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991.
Alexander Perjéssy Tran Thi Tuu Dušan Loos Viktor Sutoris 《Monatshefte für Chemie / Chemical Monthly》1988,119(4):477-486
The C=O stretching frequencies ofE-3-(2-R-vinyl)-2-benzothiazolinones (1 a–1 p) were measured in CCl4 and CHCl3 and correlated with + and * substituent constants. Thev(C=O) vs * (R) correlation was compared to an analogical relationship obtained with 3-R-2-benzothiazolinones (2). The electronic structure and geometry of compounds was investigated by CNDO/2 and PCILO methods. The results of both the spectral and theoretical studies showed forE-3-(2-R-vinyl)-2-benzothiazolinones a preference of the N—C-s-cis conformation (3), in which the substituent effects are transmitted to the C=O group very efficiently. The transmission factor for the CH=CH group was determined according to the definition ofJaffé. The role of inductive effects, delocalization of the nitrogen lone-pair electrons as well as the through-space interaction between the C=O and C=C bonds is discussed in terms of transmission mechanism and structural properties.
Infrarotspektren und theoretische Untersuchungen vonE-3-(2-R-vinyl)-2-benzo-thiazolinonen
Zusammenfassung Es wurden die C=O-Streckfrequenzen vonE-3-(2-R-vinyl)-2-benzothiazolinonen (1 a–1 p) in CCl4 und CHCl3 gemessen und mit -, +- und *-Substitutionskonstanten korreliert. Diev(C=O)-*-Korrelation wurde mit einer analogen Beziehung für 3-R-Benzothiazolinonen (2) verglichen. Die elektronische Struktur und die Geometrie der Verbindungen wurden mittels CNDO/2- und PCILO-Berechnungen untersucht. Es ergab sich dabei sowohl aus den spektros-kopischen als auch aus den theoretischen Ergebnissen eine N—C-s-cis-Konformation (3) für dieE-3-(2-R-vinyl)-2-benzothiazolinone, da dies eine günstige Geometrie zur Übermittlung von Substitutionseffekten zur C=O-Gruppe ergibt. Der Transmissionsfaktor für die CH=CH-Gruppe wurde nach der Definition vonJaffé bestimmt. Die Rolle von induktiven Effekten, der Delokalisierung des freien Elektronenpaares am Stickstoff und der C=O....C=C-Wechselwirkungen durch den Raum wurde auf Basis von Transmissionsmechanismen und strukturellen Eigenschaften diskutiert.相似文献
992.
A. Braileanu M. Zaharescu D. CriŞan D. FĂtu E. Segal C. Danciulescu 《Journal of Thermal Analysis and Calorimetry》1996,47(2):569-575
Former studies concerning the formation of the compounds in the pseudobinary systems of Bi2O3-MO type (M =Ca, Sr, Ca+Sr) have shown that the reaction which occurs with the highest rate is that between Bi2O3 and CaO. In the present work CaCO3 was used as CaO source. We carried out an investigation of the thermal decomposition of CaCO3 in the presence of Bi2O3 in comparison with the decomposition of pure CaCO3.The presence of Bi2O3 exerts a complex influence on the CaCO3 decomposition acting on the nucleation as well as on the diffusion of CO2. The decomposition of the samples with low Bi2O3 content follows the mechanism of a contracting sphere. A change from surface nucleation to bulk nucleation is recorded for higher amounts of Bi2O3. 相似文献
993.
Vratislav Langer Jan Kes?an
ubomír Smr
ok 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(9):i83-i84
The structure of γ‐alumina (Al21+1/3□2+2/3O32) crystals obtained as a product of a corrosion reaction between β‐sialon and steel was refined in the space group Fdm. The oxygen sublattice is fully occupied. The refined occupancy parameters are 0.83 (3), 0.818 (13), 0.066 (14) and 0.044 (18) for Al ions in 8a, 16d, 16c and 48f positions, respectively. The Al ions are distributed over octahedral and tetrahedral sites in a 63:37 ratio, with 6% of all Al ions occupying non‐spinel positions. 相似文献
994.
Neuhoff Nv Kaiser T Wittke S Krebs R Pitt A Burchard A Sundmacher A Schlegelberger B Kolch W Mischak H 《Rapid communications in mass spectrometry : RCM》2004,18(2):149-156
The discovery of biomarkers is currently attracting much interest as it harbors great potential for the diagnosis and monitoring of human diseases. Here we have used two advanced mass spectroscopy based technologies, surface enhanced laser desorption ionization (SELDI-MS) and capillary electrophoresis/mass spectrometry (CE/MS), to obtain proteomic patterns of urine samples from patients suffering from membranous glomerulonephritis (MGN) and healthy volunteers. The results indicate that CE/MS analysis is able to display a rich and complex pattern of polypeptides with high resolution and high mass accuracy. In order to analyze these patterns, the MosaiqueVisu software was developed for peak identification, deconvolution and the display of refined maps in a three-dimensional format. The polypeptide profiles obtained with SELDI-MS from the same samples are much sparser and show lower resolution and mass accuracy. The SELDI-MS profiles are further heavily dependent on analyte concentration. SELDI-MS analysis identified three differentially expressed polypeptides, which are potential biomarkers that can distinguish healthy donors from patients with MGN. In contrast, approximately 200 potential biomarkers could be identified by CE/MS. Thus, while SELDI-MS is easy to use and requires very little sample, CE/MS generates much richer data sets that enable an in-depth analysis. 相似文献
995.
Gilbert B Zhang H Huang F Banfield JF Ren Y Haskel D Lang JC Srajer G Jürgensen A Waychunas GA 《The Journal of chemical physics》2004,120(24):11785-11795
A room temperature solid-state structural transformation was observed in 3 nm ZnS nanoparticles in methanol following the addition of water (Zhang et al., Nature 424, 1025, 2003). Experimental wide angle x-ray scattering (WAXS), x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectroscopy measurements show a large increase in crystallinity associated with water addition, in agreement with molecular dynamics (MD) predictions. Here we perform first-shell EXAFS and pair distribution function analysis and whole-nanoparticle calculations of WAXS, EXAFS and XANES to compare structural data with the MD predictions. The predicted WAXS patterns give excellent agreement with data, while the predicted EXAFS and XANES spectra give poor agreement. Relative to WAXS, XANES and EXAFS spectra contain additional structural information related to the distribution of disorder. The discrepancy between the x-ray diffraction and x-ray absorption results indicates that structural disorder is partitioned between interior and surface regions more strongly than predicted in the MD simulations. 相似文献
996.
Astrid Malassa Helmar Grls Axel Buchholz Winfried Plass Matthias Westerhausen 《无机化学与普通化学杂志》2006,632(14):2355-2362
2‐Pyridylmethylamine (amp) and 8‐aminochinoline (ach) readily form the following complexes with iron halides in methanol: [(amp)2FeCl2] ( 1a ), [(amp)2FeBr2] ( 1b ), [(ach)2Fe(MeOH)2]Br2 ( 1c ), and [(amp)FeCl2(μ‐OMe)]2 ( 2 ). Methanol was chosen as a solvent because these reactions are rather complex in ether. For example, FeCl3 forms the ionic complex pair [(dme)2FeCl2] [FeCl4] ( 3 ) with 1,2‐dimethoxyethane (dme). The reaction of FeBr2 with tridentate di(2‐pyridylmethyl)amine (dpa) and tetradentate 1,2‐dipyridyl‐1,2‐diaminoethane (dpdae) yields the complexes [(dpa)2Fe]Br2·2 MeOH ( 4 ) and [(dpdae)2Fe] [FeBr4] ( 5 ), respectively. Crystallographic and magnetochemical investigations show the high‐spin configuration for the complexes 1 and 2 , whereas the short Fe‐N distances of 4 clearly indicate a low‐spin state. Compound 2 exhibits an antiferromagnetic exchange interaction with a coupling constant J = ?29.4 cm?1 (H;af = ?J S;afA·S;afB). 相似文献
997.
U. an der Heiden 《Journal of Mathematical Analysis and Applications》1979,70(2):599-609
It is proved that the autonomous difference-differential equation
(0) has, for a broad class of functions f, a nonconstant periodic solution whenever the associated characteristic equation has a root with positive real part. 相似文献
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998.
A stepwise experimental and mathematical modeling approach was used to assess silver release from nanocomposite Ag/alginate microbeads in wet and dried forms into water and into normal saline solution chosen as a simplified model for certain biological fluids (e.g., blood plasma, wound exudates, sweat, etc). Three phenomena were connected and mathematically described: diffusion of silver nanoparticles (AgNPs) within the alginate hydrogel, AgNP oxidation/dissolution and reaction with chloride ions, and diffusion of the resultant silver-chloride species. Mathematical modeling results agreed well with the experimental data with the AgNP diffusion coefficient estimated as 1.3 × 10?18 m2 s?1, while the first-order kinetic rate constant of AgNP oxidation/dissolution and diffusivity of silver-chloride species were shown to be inversely related. In specific, rapid rehydration and swelling of dry Ag/alginate microbeads induced fast AgNP oxidation/dissolution reaction with Cl? and AgCl precipitation within the microbeads with the lowest diffusivity of silver-chloride species compared to wet microbeads in normal saline. The proposed mathematical model provided an insight into the phenomena related to silver release from nanocomposite Ca-alginate hydrogels relevant for use of antimicrobial devices and established, at the same time, a basis for further in-depth studies of AgNP interactions in hydrogels in the presence of chloride ions. 相似文献
999.
Gold(I)‐Catalyzed Generation of the Two Components of a Formal [4+2] Cycloaddition Reaction for the Synthesis of Tetracyclic Pyrano[2,3,4‐de]chromenes 下载免费PDF全文
Dr. Tamara Arto Prof. Dr. Francisco J. Fañanás Prof. Félix Rodríguez 《Angewandte Chemie (International ed. in English)》2016,55(25):7218-7221
Ortho‐Alkynylbenzaldehydes have been widely used to generate isochromenylium derivatives through gold‐catalyzed cycloisomerization. These isochromenylium derivatives have been exploited as formal diene derivatives for reactions with different dienophiles. Herein, we describe the behavior of ortho‐alkynylsalicylaldehydes, a particular case of ortho‐alkynylbenzaldehydes. The gold‐catalyzed cycloisomerization of ortho‐alkynylsalicylaldehydes delivers an unusual heterodiene derivative that reacts with electron‐rich alkenes through a formal [4+2] cycloaddition. In this reaction, both the diene and dienophile are generated in situ through gold‐catalyzed cycloisomerization of appropriate alkynamines or alkynols. This reaction was used to synthesize complex tetracyclic pyrano[2,3,4‐de]chromenes from two very simple starting materials (an ortho‐alkynylsalicylaldehyde and an alkynamine or alkynol) with complete atom economy and with selective formation of bonds, cycles, and stereocenters. 相似文献
1000.
Emilia I. Wisotzki Ralf P. Friedrich Astrid Weidt Christoph Alexiou Stefan G. Mayr Mareike Zink 《Macromolecular bioscience》2016,16(6):914-924
As a biomaterial, it is well established that gelatin exhibits low cytotoxicity and can promote cellular growth. However, to circumvent the potential toxicity of chemical crosslinkers, reagent‐free crosslinking methods such as electron irradiation are highly desirable. While high energy irradiation has been shown to exhibit precise control over the degree of crosslinking, these hydrogels have not been thoroughly investigated for biocompatibility and degradability. Here, NIH 3T3 murine fibroblasts are seeded onto irradiated gelatin hydrogels to examine the hydrogel's influence on cellular viability and morphology. The average projected area of cells seeded onto the hydrogels increases with irradiation dose, which correlates with an increase in the hydrogel's shear modulus up to 10 kPa. Cells on these hydrogels are highly viable and exhibits normal cell cycles, particularly when compared to those grown on glutaraldehyde crosslinked gelatin hydrogels. However, proliferation is reduced on both types of crosslinked samples. To mimic the response of the hydrogels in physiological conditions, degradability is monitored in simulated body fluid to reveal strongly dose‐dependent degradation times. Overall, given the low cytotoxicity, influence on cellular morphology and variability in degradation times of the electron irradiated gelatin hydrogels, there is significant potential for application in areas ranging from regenerative medicine to mechanobiology.