全文获取类型
收费全文 | 2080篇 |
免费 | 60篇 |
专业分类
化学 | 1165篇 |
晶体学 | 39篇 |
力学 | 72篇 |
数学 | 123篇 |
物理学 | 741篇 |
出版年
2023年 | 12篇 |
2022年 | 33篇 |
2021年 | 28篇 |
2020年 | 41篇 |
2019年 | 36篇 |
2018年 | 43篇 |
2017年 | 34篇 |
2016年 | 79篇 |
2015年 | 44篇 |
2014年 | 63篇 |
2013年 | 129篇 |
2012年 | 142篇 |
2011年 | 141篇 |
2010年 | 87篇 |
2009年 | 72篇 |
2008年 | 119篇 |
2007年 | 101篇 |
2006年 | 91篇 |
2005年 | 104篇 |
2004年 | 74篇 |
2003年 | 48篇 |
2002年 | 44篇 |
2001年 | 38篇 |
2000年 | 23篇 |
1999年 | 18篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 25篇 |
1995年 | 31篇 |
1994年 | 20篇 |
1993年 | 32篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1989年 | 18篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 35篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 27篇 |
1981年 | 25篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1975年 | 9篇 |
1974年 | 14篇 |
1973年 | 10篇 |
1955年 | 12篇 |
排序方式: 共有2140条查询结果,搜索用时 15 毫秒
91.
Bharati Banerjee D.K. Sinha 《International Journal of Mathematical Education in Science & Technology》2013,44(3):261-265
This paper, after analysing the meaning of ‘applied mathematics’, seeks to explore and set forth some broad outlines of the pedagogical implications of studies in the application of mathematics. 相似文献
92.
93.
Kumar Umesh Santu Kaity Banerjee Aparna Arya A. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(9):3505-3516
Journal of Radioanalytical and Nuclear Chemistry - Literature studies reveal apaucity of data on the Th-Zr system. Investigations on the Th-30Zr alloy and its synthesis, microstructure and... 相似文献
94.
Saikat Banerjee Waqas Rasheed Ruixi Fan Dr. Apparao Draksharapu Dr. Williamson N. Oloo Prof. Dr. Yisong Guo Prof. Dr. Lawrence Que Jr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9608-9613
The [FeIV(O)(Me3NTB)]2+ (Me3NTB=tris[(1-methyl-benzimidazol-2-yl)methyl]amine) complex 1 has been shown by Mössbauer spectroscopy to have an S=1 ground state at 4 K, but is proposed to become an S=2 trigonal-bipyramidal species at higher temperatures based on a DFT model to rationalize its very high C−H bond-cleavage reactivity. In this work, 1H NMR spectroscopy was used to determine that 1 does not have C3-symmetry in solution and is not an S=2 species. Our results show that 1 is unique among nonheme FeIV=O complexes in retaining its S=1 spin state and high reactivity at 193 K, providing evidence that S=1 FeIV=O complexes can be as reactive as their S=2 counterparts. This result emphasizes the need to identify factors besides the ground spin state of the FeIV=O center to rationalize nonheme oxoiron(IV) reactivity. 相似文献
95.
A simple, efficient, and facile heterogeneous multi-walled carbon nanotubes-zirconia nanocomposite (MWCNTs-ZrO2) has been synthesized using natural feedstock coconut juice (água-de-coco do Ceará). The synthesized catalyst was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy analysis. The heterogeneous nanocomposite has been used for one-pot synthesis of various N-heterocyclic compounds like pyrazoles, 1,2-disubstituted benzimidazoles, 2-arylbenzazoles, and 2,3-dihydroquinazolin-4(1H)-ones under green reaction medium at room temperature. This novel method has several advantages, such as short reaction time, simple work-up, excellent yield, and green reaction conditions. The catalyst was recycled up to four times without significant loss in catalytic activity. 相似文献
96.
Archiv der Mathematik - In this article, we show that the homotopy invariance of K-theory holds for rings of weak global dimension at most one. Prüfer domains are examples of such rings. We... 相似文献
97.
We seek to develop network algorithms for function computation in sensor networks. Specifically, we want dynamic joint aggregation, routing, and scheduling algorithms that have analytically provable performance benefits due to in-network computation as compared to simple data forwarding. To this end, we define a class of functions, the Fully-Multiplexible functions, which includes several functions such as parity, MAX, and kth-order statistics. For such functions we characterize the maximum achievable refresh rate of the network in terms of an underlying graph primitive, the min-mincut. In acyclic wireline networks we show that the maximum refresh rate is achievable by a simple algorithm that is dynamic, distributed, and only dependent on local information. In the case of wireless networks we provide a MaxWeight-like algorithm with dynamic flow-splitting, which is shown to be throughput-optimal. 相似文献
98.
99.
A new AB type of monomer 4′-fluoro-3,5-dimethyl-3′-trifluoromethyl-biphenyl-4-ol has been synthesized that leads to a new poly(arylene ether) by self polycondensation reaction. The monomer and the polymer have been well characterized by elemental analyses, FT-IR and NMR spectroscopy. Both FT-IR and NMR spectra of the polymers did not show any terminal phenoxy group indicating high conversion. The polymer showed glass transition at 278°C and very good thermal stability in synthetic air. GPC results indicate high molar mass development; Mw = 53200 and MWD = 2.29. 相似文献
100.
Kinshuk Dasgupta D. Sen T. Mazumdar R. K. Lenka R. Tewari S. Mazumder J. B. Joshi S. Banerjee 《Journal of nanoparticle research》2012,14(3):728
For the first time, bamboo-shaped multiwalled carbon nanotubes, having diameter of the order of 50 nm, have been grown on
carbon black in a fluidized bed in bulk amount. The activation energy for the synthesis of the product was found out to be
around 33 kJ/mol in the temperature range of 700−900 °C. The carbon nanotubes were separated from the carbon black by preferential
oxidation of the later, the temperature of which was determined by thermogravimetry. The transmission electron microscopy
revealed different features of the nanotubes such as “Y” junction, bend, and catalyst filling inside the nanotubes. Small
angle neutron scattering was performed on the nanotubes synthesized at different temperatures. The data were fitted into a
suitable model in order to find out the average diameter, which decreases with increase in synthesis temperature. The Monte
Carlo simulation predicts the same behavior. Based on the above observations, a possible growth mechanism has been predicted.
The oscillation in carbon saturation value inside the catalyst in the fluidized bed has been indicated as the responsible
factor for the bamboo-shaped structure. 相似文献