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761.
Belalakatte P. Nandeshwarappa Doyijode B. Aruna Kumar Halehatty S. Bhojya Naik Kittappa M. Mahadevan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):1997-2003
A convenient, efficient, and inexpensive procedure for the synthesis of 3-formyl-2-mercaptoquinolines 2a–l has been developed by a simple one-pot reaction of 3-formyl-2-chloroquinolines 1a–l with sodium sulfide and hydrochloric acid in ethanol. The structures of all the synthesized compounds were elucidated on the basis of elemental analyses and IR, 1 H NMR, and mass spectral data. 相似文献
762.
James M. Fordham Matthew N. Grayson Varinder K. Aggarwal 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(43):15412-15416
Alkenyl boronic esters are important reagents in organic synthesis. Herein, we report that these valuable products can be accessed by the homologation of boronic esters with lithiated epoxysilanes. Aliphatic and electron‐rich aromatic boronic esters provided vinylidene boronic esters in moderate to high yields, while electron‐deficient aromatic and vinyl boronic esters were found to give the corresponding vinyl silane products. Through DFT calculations, this divergence in mechanistic pathway has been rationalized by considering the stabilization of negative charge in the C?Si and C?B bond breaking transition states. This vinylidene homologation was used in a short six‐step stereoselective synthesis of the proposed structure of machillene, however, synthetic and reported data were found to be inconsistent. 相似文献
763.
Regio‐ and Stereoselective Homologation of 1,2‐Bis(Boronic Esters): Stereocontrolled Synthesis of 1,3‐Diols and Sch 725674 下载免费PDF全文
Alexander Fawcett Dr. Dominik Nitsch Prof. Dr. Muhammad Ali Joseph M. Bateman Dr. Eddie L. Myers Prof. Dr. Varinder K. Aggarwal 《Angewandte Chemie (International ed. in English)》2016,55(47):14663-14667
1,2‐Bis(boronic esters), derived from the enantioselective diboration of terminal alkenes, can be selectively homologated at the primary boronic ester by using enantioenriched primary/secondary lithiated carbamates or benzoates to give 1,3‐bis(boronic esters), which can be subsequently oxidized to the corresponding secondary‐secondary and secondary‐tertiary 1,3‐diols with full stereocontrol. The transformation was applied to a concise total synthesis of the 14‐membered macrolactone, Sch 725674. The nine‐step synthetic route also features a novel desymmetrizing enantioselective diboration of a divinyl carbinol derivative and high‐yielding late‐stage cross‐metathesis and Yamaguchi macrolactonization reactions. 相似文献
764.
Aruna K. Mora Sushant Murudkar A. Alamelu Dr. Prabhat K. Singh Dr. Subrata Chattopadhyay Dr. Sukhendu Nath 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16505-16512
Early detection of amyloid fibrils is very important for the timely diagnosis of several neurological diseases. Thioflavin‐T (ThT) is a gold standard fluorescent probe for amyloid fibrils and has been used for the last few decades. However, due to its positive charge, ThT is incapable of crossing the blood–brain barrier and cannot be used for in vivo imaging of fibrils. In the present work, we synthesized a neutral ThT derivative, 2‐[2’‐Me,4’‐(dimethylamino)phenyl]benzothiazole (2Me‐DABT), which showed a strong affinity towards the amyloid fibrils. On association with the amyloid fibrils, 2Me‐DABT not only showed a large increase in its emission intensity, but also, unlike ThT, a large blueshift in its emission spectrum was observed. Thus, unlike ThT, 2Me‐DABT is a potential candidate for the ratiometric sensor of the amyloid fibrils. Detailed photophysical properties of 2Me‐DABT in amyloid fibrils and different solvent media were studied to understand its sensory activity. Fluorescence resonance energy transfer (FRET) studies suggested that the sites of localization for ThT and 2Me‐DABT in amyloid fibrils are not same and their average distance of separation in amyloid fibrils was determined. The experimental data was nicely supported by molecular docking studies, which confirmed the binding of 2Me‐DABT in the inner core of the amyloid fibrils. 相似文献
765.
Electrodeposition of milligram amounts of uranium on electropolished stainless steel disks 总被引:1,自引:0,他引:1
S. K. Aggarwal P. M. Shah R. K. Duggal H. C. Jain 《Journal of Radioanalytical and Nuclear Chemistry》1991,154(2):103-110
Investigations have been carried out for the electrodeposition of milligram amounts of uranium on electropolished stainless steel disks with an objective of preparing good quality sources for -spectrometric studies on uranium. The parameters studied include the variation of electrodeposition yield as a function of voltage, time, distance between the cathode and anode, and the volume of 0.2M ammonium oxalate solution. The conditions selected for preparing good quality sources with nearly 100% yield were: electrodeposition voltage 25 V, time of deposition 15 min, volume of 0.2M ammonium oxalate solution in the cell 4 ml and a distance of 2 cm between the cathode and anode. The sources prepared using this method have been used successfully for the -spectrometric determination of234U/238U ratios in uranium samples. 相似文献
766.
S. K. Aggarwal P. M. Shah R. K. Duggal H. C. Jain 《Journal of Radioanalytical and Nuclear Chemistry》1991,148(2):309-317
Experimental evaluation on the use of239Pu spike in Isotope Dilution-Thermal Ionization Mass Spectrometry (ID-TIMS),238Pu spike in Isotope Dilution Alpha Spectrometry (IDAS) and233U as a Non-Isotopic Diluent in Alpha Spectrometry (N-IDAS), for determing plutonium concentration in samples with burn-up values in the range of 1,000–10,000 MWD/TU is done. Precision is determined by analyzing replicate aliquots from different samples using each of the three spikes. Accuracy is established by comparing the results with those obtained by using well recognized spike242Pu in ID-TIMS. It is shown that the use of239Pu spike with the latest generation thermal ionization mass spectrometers gives the best precision (0.2%), whereas the precision values of 0.5 and 1% can be obtained by using238Pu and233U spikes, respectively, on a routine basis. Reasons for the difference in the precision values are discussed, along with the merits and drawbacks on the use of different spike isotopes. 相似文献
767.
Suresh K. Aggarwal Michael Kinter David A. Herold 《Journal of the American Society for Mass Spectrometry》1991,2(1):85-90
The therapeutic importance of platinum (Pt) compounds, the growing accessibility of gas chromatography/mass spectrometry (GC/MS) systems in clinical laboratories, and the lack of a mass spectrometric method for the determination of Pt in biological samples motivated us to develop an isotope dilution GC/MS assay for Pt. The method is based on the use of lithium bis(trifluoroethyl) dithiocarbamate, Li(FDEDTC), as a chelating agent and enriched 192Pt for isotope dilution. Conditions were optimized for the precise and accurate determination of isotope ratios of Pt by using a 10-m DB-l fused silica capillary column and a reverse-geometry double-focusing mass spectrometer with selected ion monitoring. An overall precision of 1% was obtained by combining within-run precision and between-run precision at the 10-ng level. No appreciable memory effect was observed when samples with different isotope ratios were analyzed sequentially. The method was validated by the quantitation of Pt in National Institute of Standards and Technology freeze-dried urine sample SRM 2670. A concentration value of 125 ± 6 /Lg/L (n = 6) was obtained by using four different sets of isotope ratios in the molecular ion and supports the National Institute of Standards and Technology recommended value of 120 ± ? μg/L. Limits-of-quantitation, estimated at 3 μg/L, are made possible by the high sensitivity of the method and the low blank value for Pt. 相似文献
768.
769.