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961.
Mengbo Zhou Li Song Feng Niu Kangying Shu Wenxiang Chai 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(5):463-466
In the title CuII complex, [Cu(C19H14O3P)2(C3H7NO)(H2O)2], the molecule is bisected by a twofold axis relating the two 2‐(diphenylphosphoryl)benzoate (ODPPB) ligands. The asymmetric unit consists of a CuII metal centre on the symmetry axis, an ODPPB ligand, one water ligand and one dimethylformamide (DMF) ligand (disordered around the twofold axis). The CuII ion has fivefold coordination provided by two carboxylate O atoms from two ODPPB ligands, two O atoms from two coordinated water molecules and another O atom from a (disordered) DMF molecule, giving a CuO5 square‐pyramidal coordination geometry. The ODPPB ligand adopts a terminal monocoordinated mode with two free O atoms forming two strong intramolecular hydrogen bonds with the coordinated water molecules, which may play a key role in the stability of the molecular structure, as shown by the higher release temperature for the coordinated water molecules than for the coordinated DMF molecule. The optical absorption properties of powder samples of the title compound have also been studied. 相似文献
962.
Jing Zhou Gaoling Zhao Xiaoxiao Ren Bin Song Gaorong Han 《Journal of Sol-Gel Science and Technology》2011,58(1):148-155
In order to clarify the effects of diethanolamine (DEA) in the silver (Ag)/titanium dioxide (TiO2) sol–gel process, sols with and without DEA, and films derived from these sols were prepared. The samples were investigated
by X-ray diffraction, transmission electron microscopy, electron diffraction and optical absorption spectra. The results showed
that metallic Ag clusters were formed in the sol with DEA and was absent in the sol without DEA. This indicated that DEA worked
not only as the stabilizer but also as the reduce agent in Ag/TiO2 sol–gel process. After annealed, Ag metallic nanoparticles were generated in the films derived from both the sols with and
without DEA. The particles in the films derived from the sol with DEA were smaller than those from the sol without DEA. This
can be ascribed to the limitation of the growth of Ag cluster formed in the sol with DEA during heat treatment. Mechanisms
for the formation of metallic Ag in the Ag/TiO2 sols and films were discussed. The effects of DEA in the sols and films were studied in detail. 相似文献
963.
964.
965.
In vivo near-infrared Raman spectroscopy: demonstration of feasibility during clinical gastrointestinal endoscopy 总被引:7,自引:0,他引:7
Raman spectroscopy (RS) has potential for disease classification within the gastrointestinal tract (GI). A near-infrared (NIR) fiber-optic RS system has been developed previously. This study reports the first in vivo Raman spectra of human gastrointestinal tissues measured during routine clinical endoscopy. This was achieved by using this system with a fiber-optic probe that was passed through the endoscope instrument channel and placed in contact with the tissue surface. Spectra could be obtained with good signal-to-noise ratio in 5 s. The effects on the spectra of varying the pressure of the probe tip on the tissue and of the probe-tissue angle were determined and shown to be insignificant. The limited set of spectra from normal and diseased tissues revealed only subtle differences. Therefore, powerful spectral-sorting algorithms, successfully implemented in prior ex vivo studies, are required to realize the full diagnostic potential of RS for tissue classification in the GI. 相似文献
966.
Zhishan Su Dr. Song Qin Dr. Changwei Hu Prof. Dr. Xiaoming Feng Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(14):4359-4367
The mechanism of the hetero‐Diels–Alder reactions of Brassard’s diene and 1,3‐butadiene catalyzed by a titanium(IV) complex of a tridentate Schiff base was investigated by DFT and ONIOM methods. The calculations indicate that the mechanism of the reaction is closely related to the nucleophilicity–electrophilicity between diene and carbonyl substrates. A stepwise pathway is adopted for Brassard’s diene, and the step corresponding to the formation of the C? C bond is predicted to be the rate‐determining step with a free‐energy barrier of 8.4 kcal mol?1. For 1,3‐butadiene, the reaction takes place along a one‐step, two‐stage pathway with a free‐energy barrier of 14.9 kcal mol?1. For Brassard’s diene as substrate, the OCH3 and OSi(CH3)3 substituents may play a key role in the formation of the transition state and zwitterionic intermediate by participating in charge transfer from Brassard’s diene to formaldehyde. The combination of the phenyl groups at the amino alcohol moiety and the ortho‐tert‐butyl group of the salicylaldehyde moiety in the chiral tridentate Schiff base ligand plays an important role in the control of the stereoselectivity, which is in agreement with experimental observations. 相似文献
967.
Three pyridyl functionalized bis(pyrazol‐1‐yl)methanes, namely 2‐[(4‐pyridyl)methoxyphenyl] bis(pyrazol‐1‐yl)methane (L1), 2‐[(4‐pyridyl)methoxyphenyl]bis(3,5‐dimethylpyrazol‐1‐yl)methane (L2) and 2‐[(3‐pyridyl)methoxyphenyl]bis(pyrazol‐1‐yl)methane (L3) have been synthesized by the reactions of (2‐hydroxyphenyl)bis(pyrazol‐1‐yl)methanes with chloromethylpyridine. Treatment of these three ligands with R2SnCl2 (R = Et, n‐Bu or Ph) yields a series of symmetric 2:1 adducts of (L)2SnR2Cl2 (L = L1, L2 or L3), which have been confirmed by elemental analysis and NMR spectroscopy. The crystal structures of (L2)2Sn(n‐Bu)2Cl2·0.5C6H14 and (L3)2SnEt2Cl2 determined by X‐ray crystallography show that the functionalized bis(pyrazol‐1‐yl)methane acts as a monodentate ligand through the pyridyl nitrogen atom, and the pyrazolyl nitrogen atoms do not coordinate to the tin atom. The cytotoxic activity of these complexes for Hela cells in vitro was tested. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
968.
Fan Xia Dr. Xu Hou Liuxuan Cao Lin Wang Jianming Xue Prof. Guangzhao Zhang Prof. Yanlin Song Prof. Daoben Zhu Prof. Yugang Wang Prof. Lei Jiang Prof. 《Chemphyschem》2010,11(4):859-864
Herein we demonstrate a fully abiotic smart single‐nanopore device that rectifies ionic current in response to the temperature. The temperature‐responsive nanopore ionic rectifier can be switched between a rectifying state below 34 °C and a non‐rectifying state above 38 °C actuated by the phase transition of the poly(N‐isopropylacrylamide) [PNIPAM] brushes. On the rectifying state, the rectifying efficiency can be enhanced by the dehydration of the attached PNIPAM brushes below the LCST. When the PNIPAM brushes have sufficiently collapsed, the nanopore switches to the non‐rectifying state. The concept of the temperature‐responsive current rectification in chemically‐modified nanopores paves a new way for controlling the preferential direction of the ion transport in nanofluidics by modulating the temperature, which has the potential to build novel nanomachines with smart fluidic communication functions for future lab‐on‐chip devices. 相似文献
969.
Chao Zhao Konggang Qu Yujun Song Can Xu Jinsong Ren Prof. Xiaogang Qu Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(27):8147-8154
Here we report a reusable DNA single‐walled carbon nanotube (SWNT)‐based fluorescent sensor for highly sensitive and selective detection of Ag+ and cysteine (Cys) in aqueous solution. SWNTs can effectively quench the fluorescence of dye‐labeled single‐stranded DNA due to their strong π–π stacking interactions. However, upon incubation with Ag+, Ag+ can induce stable duplex formation mediated by C–Ag+–C (C=cytosine) coordination chemistry, which has been further confirmed by DNA melting studies. This weakens the interactions between DNA and SWNTs, and thus activates the sensor fluorescence. On the other hand, because Cys is a strong Ag+ binder, it can remove Ag+ from C–Ag+–C base pairs and deactivates the sensor fluorescence by rewrapping the dye‐labeled oligonucleotides around the SWNT. In this way, the fluorescence signal‐on and signal‐off of a DNA/SWNT sensor can be used to detect aqueous Ag+ and Cys, respectively. This sensing platform exhibits high sensitivity and selectivity toward Ag+ and Cys versus other metal ions and the other 19 natural amino acids, with a limit of detection of 1 nM for Ag+ and 9.5 nM for Cys. Based on these results, we have constructed a reusable fluorescent sensor by using the covalent‐linked SWNT–DNA conjugates according to the same sensing mechanism. There is no report on the use of SWNT–DNA assays for the detection of Ag+ and Cys. This assay is simple, effective, and reusable, and can in principle be used to detect other metal ions by substituting C–C base pairs with other native or artificial bases that selectively bind to other metal ions. 相似文献
970.