全文获取类型
收费全文 | 3457篇 |
免费 | 156篇 |
国内免费 | 27篇 |
专业分类
化学 | 2198篇 |
晶体学 | 44篇 |
力学 | 92篇 |
综合类 | 3篇 |
数学 | 205篇 |
物理学 | 618篇 |
无线电 | 480篇 |
出版年
2024年 | 26篇 |
2023年 | 41篇 |
2022年 | 162篇 |
2021年 | 170篇 |
2020年 | 111篇 |
2019年 | 129篇 |
2018年 | 139篇 |
2017年 | 105篇 |
2016年 | 165篇 |
2015年 | 120篇 |
2014年 | 127篇 |
2013年 | 273篇 |
2012年 | 252篇 |
2011年 | 246篇 |
2010年 | 141篇 |
2009年 | 141篇 |
2008年 | 151篇 |
2007年 | 132篇 |
2006年 | 106篇 |
2005年 | 93篇 |
2004年 | 79篇 |
2003年 | 74篇 |
2002年 | 90篇 |
2001年 | 59篇 |
2000年 | 65篇 |
1999年 | 28篇 |
1998年 | 31篇 |
1997年 | 34篇 |
1996年 | 18篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 21篇 |
1992年 | 19篇 |
1991年 | 15篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 21篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1975年 | 5篇 |
排序方式: 共有3640条查询结果,搜索用时 15 毫秒
171.
172.
Farhan M. Khan Muhammad A. Abbasi Aziz-ur-Rehman Sabahat Z. Siddiqui Abdul R. Sadiq Butt Hussain Raza Ayesha Zafar Syed A. Ali Shah Muhammad Shahid Sung-Yum Seo 《Journal of heterocyclic chemistry》2021,58(5):1089-1103
By using a convergent methodology, a novel series of N-arylated 4-yl-benzamides containing a bi-heterocyclic thiazole–triazole core was synthesized, and the structures of these hybrid molecules, 9a–k , were corroborated through spectral analyses. The in vitro studies of these multifunctional molecules demonstrated their potent carbonic anhydrase inhibition relative to the standard used. The kinetics mechanism was exposed by Lineweaver–Burk plots, which revealed that 9j inhibited carbonic anhydrase non-competitively by forming an enzyme-inhibitor complex. The inhibition constants Ki calculated from Dixon plots for this compound was 1.2 μM. The computational study was also persuasive with the experimental results, and these molecules disclosed good results of all scoring functions and interactions, which suggested a good binding to carbonic anhydrase. So, it was predicted from the inferred results that these molecules might be considered as promising medicinal scaffolds for various diseases related to the uncontrolled production of this enzyme. 相似文献
173.
Nanotextured multicrystalline Al‐BSF solar cells reaching 18% conversion efficiency using industrially viable solar cell processes 下载免费PDF全文
Bishal Kafle Abdul Mannan Timo Freund Laurent Clochard Edward Duffy Marc Hofmann Jochen Rentsch Ralf Preu 《固体物理学:研究快报》2015,9(8):448-452
We report recent achievements in adapting industrially used solar cell processes on nanotextured surfaces. Nanostructures were etched into c‐Si surfaces by dry exothermic plasma‐less reaction of F species with Si in atmospheric pressure conditions and then modified using a short post‐etching process. Nanotextured multicrystalline wafers are used to prepare Al‐BSF solar cells using industrially feasible solar cell proc‐ essing steps. In comparison to the reference acidic textured solar cells, the nanostructured cells showed gain in short circuit current (Jsc) of up to 0.8 mA/cm2 and absolute gain in conversion efficiency of up to 0.3%. The best nanotextured solar cell was independently certified to reach the conversion efficiency of 18.0%. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
174.
Naved Azum Malik Abdul Rub Abdullah M. Asiri Mohd. Akram 《Russian Journal of Physical Chemistry B, Focus on Physics》2015,9(6):940-945
Aggregation behavior of cationic gemini (hexanediyl-1,5-bis(dimethylcettylammonium bromide) (16-5-16)) surfactant with conventional single chain surfactants cetyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB) were studied with the help of fluorescence measurements. Fluorescence probe is a proficient technique for examining the surfactant-surfactant interaction and aggregation. The micelle aggregation number (N agg) was measured using steady-state fluorescence quenching method. The micelle aggregation numbers of binary combinations fall between those of constituent surfactants. The micropolarity (I 1/I 3), binding constant (K sv) and dielectric constant (D exp) of mixed systems were determined from the ratio of peaks intensity in the pyrene fluorescence spectrum. The I 1/I 3 values were found to be more than >1, showing more polar environment around pyrene in the mixed micelle as compared to the pure micelles. 相似文献
175.
176.
M. Jawaid Othman Y. Alothman M. T. Paridah H. P. S Abdul Khalil 《International Journal of Polymer Analysis and Characterization》2014,19(1):62-69
In this work, oil palm empty fruit bunch (EFB) and jute fibers were treated with 2-hydroxy ethyl acrylate (2-HEA) to improve interfacial bonding of oil palm EFB and jute fibers with epoxy matrix. Hybrid composites were fabricated by incorporation of modified oil palm EFB and jute fibers into an epoxy matrix by the hand lay-up technique. Mechanical (flexural and impact) and morphological properties of modified hybrid composites were measured. Results indicated that flexural and impact properties of modified fiber–reinforced hybrid composites improved as compared to untreated hybrid composites due to better fiber/matrix interfacial bonding, which was confirmed by scanning electron microscopy. We confirmed that treated oil palm/jute hybrid composite may be fabricated by advanced techniques such as resin transfer molding, extrusion, and injection molding for industrial applications in the automotive sector. 相似文献
177.
M. Y. A. Rahman A. A. Umar L. Roza M. M. Salleh 《Russian Journal of Electrochemistry》2014,50(11):1072-1076
This work is concerned with the growth of TiO2 nanostructures as photovoltaic materials of dyesensitized solar cell (DSSC) via phase liquid deposition technique treated with CTAB surfactant. This work investigates the influence of organic dyes, N719, N3 and Z907 as photosensitizer on the photovoltaic parameters of TiO2 nanostructures dye-sensitized solar cells (DSSCs). It also highlights the effect of the concentration of the best dye, N719 on the performance of the cell. The platinum films as counter electrode of the DSSC were prepared by sputtering platinum pellet on ITO substrate. The redox couple of the electrolyte utilized in the DSSC was iodide/triiodide. The cell sensitized with N719 dye demonstrated the best performance compared with the cell sensitized with another two dyes, N3 and Z907. This is due to N719 dye possess the highest optical absorption in visible region. The cell sensitized with 0.8 mM N719 dye performs the highest short-circuit current density, J sc and power conversion efficiency, η since it posses the highest absorption in visible region. The DSSC utilizing 0.8 mM N719 dye demonstrated the highest J sc and η of 6.48 mA cm?2 and 1.69%, respectively. 相似文献
178.
A deep-cavity ‘mixed’ octahomotetraoxacalix[2]naphthalene[2]pyridine macrocycle has been synthesised and its single-crystal X-ray structure has been determined. Molecular modeling studies suggested that this macrocycle could be an effective host for guest aromatic diol(s) similar to Wang's methylazacalixpyridines. Binding constants were determined using 1H NMR chemical shifts changes and comparisons were made between the diols which were tested. 相似文献
179.
Lee Chuin Chen Md. Matiur Rahman Kenzo Hiraoka 《Journal of the American Society for Mass Spectrometry》2014,25(11):1862-1869
The heating of electrospray ion source under atmospheric pressure is limited to the normal boiling point of the solution. The boiling takes place when the vapor pressure of the liquid at a given temperature equals the ambient pressure. By using a high pressure ESI source, which has been developed previously in our laboratory, a stable electrospray ionization of super-heated aqueous solution is performed up to a solution temperature of 180°C. The ion source is pressurized with pure nitrogen to a maximum pressure of 11 atm, and it is coupled to a commercial mass spectrometer via a custom-made ion transport capillary. A booster pump with variable pumping speed is added to the pumping system to regulate the pressure in the first pumping stage at 1?~?1.3 Torr. High pressure mass spectrometry is performed on several peptides and proteins to demonstrate its application in the temperature-controlled thermally induced denaturation and dissociation. Graphical Abstract
? 相似文献
180.
A 1H NMR spectroscopic study of tetra-n-butylammonium halides (TBAX: X = Cl? , Br? or I? ) in CDCl3 solutions was conducted. Complexation studies of TBAX salts with different host molecules using 1H NMR in CDCl3 have previously revealed that the reference residual CHCl3 proton signal had been shifted downfield. The aim of the study was to quantify the extent of these chemical shift changes with TBAX salts. Linear concentration–chemical shift relationships in each case were obtained from the resulting titration plots obtained from the addition of the TBAX salts alone to CDCl3. Interactions in the solid state as determined by X-ray crystallography support the solution-state investigations indicating halide ion–chloroform proton interactions. 相似文献