全文获取类型
收费全文 | 1077篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
化学 | 856篇 |
晶体学 | 10篇 |
力学 | 15篇 |
数学 | 42篇 |
物理学 | 176篇 |
出版年
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 14篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 42篇 |
2012年 | 39篇 |
2011年 | 46篇 |
2010年 | 34篇 |
2009年 | 34篇 |
2008年 | 62篇 |
2007年 | 54篇 |
2006年 | 73篇 |
2005年 | 52篇 |
2004年 | 32篇 |
2003年 | 37篇 |
2002年 | 28篇 |
2001年 | 18篇 |
2000年 | 44篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 31篇 |
1991年 | 20篇 |
1990年 | 17篇 |
1989年 | 18篇 |
1988年 | 17篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 30篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 5篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1974年 | 11篇 |
1973年 | 11篇 |
1971年 | 5篇 |
1966年 | 8篇 |
排序方式: 共有1099条查询结果,搜索用时 15 毫秒
91.
Masanori KawasakiKosuke Namba Hidekazu TsujishimaTetsuro Shinada Yasufumi Ohfune 《Tetrahedron letters》2003,44(6):1235-1238
Highly enantioselective synthesis of (2R)-α-(hydroxymethyl)glutamate (1), a selective agonist of mGluR2 and 3, was achieved in short steps using an asymmetric version of the Strecker synthesis. This was converted into its α-methoxymethyl- and α-benzyloxymethyl derivatives 2 and 3, possible ligands as tools to investigate glutamate receptors, via protection of the sterically hindered amino group by means of phase transfer catalyst. 相似文献
92.
Kawai K Takada T Nagai T Cai X Sugimoto A Fujitsuka M Majima T 《Journal of the American Chemical Society》2003,125(52):16198-16199
The hole transfer causes the long-lived charge-separated state in DNA during the photosensitized one-electron oxidation of DNA. The combination of the transient absorption measurement and DNA damage quantification by HPLC clearly demonstrated that the yield of the DNA damage correlates well with the lifetime of the charge-separated state. 相似文献
93.
94.
Levels of intracellular Ca2+ were monitored using fluorescence from Ca2+-sensitive dyes in chick embryonic heart cells cultured in an annular geometry. There was spontaneous starting and stopping of reentrant waves of activity. The results are modeled using modified FitzHugh-Nagumo equations representing pacemakers embedded in a conducting medium. These results provide a potential mechanism for spontaneous abnormal cardiac rhythms in which there are rapid heart beats (tachycardias) that repetitively start and stop. 相似文献
95.
Shinsuke Hara Hidekazu Kobayashi Hiroki I. Fujishiro Hirofumi Miki 《Surface science》2007,601(12):2415-2419
We have studied Si(0 0 1)-Ga surface structures formed at Ga coverages of slightly above 0.50 monolayer (ML) at 250 °C by scanning tunneling microscopy (STM). 4 × 2-, 5 × 2-, and 6 × 2-Ga structures were observed in a local area on the surface. The 4 × 2-Ga structure consists of three protrusions, as observed in filled- and empty-state STM images. The characters of these structures are clearly different from those of other Si(0 0 1)-Ga structures. We also performed an ab initio calculation of the energetics for several possible models for the 4 × 2-Ga structure, and clarified that the three-orthogonal-Ga-dimer model is the most stable. Also, the results of comparing the simulated STM images and observation images at various bias voltages indicate that this structural model is the most favorable. 相似文献
96.
In applying Pressure-Sensitive Paint (PSP) to low-speed flow wind tunnel testing, it is important to minimize any measurement
uncertainties. There are various error sources such as camera noise, misalignment of images due to model displacement and
temperature distribution over the model. Among these factors, the effects of temperature distribution change during tests
on pressure measurement accuracies were studied in the present paper. Pressure and temperature distributions over a simplified
car model (1/10 scale Ahmed model) were measured using PSP and Temperature-Sensitive Paint (TSP). Sequential images were acquired
at the same intervals over the entire test period, including for the conditions before and after the tunnel run. As a result,
it was found that the measurement error caused by temperature distribution over the model could be reduced using a single-point
temperature measurement. In addition, by measuring surface temperature distributions on the model using TSP, it was proved
that the most accurate pressure measurement could be made by rationing the wind-off image acquired immediately after shutting
down the tunnel to the wind-on image acquired immediately before shutting down the tunnel. Using the present measurement technique,
complicated pressure fields over the Ahmed model were successfully visualized. 相似文献
97.
98.
Hisatoyo Morinaga Yusuke Ujihara Naho Yuto Daisuke Nagai Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2011,49(24):5210-5216
Metal‐free controlled ring‐opening polymerization of glycidyl phenyl ether (GPE) was achieved using tetra‐n‐butylammonium fluoride (Bu4NF) as an initiator in the presence of water and ethanol as chain transfer agents (CTAs). Number‐averaged molecular weight of poly(GPE) increased with an increase of [GPE]0/([Bu4NF]0 + [CTA]0) values, showing relatively narrow molecular weight distributions. NMR spectroscopic analysis exhibited a formation of ethoxy groups as well as FCH2 at the initiating polymer chain‐end when ethanol was used as the CTA in the polymerization. These results indicate that Bu4NF acts as a catalyst as well as the initiator for this polymerization system. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
99.
Effect of refraction index and thickness of the light guide in the position-sensitive gamma-ray detector using compact PS-PMTs 总被引:1,自引:0,他引:1
Koji Inoue Haruo Saito Yasuyuki Nagashima Toshio Hyodo Yasuyoshi Nagai Shinichi Muramatsu Shota Nagai 《Radiation Physics and Chemistry》2000,58(5-6):763-766
We constructed a position-sensitive gamma-ray detector consisting of an array of BGO scintillators, a light guide and compact PS-PMTs. The effects of refractive index and thickness of the light guide of a glass plate on the detector performance were investigated. A light guide with higher refractive index and smaller thickness is found better for a good spatial resolution. 相似文献
100.