全文获取类型
收费全文 | 643128篇 |
免费 | 6077篇 |
国内免费 | 1967篇 |
专业分类
化学 | 323388篇 |
晶体学 | 9323篇 |
力学 | 33023篇 |
综合类 | 22篇 |
数学 | 97670篇 |
物理学 | 187746篇 |
出版年
2021年 | 5030篇 |
2020年 | 5412篇 |
2019年 | 6133篇 |
2018年 | 17779篇 |
2017年 | 17479篇 |
2016年 | 17470篇 |
2015年 | 7868篇 |
2014年 | 11592篇 |
2013年 | 26277篇 |
2012年 | 23460篇 |
2011年 | 33858篇 |
2010年 | 22918篇 |
2009年 | 23297篇 |
2008年 | 28641篇 |
2007年 | 30326篇 |
2006年 | 20815篇 |
2005年 | 19615篇 |
2004年 | 18535篇 |
2003年 | 17040篇 |
2002年 | 16089篇 |
2001年 | 17106篇 |
2000年 | 13046篇 |
1999年 | 10127篇 |
1998年 | 8446篇 |
1997年 | 8259篇 |
1996年 | 7984篇 |
1995年 | 7134篇 |
1994年 | 7068篇 |
1993年 | 6830篇 |
1992年 | 7613篇 |
1991年 | 7787篇 |
1990年 | 7419篇 |
1989年 | 7298篇 |
1988年 | 7263篇 |
1987年 | 7132篇 |
1986年 | 6745篇 |
1985年 | 8705篇 |
1984年 | 8907篇 |
1983年 | 7165篇 |
1982年 | 7261篇 |
1981年 | 7184篇 |
1980年 | 6668篇 |
1979年 | 7307篇 |
1978年 | 7437篇 |
1977年 | 7464篇 |
1976年 | 7407篇 |
1975年 | 6834篇 |
1974年 | 6736篇 |
1973年 | 6893篇 |
1972年 | 4989篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
941.
A procedure is described separating, identifying and determining the actinides (An) U, Np, Pu, Am and Cm in the presence of the lanthanides (Ln) La, Ce, Pr, Nd, Pm, Sm, Eu and Ho on an analytical scale. It is based on high-pressure liquid chromatography (HPLC) combined with a dual on-line detection system and is accomplished within a short time, in one step and under isocratic conditions (for An). The separation was carried out on a strongly acidic and highly capacitive cationic exchange resin on a polystyrene divinylbenzene copolymer (Aminex A9, co. BioRad) basis. Radionuclides emitting α- and β-particles are detected on-line using a custom-made solid scintillation flow-through cell. Inactive components are monitored by colour reagent complex detection (Arsenazo III, λ-648 nm) with a VIS detector placed in series. 相似文献
942.
943.
944.
D. T. Satybaldyeva M. Yu. Mukhamedzhanova A. A. Sarymsakov Yu. T. Tashpulatov 《Chemistry of Natural Compounds》1998,34(3):322-325
The results are given of a study of the rheological properties of concentrated solutions of CNC and agar-agar and the influence of their quantitative ratio on the anomalous flow behavior of their solutions. A hypothesis is put forward of the formation of intermolecular associates from CMC and agar-agar which leads to the formation of a stronger structural network of solutions of the initial polysaccharides.Institute of the Physics and Chemistry of Polymers, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 1 44 26 61. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 357–361, May–June, 1998. 相似文献
945.
946.
Based on NMR imaging results of the spatial and temporal development of ion exchange processes in alginate gels, the question of appropriate modelling of these processes is discussed. For rare earth and actinoid ions, the behaviour is found to correspond qualitatively to the expectations of Stefan’s model (shrinking core model, SCM). However, quantitative correspondence of the experimental data with the model can only be achieved when an additional diffusive layer at the surface of the ion exchange material is assumed. An extension of the SCM with respect to this problem is derived. 相似文献
947.
H. Hofsäss H. Feldermann R. Merk M. Sebastian C. Ronning 《Applied Physics A: Materials Science & Processing》1998,66(2):153-181
T /nS of nT rearrangements and nS atoms in the spike volume as the crucial parameter characterizing the ability of a given ion–target combination to achieve
complete rearrangement of the spike volume. nT/nS>1 is the optimum condition for diamondlike film growth. For aC films the ion energy dependence of nT/nS agrees well with the measured sp3 bond fraction. For Ar+-ion-assisted deposition of aC we find nT/nS>1 above 50 eV with no pronounced ion energy dependence. Furthermore, our model predicts optimum conditions for the formation
of cubic boron nitride between 50 eV and 3 keV.
Accepted: 14 October 1997 相似文献
948.
The problem of sand production (dilatant-plastic reservoir fragmentation) in the process of pumping-out fluid through an uncased borehole is considered. Taking the dilatant change in reservoir porosity into account makes it possible to find a relation between the fluid and solid mass flow rates. There is no steady-state solution if the elasto-plastic boundary does not coincide with the supply contour. In this case a self-similar problem of well start-up with a constant production rate is considered. 相似文献
949.
V. V. Dovlatyan É. N. Ambartsumyan G. S. Amazaspyan 《Chemistry of Heterocyclic Compounds》1996,32(1):75-77
New approaches have been developed for the application of cyanamino-sym-triazines in the synthesis of imidazolidinyl-sym-triazines. 相似文献
950.
A. M. Osharin 《Radiophysics and Quantum Electronics》1998,41(4):295-300
Attenuation of millimeter waves in dry snowfalls is numerically simulated with allowance for the actual shape of snowflakes.
It is shown that for moderate-intensity snowfalls the values of attenuation cross-sections averaged over the snowflake orientations
are well approximated by power-law function depending on the equivalent diameter of the snowflakes. This allows us to obtain
an analytical expression for the attenuation coefficient of a plane electromagnetic wave by snowfall for size distributions
of particles of the gamma-distribution type and its modifications.
Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika,
Vol. 41, No. 4, pp. 446–455, April, 1998. 相似文献