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   22701篇
  免费   1014篇
  国内免费   47篇
电工技术   336篇
综合类   42篇
化学工业   4589篇
金属工艺   572篇
机械仪表   444篇
建筑科学   1098篇
矿业工程   164篇
能源动力   668篇
轻工业   2544篇
水利工程   189篇
石油天然气   69篇
无线电   1674篇
一般工业技术   4065篇
冶金工业   3569篇
原子能技术   138篇
自动化技术   3601篇
  2023年   179篇
  2022年   223篇
  2021年   461篇
  2020年   334篇
  2019年   361篇
  2018年   519篇
  2017年   507篇
  2016年   577篇
  2015年   482篇
  2014年   713篇
  2013年   1442篇
  2012年   1010篇
  2011年   1357篇
  2010年   957篇
  2009年   1009篇
  2008年   1090篇
  2007年   1022篇
  2006年   857篇
  2005年   822篇
  2004年   665篇
  2003年   604篇
  2002年   581篇
  2001年   372篇
  2000年   341篇
  1999年   364篇
  1998年   409篇
  1997年   341篇
  1996年   358篇
  1995年   341篇
  1994年   317篇
  1993年   283篇
  1992年   276篇
  1991年   181篇
  1990年   251篇
  1989年   225篇
  1988年   186篇
  1987年   187篇
  1986年   175篇
  1985年   202篇
  1984年   214篇
  1983年   176篇
  1982年   182篇
  1981年   182篇
  1980年   157篇
  1979年   176篇
  1978年   131篇
  1977年   130篇
  1976年   174篇
  1975年   136篇
  1973年   122篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
1.
2.
Reliable prediction of flooding conditions is needed for sizing and operating packed extraction columns. Due to the complex interplay of physicochemical properties, operational parameters and the packing-specific properties, it is challenging to develop accurate semi-empirical or rigorous models with a high validity range. State of the art models may therefore fail to predict flooding accurately. To overcome this problem, a data-driven model based on Gaussian processes is developed to predict flooding for packed liquid-liquid and high-pressure extraction columns. The optimized Gaussian process for the liquid-liquid extraction column results in an average absolute relative error (AARE) of 15.23 %, whereas the algorithm for the high-pressure extraction column results in an AARE of 13.68 %. Both algorithms can predict flooding curves for different packing geometries and chemical systems precisely.  相似文献   
3.
Number entry is a ubiquitous activity and is often performed in safety- and mission-critical procedures, such as healthcare, science, finance, aviation and in many other areas. We show that Monte Carlo methods can quickly and easily compare the reliability of different number entry systems. A surprising finding is that many common, widely used systems are defective, and induce unnecessary human error. We show that Monte Carlo methods enable designers to explore the implications of normal and unexpected operator behaviour, and to design systems to be more resilient to use error. We demonstrate novel designs with improved resilience, implying that the common problems identified and the errors they induce are avoidable.  相似文献   
4.
5.
The diagnosis and treatment of prostate cancer (PCa) is a major health-care concern worldwide. This cancer can manifest itself in many distinct forms and the transition from clinically indolent PCa to the more invasive aggressive form remains poorly understood. It is now universally accepted that glycan expression patterns change with the cellular modifications that accompany the onset of tumorigenesis. The aim of this study was to investigate if differential glycosylation patterns could distinguish between indolent, significant, and aggressive PCa. Whole serum N-glycan profiling was carried out on 117 prostate cancer patients’ serum using our automated, high-throughput analysis platform for glycan-profiling which utilizes ultra-performance liquid chromatography (UPLC) to obtain high resolution separation of N-linked glycans released from the serum glycoproteins. We observed increases in hybrid, oligomannose, and biantennary digalactosylated monosialylated glycans (M5A1G1S1, M8, and A2G2S1), bisecting glycans (A2B, A2(6)BG1) and monoantennary glycans (A1), and decreases in triantennary trigalactosylated trisialylated glycans with and without core fucose (A3G3S3 and FA3G3S3) with PCa progression from indolent through significant and aggressive disease. These changes give us an insight into the disease pathogenesis and identify potential biomarkers for monitoring the PCa progression, however these need further confirmation studies.  相似文献   
6.
7.
8.
A contact layer element for large deformations   总被引:1,自引:0,他引:1  
  相似文献   
9.
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations...  相似文献   
10.
Combined photochemical arylation, “nuisance effect” (SNAr) reaction sequences have been employed in the design of small arrays for immediate deployment in medium-throughput X-ray protein–ligand structure determination. Reactions were deliberately allowed to run “out of control” in terms of selectivity; for example the ortho-arylation of 2-phenylpyridine gave five products resulting from mono- and bisarylations combined with SNAr processes. As a result, a number of crystallographic hits against NUDT7, a key peroxisomal CoA ester hydrolase, have been identified.  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