全文获取类型
收费全文 | 1178篇 |
免费 | 42篇 |
国内免费 | 9篇 |
专业分类
化学 | 695篇 |
晶体学 | 3篇 |
力学 | 61篇 |
综合类 | 4篇 |
数学 | 180篇 |
物理学 | 286篇 |
出版年
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 20篇 |
2014年 | 23篇 |
2013年 | 107篇 |
2012年 | 43篇 |
2011年 | 38篇 |
2010年 | 34篇 |
2009年 | 30篇 |
2008年 | 44篇 |
2007年 | 34篇 |
2006年 | 28篇 |
2005年 | 23篇 |
2004年 | 25篇 |
2003年 | 32篇 |
2002年 | 33篇 |
2001年 | 34篇 |
2000年 | 34篇 |
1999年 | 18篇 |
1998年 | 16篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1990年 | 26篇 |
1989年 | 18篇 |
1988年 | 23篇 |
1987年 | 21篇 |
1986年 | 12篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 18篇 |
1982年 | 27篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1977年 | 15篇 |
1976年 | 7篇 |
1975年 | 26篇 |
1974年 | 10篇 |
1973年 | 17篇 |
排序方式: 共有1229条查询结果,搜索用时 187 毫秒
1.
Jan E. Åman Ingemar Bengtsson Narit Pidokrajt 《General Relativity and Gravitation》2006,38(8):1305-1315
The Hessian of either the entropy or the energy function can be regarded as a metric on a Gibbs surface. For two parameter families of asymptotically flat black holes in arbitrary dimension one or the other of these metrics are flat, and the state space is a flat wedge. The mathematical reason for this is traced back to the scale invariance of the Einstein–Maxwell equations. The picture of state space that we obtain makes some properties such as the occurence of divergent specific heats transparent.Supported by VR. 相似文献
2.
P G Stelmachowicz D E Lewis L L Larson W Jesteadt 《The Journal of the Acoustical Society of America》1987,81(6):1881-1887
Growth-of-masking functions were obtained from 19 normal and 5 hearing-impaired listeners using a simultaneous-masking paradigm. When masker and probe frequency are identical, the slope of masking approximates 1.0 for both normal-hearing and impaired listeners. For masker frequencies less than or greater than probe frequency, the slopes for impaired listeners are shallower than those of normals. These findings are consistent with previously reported physiological data (single-fiber rate versus level and AP masking functions) for animals with induced cochlear lesions. Results are discussed in terms of a potential masking technique to estimate the growth of response in normal and impaired ears. 相似文献
3.
Takeshi Kitatani Masahiko Kondow Koji Nakahara M. C. Larson Kazuhisa Uomi 《Optical Review》1998,5(2):69-71
Temperature stability of the threshold current and the lasing wavelength is investigated in a 1.3-μm GaInNAs/ GaAs single quantum-well laser. The measured characteristic-temperature was 88 K. The small wavelength shift per change in temperature of 0.35 nm/°C was obtained, indicating the superior lasing-wavelength stability. Therefore, it is shown experimentally that GaInNAs is very promising material for the fabrication of light source with excellent high-temperature performance for optical fiber communications. 相似文献
4.
5.
6.
7.
Pal R Yang M Lin R Johnson BN Srivastava N Razzacki SZ Chomistek KJ Heldsinger DC Haque RM Ugaz VM Thwar PK Chen Z Alfano K Yim MB Krishnan M Fuller AO Larson RG Burke DT Burns MA 《Lab on a chip》2005,5(10):1024-1032
An integrated microfluidic device capable of performing a variety of genetic assays has been developed as a step towards building systems for widespread dissemination. The device integrates fluidic and thermal components such as heaters, temperature sensors, and addressable valves to control two nanoliter reactors in series followed by an electrophoretic separation. This combination of components is suitable for a variety of genetic analyses. As an example, we have successfully identified sequence-specific hemagglutinin A subtype for the A/LA/1/87 strain of influenza virus. The device uses a compact design and mass production technologies, making it an attractive platform for a variety of widely disseminated applications. 相似文献
8.
9.
D P Egolf B T Haley V D Larson 《The Journal of the Acoustical Society of America》1986,79(5):1592-1602
In the literature there are several references which imply that various parts of a hearing aid are sources of constant volume velocity. Reported herein are the findings of an investigation of the validity of such statements. A computer scheme, referenced elsewhere, for modeling in situ hearing aids was utilized to test the constant-volume-velocity hypothesis. In particular, capabilities of the receiver, ear hook, and earmold tip to deliver constant volume velocity were investigated via a computer. To facilitate such an investigation, a universal receiver/earmold model was created. This model was broken down into "source" and "load"at three locations: the receive output, output of the ear hook, and medial tip of the earmold. At each location comparisons were made between computed values of source and load impedance. The constant-volume-velocity hypothesis was assumed to be valid for those cases where source impedance was much, much greater than load impedance. Plots of such impedances show that, for the cases investigated, this rarely occurred, except over certain frequency bands. With the exception of in-the-ear hearing aids, these results appear to contradict inferences made in the literature about the constant-volume-velocity nature of hearing aids. 相似文献
10.
Òscar Rubio-Pons Boris Minaev Oleksandr Loboda Hans Ågren 《Theoretical chemistry accounts》2005,113(1):15-27
The phosphorescence spectrum of p-dichlorobenzene has been calculated using multiconfiguration self-consistent-field wave functions and the quadratic response technique. Attention has been paid to the intensity distribution of the singlet–triplet (3B1u1Ag) transition through a number of vibronic subbands. The second order spin–orbit coupling (SOC) contribution to the spin splitting of the 3B1u (3*) state is found to be almost negligible, and the calculations therefore provide a good estimate for the zero-field splitting (ZFS) parameters based only on the electron spin–spin coupling expectation values. Nuclear quadrupole resonance constants for the different Cl isotopes are also calculated to accomplish the ZFS assignment. The electric dipole activity of the spin sublevels in the triplet–singlet transitions to the ground-state vibrational levels is estimated by calculations of derivatives using distorted geometries which are shifted from the equilibrium position along different vibrational modes. A vibrational analysis of the phosphorescence spectrum, based on the SOC-induced mixing of the singlet and triplet states calculated along different vibrational modes, provides reasonable agreement with experimental data.Acknowledgment O. R.-P. would like to thank the European MOLPROP network for support. The authors thank Alexander Baev for fruitful discussions. This work was supported by the Swedish Royal Academy of Science (KVA). 相似文献