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991.
Isomerization of Secondary Phosphirane into Terminal Phosphinidene Complexes: An Analogy between Monovalent Phosphorus and Transition Metals 下载免费PDF全文
Jonathan Wong Yongxin Li Yanwei Hao Rongqiang Tian François Mathey 《Angewandte Chemie (International ed. in English)》2015,54(44):12891-12893
Secondary phosphirane complexes isomerize above 100 °C to give the corresponding terminal phosphinidene complexes, which can be trapped by alkenes and alkynes. This reaction is a rare instance of the isomerization of a PIII derivative into a PI derivative. It appears to mimic the reductive elimination of alkanes from transition‐alkylmetal hydrides. 相似文献
992.
Wrinkled Graphene Monoliths as Superabsorbing Building Blocks for Superhydrophobic and Superhydrophilic Surfaces 下载免费PDF全文
Li‐Bing Lv Tian‐Lu Cui Bing Zhang Hong‐Hui Wang Prof. Xin‐Hao Li Prof. Jie‐Sheng Chen 《Angewandte Chemie (International ed. in English)》2015,54(50):15165-15169
Superhydrophobic and superhydrophilic surfaces are of great interest because of a large range of applications, for example, as antifogging and self‐cleaning coatings, as antibiofouling paints for boats, in metal refining, and for water–oil separation. An aqueous ink based on three‐dimensional graphene monoliths (Gr) can be used for constructing both superhydrophobic and superhydrophilic surfaces on arbitrary substrates with different surficial structures from the meso‐ to the macroscale. The surface wettability of a Gr‐coated surface mainly depends on which additional layers (air for a superhydrophobic surface and water for a superhydrophilic surface) are adsorbed on the surface of the graphene sheets. Switching a Gr‐coated surface between being superhydrophobic and superhydrophilic can thus be easily achieved by drying and prewetting with ethanol. The Gr‐based superhydrophobic membranes or films should have great potential as efficient separators for fast and gravity‐driven oil–water separation. 相似文献
993.
Surface Trapping and STM Observation of Conformational Isomers of a Bis(Terpyridine) Ligand from Metallosupramolecular Grids 下载免费PDF全文
Sujoy Karan Dr. Christian Hamann Dr. Hao Tang Dr. Artur R. Stefankiewicz Prof. Jean‐Marie Lehn Prof. Richard Berndt 《Chemphyschem》2015,16(7):1370-1373
Tetranuclear Co‐grid complexes incorporating bis‐tridentate ligands, namely 4,6‐bis(2,2′‐bipyrid‐6‐yl)‐2‐phenylpyrimidine, were electrosprayed onto a Au(111) substrate under an ultrahigh vacuum. Fragmentation occurs leaving the ligands in four different conformations. Most ligands are found to form H‐bonded dimers. The most abundant conformer of the ligand on the Au surface is an asymmetric form, which has not been observed before. The present results indicate that the fragmentation of coordination compounds during the deposition process, in principle, allows for surface trapping, identification, and investigation of high energy, out‐of‐equilibrium conformations of the ligand molecules at low temperatures, which otherwise would not be observable. 相似文献
994.
Fabrication and performance of microencapsulated phase change materials with hybrid shell by in situ polymerization in Pickering emulsion 下载免费PDF全文
Microencapsulated phase change materials (MePCMs) using melamine–formaldehyde resin/SiO2 as shell were investigated in this paper. Organically modified SiO2 particles were employed to stabilize Pickering emulsion, and in situ polymerization of melamine and formaldehyde was carried out to form hybrid shell. The performances of resultant MePCMs with hybrid shell were investigated comparatively with the MePCMs with polymer shell. SiO2 particles raise the microencapsulation efficiency by improving the stability of emulsion and providing a precipitation site for melamine–formaldehyde resin. Also, the mechanical strength, thermal reliability, and anti‐osmosis performance of MePCMs were improved significantly by SiO2 particles in the shell. Our study shows that Pickering emulsion is a simple and robust template for MePCMs with polymer‐inorganic hybrid shell. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
995.
Structure and further fragmentation of significant [a3 + Na − H]+ ions from sodium‐cationized peptides 下载免费PDF全文
Huixin Wang Bing Wang Zhonglin Wei Hao Zhang Xinhua Guo 《Journal of mass spectrometry : JMS》2015,50(1):212-219
A good understanding of gas‐phase fragmentation chemistry of peptides is important for accurate protein identification. Additional product ions obtained by sodiated peptides can provide useful sequence information supplementary to protonated peptides and improve protein identification. In this work, we first demonstrate that the sodiated a3 ions are abundant in the tandem mass spectra of sodium‐cationized peptides although observations of a3 ions have rarely been reported in protonated peptides. Quantum chemical calculations combined with tandem mass spectrometry are used to investigate this phenomenon by using a model tetrapeptide GGAG. Our results reveal that the most stable [a3 + Na ? H]+ ion is present as a bidentate linear structure in which the sodium cation coordinates to the two backbone carbonyl oxygen atoms. Due to structural inflexibility, further fragmentation of the [a3 + Na ? H]+ ion needs to overcome several relatively high energetic barriers to form [b2 + Na ? H]+ ion with a diketopiperazine structure. As a result, low abundance of [b2 + Na ? H]+ ion is detected at relatively high collision energy. In addition, our computational data also indicate that the common oxazolone pathway to generate [b2 + Na ? H]+ from the [a3 + Na ? H]+ ion is unlikely. The present work provides a mechanistic insight into how a sodium ion affects the fragmentation behaviors of peptides. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
996.
Dr. Guang‐Ping Hao Giovanni Mondin Dr. Zhikun Zheng Tim Biemelt Stefan Klosz René Schubel Prof. Alexander Eychmüller Prof. Stefan Kaskel 《Angewandte Chemie (International ed. in English)》2015,54(6):1941-1945
There is significant interest in high‐performance materials that can directly and efficiently capture water vapor, particularly from air. Herein, we report a class of novel porous carbon cuboids with unusual ultra‐hydrophilic properties, over which the synergistic effects between surface heterogeneity and micropore architecture is maximized, leading to the best atmospheric water‐capture performance among porous carbons to date, with a water capacity of up to 9.82 mmol g?1 at P/P0=0.2 and 25 °C (20 % relative humidity or 6000 ppm). Benefiting from properties, such as defined morphology, narrow pore size distribution, and high heterogeneity, this series of functional carbons may serve as model materials for fundamental research on carbon chemistry and the advance of new types of materials for water‐vapor capture as well as other applications requiring combined highly hydrophilic surface chemistry, developed hierarchical porosity, and excellent stability. 相似文献
997.
Catalytic Asymmetric Intramolecular Homologation of Ketones with α‐Diazoesters: Synthesis of Cyclic α‐Aryl/Alkyl β‐Ketoesters 下载免费PDF全文
Dr. Wei Li Fei Tan Xiaoyu Hao Gang Wang Yu Tang Prof. Dr. Xiaohua Liu Dr. Lili Lin Prof. Dr. Xiaoming Feng 《Angewandte Chemie (International ed. in English)》2015,54(5):1608-1611
A catalytic asymmetric intramolecular homologation of simple ketones with α‐diazoesters was firstly accomplished with a chiral N,N′‐dioxide–Sc(OTf)3 complex. This method provides an efficient access to chiral cyclic α‐aryl/alkyl β‐ketoesters containing an all‐carbon quaternary stereocenter. Under mild conditions, a variety of aryl‐ and alkyl‐substituted ketone groups reacted with α‐diazoester groups smoothly through an intramolecular addition/rearrangement process, producing the β‐ketoesters in high yield and enantiomeric excess. 相似文献
998.
Formation of DNA:RNA Hybrid G‐Quadruplex in Bacterial Cells and Its Dominance over the Intramolecular DNA G‐Quadruplex in Mediating Transcription Termination 下载免费PDF全文
999.
Inside Back Cover: Surface Trapping and STM Observation of Conformational Isomers of a Bis(Terpyridine) Ligand from Metallosupramolecular Grids (ChemPhysChem 7/2015) 下载免费PDF全文
1000.
Tracing novel hemostatic compounds from heating products of total flavonoids in Flos Sophorae by spectrum–effect relationships and column chromatography 下载免费PDF全文
Hao Wu Yaozong Pan Kuilong Wang Liping Liu Yangping Jin Chenchao Zhang 《Journal of separation science》2015,38(10):1691-1699
Flos Sophorae and its processed product have been clinically used to treat hemorrhage. In this study, the total ion chromatographic fingerprints of the heating products of total flavonoids in Flos Sophorae were established by high‐performance liquid chromatography with tandem mass spectrometry and the hemostatic activities were studied by hemostatic screening tests in vivo. The spectrum–effect relationships between fingerprints and hemostatic activities were investigated using canonical correlation analysis to trace the peaks responsible for the hemostatic effects. The predicted active peaks in fingerprints were isolated by column chromatography and their structures were identified by NMR spectroscopy and mass spectrometry. The hemostatic activities of them were verified by platelet aggregation and procoagulation assays in vitro. Canonical correlation analysis results showed that peak 8 and peak 11 were correlated most closely, thus probably being the main hemostatic compounds. Through column chromatography separation, peak 8 (compound I) and peak 11 (compound II) were obtained with purities of 95.61 and 93.38%, respectively, and were discovered new hemostatic compounds named as huaicarbon A (I) and huaicarbon B (II), respectively. This study provides a universal model to trace the active compounds of other herbs which have bioactivity enhancement after processing by spectrum–effect relationships and column chromatography. 相似文献