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   652507篇
  免费   9288篇
  国内免费   2110篇
电工技术   12293篇
综合类   589篇
化学工业   95691篇
金属工艺   25026篇
机械仪表   22278篇
建筑科学   17507篇
矿业工程   2022篇
能源动力   16855篇
轻工业   62877篇
水利工程   5686篇
石油天然气   4904篇
武器工业   16篇
无线电   82833篇
一般工业技术   123778篇
冶金工业   116656篇
原子能技术   8769篇
自动化技术   66125篇
  2021年   3965篇
  2020年   2856篇
  2019年   3624篇
  2018年   13575篇
  2017年   14295篇
  2016年   10429篇
  2015年   5426篇
  2014年   8328篇
  2013年   27745篇
  2012年   17071篇
  2011年   28934篇
  2010年   23716篇
  2009年   25035篇
  2008年   25765篇
  2007年   27853篇
  2006年   18383篇
  2005年   20267篇
  2004年   17990篇
  2003年   17301篇
  2002年   15758篇
  2001年   15641篇
  2000年   14425篇
  1999年   15338篇
  1998年   36190篇
  1997年   25909篇
  1996年   20014篇
  1995年   15507篇
  1994年   13710篇
  1993年   13336篇
  1992年   9730篇
  1991年   9273篇
  1990年   8747篇
  1989年   8378篇
  1988年   8091篇
  1987年   6709篇
  1986年   6558篇
  1985年   8081篇
  1984年   7473篇
  1983年   6626篇
  1982年   6100篇
  1981年   6164篇
  1980年   5742篇
  1979年   5455篇
  1978年   5063篇
  1977年   6151篇
  1976年   8129篇
  1975年   4267篇
  1974年   4044篇
  1973年   3969篇
  1972年   3121篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The data on the use of solar photovoltaic plants (PVPs) for providing a reliable and guaranteed power supply to telecommunication systems and cellular communication systems in the conditions prevalent in Uzbekistan are given. The research-based structures developed by OOO MIR SOLAR and the selection of PVP elements ensuring their reliable operation are described. The main influencing factors are discussed, and the use of effective combinations of different types of panels (from monocrystalline and polycrystalline silicon) and a specially developed controller are considered.  相似文献   
62.
This work presents simulation of microstructure evolution in the nugget zone (NZ) of a AZ31-Mg-alloy friction stir weld. The process parameters (tool geometrical characteristics, rotational speed, travel speed, applied load) have been correlated with the resulting microstructural features in the NZ of the weld (grain size and population) with the aid of the MICRESS software, which provides the ability to simulate both nucleation and grain growth during dynamic recrystallization phenomena evolving in the NZ during the weld thermal cycle. The input parameters of the developed model include the tool geometry, the welding conditions as well as the recrystallization energy, the grain boundary mobility and specific material properties. NZ microstructure obtained by simulation shows good agreement with experimental measurements for both grain population and size.  相似文献   
63.
64.
65.
66.
67.
This study evaluated several physical and sensory parameters of different types of cheese available in the Polish market. The measurements of textural properties were conducted in an Instron universal testing machine, while the colour properties of cheeses were measured using a Minolta chromameter. The chemical composition was determined by means of the near‐infrared spectroscopy (NIRs). Moreover, a trained sensory panel was invited to assess the cheese texture‐related properties. Generally, cheeses with reduced fat content were characterised by higher hardness, adhesiveness, cohesiveness and elasticity. Texture‐related parameters of cheese with canola oil were comparable to that of most of full‐fat cheeses. The correlation analysis between physical and sensory attributes related to cheese textural properties indicated the potential applications of TPA, shear and penetration tests (= 0.766, = 0.75 and = 0.765, respectively) for the evaluation of sensory properties related to the hardness. Meanwhile, the elasticity of cheese obtained from sensory evaluation was strongly correlated with the elasticity determined from the shear test (= 0.722) and moderately correlated with the elasticity from penetration test (= 0.588), indicating a need to refine the method of penetration test. In addition, cheeses exhibited higher meltability during convection heating at 230 °C than microwave heating. The values of meltability for cheese with reduced fat content were lower than those of full‐fat cheese.  相似文献   
68.
Phosphorodiamidate morpholino oligomers (PMOs) are oligonucleotide analogs that can be used for therapeutic modulation of pre‐mRNA splicing. Similar to other classes of nucleic acid‐based therapeutics, PMOs require delivery systems for efficient transport to the intracellular target sites. Here, artificial peptides based on the oligo(ethylenamino) acid succinyl‐tetraethylenpentamine (Stp), hydrophobic modifications, and an azide group are presented, which are used for strain‐promoted azide‐alkyne cycloaddition conjugation with splice‐switching PMOs. By systematically varying the lead structure and formulation, it is determined that the type of contained fatty acid and supramolecular assembly have a critical impact on the delivery efficacy. A compound containing linolenic acid with three cis double bonds exhibits the highest splice‐switching activity and significantly increases functional protein expression in pLuc/705 reporter cells in vitro and after local administration in vivo. Structural and mechanistic studies reveal that the lipopeptide PMO conjugates form nanoparticles, which accelerate cellular uptake and that the content of unsaturated fatty acids enhances endosomal escape. In an in vitro Duchenne muscular dystrophy exon skipping model using H2K‐mdx52 dystrophic skeletal myotubes, the highly potent PMO conjugates mediate significant splice‐switching at very low nanomolar concentrations. The presented aminoethylene‐lipopeptides are thus a promising platform for the generation of PMO‐therapeutics with a favorable activity/toxicity profile.  相似文献   
69.
70.
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