全文获取类型
收费全文 | 207788篇 |
免费 | 7020篇 |
国内免费 | 4151篇 |
专业分类
化学 | 113654篇 |
晶体学 | 3376篇 |
力学 | 9330篇 |
综合类 | 244篇 |
数学 | 23763篇 |
物理学 | 68592篇 |
出版年
2022年 | 2102篇 |
2021年 | 2605篇 |
2020年 | 2825篇 |
2019年 | 2875篇 |
2018年 | 3119篇 |
2017年 | 3129篇 |
2016年 | 4773篇 |
2015年 | 3513篇 |
2014年 | 5088篇 |
2013年 | 10193篇 |
2012年 | 8945篇 |
2011年 | 10025篇 |
2010年 | 7165篇 |
2009年 | 7009篇 |
2008年 | 8688篇 |
2007年 | 8336篇 |
2006年 | 7868篇 |
2005年 | 7014篇 |
2004年 | 6367篇 |
2003年 | 5546篇 |
2002年 | 5324篇 |
2001年 | 5907篇 |
2000年 | 4527篇 |
1999年 | 3771篇 |
1998年 | 3159篇 |
1997年 | 3003篇 |
1996年 | 2928篇 |
1995年 | 2707篇 |
1994年 | 2633篇 |
1993年 | 2467篇 |
1992年 | 2748篇 |
1991年 | 2600篇 |
1990年 | 2510篇 |
1989年 | 2356篇 |
1988年 | 2333篇 |
1987年 | 2318篇 |
1986年 | 2155篇 |
1985年 | 2783篇 |
1984年 | 2814篇 |
1983年 | 2495篇 |
1982年 | 2565篇 |
1981年 | 2365篇 |
1980年 | 2331篇 |
1979年 | 2458篇 |
1978年 | 2487篇 |
1977年 | 2408篇 |
1976年 | 2461篇 |
1975年 | 2391篇 |
1974年 | 2350篇 |
1973年 | 2521篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
For two types of qutrits specified by the dynamical symmetry SU(3) and SU(2), we consider the difference in entanglement caused by the lack of quantum observables in the latter case. In particular, we show that the SU(2) qutrits can have specific separable entanglement caused by quantum correlations of intrinsic degrees of freedom in a single party without interparty correlations. 相似文献
102.
A novel copolymer, poly(N‐hexyl‐3,7‐phenothiazylene‐1,2‐ethenylene‐2,6‐pyridylene‐1,2‐ethenylene) ( P3 ), containing N‐hexyl‐3,7‐phenothiazylene and 2,6‐pyridylene chromophores was synthesized to investigate the effect of protonation, metal complexation, and chemical oxidation on its absorption and photoluminescence (PL). Poly(N‐hexyl‐3,8‐iminodibenzyl‐1,2‐ethenylene‐1,3‐phenylene‐1,2‐ethenylene) and poly(N‐hexyl‐3,7‐phenothiazylene‐1,2‐ethenylene‐1,3‐phenylene‐1,2‐ethenylene) ( P2 ), consisting of 1,3‐divinylbenzene alternated with N‐hexyl‐3,8‐iminodibenzyl and N‐hexyl‐3,7‐phenothiazylene, respectively, were also prepared for comparison. Electrochemical investigations revealed that P3 exhibited lower band gaps (2.34 eV) due to alternating donor and acceptor conjugated units (push–pull structure). The absorption and PL spectral variations of P3 were easily manipulated by protonation, metal chelation, and chemical oxidation. P3 displayed significant bathochromic shifts when protonated with trifluoroacetic acid in chloroform. The complexation of P3 with Fe3+ led to a significant absorption change and fluorescence quenching, and this implied the coordination of ferric ions with the 2,6‐pyridylene groups in the backbone. Moreover, both phenothiazylene‐containing P2 and P3 showed conspicuous PL quenching with a slight redshift when oxidized with NOBF4. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1272–1284, 2004 相似文献
103.
Nowadays much attention is being paid to the determination of trace amounts of noble metals in geological, industrial, biological and environmental samples. The most promising techniques, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (ETAAS) are characterized by high sensitivity. However, the accurate determination of trace noble metals has been limited by numerous interferences generated from the presence of matrix elements. To decrease, or eliminate, these interferences, the sorption preconcentration of noble metals is often used prior to their instrumental detection. A great number of hyphenated methods of noble metal determination using sorption preconcentration have been developed. This review describes the basic types of available sorbents, preconcentration procedures and preparations of the sorbent to the subsequent determination of noble metals. The specific features of instrumental techniques and examples of ETAAS, FAAS, ICP-AES, ICP-MS determinations after the sorption preconcentration of noble metals are considered. The references cited here were selected mostly from the period 1996 - 2006. 相似文献
104.
The adsorption of nonionic surfactant Triton X-100 on quartz sand and methylated quartz sand from water and toluene was investigated by means of spectrophotometry, the radiotracer technique, and wetting angle measurements. 相似文献
105.
For the NO molecule, modelled as a Morse oscillator, time-dependent (TD) nuclear Schr?dinger equation has been numerically
solved for the multiphoton vibrational dynamics of the molecule under a far-infrared laser of wavelength 10503 nm, and four
different intensities,I = 1 × 108, 1 × 1013, 5 × 1016, and 5 × 1018 W cm−2 respectively. Starting from the vibrational ground state at zero time, various TD quantities such as the norm, dissociation
probability, potential energy curve and dipole moment are examined. Rich high-harmonics generation (HHG) spectra and above-threshold
dissociation (ATD) spectra, due to the multiphoton interaction of vibrational motions with the laser field, and consequent
elevation to the vibrational continuum, have been obtained and analysed.
Dedicated to Professor C N R Rao on his 70th birthday
An erratum to this article is available at . 相似文献
106.
Crosslinking behaviors of acrylonitrile butadiene rubber (NBR)/poly (vinyl chloride) (PVC) alloy, filled with anhydrous copper sulfate (CuSO4) particles, were investigated for the first time by dynamic mechanical analysis (DMA) under hetero and isothermal modes, respectively. In the heterothermal testing, (NBR/PVC)/CuSO4 compound showed two marked increases in the storage modulus (E′), corresponding to coordination crosslinking of NBR-CuSO4 and self-crosslinking of NBR and PVC respectively. During the isothermal testing, a dramatic increase in E′ was found at the initial stage while that of original NBR/PVC alloy was not detected. The marked increase in E′ of (NBR/PVC)/CuSO4 compound was mainly due to the crosslinking induced by coordination between CN and Cu2+. The increasing extent of E′ increased with the rise of CuSO4 content, suggesting the formation of a greater number of crosslinks. Moreover, the activation energy (Ea) of crosslinking process was about 139 kJ/mol. In this work, fourier transform infrared spectrum (FT-IR) and equilibrium swelling method were also performed for the characterization of the compound. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 41–51, 2007 相似文献
107.
108.
M. S. Kalinin M. B. Krainev 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(7):984-987
The behavior of the intensity of anomalous and galactic cosmic rays in the outer heliosphere is compared. The previous hypothesis, according to which the lowest energy galactic cosmic rays affected by large-scale electric fields far beyond the termination shock wave of the solar wind may contribute to the behavior of the anomalous component intensity, is analyzed. 相似文献
109.
110.