全文获取类型
收费全文 | 2292篇 |
免费 | 67篇 |
国内免费 | 9篇 |
专业分类
化学 | 1777篇 |
晶体学 | 22篇 |
力学 | 25篇 |
数学 | 179篇 |
物理学 | 365篇 |
出版年
2023年 | 9篇 |
2022年 | 13篇 |
2021年 | 9篇 |
2020年 | 16篇 |
2019年 | 25篇 |
2018年 | 10篇 |
2017年 | 20篇 |
2016年 | 42篇 |
2015年 | 31篇 |
2014年 | 47篇 |
2013年 | 115篇 |
2012年 | 121篇 |
2011年 | 144篇 |
2010年 | 70篇 |
2009年 | 77篇 |
2008年 | 132篇 |
2007年 | 157篇 |
2006年 | 153篇 |
2005年 | 171篇 |
2004年 | 137篇 |
2003年 | 124篇 |
2002年 | 129篇 |
2001年 | 34篇 |
2000年 | 40篇 |
1999年 | 27篇 |
1998年 | 29篇 |
1997年 | 30篇 |
1996年 | 26篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 25篇 |
1984年 | 34篇 |
1983年 | 20篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 26篇 |
1979年 | 27篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 12篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1973年 | 13篇 |
排序方式: 共有2368条查询结果,搜索用时 0 毫秒
1.
2.
3.
We study the half-space problem of the nonlinear Boltzmann equation, assigning the Dirichlet data for outgoing particles
at the boundary and a Maxwellian as the far field. We will show that the solvability of the problem changes with the Mach
number ℳ∞ of the far Maxwellian. If ℳ∞<−1, there exists a unique smooth solution connecting the Dirichlet data and the far Maxwellian for any Dirichlet data sufficiently
close to the far Maxwellian. Otherwise, such a solution exists only for the Dirichlet data satisfying certain admissible conditions.
The set of admissible Dirichlet data forms a smooth manifold of codimension 1 for the case −1<ℳ∞<0, 4 for 0<ℳ∞<1 and 5 for ℳ∞>1, respectively. We also show that the same is true for the linearized problem at the far Maxwellian, and the manifold is,
then, a hyperplane. The proof is essentially based on the macro-micro or hydrodynamics-kinetic decomposition of solutions
combined with an artificial damping term and a spatially exponential decay weight.
Received: 20 April 2002 / Accepted: 4 December 2002
Published online: 21 March 2003
Communicated by H.-T. Yau 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.
A new method for rotation and brightness invariant pattern recognition was proposed by applying multiple circular harmonic expansions to the joint transform correlator. The amplitudes of the multiple orders of circular harmonic expansions made from a detecting image were synthetically modified to respond to the same auto-correlation peaks. These modified circular harmonic expansions were arranged in the input plane as reference patterns together with an arbitrary target pattern, and the correlation signals between them were calculated in the subtracted joint transform correlator. The fraction of the correlation-peak intensities between the target and the references were extracted as a new discrimination parameter. This new parameter performs pattern recognition under rotation and brightness invariance with good discriminability. Its high discriminability has been proved in computer simulations using the face image patterns of many individuals. 相似文献
6.
Betancourt L Takao T Hernandez L Padron G Shimonishi Y 《Journal of mass spectrometry : JMS》1999,34(3):169-174
High-resolution matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to characterize the primary structure of the levansucrase (EC 2.4.1.10) secreted by Acetobacter diazotropicus SRT4. The technique permitted not only the reading frame of this enzyme, the amino acid sequence of which was deduced from DNA, but also the elucidation of an N-terminal blocking group and the position of a disulfide bridge between Cys309 and Cys365 among the three Cys residues. A free cysteine (Cys127) was identified by modifying an intact molecule with a sulfhydryl reagent, 5-(octyldithio)-2-nitrobenzoic acid, under non-reducing conditions. In addition, the enzyme obtained by site-directed mutagenesis at Asp279 to Asn279 was also identified by the above methods. Post-source decay analysis of the tryptic peptide containing the mutation site unequivocally revealed an Asn residue at position 279. 相似文献
7.
8.
Atsushi Ikeda Masaru Kawaguchi Yoshio Suzuki Tsukasa Hatano Munenori Numata Seiji Shinkai Akio Ohta Makoto Ohta 《Journal of inclusion phenomena and macrocyclic chemistry》2000,38(1-4):163-170
The calixarene-fullerene interaction,which causes only a slight change in the absorptionspectra, has been substantiated by calorimetricmeasurements: the H° values arecomparable with those obtained from the associationconstants estimated by a spectroscopic method. Furthermore, we determined the association constantbetween homooxacalix[3]arene and [60]fullerenederivatives with a porphyrin moiety by fluorescencespectra. 相似文献
9.
The solubility of glycine,
-alanine,
-valine,
-leucine, and
-isoleucine in water was measured at 298.15 K and pressures up to 400 MPa. The standard deviation of the logarithm of the solubility is 0.001–0.003, equal to or better than the accuracy of atmospheric pressure measurement in the literature (0.001–0.05). A variety of solubility phenomena were observed. The solubility of glycine decreased with increasing pressure, whereas that of
-alanine increased. The
-valine and
-isoleucine have a solubility maximum at around 100 MPa, and
-leucine seems to exhibit a solid-phase phase transition at around 200 MPa. Pressure coefficient of the solubilities at 0.10 MPa is compared with that thermodynamically estimated in reference to aqueous density measurements of glycine and
-alanine at 298.15 K and 0.10 MPa, supporting a reliability of our high-pressure measurements. 相似文献
10.