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   303404篇
  免费   3629篇
  国内免费   1103篇
电工技术   6237篇
综合类   1380篇
化学工业   44640篇
金属工艺   12241篇
机械仪表   10448篇
建筑科学   7709篇
矿业工程   1717篇
能源动力   6826篇
轻工业   24966篇
水利工程   3191篇
石油天然气   5064篇
武器工业   82篇
无线电   40477篇
一般工业技术   57514篇
冶金工业   51137篇
原子能技术   5828篇
自动化技术   28679篇
  2022年   4231篇
  2021年   5471篇
  2020年   4143篇
  2019年   5189篇
  2018年   4544篇
  2017年   4197篇
  2016年   4086篇
  2015年   2635篇
  2014年   4422篇
  2013年   12113篇
  2012年   7130篇
  2011年   10468篇
  2010年   8240篇
  2009年   9215篇
  2008年   9426篇
  2007年   9360篇
  2006年   8585篇
  2005年   8131篇
  2004年   8925篇
  2003年   8597篇
  2002年   8292篇
  2001年   8030篇
  2000年   7201篇
  1999年   7082篇
  1998年   15054篇
  1997年   10981篇
  1996年   8581篇
  1995年   6809篇
  1994年   6263篇
  1993年   5964篇
  1992年   4924篇
  1991年   4463篇
  1990年   4355篇
  1989年   4162篇
  1988年   3969篇
  1987年   3429篇
  1986年   3434篇
  1985年   3928篇
  1984年   3645篇
  1983年   3332篇
  1982年   3133篇
  1981年   3172篇
  1980年   2920篇
  1979年   2808篇
  1978年   2733篇
  1977年   3217篇
  1976年   3755篇
  1975年   2540篇
  1974年   2483篇
  1973年   2429篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  相似文献   
2.

Stability constants and formation enthalpies of supramolecular complexes of crown ethers and their cyclic and acyclic analogues are determined on the basis of experimental data obtained by different physicochemical methods in the terms of a general approach developed and implemented in the ChemEqui software package. The established regularities of variation of stability of complexes are discussed as dependent on the ligand structure, nature of the cation, solvent, and anion. The applicability of the suggested method of determining complexation selectivity is shown for multicomponent equilibria in solutions.

  相似文献   
3.
4.
Here we report some recent biophysical issues on the preparation of solute-filled lipid vesicles and their relevance to the construction of “synthetic cells.” First, we introduce the “semi-synthetic minimal cells” as the liposome-based cell-like systems, which contain a minimal number of biomolecules required to display simple and complex biological functions. Next, we focus on recent aspects related to the construction of synthetic cells. Emphasis is given to the interplay between the methods of synthetic cell preparation and the physics of solute encapsulation. We briefly introduce the notion of structural and compositional “diversity” in synthetic cell populations.  相似文献   
5.
The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g?1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL?1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL?1) compared to the control (61 ± 2.83 Miller units mL?1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus.  相似文献   
6.
7.
8.

To increase the efficiency of designing systems intended for monitoring surface cracks in aluminum structures during their working life, we have analyzed a two-dimensional symmetric problem on uniaxial extension of an Al-polyimide-Cu layered structure with ideal adhesion between layers and a model crack in the aluminum base. The problem has been first solved for a sample with the crack modeled by a zero-thickness notch using the ANSYS engineering simulation program package. It is shown that this setting of the problem can lead to inadequate results as manifested, in particular, by significantly overstated mechanical stresses in aluminum in the region of crack emergence on the surface. In order to eliminate this difficulty, we propose to use the structure with a model defect in the form of a notch of nonzero thickness in the initial unstressed state of the structure. Recommendations for selecting the thickness of a notch used in the model structure are given.

  相似文献   
9.
10.
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