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排序方式: 共有609条查询结果,搜索用时 15 毫秒
601.
Leandro M. de Carvalho Carine Viana Ana Paula L. Moreira Paulo C. do Nascimento Denise Bohrer Monique J. Motta Géssica D. da Silveira 《Journal of Solid State Electrochemistry》2013,17(6):1601-1608
Herein, we present a new method based on separation by ion-pair chromatography with pulsed amperometric detection for evaluating various diuretics, including hydrochlorothiazide, chlorthalidone, furosemide, and amiloride, which are adulterants in herbal-based pharmaceutical formulations. The amperometric detection cycle (time?=?2 s) was performed at a gold electrode by applying a detection potential (E1) of +800 mV for 0.4 s and an oxidation potential (E2) of +1,000 mV for 0.40 s, followed by a reduction potential (E3) of ?200 mV for 1.20 s. The mobile phase for separating the diuretics was composed of 5 mmol L?1 phosphate buffer and 0.3 mmol L?1 sodium dodecyl sulfate in 50 % (v/v) methanol (pH 4.5). This method enabled the quantification of the drugs at low concentrations (i.e., 0.08 mg/capsule for hydrochlorothiazide, 0.01 mg/capsule for chlorthalidone, and 0.007 mg/capsule for furosemide). Twenty-six herbal formulations were analyzed, and eight samples (30.8 %) were found to contain diuretics that were added to the final composition (declared or not). 相似文献
602.
We report here, for the first time, application of batch injection analysis (BIA) with amperometric detection for determination of the phenolic antioxidant butylated hydroxyanisole (BHA) in biodiesel. A sample plug was directly injected onto a boron-doped diamond electrode immersed in 50% v/v hydroethanolic solution with 0.1 mol L−1 HClO4 using an electronic micropipette. Importantly, the only preparation step required for biodiesel analysis is dilution in the same hydroethanolic electrolyte solution. Our proposed method has several advantages for routine biodiesel analysis, including: a low relative standard deviation between injections (0.29%, n = 20), high analytical frequency (120 h−1), adequate recovery values (93-101%) for spiked samples, satisfactory accuracy (based on comparative determinations by high-performance liquid-chromatography), and a low detection limit (100 ng of BHA per g of biodiesel). Finally, our method can be adapted for the determination of other antioxidants in biodiesel samples. 相似文献
603.
Zuzanna A. Lewicka Angelo F. Benedetto Denise N. Benoit William W. Yu John D. Fortner Vicki L. Colvin 《Journal of nanoparticle research》2011,13(9):3607-3617
TiO2 and ZnO nanomaterials are widely used to block ultraviolet radiation in many skin care products, yet product labels do not
specify their dimensions, shape, or composition. The absence of this basic information creates a data gap for both researchers
and consumers alike. Here, we investigate the structural similarity of pigments derived from actual sunscreen products to
nanocrystals which have been the subject of intense scrutiny in the nanotoxicity literature. TiO2 and ZnO particles were isolated from eight out of nine commercial suncare products using three extraction methods. Their
dimension, shape, crystal phase, surface area, and elemental composition were examined using transmission and scanning electron
microscopy, X-ray diffraction, Brunauer–Emmett–Teller (BET) specific surface area analysis, energy dispersive X-ray and inductively
coupled plasma optical emission spectroscopy. TiO2 pigments were generally rutile nanocrystals (dimensions ~25 nm) with needle-like or near-spherical shapes. ZnO pigments were
wurtzite rods with a short axes less than 40 nm and longer dimensions often in excess of 100 nm. We identify two commercial
sources of TiO2 and ZnO nanocrystals whose physical and chemical features are similar to the pigments found in sunscreens. These particular
materials would be effective surrogates for the commercial product and could be used in studies of the health and environmental
impacts of engineered nanomaterials contained in sunscreens. 相似文献
604.
Edgar Vicente Torres Gonzlez Sergio Castro Hernndez Helen Denise Lugo Mndez Fernando Gabriel Arroyo Cabaas Javier Valencia Lpez Raúl Lugo Leyte 《Entropy (Basel, Switzerland)》2022,24(5)
Nowadays, in Mexico, most of the installed electricity generation capacity corresponds to combined cycles, representing 37.1%. For this reason, it is important to maintain these cycles in good operating conditions, with the least environmental impacts. An exergoeconomic and environmental analysis is realized to compare the operation of the combined cycle, with and without postcombustion, with the comparison of exergoeconomic and environmental indicators. With the productive structure of the energy system, the process of formation of the final products and the residues are identified, and an allocation criterion is also used to impute the formation cost of residue to the productive components related to its formation. This criterion considers the irreversibilities generated in each productive component that participates in the formation of a residue. The compositions of pollutant gases emitted are obtained, and their environmental impact is determined. The unit exergoeconomic cost of the power output in the gas turbine is lower in the combined cycle with postcombustion, indicating greater efficiency in the process of obtaining this energy stream, and the environmental indicators of global warming, smog formation and acid rain formation are higher in the combined cycle with postcombustion, these differences being 5.22%, 5.53% and 5.30%, respectively. 相似文献
605.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
606.
607.
Poly-(ϵ-caprolactone) is a biodegradable polymer, which can be used for both medical and environmental applications. Due to its multiple applications the synthesis of such a polymer has been attracting an increasing attention in the past few decades. In our work, the polymers were synthesised by bulk polymerisation, using different lanthanide halides as initiators. The lanthanide derivatives are known as very active catalysts in the ring-opening polymerisation of cyclic esters. Moreover, they are not toxic in comparison of catalysts, which are usually used for this synthesis. In this paper, the influence of the lanthanides on both the hydrolytic and enzymatic degradation of the PCL obtained by ring-opening polymerization of ϵ-caprolactone with different lanthanide-based catalysts such as: lanthane chloride (LaCl3), ytterbium chloride (YbCl3) and samarium chloride (SmCl3) was assessed. Samarium seems to slightly accelerate the hydrolytic degradation of the polymer and to slow down or inhibit its enzymatic degradation, mainly when the molecular weight of the polymer is high. The behaviour of PCL containing another lanthanide like lanthane is dependent on the nature of the metallic ion. Complete degradation, by the Lipase PS from Pseudomonas cepacia, is achieved only with Ytterbium. 相似文献
608.
609.
Franziska Hausig-Punke Gregor Dekevic Fabian H. Sobotta Jana I. Solomun Friederike Richter Denise Salzig Anja Traeger Johannes C. Brendel 《Macromolecular bioscience》2023,23(5):2370016
Cationic pH-responsive polymers promise to overcome critical challenges in cellular delivery. Ideally, the polymers become selectively charged along the endosomal pathway disturbing only the local membrane and avoiding unintended interactions or cytotoxic side effects at physiological conditions. Polypiperazines represent a novel, hydrophilic class of pH-responsive polymers whose response can be tuned within the relevant pH range (5–7.4). The authors discovered that the polypiperazines are effectively binding plasmid DNA (pDNA) and demonstrate high efficiency in transfection. By design of experiments (DoE), a wide parameter space (pDNA and polymer concentration) is screened to identify the range of effective concentrations for transfection. An isopropyl modified polypiperazine is highly efficient over a wide range of concentrations outperforming linear polyethylenimine (l-PEI, 25 kDa) in regions of low N*/P ratios. A quantitative polymerase chain reaction (qPCR) surprisingly revealed that the pDNA within the piperazine-based polyplexes can be amplified in contrast to polyplexes based on l-PEI. The pDNA must therefore be more accessible and bound differently than for other known transfection polymers. Considering the various opportunities to further optimize their structure, polypiperazines represent a promising platform for designing effective soluble polymeric vectors, which are charge-neutral at physiological conditions. 相似文献