全文获取类型
收费全文 | 5687篇 |
免费 | 212篇 |
国内免费 | 18篇 |
专业分类
化学 | 4416篇 |
晶体学 | 50篇 |
力学 | 79篇 |
数学 | 243篇 |
物理学 | 1129篇 |
出版年
2023年 | 33篇 |
2022年 | 50篇 |
2021年 | 61篇 |
2020年 | 72篇 |
2019年 | 91篇 |
2018年 | 58篇 |
2017年 | 58篇 |
2016年 | 123篇 |
2015年 | 131篇 |
2014年 | 154篇 |
2013年 | 273篇 |
2012年 | 301篇 |
2011年 | 321篇 |
2010年 | 158篇 |
2009年 | 158篇 |
2008年 | 321篇 |
2007年 | 304篇 |
2006年 | 327篇 |
2005年 | 317篇 |
2004年 | 296篇 |
2003年 | 238篇 |
2002年 | 267篇 |
2001年 | 153篇 |
2000年 | 110篇 |
1999年 | 88篇 |
1998年 | 63篇 |
1997年 | 54篇 |
1996年 | 74篇 |
1995年 | 69篇 |
1994年 | 72篇 |
1993年 | 59篇 |
1992年 | 85篇 |
1991年 | 68篇 |
1990年 | 60篇 |
1989年 | 56篇 |
1988年 | 46篇 |
1987年 | 39篇 |
1986年 | 52篇 |
1985年 | 74篇 |
1984年 | 63篇 |
1982年 | 57篇 |
1981年 | 32篇 |
1980年 | 35篇 |
1979年 | 52篇 |
1978年 | 41篇 |
1977年 | 45篇 |
1976年 | 34篇 |
1975年 | 31篇 |
1974年 | 33篇 |
1973年 | 40篇 |
排序方式: 共有5917条查询结果,搜索用时 542 毫秒
1.
Optical Review - This paper demonstrates a method to estimate the depth of a fluorescence object in turbid media using dual-wavelength excited photodynamic diagnosis, to aid in the invasion depth... 相似文献
2.
Mitsuki Yamashita Yuna Kawasumi Yuki Tachibana Dr. Shinnosuke Horiuchi Dr. Koji Yamamoto Prof. Tetsuro Murahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(5):1212-1216
Although small cyclic- and open-chain unsaturated hydrocarbon anions such as cyclopentadienide and open-chain pentadienide are used as the strongly electron-donating auxiliary ligands for metal complexes, more extended π-conjugated unsaturated hydrocarbon anions have rarely been used in coordination chemistry, despite their potential ability to serve as the multiply bridging π-ligands for metal clusters. This work reports isolation of metal chain clusters bearing the multi-dentate, open-chain extended unsaturated hydrocarbon anion ligands. The extended open-chain π-conjugated polyenyl ligands could effectively stabilize oxidized palladium chains, including an unprecedented [Pd4]4+ chain. 相似文献
3.
4.
5.
It is an important issue to clarify the minimum required size of a specimen for the accurate measurement of oblique incidence absorption coefficient. Investigation is made on the basis of experimental studies in a laboratory, using Aoshima's time stretched pulse technique. Measurements are carried out for glass fiber with thickness of 50 and 100 mm as highly absorbing materials and for ceramic with a thickness of 52 mm as relatively low absorbing material. The tested surface areas range from 0.0625 to 42 m2 for glass fiber and from 0.1563 to 39.168 m2 for ceramics. The absorption coefficients are determined at incidence angles from 0 to 45° in increments of 15°. With consideration of an active surface bounded by ellipse orbit, the minimum required surface area is 16 m2 with a ratio of length to width of about 1.25. This value is twice the area size of the active surface, which is calculated from the geometry of source and microphone, and the width of the temporal window. 相似文献
6.
7.
Kouichi Akahane Naokatsu Yamamoto Naoki Ohtani 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):295
We fabricated InAs quantum dots (QDs) with a GaAsSb strain-reducing layer (SRL) on a GaAs(0 0 1) substrate. The wavelength of emission from InAs QD is shown to be controllable by changing the composition and thickness of the SRL. An increase in photoluminescence intensity with increasing compositions of Sb and thickness of the GaAsSb SRL is also seen. The efficiency of radiative recombination was improved under both conditions because the InAs/GaAsSb/GaAs hetero-interface band structure more effectively suppressed carrier escape from the InAs QDs. 相似文献
8.
D. Amutha Rani Y. Yamamoto S. Mohri M. Sivakumar Y. Tsujita H. Yoshimizu 《Journal of Polymer Science.Polymer Physics》2003,41(3):269-273
In this study, a novel stepwise extraction method has been examined. The guest molecules housed between the helices of the clathrate δ form of syndiotactic polystyrene can be removed completely with this method. A systematic study of the preparation of a solvent‐free mesophase (emptied clathrate) membrane, its helical and residual solvent contents, and its structural transformations has been performed. In this first attempt, an enhancement in the TTGG helical content has been observed in the extracted membrane, and a conceptual mechanism is proposed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 269–273, 2003 相似文献
9.
Akira Yanagisawa Prof. Dr. Takahiro Suzuki Takanori Koide Shogo Okitsu Takayoshi Arai Prof. Dr. 《化学:亚洲杂志》2008,3(10):1793-1800
A Barbier‐type regioselective propargylation of aldehydes and ketones with (3‐bromobut‐1‐ynyl)trimethylsilane has been achieved using reactive barium as a low‐valent metal in THF. Especially in the case of ketones, the corresponding homopropargylic alcohols form almost exclusively. In the reaction of α,β‐unsaturated carbonyl compounds, only 1,2‐adducts have been observed. This method is also applicable to propargylation of imines, and the corresponding homopropargylic amines are obtained regiospecifically in good yields with diastereomeric ratios of up to 87:13. 相似文献
10.
R. Bairava Ganesh Hitoshi Matsuo Takahiro Kawamura Yoshihiro Kangawa Koji Arafune Yoshio Ohshita Masafumi Yamaguchi Koichi Kakimoto 《Journal of Crystal Growth》2008,310(11):2697-2701
Multicrystalline silicon was grown by unidirectional solidification method using the accelerated crucible rotation technique. The application of the accelerated crucible rotation technique in unidirectional solidification method induced growth striations across the axial direction of the grown crystal. This striation pattern was observed from carbon concentration distribution, obtained by using Fourier transform infrared spectroscopy. The generated striation pattern was found to be weak and discontinuous. Some striations were absent, probably due to back melting, caused during each crucible rotation. From the growth striations and applied time period in crucible rotation, the growth rate was estimated by using Fourier transformation analysis. 相似文献