全文获取类型
收费全文 | 1223篇 |
免费 | 34篇 |
国内免费 | 3篇 |
专业分类
化学 | 958篇 |
晶体学 | 38篇 |
力学 | 12篇 |
数学 | 48篇 |
物理学 | 204篇 |
出版年
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 13篇 |
2019年 | 27篇 |
2018年 | 30篇 |
2017年 | 15篇 |
2016年 | 15篇 |
2015年 | 29篇 |
2014年 | 28篇 |
2013年 | 80篇 |
2012年 | 71篇 |
2011年 | 65篇 |
2010年 | 31篇 |
2009年 | 36篇 |
2008年 | 61篇 |
2007年 | 74篇 |
2006年 | 63篇 |
2005年 | 59篇 |
2004年 | 42篇 |
2003年 | 40篇 |
2002年 | 59篇 |
2001年 | 30篇 |
2000年 | 27篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 14篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 27篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1972年 | 6篇 |
排序方式: 共有1260条查询结果,搜索用时 0 毫秒
271.
Arasambattu K. Mohanakrishnan Natarajan Senthil Kumar P. Amaladass 《Tetrahedron letters》2008,49(32):4792-4795
The synthesis of soluble benzo[c]thiophene analogs capped with 9,9-dialkylfluorene at one end is described. 相似文献
272.
273.
An important question in discrete optimization under uncertainty is to understand the persistency of a decision variable, i.e., the probability that it is part of an optimal solution. For instance, in project management,
when the task activity times are random, the challenge is to determine a set of critical activities that will potentially
lie on the longest path. In the spanning tree and shortest path network problems, when the arc lengths are random, the challenge
is to pre-process the network and determine a smaller set of arcs that will most probably be a part of the optimal solution
under different realizations of the arc lengths. Building on a characterization of moment cones for single variate problems,
and its associated semidefinite constraint representation, we develop a limited marginal moment model to compute the persistency
of a decision variable. Under this model, we show that finding the persistency is tractable for zero-one optimization problems
with a polynomial sized representation of the convex hull of the feasible region. Through extensive experiments, we show that
the persistency computed under the limited marginal moment model is often close to the simulated persistency value under various
distributions that satisfy the prescribed marginal moments and are generated independently. 相似文献
274.
Obtaining (tail) probabilities from a transform function is an important topic in queueing theory. To obtain these probabilities
in discrete-time queueing systems, we have to invert probability generating functions, since most important distributions
in discrete-time queueing systems can be determined in the form of probability generating functions. In this paper, we calculate
the tail probabilities of two particular random variables in discrete-time priority queueing systems, by means of the dominant
singularity approximation. We show that obtaining these tail probabilities can be a complex task, and that the obtained tail
probabilities are not necessarily exponential (as in most ‘traditional’ queueing systems). Further, we show the impact and
significance of the various system parameters on the type of tail behavior. Finally, we compare our approximation results
with simulations. 相似文献
275.
276.
Using the spectrally resolved white light interferometry we present our experimental results on the measurement of the optical
constants of thin polymer films coated on a transparent substrate. As an extension to our previous work (J. Opt. Soc. Am.
B12, 1559 (1995)) on thick glass plates, we have shown here that this technique can be effectively applied to very thin polymer
films also. We have improved the accuracy of our results by using the Sellmeier dispersion formula for fitting the data. From
the width and position of the zero-order fringe and the frequency of modulations in the white light spectrum, the refractive
indexn(λ) and thicknesst of the thin polymer films are calculated. To study the accuracies involved in the technique, PVA, PMMA and PS films of varied
thicknesses are coated on glass plates and the measured values are compared with ellipsometer studies. 相似文献
277.
Chandrasekhar Das 《The Journal of the Operational Research Society》1984,35(11):995-1001
The price-break problem is a non-linear discrete problem of two variables and three parameters which is not solvable analytically. As such, a graphical solution is suggested here by re-formulating the problem in two stages: first, as an equivalent non-linear, and next, as a linear problem of two variables and a single parameter. The later formulation affords an efficient graphical solution which was not possible earlier. In addition, useful procedures for plotting iso-cost curves and deriving approximate numerical solutions are also discussed. 相似文献
278.
279.
280.
M. V. S. Chandrasekhar Rao N. Venkateswara Rao S. Bhuloka Reddy G. Satyanarayana D. L. Sastry M. R. Iyer S. G. Sahasrabhude 《Zeitschrift für Physik A Hadrons and Nuclei》1988,330(2):161-165
The total conversion coefficient of the 127.49 keV E3 isomeric transition in the decay of134mCs was measured using the gamma intensity balance method with the help of a high resolution low energy photon detector. Theα Tvalue was found to be 5.84±0.47 as against the theoretical value of 6.96, thus showing an anomaly of (16.1±6.7)%. TheK-conversion coefficient,α kwas also measured using the X-ray peak to gamma ray intensity method and found to be 2.24±0.04 as against the theoretical value of 2.72, which shows an anomaly of (17.6±1.4)% consistent with the experimental anomaly inα T. TheE3 hindrance factor of the isomeric transition was estimated to be (3.44±0.23) ·104. 相似文献