全文获取类型
收费全文 | 1668篇 |
免费 | 140篇 |
国内免费 | 145篇 |
专业分类
化学 | 1314篇 |
晶体学 | 19篇 |
力学 | 52篇 |
综合类 | 9篇 |
数学 | 113篇 |
物理学 | 446篇 |
出版年
2023年 | 8篇 |
2022年 | 31篇 |
2021年 | 33篇 |
2020年 | 57篇 |
2019年 | 65篇 |
2018年 | 43篇 |
2017年 | 31篇 |
2016年 | 63篇 |
2015年 | 80篇 |
2014年 | 73篇 |
2013年 | 96篇 |
2012年 | 111篇 |
2011年 | 106篇 |
2010年 | 83篇 |
2009年 | 89篇 |
2008年 | 98篇 |
2007年 | 85篇 |
2006年 | 80篇 |
2005年 | 78篇 |
2004年 | 66篇 |
2003年 | 69篇 |
2002年 | 76篇 |
2001年 | 53篇 |
2000年 | 38篇 |
1999年 | 31篇 |
1998年 | 16篇 |
1997年 | 9篇 |
1996年 | 21篇 |
1995年 | 11篇 |
1994年 | 18篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 20篇 |
1990年 | 21篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 27篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 8篇 |
排序方式: 共有1953条查询结果,搜索用时 15 毫秒
1.
Stability Properties of Maps Between Hopf Spaces 总被引:1,自引:0,他引:1
2.
Hiroshi Maruyama Tadao Ishii Naruhiko Bamba Hironobu Maeda Akihisa Koizumi Yuzo Yoshikawa Hitoshi Yamazaki 《Physica C: Superconductivity and its Applications》1989,160(5-6):524-532
The temperature dependence of the extended X-ray absorption fine structure (EXAFS) is studied in the high Tc superconductors, YBa2Cu3O7−δ. The measurements were done at the Cu K-edge for samples of two orthorhombic phases (Tc≈90 K and ≈58 K, respectively) and a nonsuperconducting tetragonal phase. Interatomic distances and mean square relative displacements σ2 for Cu-O bonds are determined by the least squares refinement. The results indicate that values of σ2 increase near Tc for both the orthorhombic samples. It is concluded that this anomalous behavior related to Tc is caused by an anomalous vibration of oxygen atoms in the Ba-O layer. Changes in the Cu-O distances from 300 to 20 K are not found. 相似文献
3.
Lian-Chun Park Tatsuo Maruyama Noriho Kamiya Masahiro Goto Hiroyuki Kuma Naotaka Hamasaki 《Analytical sciences》2004,20(11):1609-1611
The emergence of drug-resistant hepatitis B virus (HBV) has been reported in patients with prolonged administration of lamivudine, which is a potent drug for the prevention of HBV infection. Lamivudine-resistant HBV has several types of mutations at the YMDD motif of its DNA polymerase. We successfully demonstrated that monitoring the hybridization behavior in nanostructured reverse micelles enables us to detect single nucleotide polymorphisms (SNPs). With the aid of reverse micelles, a model 40-mer oligonucleotide containing a single-base substitution was clearly distinguished from the normal, complementary oligonucleotide. In addition, we extended this technique to a high-throughput analysis. The results obtained with a 96-well micro-plate reader indicated the possibility of SNPs detection toward multiple samples of patients. 相似文献
4.
The Constraint Molecular Dynamics approach is illustrated together with calculation on different heavy ion collisions. In particular the charge-mass distribution produced in the collision 124Sn + 64Ni and 112Sn + 58Ni at 35 MeV/nucleon is discussed. By comparing the Y = (N ? Z)/A distributions for fragments produced in central collisions it results that this observable can be sensitive to the dynamic effects induced on the two systems by the different charge/mass ratio. 相似文献
5.
Yan Shun MA Qing Hua MENG Hong Yu SHI Yuan De LONG Tian Bao HUANG 《中国化学快报》2006,17(6):807-808
Dencichine (β-N-oxalyl-L-α, β-diaminopropionic acid, L-ODAP), a nonprotein amino acid, is a haemostatic agent present in important Chinese medicinal herbs such as Panax notoginseng, as well as other Panax species1. It was first isolated from the seeds … 相似文献
6.
Ying‐Ling Liu Chuan‐Shao Wu Yie‐Shun Chiu Wen‐Hsuan Ho 《Journal of polymer science. Part A, Polymer chemistry》2003,41(15):2354-2367
A novel epoxy system was developed through the in situ curing of bisphenol A type epoxy and 4,4′‐diaminodiphenylmethane with the sol–gel reaction of a phosphorus‐containing trimethoxysilane (DOPO–GPTMS), which was prepared from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with 3‐glycidoxypropyltrimethoxysilane (GPTMS). The preparation of DOPO–GPTMS was confirmed with Fourier transform infrared, 1H and 31P NMR, and elemental analysis. The resulting organic–inorganic hybrid epoxy resins exhibited a high glass‐transition temperature (167 °C), good thermal stability over 320 °C, and a high limited oxygen index of 28.5. The synergism of phosphorus and silicon on flame retardance was observed. Moreover, the kinetics of the thermal oxidative degradation of the hybrid epoxy resins were studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2354–2367, 2003 相似文献
7.
Yuzo Maruyama 《Journal of multivariate analysis》2004,88(2):320-334
We consider estimation of a multivariate normal mean vector under sum of squared error loss.We propose a new class of minimax admissible estimator which are generalized Bayes with respect to a prior distribution which is a mixture of a point prior at the origin and a continuous hierarchical type prior. We also study conditions under which these generalized Bayes minimax estimators improve on the James–Stein estimator and on the positive-part James–Stein estimator. 相似文献
8.
9.
Three New Diarylpropanes from Dioscorea composita 总被引:1,自引:0,他引:1
ShunLiYANG XiKuiLIU 《中国化学快报》2005,16(1):57-60
Three new diarylpropanes were isolated from the dried rhizomes of Dioscorea composita Hemsl., and their structures were determined as 1, 3-bis-(2-hydroxy-4-methoxyphenyl) propane (1), 1, 3-bis-(2, 4-dihydroxyphenyl)propane (2), 1-(2′-hydroxy-4′-O-β-D- glucopymnosy-phenyl)-3-(2“, 4“-dihydroxyphenyl)propane (3), by spectroscopic analysis, respectively. 相似文献
10.
Hee Seok Choi Young Han Kim Shun Myung Shin 《Journal of polymer science. Part A, Polymer chemistry》2006,44(8):2428-2439
An in‐line monitoring device using a quartz crystal resonator for thin film polymerization was proposed, and its performance has been evaluated by implementing in the UV polymerization of 2‐hydroxyethyl methacrylate with a photoinitiator of 1‐chloroanthraquinone. Because the variation of resonant resistance of the resonator is proportional to the square root of viscosity change that is closely related to the polymerization degree, the resistance can be used as a measure of the polymerization degree. The resistance measurements were compared with the outcome of instrumental analyses of polymerization degree using an FTIR spectrometer and a gel permeation chromatograph. The experimental results showed that the resistance measurements were consistent with the experimental outcome of the instrumental analyses, and this indicates the effectiveness of the proposed device. Owing to the simplicity and availability of the resonator system, its wide utilization in the monitoring of a variety of film polymerization processes, including photoresistor application, is expected. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2428–2439, 2006 相似文献