全文获取类型
收费全文 | 966篇 |
免费 | 87篇 |
国内免费 | 97篇 |
专业分类
化学 | 318篇 |
晶体学 | 1篇 |
力学 | 244篇 |
综合类 | 26篇 |
数学 | 347篇 |
物理学 | 214篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 18篇 |
2021年 | 46篇 |
2020年 | 54篇 |
2019年 | 46篇 |
2018年 | 39篇 |
2017年 | 35篇 |
2016年 | 45篇 |
2015年 | 28篇 |
2014年 | 46篇 |
2013年 | 58篇 |
2012年 | 43篇 |
2011年 | 61篇 |
2010年 | 42篇 |
2009年 | 37篇 |
2008年 | 35篇 |
2007年 | 51篇 |
2006年 | 52篇 |
2005年 | 42篇 |
2004年 | 43篇 |
2003年 | 47篇 |
2002年 | 38篇 |
2001年 | 26篇 |
2000年 | 29篇 |
1999年 | 24篇 |
1998年 | 19篇 |
1997年 | 23篇 |
1996年 | 13篇 |
1995年 | 16篇 |
1994年 | 7篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1971年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有1150条查询结果,搜索用时 125 毫秒
991.
加速器质谱(AMS) 由于其极高的测量灵敏度而广泛应用于核科学、生命科学、地球科学、环境科学和考古学等研究领域,同时,AMS还可以用来分析样品中的微量核素,是核科学领域的重要研究工具。目前,AMS研究的最新领域是U和Pu 等锕系元素的测量,在核保障、核监测及核试验沉降物示踪大气输运和表面沉积物的迁移等研究中也显示出了较大潜力。综述了AMS在核科学研究中的应用及研究现状,主要包括AMS在放射性核素半衰期的测定、核反应截面的测量等方面的研究进展。Accelerator mass spectrometry (AMS) is a promising method to provide extreme sensitivity measurements of the production yields of long-lived radioisotopes, which cannot be detected by other methods. AMS technique plays an important role in the research of nuclear physics, as well as the application field of AMS covered nuclear science and technology, life science, earth science, environmental science, archaeology etc. The newest AMS field is that of actinide, particularly U and Pu, isotopic assay with expanding applications in nuclear safeguards and monitoring, and as a modern bomb-fallout tracer for atmospheric transport and surface sediment movement. This paper reviews the applications of AMS in the research of nuclear energy and nuclear security including the research of half life of radionuclides, cross section of nuclear reaction. 相似文献
992.
Solving Planning and Design Problems in the Process Industry Using Mixed Integer and Global Optimization 总被引:1,自引:0,他引:1
Josef Kallrath 《Annals of Operations Research》2005,140(1):339-373
This contribution gives an overview on the state-of-the-art and recent advances in mixed integer optimization to solve planning
and design problems in the process industry. In some case studies specific aspects are stressed and the typical difficulties
of real world problems are addressed.
Mixed integer linear optimization is widely used to solve supply chain planning problems. Some of the complicating features
such as origin tracing and shelf life constraints are discussed in more detail. If properly done the planning models can also
be used to do product and customer portfolio analysis.
We also stress the importance of multi-criteria optimization and correct modeling for optimization under uncertainty. Stochastic
programming for continuous LP problems is now part of most optimization packages, and there is encouraging progress in the
field of stochastic MILP and robust MILP.
Process and network design problems often lead to nonconvex mixed integer nonlinear programming models. If the time to compute
the solution is not bounded, there are already a commercial solvers available which can compute the global optima of such
problems within hours. If time is more restricted, then tailored solution techniques are required. 相似文献
993.
王华磊 张玉虎 周小红 郭应祥 雷祥国 徐树威 谢元祥 郑勇 柳敏良 邢烨炳 谢成营 宋立涛 郭文涛 T.Hayakawa M.Oshima Y.Toh J.Katakura Y.Hatssukawa M.Matsuda N.Shinohara T.Ishii H.Kusakari M.Sugawara T.Komatsubara 《原子核物理评论》2006,23(1):13-17
利用在束实验产生具有β^+/EC衰变性质核素^176,178Ir,分析了在柬实验条件下获得的γ—γ符合数据,识别出了^176Os的4条新能级和13条新γ跃迁、^178Os的5条新能级和14条新γ跃迁。籍助氨喷嘴快速带传输系统,进一步对^176Ir的β’/EC衰变进行了测量,在确认在束测量新γ射线的同时建议了^176Ir的一个低自旋同核异能态。通过两准粒子耦舍的半经验计算,建议了^176,178Ir基态及同核异能态的组态。The γ rays following the β^+/EC decay of ^176. 178Ir nuclei have been investigated using in-beam γ- ray experiment. A total of 4 new levels, 13 new γ transitions of ^176Os and 5 new levels, 14 new γ transitions of ^178Os were identified. In addition, with the aid of a helium-jet recoil fast tape transport system, the β^+/EC decay of ^176Ir was further studied, the above new γ rays were proved and an isomer was proposed in ^176Ir. By the semiempirical calculations of two-quasiparticle intrinsic states of odd-odd nuclei, the configurations of ground states and isomeric states were also proposed for ^176, 178Ir 相似文献
994.
一种新的武器总体综合设计方法 总被引:1,自引:0,他引:1
对武器装备的作战效能、寿命周期费用、风险和研制周期的模型进行了研究,提出了综合运用这四维指标作为目标函数的武器总体综合设计的思路和数学模型,可以全面而系统地认识武器装备的发展问题,避免设计中由于只注重提高性能而引起的弊端. 相似文献
995.
Toshiharu Higuchi Shigehiko Yamamoto Hiroshi Kudo Hirotaka Murata 《Applied Surface Science》2002,200(1-4):125-137
We have developed the calculation method for ion bombardment traces. When an M type dispenser cathode is operated in a cathode ray tube (CRT), the surface coating film is subjected to ion bombardment due to ionized residual gas. With long-time use, the coating film is dissipated and a change to an S type occurs. This occurrence of an S type causes a deterioration of emission and focus characteristics. A method for calculating the life time dependency of the shape of ion bombardment traces using the degree of vacuum in the tube, the grid voltage, and the cathode current was studied. The calculated results and measured results were in close agreement. As a result, it was confirmed that modeling is possible using (1) an electron and ion beam trajectory calculation program, and (2) formulas for calculating the ionization cross-section and sputtering yield. 相似文献
996.
Dilip Roy 《Annals of the Institute of Statistical Mathematics》2002,54(2):404-410
The earlier concept of bivariate lack of memory property has been examined and an alternative concept of bivariate lack of memory property has been presented along with a set of equivalent conditions. In this process, the link relations known in the literature on univariate lack of memory property have been extended to the bivariate set-up. A multivariate extension of the lack of memory property has also been proposed. 相似文献
997.
Under the reliability NBU/NWU conditions, the exponential distribution is characterized by stochastic ordering properties
which link the geometric compound with minimum order statistics or spacings of order statistics. This somewhat answers a question
posed by Kakosyan, Klebanov and Melamed (1984,Characterization of Distributions by the Method of intensively Monotone Operators, Springer, New York). We also show the related results based on the residual life in a renewal process and on record values.
Finally, some fundamental properties of the NBUC/NWUC classes of life distributions are investigated. 相似文献
998.
The k‐out‐of‐n structure is a very popular type of redundancy in fault‐tolerant systems, it has founded wide applications in industrial and military systems during the past several decades. This paper will investigate the residual life length of a k‐out‐of‐n system with independent (not necessarily identical) components, given that the (n?k)th failure has occurred at time t?0. Behaviour of PF2, IFR, DRHR, DMRL, NBU(2) and NBUC classes of life distributions are derived in terms of the monotonicity of the residual life given the time of the (n?k)th failure. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
999.
随机利率下增额寿险现值函数矩的一些结果 总被引:5,自引:0,他引:5
本文对随机利率采用 Wiener过程和 Orentein- Uhlenbeck过程建模 ,得到了增额寿险现值函数的矩的一些结果 相似文献
1000.
对数正态分布场合有非常数尺度参数恒加试验的参数估计 总被引:1,自引:0,他引:1
王炳兴 《高校应用数学学报(A辑)》2003,18(2):200-206
讨论了对数正态分布场合有非常数尺度参数恒加寿命试验的参数估计,导出了基于全样本和定数截尾样本恒加试验的点估计和近似区间估计。 相似文献