全文获取类型
收费全文 | 1723篇 |
免费 | 41篇 |
国内免费 | 17篇 |
专业分类
化学 | 1377篇 |
晶体学 | 20篇 |
力学 | 20篇 |
数学 | 89篇 |
物理学 | 275篇 |
出版年
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 31篇 |
2015年 | 26篇 |
2014年 | 17篇 |
2013年 | 66篇 |
2012年 | 59篇 |
2011年 | 80篇 |
2010年 | 41篇 |
2009年 | 38篇 |
2008年 | 79篇 |
2007年 | 89篇 |
2006年 | 66篇 |
2005年 | 79篇 |
2004年 | 95篇 |
2003年 | 79篇 |
2002年 | 91篇 |
2001年 | 52篇 |
2000年 | 37篇 |
1999年 | 31篇 |
1998年 | 24篇 |
1997年 | 18篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 14篇 |
1993年 | 19篇 |
1992年 | 30篇 |
1991年 | 26篇 |
1990年 | 26篇 |
1989年 | 24篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 28篇 |
1985年 | 31篇 |
1984年 | 31篇 |
1983年 | 19篇 |
1982年 | 34篇 |
1981年 | 31篇 |
1980年 | 28篇 |
1979年 | 28篇 |
1978年 | 28篇 |
1977年 | 25篇 |
1976年 | 9篇 |
1975年 | 15篇 |
1974年 | 21篇 |
1973年 | 16篇 |
1972年 | 13篇 |
1968年 | 9篇 |
排序方式: 共有1781条查询结果,搜索用时 15 毫秒
151.
Suzuki T Arai K Goto H Hanano M Watanabe J Tomono K 《Chemical & pharmaceutical bulletin》2002,50(6):741-743
Nifedipine-containing calcium phosphate cement (CPC) was prepared, and nifedipine (NF) release from this preparation was evaluated by the shaking method (SK), Japanese Pharmacopoeia XIV (JPXIV) paddle method (PD), and JPXIV flow-through cell method (FT). The release of NF from the CPC preparation continued for 7 d or longer by all these methods. This suggests that the release of NF can be controlled by preparing NF-containing CPC. The release pattern of NF from CPC in these tests was found to follow the Higuchi equation. However, the Higuchi constant differed among the three dissolution tests, probably because the apparent tortuosity of capillary system (tau) varied. 相似文献
152.
Periodic mesoporous benzene-silicas with large pores of 6.0 to 7.4 nm in diameter are synthesized using triblock copolymer as a template. These mesoporous materials have a well-defined hexagonal rod morphology and high thermal stability up to 823 K in air. 相似文献
153.
Mitsuda A Goto T Yoshimura K Zhang W Sato N Kosuge K Wada H 《Physical review letters》2002,88(13):137204
We investigated the magnetization of Yb0.8Y0.2InCu4 as a function of temperature down to 0.6 K, pressure up to 1.2 GPa, and magnetic field up to 9 T. The valence transition temperature of Yb0.8Y0.2InCu4 is lowered with applying pressure. At 0.8 GPa, collapse of the valence transition and ferromagnetic ordering occur almost simultaneously. The ferromagnetic phase at 1.2 GPa is characterized by a low Curie temperature of 1.7 K and an extremely small ordered moment of 0.05 micro(B) per Yb. Some effect of screening the ordered moment may play a key role in the ferromagnetism and the valence transition. 相似文献
154.
Hashi K Shimizu T Goto A Kiyoshi T Matsumoto S Wada H Fujito T Hasegawa K Yoshikawa M Miki T Ito S Hamada M Hayashi S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,156(2):318-321
We have developed a 920-MHz NMR system and performed the proton NMR measurement of H(2)O and ethylbenzene using the superconducting magnet operating at 21.6 T (920 MHz for proton), which is the highest field produced by a superconducting NMR magnet in the persistent mode. From the NMR measurements, it is verified that both homogeneity and stability of the magnet have a specification sufficient for a high resolution NMR. 相似文献
155.
Andrzej Skowronski Kunio Yamagata 《Transactions of the American Mathematical Society》1999,351(2):715-734
In the representation theory of selfinjective artin algebras an important role is played by selfinjective algebras of the form where is the repetitive algebra of an artin algebra and is an admissible group of automorphisms of . If is of finite global dimension, then the stable module category of finitely generated -modules is equivalent to the derived category of bounded complexes of finitely generated -modules. For a selfinjective artin algebra , an ideal and , we establish a criterion for to admit a Galois covering with an infinite cyclic Galois group . As an application we prove that all selfinjective artin algebras whose Auslander-Reiten quiver has a non-periodic generalized standard translation subquiver closed under successors in are socle equivalent to the algebras , where is a representation-infinite tilted algebra and is an infinite cyclic group of automorphisms of .
156.
Kunio Yasue 《Journal of Functional Analysis》1983,51(2):133-141
Motivated from Arnold's variational characterization of the Euler equation in terms of geodesic families of diffeomorphisms, a variational principle for the motion of incompressible viscous fluids is presented. A volume preserving diffusion process with drift velocity field subject to the Navier-Stokes equation is shown to extremize the energy functional of the fluid under a certain class of stochastic variations. 相似文献
157.
158.
Acyclic asymmetric induction was achieved in >99 % formation via coordinated intermediate () in the heteroconjugate addition ( to ); the heteroatom in the adduct being used for elongation of the carbon chain toward maytansine ). 相似文献
159.
Syntheses are described for the “slow reacting substances” 11--leukotriene C (3) (previously known as leukotriene C-2) and leukotriene D (4), the cys-gly analog of leukotriene C (2). The synthesized leukotrienes 3 and 4 were instrumental in the assignment of structure to these members of the family of naturally occuring slow reacting substances which includes also 2. 相似文献
160.
The contribution of backscattered electrons (BE) to Auger electrons (AE) and secondary electrons (SE) was studied by depositing Be onto a polycrystalline or deposited Cu substrate. The effects of backscattering on SE and maximum escape depth of SE were obtained by using the so called δ-η method. This method was also applied to the AE and the effects of BE on AE were experimentally evaluated. The AE yield versus primary energy curve which was corrected for BE was compared with other experiments and theories and considerably good agreement was obtained. From this analysis, the excitation efficiencies of AE by primary electrons and by BE could also be obtained. The absolute AE yield of Be (KVV) was estimated by “area” measurements. The changes of plasma losses, the elastic peaks, the energy distribution of BE, and the true SE were also observed as a function of deposited film thickness, and the results are discussed. 相似文献