全文获取类型
收费全文 | 553288篇 |
免费 | 7035篇 |
国内免费 | 1769篇 |
专业分类
电工技术 | 10130篇 |
综合类 | 440篇 |
化学工业 | 81606篇 |
金属工艺 | 22060篇 |
机械仪表 | 17757篇 |
建筑科学 | 12242篇 |
矿业工程 | 3178篇 |
能源动力 | 15295篇 |
轻工业 | 41655篇 |
水利工程 | 5966篇 |
石油天然气 | 10691篇 |
武器工业 | 23篇 |
无线电 | 65881篇 |
一般工业技术 | 111624篇 |
冶金工业 | 105143篇 |
原子能技术 | 12471篇 |
自动化技术 | 45930篇 |
出版年
2021年 | 5026篇 |
2020年 | 3781篇 |
2019年 | 4881篇 |
2018年 | 8244篇 |
2017年 | 8272篇 |
2016年 | 8774篇 |
2015年 | 5628篇 |
2014年 | 9294篇 |
2013年 | 26547篇 |
2012年 | 14934篇 |
2011年 | 20227篇 |
2010年 | 16127篇 |
2009年 | 18258篇 |
2008年 | 18679篇 |
2007年 | 18470篇 |
2006年 | 16402篇 |
2005年 | 14826篇 |
2004年 | 14094篇 |
2003年 | 14022篇 |
2002年 | 13113篇 |
2001年 | 13115篇 |
2000年 | 12477篇 |
1999年 | 13017篇 |
1998年 | 33253篇 |
1997年 | 23060篇 |
1996年 | 17790篇 |
1995年 | 13163篇 |
1994年 | 11729篇 |
1993年 | 11572篇 |
1992年 | 8506篇 |
1991年 | 8020篇 |
1990年 | 7841篇 |
1989年 | 7578篇 |
1988年 | 7224篇 |
1987年 | 6355篇 |
1986年 | 6136篇 |
1985年 | 6975篇 |
1984年 | 6379篇 |
1983年 | 5851篇 |
1982年 | 5303篇 |
1981年 | 5519篇 |
1980年 | 5030篇 |
1979年 | 5026篇 |
1978年 | 5011篇 |
1977年 | 5675篇 |
1976年 | 7529篇 |
1975年 | 4314篇 |
1974年 | 4074篇 |
1973年 | 4144篇 |
1972年 | 3435篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
93.
A. A. Babenko V. I. Zhuchkov L. A. Smirnov A. V. Sychev A. A. Akberdin A. S. Kim M. F. Vitushchenko A. A. Dobromilov 《Steel in Translation》2015,45(11):883-886
A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite. 相似文献
94.
95.
Dr. Blijke S. Kroezen Gabriele Conti Benedetta Girardi Dr. Jonathan Cramer Dr. Xiaohua Jiang Dr. Said Rabbani Jennifer Müller Maja Kokot Enrico Luisoni Prof. Daniel Ricklin Dr. Oliver Schwardt Prof. Beat Ernst 《ChemMedChem》2020,15(18):1706-1719
Siglecs are members of the immunoglobulin gene family containing sialic acid binding N-terminal domains. Among them, Siglec-8 is expressed on various cell types of the immune system such as eosinophils, mast cells and weakly on basophils. Cross-linking of Siglec-8 with monoclonal antibodies triggers apoptosis in eosinophils and inhibits degranulation of mast cells, making Siglec-8 a promising target for the treatment of eosinophil- and mast cell-associated diseases such as asthma. The tetrasaccharide 6’-sulfo-sialyl Lewisx has been identified as a specific Siglec-8 ligand in glycan array screening. Here, we describe an extended study enlightening the pharmacophores of 6’-sulfo-sialyl Lewisx and the successful development of a high-affinity mimetic. Retaining the neuraminic acid core, the introduction of a carbocyclic mimetic of the Gal moiety and a sulfonamide substituent in the 9-position gave a 20-fold improved binding affinity. Finally, the residence time, which usually is the Achilles tendon of carbohydrate/lectin interactions, could be improved. 相似文献
96.
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
97.
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
98.
Abiodun B. Ogbesejana Zhong Ningning Oluwadayo O. Sonibare 《Petroleum Science and Technology》2019,37(18):1969-1977
The occurrence and distributions of dibenzofurans (DBFs) and benzo[b]naphthofurans were investigated in crude oils from Niger Delta, Nigeria, by gas chromatography-mass spectrometry-mass spectrometry. The distribution of DBFs was characterized by the predominance of C2-dibenzofurans. 4-Methyldibenzofuran was the most abundant among the methyldibenzofurans isomers while dimethyldibenzofuran-2 (DMDBF-2), ethyldibenzofuran-1, DMDBF-3, and DMDBF-6 occurred in higher amounts when compared with other DMDBFs. Among the benzonaphthofurans, the abundance of benzo[b]naphtho[2,1-d]furan was higher than other isomers. The DBFs distributions in the oils were not affected by source facies and depositional environments. However, the DBFs concentrations increased with increasing maturity in oils from ADL and MJO oilfields. 相似文献
99.
Chitosan microspheres containing bromocresol green, cresol red, and phenolphthalein for corrosion detection, through pH change, are synthesized in order to be used in protective coatings for aluminium alloys. Microspheres containing corrosion detection species are characterized morphologically (SEM) and physico‐chemically (FTIR, TGA). Release studies (UV–vis) are performed in corrosion‐promoting conditions (pH, NaCl), and detection studies by immersion in media associated with corrosion activity while microspheres' sensing activity is evaluated visually. Electrochemical characterization of AA2024 substrates in the presence of chitosan spheres is performed to understand material performance, and a color change is observed as a result of local pH increase in cathodic areas when corrosion takes place. These findings can be correlated with the results from release studies and seem a promising approach for corrosion sensing purposes, not only because pH increase is possible to detect due to corrosion, but also because chitosan is considered an environmentally friendly material. 相似文献
100.
C. G. Prosgolitis S. G. Lambrakos A. D. Zervaki 《Journal of Materials Engineering and Performance》2018,27(10):5102-5113
This work presents simulation of microstructure evolution in the nugget zone (NZ) of a AZ31-Mg-alloy friction stir weld. The process parameters (tool geometrical characteristics, rotational speed, travel speed, applied load) have been correlated with the resulting microstructural features in the NZ of the weld (grain size and population) with the aid of the MICRESS software, which provides the ability to simulate both nucleation and grain growth during dynamic recrystallization phenomena evolving in the NZ during the weld thermal cycle. The input parameters of the developed model include the tool geometry, the welding conditions as well as the recrystallization energy, the grain boundary mobility and specific material properties. NZ microstructure obtained by simulation shows good agreement with experimental measurements for both grain population and size. 相似文献