全文获取类型
收费全文 | 6662篇 |
免费 | 113篇 |
国内免费 | 31篇 |
专业分类
化学 | 4185篇 |
晶体学 | 35篇 |
力学 | 183篇 |
数学 | 1365篇 |
物理学 | 1038篇 |
出版年
2020年 | 59篇 |
2019年 | 50篇 |
2016年 | 95篇 |
2015年 | 83篇 |
2014年 | 94篇 |
2013年 | 229篇 |
2012年 | 205篇 |
2011年 | 221篇 |
2010年 | 147篇 |
2009年 | 144篇 |
2008年 | 225篇 |
2007年 | 238篇 |
2006年 | 192篇 |
2005年 | 223篇 |
2004年 | 189篇 |
2003年 | 160篇 |
2002年 | 182篇 |
2001年 | 87篇 |
2000年 | 114篇 |
1999年 | 80篇 |
1998年 | 69篇 |
1997年 | 88篇 |
1996年 | 89篇 |
1995年 | 101篇 |
1994年 | 95篇 |
1993年 | 84篇 |
1992年 | 109篇 |
1991年 | 73篇 |
1990年 | 79篇 |
1989年 | 85篇 |
1988年 | 101篇 |
1987年 | 83篇 |
1986年 | 103篇 |
1985年 | 130篇 |
1984年 | 125篇 |
1983年 | 95篇 |
1982年 | 132篇 |
1981年 | 128篇 |
1980年 | 120篇 |
1979年 | 131篇 |
1978年 | 114篇 |
1977年 | 109篇 |
1976年 | 102篇 |
1975年 | 116篇 |
1974年 | 87篇 |
1973年 | 90篇 |
1972年 | 56篇 |
1971年 | 62篇 |
1970年 | 64篇 |
1966年 | 48篇 |
排序方式: 共有6806条查询结果,搜索用时 15 毫秒
1.
Walter Benz 《Monatshefte für Mathematik》2004,141(1):1-10
The lines of euclidean and hyperbolic geometries are characterized as metric lines in the sense of Blumenthal–Menger, and the lines of spherical and elliptic geometry as periodic ones. In euclidean geometries there do not exist periodic lines. 相似文献
2.
Hans-Rudolf Buser Michael Oehme Walter Vetter Bernd Luckas 《Fresenius' Journal of Analytical Chemistry》1993,347(12):502-512
Summary Conventional electron ionization (EI) mass spectrometry (MS) and MS/MS techniques were applied to the analysis of two abundant octa and nonachlorobornanes isolated from seals of the Baltic sea and originating from technical toxaphene. The exact sterical structures of the two compounds were previously determined using nuclear magnetic resonance (NMR) spectroscopy by two independent research groups. The MS and MS/MS data generated in this study allowed partial structure elucidation of these polychlorobornanes, in particular revealing the distribution of the Cl substituents between the six-membered carbon ring, the bridge and the bridgehead in the parent bornane structure. Fragmentation of the six-membered carbon ring and the bridge by retro-Diels-Alder (RDA) and related mechanisms was discovered by studying specific parent/daughter ion transitions. The detailed fragmentation pathways formulated may be applicable to the structure elucidation of other toxaphene congeners and the monitoring of strategic transitions is highly selective for the detection of these compounds in technical toxaphene and in environmental samples. 相似文献
3.
Walter Benz Hamburg 《Results in Mathematics》2003,44(1-2):41-43
It will be proved that the functional equation of periodic lines has no solution for hyperbolic distances. 相似文献
4.
Endoscopic Observation of Tissue by Narrowband Illumination 总被引:6,自引:0,他引:6
Kazuhiro Gono Kenji Yamazaki Nobuyuki Doguchi Tetsuo Nonami Takashi Obi Masahiro Yamaguchi Nagaaki Ohyama Hirohisa Machida Yasushi Sano Shigeaki Yoshida Yasuo Hamamoto Takao Endo 《Optical Review》2003,10(4):211-215
We propose a new illumination method for a medical endoscope: narrow band imaging (NBI), in which the spectral bandwidth of the filtered light is narrowed. To confirm how the spectral specifications of the filtered light influence a reproduced image, an experiment was conducted observing the endoscopic images of the back mucosa of a human tongue. In addition, the effect of NBI on endoscopic images was investigated through preliminary clinical tests in colonoscopy and upper gastrointestinal endoscopy. It has been shown that NBI can enhance the capillary pattern and the crypt pattern on the mucosa. These patterns are useful features for diagnosing an early cancer. 相似文献
5.
6.
7.
We investigate function spaces of generalised smoothness of Besov and Triebel–Lizorkin type. Equivalent quasi-norms in terms
of maximal functions and local means are given. An atomic decomposition theorem for this type of spaces is proved.
Mathematics Subject Classification (2000) 46E35 相似文献
8.
6-Thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes and Isothiocyanatophosphine-sulfides from (Methylidenamino)phosphines, Carbon Disulfide, and Acetylene- or Ethylene Derivatives (Methylidenamino)phosphines react with carbon disulfide to 1,3,2-thiazaphosphete derivatives 2 . Acetylenedicarboxylates give with 2 6-thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes 4a , b , and acrylates yield isothio-cyanatophosphin-sulfides 5a – c . The structures of 4a and 5a are proven by an X-ray diffraction analysis. 相似文献
9.
We study the transversal spin–spin correlations in the non-equilibrium steady state of the XY chain constructed by coupling a finite cutout of the chain to the two infinite parts to its left and right acting as thermal reservoirs at different temperatures. We prove that the spatial decay of these correlations is at least exponentially fast. 相似文献
10.