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151.
Empirical study and prediction of contact angle and surface free energy of commonly used plastics with pillar‐like structure 下载免费PDF全文
An effective approach is proposed to estimate liquids' contact angles on five commonly used plastics, polyethylene terephthalate, polypropylene, high‐density polyethylene, low‐density polyethylene, and polyvinyl chloride, with pillar‐like structures. A change in liquid droplets' three‐phase contact line due to surface roughness has been proposed in literatures. In this article, contact length ratio, σ, was used as a parameter corresponding to a specific dimension of the pillar‐like structure. Wettability of these rough plastics and their surface free energy were investigated by liquids with various polarities—de‐ionized water (polar), ethylene glycol (monopolar), and α‐bromonaphthalene (apolar). The effects of pillar‐like structures on liquids' contact angles and plastics' surface free energy were studied, and the results reveal that both effects are linear in the range of σ = 1.0 to 1.96. Linear regression models are hence proposed to predict liquids' contact angles, and accuracies are confirmed by less than 6% error for most plastic–liquid combinations. Plastics' surface free energy is also predicted by linear regression models, and the results agree with existing experimental data. Plastic–liquid interactions were also studied, and the results further validate predictions of plastics' surface free energy. In addition, plastics' polarity alteration due to effects of pillar‐like structure were analyzed and reported in this article. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
152.
Wang CF Chiou SF Ko FH Chen JK Chou CT Huang CF Kuo SW Chang FC 《Langmuir : the ACS journal of surfaces and colloids》2007,23(11):5868-5871
One of the most important tasks remaining to be resolved in nanoimprint lithography is the elimination of the resist sticking to the mold during demolding. Previously, the main approach was to apply a thin layer of fluorinated alkyl silane mold-release agent on the surface on the mold; however, this involves complicated steps and high costs. The low surface free energy material polybenzoxazine provides an efficient mold-release agent for silicon molds that is easier to process, costs less, and has no side reactions. 相似文献
153.
154.
Wei‐Jan Huang OmV. Singh Chung‐Hsiung Chen Sheng‐You Chiou Shoei‐Sheng Lee 《Helvetica chimica acta》2002,85(4):1069-1078
Oxidation of N‐methyltetrahydroisoquinolines with iodosylbenzene in the presence of a catalytic amount of tetrabutylammonium iodide in various solvents afforded N‐methyl‐2H‐3,4‐dihydroisoquinol‐1‐ones in almost quantitative yields. The application of this finding to the oxidation of other isoquinolines, including tetrahydroisoquinolines, lycorine diacetate, and benzyltetrahydroisoquinolines, also afforded the corresponding lactams in good yields, however, accompanied by a few minor byproducts. Under similar conditions, tetrahydroberberine gave a rearranged compound, berberal, as the major product, accompanied by 8‐oxoberberine and berberine. 相似文献
155.
Wang Wen-Yi Chiou Jia-Chi Chen Wan-Xue Yu Jia-Li Kan Chi-Wai 《Cellulose (London, England)》2022,29(2):1249-1262
Cellulose - Textile industry is one of the most polluting industries due to the large quantities of dyeing wastewater it generates and discharges. Herein, we report an eco-friendly and sustainable... 相似文献
156.
Src, a nonreceptor tyrosine kinase, was the first oncogene identified from an oncogenic virus. Mechanistic studies of Src-induced transformations aid in understanding the pathologic processes underlying tumorigenesis and may provide new strategies for cancer therapy. Although several pathways and protein modifications are reportedly involved in Src-induced transformation, the detailed mechanisms of their regulation remain unclear. Protein methylation is an important PTM that is widely involved in cellular physiology. In this study, we determined if protein methylation was involved in Src activation and which methylated proteins were associated with this activity. Using in vitro methylation and 2-DE analysis of viral Src (v-Src)-transformed rat kidney epithelial cells (RK3E), several known and novel methylated proteins were identified based on their changes in methylation signal intensity upon transformation. Among these, elongation factor 2 (EF-2), heterogeneous nuclear ribonucleoprotein K (hnRNP K), and β-tubulin protein expressions remained unchanged, indicating that their altered methylation levels were due to Src activation. In addition, the altered expression of β-actin, vimentin, and protein phosphatase 2, catalytic subunit (PPP2C) as well as protein phosphatase 2, catalytic subunit methylation were also confirmed in RK3E cells transformed with a human oncogenic Src mutant (Src531), supporting their association with Src-induced transformation in human cancer. Together, we showed putative involvement of protein methylation in Src activation and our identification of methylated proteins provides important targets for extensively studying Src-induced transformations. 相似文献
157.
Multisubstituted pyrroles are important fragments that appear in many bioactive small molecule scaffolds. Efficient synthesis of multisubstituted pyrroles with different substituents from easily accessible starting materials is challenging. Herein, we describe a metal-free method for the preparation of pentasubstituted pyrroles and hexasubstituted pyrrolines with different substituents and a free amino group by a base-promoted cascade addition–cyclization of propargylamides or allenamides with trimethylsilyl cyanide. This method would complement previous methods and support expansion of the toolbox for the synthesis of valuable, but previously inaccessible, highly substituted pyrroles and pyrrolines. Mechanistic studies to elucidate the reaction pathway have been conducted.This method is a toolbox for the synthesis of valuable, but previously inaccessible, highly substituted pyrroles and pyrrolines.Pyrroles are molecules of great interest in a variety of compounds including pharmaceuticals, natural products and other materials. Pyrrole fragments for example are key motifs in bioactive natural molecules, forming the subunit of heme, chlorophyll and bile pigments, and are also found in many clinical drugs, including those in Fig. 1a.1 Although many classical methods of pyrrole synthesis, including the Paal–Knorr condensation,2 the Knorr reaction,3 the Hantzsch reaction,4 transition metal-catalyzed reactions,5 and multicomponent coupling reactions,6 have been developed over many years, the efficient synthesis of multisubstituted pyrroles is still challenging. In condensation syntheses of pyrroles, the major problems lie in the extended syntheses of complex precursors and limited substitution patterns that are allowed. Multicomponent reactions are superior when building pyrrole core structures with more substituents. Among these, the [2+2+1] cycloaddition reaction of alkynes and primary amines is attractive because of the readily available alkyne and amine substrates and the ability to construct fully substituted pyrroles.7 However, with the exception of some rare examples,8 most [2+2+1] cycloaddition reactions afford pyrroles with two or more identical substituents. The synthesis of multisubstituted pyrroles with all different substituents from simple starting materials therefore remains a major challenge.Open in a separate windowFig. 1Previous reports and this work on propargylamides transformation.Easily accessible propargylamides are classical, privileged building blocks broadly utilized for the synthesis of a large variety of heterocyclic molecules such as pyrroles, pyridines, thiazoles, oxazoles and other relevant organic frameworks.9 For example, Looper10et al. reported the synthesis of 2-aminoimidazoles from propargyl cyanamides and Eycken11 reported a method starting from propargyl guanidines which undergo a 5-exo-dig heterocyclization as shown in Fig. 1b. Subsequently, Wan12et al. revealed the cyclization of N-alkenyl propargyl sulfonamides into pyrroles via sulfonyl migration. Inspired by these transformations and multi-substituted pyrrole synthesis, we report herein a direct synthesis of pentasubstituted pyrroles and hexasubstituted pyrrolines with all different substituents from propargyl sulfonylamides and allenamides.Previously, Zhu,13 Ji14 and Qiu13b,15 reported efficient syntheses of 2-aminopyrroles from isocyanides. Ye16 and Huang17 independently developed gold-catalyzed syntheses of 2-amino-pentasubstituted pyrroles with ynamides. Despite the many advantages of these methods, they all afford protected amines, rather than free amines. The deprotection of these amines may cause problems in further transformations of the products. Our method delivers pyrroles with an unprotected free amino group and are often complementary to the previously well-developed classical methods.Initially, the cyclization reaction of N-(1,3-diphenylprop-2-yn-1-yl)-N-ethylbenzenesulfonamide (1a) with trimethylsilyl cyanide (TMSCN) was carried out with Ni(PPh3)2Cl2 as a catalyst, a base (Cs2CO3) and DMF as a solvent. Different metal catalysts, such as Ni(PPh3)2Cl2, Pd(OAc)2, Cu(OAc)2, and Co(OAc)2 provided the desired product with similar yields ( Entry Cat. Base Solvent Yield 1 Ni(PPh3)2Cl2 Cs2CO3 DMF 67% 2 Pd(OAc)2 Cs2CO3 DMF 65% 3 Cu(OAc)2 Cs2CO3 DMF 65% 4 Co(OAc)2 Cs2CO3 DMF 63% 5 Cs2CO3 DMF 65% 6 KF DMF Trace 7 K3PO4 DMF Trace 8 K2CO3 DMF 48% 9 KOH DMF 52% 10 KOtBu DMF 46% 11 Et3N DMF Trace 12 Cs2CO3 CH3CN 18% 13 Cs2CO3 DME 23% 14 Cs2CO3 Toluene Trace 15 Cs2CO3 DCE Trace 16 Cs2CO3 Dioxane Trace