全文获取类型
收费全文 | 13530篇 |
免费 | 898篇 |
国内免费 | 355篇 |
专业分类
化学 | 10019篇 |
晶体学 | 147篇 |
力学 | 359篇 |
综合类 | 31篇 |
数学 | 1517篇 |
物理学 | 2710篇 |
出版年
2023年 | 116篇 |
2022年 | 204篇 |
2021年 | 260篇 |
2020年 | 325篇 |
2019年 | 309篇 |
2018年 | 253篇 |
2017年 | 224篇 |
2016年 | 465篇 |
2015年 | 416篇 |
2014年 | 485篇 |
2013年 | 737篇 |
2012年 | 902篇 |
2011年 | 973篇 |
2010年 | 612篇 |
2009年 | 536篇 |
2008年 | 843篇 |
2007年 | 810篇 |
2006年 | 841篇 |
2005年 | 740篇 |
2004年 | 620篇 |
2003年 | 569篇 |
2002年 | 509篇 |
2001年 | 247篇 |
2000年 | 191篇 |
1999年 | 119篇 |
1998年 | 129篇 |
1997年 | 151篇 |
1996年 | 190篇 |
1995年 | 135篇 |
1994年 | 115篇 |
1993年 | 167篇 |
1992年 | 108篇 |
1991年 | 112篇 |
1990年 | 117篇 |
1989年 | 107篇 |
1988年 | 76篇 |
1987年 | 64篇 |
1986年 | 71篇 |
1985年 | 109篇 |
1984年 | 87篇 |
1983年 | 60篇 |
1982年 | 93篇 |
1981年 | 88篇 |
1980年 | 70篇 |
1979年 | 70篇 |
1978年 | 61篇 |
1977年 | 51篇 |
1976年 | 62篇 |
1975年 | 34篇 |
1974年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
81.
82.
Matthew D. Bailey Steven M. Shechter Andrew J. Schaefer 《Operations Research Letters》2006,34(3):307-315
We consider a general adversarial stochastic optimization model. Our model involves the design of a system that an adversary may subsequently attempt to destroy or degrade. We introduce SPAR, which utilizes mixed-integer programming for the design decision and a Markov decision process (MDP) for the modeling of our adversarial phase. 相似文献
83.
Summary Laser ablation inductively coupled plasma-source mass spectrometry has been used to determine thirty elements (Na, Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, As, Rb, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Dy, Ho, Yb, Hf, Ta, W, Th, U) in seven Chinese reference soils. The Surrey prototype spectrometer was employed with sample ablation by a free-running ruby laser. Concentrations in the soils (GSS-2 to GSS-8) were calculated from elemental responses and sensitivities derived from another soil in the series, namely GSS-1. Comparisons with previous neutron activation analyses are made. Rapid semiquantitative analyses are proved feasible. About eighty percent of the LA-ICP-MS determined concentrations were within a factor of two of the concentrations measured by INAA, and many were considerably closer than this. Precisions were typically in the range 2–10% RSD, but some were considerably poorer for elements present at trace levels. 相似文献
84.
Hardy spaces of analytic functions are studied both on strongly pseudoconvex domains in ℂn and on domains of finite type in ℂ2. Duality theorems, atomic decompositions, and factorization of functions are treated. Mapping properties of certain Hankel
operators are studied. 相似文献
85.
Optimization of plate buckling resistance is very complicated, because the in-plane stress resultants in the prebuckled state of a plate are functions of thickness distribution. This paper discusses the problem of finding the optimum thickness distribution of isotropic plate structures, with a given volume and layout, that would maximise the buckling load. A simple numerical method using the finite-element analysis is presented to obtain the optimum thickness distribution. Optimum designs of compression-loaded rectangular plates with different boundary conditions and plate aspect ratios are obtained by using the proposed method. Optimum designs from earlier studies and the methods of buckling analysis used to attain these results are discussed and compared with the designs from the proposed method. This paper also examines the reliability of the optimality criterion generally used for plate buckling optimization, which is based on the uniform strain energy density. 相似文献
86.
87.
David P. Dobkin Steven J. Friedman Kenneth J. Supowit 《Discrete and Computational Geometry》1990,5(1):399-407
LetS be any set ofN points in the plane and let DT(S) be the graph of the Delaunay triangulation ofS. For all pointsa andb ofS, letd(a, b) be the Euclidean distance froma tob and let DT(a, b) be the length of the shortest path in DT(S) froma tob. We show that there is a constantc (≤((1+√5)/2) π≈5.08) independent ofS andN such that $$\frac{{DT(a,b)}}{{d(a,b)}}< c.$$ 相似文献
88.
89.
Kumita T Sagawa H Auchincloss P Blanis D Bodek A Budd H Eno S Fry CA Harada H Ho YH Kim YK Mori T Olsen SL Shaw NM Sill A Thorndike EH Ueno K Zheng HW Abe K Fujii Y Higashi Y Kim SK Kurihara Y Maki A Nozaki T Omori T Sakai Y Sugimoto Y Takaiwa Y Terada S Walker R Imlay R Kirk P Lim J McNeil RR Metcalf W Myung SS Cheng CP Gu P Li J Li YK Ye MH Zhu YC Abashian A Gotow K Hu KP Low EH Mattson ME Piilonen L Sterner KL Lusin S Rosenfeld C Wang AT Wilson S Frautschi M Kagan H Kass R Trahern CG 《Physical review D: Particles and fields》1990,42(5):1339-1349
90.