全文获取类型
收费全文 | 1480篇 |
免费 | 12篇 |
国内免费 | 3篇 |
专业分类
化学 | 979篇 |
晶体学 | 10篇 |
力学 | 31篇 |
数学 | 297篇 |
物理学 | 178篇 |
出版年
2014年 | 13篇 |
2013年 | 26篇 |
2012年 | 35篇 |
2011年 | 37篇 |
2010年 | 30篇 |
2009年 | 23篇 |
2008年 | 39篇 |
2007年 | 34篇 |
2006年 | 34篇 |
2005年 | 41篇 |
2004年 | 28篇 |
2003年 | 31篇 |
2002年 | 31篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 20篇 |
1998年 | 16篇 |
1996年 | 17篇 |
1994年 | 13篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 19篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 15篇 |
1986年 | 26篇 |
1985年 | 19篇 |
1984年 | 28篇 |
1983年 | 22篇 |
1982年 | 34篇 |
1981年 | 37篇 |
1980年 | 22篇 |
1979年 | 29篇 |
1978年 | 16篇 |
1977年 | 18篇 |
1976年 | 21篇 |
1975年 | 22篇 |
1971年 | 14篇 |
1969年 | 13篇 |
1938年 | 15篇 |
1937年 | 17篇 |
1934年 | 21篇 |
1933年 | 19篇 |
1931年 | 24篇 |
1930年 | 19篇 |
1929年 | 20篇 |
1928年 | 29篇 |
1927年 | 18篇 |
1926年 | 19篇 |
排序方式: 共有1495条查询结果,搜索用时 15 毫秒
81.
The relation between sample mass andDSC-amplitude was investigated under various experimental conditions for vitreous quartz, both as discs and powders. Contrary to other authors3 proportionality has been found up to the highest masses (75 mg) used. A statistical analysis of the data indicates that the accuracy of directC p-measurements byDSC can be increased by determining the blank value by extrapolation of the amplitudes for several masses to zero mass instead of using the usual procedure, which involves a run with the empty pans. The overall error ofC p due to instrument errors is estimated not to exceed 2%. 相似文献
82.
83.
84.
Erich Bohl 《Numerische Mathematik》1980,34(2):111-124
Summary The numerical treatment of discrete bifurcation problems (2) with chord methods or Newton's method is a question of constructing appropriate initial approximations to prevent the sequence from converging to the trivial solution. This problem is being discussed under conditions which are satisfied for quite a few examples arising in applications (see Sect. 3). 相似文献
85.
86.
Erich Platte 《Archiv der Mathematik》1978,31(1):143-145
Ohne Zusammenfassung 相似文献
87.
Electrochemical Formation of Δ1,2-Norbornene The electrochemical reduction of 1,2-dihalogen norbornanes in tetrahydrofuran/furan leads to a mixture of two isomeric cycloadducts 6 and 7. The ratio of these adducts corresponds to those which have been found in reductive bisdehalogenation of 1 and 2 by butyllithium. 相似文献
88.
Bicyclo[3.1.0]hexane-2.3.4-trione and its 1.5-dimethyl derivative have been synthesized and investigated by means of photoelectron spectroscopy. 相似文献
89.
Jones DJ Holman KW Notcutt M Ye J Chandalia J Jiang LA Ippen EP Yokoyama H 《Optics letters》2003,28(10):813-815
Using high-bandwidth feedback, we have synchronized the pulse train from a mode-locked semiconductor laser to an external optical atomic clock signal and achieved what is to our knowledge the lowest timing jitter to date (22 fs, integrated from 1 Hz to 100 MHz) for such devices. The performance is limited by the intrinsic noise of the phase detector used for timing-jitter measurement. We expect such a highly stable device to play an important role in fiber-network-based precise time/frequency distribution. 相似文献
90.
Porphycene, an isomer that can replace porphin in chemical and biochemical contexts, is predicted by ab initio calculation to exhibit a global diatropic pi ring current with bifurcation across the four pyrrole units of the macrocycle. Analysis of the orbital contributions to the current density in porphycene reveals that the global current, with its bifurcation feature, is attributable to the four electrons of the near-degenerate HOMO levels, the same set of active electrons that feature in the well-known four-orbital model of the electronic spectra of porphyrins. Integration of the current density gives 1H, 13C and 15N NMR shieldings that are compatible with the observed low-field shifts of peripheral and bridge protons and high-field shift of the internal NH protons, assignment of the 13C NMR spectrum and the single average 15N chemical shift resulting from rapid NH tautomerism. Geometries were calculated with the DFT B3LYP functional, the current density maps were calculated with the ipsocentric coupled-Hartree-Fock CTOCD-DZ method, and the shieldings with the CTOCD-PZ2 variant, all in the same 6-31G** basis. 相似文献