全文获取类型
收费全文 | 498873篇 |
免费 | 8644篇 |
国内免费 | 2039篇 |
专业分类
电工技术 | 9462篇 |
综合类 | 508篇 |
化学工业 | 76411篇 |
金属工艺 | 20470篇 |
机械仪表 | 15994篇 |
建筑科学 | 12537篇 |
矿业工程 | 1358篇 |
能源动力 | 14304篇 |
轻工业 | 44623篇 |
水利工程 | 3833篇 |
石油天然气 | 4599篇 |
武器工业 | 19篇 |
无线电 | 66509篇 |
一般工业技术 | 95398篇 |
冶金工业 | 92482篇 |
原子能技术 | 8601篇 |
自动化技术 | 42448篇 |
出版年
2022年 | 2980篇 |
2021年 | 4837篇 |
2020年 | 3456篇 |
2019年 | 4130篇 |
2018年 | 6521篇 |
2017年 | 6471篇 |
2016年 | 7044篇 |
2015年 | 5113篇 |
2014年 | 8489篇 |
2013年 | 23885篇 |
2012年 | 13624篇 |
2011年 | 18543篇 |
2010年 | 14740篇 |
2009年 | 16420篇 |
2008年 | 17061篇 |
2007年 | 16431篇 |
2006年 | 14803篇 |
2005年 | 13379篇 |
2004年 | 12755篇 |
2003年 | 12883篇 |
2002年 | 12432篇 |
2001年 | 12446篇 |
2000年 | 11461篇 |
1999年 | 12337篇 |
1998年 | 30444篇 |
1997年 | 21292篇 |
1996年 | 16660篇 |
1995年 | 12608篇 |
1994年 | 11098篇 |
1993年 | 10809篇 |
1992年 | 7813篇 |
1991年 | 7655篇 |
1990年 | 7062篇 |
1989年 | 6850篇 |
1988年 | 6653篇 |
1987年 | 5643篇 |
1986年 | 5577篇 |
1985年 | 6281篇 |
1984年 | 5656篇 |
1983年 | 5276篇 |
1982年 | 4922篇 |
1981年 | 4825篇 |
1980年 | 4633篇 |
1979年 | 4355篇 |
1978年 | 4126篇 |
1977年 | 5130篇 |
1976年 | 7291篇 |
1975年 | 3500篇 |
1974年 | 3367篇 |
1973年 | 3296篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
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
172.
Microalgae can efficiently fix carbon dioxide through their phototropic metabolism, and have been recognized as a promising bioresource for animal feed, health food, fuel, cosmetic, and pharmaceutical products. However, since microalgae in cultivated medium have a low biomass concentration (0.1–1% w/w), both harvesting and concentration of microalgal biomass are often required prior to the production of commercial products. Efficient and cost-effective dewatering and drying methods for microalgae heavily affect the overall energy consumption and production cost of microalgal products. This review describes the characteristics of commonly used dewatering and drying technologies, and critically evaluates the feasibility for their use to treat microalgal biomass. No single dewatering or drying method can satisfactorily handle all types of microalgae. The suitability of each method depends on the properties of the microalgae suspension, the required process design, the quality of the end product, and the related capital and production costs. 相似文献
173.
174.
175.
Lecture capture with real‐time rearrangement of visual elements: impact on student performance 下载免费PDF全文
The primary goal of this study is to create and test a lecture‐capture system that can rearrange visual elements while recording is still taking place, in such a way that student performance can be positively influenced. The system we have devised is capable of integrating and rearranging multimedia sources, including learning content, the instructor and students' images, into lecture videos that are embedded in a website for students to review after school. The present study employed a two‐group experimental design, with 153 participants (145 females and 8 males) making up an experimental group in which lecture courses were recorded using the new lecture‐capture system, and 149 participants (140 females and 9 males) forming a control group whose lectures were recorded by traditional means. All participants were in the freshman college and studying Introduction to Computer and Information Science in one of six classes, and were randomly assigned to one of the two groups. The participants' midterm examination and final examination scores were collected as indicators of their academic performance, with their mathematics entrance scores used as a pre‐test. The findings obtained from analysis of covariance (ANCOVA) suggest that appropriate rearrangement of visual elements in lecture videos can significantly impact students' learning performance. 相似文献
176.
177.
178.
Vashchenko S.V. Khudyakov A.Yu. Baiul K.V. Semenov Yu.S. 《Powder Metallurgy and Metal Ceramics》2021,60(3-4):247-256
Powder Metallurgy and Metal Ceramics - The mechanisms of phase interactions in granular media were studied to elaborate the results obtained previously at the Nekrasov Iron and Steel Institute of... 相似文献
179.
Choi HyungSeok Kim ChanHyung Choi Hyuk Lee JaeHwan 《Food science and biotechnology》2021,30(11):1435-1443
Food Science and Biotechnology - Buah merah oil and red palm oil are red colored and unrefined edible oils. Because of this color characteristic, measuring acid value by titration method can be... 相似文献
180.
Chandel Narendra Singh Chakraborty Subir Kumar Rajwade Yogesh Anand Dubey Kumkum Tiwari Mukesh K. Jat Dilip 《Neural computing & applications》2021,33(10):5353-5367
Neural Computing and Applications - The identification of water stress is a major challenge for timely and effective irrigation to ensure global food security and sustainable agriculture. Several... 相似文献