全文获取类型
收费全文 | 4036篇 |
免费 | 92篇 |
国内免费 | 21篇 |
专业分类
化学 | 2835篇 |
晶体学 | 42篇 |
力学 | 48篇 |
数学 | 182篇 |
物理学 | 1042篇 |
出版年
2023年 | 16篇 |
2021年 | 34篇 |
2020年 | 48篇 |
2019年 | 56篇 |
2018年 | 40篇 |
2017年 | 21篇 |
2016年 | 56篇 |
2015年 | 68篇 |
2014年 | 65篇 |
2013年 | 166篇 |
2012年 | 175篇 |
2011年 | 235篇 |
2010年 | 107篇 |
2009年 | 141篇 |
2008年 | 210篇 |
2007年 | 222篇 |
2006年 | 232篇 |
2005年 | 181篇 |
2004年 | 179篇 |
2003年 | 158篇 |
2002年 | 179篇 |
2001年 | 131篇 |
2000年 | 107篇 |
1999年 | 71篇 |
1998年 | 51篇 |
1997年 | 58篇 |
1996年 | 52篇 |
1995年 | 42篇 |
1994年 | 53篇 |
1993年 | 63篇 |
1992年 | 75篇 |
1991年 | 58篇 |
1990年 | 51篇 |
1989年 | 57篇 |
1988年 | 47篇 |
1987年 | 56篇 |
1986年 | 48篇 |
1985年 | 55篇 |
1984年 | 53篇 |
1983年 | 40篇 |
1982年 | 27篇 |
1981年 | 41篇 |
1980年 | 30篇 |
1979年 | 48篇 |
1978年 | 40篇 |
1977年 | 25篇 |
1976年 | 31篇 |
1975年 | 24篇 |
1974年 | 28篇 |
1973年 | 21篇 |
排序方式: 共有4149条查询结果,搜索用时 15 毫秒
11.
Yumi ShimadaMakoto Nakamura Toshimasa SuzukaJunji Matsui Ryo TatsumiKen Tsutsumi Tsumoru MorimotoHideo Kurosawa Kiyomi Kakiuchi 《Tetrahedron letters》2003,44(7):1401-1403
A new method for the construction of the AB-ring core of Taxol was developed utilizing a new skeletal transformation protocol as a pivotal step. The acid-catalyzed rearrangement of the cyclopentenone-allene photoadduct gave a bridged seven-membered ketone, which was easily transformed, using the intramolecular Suzuki reaction and the oxidative cleavage of the vicinal diol, to the bicyclic diketone. 相似文献
12.
Jin Cheng Ching-Lung Lin Gen Nakamura 《Proceedings of the American Mathematical Society》2005,133(8):2359-2367
In this paper we prove the following kind of unique continuation property. That is, the zero on each geodesic of the solution in a real analytic hypersurface for second order anisotropic hyperbolic systems with real analytic coefficients can be continued along this curve.
13.
14.
Isao Tanikawa Nobuo Hirakawa Hiroko Hosono Hiroshi Nakamura 《Analytical sciences》2007,23(11):1267-1274
Hydro-membrane gas chromatography (HMGC) is achieved by the annular condensation of water in a capillary column at less than 70 degrees C. The annular membrane of water is formed as a result of the wettability of the stationary phase, which is induced at a water contact angle ranging from 75 degrees to 79 degrees, as derived from a solubility parameter (delta) range of 15.7 +/- 0.3 MPa(1/2) of the coated resin. The range of the liquid to gas volume ratio (beta) required to support the annular membrane should be kept between 0.00005 and 0.0003. In the case of a 0.25-mm i.d. column, the ratio can be set by the combination of a 0.1 to 0.2 microl min(-1) water supply rate and helium gas flow rate. Separation by HMGC develops not only a gas-solid partition but also a focusing effect on the water membrane. One feature of HMGC is that it gives a non-adsorption chromatogram based on the blocking effect of pre-adsorbed water; furthermore, despite the presence of a relatively large quantity of water, the electron impact ionization efficiency is kept the same as in the usual GC/MS condition. The detection limit with the injection of 1 microl of aquatic solution was estimated to be less than 0.1 ppb of low-molecular-weight fatty acids with s/n = 5 on a mass chromatogram at m/z 45. The HMGC/EI-MS system can be applied to the trace analysis of C1 to C3 volatile acids, volatile inorganic acids, and halogenated organic acids in water. 相似文献
15.
Takashi Nakamura 《Journal of Number Theory》2007,123(1):1-9
In this paper, we define λ-joint, a′-joint, (λ,λ)-joint, (λ,a′)-joint and (a′,a′)-joint t-universality of Lerch zeta functions and consider the relations among those. Next we show the existence of (λ,λ)-joint t-universality. Finally, we also show the existence of λ-joint, a′-joint, (λ,a′)-joint and (a′,a′)-joint t-universality by using inversion formulas. 相似文献
16.
17.
M. Wada Y. Ishida T. Nakamura Y. Kanai T. M. Kojima A. Takamine Y. Yamazaki K. Okada A. Yoshida T. Kubo I. Katayama S. Ohtani V. Varentsov H. Wollnik V. Lioubimov H. A. Schuessler 《Hyperfine Interactions》2006,173(1-3):153-163
A next-generation slow radioactive nuclear ion beam facility (SLOWRI) which provides slow, high-purity and small emittance ion beams of all elements is being build as one of the principal facilities at the RIKEN RI-beam factory (RIBF). High energy radioactive ion beams from the projectile fragment separator BigRIPS are thermalized in a large gas catcher cell. The thermalized ions in the gas cell are guided and extracted to a vacuum environment by a combination of dc electric fields and inhomogeneous rf fields (rf carpet ion guide). From there the slow ion beam is delivered via a mass separator and a switchyard to various devices: such as an ion trap, a collinear fast beam apparatus, and a multi-reflection time of flight mass spectrometer. In the R&D works at the present RIKEN facility, an overall efficiency of 5% for a 100A MeV 8Li ion beam from the present projectile fragment separator RIPS was achieved and the dependence of the efficiency on the ion beam intensity was investigated. Recently our first spectroscopy experiment at the prototype SLOWI was performed on Be isotopes. Energetic ions of 10Be and 7Be from the RIPS were trapped and laser cooled in a linear rf trap and the specific mass shifts of these isotopes were measured for the first time. 相似文献
18.
A side-chain liquid crystalline polysiloxane derivative possessing mesogens was synthesized. The mesogens included a large dielectrically-anisotropic moiety. Phase transition behaviour was investigated and the electrorheological (ER) effect of the polymer considered. No ER effect was observed in non-sheared polysiloxane derivative because of its high inherent viscosity. However, a large ER effect was observed after pre-shearing. Pre-shearing, i.e. shearing with a high shear rate before the measurements, arranges the terminal mesogens in the shearing direction. Furthermore, a dilution of the sample led to a larger ER effect exceeding 10 000 Pa. We thus were able to demonstrate a new approach for the appearance of the ER effect. 相似文献
19.
20.
Midori Kobayashi Hitoshi Awoki Yoshimi Nakazaki Gisaku Nakamura 《Graphs and Combinatorics》1989,5(1):243-244
In this paper, a perfect one-factorization ofK
36 is given, which is factor-1-rotational. 相似文献