全文获取类型
收费全文 | 28699篇 |
免费 | 2156篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 187篇 |
综合类 | 10篇 |
化学工业 | 6303篇 |
金属工艺 | 475篇 |
机械仪表 | 590篇 |
建筑科学 | 886篇 |
矿业工程 | 53篇 |
能源动力 | 684篇 |
轻工业 | 5949篇 |
水利工程 | 320篇 |
石油天然气 | 133篇 |
武器工业 | 1篇 |
无线电 | 1131篇 |
一般工业技术 | 4584篇 |
冶金工业 | 5653篇 |
原子能技术 | 89篇 |
自动化技术 | 3833篇 |
出版年
2024年 | 52篇 |
2023年 | 282篇 |
2022年 | 388篇 |
2021年 | 820篇 |
2020年 | 707篇 |
2019年 | 743篇 |
2018年 | 1261篇 |
2017年 | 1233篇 |
2016年 | 1297篇 |
2015年 | 996篇 |
2014年 | 1188篇 |
2013年 | 2408篇 |
2012年 | 1877篇 |
2011年 | 1757篇 |
2010年 | 1414篇 |
2009年 | 1262篇 |
2008年 | 1273篇 |
2007年 | 1180篇 |
2006年 | 766篇 |
2005年 | 656篇 |
2004年 | 605篇 |
2003年 | 578篇 |
2002年 | 487篇 |
2001年 | 385篇 |
2000年 | 301篇 |
1999年 | 348篇 |
1998年 | 2016篇 |
1997年 | 1257篇 |
1996年 | 783篇 |
1995年 | 439篇 |
1994年 | 335篇 |
1993年 | 339篇 |
1992年 | 103篇 |
1991年 | 79篇 |
1990年 | 64篇 |
1989年 | 63篇 |
1988年 | 86篇 |
1987年 | 86篇 |
1986年 | 73篇 |
1985年 | 79篇 |
1984年 | 65篇 |
1983年 | 37篇 |
1982年 | 41篇 |
1981年 | 64篇 |
1980年 | 62篇 |
1978年 | 31篇 |
1977年 | 107篇 |
1976年 | 213篇 |
1975年 | 35篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Ana Belén Bautista-Ortín Rim Ben Abdallah Liliana del Rocío Castro-López María Dolores Jiménez-Martínez Encarna Gómez-Plaza 《International journal of molecular sciences》2016,17(1)
The transference and reactivity of proanthocyanidins is an important issue that affects the technological processing of some fruits, such as grapes and apples. These processes are affected by proanthocyanidins bound to cell wall polysaccharides, which are present in high concentrations during the processing of the fruits. Therefore, the effective extraction of proanthocyanidins from fruits to their juices or derived products will depend on the ability to manage these associations, and, in this respect, enzymes that degrade these polysaccharides could play an important role. The main objective of this work was to test the role of pure hydrolytic enzymes (polygalacturonase and cellulose) and a commercial enzyme containing these two activities on the extent of proanthocyanidin-cell wall interactions. The results showed that the modification promoted by enzymes reduced the amount of proanthocyanidins adsorbed to cell walls since they contributed to the degradation and release of the cell wall polysaccharides, which diffused into the model solution. Some of these released polysaccharides also presented some reactivity towards the proanthocyanidins present in a model solution. 相似文献
992.
Biosynthesis and purification of histidine‐tagged human soluble catechol‐O‐methyltransferase 下载免费PDF全文
993.
Ana Laura CIMADOR Emeli Luciana GALANTE Lucila Ibel MUÑOZ Patricia Silvia ROMANO Antonella Denisse LOSINNO María Cristina VANRELL 《Biocell》2019,43(1):13-20
Trypanosoma rangeli and T. cruzi are both parasitic unicellular species that infect humans. Unlike T. cruzi,
the causative agent of Chagas disease, T. rangeli is an infective and non-pathogenic parasite for humans, but pathogenic
for vectors from the Rhodnius genus. Because both species can coexist in different hosts and overlap their infective
cycles but very little is known about the infection of T. rangeli in mammalian cells, we decided to characterize both the
development of this parasite in cell culture and the effect of therapeutic agents with potential trypanocidal action on
it. We found that T. rangeli exhibits a cycle of infection in Vero cells similar to that for T. cruzi and that the repurposed
drug, 17-AAG, and the natural extract Artemisia sp. essential oil produce a toxic effect on epimastigotes showing
a trypanocidal action from the fifth day of culture. Both treatments also affected the infection of trypomastigotes
and reduced the capacity of replication of amastigotes of T. rangeli. Since T. cruzi / T. rangeli coinfection cases have
been reported, the finding of drugs with potential activity against both species could be significant in the future.
Furthermore, studies of susceptibility of both species to drugs could also help to know the different mechanisms of
pathogenicity in humans displayed by T. cruzi that are absent in T. rangeli 相似文献
994.
Igor A. Magno Fabrício A. Souza Marlo O. Costa Jacson M. Nascimento Adrina P. Silva Thiago S. Costa 《Materials Science & Technology》2019,35(7):791-806
Horizontal directional solidification and precipitation hardening experiments were performed with the Al5.5Si3Cu alloy. Solidification thermal and microstructural parameters such as growth and cooling rates (VL and TR, respectively) and the secondary dendrite arm spacing (λ2) were determined experimentally. As-solidified samples were selected and submitted to the T6-heat treatment (T6-HT). The T6-HT was carried out considering two solution times: 8 and 5?h at 490?±?2°C, followed by quenching in warm water (60?±?2°C), aging for 5?h at 155?±?2°C and air-cooling. Higher HV values were observed for the solution time of 5 h. As highlights of this work, the influence of the processing parameters (VL, TR and λ2) on the distribution, morphology and size of the eutectic Si particles has been investigated. 相似文献
995.
996.
997.
Maria Pemartín Gregorio Sánchez-Marín José Luis Munuera-Alemán 《Industry and innovation》2019,26(1):57-77
Since new product development (NPD) collaborations with external partners have become the next generation in NPD practices, relationship promoters have become especially relevant as key contributors to the success of this type of inter-organisational collaboration. To realise successful outcomes in NPD collaborations, partners face the challenge of effectively integrating the role of relationship promoter into their existing and essential relationships of trust. It is within this context that this paper examines the role of the relationship promoter, by analysing its moderating effect on the relationship between trust and the outcomes of NPD collaboration – including new product competitiveness and partner satisfaction. We test our hypotheses against survey data from 107 innovative firms involved in NPD collaboration with the help of relationship promoters. The results show that, while a non-significant influence can be reported about the presence of a relationship promoter in terms of partner satisfaction, the relationship promotor weakens the influence of trust on new product competitiveness, making trust less important when it comes to creating a competitive new product. 相似文献
998.
Sarwar Sohail Qayyum Zia Ul García-Castro Raúl Safyan Muhammad Munir Rana Faisal 《Multimedia Tools and Applications》2019,78(24):34745-34771
Multimedia Tools and Applications - Enhancing the degree of learner productivity, one of the major challenges in E-Learning systems, may be catered through effective personalization, adaptivity and... 相似文献
999.
Abstract An ion pair (RBMB) isolated from Rose Bengal and Methylene Blue has been used as the photoinitiator in formulations of photopolymers tested as holographic recording materials in the form of dry films. Under irradiation with light of wavelength 633 or 514 nm, diffraction efficiencies of 65 and 35%, and sensitivities of 30 and 100mJcm?2 have been respectively reached, with a spatial resolution of ca. 1000 lines mm?1. These holographic responses are better than those reached under comparative conditions using a 1:1 physical mixture of the individual dyes. The influence of the light intensity on the photoinitiation of the polymerization process yielding the hologram has also been studied. 相似文献
1000.
María Carolina Martín Vilma Inés Morata de Ambrosini 《International Journal of Food Science & Technology》2014,49(8):1893-1901
The effect of a new cold‐active pectinolytic system on colour of Malbec wines was studied under the following winemaking conditions: (i) fermentation at low temperature (20 °C) and (ii) prefermentative cold maceration (PCM) (5 °C–7 days) followed by traditional fermentation (28 °C). The pectinolytic system was mainly composed of polymethylgalacturonase and pectin lyase activities, detected under similar conditions to those in winemaking (pH 3.6–20 °C). The results show that the enzyme system significantly accelerated colour extraction by reducing the maceration time necessary for vinification at low temperature and shortening the PCM stage. Enzyme‐treated wines exhibited better chromatic parameters than their controls at devatting and after 6 months of storage. The cold‐active enzyme compensated the decrease in colour extraction due to the low maceration temperature, achieving high‐quality wines with chromatic characteristics similar to those of traditional wines. 相似文献