全文获取类型
收费全文 | 8556篇 |
免费 | 1262篇 |
国内免费 | 722篇 |
专业分类
化学 | 2348篇 |
晶体学 | 84篇 |
力学 | 1599篇 |
综合类 | 109篇 |
数学 | 2696篇 |
物理学 | 3704篇 |
出版年
2024年 | 24篇 |
2023年 | 106篇 |
2022年 | 280篇 |
2021年 | 279篇 |
2020年 | 313篇 |
2019年 | 262篇 |
2018年 | 277篇 |
2017年 | 320篇 |
2016年 | 389篇 |
2015年 | 263篇 |
2014年 | 457篇 |
2013年 | 717篇 |
2012年 | 433篇 |
2011年 | 475篇 |
2010年 | 438篇 |
2009年 | 478篇 |
2008年 | 476篇 |
2007年 | 476篇 |
2006年 | 436篇 |
2005年 | 423篇 |
2004年 | 371篇 |
2003年 | 370篇 |
2002年 | 312篇 |
2001年 | 250篇 |
2000年 | 263篇 |
1999年 | 233篇 |
1998年 | 215篇 |
1997年 | 181篇 |
1996年 | 175篇 |
1995年 | 140篇 |
1994年 | 118篇 |
1993年 | 93篇 |
1992年 | 88篇 |
1991年 | 55篇 |
1990年 | 57篇 |
1989年 | 53篇 |
1988年 | 41篇 |
1987年 | 24篇 |
1986年 | 23篇 |
1985年 | 24篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 26篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1976年 | 5篇 |
1971年 | 7篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Ferhat Sametoglu 《Optical Review》2006,13(5):326-337
Traceability in illuminance measurements at the National Metrology Institute of Turkey (TüBITAK-UME) was established in 2003
with a detector-based realization. The new measurement technique was developed for the determination of illuminance responsivity
and upgrating of the illuminance scale. The unit of the illuminance responsivity, in A/lx, was measured with an expanded uncertainty
of 0.2% (k = 2) by supplying using the developed scanning technique for the calculation of color correction factor. The surface of a
radiometer was scanned using a double-monochromator facility upgraded with an x-y scanning system. The illuminance responsivity
as a function of bandpass and temperature were also investigated in this study.
To use a radiometer in the photometric applications of metrology, a light-sensitive device, a so-called trap detector, was
characterized by measuring the absolute responsivity, the non-linearity, and spatial non-uniformity. 相似文献
42.
对Hajek-Renyi不等式进行了推广,利用推广的不等式给出了随机变量序列绝对平均意义下的强大数定律的一个条件. 相似文献
43.
44.
R. Jayakumar Y.‐S. Lee S. Nanjundan 《Journal of polymer science. Part A, Polymer chemistry》2003,41(18):2865-2878
The calcium salt of mono(hydroxyethoxyethyl)phthalate [Ca(HEEP)2] was synthesized by the reaction of diethylene glycol, phthalic anhydride, and calcium acetate. Calcium‐containing poly(urethane ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI) with a mixture of Ca(HEEP)2 and poly(ethylene glycol) (PEG300 or PEG400) with di‐n‐butyltin dilaurate as a catalyst. A series of calcium‐containing PUEs of different compositions were synthesized with Ca(HEEP)2/PEG300 (or PEG400)/diisocyanate (HMDI or TDI) molar ratios of 2:2:4, 3:1:4, and 1:3:4 so that the coating properties of the PUEs could be studied. Blank PUEs without calcium‐containing ionic diols were also prepared by the reaction of PEG300 or PEG400 with HMDI or TDI. The PUEs were well characterized by Fourier transform infrared, 1H and 13C NMR, solid‐state cross‐polarity/magic‐angle‐spinning 13C NMR, viscosity, solubility, and X‐ray diffraction studies. The thermal properties of the polymers were also studied with thermogravimetric analysis and differential scanning calorimetry. The PUEs were applied as top coats on acrylic‐coated leather, and their physicomechanical properties were also studied. The coating properties of PUEs, such as the tensile strength, elongation at break, tear strength, water vapor permeability, flexing endurance, cold crack resistance, abrasion resistance, color fastness, and adhesive strength, were better than the standard values. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2865–2878, 2003 相似文献
45.
Dmitry Dolgopyat 《Transactions of the American Mathematical Society》2004,356(4):1637-1689
We consider a large class of partially hyperbolic systems containing, among others, affine maps, frame flows on negatively curved manifolds, and mostly contracting diffeomorphisms. If the rate of mixing is sufficiently high, the system satisfies many classical limit theorems of probability theory.
46.
E.V. Jansson 《Applied Acoustics》2004,65(12):1197-1205
Good violins have a broad hill in the 2-3 kHz range of their frequency response. This hill has previously been attributed to the first in-plane resonance of the violin bridge. Experiments prove, however, that the hill is the result of two forces acting in opposite directions at the bridge feet. The experiments reported here show that the hill can be “tuned” by altering the distance between the bridge feet. It can be tuned both in terms of frequency and level but the properties of the violin cannot be neglected. 相似文献
47.
A simple and accurate algorithm (phase scanning method) is proposed for 3D surface contouring and dynamic response determination of a vibrating object. A sinusoidal fringe pattern is projected onto a low-frequency vibrating object by a programmable liquid crystal display projector. The fringe patterns are captured by a high-speed CCD camera with a telecentric gauging lens. Phase values are evaluated point by point using phase scanning method. From the phase values of each point on the object, the contour of the specimen at different instants of vibration can be retrieved. In this paper, a small vibrating coin is used to demonstrate the validity of the method and the experimental results are compared with test results on a stationary coin using four-step phase shifting and fast Fourier transform methods. The technique is especially useful in applications where the vibrating object has a complicated shape. 相似文献
48.
Letters in Mathematical Physics - 相似文献
49.
50.
选用新方法合成了2-碘—N-甲基苯磺酰胺,通过^1H NMR,^13C NMR,^13C DEPT NMR(Distortionless Enhancement by Polarization Transfer NMR)和MS确证的其结构。 相似文献