全文获取类型
收费全文 | 80935篇 |
免费 | 24329篇 |
国内免费 | 17767篇 |
专业分类
化学 | 51236篇 |
晶体学 | 1040篇 |
力学 | 5425篇 |
综合类 | 80篇 |
数学 | 10493篇 |
物理学 | 54757篇 |
出版年
2024年 | 474篇 |
2023年 | 819篇 |
2022年 | 875篇 |
2021年 | 827篇 |
2020年 | 1110篇 |
2019年 | 1583篇 |
2018年 | 1583篇 |
2017年 | 2167篇 |
2016年 | 2414篇 |
2015年 | 2663篇 |
2014年 | 2556篇 |
2013年 | 4421篇 |
2012年 | 4829篇 |
2011年 | 6389篇 |
2010年 | 9597篇 |
2009年 | 9805篇 |
2008年 | 3661篇 |
2007年 | 3190篇 |
2006年 | 2800篇 |
2005年 | 3126篇 |
2004年 | 3922篇 |
2003年 | 3160篇 |
2002年 | 2983篇 |
2001年 | 3239篇 |
2000年 | 2412篇 |
1999年 | 2648篇 |
1998年 | 2253篇 |
1997年 | 2046篇 |
1996年 | 2374篇 |
1995年 | 2790篇 |
1994年 | 2867篇 |
1993年 | 2914篇 |
1992年 | 2494篇 |
1991年 | 2145篇 |
1990年 | 1782篇 |
1989年 | 1906篇 |
1988年 | 1868篇 |
1987年 | 1158篇 |
1986年 | 1208篇 |
1985年 | 864篇 |
1984年 | 985篇 |
1982年 | 892篇 |
1981年 | 738篇 |
1980年 | 770篇 |
1979年 | 529篇 |
1978年 | 530篇 |
1977年 | 636篇 |
1976年 | 1041篇 |
1973年 | 439篇 |
1972年 | 532篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
31.
32.
33.
S. O. Kolusheva B. A. Salakhutdinov T. F. Aripov L. P. Vernon 《Chemistry of Natural Compounds》1994,29(4):523-525
It has been shown by the ESR of spin probes that thionin initially interacts with with negatively charged membranes electrostatically and then passes into the membranes to a depth comparable with the length of the hydrophobic sections of the protein loops.Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Brigham Young University, Provo, Utah, USA. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 594–597, July–August, 1993. 相似文献
34.
Twelve series of linear oligomers of four different degrees of polymerization (xn = 8.77−41.55), having a common perfluorinated random copolymeric chain as molecular body and two equal foreign end units of one of the types listed in Table 1, have been synthesized by derivatization of base samples of one of them having a diolic---CH2OH functionality. The glass transition temperature Tg of all the series was measured and thus examined as a function of xn. A clear end unit effect is observed, dominantly determined in every series by chemical nature and structure of the end units, quantitatively expressed at any xn by different positive or negative Tg deviations from the common asymptotic Tg∞ value. The results are also discussed in terms of copolymer end effect and of relation between Tg and end copolymeric composition. 相似文献
35.
The properties of a polymer-concrete composed of polyester matrix and locally available rock aggregate are investigated. The formula of the concrete is found by an experimental-calculation approach in such a way as to attain a closer packing of the aggregate particles on the one hand, and to ensure the needed processing characteristics (placeability) of the mix on the other. It is shown experimentally that the material obtained has a rather high compression strength. Under prolonged compression loads, the polymer-concrete exhibits a noticeable creep behavior with a linear relation between the creep strains and stresses. After the action of half the ultimate load over 3000 h, the total strains exceed the instantaneous ones by 2.0 to 2.2 times. The accumulation of irreversible strains is also observed; however, their contribution to the total strain is small. It is found that the stress-strain relation can be represented by the equation of linear hereditary creep theory.Institute of Polymer Mechanics, University of Latvia, Riga, LV-1006, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 147–162, March–April, 1999. 相似文献
36.
37.
To investigate local ordering and segregation phenomenon in a Ni91Pt9-alloy after sputtering and annealing a 3D optical atom probe (OAP) has been used. The specimen tips have been prepared from polycrystalline samples. To sputter the samples a separate preparation chamber with a scannable Ar-sputter-gun is connected to the OAP vessel. When necessary, the sample can be electrically heated to induce segregation and cure the altered layer. After a heat treatment of a Ni91 at. %Pt 9 at.% specimen at 1100 K the surface of a (111)-oriented specimen is enriched in platinum by a factor of two in relation to the bulk. The phenomenon of short-range ordering has been investigated on the surface and in the subsurface volume. A 3D reconstruction of this annealed NiPt specimen shows regions with high concentration of platinum that gives an indication at short-range ordering. Uniform sputtering of the tip without a heat treatment induces a decisive depletion of Pt on the surface and the following subatomic layers. The atom-probe results of specimens in thermal equilibrium are in close agreement to further surface sensitive results obtained from Ion Scattering Spectroscopy (ISS) and Auger Electron Spectroscopy (AES). 相似文献
38.
Ma Jiangle Yang Hong-shen Zhang Zhongxi Lu Zhong-zuo 《International Journal of Infrared and Millimeter Waves》1993,14(5):1069-1076
A simple method is introduced to improve the analysing accuracy of circular groove guide. With this method, the characteristic equation of circular groove guide is derived and its solution is given and discussed.The Project Supported by National Natural Science Foundation of P.R.China 相似文献
39.
40.
采用密度泛函方法(B3P86)对 Fe_2分子结构进行了优化.计算结果中未观察到自旋污染,基态波函数与高态波函数并未混杂,结果表明,Fe_2中有8个未配对电子,这些电子空间分布不同和自旋平行产生的自旋极化效应,使 Fe_2能量最低.计算结果表明,Fe_2分子的基态是~9∑_g~ ,并非~7Δ_u,进而表明 Fe_2的自旋平行效应比电子自旋配对效应要强.计算得到该分子基态的二阶、三阶和四阶力常数分别为1.4115×10~(-2)aJ/nm~2、-37.1751×10~3aJ/nm~3和 98.7596×10~4aJ/nm~4;光谱数据ω_eχ_e、B_e、α_e分别为0.3522、0.0345、 0.4963×10~(-4)cm~(-1);离解能为3.5522eV,平衡键长为0.2137nm,振动频率为292.914cm~(-1);并得到了 Murrel-Sorbie 函数. 相似文献