全文获取类型
收费全文 | 763629篇 |
免费 | 40139篇 |
国内免费 | 30732篇 |
专业分类
化学 | 344147篇 |
晶体学 | 10110篇 |
力学 | 34750篇 |
综合类 | 357篇 |
数学 | 82323篇 |
物理学 | 238753篇 |
无线电 | 124060篇 |
出版年
2022年 | 6073篇 |
2021年 | 8312篇 |
2020年 | 9166篇 |
2019年 | 10982篇 |
2018年 | 12864篇 |
2017年 | 13446篇 |
2016年 | 18171篇 |
2015年 | 13480篇 |
2014年 | 18738篇 |
2013年 | 36892篇 |
2012年 | 30555篇 |
2011年 | 35159篇 |
2010年 | 28975篇 |
2009年 | 29944篇 |
2008年 | 31489篇 |
2007年 | 31406篇 |
2006年 | 29504篇 |
2005年 | 26632篇 |
2004年 | 25731篇 |
2003年 | 22737篇 |
2002年 | 22486篇 |
2001年 | 24960篇 |
2000年 | 19803篇 |
1999年 | 16403篇 |
1998年 | 14200篇 |
1997年 | 13545篇 |
1996年 | 13179篇 |
1995年 | 12225篇 |
1994年 | 12192篇 |
1993年 | 12015篇 |
1992年 | 12257篇 |
1991年 | 12116篇 |
1990年 | 11258篇 |
1989年 | 10705篇 |
1988年 | 10139篇 |
1987年 | 8950篇 |
1986年 | 8454篇 |
1985年 | 10297篇 |
1984年 | 10512篇 |
1983年 | 8292篇 |
1982年 | 8710篇 |
1981年 | 8292篇 |
1980年 | 7968篇 |
1979年 | 8196篇 |
1978年 | 8219篇 |
1977年 | 8213篇 |
1976年 | 8439篇 |
1975年 | 7392篇 |
1974年 | 7405篇 |
1973年 | 7544篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
981.
N. L. Dmitruk O. Yu. Borkovskaya R. V. Konakova I. B. Mamontova S. V. Mamykin D. I. Voitsikhovskiy 《Technical Physics》2002,47(6):698-702
The effect of 60Co gamma irradiation at doses of 103-2×105 Gy on the photoconversion and dark I-V characteristics of Au/GaAs surface-barrier solar cells (SCs) is studied. The morphology of the interface microrelief is varied
to reach the highest photoconversion efficiency. Of the two types of microrelief morphology (dendritic and quasi-grating)
obtained by the chemical anisotropic etching of n-(100)GaAs, the latter is more promising, particularly for SCs designed for space application, since the associated SCs offer
higher efficiency and radiation resistance. 相似文献
982.
Sanzharov N. A. Yarovoi A. T. Bekhtereva E. S. Ulenikov O. N. 《Russian Physics Journal》2002,45(10):1024-1031
Analytical formulas are derived that describe the dependences of the transition probabilities in vibrational-rotational spectra of XY3-type molecules with C
3v
symmetry on the rotational quantum numbers. 相似文献
983.
Multi-valued and universal binary neurons (MVN and UBN) are the neural processing elements with the complex-valued weights and high functionality. It is possible to implement an arbitrary mapping described by partially defined multiple-valued function on the single MVN. An arbitrary mapping described by partially defined or fully defined Boolean function, which can be non-threshold, may be implemented on the single UBN. The quickly converging learning algorithms exist for both types of neurons. Such features of the MVN and UBN may be used for solving the different problems. One of the most successful applications of the MVN and UBN is their usage as basic neurons in the Cellular Neural Networks (CNN). It opens the new effective opportunities in nonlinear image filtering and its applications to noise reduction, edge detection and solving of the super resolution problem. A number of experimental results are presented to illustrate the performance of the proposed algorithms.An erratum to this article can be found at 相似文献
984.
Effect of misalignment on electrical characteristics of ACF joints for flip chip on flex applications 总被引:1,自引:0,他引:1
The effect of misalignment on the electrical properties of anisotropic conductive film (ACF) joints is investigated in this work. It is found that along with the increase of misalignment, the connection resistance of ACF joints increases. When the misalignment in x-direction is less than 5 μm, the increase rate of connection resistance is quite large. Then, along with the severity of misalignment, the increase rate becomes smaller. Finally, when the misalignment is close to 20 μm, the increase rate rises again. The Holm's electric contact theory is used for understanding the connection resistance variation. On the other hand, with the increase of misalignment in x-direction, the insulation resistance between ACF joints decreases. If the misalignment exceeded 10 μm, the decrease is prominent for the Ni particle ACF joints. This phenomenon can be explained by the effect of dielectric damage of the epoxy.Computer programs are also developed to calculate the variation of the probability of open and shorting after misalignment and predicate the maximum misalignment tolerance. The results show that the open and shorting probability increase abruptly after misalignment. On the view of pad parameters, the open probability is mainly related to the pad area, while the pads gap is critical to the shorting probability. Large pads gap (small pad width) can reduce the shorting probability obviously. On the other hand, enlarging the pad area by increasing pad length decreases the open probability significantly. So comparing to square shape pad, rectangle shape pad can reduce the failure probability greatly. 相似文献
985.
The circular dichroism (CD) method has been used to study the stereochemistry of the bisbenzyltetrahydroisoquinoline alkaloids. A relationship has been established between the absolute configurations of the asymmetric centers and the parameters of the Cotton effects in the CD spectra. The changes in the CD spectra on protonation have been correlated with conformational rearrangements of the molecules due to the different attachment of the oxygen bridges.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 818–823, November–December, 1979. 相似文献
986.
987.
The interaction between azathioprine (AZ) and bovine serum albumin (BSA) is mainly due to hydrophobic binding according to the dependence of the binding constant on the ionic strength obtained by equilibrium dialysis. The binding constant and partition coefficient of AZ were smaller than those of warfarin, phenylbutazone and ibuprofen. Little variation in the proton chemical shift of AZ was observed whether there was an absence or presence of BSA (7.25 x 10(-5) M). The spin-lattice relaxation time (T1) of AZ decreased in the presence of BSA to 6-22%. The spin-spin relaxation rate (1/T2) of AZ increased 16-24 times for the methyl group and the imidazole ring and 8-13 times for the purine ring in the presence of BSA. The ratio of the spin-spin relaxation rate of the free AZ to the bound AZ ((1/T2)b/(1/T2)f) of the methyl group and the imidazole ring was 2-3 times larger than that of the purine ring. The binding of AZ to BSA was concluded to be mainly at the methyl group on the imidazole ring of AZ. 相似文献
988.
N. Euler W. -H. Steeb L. G. S. Duarte I. C. Moreira 《International Journal of Theoretical Physics》1991,30(9):1267-1271
The techniques of invertible point transformations and the Painlevé analysis can be used to construct integrable ordinary differential equations. We compare both techniques for the second Painlevé transcendent. 相似文献
989.
990.
S. A. Vakulenko 《Journal of Mathematical Sciences》1991,57(3):3093-3096
A generalization of Whitham's asymptotic principle for parabolic equations is stated. An application of this principle to Fisher's one-dimensional nonlinear equation is considered.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova, Vol. 179, pp. 46–51, 1989. 相似文献