全文获取类型
收费全文 | 27030篇 |
免费 | 1299篇 |
国内免费 | 329篇 |
专业分类
电工技术 | 524篇 |
综合类 | 554篇 |
化学工业 | 6448篇 |
金属工艺 | 593篇 |
机械仪表 | 816篇 |
建筑科学 | 1105篇 |
矿业工程 | 215篇 |
能源动力 | 717篇 |
轻工业 | 3187篇 |
水利工程 | 284篇 |
石油天然气 | 212篇 |
武器工业 | 27篇 |
无线电 | 2633篇 |
一般工业技术 | 3711篇 |
冶金工业 | 4016篇 |
原子能技术 | 183篇 |
自动化技术 | 3433篇 |
出版年
2023年 | 218篇 |
2022年 | 978篇 |
2021年 | 1205篇 |
2020年 | 492篇 |
2019年 | 540篇 |
2018年 | 630篇 |
2017年 | 569篇 |
2016年 | 660篇 |
2015年 | 564篇 |
2014年 | 791篇 |
2013年 | 1450篇 |
2012年 | 1157篇 |
2011年 | 1370篇 |
2010年 | 1019篇 |
2009年 | 1079篇 |
2008年 | 1066篇 |
2007年 | 1058篇 |
2006年 | 912篇 |
2005年 | 756篇 |
2004年 | 818篇 |
2003年 | 1010篇 |
2002年 | 1282篇 |
2001年 | 1069篇 |
2000年 | 635篇 |
1999年 | 588篇 |
1998年 | 1368篇 |
1997年 | 901篇 |
1996年 | 679篇 |
1995年 | 462篇 |
1994年 | 352篇 |
1993年 | 381篇 |
1992年 | 220篇 |
1991年 | 169篇 |
1990年 | 170篇 |
1989年 | 144篇 |
1988年 | 150篇 |
1987年 | 126篇 |
1986年 | 121篇 |
1985年 | 166篇 |
1984年 | 102篇 |
1983年 | 106篇 |
1982年 | 88篇 |
1981年 | 113篇 |
1980年 | 107篇 |
1979年 | 70篇 |
1978年 | 52篇 |
1977年 | 107篇 |
1976年 | 198篇 |
1975年 | 54篇 |
1973年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We present results on the Forcespinning® (FS) of Polyacrylonitrile (PAN) for mass production of polymer nanofiber membranes as separators for Lithium‐ion batteries (LIBs). Our results presented here show that uniform, highly fibrous mats from PAN produced using Forcespinning®, exhibit improved electrochemical properties such as electrolyte uptake, low interfacial resistance, high oxidation limit, high ionic conductivity, and good cycling performance when used in lithium ion batteries compared to commercial PP separator materials. This article introduces ForceSpinning®, a cost effective technique capable of mass producing high quality fibrous mats, which is completely different technology than the commonly used in‐house centrifugal method. This Forcespinning® technology is thus the beginning of the nano/micro fiber revolution in large scale production for battery separator application. This is the first time to report results on the cycle performance of LIB‐based polymer nanofiber separators made by Forcespinning® technology. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42847. 相似文献
992.
993.
Initial Molecular Recognition Steps of McjA Precursor during Microcin J25 Lasso Peptide Maturation 下载免费PDF全文
Dr. Nadine Assrir Dr. Anna Pavelkova Régine Dazzoni Dr. Rémi Ducasse Dr. Nelly Morellet Dr. Eric Guittet Prof. Sylvie Rebuffat Dr. Séverine Zirah Dr. Yanyan Li Dr. Ewen Lescop 《Chembiochem : a European journal of chemical biology》2016,17(19):1851-1858
Microcin J25 (MccJ25) has emerged as an excellent model to understand the maturation of ribosomal precursor peptides into the entangled lasso fold. MccJ25 biosynthesis relies on the post‐translational modification of the precursor McjA by the ATP‐dependent protease McjB and the lactam synthetase McjC. Here, using NMR spectroscopy, we showed that McjA is an intrinsically disordered protein without detectable conformational preference, which emphasizes the active role of the maturation machinery on the three‐dimensional folding of MccJ25. We further showed that the N‐terminal region of the leader peptide is involved in interaction with both maturation enzymes and identified a predominant interaction of V43–S55 in the core McjA sequence with McjC. Moreover, we demonstrated that residues K23–Q34 in the N‐terminal McjA leader peptide tend to adopt a helical conformation in the presence of membrane mimics, implying a role in directing McjA to the membrane in the vicinity of the lasso synthetase/export machinery. These data provide valuable insights into the initial molecular recognition steps in the MccJ25 maturation process. 相似文献
994.
Benigna Szeptycka Anna Gajewska-Midzialek Tomasz Babul 《Journal of Materials Engineering and Performance》2016,25(8):3134-3138
The research on the graphene application for the electrodeposition of nickel composite coatings was conducted. The study assessed an important role of graphene in an increased corrosion resistance of these coatings. Watts-type nickel plating bath with low concentration of nickel ions, organic addition agents, and graphene as dispersed particles were used for deposition of the composite coatings nickel-graphene. The results of investigations of composite coatings nickel-graphene deposited from the bath containing 0.33, 0.5, and 1 g/dm3 graphene and one surface-active substance were shown. The contents of particles in coatings, the surface morphology, the cross-sectional structures of the coated samples, and their thickness and the internal stresses were studied. Voltammetric method was used for examination of the corrosion resistance of samples of composite coatings in 0.5 M NaCl. The obtained results suggest that the content of incorporated graphene particles increases with an increasing amount of graphene in plating bath. The application of organic compounds was advantageous because it caused compressive stresses in the deposited coatings. All of the nickel-graphene composite layers had better corrosion resistance than the nickel coating. 相似文献
995.
Wei Guo De Wang Yuan Fu Li Zhang Qudong Wang 《Journal of Materials Engineering and Performance》2016,25(10):4109-4114
AZ31-Mg2Si in situ composites were prepared from AZ31 Mg alloy and Si particles by a gravity casting method. Several parameters, such as Si content, normal load, and environmental temperature, were varied in order to study their effects on the composite dry sliding wear properties. Tensile properties and hardness of the composites were also investigated. The obtained results showed that the wear resistance, yield strength, and hardness of the AZ31-Mg2Si composites increased with size and quantity of the Mg2Si phase. However, when the environmental temperature increased from 25 to 190 °C, the composite wear resistance and ultimate tensile strength gradually decreased due to softening of the AZ31 matrix. 相似文献
996.
997.
998.
Marta Anna Szychlinska Francesca Maria Trovato Michelino Di Rosa Lucia Malaguarnera Lidia Puzzo Rosy Leonardi Paola Castrogiovanni Giuseppe Musumeci 《International journal of molecular sciences》2016,17(3)
Osteoarthritis is the most common human arthritis characterized by degeneration of articular cartilage. Several studies reported that levels of human cartilage glycoprotein chitinase 3-like-1 (CHI3L1) are known as a potential marker for the activation of chondrocytes and the progression of Osteoarthritis (OA), whereas lubricin appears to be chondroprotective. The aim of this study was to investigate the co-expression and co-localization of CHI3L1 and lubricin in normal and osteoarthritic rat articular cartilage to correlate their modified expression to a specific grade of OA. Samples of normal and osteoarthritic rat articular cartilage were analyzed by the Kellgren–Lawrence OA severity scores, the Kraus’ modified Mankin score and the Histopathology Osteoarthritis Research Society International (OARSI) system for histomorphometric evaluations, and through CHI3L1 and lubricin gene expression, immunohistochemistry and double immuno-staining analysis. The immunoexpression and the mRNA levels of lubricin increased in normal cartilage and decreased in OA cartilage (normal vs. OA, p < 0.01). By contrast, the immunoexpression and the mRNA levels of CHI3L1 increased in OA cartilage and decreased in normal cartilage (normal vs. OA, p < 0.01). Our findings are consistent with reports suggesting that these two glycoproteins are functionally associated with the development of OA and in particular with grade 2/3 of OA, suggesting that in the future they could be helpful to stage the severity and progression of the disease. 相似文献
999.
The development of poly(vinyl chloride) extrusions for a 14,000‐ton self‐supporting structure for the detection of neutrinos 下载免费PDF全文
James J. Grudzinski Richard L. Talaga Anna Pla‐Dalmau James E. Fagan Charles Grozis Karen Kephart Richard Fischer 《乙烯基与添加剂工艺杂志》2016,22(3):368-376
The NOvA Neutrino Experiment has built a one‐of‐a‐kind self‐supporting plastic structure, potentially the largest ever built. The poly(vinyl chloride) (PVC) structure serves as a neutrino detector and is composed of 28 individual blocks that measure 15.5 m (51 feet) high by 15.5 m (51 feet) wide by 2.1 m (7 feet) deep. The primary parts in the detector construction are 15.5‐m (51‐foot), 16‐cell PVC extrusions. These extrusions form the basis of the detector modules, which are laminated together in a crossed pattern to form the individual blocks and then filled with (mineral oil)–based liquid scintillator. The self‐supporting nature of the detector places important structural requirements on both the PVC formulation and the extrusions. Block assembly requirements impose narrow geometric tolerances. Because of the method of detecting neutrinos, the extrusions must possess exceptionally high reflectivity over a particular wavelength range. This requirement places additional restrictions on the components of the PVC formulation. Altogether, the PVC extrusions have to maintain important reflectivity characteristics, provide structural support to the detector, and meet relatively tight geometric requirements for assembly. In order to meet these constraints, a custom PVC formulation had to be created and extruded. We describe the purpose and requirements of the NOvA detector leading to the production of our unique PVC extrusion, summarize the research and development process, and discuss the lessons learned. J. VINYL ADDIT. TECHNOL., 22:368–376, 2016. © 2014 Society of Plastics Engineers 相似文献
1000.