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   3214篇
  免费   136篇
  国内免费   12篇
电工技术   28篇
综合类   2篇
化学工业   663篇
金属工艺   72篇
机械仪表   86篇
建筑科学   144篇
矿业工程   12篇
能源动力   127篇
轻工业   277篇
水利工程   32篇
石油天然气   6篇
无线电   208篇
一般工业技术   655篇
冶金工业   630篇
原子能技术   25篇
自动化技术   395篇
  2023年   52篇
  2022年   82篇
  2021年   104篇
  2020年   107篇
  2019年   103篇
  2018年   101篇
  2017年   92篇
  2016年   92篇
  2015年   69篇
  2014年   100篇
  2013年   181篇
  2012年   145篇
  2011年   208篇
  2010年   143篇
  2009年   143篇
  2008年   185篇
  2007年   150篇
  2006年   107篇
  2005年   101篇
  2004年   75篇
  2003年   70篇
  2002年   44篇
  2001年   48篇
  2000年   47篇
  1999年   54篇
  1998年   52篇
  1997年   43篇
  1996年   51篇
  1995年   43篇
  1994年   28篇
  1993年   19篇
  1992年   26篇
  1991年   15篇
  1990年   26篇
  1989年   25篇
  1988年   17篇
  1987年   21篇
  1986年   23篇
  1985年   27篇
  1984年   15篇
  1983年   18篇
  1982年   21篇
  1981年   23篇
  1980年   28篇
  1979年   18篇
  1978年   24篇
  1977年   19篇
  1976年   20篇
  1975年   16篇
  1973年   18篇
排序方式: 共有3362条查询结果,搜索用时 15 毫秒
61.
The authors investigated the direct and interactive effects of the job demand– control–support (JDC-S) model’s components on subsequent changes in high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides (TRI) separately for male and female employees. In contrast to all 14 past studies on these relationships, the authors used a longitudinal design. Study participants (N = 1,137, 66% men) were all apparently healthy employees who underwent a routine health check at 2 points in time (Time 1 and Time 2) about 22 months apart. In these analyses, the authors controlled for the Time 1 level of each criterion and for other confounders. Most of the direct and moderating effects found did not support the predictions of the JDC-S model; this finding is in agreement with the majority of past cross-sectional studies. The authors did not find any evidence supporting the existence of a reverse causation for either of the components of the JDC-S model. The authors suggest that serum lipids may not be a physiological mechanism mediating the effects of the JDC-S model on atherosclerotic diseases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
62.
Exponential increases in multiracial identities, expected over the next century, create a conundrum for perceivers accustomed to classifying people as their own- or other-race. The current research examines how perceivers resolve this dilemma with regard to the own-race bias. The authors hypothesized that perceivers are not motivated to include ambiguous-race individuals in the in-group and therefore have some difficulty remembering these individuals. Both racially ambiguous and other-race faces were misremembered more often than own-race faces (Study 1), though memory for ambiguous faces was improved among perceivers motivated to include biracial individuals in the in-group (Study 2). Racial labels assigned to racially ambiguous faces determined memory for these faces, suggesting that uncertainty provides the motivational context for discounting ambiguous faces in memory (Study 3). Finally, an inclusion motivation fostered cognitive associations between racially ambiguous faces and the in-group. Moreover, the extent to which perceivers associated racially ambiguous faces with the in-group predicted memory for ambiguous faces and accounted for the impact of motivation on memory (Study 4). Thus, memory for biracial individuals seems to involve a flexible person construal process shaped by motivational factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
63.
64.
There is an urgent need to better understand the mechanisms involved in scar formation in the brain. It is well known that astrocytes are critically engaged in this process. Here, we analyze incipient scar formation one week after a discrete ischemic insult to the cerebral cortex. We show that the infarct border zone is characterized by pronounced changes in the organization and subcellular localization of the major astrocytic protein AQP4. Specifically, there is a loss of AQP4 from astrocytic endfoot membranes that anchor astrocytes to pericapillary basal laminae and a disassembly of the supramolecular AQP4 complexes that normally abound in these membranes. This disassembly may be mechanistically coupled to a downregulation of the newly discovered AQP4 isoform AQP4ex. AQP4 has adhesive properties and is assumed to facilitate astrocyte mobility by permitting rapid volume changes at the leading edges of migrating astrocytes. Thus, the present findings provide new insight in the molecular basis of incipient scar formation.  相似文献   
65.
66.
Darwin  S.  Arun Samuel  T. S. 《SILICON》2020,12(2):393-403
Silicon - The 2D analytical models for electrostatic potential, threshold voltage, subthreshold swing, Drain Induced Barrier Lowering (DIBL) and drain current of the Dual Material Double Gate...  相似文献   
67.
The nasal epithelium is a key portal for infection by respiratory viruses such as SARS-CoV-2 and represents an important target for prophylactic and therapeutic interventions. In the present study, we test the safety and efficacy of a newly developed nasal spray (AM-301, marketed as Bentrio) against infection by SARS-CoV-2 and its Delta variant on an in vitro 3D-model of the primary human nasal airway epithelium. Safety was assessed in assays for tight junction integrity, cytotoxicity and cilia beating frequency. Efficacy against SARS-CoV-2 infection was evaluated in pre-viral load and post-viral load application on airway epithelium. No toxic effects of AM-301 on the nasal epithelium were found. Prophylactic treatment with AM-301 significantly reduced viral titer vs. controls over 4 days, reaching a maximum reduction of 99% in case of infection from the wild-type SARS-CoV-2 variant and more than 83% in case of the Delta variant. When AM-301 administration was started 24 h after infection, viral titer was reduced by about 12-folds and 3-folds on Day 4. The results suggest that AM-301 is safe and significantly decelerates SARS-CoV-2 replication in cell culture inhibition assays of prophylaxis (pre-viral load application) and mitigation (post-viral load application). Its physical (non-pharmaceutical) mechanism of action, safety and efficacy warrant additional investigations both in vitro and in vivo for safety and efficacy against a broad spectrum of airborne viruses and allergens.  相似文献   
68.
The present studies were conducted to evaluate key serum proteins and other components that mediate anchorage-independent growth (3-D growth) of LNCaP prostate cancer cells as spheroids. The cells were cultured on ultra-low attachment plates in the absence and presence of fetuin-A and with or without extracellular vesicles. The data show that fetuin-A (alpha 2HS glycoprotein) is the serum protein that mediates 3-D growth in these cells. It does so by sequestering extracellular vesicles of various sizes on the surfaces of rounded cells that grow as spheroids. These vesicles in turn transmit growth signals such as the activation of AKT and MAP kinases in a pattern that differs from the activation of these key growth signaling pathways in adherent and spread cells growing in 2-D. In the process of orchestrating the movement and disposition of extracellular vesicles on these cells, fetuin-A is readily internalized in adhered and spread cells but remains on the surfaces of non-adherent cells. Taken together, our studies suggest the presence of distinct signaling domains or scaffolding platforms on the surfaces of prostate tumor cells growing in 3-D compared to 2-D.  相似文献   
69.
Multiple myeloma is a hematologic malignancy of plasma cells that causes bone-destructive lesions and associated skeletal-related events (SREs). The pathogenesis of myeloma-related bone disease (MBD) is the imbalance of the bone-remodeling process, which results from osteoclast activation, osteoblast suppression, and the immunosuppressed bone marrow microenvironment. Many important signaling cascades, including the RANKL/RANK/OPG axis, Notch signaling, the Wnt/β-Catenin signaling pathways, and signaling molecules, such as DKK-1, sclerostin, osteopontin, activin A, chemokines, and interleukins are involved and play critical roles in MBD. Currently, bisphosphonate and denosumab are the gold standard for MBD prevention and treatment. As the molecular mechanisms of MBD become increasingly well understood, novel agents are being thoroughly explored in both preclinical and clinical settings. Herein, we will provide an updated overview of the pathogenesis of MBD, summarize the clinical management and guidelines, and discuss novel bone-modifying therapies for further management of MBD.  相似文献   
70.
Annals of Telecommunications - This paper presents a new consensus algorithm, Proof of Usage (PoU), for the blockchain technology. This consensus is introduced for permissioned (or private)...  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