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991.
We describe a Rh-catalyzed desymmetrization of all-carbon quaternary centers from α,α-bis(allyl)aldehydes by a cascade featuring isomerization and hydroacylation. This desymmetrization competes with two other novel olefin functionalizations that are triggered by C–H bond activation, including carboacylation and bisacylation. A BIPHEP ligand promotes enantioselective formation of α-vinylcyclopentanones. Mechanistic studies support irreversible and enantioselective olefin-isomerization followed by olefin-hydroacylation. 相似文献
992.
Studying protein ubiquitination is difficult due to the complexity of the E1–E2–E3 ubiquitination cascade. Here we report the discovery that C-terminal ubiquitin thioesters can undergo direct transthiolation with the catalytic cysteine of the model HECT E3 ubiquitin ligase Rsp5 to form a catalytically active Rsp5∼ubiquitin thioester (Rsp5∼Ub). The resulting Rsp5∼Ub undergoes efficient autoubiquitination, ubiquitinates protein substrates, and synthesizes polyubiquitin chains with native Ub isopeptide linkage specificity. Since the developed chemical system bypasses the need for ATP, E1 and E2 enzymes while maintaining the native HECT E3 mechanism, we named it “Bypassing System” (ByS). Importantly, ByS provides direct evidence that E2 enzymes are dispensable for K63 specific isopeptide bond formation between ubiquitin molecules by Rsp5 in vitro. Additionally, six other E3 enzymes including Nedd4-1, Nedd4-2, Itch, and Wwp1 HECT ligases, along with Parkin and HHARI RBR ligases processed Ub thioesters under ByS reaction conditions. These findings provide general mechanistic insights on protein ubiquitination, and offer new strategies for assay development to discover pharmacological modulators of E3 enzymes. 相似文献
993.
Rücktitelbild: Cofactor‐Free Light‐Driven Whole‐Cell Cytochrome P450 Catalysis (Angew. Chem. 3/2015)
994.
Synthesis and antibacterial activity of versatile substrate‐coated biocidal material via catechol chemistry 下载免费PDF全文
Shazid Md. Sharker So Yeong Lee Insik In Sung Young Park 《Surface and interface analysis : SIA》2015,47(2):259-264
We report a potential coating material showing durable and significant antimicrobial activity for preserving the surfaces of a broad range of materials. The structure of the prepared antimicrobial adhesive material features a catechol moiety of dopamine hydrochloride conjugated to 4‐bromobutanoyl chloride as an adhesive material. Antimicrobial properties against a wide range of microorganism species are achieved by quaternizing a long hydrophobic chain (N,N'‐dimethyldecylamine) onto 3,4‐dihydroxyphenylalanine (Dopa) to afford the prepared material (Dopa‐decyl). The successful formation of Dopa‐decyl is confirmed by hydrogen nuclear magnetic resonance (1H‐NMR) and attenuated total reflectance‐infrared (ATR‐IR) measurements. The chemical composition of the quaternized adhesive material (Dopa‐decyl) is characterized by X‐ray photoelectron spectroscopy (XPS). Investigation of the antimicrobial activity of the Dopa‐decyl‐coated film against both gram‐positive Staphylococcus aureus (S. aureus) and gram‐negative Escherichia coli (E. coli) stains reveals a highly efficient antimicrobial effect under both normal and extreme stress conditions due to the biocidal effect of the quaternized amine when the materials are applied on the surface of various substrates. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Hiroshi Mizoguchi SangWon Park Haruhiro Hiraka Kazutaka Ikeda Toshiya Otomo Hideo Hosono 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(10):2975-2978
Using a high pressure technique and the strong donating nature of H−, a new series of tetragonal La2Fe2Se2O3‐type layered mixed‐anion arsenides, Ln2M2As2Hx, was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x≈3). In these compounds, an unusual M2H square net, which has anti CuO2 square net structures accompanying two As3− ions, is sandwiched by (LaH)2 fluorite layers. Notably, strong metal–metal bonding with a distance of 2.80 Å was confirmed in La2Ti2As2H2.3, which has metallic properties. In fact, these compounds are situated near the boundary between salt‐like ionic hydrides and transition‐metal hydrides with metallic characters. 相似文献
999.
Fluorescence Polarization Based Nucleic Acid Testing for Rapid and Cost‐Effective Diagnosis of Infectious Disease 下载免费PDF全文
Dr. Ki Soo Park Prof. Richelle C. Charles Prof. Edward T. Ryan Prof. Ralph Weissleder Prof. Hakho Lee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16359-16363
A new nucleic acid detection method was developed for a rapid and cost‐effective diagnosis of infectious disease. This approach relies on the three unique elements: 1) detection probes that regulate DNA polymerase activity in response to the complementary target DNA; 2) universal reporters conjugated with a single fluorophore; and 3) fluorescence polarization (FP) detection. As a proof‐of‐concept, the assay was used to detect and sub‐type Salmonella bacteria with sensitivities down to a single bacterium in less than three hours. 相似文献
1000.
Kabindra Kafle Yong Bum Park Christopher M. Lee Joshua J. Stapleton Sarah N. Kiemle Daniel J. Cosgrove Seong H. Kim 《Cellulose (London, England)》2017,24(8):3145-3154
The organization of polysaccharides in plant cell walls is important for the mechanics of plant cells. Spectral analysis of cell walls by polarized IR can reveal polysaccharide organization, but may be complicated by dipoles not aligned with the backbone. For instance, analysis of uniaxially-aligned cellulose Iβ film revealed that the dipole transition vector of the 1160 cm?1 band involving stretch vibrations of glycosidic C1–O–C4 linkages is approximately at 30° with respect to the backbone of the cellulose chain, because of coupling with C5–O–C1 bonds in the six-membered rings. In the case of homogalacturonan, the dipole transition vector of the ester carbonyl group vibration (νC=O, 1745 cm?1) is expected to be nearly normal to the homogalacturonan backbone. Using this information and the dichroism equation, the change in net orientation of cell wall polymers upon mechanical stretch was determined by polarized IR analysis. Never-dried abaxial outer epidermal cell walls of the second scale of onion bulb were mechanically stretched along longitudinal or transverse directions with respect to the long axis of the cells and then dried while under mechanical stretch. The average orientations of both 1160 and 1745 cm?1 vibration transition dipoles were rotated by ~5° and ~4°, respectively, along the stretch direction from their initial random distributions upon longitudinal strain by 14%; and by ~4° and ~3°, respectively, upon transverse strain by 12%. These results imply that both cellulose microfibrils and pectins in the cell wall are passively realigned along the stretch direction by external mechanical force. The analytical methodology developed here will be useful to study how cell wall polymers might reorganize during cell wall growth and development. 相似文献