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21.
William J.?KraemerEmail author Jeff S.?Volek Barry A.?Spiering Jakob L.?Vingren 《Monatshefte für Chemie / Chemical Monthly》2005,136(8):1383-1390
Summary. Early research investigating the effects of L-carnitine supplementation has examined its role in substrate metabolism and in acute exercise performance. These studies have yielded equivocal findings, partially due to difficulties in increasing muscle carnitine concentrations. However, recent studies have proposed that L-carnitine may play a different role in exercise physiology, and preliminary results have been encouraging. Current investigations have theorized that L-carnitine supplementation facilitates exercise recovery. Proposed mechanism is as follows: 1) increased serum carnitine concentration enhances capillary endothelial function; 2) increased blood flow and reduced hypoxia mitigate the cascade of ensuing, destructive chemical events following exercise; 3) thus allowing reduced structural damage of skeletal muscle mediated by more intact receptors in muscle needed for improved protein signaling. This paradigm explains decreased markers of purine catabolism, free radical formation, and muscle tissue disruption after resistance exercise and the increased repair of muscle proteins following long-term L-carnitine supplementation. 相似文献
22.
De La Rosa Luis B. Reshamwala Sultan Latimer Vivian M. Shawky Bahaa T. Dale Bruce E. Stuart Earnest D. 《Applied biochemistry and biotechnology》1994,(1):483-497
The herbaceous crops that may provide fermentable carbohydrates for production of fuels and chemicals also contain 10–20%
protein. Protein coproduction with biomass-derived fuels and chemicals has important advantages: (1) food and fuel production
can be integrated, and (2) protein is a high-value product that may significantly improve overall process economics. We report
the results of an integrated approach to producing protein and fermentable sugars from one herbaceous species, Coastal Bermudagrass
(CBG). The ammonia fiber explosion (AFEX) process makes possible over 90% conversion of cellulose and hemicellulose to simple
sugars (about 650 mg reducing sugars/g dry CBG) at 5 IU cellulase/g vs < 20% conversion for untreated CBG. The AFEX treatment
also improves protein extraction from CBG; over 80% protein recovery is possible from AFEX-treated CBG vs about 30% recovery
from untreated CBG. 相似文献
23.
Chatterjee J 《Advances in colloid and interface science》2002,99(2):163-179
Removal of oil drops from solid surfaces immersed in an aqueous medium is of interest in many applications. It has been shown that drop shape analysis can be used to predict conditions at which the stability limit of a lighter than water oil drop on a solid surface immersed in an aqueous bath is reached (Adv. Colloid Interface Sci. 98 (2002) 265). However the above analysis is restricted to cases where the contact angle made by the drop is below 90degrees and when the surface conditions result in a 'pinned' contact line. In this paper, it is shown that drop shape analysis can be used to predict the critical conditions at which drop stability limit is reached for drop contact angles of 90degrees and above, which is encountered with 'hydrophilic' surfaces. This critical condition can predict the occurrence of partial oil drop detachment, before complete removal due to 'roll-up', which occurs when the hydrophilic surface is adequately smooth which prevents 'pinning' of the contact line. The critical conditions at which partial drop detachment occurs can also be approximately predicted from simple force balances. It has been shown (Adv. Colloid Interface Sci. 98 (2002) 265) that for contact angles less than 90degrees, the critical limit based on shape analysis appears to resolve the differences that arise due to alternate expressions for capillary retention force. This paper shows that even for contact angles above 90degrees, the critical conditions predicted from the shape analysis resolves the differences in the predictions from the alternate force balances. Drop shape analysis used in this paper is based on the 'Arc-length' form of Young-Laplace or 'drop shape' equation, which is different from the 'Y vs X' form of the above equation that is used in Adv. Colloid Interface Sci. 98 (2002) 265. The above drop shape equation is solved by a fourth order Runge-Kutta technique and it is shown that for angles less than 90degrees, the two forms of the drop shape equation, predict almost identical values of the critical Eotvos number. This paper highlights the competing effects of interfacial tension lowering induced drop instability and 'roll-up', a term that is used to describe the retraction of the contact line of an oil drop on a surface, in being the primary c ause for drop detachment. 相似文献
24.
Soon Fatt Yoon 《Journal of Electronic Testing》1995,6(1):117-125
Conventionally, lifetests of semiconductor laser diodes usually involved operating the devices continuously at either constant power output or drive current, with periodic recording of their characteristics. In this paper, some effects arising from interrupted lifetest of 1.3 m GaInAsP-InP inverted-rib laser diodes are reported. This unconventional lifetest method involves constant power biasing at 4 mW/facet and 8 mW/facet respectively at 50°C, followed by a period during which the lifetest is interrupted and the devices left unbiased at room temperature. Subsequently, the devices were put back on constant power biasing at 50°C. Among a number of parameters, pronounced reduction in the threshold current, current for 4 mW/facet and 8 mW/facet were observed, indicating strong recovery effects commencing from the time when the life-test was interrupted. Redistribution of mobile defects in the cladding layer is postulated to be the cause of the degradation recovery, and the data supports the occurrence of an aging-current dependent defect annihilation mechanism. Such recovery effects have so far been observed to occur only in the GaInAsP-InP inverted-rib devices. 相似文献
25.
为了节省基站天线所占空间资源,降低其运营成本,现代移动通信需要将多个天线阵列紧密地排列在一起,构成多频共口径基站天线。多天线的紧密排列势必造成天线间强烈的耦合,不仅使得天线阻抗失配、隔离度变差,同时也造成辐射方向图的严重变形。因此,近年来多频共口径基站天线的去耦成为工业界和学术界研究的热点,早期的去耦技术主要是面向改善天线的阻抗匹配和隔离度,而对面向方向图保形的去耦技术研究相对较少。文章在简要介绍面向方向图保形的基站天线去耦技术的研究现状的基础上,重点阐述了褚庆昕教授天线射频团队基于感应电流抵消、耦合场抵消和辐射阻断等原理,提出的几种新型的去耦技术。这些技术不仅可以有效地改善基站天线的阻抗匹配和隔离,更重要的是很好地实现了天线方向图保形。仿真和测试结果验证了原理的正确性和设计的可行性。一些技术已被用于5G基站天线产品。 相似文献
26.
27.
Yong Zhu Jin-lian Hu Kwok-wing Yeung Hao-jun Fan Ye-qiu 《高分子科学》2006,(2):173-186
SMPU (shape memory polyurethane) non-ionomers and ionomers, synthesized with poly(c-caprolactone) (PCL), 4, 4'-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO), dimethylolpropionic acid (DMPA) were measured with cyclic tensile test and strain recovery test. The relations between the structure and shape memory effect of these two series were studied with respect to the ionic group content and the effect of neutralization. The resulting data indicate that, with the introduction of asymmetrical extender, the stress at 100% elongation is decreased for PU non-ionomer and ionomer series, especially lowered sharply for non-ionomer series; the fixation ratio of ionomer series is not affected obviously by the ionic group content; the total recovery ratio of ionomer series is decreased greatly. After sufficient relaxation time for samples stretched beforehand, the switching temperature is raised slightly, whereas the recovery ratio measured with strain recovery test method is lowered with increased DMPA content. The characterization with FT-IR, DSC, DMA elucidated that, the ordered hard domain of the two series is disrupted with the introduction of DMPA which causes more hard segments to dissolve in soft phase; ionic groups on hard segment enhance the cohesion between hard segments especially at high ionic group content and significantly facilitate the phase separation compared with the corresponding non-ionomer at moderate ionic group content. 相似文献
28.
We report a nanoscale lipid membrane-based sensor of conjugated polydiacetylene (PDA) vesicles for fluorescence detection of organic amines. The vesicle sensor was constructed by incorporation of a BODIPY fluorescent dye into the PDA vesicles. The fluorescent properties of the resulting vesicles can be manipulated by adjusting lipid components, and are controlled by environmental and solution conditions. The fluorescence of the BODIPY dye was significantly quenched in the polymerization of diacetylene lipid vesicles by a UV irradiation process. However, it was sufficiently recovered by external stimuli such as a hike of solution pH. The fluorescence recovery process was reversible, and a decrease in solution pH resulted in repeated quenching. The reported system transforms an external stimulus into a large fluorescence intensity change, demonstrating great potential in developing new signal reporting method for biosensor design. The quench-recovery phenomenon of the BODIPY-PDA is believed to be related to the energy transfer between the dye and the PDA conjugate backbone. The vesicle sensor was applied for detecting an organic amine, triethylamine (TEA) and a large linear relationship was obtained between the increase in fluorescence intensity and the concentrations of TEA. The detection limit of TEA by vesicle sensors using fluorescence recovery was found to be 10 μM. 相似文献
29.
Three non-specific methods for the extraction of total petroleum hydrocarbons (TPH) from soil into organic solvent were compared.
The techniques used for sample preparation were Soxhlet extraction, closed-vessel microwave-assisted extraction, and CEN shake
extraction. The total concentrations of extracted compounds in the boiling point range of C10–C40 were determined by gas chromatography
with flame ionization detection. The best recovery (99%) and repeatability (±3%) from standard oil mixtures were obtained
with microwave-assisted extraction. However, the different extraction methods exhibited different behaviour when spiked soil
samples were extracted. The best repeatability was obtained with CEN shake extraction (±6%) but the repeatability values for
Soxhlet and microwave-assisted methods were quite high (>20%). However, the larger uncertainties of the latter extraction
methods does not necessarily limit the applicability of these methods to the determination of petroleum hydrocarbons in soil,
as in the assessment of soil contamination the expanded uncertainty of the result is usually not limited by analytical uncertainty,
but rather by the uncertainty of the primary sampling stage. However, distinctive variation found in the chromatographic profiles
illustrates that discretion should be obeyed when chromatograms obtained after application of different extraction methods
on petroleum contaminated samples are to be used in the fingerprinting or age dating studies. Otherwise, misleading conclusions
concerning the age of spillage could be drawn. 相似文献
30.
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