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   312770篇
  免费   28602篇
  国内免费   17988篇
电工技术   46313篇
技术理论   38篇
综合类   31484篇
化学工业   22450篇
金属工艺   11407篇
机械仪表   22346篇
建筑科学   28760篇
矿业工程   11022篇
能源动力   23381篇
轻工业   11383篇
水利工程   8713篇
石油天然气   9666篇
武器工业   4628篇
无线电   29111篇
一般工业技术   22159篇
冶金工业   10428篇
原子能技术   3723篇
自动化技术   62348篇
  2024年   962篇
  2023年   4104篇
  2022年   6976篇
  2021年   8822篇
  2020年   9344篇
  2019年   7482篇
  2018年   6683篇
  2017年   8708篇
  2016年   9939篇
  2015年   10989篇
  2014年   20122篇
  2013年   17874篇
  2012年   23119篇
  2011年   24925篇
  2010年   18842篇
  2009年   18807篇
  2008年   18702篇
  2007年   23017篇
  2006年   20260篇
  2005年   17615篇
  2004年   14548篇
  2003年   12904篇
  2002年   10070篇
  2001年   8482篇
  2000年   7081篇
  1999年   5717篇
  1998年   4328篇
  1997年   3526篇
  1996年   3118篇
  1995年   2583篇
  1994年   2165篇
  1993年   1540篇
  1992年   1278篇
  1991年   968篇
  1990年   774篇
  1989年   650篇
  1988年   478篇
  1987年   309篇
  1986年   202篇
  1985年   247篇
  1984年   201篇
  1983年   159篇
  1982年   155篇
  1981年   105篇
  1980年   105篇
  1979年   73篇
  1978年   53篇
  1977年   44篇
  1976年   32篇
  1959年   27篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
161.
This study was designed to evaluate the acid stability, release property and antimicrobial efficacy of Escherichia coli O157:H7 bacteriophages encapsulated in chitosan–alginate microspheres under the simulated gastrointestinal conditions. The bacteriophages belonging to Myoviridae family were stable at the pH above 4 in trypticase soy broth. The chitosan–alginate microspheres exhibited protective effect on the viability of bacteriophages in the simulated gastric conditions at pH 2.0 and pH 2.5, showing 4.8 and 5.6 log PFU mL‐1, respectively, after 1 h of incubation at 37 °C. The release per cent of bacteriophages from microspheres gradually increased up to 65% in the simulated intestinal condition (pH 7.5) at 37 °C for 6 h. The lytic efficacy of chitosan‐ and alginate‐encapsulated bacteriophages against Ecoli O157:H7 was significantly maintained in the simulated intestinal conditions to 10 h of incubation (1.3 log reduction). The results suggest that the chitosan–alginate microspheres can be used as a reliable delivery system for bacteriophages.  相似文献   
162.
计算机录入编辑盲文是信息处理的特殊应用领域,是特殊教育中的重要研究课题。文中将盲文制作为特殊符号,通过制作字库,编写个性化码表,然后嵌入到主流输入法,从而实现盲文与汉字混排以及实现单手盲文输入。该系统具有易学易记性、盲文编码多样性、嵌入性强等优点,并通过实验证明输入盲文效率能提高5~6倍,在盲文出版、盲文印刷、盲文教学等领域有重要的应用价值。但盲文字符在不同平台(如智能手机)与不同操作系统兼容性问题还有待进一步研究开发。  相似文献   
163.
To improve the electrochemical properties of rare-earth–Mg–Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the ...  相似文献   
164.
李中望 《电镀与涂饰》2021,40(4):269-273
针对电镀液温度控制系统,引入状态反馈控制。相对于传统的反馈控制,本方法可以获得更优异的性能。另外,考虑到镀液温度控制具有纯迟延的特点,提出了一种消去纯迟延的方法。仿真验证结果显示,控制效果良好。  相似文献   
165.
Processing lithium-ion battery (LIB) electrode dispersions with water as the solvent during primary drying offers many advantages over N-methylpyrrolidone (NMP). An in-depth analysis of the comparative drying costs of LIB electrodes is discussed for both NMP- and water-based dispersion processing in terms of battery pack $/kWh. Electrode coating manufacturing and capital equipment cost savings are compared for water vs. conventional NMP organic solvent processing. A major finding of this work is that the total electrode manufacturing costs, whether water- or NMP-based, contribute about 8–9% of the total pack cost. However, it was found that up to a 2?×?reduction in electrode processing (drying and solvent recovery) cost can be expected along with a $3–6?M savings in associated plant capital equipment (for a plant producing 100,000 10-kWh Plug-in Hybrid Electric Vehicle (PHEV) batteries) using water as the electrode solvent. This paper shows a different perspective in that the most important benefits of aqueous electrode processing actually revolve around capital equipment savings and environmental stewardship and not processing cost savings.  相似文献   
166.
This paper considers a novel distributed iterative learning consensus control algorithm based on neural networks for the control of heterogeneous nonlinear multiagent systems. The system's unknown nonlinear function is approximated by suitable neural networks; the approximation error is countered by a robust term in the control. Two types of control algorithms, both of which utilize distributed learning laws, are provided to achieve consensus. In the provided control algorithms, the desired reference is considered to be an unknown factor and then estimated using the associated learning laws. The consensus convergence is proven by the composite energy function method. A numerical simulation is ultimately presented to demonstrate the efficacy of the proposed control schemes.  相似文献   
167.
168.
The use of geothermal energy and its associated technologies has been increasing worldwide. However, there has been little paradigmatic research conducted in this area. This paper proposes a systematic methodology to research the development trends for the sustainable development of geothermal energy. A novel data analysis system was created to research the geothermal energy utilization trends, and a technological paradigm theory was adopted to explain the technological changes. A diffusion velocity model was used to simulate and forecast the geothermal power generation development in the diffusion phase. Simulation results showed that the development of installed capacity for geothermal generation had a strong inertia force along with the S-curve. Power generation from geothermal power sources reached a peak in 2008 and is estimated to be saturated by 2030. Geothermal energy technologies in hybrid power systems based on other renewable energy sources look to be more promising in the future.  相似文献   
169.
Honey powders produced by spray drying with the addition of Arabic gum and sodium caseinate were characterised in terms of the influence of storage time on the following physical properties: particle size, moisture content, water activity, bulk density, flowability and hygroscopicity. The storage affected those properties; after 12 weeks of storage, particle size decreased (except Arabic gum powder treated as a control sample), moisture content and water activity increased, hygroscopicity decreased. Changes in bulk density, particle size and moisture content caused the rise of Hausner ratio value; however, the powders were still characterised by a very good flow properties and low cohesiveness. The colour of reconstituted powders was also affected by storage; in most of samples, the darkening, reduction in redness and yellowness were observed. Colour parameters were the most stable in powders obtained with the addition of 2% w/w of sodium caseinate.  相似文献   
170.
In this paper, the development of the models for the prediction of rock mass P wave velocity is presented. For model development, the database of 53 cases including widely used and recorded drilling parameters and P wave velocity was constructed from the field studies conducted in 13 open pit lignite mines. Both conventional linear, non-linear multiple regression and Adaptive Neuro Fuzzy Inference System (ANFIS) were used for model development. Prediction performance indicators showed that ANFIS model presented the best performance and it can successfully be used for the preliminary prediction of P wave velocities of rock masses.  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