首页 | 官方网站   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   61593篇
  免费   3507篇
  国内免费   191篇
工业技术   65291篇
  2023年   612篇
  2022年   391篇
  2021年   1601篇
  2020年   1269篇
  2019年   1389篇
  2018年   1733篇
  2017年   1699篇
  2016年   2103篇
  2015年   1599篇
  2014年   2550篇
  2013年   3895篇
  2012年   3893篇
  2011年   4738篇
  2010年   3457篇
  2009年   3592篇
  2008年   3487篇
  2007年   2757篇
  2006年   2514篇
  2005年   2155篇
  2004年   1991篇
  2003年   1884篇
  2002年   1631篇
  2001年   1363篇
  2000年   1142篇
  1999年   1108篇
  1998年   2177篇
  1997年   1425篇
  1996年   1078篇
  1995年   808篇
  1994年   712篇
  1993年   626篇
  1992年   432篇
  1991年   406篇
  1990年   393篇
  1989年   372篇
  1988年   291篇
  1987年   255篇
  1986年   214篇
  1985年   210篇
  1984年   174篇
  1983年   130篇
  1982年   88篇
  1981年   100篇
  1980年   90篇
  1979年   79篇
  1978年   73篇
  1977年   105篇
  1976年   160篇
  1975年   67篇
  1973年   54篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Lee  Yang Sun  Kim  Se-Hoon 《Multimedia Tools and Applications》2020,79(23-24):16035-16049
Multimedia Tools and Applications - This paper proposed an MAC (Media Access Control) operation method based on the CCH (Control Channel) and SCH (Service Channel) control mode of the WAVE...  相似文献   
32.
33.
The human cervical spine is a complex structure that is the most frequently injured site among all spinal injuries. Therefore, understanding of the cervical spine injury and dysfunction, and also biomechanical response to external stimuli is important. Finite element (FE) modeling can help researchers to access the internal stresses and strains in the bones, ligaments and soft tissues more realistically, and it has been widely adopted for spine biomechanics research. Although in recent years numerous techniques have been developed, there are no recent literature reviews on FE models of the cervical spine. Our objective was to present recent advances in FE modeling of the human cervical spine in terms of component modeling, material properties, and validation procedures. Model applications and further development are also discussed. The integration of new technologies will allow us to generate more accurate and comprehensive model of the cervical spine, which can increase efficiency and model applicability. Finally, the FE modeling can help to facilitate diagnosis, treatment, and prevention technologies for cervical spine injuries.  相似文献   
34.
Wireless Networks - Vehicular communication is one of the critical technologies in intelligent transportation system to provide connectivity between vehicles, road side units, and pedestrians....  相似文献   
35.
In this paper, we present a performance analysis of large-scale multi-input multi-output (MIMO) systems for wireless backhaul networks. We focus on fully connected N nodes in a wireless meshed and multi-hop network topology. We also consider a large number of antennas at both the receiver and transmitter. We investigate the transmission schemes to support fully connected N nodes for half-duplex and full-duplex transmission, analyze the achievable ergodic sum rate among N nodes, and propose a closed-form expression of the achievable ergodic sum rate for each scheme. Furthermore, we present numerical evaluation results and compare the resuts with closed-form expressions.  相似文献   
36.
Adipose-derived mesenchymal stromal cells (Ad-MSCs) are a promising tool for articular cartilage repair and regeneration. However, the terminal hypertrophic differentiation of Ad-MSC-derived cartilage is a critical barrier during hyaline cartilage regeneration. In this study, we investigated the role of matrilin-3 in preventing Ad-MSC-derived chondrocyte hypertrophy in vitro and in an osteoarthritis (OA) destabilization of the medial meniscus (DMM) model. Methacrylated hyaluron (MAHA) (1%) was used to encapsulate and make scaffolds containing Ad-MSCs and matrilin-3. Subsequently, the encapsulated cells in the scaffolds were differentiated in chondrogenic medium (TGF-β, 1–14 days) and thyroid hormone hypertrophic medium (T3, 15–28 days). The presence of matrilin-3 with Ad-MSCs in the MAHA scaffold significantly increased the chondrogenic marker and decreased the hypertrophy marker mRNA and protein expression. Furthermore, matrilin-3 significantly modified the expression of TGF-β2, BMP-2, and BMP-4. Next, we prepared the OA model and transplanted Ad-MSCs primed with matrilin-3, either as a single-cell suspension or in spheroid form. Safranin-O staining and the OA score suggested that the regenerated cartilage morphology in the matrilin-3-primed Ad-MSC spheroids was similar to the positive control. Furthermore, matrilin-3-primed Ad-MSC spheroids prevented subchondral bone sclerosis in the mouse model. Here, we show that matrilin-3 plays a major role in modulating Ad-MSCs’ therapeutic effect on cartilage regeneration and hypertrophy suppression.  相似文献   
37.
Metals and Materials International - This study investigated the influence of the initial grain size on the plastic deformation and tunnel defects that occurred from friction stir welding of...  相似文献   
38.
Food Science and Biotechnology - Fish meat hydrolysates (FMHs) were produced from nine fishes at a high pressure of 300 MPa using Flavourzyme 500MG and a protease mixture including...  相似文献   
39.
40.
Food Science and Biotechnology - A new analytical method was developed for the simultaneous determination of seven food additives (Ponceau 4R, Allura Red AC, Amaranth, 4-hydroxymethyl benzoic acid,...  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-23

京公网安备 11010802026262号