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   449339篇
  免费   3298篇
  国内免费   1706篇
电工技术   7766篇
综合类   668篇
化学工业   66174篇
金属工艺   19395篇
机械仪表   13977篇
建筑科学   9803篇
矿业工程   3319篇
能源动力   10940篇
轻工业   33156篇
水利工程   5568篇
石油天然气   11976篇
武器工业   64篇
无线电   50895篇
一般工业技术   92951篇
冶金工业   80247篇
原子能技术   12258篇
自动化技术   35186篇
  2021年   3994篇
  2019年   4016篇
  2018年   6545篇
  2017年   6699篇
  2016年   7190篇
  2015年   4341篇
  2014年   7327篇
  2013年   19076篇
  2012年   11602篇
  2011年   15565篇
  2010年   12266篇
  2009年   13976篇
  2008年   14342篇
  2007年   14288篇
  2006年   12304篇
  2005年   11356篇
  2004年   10941篇
  2003年   10615篇
  2002年   10278篇
  2001年   10445篇
  2000年   9839篇
  1999年   10186篇
  1998年   25077篇
  1997年   17692篇
  1996年   13568篇
  1995年   10346篇
  1994年   9076篇
  1993年   9313篇
  1992年   6860篇
  1991年   6655篇
  1990年   6393篇
  1989年   6378篇
  1988年   6092篇
  1987年   5428篇
  1986年   5484篇
  1985年   6061篇
  1984年   5663篇
  1983年   5312篇
  1982年   4836篇
  1981年   4886篇
  1980年   4920篇
  1979年   4731篇
  1978年   4759篇
  1977年   5129篇
  1976年   6473篇
  1975年   4164篇
  1974年   4054篇
  1973年   4113篇
  1972年   3548篇
  1971年   3186篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The value of flexible videoendoscopy as a biofeedback tool in conservative swallowing rehabilitation of patients suffering from aspiration after head and neck surgery was examined. For this purpose, the outcomes of conventional swallowing therapy and of swallowing therapy with support of videoendoscopic biofeedback were compared. In the first 40 days of swallowing therapy, videoendoscopic biofeedback significantly increased the chance of therapeutic success, shortening the period of functional rehabilitation in comparison to conventional swallowing therapy. Limitations of this visual biofeedback procedure are poor cognitive skills of the patient, rejection of the procedure by the patient and local factors that make the positioning of the endoscope difficult.  相似文献   
52.
Implementing a neural network on a digital or mixed analog and digital chip yields the quantization of the synaptic weights dynamics. This paper addresses this topic in the case of Kohonen's self-organizing maps. We first study qualitatively how the quantization affects the convergence and the properties, and deduce from this analysis the way to choose the parameters of the network (adaptation gain and neighborhood). We show that a spatially decreasing neighborhood function is far more preferable than the usually rectangular neighborhood function, because of the weight quantization. Based on these results, an analog nonlinear network, integrated in a standard CMOS technology, and implementing this spatially decreasing neighborhood function is then presented. It can be used in a mixed analog and digital circuit implementation.  相似文献   
53.
Pipelining and bypassing in a VLIW processor   总被引:1,自引:0,他引:1  
This short note describes issues involved in the bypassing mechanism for a very long instruction word (VLIW) processor and its relation to the pipeline structure of the processor. The authors first describe the pipeline structure of their processor and analyze its performance and compare it to typical RISC-style pipeline structures given the context of a processor with multiple functional units. Next they study the performance effects of various bypassing schemes in terms of their effectiveness in resolving pipeline data hazards and their effect on the processor cycle time  相似文献   
54.
55.
56.
57.
The deletion of nine residues from the C-terminus of the bacterialchloramphenicol acetyltransferase (CAT) results in depositionof the mutant protein in cytoplasmic inclusion bodies and lossof chloramphenicol resistance in Escherichia coli. This foldingdefect is relieved by C-terminal fusion of the polypeptide withas few as two residues. Based on these observations, efficientpositive selection for the cloning of DNA fragments has beendemonstrated. The cloning vector encodes a C-terminally truncatedCAT protein. Restriction sites in front of the stop codon allowthe insertion of target DNA, resulting in the production ofproperly folded CAT fusion proteins and regained chloramphenicolresistance. The positive selection of recombinants is accomplishedby growth of transformants on chloramphenicol-containing agarplates. The method appears particularly convenient for the cloningof DNA fragments amplified by the PCR because minimal informationto restore CAT folding can be included in the primers. The cloningof random sequences shows that the folding defect can be relievedby fusion to a wide variety of peptides, providing great flexibilityto the positive selection system. This vector may also contributeto the determination of the role of the C-terminus in CAT folding.  相似文献   
58.
This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate.  相似文献   
59.
The effectiveness of the hybrid system sonication followed by wet oxidation (SONIWO) to treat otherwise refractory waste has been demonstrated. In such a hybrid system homogeneous CuSO4 catalyst was found to be very efficient.  相似文献   
60.
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described.  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