全文获取类型
收费全文 | 48150篇 |
免费 | 2756篇 |
国内免费 | 152篇 |
专业分类
电工技术 | 701篇 |
综合类 | 63篇 |
化学工业 | 9578篇 |
金属工艺 | 2133篇 |
机械仪表 | 3236篇 |
建筑科学 | 1095篇 |
矿业工程 | 24篇 |
能源动力 | 2102篇 |
轻工业 | 3865篇 |
水利工程 | 269篇 |
石油天然气 | 86篇 |
武器工业 | 2篇 |
无线电 | 7791篇 |
一般工业技术 | 10577篇 |
冶金工业 | 3878篇 |
原子能技术 | 658篇 |
自动化技术 | 5000篇 |
出版年
2023年 | 537篇 |
2022年 | 327篇 |
2021年 | 1345篇 |
2020年 | 1069篇 |
2019年 | 1175篇 |
2018年 | 1429篇 |
2017年 | 1411篇 |
2016年 | 1750篇 |
2015年 | 1293篇 |
2014年 | 2088篇 |
2013年 | 3006篇 |
2012年 | 3265篇 |
2011年 | 3889篇 |
2010年 | 2814篇 |
2009年 | 2921篇 |
2008年 | 2811篇 |
2007年 | 2185篇 |
2006年 | 2031篇 |
2005年 | 1723篇 |
2004年 | 1571篇 |
2003年 | 1505篇 |
2002年 | 1302篇 |
2001年 | 1079篇 |
2000年 | 901篇 |
1999年 | 839篇 |
1998年 | 1489篇 |
1997年 | 936篇 |
1996年 | 751篇 |
1995年 | 555篇 |
1994年 | 459篇 |
1993年 | 405篇 |
1992年 | 282篇 |
1991年 | 271篇 |
1990年 | 257篇 |
1989年 | 241篇 |
1988年 | 203篇 |
1987年 | 167篇 |
1986年 | 119篇 |
1985年 | 115篇 |
1984年 | 91篇 |
1983年 | 61篇 |
1982年 | 38篇 |
1981年 | 39篇 |
1980年 | 30篇 |
1979年 | 30篇 |
1978年 | 30篇 |
1977年 | 38篇 |
1976年 | 61篇 |
1975年 | 19篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 91 毫秒
31.
Yoon Hyuk Kim Batbayar Khuyagbaatar Kyungsoo Kim 《Journal of Mechanical Science and Technology》2018,32(1):1-10
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
32.
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
33.
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
34.
Manjunatha S. Muttigi Byoung Ju Kim Bogyu Choi Inbo Han Hansoo Park Soo-Hong Lee 《International journal of molecular sciences》2020,21(23)
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
35.
Park Sangwon Nam Hyunbin Na Youngsang Kim Hyoungseop Moon Younghoon Kang Namhyun 《Metals and Materials International》2020,26(5):641-649
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
36.
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
37.
38.
Kim Ho Jin Lee Mi Jin Park Hye Jin Kim Hye Jin Cho Soon Kil Jeong Min Hee 《Food science and biotechnology》2018,27(3):877-882
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
39.
AbstractBuilding thermal inertia and operation control strategies have impacted on the thermal performance of a radiant floor heating system. This study conducts a two-dimensional numerical analysis of an intermittently operated radiant floor heating system using the Re-Normalization Group model with Discrete Ordinates Radiation model. A detailed numerical simulation setups and various analyses are provided, including grid independency analysis, initial condition, time step sizes and external boundary conditions. Three different weekend day intermittent operation strategies are investigated. The results showed that Case 3 designed with pre-heating of 20?h has better performance compared to Case 1 designed with pre-heating of 8?h and Case 2 designed with pre-heating of 14?h. The average indoor air temperature differences of approximate 2.1, 1.6 and 1.2 K are observed for Case 1, Case 2 and Case 3, respectively, when comparing two-time slot at 8:00am on Friday morning and Monday morning. This significantly highlights the effect of thermal inertia and the potential of energy saving due to the utilization of intermittent operation. Therefore, the current study presents numerical simulation potential in evaluating the radiant floor heating effects on indoor thermal environment, taking into account building thermal inertia and transient external climatic conditions. 相似文献
40.
Jihoon Kim Lauren F. Sestito Sooseok Im Won Jong Kim Susan N. Thomas 《Advanced functional materials》2020,30(16)
Despite the approval of oncolytic virus (OV) therapy for advanced melanoma, its intrinsic limitations that include the risk of persistent viral infection and cost‐intensive manufacturing motivate the development of analogous approaches that are free from the disadvantages of virus‐based therapies. Herein, reported is a nanoassembly comprised of multivalent host–guest interactions between polymerized paclitaxel (pPTX) and nitric oxide‐incorporated polymerized β‐cyclodextrin (pCD‐pSNO) that through its bioactive components and when used locoregionally recapitulates the therapeutic effects of OV. The resultant pPTX/pCD‐pSNO exhibits significantly enhanced cytotoxicity, immunogenic cell death, dendritic cell (DC) activation, and T cell expansion in vitro compared to free agents alone or in combination. In vivo, intratumoral administration of pPTX/pCD‐pSNO results in activation and expansion of DCs systemically, but with a corresponding expansion of myeloid‐derived suppressor cells and suppression of CD8+ T cell expansion. When combined with antibody targeting cytotoxic T lymphocyte antigen‐4 that blunts this molecule's signaling effects on T cells, intratumoral pPTX/pCD‐pSNO treatment elicits potent anticancer effects that significantly prolong animal survival. This formulation thus leverages the chemo‐ and immunotherapeutic synergies of PTX and nitric oxide and suggests the potential for virus‐free nanoformulations to mimic the therapeutic action and benefits of OVs. 相似文献