全文获取类型
收费全文 | 68篇 |
免费 | 33篇 |
国内免费 | 9篇 |
专业分类
化学 | 50篇 |
综合类 | 1篇 |
数学 | 42篇 |
物理学 | 17篇 |
出版年
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有110条查询结果,搜索用时 203 毫秒
71.
为了实现采摘机器人在复杂的自然场景下正确识别树上果实,来完成果实采摘,研究了不同环境下柑橘的识别方法.针对复杂的自然环境的影响及传统方法的局限性,在可见光和近红外区域择选5个特征波长滤波片,采集得到5幅滤波后的图像,并利用光谱角分类算法完成柑橘识别.试验结果表明,在光照角度、光照强度等不同条件下,柑橘的识别准确度达到96%.研究表明,滤波片光谱图像技术结合光谱角分类算法可以有效地识别自然场景下的成熟柑橘. 相似文献
72.
Marek Dziadosz Jens-Peter Weller Michael Klintschar Jörg Teske 《Analytical and bioanalytical chemistry》2013,405(20):6595-6597
To avoid the detection of small fragmentation products of γ-hydroxybutyrate (GHB), a liquid chromatography–tandem mass spectrometry GHB quantification method in human serum supported by adduct formation was developed and validated. The continuous infusion of GHB/GHB-D6 made the identification of two adducts possible and GHB/GHB-D6 sodium acetate adduct fragmentation was used as target mass transition. A Luna 5 μm C18 (2) 100 A, 150 mm?×?2 mm analytical column and elution with a programmed flow of the mobile phase consisting of 10 % A (H2O/methanol = 95/5, v/v) and 90 % B (H2O/methanol = 3/97, v/v), both with 10 mM ammonium acetate and 0.1 % acetic acid (pH?=?3.2), were used. Protein precipitation with 1 mL of the mobile phase B was used as the sample preparation. The calculated limit of detection/quantification was 1 μg/mL. The presented study shows that the fragmentation of GHB sodium acetate adducts is an effective way of quantification of this small molecule and is an interesting alternative to other methods based on the detection of ions smaller than 85 Da. This fact together with the short analysis time of 3 min and the fast sample preparation make this method very attractive for forensic/clinical application. 相似文献
73.
The objective of this study was to determine if topical anesthesia to the larynx and pharynx affects vocal fold motion during dynamic voice evaluation with transnasal flexible endoscopy. Transnasal dynamic laryngeal examinations of 10 patients with no voice complaints were evaluated by five blinded fellowship-trained laryngologists. Each patient was examined before and after application of topical anesthetic. Reviewers rated briskness of right and left vocal fold movement and longitudinal tension on a visual analogue scale. Statistical comparisons were made between individual subject scores before and after anesthetic application. Inter-rater reliability was also assessed. No statistical difference was observed between subject scores before and after anesthetic application. Average intraclass correlation coefficients were 0.643 and 0.591 for pre- and postanesthesia scores, respectively. Application of topical anesthesia to the larynx and pharynx does not affect vocal fold motion. 相似文献
74.
J. Herion K. Szot S. Barzen F. Siebke M. Teske 《Analytical and bioanalytical chemistry》1997,358(1-2):338-340
As-grown films of hydrogenated amorphous silicon (a-Si?:?H, highly phosphorous-doped) were investigated by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Hills up to 10 nm in height and 10 to 20 nm in diameter have been observed by AFM. By using STM in a new high-sensitivity mode, (1) atomically smooth areas (roughness about 0.3 Å rms) which occur at the top of the hills, (2) subnanometer structures several Å in height which cover large parts of the surface have been identified. Simultaneous measurements of the local apparent barrier heights (LABH) show a clear correlation to the topography. Areas showing subnanometer structures have always low LABHs while the highest values of the LABH occur on the smooth areas. 相似文献
75.
76.
MJ Lazaro AA Herod M Domin Y Zhuo CA Islas R Kandiyoti 《Rapid communications in mass spectrometry : RCM》1999,13(14):1401-1412
Three methods for determining a 'safe' estimate for high-mass limits of MALDI spectra of coal derived liquids were explored, using a sample of coal-tar pitch and its pyridine-insoluble fraction. Co-addition of increasing numbers of single-shot spectra (10, 30, 50 and 100 pulses) showed visually observable reductions in noise levels, consistent with robust and statistically meaningful signals. Three separate types of post-acquisition calculation were used to identify high-mass limits of the spectra. (i) A literature method indicated high-mass limits similar to those observed visually-as a shift from baseline at the highest masses, nearly 350 000 u for the coal tar pitch and about 390 000 u for its pyridine insoluble fraction. (ii) Comparing instrument signal with pre-selected multiples of the standard deviation, upper mass estimates of between 40-60 000 u for the coal-tar pitch and about 95 000 u for its pyridine-insoluble fraction were found. (iii) Calculation of the slope was used to identify 'lift-off' of the spectrum from baseline. The angle between the smoothed spectrum and the baseline was matched to a pre-selected value (e.g. 0.5 degrees and 1 degrees ). However, the arbitrary specification of the key parameter did not establish this last method on a firm basis. The choice of a criterion for estimating high-mass limits of MALDI spectra remains a semi-quantitative procedure; a reasonably conservative high-mass limit may be estimated by comparison of signal with five times the standard deviation. However, evaluation of size exclusion chromatograms of the present samples using polystyrene standards suggests that molecular mass distributions of pitch samples arrived at by MALDI mass spectrometry are, at least partly, determined by the limitations of available instruments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
77.
Christoph Ludwig Teske Huayna Terraschke Sebastian Mangelsen Wolfgang Bensch 《无机化学与普通化学杂志》2020,646(21):1716-1721
New investigations combining single crystal- and synchrotron-based powder X-ray diffraction data revealed that Ba[Au2SnS4] crystallizes in the orthorhombic crystal system in space group C2221 instead of P21212 as reported earlier. While the principle crystal structure is not altered, there are significant differences of the interatomic distances Au-S and Sn-S. A salient property of this crystal structure is the partial framework composed of AuS2 dumbbells and SnS4 tetrahedra to form chains [(Au2SnS4)2–]∞ propagating in the [100] direction. Within the chains a short Au ··· Au separation of 2.9538(13) Å is observed, while the interchain Au ··· Au separation is longer at 3.383 Å. The Ba2+ cation is eightfold coordinated by S2– anions in a distorted bicapped trigonal prismatic environment BaS8. These polyhedra share all S2– anions thus generating a three-dimensional network. This connection Scheme generates voids along [100] hosting [(Au2SnS4)2–]∞ chains. In addition, the compound has been shown to be luminescent at the blue-green spectral range with emission maximum at approximately 21000 cm–1. 相似文献
78.
79.
80.