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   16380篇
  免费   124篇
  国内免费   478篇
电工技术   243篇
综合类   79篇
化学工业   1744篇
金属工艺   595篇
机械仪表   897篇
建筑科学   968篇
矿业工程   319篇
能源动力   100篇
轻工业   3297篇
水利工程   357篇
石油天然气   301篇
武器工业   69篇
无线电   844篇
一般工业技术   5888篇
冶金工业   326篇
原子能技术   169篇
自动化技术   786篇
  2022年   28篇
  2021年   42篇
  2018年   19篇
  2016年   28篇
  2015年   44篇
  2014年   55篇
  2013年   77篇
  2012年   1755篇
  2011年   2294篇
  2010年   482篇
  2009年   234篇
  2008年   1461篇
  2007年   1384篇
  2006年   1142篇
  2005年   1008篇
  2004年   869篇
  2003年   692篇
  2002年   663篇
  2001年   526篇
  2000年   555篇
  1999年   369篇
  1998年   208篇
  1997年   184篇
  1996年   167篇
  1995年   139篇
  1994年   159篇
  1993年   126篇
  1992年   121篇
  1991年   153篇
  1990年   152篇
  1989年   153篇
  1988年   125篇
  1987年   142篇
  1986年   115篇
  1985年   153篇
  1984年   149篇
  1983年   154篇
  1982年   137篇
  1981年   105篇
  1980年   98篇
  1979年   98篇
  1978年   52篇
  1977年   24篇
  1976年   33篇
  1975年   33篇
  1974年   25篇
  1973年   18篇
  1965年   25篇
  1964年   25篇
  1958年   20篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
被处理的工件直接真空淬油,则无需进行清洗或精加工,该工艺称为“光亮淬火”。此工艺之所以得到发展是由于其经济性好。加热期间采用保护气(氩、氮氢化合物)  相似文献   
992.
不同浓度的~(131)I-Lym-2 MoAb与ARH-77和CEM细胞进行结合试验,结果表明:随浓度增大,结合值均升高;实验组裸鼠模型9只获得动力学数据。实验组和对照组注射~(131)I-Lym-2 MoAb后144h解剖,进行生物学分布(%D/g)测定,实验组肿瘤为16.88±12.64,肌肉为0.72±0.56。结果表明,~(131)I-131-Lym-2MoAb对临床B细胞淋巴瘤的放射免疫分析、显像有良好的效果。  相似文献   
993.
1.引言 目前轧钢生产者们正面对提高产品质量及降低生产成本的要求,绝大多数热带钢轧机需要进行专门改造以保证其市场竞争能力。通常,改造工作的目标如下: —减少加工成本 —提高生产率 —降低损耗 —增加产量,主要通过: *减少铁鳞损失 *将切头切尾长度减至最小 *将宽度方向公差减至最小 —质量改进,有关: *厚度公差  相似文献   
994.
We report on our prototype experiment that uses a 4-m detuned resonant sideband extraction interferometer with suspended mirrors, which has almost the same configuration as the next-generation, gravitational-wave detectors. We have developed a new control scheme and have succeeded in the operation of such an interferometer with suspended mirrors for the first time ever as far as we know. We believe that this is the first such instrument that can see the radiation pressure signal enhancement, which can improve the sensitivity of next-generation gravitational-wave detectors.  相似文献   
995.
Xu P  Brissaud F  Fazio A 《Water research》2002,36(12):3074-3082
In Noirmoutier, a French island off the Atlantic coast, secondary effluents flow into a series of four lagoons, 1.4-2.8 m deep, and are reused for agricultural irrigation. The excess water is disposed of to the sea. The aim of this study was to provide a model capable of predicting the microbiological quality of the water pumped for irrigation or discharged to the sea. Meteorological variables, flow rates, physical-chemical characteristics and faecal coliform (FC) contents were monitored for a year and a half. The hydraulic pattern of each lagoon was assumed to be that of completely mixed reactor because of the calculated dispersion numbers and the wind mixing effect. Coliform decay was assumed to follow first order kinetics in each lagoon. Die-off coefficients were calculated in each lagoon using a non-steady-state model. The main bacterial removal mechanism was shown to be solar irradiation. Empirical equations were established to calculate die-off coefficients as a function of received solar energy and temperature. FC die-off rates were higher in the first lagoon and then decreased successively in those following. FC numbers in the different lagoons were predicted with reasonable accuracy in spite of high variation in inlet water quality. The model will facilitate the prediction of water quality under various climatic conditions and different water reuse scenarios and will help to optimise reclamation and storage facilities.  相似文献   
996.
Because of its high reaction rate and specificity, the enzyme superoxide dismutase (SOD) offers great potential for the sensitive quantification of superoxide radicals in electrochemical biosensors. In this work, monomeric mutants of human Cu,Zn-SOD were engineered to contain one or two additional cysteine residues, which could be used to bind the protein to gold surfaces, thus making the use of promotor molecules unnecessary. Six mutants were successfully designed, expressed, and purified. All mutants bound directly to unmodified gold surfaces via the sulfur of the cysteine residues and showed a quasi-reversible, direct electron transfer to the electrode. Thermodynamic and kinetic parameters of the electron transfer were characterized and showed only slight variations between the individual mutants. For one of the mutants, the interaction with the superoxide radical was studied in more detail. For both partial reactions of the dismutation, an interaction between protein and radical could be shown. In an amperometric biosensorial approach, the SOD-mutant electrode was successfully applied for the detection of superoxide radicals. In the oxidation region, the electrode surpassed the sensitivity of the commonly used cytochrome c electrodes by approximately 1 order of magnitude while not being limited by interferences, but the electrode did not fully reach the sensitivity of dimeric Cu,Zn-SOD immobilized on MPA-modified gold.  相似文献   
997.
998.
Diffusion tensor imaging is of high value in neurosurgery, providing information about the location of white matter tracts in the human brain. For their reconstruction, streamline techniques commonly referred to as fiber tracking model the underlying fiber structures and have therefore gained interest. To meet the requirements of surgical planning and to overcome the visual limitations of line representations, a new real-time visualization approach of high visual quality is introduced. For this purpose, textured triangle strips and point sprites are combined in a hybrid strategy employing GPU programming. The triangle strips follow the fiber streamlines and are textured to obtain a tube-like appearance. A vertex program is used to orient the triangle strips towards the camera. In order to avoid triangle flipping in case of fiber segments where the viewing and segment direction are parallel, a correct visual representation is achieved in these areas by chains of point sprites. As a result, a high quality visualization similar to tubes is provided allowing for interactive multimodal inspection. Overall, the presented approach is faster than existing techniques of similar visualization quality and at the same time allows for real-time rendering of dense bundles encompassing a high number of fibers, which is of high importance for diagnosis and surgical planning.  相似文献   
999.
SAW COM-parameter extraction in AlN/diamond layered structures   总被引:1,自引:0,他引:1  
Highly c-axis oriented aluminum nitride (AlN) thin piezoelectric films have been grown on polycrystalline diamond substrates by pulsed direct current (DC) magnetron reactive sputter-deposition. The films were deposited at a substrate temperature below 50/spl deg/C (room temperature) and had a typical full width half maximum (FWHM) value of the rocking curve of the AlN-002-peak of 2.1 degrees. A variety of one-port surface acoustic wave (SAW) resonators have been designed and fabricated on top of the AlN films. The measurements indicate that various SAW modes are excited. The SAW phase velocities of up to 11.800 m/s have been measured. These results are in agreement with calculated dispersion curves of the AlN/diamond structure. Finally, the coupling of modes parameters have been extracted from S/sub 11/ measurements using curve fitting for the first SAW mode, which indicate an effective coupling K/sup 2/ of 0.91% and a Q factor of about 600 at a frequency of 1050 MHz.  相似文献   
1000.
This paper addresses in an integrated and systematic fashion the relatively overlooked but increasingly important issue of measuring and characterizing the geometrical properties of nerve cells and structures, an area often called neuromorphology. After discussing the main motivation for such an endeavour, a comprehensive mathematical framework for characterizing neural shapes, capable of expressing variations over time, is presented and used to underline the main issues in neuromorphology. Three particularly powerful and versatile families of neuromorphological approaches, including differential measures, symmetry axes/skeletons, and complexity, are presented and their respective potentials for applications in neuroscience are identified. Examples of applications of such measures are provided based on experimental investigations related to automated dendrogram extraction, mental retardation characterization, and axon growth analysis.  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