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101.
102.
Compared to conventional molecular solvents, the ionic liquid [b-3C-im][NTf(2)] was found to promote transimination reactions with up to ~100-fold rate enhancement. This rate effect observed at ambient temperature might be explained by the fact that the ionic liquid displays weak Lewis acidity with very low, if any, nucleophilicity and its imidazolium cation is expected to interact by associating with, and thus electrophilically activating, the C=N bond of the starting imine, leading to increased stabilization of the polar, charged intermediate species and ultimately, rapid product formation. Moreover, the presence of 1 mol% Sc(OTf)(3) in [b-3C-im][NTf(2)] further facilitates the transimination reactions studied. 相似文献
103.
This study describes a simple method for the selective and sensitive detection of cyanide and endogenous biological cyanide using polysorbate 40-stabilized gold nanoparticles. 相似文献
104.
Chi HW Chien YC Liu CY Tseng CJ Lee YJ Chan JL Chu YR Chin DH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(5):1493-1506
The antibiotic neocarzinostatin comprises a carrier protein with a well-defined cavity for accommodating an active enediyne chromophore. The protein has two disulfides, one (Cys(37)-Cys(47)) lies on the cavity bottom and the other (Cys(88)-Cys(93)) in a constrained short loop. When the chromophore is not bound to the protein, a thiol-induced cycloaromatization of the enediyne into a tetrahydroindacene derivative is responsible for the potent antitumor activity. When it is protein-bound, the protein diverts the cycloaromatization pathway to form a distinct hydroxyisochromene-type product. How the protein directs the enediyne chemistry is an interesting puzzle, and various suggestions have been proposed in the past. We screened more than fifty thiols and manipulated conditions to locate reaction features and search for factors that could influence the protein directing strength. Thiol- and oxygen-concentration-dependence studies suggested that disulfides, which maintain the steric rigidity of the protein, could play a key role in diverting the cycloaromatization pathway. For direct proofs, we made mutations at each of the two disulfides by replacing sulfur atoms with oxygen. Circular dichroism and two-dimensional NMR spectroscopy studies suggested that the mutations changed neither the protein conformation nor the ligand interactions. Analyses of the thiol-induced cycloaromatization revealed that rupture of Cys(37)-Cys(47) made the protein almost completely lose its chemical directing ability, whereas rupture of Cys(88)-Cys(93) had only a minor influence. The results demonstrated that the steric rigidity of the binding cavity, but not necessary the whole protein, played an important role in the protein-directed mechanism. 相似文献
105.
Tseng CH Chen YL Chung KY Wang CH Peng SI Cheng CM Tzeng CC 《Organic & biomolecular chemistry》2011,9(9):3205-3216
A number of 2,3-diarylquinoline derivatives were synthesized and evaluated for antiproliferative activities against the growth of six cancer cell lines including human hepatocellular carcinoma (Hep G2 and Hep 3B), non-small cell lung cancer (A549 and H1299), and breast cancer (MCF-7 and MDA-MB-231) cell lines. The preliminary results indicated that 6-fluoro-2,3-bis{4-[2-(piperidin-1-yl)ethoxy]phenyl}quinoline (16b) was one of the most active compounds against the growth of Hep 3B, H1299, and MDA-MB-231 with a GI(50) value of 0.71, 1.46, and 0.72 μM respectively which was more active than tamoxifen. Further investigations have shown that 16b induced cell cycle arrest at G2/M phase followed by DNA fragmentation via an increase in the protein expression of Bad, Bax and decrease in Bcl-2, and PARP which consequently cause cell death. 相似文献
106.
Stroke is one of the leading causes of mortality, with a high incidence of severe morbidity in survivors. The treatment to minimize tissue injury after stroke is still unsatisfactory and it is mandatory to develop effective treatment strategies for stroke. The pathophysiology of ischemic stroke is complex and involves many processes including energy failure, loss of ion homeostasis, increased intracellular calcium level, platelet aggregation, production of reactive oxygen species, disruption of blood brain barrier, and inflammation and leukocyte infiltration, etc. Tetrandrine, a bisbenzylisoquinoline alkaloid, has many pharmacologic effects including anti-inflammatory and cytoprotective effects. In addition, tetrandrine has been found to protect the liver, heart, small bowel and brain from ischemia/reperfusion injury. It is a calcium channel blocker, and can inhibit lipid peroxidation, reduce generation of reactive oxygen species, suppress the production of cytokines and inflammatory mediators, inhibit neutrophil recruitment and platelet aggregation, which are all devastating factors during ischemia/reperfusion injury of the brain. Because tetrandrine can counteract these important pathophysiological processes of ischemic stroke, it has the potential to be a protective agent for ischemic stroke. 相似文献
107.
Tseng CM Dyakov YA Huang CL Mebel AM Lin SH Lee YT Ni CK 《Journal of the American Chemical Society》2004,126(28):8760-8768
Photoisomerization and photodissociation of aniline and 4-methylpyridine at 193 nm were studied separately using multimass ion imaging techniques. Photofragment translational energy distributions and dissociation rates were measured. Our results demonstrate that more than 23% of the ground electronic state aniline and 10% of 4-methylpyridine produced from the excitation by 193 nm photons after internal conversion isomerize to seven-membered ring isomers, followed by the H atom migration in the seven-membered ring, and then rearomatize to both methylpyridine and aniline prior to dissociation. The significance of this isomerization is that the carbon, nitrogen, and hydrogen atoms belonging to the alkyl or amino groups are involved in the exchange with those atoms in the aromatic ring during the isomerization. 相似文献
108.
C. -W. Chang Y. -C. Chou J. -M. Tseng M. -Y. Liu C. -M. Shu 《Journal of Thermal Analysis and Calorimetry》2009,95(2):639-643
Many concerns over unsafe or unknown properties of multi-walled carbon nanotubes (MWNTs) have been raised. The thermal characteristics
regarding stability would represent potential hazards during the production or utilization stage and could be determined by
calorimetric tests for various thermokinetic parameters. Differential scanning calorimetry (DSC) was employed to evaluate
the thermokinetic parameters for MWNTs at various compositions.
Thermoanalytical curves showed that the average heat of decomposition (ΔH
d) of the MWNTs samples in a manufacturing process was about 31,723 J g−1, by identifying them as an inherently hazardous material. In this study, significant thermal analysis appeared in the presence
of sulfuric acid (H2SO4). From the DSC experiments, the purification process of MWNTs could induce an unexpected reaction in the condition of batch
addition with reactants of H2SO4. The results can be applied for designing emergency relief system and emergency rescue strategies during a perturbed situation
or accident. 相似文献
109.
Hao Wang Dr. Shutao Wang Dr. Helen Su Dr. Kuan‐Ju Chen Amanda Lee Armijo Wei‐Yu Lin Dr. Yanju Wang Dr. Jing Sun Dr. Ken‐ichiro Kamei Dr. Johannes Czernin Prof. Caius G. Radu Prof. Hsian‐Rong Tseng Prof. 《Angewandte Chemie (International ed. in English)》2009,48(24):4344-4348
A supramolecular approach has been developed for the preparation of supramolecular nanoparticles (SNPs) with variable sizes (30–450 nm) from three different molecular building blocks using a cyclodextrin/adamantane recognition system. Positron emission tomography (PET) was employed to study the biodistribution and lymph node drainage of the SNPs in mice. The sizes of the SNPs affect their in vivo characteristics (see picture).
110.
Jie‐Ru Yeh Fu‐Yuan Tseng Je‐Yuan Yeh Jing‐Cherng Tsai Raymond Chien‐Chao Tsiang 《Journal of polymer science. Part A, Polymer chemistry》2010,48(20):4400-4407
An effective method to synthesize directly a hard composite material containing uniformly dispersed nanogold particles chemically bonded with a stereospecific, crystalline polymer matrix has been developed. Syndiotactic polypropylene was synthesized and functionalized to have a hydroxyl terminal group (sPPOH) via a metallocene catalysis with a selective chain transfer. Next, sPPOH was activated to react with ethylene sulfide forming the thiol‐terminated polymer, sPPSH. sPPSH was then chemically bonded to gold nanoparticles (AuNPs) formed in situ via a reduction of HAuCl4. The bonding between thiol and AuNP stabilized the AuNPs and led to the formation of sPPAuNPs composite containing uniformly‐dispersed AuNPs of a 19–40 nm size without noticeable aggregation. Furthermore, the chemical bonding of AuNPs has afforded sPPAuNPs a thermal degradation temperature (TD) 49.4 °C higher than the pristine sPP or sPPOH and 25.7 °C higher than sPPSH without any adverse effect on the crystalline temperature and melting temperature. In addition, the characteristic UV‐Vis absorption wavelength of sPPAuNPs remains the same at various temperatures, thus indicating the independence of optical property on temperature as well as the good thermal stability of the sPPAuNPs composite. 1H NMR, 13C NMR, FESEM, STEM, XPS, TGA and DSC were used to investigate the molecular structure, morphology and thermal properties of the resulting sPPAuNPs nanocomposite. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献