全文获取类型
收费全文 | 1065篇 |
免费 | 38篇 |
国内免费 | 5篇 |
专业分类
化学 | 881篇 |
晶体学 | 8篇 |
力学 | 19篇 |
数学 | 63篇 |
物理学 | 137篇 |
出版年
2023年 | 8篇 |
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 17篇 |
2019年 | 21篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 27篇 |
2015年 | 24篇 |
2014年 | 30篇 |
2013年 | 55篇 |
2012年 | 68篇 |
2011年 | 84篇 |
2010年 | 36篇 |
2009年 | 33篇 |
2008年 | 70篇 |
2007年 | 88篇 |
2006年 | 79篇 |
2005年 | 69篇 |
2004年 | 59篇 |
2003年 | 53篇 |
2002年 | 50篇 |
2001年 | 19篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1956年 | 1篇 |
排序方式: 共有1108条查询结果,搜索用时 171 毫秒
81.
82.
Abstract Accuracy of hydrostatic pressure measurement in a diamond-anvil cell (DAC) depends on the reproducibility of ruby RI fluorescent measurement. The larger scatter in R, fluorescent wavelength shift than the reproducibility of spectroscopic measurement was observed among appropriately mirror-finished ruby plates before setting up in DAC. The characteristics of the scatter changed after loading DAC up to pressure over hydrostatic limit. They vanished by annealing the ruby plates. These phenomena are presumably due to the appearance and disappearance of the residual stress in the ruby crystal. Such hysteresis of ruby fluorescent wavelength shift by pressure and its annealing effect are discussed. 相似文献
83.
Xianqing Piao Xianmin Zhang Yuichi Mori Masayuki Koishi Akinari Nakaya Shinichiro Inoue Isao Aoki Akira Otomo Shiyoshi Yokoyama 《Journal of polymer science. Part A, Polymer chemistry》2011,49(1):47-54
Electro‐optic side‐chain polymers have been synthesized by the post‐functionalization of methacrylate isocyanate polymers with novel phenyl vinylene thiophene vinylene bridge (FTC) nonlinear optical chromophores. For this application, FTC‐based chromophores were modified in their electronic donor structure, exhibiting much larger molecular hyperpolarizabilities compared with the benchmark FTC. Of these new chromophores, absorption spectra, hyper‐Rayleigh scattering experiment, and thermal analysis were carried out to confirm availability as effective nonlinear optical units for electro‐optic side‐chain polymers. The electro‐optic coefficients (r33) of obtained polymers were investigated in the process of in situ poling by monitoring the temperature, current flow, poling field, and electro‐optic signal. Compared with the nonsubstituted analogue, benxyloxy modified FTC chromophore significantly achieved higher nonlinear optical property, exhibiting molecular hyperpolarizability at 1.9 μm of 4600 × 10?30 esu and an r33 value of 150 pm/V at the wavelength of 1.31 μm. Synthesized electro‐optic polymers showed high glass transition temperature (Tg), so that the temporal stability examination exhibited >78% of the electro‐optic intensity remaining at 85 °C over 500 h. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
84.
85.
Kuga Yoshikazu Okauchi Keiko Takeda Daiki Ohira Yuichi Ando Koji 《Journal of nanoparticle research》2001,3(2-3):175-183
Size distribution measurements and classification tests by a low pressure differential mobility analyzer (LPDMA) for nanometer-sized silver particles and cesium iodide particles under low pressure conditions (123–300 Torr) were performed using a transmission electron microscope (TEM) and the tandem DMA technique. When the ratio of the sheath gas flow rate and the aerosol gas flow rate was set at 5 : 1, the targeted sizes calculated from the classification voltage applied to the LPDMA at 160 Torr are found to be in good correlation with the count mean Feret diameter obtained from the TEM observation of the particles collected after a classification ranging from 6 to 25 nm, although the targeted sizes set by the LPDMA were approximately 15% greater than the count mean Feret diameter measured by the TEM after classification. The geometric standard deviations of DMA-classified particles measured by TEM and those obtained from the tandem DMA method ranged from 1.08 to 1.17 and from 1.05 to 1.13, respectively. They were slightly greater than the ideal geometric standard deviations (1.05) of the particles classified with the LPDMA, which was calculated by neglecting the broadening effects due to Brownian diffusion. We experimentally demonstrated the validity of our LPDMA system for size measurements and classification of the nanometer-sized particles under low pressure conditions. 相似文献
86.
For the evaluation of two-dimensional carrier profiles in semiconductor devices, we have developed a novel form of probe–sensor combined unit that uses an etched tungsten wire as a conductive probe, and commercially available quartz tuning fork as the force sensor. This unit has a self-sensing capability due to the piezoelectric effect of quartz tuning fork, thus obviating optical setup, and its conductivity is higher and more stable than that of conventional metal-coated Si cantilever. In addition, this probe–sensor combined unit is inexpensive and easy to use, when compared to the well-known optical methods of Si-based cantilever vibration detection system. Our scanning probe microscope using this probe–sensor combined unit is able to mapping the capacitive gradient signal (dC/dZ image) and internal damping of quartz tuning fork oscillation (dissipation image) while scanning the sample surface. In this letter, we show the results of visualization of the p–n junction locus of a Si metal–oxide–semiconductor field effect transistor in both dC/dZ and dissipation images. 相似文献
87.
Paul Sheridan Yuichi Yagahara Hidetoshi Shimodaira 《Annals of the Institute of Statistical Mathematics》2008,60(4):747-761
We propose a scale-free network model with a tunable power-law exponent. The Poisson growth model, as we call it, is an offshoot
of the celebrated model of Barabási and Albert where a network is generated iteratively from a small seed network; at each
step a node is added together with a number of incident edges preferentially attached to nodes already in the network. A key
feature of our model is that the number of edges added at each step is a random variable with Poisson distribution, and, unlike
the Barabási–Albert model where this quantity is fixed, it can generate any network. Our model is motivated by an application
in Bayesian inference implemented as Markov chain Monte Carlo to estimate a network; for this purpose, we also give a formula
for the probability of a network under our model. 相似文献
88.
Koji Nagahama Kanae Fujiura Shunsuke Enami Tatsuro Ouchi Yuichi Ohya 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6317-6332
Starburst triblock copolymers consisting of 8‐arm poly(ethylene glycol) (8‐arm PEG) and biodegradable poly(L ‐lactide) (PLLA) or its enantiomer poly(D ‐lactide) (PDLA), 8‐arm PEG‐b‐PLLA‐b‐PEG ( Stri‐L ), and 8‐arm PEG‐b‐PDLA‐b‐PEG ( Stri‐D ) were synthesized. An aqueous solution of a 1:1 mixture ( Stri‐Mix ) of Stri‐L and Stri‐D assumed a sol state at room temperature, but instantaneously formed a physically crosslinked hydrogel in response to increasing temperature. The resulting hydrogel exhibited a high‐storage modulus (9.8 kPa) at 37 °C. Interestingly, once formed at the transition temperature, the hydrogel was stable even after cooling below the transition temperature. The hydrogel formation process was irreversible because of the formation of stable stereocomplexes. In aqueous solution, gradual hydrolytic erosion was observed because of degradation of the hydrogel. The combination of rapid temperature‐triggered irreversible hydrogel formation, high‐mechanical strength, and degradation behavior render this polymer mixture system suitable for use in injectable biomedical materials, for example, as a drug delivery system for bioactive reagents or a biodegradable scaffold for tissue engineering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6317–6332, 2008 相似文献
89.
Yuichi Yamamura Krzysztof Matyjaszewski 《Journal of polymer science. Part A, Polymer chemistry》2008,46(6):2015-2024
Tripodal imidazole containing ligands, bis((2‐pyridyl)methyl)(1‐methylimidazole‐2‐yl)methyl)amine (BPIA) and bis(1‐methylimidazole‐2‐yl)methyl)((2‐pyridyl)methyl)amine (BIPA), were synthesized and used for copper catalyzed atom transfer radical polymerization (ATRP) of n‐butyl acrylate (nBA). The molecular weights of poly(n‐butyl acrylate) (PnBA) catalyzed by CuBr/BPIA and CuBr/BIPA complexes increased linearly with nBA conversions and they were close to theoretical values with low polydispersities. ATRP equilibrium rate constant (KATRP) measurements showed that bothCuBr/BPIA and CuBr/BIPA complexes had high KATRP values, similar to that of CuBr/tri(2‐pyridylmethyl)amine (TPMA), which is one of the ATRP most active ligands. Activators regenerated by electron transfer (ARGET) ATRP of nBA with CuBr2/BPIA and CuBr2/BIPA complexes were also conducted and polymerization reached high nBA conversions, resulting in PnBA with low polydispersities. This suggests that the copper complexes with BPIA and BIPA were sufficiently stable and active to conduct ATRP when catalyst concentration was low. ARGET ATRP to form high molecular weight PnBA with CuBr2/BPIA and CuBr2/BIPA complexes was also successful. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2015–2024, 2008 相似文献
90.