全文获取类型
收费全文 | 1459篇 |
免费 | 86篇 |
国内免费 | 2篇 |
专业分类
化学 | 1128篇 |
晶体学 | 19篇 |
力学 | 9篇 |
数学 | 38篇 |
物理学 | 353篇 |
出版年
2023年 | 9篇 |
2022年 | 16篇 |
2021年 | 18篇 |
2020年 | 20篇 |
2019年 | 25篇 |
2018年 | 21篇 |
2017年 | 13篇 |
2016年 | 42篇 |
2015年 | 45篇 |
2014年 | 45篇 |
2013年 | 65篇 |
2012年 | 68篇 |
2011年 | 104篇 |
2010年 | 42篇 |
2009年 | 47篇 |
2008年 | 63篇 |
2007年 | 76篇 |
2006年 | 65篇 |
2005年 | 58篇 |
2004年 | 66篇 |
2003年 | 46篇 |
2002年 | 56篇 |
2001年 | 40篇 |
2000年 | 36篇 |
1999年 | 22篇 |
1997年 | 10篇 |
1996年 | 23篇 |
1995年 | 10篇 |
1994年 | 18篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 20篇 |
1987年 | 16篇 |
1985年 | 14篇 |
1984年 | 23篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 21篇 |
1979年 | 20篇 |
1978年 | 25篇 |
1977年 | 11篇 |
1976年 | 18篇 |
1975年 | 9篇 |
1974年 | 17篇 |
1973年 | 9篇 |
1968年 | 8篇 |
排序方式: 共有1547条查询结果,搜索用时 15 毫秒
1.
2.
Hiroto Kudo Nobuhito Ito Keiji Nakajima Masami Ochiai Tadatomi Nishikubo 《Journal of polymer science. Part A, Polymer chemistry》2007,45(19):4421-4429
The polyaddition of fluorine‐containing bis(epoxide)s and fluorine‐containing triazine di(aryl ether)s were examined to give the corresponding fluorine‐containing poly(cyanurate)s. It was observed that the synthesized fluoropolymers had good thermal stabilities and good film‐forming properties. The glass transition temperatures (Tg's) and refractive‐indices (nD's) of synthesized polymers were determined by differential scanning calorimetry and ellipsometry, respectively, and it was found that the values of Tg's and nD's were supported by their fluorine containing ratios and skeletons. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4421–4429, 2007 相似文献
3.
The running coupling and the Kugo-Ojima parameter of unquenched lattice Landau gauge are simulated and compared with the continuum
theory. Although the running coupling measured by the ghost and gluon dressing function is infrared suppressed, the running
coupling has a maximum of α0 ∼ 2 − 2.5 at around q = 0.5 GeV irrespective of the fermion actions (Wilson fermions and Kogut-Susskind (KS) fermions). The Kugo-Ojima parameter
c which saturated to about 0.8 in quenched simulations becomes consistent with 1 in the MILC configurations produced with the
use of the Asqtad action, after averaging the dependence on polarization directions caused by the asymmetry of the lattice.
The presence of the correction factor 1 + c
1/q
2 in the running coupling depends on the lattice size and the sea quark mass. In the large lattice size and small sea quark
mass, c
1 is confirmed of the order of a few GeV. The MILC configuration of a = 0.09 fm suggests also the presence of dimension-4 condensates with a sign opposite to the dimension-2 condensates. The
gluon propagator, the ghost propagator, and the running coupling are compared with recent pQCD results including an anomalous
dimension of fields up to the four-loop level. 相似文献
4.
Trifluoromethylation onto the tetrafluorophthalonitrile and tetrafluoroisophthalonitrile has been carried out using CF3TMS-CuI-KF system, and it was demonstrated that these trifluoromethylation enabled us to successfully construct di- and/or tri-trifluoromethylated benzonitriles via the decyanotrifluoromethylation. 相似文献
5.
Strained layer quantum well semiconductor optical amplifiers: Polarization insensitive amplification
M. Joma H. Hofukawa M. Nakajima M. Kawahara T. Kamijoh 《Fiber and Integrated Optics》1991,10(4):361-364
Polarization insensitive optical amplification was demonstrated in newly developed semiconductor optical amplifiers that have strained GalnAsP quantum well structures. We tailored the active region of the quaternary strained layer quantum well structure with a small biaxially tensile strain of 0.2% in the well layers for polarization insensitive operation. 相似文献
6.
Nahoko Yamaji Manabu Horikawa Hideo Naoki Terumi Nakajima 《Tetrahedron letters》2004,45(28):5371-5373
A novel polyamine toxin, named MG30, was isolated from the venom of the spider, Macrothele gigas, and its structure was elucidated by two-dimensional NMR and mass analysis. In addition, the enantioselective synthesis of MG30 was achieved to assign its absolute stereochemistry. 相似文献
7.
S. Sasa A. Nakashima Y. Nakajima M. Inoue 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):224
We fabricated nanoscale open-dot structures in an InAs surface inversion layer using an atomic-force-microscope oxidation process. Due to its superior nanofabrication capability, small open-dot structures with the feature size ranging between 100 and 300 nm were successfully fabricated. The magnetoresistance signal measured at 4.2 K showed reproducible fluctuations and a periodic oscillation component that varies in both amplitude and periodicity depending on the dot size. We show that the period of the oscillations corresponds to that of the Aharonov–Bohm effect and propose that the possible mechanism for the oscillations is due to the formation of a one-dimensional electron channel enclosing the open-dot structure as a result of the electron transfer from the InAs oxide to InAs. 相似文献
8.
9.
Tasuku Nakajima Takayuki Kurokawa Hidemitsu Furukawa Qiu Ming Yu Yoshimi Tanaka Yoshihito Osada Jian Ping Gong 《高分子科学》1996,(1):1-9
Living tissues work with fantastic functions in soft and wet gel-like state. Thus, hydrogels have attracted much attention as excellent soft & wet materials, suitable for making artificial organs for medical treatments.However, conventional hydrogels are mechanically too weak for practical uses. We have created double network (DN) hydrogels with extremely high mechanical strength in order to overcome this problem. DN gels are interpenetrating network (IPN) hydrogels consisting of rigid polyelectrolyte and soft neutral polymer. Their excellent mechanical properties cannot be explained by the standard fracture theories. In this paper, we discuss about the toughening mechanism of DN gels in accordance with their characteristic behavior, such as large hysteresis and necking phenomenon. We also describe the results on tissue engineering application of DN gels. 相似文献
10.