全文获取类型
收费全文 | 1740篇 |
免费 | 69篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 67篇 |
综合类 | 2篇 |
化学工业 | 409篇 |
金属工艺 | 68篇 |
机械仪表 | 53篇 |
建筑科学 | 26篇 |
能源动力 | 140篇 |
轻工业 | 56篇 |
水利工程 | 8篇 |
石油天然气 | 3篇 |
无线电 | 235篇 |
一般工业技术 | 416篇 |
冶金工业 | 123篇 |
原子能技术 | 17篇 |
自动化技术 | 196篇 |
出版年
2023年 | 26篇 |
2022年 | 60篇 |
2021年 | 74篇 |
2020年 | 64篇 |
2019年 | 51篇 |
2018年 | 73篇 |
2017年 | 56篇 |
2016年 | 61篇 |
2015年 | 42篇 |
2014年 | 67篇 |
2013年 | 115篇 |
2012年 | 84篇 |
2011年 | 90篇 |
2010年 | 77篇 |
2009年 | 74篇 |
2008年 | 78篇 |
2007年 | 70篇 |
2006年 | 59篇 |
2005年 | 43篇 |
2004年 | 31篇 |
2003年 | 32篇 |
2002年 | 32篇 |
2001年 | 23篇 |
2000年 | 17篇 |
1999年 | 27篇 |
1998年 | 53篇 |
1997年 | 32篇 |
1996年 | 29篇 |
1995年 | 29篇 |
1994年 | 12篇 |
1993年 | 25篇 |
1992年 | 11篇 |
1991年 | 19篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1973年 | 7篇 |
排序方式: 共有1819条查询结果,搜索用时 31 毫秒
81.
Gennady Verkhivker Steve Agajanian Ryan Kassab Keerthi Krishnan 《International journal of molecular sciences》2022,23(8)
In this study, we combine all-atom MD simulations and comprehensive mutational scanning of S-RBD complexes with the angiotensin-converting enzyme 2 (ACE2) host receptor in the native form as well as the S-RBD Delta and Omicron variants to (a) examine the differences in the dynamic signatures of the S-RBD complexes and (b) identify the critical binding hotspots and sensitivity of the mutational positions. We also examined the differences in allosteric interactions and communications in the S-RBD complexes for the Delta and Omicron variants. Through the perturbation-based scanning of the allosteric propensities of the SARS-CoV-2 S-RBD residues and dynamics-based network centrality and community analyses, we characterize the global mediating centers in the complexes and the nature of local stabilizing communities. We show that a constellation of mutational sites (G496S, Q498R, N501Y and Y505H) correspond to key binding energy hotspots and also contribute decisively to the key interfacial communities that mediate allosteric communications between S-RBD and ACE2. These Omicron mutations are responsible for both favorable local binding interactions and long-range allosteric interactions, providing key functional centers that mediate the high transmissibility of the virus. At the same time, our results show that other mutational sites could provide a “flexible shield” surrounding the stable community network, thereby allowing the Omicron virus to modulate immune evasion at different epitopes, while protecting the integrity of binding and allosteric interactions in the RBD–ACE2 complexes. This study suggests that the SARS-CoV-2 S protein may exploit the plasticity of the RBD to generate escape mutants, while engaging a small group of functional hotspots to mediate efficient local binding interactions and long-range allosteric communications with ACE2. 相似文献
82.
Pulipparambil Vasu Divya Divakaran Ambika Dhanya Krishnan Kalathil Sivanandan Viswanathan Kumar 《International Journal of Applied Ceramic Technology》2009,6(2):231-235
Ferroelectric glass–ceramics of composition 0.90 (Ba0.7 Sr0.3 ) TiO3 –0.10(B2 O3 :SiO2 ) (0.90 BST:0.10 BS) synthesized by sol–gel method have been used for the preparation of dielectric thick-film inks. The particle dispersion of the glass–ceramic powders in the thick-film ink formulations have been studied through rheological measurements for fabricating thick-film capacitors by screen printing technique. The thick films derived from such glass–ceramics are found to sinter at considerably lower temperatures than the pure ceramic, and exhibit good dielectric characteristics with a tunability of 32% at 1 MHz under a dc bias field of 35 kV/cm. 相似文献
83.
P.?Santhana Gopala Krishnan Rohit?H.?VoraEmail author Tai-Shung?Chung Shun-Ichiro?Uchimura Nori?Sasaki 《Journal of Polymer Research》2005,11(4):299-308
Amic acid compound namely bisphthalamic acid of 2, 2-dimethyl-4, 4-diaminobiphenyl (amic acid) and its ionic salt with 3-(dimethylamino)propyl methacrylate (amic acid salt) were synthesized and characterized by FT-IR, mass spectroscopy, NMR and DSC. Effect of temperature and water content on these compounds was studied by 1H-NMR and potentiometric titration. In the absence of added water, both amic acid and its ionic salt had undergone imidization followed by hydrolysis, which was attributed to the water formed as a result of an initial imidization reaction. Polyamic acid (PAA) was synthesized by reacting 4, 4-oxydiphthalic anhydride and 2, 2-dimethyl 4, 4-diaminobiphenyl (m-tolidine) in N-methyl-2-pyrrolidone, which was then reacted with 3-(dimethylamino)propyl methacrylate to obtain PAS. Their storage stabilities were studied by monitoring their bulk viscosities and acid numbers as a function of time and temperature. PAS was found to be less stable than PAA. Similar observations were made for amic acid compounds. PAA and PAS showed two-step thermal degradation in air and nitrogen. 相似文献
84.
J. Perez-Mariano K.H. Lau E. Alvarez R. Malhotra M. Hornbostel G. Krishnan A. Sanjurjo 《Surface & coatings technology》2008,202(12):2794-2800
Deposition of several coatings by Chemical Vapor Deposition in a Fluidized Bed was studied inside porous coupons made of 409 steel. Four different coating systems were studied: TiAlSiN/TiAl/SS409, TiAlSiN/TiAlSi/SS409, TiAlN/Nb/TiAl/SS409 and TiSiN/Nb/TiSi/SS409. Though coating thickness decreased with depth inside the porous filter, the formation of Ti-based ceramic films with thicknesses around 1 micrometer was observed 0.5 mm inside the bulk of the samples. Coated substrates were exposed to a simulated coal gas at 643 K for 300 hours, in order to study their corrosion resistance under conditions that mimic a porous metal particulate filter of a coal gasification system. Some of the coatings did not provide enough protection against corrosion at the bulk of the porous coupons, and iron sulfide crystals were formed that plugged the pores. On the other hand, the TiSiN/Nb/TiSi/SS409 system showed no sign of corrosion. 相似文献
85.
86.
87.
Thermal Shock Resistance of Ceramic Foams 总被引:2,自引:0,他引:2
Venkata R. Vedula David J. Green John R. Hellman 《Journal of the American Ceramic Society》1999,82(3):649-656
Thermal shock behavior of a variety of open-cell ceramic foams was evaluated using infrared heating and forced air cooling. The extent of damage after thermal shock was determined by a nondestructive, dynamic resonance technique. The damage in foams was found to be strongly dependent on cell size and weakly dependent on density. In zirconia-based foams, damage was found to increase with an increase in zirconia content. A thermal stress resistance parameter R 'f was derived to predict the effect of cell size and density on the damage incurred in foams. The experimental results were found to corroborate the predictions fairly well but a better approach was to compare the maximum applied thermal strains with the degree of damage. 相似文献
88.
Sundaram Vickram Karunakaran Rohini Subramanian Srinivasan David Nancy Veenakumari Kumar Archana Krishnan Anbarasu Palanivelu Jeyanthi Sundaram Thanigaivel Govindarajan Gulothungan Nanmaran Rajendiran Padmalayam Sadanandan Srikumar 《International journal of molecular sciences》2021,22(4)
Zinc (Zn), the second-most necessary trace element, is abundant in the human body. The human body lacks the capacity to store Zn; hence, the dietary intake of Zn is essential for various functions and metabolism. The uptake of Zn during its transport through the body is important for proper development of the three major accessory sex glands: the testis, epididymis, and prostate. It plays key roles in the initial stages of germ cell development and spermatogenesis, sperm cell development and maturation, ejaculation, liquefaction, the binding of spermatozoa and prostasomes, capacitation, and fertilization. The prostate releases more Zn into the seminal plasma during ejaculation, and it plays a significant role in sperm release and motility. During the maternal, labor, perinatal, and neonatal periods, the part of Zn is vital. The average dietary intake of Zn is in the range of 8–12 mg/day in developing countries during the maternal period. Globally, the dietary intake of Zn varies for pregnant and lactating mothers, but the average Zn intake is in the range of 9.6–11.2 mg/day. The absence of Zn and the consequences of this have been discussed using critical evidence. The events and functions of Zn related to successful fertilization have been summarized in detail. Briefly, our current review emphasizes the role of Zn at each stage of human reproduction, from the spermatogenesis process to childbirth. The role of Zn and its supplementation in in vitro fertilization (IVF) opens opportunities for future studies on reproductive biology. 相似文献
89.
Daniela M. Ushizima Hrishikesh A. Bale E. Wes Bethel Peter Ercius Brett A. Helms Harinarayan Krishnan Lea T. Grinberg Maciej Haranczyk Alastair A. Macdowell Katarzyna Odziomek Dilworth Y. Parkinson Talita Perciano Robert O. Ritchie Chao Yang 《JOM Journal of the Minerals, Metals and Materials Society》2016,68(11):2963-2972
90.
In this investigation, low-cement castables were prepared using 70% alumina grog aggregates obtained from crushed alumina brick waste. The aggregates were thermally treated at 1550 °C for 3 h. Four types of low-cement castables were prepared with various types of aggregates (alumina grog with or without thermal treatment) and fillers (with or without zircon addition), and they were evaluated in terms of their physical, thermal, and chemical properties. Microstructural analysis via scanning electron microscopy (SEM) was performed on the castables before and after slag attack. Compared to the other fabricated castables, the thermally treated alumina grog castables with zircon showed better physical properties, such as a higher bulk density, cold crushing strength, and modulus of rupture and a lower apparent porosity and water absorption. In addition, they had a higher positive linear thermal expansion, refractoriness under load, permanent linear change, and hot modulus of rupture. The results of the SEM with energy dispersive X-ray analysis of the prepared castables confirmed that the mullite and anorthite phases were predominant when zircon was not added and the zircon–mullite phase additionally appeared upon the incorporation of zircon. A quantitative elemental analysis via X-ray fluorescence spectroscopy was employed to determine the composition of the castables. X-ray diffraction analysis showed that the alumina grog castables had a high mullite and low anorthite content, and the thermally treated alumina grog had a high anorthite, low mullite, and high zircon content. The improvement in the mechanical and thermo-mechanical properties of the castables with thermally treated alumina grog and added zircon can be attributed to the formation of the zircon–mullite phase with a low mullite phase content. 相似文献