全文获取类型
收费全文 | 2052篇 |
免费 | 40篇 |
国内免费 | 7篇 |
专业分类
化学 | 1158篇 |
晶体学 | 33篇 |
力学 | 53篇 |
数学 | 241篇 |
物理学 | 614篇 |
出版年
2022年 | 29篇 |
2020年 | 33篇 |
2019年 | 39篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 54篇 |
2015年 | 33篇 |
2014年 | 37篇 |
2013年 | 135篇 |
2012年 | 88篇 |
2011年 | 113篇 |
2010年 | 64篇 |
2009年 | 55篇 |
2008年 | 65篇 |
2007年 | 77篇 |
2006年 | 69篇 |
2005年 | 51篇 |
2004年 | 54篇 |
2003年 | 45篇 |
2002年 | 39篇 |
2001年 | 45篇 |
2000年 | 39篇 |
1999年 | 23篇 |
1998年 | 23篇 |
1997年 | 18篇 |
1996年 | 24篇 |
1995年 | 19篇 |
1994年 | 44篇 |
1993年 | 30篇 |
1992年 | 46篇 |
1991年 | 28篇 |
1990年 | 39篇 |
1989年 | 28篇 |
1988年 | 26篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 26篇 |
1984年 | 35篇 |
1983年 | 27篇 |
1982年 | 30篇 |
1981年 | 25篇 |
1980年 | 20篇 |
1979年 | 36篇 |
1978年 | 36篇 |
1977年 | 27篇 |
1976年 | 19篇 |
1975年 | 21篇 |
1974年 | 19篇 |
1973年 | 23篇 |
1970年 | 14篇 |
排序方式: 共有2099条查询结果,搜索用时 15 毫秒
121.
Wei Qin Rishabh Jain Francisco C. Robles Hernández Prof. Dr. Jeffrey D. Rimer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(23):5893-5898
Zeolite crystals can be used as seeds or aluminosilicate sources in syntheses to control polymorphs and/or reduce the quantity of organics used as structure-directing agents. A frequently invoked hypothesis for interzeolite transformations is that zeolites share some underlying similarity in structure, most notably in cases pertaining to organic-free syntheses. Herein, we show for the first time that ZSM-5 (MFI) can be directly obtained from USY (FAU) through an interzeolite transformation between parent–daughter structures lacking common building units in the absence of a structure-directing agent and seeds. We show that interzeolite transformation leads to a crystalline product with fewer defects. Our findings also reveal that ZSM-5 is a metastable intermediate that undergoes further transformation to mordenite (MOR) and quartz. The MFI-to-MOR transition is counter to reported trends for which transformations lead to structures with reduced molar volume. Herein, we propose mechanistic arguments that suggest the driving force for interzeolite transformation is more complex than guidelines posited in the literature. 相似文献
122.
The conventional condensation and refluxing process was employed to synthesize Ni(II) and Cu(II) complexes of Methylcarbamatethiosemicarbazone ligand. Reactions were carried out at the pH of 7. The molar ratio of the ligand and metal salt was 2:1. The structures of the synthesized metal complexes were suggested by different analytical techniques such as magnetic susceptibility, molar conductance, IR, EPR and UV spectroscopy. Experimental studies confirmed the octahedral geometry for all the complexes. The geometry of the ligand and complexes were also confirmed by theoretical studies. The complexes were investigated for biological action against pathogenic fungi (C. krusei, C. albican) and bacteria (S. aureus, E. coli). The antimicrobial results confirmed superior inhibition potential of the metal complexes as compared with the parent ligand. The enhanced antimicrobial activities might be due to the chelation. Molecular-docking assays confirmed the strong interaction of ligand with target antimicrobial protein DNA gyrase-B. 相似文献
123.
124.
Amitabh Jain 《辐射效应与固体损伤》2013,168(1-4):39-46
The potential advantages of ion implantation have been exploited in virtually every kind of semiconductor device. Several commercially important devices owe their existence to this technique. Ion implantation provides precise control over the amount of dopant, concentration profile and lateral dimensions in device fabrication. The high degree of uniformity and reproducibility have made it possible to produce sophisticated devices and integrated circuits with high yield and tight tolerances. This is a truly planar process. It is possible to achieve high doping concentrations with relatively lower processing temperatures thereby avoiding lifetime degradation. The process is carried out in an inherently clean environment. A wide range of dopants is available and one is not limited by the particular properties of the substrate. There is great flexibility in choice of masking materials and self-alignment of doped regions in MOS devices is facilitated. The increasing impact of ion implantation on device technology is discussed with reference to some recent developments. Specific commercially manufactured devices are mentioned. Ion implantation machines continue to undergo development aimed at higher throughputs and cleaner vacuum. There is the need for greater reliability of machines. Effort is also directed at the development of low cost machines for dedicated applications. Design of implanted devices continues to be an empirical process in some respects. The ability to accurately predict profile shapes in samples implanted (perhaps through a screen oxide) and subject to complicated post-implantation process steps, would cut down development time and costs. 相似文献
125.
126.
127.
Subhash C. Jain Pankaj Khanna Sunita Bhagat Manish Jain Rajeev Sakhuja 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1829-1839
The reaction of indol-2,3-diones ( 1a–i ) with 5-aminoindazole ( 2 ) has resulted in the formation of hitherto unknown 3-(indazol-5-yl)iminoindol-2-ones ( 3a–i ) in quantitative yields which, on 1,3-dipolar cyclocondensation with mercaptoacetic acid ( 4 ), has afforded a series of new spiro heterocycles, 3′-(indazol-5-yl) spiro[3H, indol-3, 2′ -thiazolidine]-2,4′-diones* ( 5a–i ). 相似文献
128.
Suizhou Yang Ke Yang Aloke Jain Ramaswamy Nagarajan Jayant Kumar 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):938-941
A novel method for maskless micro-patterning of polymeric substrates is presented. First, an azobenzene functionalized polymer film is spin-coated on a Poly (ethylene terephthalate) (PET) sheet. Then surface relief structures are optically inscribed on the polymer film by interference of laser beams. The patterned azobenzene functionalized film is then etched in the plasma chamber such that the gratings are transferred to the PET substrate. Finally, any remaining azobenzene functionalized polymer is dissolved away using an appropriate solvent. This method of patterning can be broadly applied to a variety of flexible/polymeric substrates and the resolution is not limited by the substrate thermo-mechanical properties. 相似文献
129.
R. Pankajavalli Ashish Jain Akanksha Sharma S. Anthonysamy V. Ganesan 《Journal of Thermal Analysis and Calorimetry》2013,112(1):83-93
The standard Gibbs energy of formation of M2TeO6 and M6TeO12 (where M = Sc, Y), was determined from its vapor pressure measurements by employing thermogravimetry-based transpiration technique. This technique was validated by measuring the vapor pressure of well-studied substances such as TeO2(s) and CdCl2(s). The temperature dependence of the vapor pressure of TeO2(g) over the mixtures M6TeO12 + M2O3 (where M = Sc, Y), generated by the incongruent vaporization reaction, M6TeO12(s) → 3M2O3(s) + TeO2(g) + ½O2(g) were measured in the temperature range 1,413–1,473 K and 1,623–1,743 K for Sc6TeO12(s) and Y6TeO12(s), respectively. Similarly, the vapor pressure of TeO2(g) over the mixtures M2TeO6(s) + M6TeO12(s) generated by the vaporization reaction, 3M2TeO6(s) → M6TeO12(s) + 2TeO2(g) + O2(g) was measured in the temperature range (1,223–1,293 K) and (1,333–1,423 K) for Sc2TeO6(s) and Y2TeO6(s), respectively. From the vapor pressure measurements, the standard Gibbs energy of formation of M6TeO12 and M2TeO6 were derived. 相似文献
130.
Jitender Gaur Shilpa Jain Rohit Bhatia Arun Lal Narender Kumar Kaushik 《Journal of Thermal Analysis and Calorimetry》2013,112(2):1137-1143
We demonstrate synthesis of water insoluble, novel copolymer PA1 from condensation of glyoxal dihydrazone and glyoxal dihydrazone bis(dithiocarbamate) monomers having high capacity to remove metal ions from aqueous solution. The presence of a high atomic percentage of nitrogen and sulfur atoms in PA1 leads to strong ligating ability with metal ions. The monomers and the polymer have been characterized by FTIR, UV–Visible spectroscopy, CHNS elemental analysis, NMR, MALDI-MS, and TG/DTA. As a proof of concept, the PA1 is tested for its ability to remove heavy metal ions Cu2+, Co2+, Fe2+, Ni2+, Mn2+, and CrO 7 2? from aqueous solutions. PA1 efficiently removed metals ions from the metal solutions. The highest absorption ability has been observed toward the iron salts where 0.969 g metal salt is absorbed by 1 g polymer. This study has implication for inexpensive and efficient polymer for purification of water. 相似文献