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991.
992.
Turbulence,vortex and external explosion induced by venting 总被引:2,自引:0,他引:2
The process of explosion venting to air in a cylindrical vent vessel connected to a duct, filling with a stoichiometric methane-oxygen gas mixture, was simulated numerically by using a colocated grid SIMPLE scheme based on k-epsilon turbulent model and Eddydissipation combustion model. The characteristics of the combustible cloud, flame and pressure distribution in the external flow field during venting were analyzed in terms of the predicted results. The results show that the external explosion is generated due to violent turbulent combustion in the high pressure region within the external combustible cloud ignited by a jet flame. And the turbulence and vortex in the external flow field were also discussed in detail. After the jet flame penetrating into the external combustible cloud, the turbulent intensity is greater in the regions with greater average kinetic energy gradient, rather than in the flame front ; and the vortex in the external flow field is generated primarily due to the baroclinic effect, which is greater in the regions where the pressure and density gradients are nearly perpendicular. 相似文献
993.
994.
对12年前经离子注入处理后的GCr15轴承钢表面耐磨性能的时间效应进行了探讨。发现离子注入材料的改性效果存在时间效应性。利用AES和X射线衍射分析发现,掺杂原子及材料表面吸附的氧原子的多元迁移和硬质相的生成是造成离子注入材料改性时效的原因。 相似文献
995.
Diaminodiacid Bridges to Improve Folding and Tune the Bioactivity of Disulfide‐Rich Peptides 下载免费PDF全文
Ye Guo De‐Meng Sun Feng‐Liang Wang Yao He Prof. Lei Liu Prof. Chang‐Lin Tian 《Angewandte Chemie (International ed. in English)》2015,54(48):14276-14281
Disulfide‐rich peptides containing three or more disulfide bonds are promising therapeutic and diagnostic agents, but their preparation is often limited by the tedious and low‐yielding folding process. We found that a single cystine‐to‐diaminodiacid replacement could significantly increase the folding efficiency of disulfide‐rich peptides and thus improve their production yields. The practicality of this strategy was demonstrated by the synthesis and folding of derivatives of the μ‐conotoxin SIIIA, the preclinical hormone hepcidin, and the trypsin inhibitor EETI‐II. NMR and X‐ray crystallography studies confirmed that these derivatives of disulfide‐rich peptide retained the correct three‐dimensional conformations. Moreover, the cystine‐to‐diaminodiacid replacement enabled structural tuning, thereby leading to an EETI‐II derivative with higher bioactivity than the native peptide. 相似文献
996.
Crystalline Hetero‐Stereocomplexed Polycarbonates Produced from Amorphous Opposite Enantiomers Having Different Chemical Structures 下载免费PDF全文
Dr. Ye Liu Meng Wang Wei‐Min Ren Yue‐Chao Xu Prof. Dr. Xiao‐Bing Lu 《Angewandte Chemie (International ed. in English)》2015,54(24):7042-7046
Stereocomplexation is the stereoselective interaction between two opposite enantiomeric polymers through an interlocked orderly assembly. Most studies focus on the stereocomplex formation from the crystalline opposite enantiomers having the identical structure; nevertheless, rare examples were reported regarding the crystalline stereocomplexes from enantiomeric polymers having different chemical structures. Herein we show a strategy for polymer orderly assembly through the formation of crystalline hetero‐stereocomplexed polymeric materials by the cocrystallization of amorphous isotactic polycarbonates with different chemical structures and opposite configurations. The behaviors in the crystalline state are significantly different from that of the component enantiomeric polymers or their homo‐stereocomplexes. This study is expected to open up a new way to prepare various semicrystalline materials having a wide variety of physical properties and degradability. 相似文献
997.
A Chemically Triggered and Thermally Switched Dielectric Constant Transition in a Metal Cyanide Based Crystal 下载免费PDF全文
Chao Shi Xi Zhang Ying Cai Prof. Ye‐Feng Yao Prof. Wen Zhang 《Angewandte Chemie (International ed. in English)》2015,54(21):6206-6210
A dielectric constant transition is chemically triggered and thermally switched in (HPy)2[Na(H2O)Co(CN)6] ( 2 , HPy=pyridinium cation) by single‐crystal‐to‐single‐crystal transformation and structural phase transition, respectively. Upon dehydration, (HPy)2[Na(H2O)2Co(CN)6] ( 1 ) transforms to its semi‐hydrated form 2 , accompanying a transition from a low‐dielectric state to a high‐dielectric state, and vice versa. This dielectric switch is also realized by a structural phase transition in 2 that occurs between room‐ and low‐temperature phases, and which corresponds to high‐ and low‐dielectric states, respectively. The switching property is due to the variation in the environment surrounding the HPy cation, that is, the hydrogen‐bonding interactions and the crystal packing, which exert predominant influences on the dynamics of the cations that transit between the static and motional states. 相似文献
998.
Direct Detection of the Superoxide Anion as a Stable Intermediate in the Electroreduction of Oxygen in a Non‐Aqueous Electrolyte Containing Phenol as a Proton Source 下载免费PDF全文
Prof. Zhangquan Peng Dr. Yuhui Chen Prof. Peter G. Bruce Prof. Ye Xu 《Angewandte Chemie (International ed. in English)》2015,54(28):8165-8168
The non‐aqueous Li–air (O2) battery has attracted intensive interest because it can potentially store far more energy than today′s batteries. Presently Li–O2 batteries suffer from parasitic reactions owing to impurities, found in almost all non‐aqueous electrolytes. Impurities include residual protons and protic compounds that can react with oxygen species, such as the superoxide (O2?), a reactive, one‐electron reduction product of oxygen. To avoid the parasitic reactions, it is crucial to have a fundamental understanding of the conditions under which reactive oxygen species are generated in non‐aqueous electrolytes. Herein we report an in situ spectroscopic study of oxygen reduction on gold in a dimethyl sulfoxide electrolyte containing phenol as a proton source. It is shown directly that O2?, not HO2, is the first stable intermediate during the oxygen reduction process to hydrogen peroxide. The unusual stability of O2? is explained using density functional theory (DFT) calculations. 相似文献
999.
Copper‐Catalyzed Trifluoromethylazidation of Alkynes: Efficient Access to CF3‐Substituted Azirines and Aziridines 下载免费PDF全文
Fei Wang Na Zhu Dr. Pinhong Chen Prof. Dr. Jinxing Ye Prof. Dr. Guosheng Liu 《Angewandte Chemie (International ed. in English)》2015,54(32):9356-9360
A novel method for convenient access to CF3‐containing azirines has been developed, and involves a copper‐catalyzed trifluoromethylazidation of alkynes and a photocatalyzed rearrangement. Both terminal and internal alkynes are compatible with the mild reaction conditions, thus delivering the CF3‐containing azirines in moderate to good yields. The azirines can be converted into various CF3‐substituted aziridines. 相似文献
1000.
Flexible,Stretchable, and Rechargeable Fiber‐Shaped Zinc–Air Battery Based on Cross‐Stacked Carbon Nanotube Sheets 下载免费PDF全文
Yifan Xu Ye Zhang Ziyang Guo Jing Ren Prof. Yonggang Wang Prof. Huisheng Peng 《Angewandte Chemie (International ed. in English)》2015,54(51):15390-15394
The fabrication of flexible, stretchable and rechargeable devices with a high energy density is critical for next‐generation electronics. Herein, fiber‐shaped Zn–air batteries, are realized for the first time by designing aligned, cross‐stacked and porous carbon nanotube sheets simultaneously that behave as a gas diffusion layer, a catalyst layer, and a current collector. The combined remarkable electronic and mechanical properties of the aligned carbon nanotube sheets endow good electrochemical properties. They display excellent discharge and charge performances at a high current density of 2 A g?1. They are also flexible and stretchable, which is particularly promising to power portable and wearable electronic devices. 相似文献