全文获取类型
收费全文 | 282845篇 |
免费 | 3110篇 |
国内免费 | 842篇 |
专业分类
化学 | 151903篇 |
晶体学 | 4310篇 |
力学 | 12423篇 |
综合类 | 34篇 |
数学 | 32198篇 |
物理学 | 85929篇 |
出版年
2020年 | 2381篇 |
2019年 | 2594篇 |
2018年 | 3453篇 |
2017年 | 3410篇 |
2016年 | 4988篇 |
2015年 | 3139篇 |
2014年 | 4807篇 |
2013年 | 11641篇 |
2012年 | 9091篇 |
2011年 | 11010篇 |
2010年 | 7790篇 |
2009年 | 7481篇 |
2008年 | 10172篇 |
2007年 | 10290篇 |
2006年 | 9640篇 |
2005年 | 8749篇 |
2004年 | 8015篇 |
2003年 | 7205篇 |
2002年 | 7072篇 |
2001年 | 7586篇 |
2000年 | 5921篇 |
1999年 | 4562篇 |
1998年 | 4009篇 |
1997年 | 3976篇 |
1996年 | 3745篇 |
1995年 | 3444篇 |
1994年 | 3609篇 |
1993年 | 3316篇 |
1992年 | 3794篇 |
1991年 | 3780篇 |
1990年 | 3708篇 |
1989年 | 3571篇 |
1988年 | 3653篇 |
1987年 | 3555篇 |
1986年 | 3363篇 |
1985年 | 4461篇 |
1984年 | 4735篇 |
1983年 | 3939篇 |
1982年 | 4096篇 |
1981年 | 4022篇 |
1980年 | 3977篇 |
1979年 | 3962篇 |
1978年 | 4279篇 |
1977年 | 4176篇 |
1976年 | 4252篇 |
1975年 | 3912篇 |
1974年 | 3952篇 |
1973年 | 4115篇 |
1972年 | 2874篇 |
1971年 | 2405篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The literature published over the period 1986–1990 on the chemical properties (oxidation, addition, substitution, reactions of the functional groups, etc.) of 1,4-dihydropyridines is correlated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, No. 5, pp. 579–612, May, 1993. 相似文献
992.
Investigations to the causes and effects of contaminants at the rf diode deposition of CrSi films in a non-heated high vacuum apparatus were carried out comparing an oxygen-free fusion target with an oxygen-containing cermet target. The films of the fusion target contained considerable amounts of oxygen; analogously the oxygen concentration in the films was increased in the case of the cermet target. Moreover, hydrogen was found. The concentration of the contaminants decreased with the sputtering power, however the rate of incorporation increased. For high sputtering rates the contamination process was reproducible and independent of the plant conditioning; the deposited films were depth-homogeneous. The reasons for this behaviour lie in water sources which are activated first of all by the discharge itself. The electrical properties found are explained by the contaminants and the deposition conditions. 相似文献
993.
994.
G. N. Stratopoulos W. J. Zakrewski 《Zeitschrift fur Physik C Particles and Fields》1993,59(2):307-312
We look at the recently proposed scheme of approximating a sine-Gordon soliton by an expression derived from two dimensional instantons. We point out that the scheme of Sutcliffe in which he uses two dimensional instantons can be generalised to higher dimensions and that these generalisations produce even better approximations than the original approximation. We also comment on generalisations to other models. 相似文献
995.
996.
D. Kast A. Jungclaus K.P. Lieb M. Górska G. de Angelis P.G. Bizzeti A. Dewald C. Fahlander H. Grawe R. Peusquens M. De Poli H. Tiesler 《The European Physical Journal A - Hadrons and Nuclei》1998,3(2):115-128
In the neutron deficient isotopes 104,105In lifetimes of high spin states in the range from 0.5 ps to 600 ps have been measured in a coincidence recoil distance Doppler
shift (RDDS) experiment. By combining the Doppler shift attenuation (DSA) and RDDS methods at few μm flight distances, the
problem of delayed feeding has been avoided and very short lifetimes in the range 0.5–0.8 ps have been determined. Shell model
calculations with strong restrictions for the neutron orbitals reveal good agreement with experimental level energies and
still fair agreement for most measured B(M1) and B(E2) values.
Received: 30 June 1998 相似文献
997.
Polyethyleneimine (PEIM) samples crosslinked by a commercial epoxy resin (Epon 828) were prepared, and their adsorption capacity for acidic gases was studied. The swelling and deswelling characteristics of the crosslinked samples were also examined as part of this program. Reactivation of these adsorbents could be carried out by heat, or by a combination of heat and treatment in dilute alkalies. 相似文献
998.
999.
1000.
G. M. Luke L. P. Le B. J. Sternlieb Y. J. Uemura J. H. Brewer R. Kadono R. F. Kiefl S. R. Kreitzman T. M. Riseman C. E. Stronach M. Davis S. Uchida H. Takagi Y. Tokura Y. Hidaka T. Murakami E. A. Early J. T. Markert M. B. Maple C. L. Seaman 《Hyperfine Interactions》1991,63(1-4):311-317
We report muon spin relaxation/rotation measurements on sintered powder samples of Nd2−x
Ce
x
CuO4−y
and a large single crystal of Nd2CuO4−y
. We find an electronic phase diagram which is quite similar to that of hole-doped superconductors such as La2−x
Sr
x
CuO4−y
, although the doping of electrons into the system is less efficient in destroying the static moments on the copper spins.
Static magnetic order in Nd2CuO4−y
appears below about 250 K, and two spin reorientations are seen atT=75 K andT=35 K. Measurements of the magnetic field penetration depth have been unsuccessful due to the rare-earth paramagnetism of
these materials. 相似文献