacrylate in dimethylsulfoxide with azobisisobutyronitrile as an initiator. The reaction mechanism, resultant structure, and polymer composition were confirmed by IR and elemental analysis. The effects of the feed composition on the polymer composition, mechanical properties, thermal properties, and degree of swelling were investigated. It was found that water permeated through the membrane preferentially in a water/alcohol system. The flux increased with the increase of SStSA, but the separation factor decreased drastically with higher SStSA. For a 50 wt % water–ethanol mixture, a flux of 0.65 kg/m2 h and a separation factor of 212 were obtained at 30°C when the membrane containing the highest SStSA content was used. The capacities of the metal ions absorbed by the membranes were investigated in the study. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 244–250, 2003  相似文献   
32.
Bioremediation strategies have been applied to clean up petroleum hydrocarbon (PHC) impacted sites. Introducing PHC degrading microorganisms (bioaugmentation) and enhancing the in‐situ nutrients availability (biostimulation) are widely used strategies. These strategies can be combined to lead to a better bioremediation performance. In this work, Pseudomonas fluorescens was isolated from a PHC impacted site. Through a 23 factorial design plan, the effect of various combinations of nitrate, sulphate, and phosphate ions on the PHC bioremediation performance by P. fluorescens was investigated using catechol, an essential metabolic intermediate of BTEX degradation, as the sole carbon source. The maximum specific catechol degradation rate was chosen as the response to evaluate the catechol bioremediation performance. The ANOVA results indicated that the presence of nitrate ions alone lowered the maximum specific catechol degradation rate, which can be explained by the accumulation of nitrites and ammonia during the denitrification process by P. fluorescens. It was noted that dosing sulphate ions alone did not affect the bioremediation performance, which indicates P. fluorescens can grow in a sulphur‐limited environment. In contrast, the presence of sulphate and nitrate ions together can lead to a higher specific catechol degradation rate. This may be caused by the presence of sulphate that can suppress the production of nitrites. The importance of phosphate ions on catechol biodegradation was investigated. The absence of phosphate led to incomplete biodegradation. Introducing phosphate ions can accelerate catechol degradation, which can be explained by the secretion of organic acids.  相似文献   
33.
计算机图象法是计算机应用的新发展。本文对微计算机图象法在焊接领域中的应用作了一些探索。研究和配置了不同分辨力的图象输入接口(8BIT、4BIT、二化值),并进行了焊接图象处理、模式识别和反馈自动控制方面的研究。简介了采用微计算机图象法在焊接过程中面积和尺寸形状的测量、焊接温度场测定、焊缝X 光底片判断、焊缝对中等方面的研究工作,从而证明计算机图象法在焊接领域中具有广阔的前途.  相似文献   
34.
A microstrip‐fed conventional annular ring slot (ARS) antenna with linear polarization (LP) is initially studied. To generate two orthogonal degenerate modes for circular polarization (CP) radiations, two identical meandering perturbation slots (MPS) are symmetrically loaded into the ARS. By further incorporating a PIN diode switch across each MPS, the proposed antenna can switch between left‐hand CP (LHCP), right‐hand CP (RHCP), and LP. All three polarizations have shown good impedance bandwidth and broad CP bandwidth that can satisfy the wireless local area network (WLAN) 2.4‐GHz operating band (2400–2480 MHz). Furthermore, desirable gains of 1.8–2.0 dBi and 2.40–2.84 dBic are also exhibited at LP and LHCP/RHCP, respectively. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:110–120, 2016.  相似文献   
35.
36.
We adapted a model in organizational theory to determine whether organizational citizenship behaviors (OCBs) of system implementation teams influenced that organization's integration climate and improved their project management, resulting in successful system implementation. Surveys were elicited from 254 system users in various business organizations that had implemented large-scale IS in the previous year; the analysis of their responses provided support for our model, suggesting that the OCB of the implementation team created a higher level of integration climate and more effective project management, and that these in turn influenced information system success. Implications for researchers and managers are discussed and limitations are identified.  相似文献   
37.
The presented paper describes a novel process using inkjet printing to pattern a conformal (built-on) mask onto photoresist for further microstructure formation. The advantages of using the inkjet printing conformal mask include no Cr photomask required, suitable for non-planar substrate, scalable for large area, and extreme low cost. The ink is ejected from the inkjet print-head controlled by the inkjet system. A CAD pattern from the designer can use this process to place the pattern ink onto the photoresist substrate. A conformal mask (made of ink) was directly built-on the photoresist substrate. The dried ink thickness has to be more than 1.8 μm thick as UV absorber. Following UV exposure, development, and ink removal, the designed microstructure patterns can be realized in photoresist such as microchannels and micro-columns.  相似文献   
38.
Dynamic Multiple Swarms in Multiobjective Particle Swarm Optimization   总被引:2,自引:0,他引:2  
A multiple-swarm multiobjective particle swarm optimization (PSO) algorithm, named dynamic multiple swarms in multiobjective PSO, is proposed in which the number of swarms is adaptively adjusted throughout the search process via the proposed dynamic swarm strategy. The strategy allocates an appropriate number of swarms as required to support convergence and diversity criteria among the swarms. Additional novel designs include a PSO updating mechanism to better manage the communication within a swarm and among swarms and an objective space compression and expansion strategy to progressively exploit the objective space during the search process. Comparative study shows that the performance of the proposed algorithm is competitive in comparison to the selected algorithms on standard benchmark problems. In particular, when dealing with test problems with multiple local Pareto fronts, the proposed algorithm is much less computationally demanding. Sensitivity analysis indicates that the proposed algorithm is insensitive to most of the user-specified design parameters.  相似文献   
39.
Including: Neural Networks Pioneer Vladimir Vapnik, NEC Research, Inc., USA. Fuzzy Systems Pioneer Hideo Tanaka, Hiroshima International University, JAPAN. Evolutionary Computation Pioneer David E. Goldberg, University of Illinois at Urbana Champaign, USA and John Grefenstette, George Mason University, USA. Meritorious Services James M. Keller, University of Missouri, USA. IEEE Transactions on Fuzzy Systems Outstanding Paper, IEEE Transactions on Evolutionary Computation Outstanding Paper, Outstanding Chapter, Outstanding Ph.D. Dissertation. Also past CIS Neural Networks Pioneer Awardees, Fuzzy Systems Pioneer Awardees, Evolutionary Computation Pioneer Awardees and Meritorious Service Awardees.  相似文献   
40.
Responsive nanomaterials have emerged as promising candidates as drug delivery vehicles in order to address biomedical diseases such as cancer. In this work, polymer‐based responsive nanoparticles prepared by a supramolecular approach are loaded with doxorubicin (DOX) for the cancer therapy. The nanoparticles contain disulfide bonds within the polymer network, allowing the release of the DOX payload in a reducing environment within the endoplasm of cancer cells. In addition, the loaded drug can also be released under acidic environment. In vitro anticancer studies using redox and pH dual responsive nanoparticles show excellent performance in inducing cell death and apoptosis. Zebrafish larvae treated with DOX‐loaded nanoparticles exhibit an improved viability as compared with the cases treated with free DOX by the end of a 3 d treatment. Confocal imaging is utilized to provide the daily assessment of tumor size on zebrafish larva models treated with DOX‐loaded nanoparticles, presenting sustainable reduction of tumor. This work demonstrates the development of functional nanoparticles with dual responsive properties for both in vitro and in vivo drug delivery in the cancer therapy.  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