全文获取类型
收费全文 | 696篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
化学 | 348篇 |
晶体学 | 2篇 |
力学 | 29篇 |
数学 | 47篇 |
物理学 | 296篇 |
出版年
2023年 | 9篇 |
2022年 | 9篇 |
2021年 | 11篇 |
2020年 | 19篇 |
2019年 | 18篇 |
2018年 | 22篇 |
2017年 | 11篇 |
2016年 | 24篇 |
2015年 | 19篇 |
2014年 | 28篇 |
2013年 | 80篇 |
2012年 | 63篇 |
2011年 | 49篇 |
2010年 | 42篇 |
2009年 | 32篇 |
2008年 | 35篇 |
2007年 | 41篇 |
2006年 | 22篇 |
2005年 | 18篇 |
2004年 | 6篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1963年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有722条查询结果,搜索用时 281 毫秒
61.
Various empirical theories of ultrasonic velocity have been applied to three binary liquid mixtures, under pressures up to
200 MPa and their validity have been tested. A pressure dependent study of ultrasonic velocities has been made at 303.15 K.
The agreement between theory and experiment is found to be quite satisfactory. 相似文献
62.
Akhil Ranjan 《Proceedings Mathematical Sciences》2000,110(1):27-34
In this paper we give a proof of Lichnerowicz conjecture for compact simply connected manifolds which is intrinsic in the
sense that it avoids thenice embeddings into eigenspaces of the Laplacian. Even if one wants to use these embeddings, this paper gives a more streamlined proof.
As a byproduct, we get a simple criterion for a polynomial to be a Jacobi polynomial. 相似文献
63.
A novel tetrafunctional epoxy resin, N,N,N,Nt'-tetraglycidyl-2,2-bis[4-(p-aminophen-oxy)phenyl]propane, has been synthesised. The curing kinetics and thermal stability of the cured product have been investigated using various amine curing-agents. The overall activation energy for the curing reaction is observed to be in the range 30.3–126.2 kJ mol−1. The cured products have good thermal stability. 相似文献
64.
Krishanu Nandy Sayani Chaudhuri Ranjan Ganguly Ishwar K. Puri 《Journal of magnetism and magnetic materials》2008
Magnetic microspheres are used as mobile substrates in micro-total-analysis systems (μTAS), since the particles can be selectively functionalized to attach different bioconjugates and can be precisely manipulated using external magnetic field gradients. A large number of MEMS-based bio-analytical devices employ magnetophoretic separation as an important step during their operation. An analytical technique is proposed in this paper that describes the magnetophoretic transport of magnetic microspheres under an imposed magnetic field when there is a pressure-driven or electroosmotic flow through a microchannel. Successful magnetophoretic capture occurs if the strength of the field-inducing magnetic dipole exceeds a critical value, or if the particles are larger than a critical size. The magnetophoretic separator performance is characterized in terms of capture efficiency. The analysis shows that the capture efficiency is a function of two independent non-dimensional parameters, λ and γ that in turn involve all the physical design and operating parameters of the microfluidic separator, e.g., the dipole strength, particle size and susceptibility, fluid viscosity and velocity, channel height, and the separation of the dipole. Parametric plots of capture efficiency as function of λ and γ helps in choosing the right design and operation parameter of a practical microfluidic separator for a target level of performance. 相似文献
65.
66.
J.S. Yadav B.V. Subba Reddy B. Anusha U.V. Subba Reddy V.V. Bhadra Reddy 《Tetrahedron letters》2010,51(21):2872-4381
The synthesis of symmetrical 2,6-disubstituted 4-fluorotetrahydropyran derivatives has been achieved using HBF4·OEt2 via a tandem allylation and Prins cyclization. This is a highly efficient and diastereoselective approach for the preparation of 4-fluorotetrahydropyrans in a single step. The use of readily available and easy to handle reagent HBF4·OEt2 makes this method simple, convenient and practical. 相似文献
67.
Suvendu Ranjan Pattanaik 《Set-Valued and Variational Analysis》2011,19(3):329-341
In this article, necessary optimality conditions for mathematical programming problems under generalized equation constraints
problems are studied in Asplund spaces. We consider a very general version of the problem and derive necessary optimality
conditions under various hypothesis on the problem data and sacrificing the differentiability assumption. 相似文献
68.
Eric A. Voight Jerome F. Daanen Bhadra H. Shelat Daniel J. Plata 《Tetrahedron letters》2010,51(45):5904-5907
Starting from a variety of substituted chroman-4-ones, a highly enantioselective CBS reduction using in situ-generated B-H catalyst gave (S)-chroman-4-ols. Azide inversion and reduction gave crude (R)-chroman-4-amines, which could be purified without chromatography by isolation as the (R)-mandelic or d-tartaric acid salts with good yields and excellent ee. 相似文献
69.
In this paper we report a new method of fabrication of surface tensionconfined microfluidic devices on glass. We have also
successfully carried out some well-known chemical reactions in these fluidic channels to demonstrate the usefulness of these
wall-less microchannels. The confined flow path of liquid was achieved on the basis of extreme differences in hydrophobic
and hydrophilic characters of the surface. The flow paths were fabricated by making parallel lines using permanent marker
pen ink or other polymer on glass surfaces. Two mirror image patterned glass plates were then sandwiched one on top of the
other, separated by a thin gap-created using a spacer. The aqueous liquid moves between the surfaces by capillary forces,
confined to the hydrophilic areas without wetting the hydrophobic lines, achieving liquid confinement without physical side-walls.
We have shown that the microfluidic devices designed in such a way can be very useful due to their simplicity and low fabrication
cost. More importantly, we have also demonstrated that the minimum requirement of such a working device is a hydrophilic line
surrounded by hydrophobic environment, two walls of which are constituted of air and the rest is made of a hydrophobic surface. 相似文献
70.
Ranjan Sengupta 《Journal of voice》1990,4(2)
This article deals with a spectrographic analysis of the singer's formant as occurred during singing of the vowels /a/, /i/, and /o/ in North Indian classical vocal music. The resonance balance, center frequency, and band-width are shown as a function of fundamental frequency for eight singers.Two new parameters have been defined viz. asymmetry parameter (A) and spectral energy balance (W). Their variation with fundamental frequency is shown. 相似文献