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   102843篇
  免费   1754篇
  国内免费   452篇
电工技术   1006篇
综合类   2343篇
化学工业   15234篇
金属工艺   5194篇
机械仪表   3416篇
建筑科学   3138篇
矿业工程   666篇
能源动力   1715篇
轻工业   5308篇
水利工程   1428篇
石油天然气   408篇
无线电   10714篇
一般工业技术   19687篇
冶金工业   6327篇
原子能技术   401篇
自动化技术   28064篇
  2023年   133篇
  2022年   150篇
  2021年   347篇
  2020年   249篇
  2019年   288篇
  2018年   14726篇
  2017年   13645篇
  2016年   10331篇
  2015年   958篇
  2014年   748篇
  2013年   1427篇
  2012年   3947篇
  2011年   10529篇
  2010年   9039篇
  2009年   6346篇
  2008年   7678篇
  2007年   8591篇
  2006年   900篇
  2005年   1954篇
  2004年   1732篇
  2003年   1720篇
  2002年   1075篇
  2001年   443篇
  2000年   491篇
  1999年   401篇
  1998年   517篇
  1997年   386篇
  1996年   405篇
  1995年   345篇
  1994年   327篇
  1993年   303篇
  1992年   284篇
  1991年   211篇
  1990年   254篇
  1989年   219篇
  1988年   193篇
  1987年   181篇
  1986年   176篇
  1985年   203篇
  1984年   226篇
  1983年   182篇
  1982年   186篇
  1981年   174篇
  1980年   162篇
  1979年   175篇
  1978年   127篇
  1977年   131篇
  1976年   190篇
  1975年   143篇
  1974年   118篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
2.
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   
3.
With the emergence of distributed ledger technology (DLT), numerous practitioners and researchers have proclaimed its beneficial impact on supply chain transactions in the future. However, the vast majority of DLT initiatives are discontinued after a short period. With the full potential of DLT laying far down the road, especially managers in supply chain management (SCM) seek for short-term cost-saving effects of DLT in order to achieve long-term benefits of DLT in the future. However, the extant research has bypassed grounding long-term as well as short-term effects of DLT on supply chain transaction with empirical data. We address this shortcoming, following an abductive research approach and combining empirical data from a multiple case study design with the corresponding literature. Our study reveals that the effects of DLT on supply chain transactions are two-sided. We found six effects of DLT solutions that have a cost-reducing or cost avoidance impact on supply chain transactions. In addition, we found two effects that change the power distribution between buyers and suppliers in transactions and a single effect that reduces the dependency of supply chain transactions on third parties. While cost-reducing and avoidance as well as dependency-reducing effects are positive effects, the change in power distribution might come with disadvantages. With these findings, the paper provides the first empirical evidence of the impact of DLT on supply chain transactions, which will enable managers to improve their assessment of DLT usage in supply chains.  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.
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   
8.
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   
9.
To quantify the evacuation process, evacuation practitioners use engineering egress data describing the occupant movement characteristics. These data are typically based to young and fit populations. However, the movement abilities of occupants who might be involved in evacuations are becoming more variable—with the building populations of today typically including increasing numbers of individuals: with impairments or who are otherwise elderly or generally less mobile. Thus, there will be an increasing proportion of building occupants with reduced ability to egress. For safe evacuation, there is therefore a need to provide valid engineering egress data considering pedestrians with disabilities. Gwynne and Boyce recently compiled a series of data sets related to the evacuation process to support practitioner activities in the chapter Engineering Data in the SFPE Handbook of Fire Protection Engineering. This paper supplements these data sets by providing information on and presenting data obtained from additional research related to the premovement and horizontal movement of participants with physical‐, cognitive‐, or age‐related disabilities. The aim is to provide an overview of currently available data sets related to, and key factors affecting the egress performance of, mixed ability populations which could be used to guide fire safety engineering decisions in the context of building design.  相似文献   
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