全文获取类型
收费全文 | 940篇 |
免费 | 43篇 |
国内免费 | 2篇 |
专业分类
化学 | 566篇 |
晶体学 | 11篇 |
力学 | 44篇 |
数学 | 60篇 |
物理学 | 304篇 |
出版年
2023年 | 10篇 |
2022年 | 6篇 |
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 36篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 53篇 |
2012年 | 45篇 |
2011年 | 49篇 |
2010年 | 27篇 |
2009年 | 26篇 |
2008年 | 47篇 |
2007年 | 37篇 |
2006年 | 41篇 |
2005年 | 35篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 17篇 |
2001年 | 21篇 |
2000年 | 24篇 |
1999年 | 17篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 18篇 |
1995年 | 18篇 |
1994年 | 9篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 21篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1978年 | 16篇 |
1977年 | 12篇 |
1976年 | 13篇 |
1975年 | 5篇 |
1972年 | 5篇 |
排序方式: 共有985条查询结果,搜索用时 15 毫秒
101.
It is demonstrated that a generalized version of the orthogonal gradient method of orbital optimization may sometimes encounter
a specific divergence problem which may be termed intrinsic to the first order method. Instead of switching over to a more
sophisticated second order method one can cure the divergence problem at the first order level itself by suitably tailoring
the MC-SCF operator or the MC-SCF energy matrix. Results of complete geometry optimization of propynal inl,3nπ* and3ππ* states (pathological cases) are reported to demonstrate the usefulness of the method at an INDO-MCSCF level of approximation.
The results of structure calculations are further rationalized from generalized quantum chemical bond order indices. 相似文献
102.
103.
The effect of replacing the hydrogen atoms in thioformaldehyde by halogen atoms (F, Cl) on the ionisation potential of the
non-bonding electron is analysed by using the Hellman-Feynman theorem, regarding the nuclear charge of the substituent as
a parameter in the many-electron Hamiltonian. The trends predicted by our theory nicely agree with the relevant ionisation
potentials computed either by applying Koopmans’ theorem or by the ΔE
SCF method. For the carbonyls, avaible experimental data indicate the reliability of our prediction. 相似文献
104.
105.
S. Bhattacharyya 《Il Nuovo Cimento C》1988,11(4):443-446
Summary The very recent measurements on the ratio of cosmic antiproton to proton have contradicted seriously the previous measurements
of the same for low-energy antiprotons. The controversial situation has been described and its implication for the validity
of the postulate about the existence of antigalaxy has been examined. Although a very decisive conclusion cannot yet be made,
a two-component behaviour of the ratio cannot, however, be excluded. Moreover, this two-component proposition seems to have
better prospectsvis-a-vis the high-energy measurements of the ratio. 相似文献
106.
Summary Bjorken predicted in the recent past about the large excess emission of photons in high-energy collisions and this was subsequently
corroborated by some experimentalists as well. Obviously, this phenomenon is just opposite in nature to pro-centauro events
marked by the production of photonless hadrons. In this note we will try to trace the outlines of this confusing and contradictory
situation, probe quantitatively into this excess emission of photons (called progammaisation events) and compare them mainly
with Bjorken's disoriented-chiral-condensate (DCC) model. 相似文献
107.
Kinetic investigations on the reaction between U(IV) and H2O2 have been carried out at different acidities in chloride medium at an ionic strength of 2M. The observed bimolecular rate constant has been found to be dependant on [H+]?1.3. The activation energy of the overall reaction has been found to vary from 13.4 ± 0.7 to 18.0 ± 0.8 kcal/mol in the range of acidity from 0.3 to 1.5M. The results have been explained on the basis of three parallel rate-controlling reactions involving unhydrolyzed species of U(IV) and hydrolyzed species UCl(OH)2+ and UO2+. The values of the rate constants for these three reaction paths have been found to be of the order of 3.95, 5.59 × 103, and 1.49 × 105M?1 min?1, respectively. 相似文献
108.
D. P. Bhattacharyya 《Zeitschrift für Physik A Hadrons and Nuclei》1970,234(1):17-22
The vertical momentum spectrum of cosmic-ray muons has been determined by a counter controlled neon-hodoscope in the spectral region (0.2–3) Bev/c at geomagnetic latitude 12 °N. The observed spectrum agrees satisfactorily with the calculated spectrum of Olbert for muon momentum above 1.8 Bev/c. Below about 1.8 Bev/c, the measured spectrum exceeds slightly the theoretical spectrum of Olbert, calculated for the same geomagnetic latitude. The measured spectrum agrees with the experimental spectrum of Allkofer at 9 °N, but is somewhat below the spectrum obtained by Hayman in the low momentum region at 57.5 °N. This shows that there exists a latitude dependence of the low momentum muon spectrum. The estimated integral intensity of muon of momentum ≧320 Mev/c is found to be 7.3×10?3 cm?2 sec?1 str?1 which agrees with the value of other investigators1–9. 相似文献
109.
Reduction and reductive alkylation of the tricyclic α,β-unsaturated ketones 9–12 afforded the saturated ketones 13–21 in high yields. 相似文献
110.
Adenine has been used as the template for the directed synthesis of 5-substituted imidazoles. A Novel intermediate involved in the cyclic operation has been characterised. 相似文献