全文获取类型
收费全文 | 17469篇 |
免费 | 425篇 |
国内免费 | 14篇 |
专业分类
化学 | 8791篇 |
晶体学 | 210篇 |
力学 | 365篇 |
综合类 | 1篇 |
数学 | 3805篇 |
物理学 | 4736篇 |
出版年
2021年 | 210篇 |
2020年 | 235篇 |
2019年 | 230篇 |
2018年 | 339篇 |
2017年 | 365篇 |
2016年 | 676篇 |
2015年 | 530篇 |
2014年 | 594篇 |
2013年 | 1273篇 |
2012年 | 854篇 |
2011年 | 1042篇 |
2010年 | 698篇 |
2009年 | 628篇 |
2008年 | 587篇 |
2007年 | 522篇 |
2006年 | 390篇 |
2005年 | 261篇 |
2004年 | 291篇 |
2003年 | 293篇 |
2002年 | 305篇 |
2001年 | 245篇 |
2000年 | 256篇 |
1999年 | 240篇 |
1998年 | 211篇 |
1997年 | 216篇 |
1996年 | 217篇 |
1995年 | 187篇 |
1994年 | 185篇 |
1993年 | 185篇 |
1992年 | 200篇 |
1991年 | 163篇 |
1990年 | 179篇 |
1989年 | 161篇 |
1988年 | 158篇 |
1987年 | 162篇 |
1986年 | 143篇 |
1985年 | 205篇 |
1984年 | 210篇 |
1983年 | 164篇 |
1982年 | 192篇 |
1981年 | 173篇 |
1980年 | 177篇 |
1979年 | 189篇 |
1978年 | 179篇 |
1977年 | 174篇 |
1976年 | 182篇 |
1975年 | 168篇 |
1974年 | 174篇 |
1973年 | 149篇 |
1968年 | 135篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
A. Račkauskas 《Acta Appl Math》1995,38(1):109-129
Let(X
i
) be a martingale difference sequence. LetY be a standard normal random variable. We investigate the rate of uniform convergence
相似文献
42.
A. Laurinavi?ius K. Rep?as A. -R. Va?kevi?ius 《International Journal of Infrared and Millimeter Waves》1995,16(7):1217-1222
Power-voltage and frequency characteristics of power heads for 90–120 GHz TE10-mode millimeter waves are presented. Operation of the power heads is based on thermo-e.m.f. of hot charge carriers in silicon. The head has been tested both in the pulsed and continuous generation regime. The experiments were carried out in the power range of 2·10–3–4 W. In the pulse regime, the shortest pulse duration was 1s. 相似文献
43.
The radionuclides54Mn,60Co,90Sr,95Nb,95Zr,103Ru,106Ru,125Sb,131I,134Cs,137Cs,140Ba,144Ce,226Ra and228Ac have been studied in the Sava River environment since the Chernobyl accident in 1986. The measured periphyton concentration ratios (CR) for each radionuclide were correlated with the measured sediment distribution coefficients (Kd) for that radionuclide. The Kd-CR relationships obtained were defined by the equation ln Kd=–0.5 ln CR +7.4. These Kd-CR relationships were assumed to be referable to the Sava River ecosystem and were used to predict the missing soil Kd values and/or the missing CR values for the wide range of radionuclides, respectively. Moreover, the Kd-CR relationship characteristic for the Sava River ecosystem was compared with the Kd-CR relationship proposed by Baes1 and by Shepard2. The characterization of the partition coefficients in the Sava River environment and understanding of the mechanisms affecting radionuclide retardation and bioaccumulation are required for the planning of radioactive waste depositories in the area. 相似文献
44.
Individual extraction constants of some dicarbollylcobaltate anions in the water-nitrobenzene system
E. Makrlík J. Rais K. Baše J. Plešek P. Vaňura 《Journal of Radioanalytical and Nuclear Chemistry》1995,198(2):359-365
Individual extraction constants of nine dicarbollylcobaltate anions in the two-phase water-nitrobenzene system were determined radiometrically assuming that the changes of Gibbs energy of the transfer of the tetraphenylarsonium cation, Ph4As+, and of the tetraphenylborate anion, BPh
4
–
, from the aqueous into the nitrobenzene phase are equal. The constants obtained by this method were correlated with Hansch's constants of hydrophobity. 相似文献
45.
We give a necessary and sufficient condition for a Bell-type inequality to hold in a horizontal sum of finitely many finite Boolean algebras. 相似文献
46.
In the framework of noncommutative geometry we describe spinor fields with nonvanishing winding number on a truncated (fuzzy) sphere. The corresponding field theory actions conserve all basic symmetries of the standard commutative version (space isometries and global chiral symmetry), but due to the noncommutativity of the space the fields are regularized and they contain only a finite number of modes.Part of the Project P8916-PHY of the Fonds zur Förderung der wissenschaftlichen Forschung in Österreich. 相似文献
47.
Precise values of energies and widths of low-lying resonances in some rare-gas atom systems (Ar-Ar, Ne-Kr, Ne-Xe) are reported. 相似文献
48.
A. Brablec J. Janča V. Kapička D. Trunec Yu. Chutov V. Pikozh 《Czechoslovak Journal of Physics》1996,46(6):587-594
An expansion of finite plasma clots into the background neutral gas is studied numerically. The presented model includes the quasineutrality violation as well as the interpenetration of plasma and neutral gas at the boundary of the plasma. We estimate the region of plasma parameters where the model is correct. Space distributions of main plasma parameters, cooling of electrons and the process of inter-penetration of the plasma and the neutral gas are analysed as well as an empiric formula for electron temperature is found. Finally, it is shown that the most intensive plasma-gas inter-penetration occurs in the case where the initial plasma and gas densities are the same. 相似文献
49.
J. L. Vučina 《Journal of Radioanalytical and Nuclear Chemistry》1996,214(1):29-39
The effect of the preparation conditions on the in vitro stability of99mTc (Sn)-pyrophosphate kit solution has been examined. To extend the shelf-life of the preparation, different methods of protection were tested. Nitrogen purging stabilizes the kit for at least 6 h after labeling when the content of99mTc-pertechnetate raises to about 5%. However, this method is ineffective in the presence of hydrogen peroxide. The protecting ability of two chemicals was also determined. Gentisic acid gave good results. In the presence of 50 g of gentisic acid per ml of the kit the content of pertechnetate was 1–2% throughout the examined time interval. To eliminate the influence of hydrogen peroxide (6 g per ml of the kit) about 100 g of gentisic acid is needed. N, N-diphenyl-p-phenylenediamine (DPPD) performs some protecting effect only when used in the samples protected by nitrogen purging. However its protecting ability is lower that in the case of gentisic acid. 相似文献
50.
Zusammenfassung Die schon früher beschriebene gasvolumetrische Methode zur N-N-Gruppenbestimmung durch Oxydationsaufschluß mit Chromsäure wurde zur Bestimmung des heterocyklischen Stickstoffes in Indazolinonderivaten mit Erfolg benützt und dadurch weiter die allgemeine Anwendbarkeit der Methode bestätigt. Enthält die Substanz gleichzeitig Amino- oder Nitrogruppen, können diese aus derselben Einwaage als Ammoniak bzw. Salpetersäure bestimmt werden.
Analytical aspects of the oxidation of organic nitrogen compounds with chromic acid Summary The gas volumetric method for determining N-N groups by oxidative fusion with chromic acid (which has already been described previously) was successfully employed to determine the heterocyclic nitrogen in indazolinone derivatives. The general applicability of the method was thereby confirmed. If the substance contains amino or nitro groups at the same time, these can be determined in the same sample as ammonia or nitric acid. XXVII. Mitteilung, siehe1. 相似文献 |