全文获取类型
收费全文 | 83490篇 |
免费 | 7663篇 |
国内免费 | 9272篇 |
专业分类
化学 | 38144篇 |
晶体学 | 343篇 |
力学 | 6624篇 |
综合类 | 1322篇 |
数学 | 29309篇 |
物理学 | 24683篇 |
出版年
2024年 | 148篇 |
2023年 | 819篇 |
2022年 | 1651篇 |
2021年 | 1799篇 |
2020年 | 2017篇 |
2019年 | 2288篇 |
2018年 | 1803篇 |
2017年 | 2088篇 |
2016年 | 2614篇 |
2015年 | 2464篇 |
2014年 | 3280篇 |
2013年 | 6041篇 |
2012年 | 3681篇 |
2011年 | 4115篇 |
2010年 | 3509篇 |
2009年 | 4791篇 |
2008年 | 5221篇 |
2007年 | 5520篇 |
2006年 | 5086篇 |
2005年 | 4286篇 |
2004年 | 3855篇 |
2003年 | 3857篇 |
2002年 | 3379篇 |
2001年 | 2853篇 |
2000年 | 2787篇 |
1999年 | 2451篇 |
1998年 | 2300篇 |
1997年 | 1923篇 |
1996年 | 1643篇 |
1995年 | 1467篇 |
1994年 | 1346篇 |
1993年 | 1151篇 |
1992年 | 1115篇 |
1991年 | 851篇 |
1990年 | 707篇 |
1989年 | 625篇 |
1988年 | 566篇 |
1987年 | 444篇 |
1986年 | 377篇 |
1985年 | 453篇 |
1984年 | 439篇 |
1983年 | 213篇 |
1982年 | 353篇 |
1981年 | 407篇 |
1980年 | 313篇 |
1979年 | 292篇 |
1978年 | 233篇 |
1977年 | 212篇 |
1976年 | 163篇 |
1974年 | 110篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
211.
Eremenko L. T. Oreshko G. V. Nesterenko D. A. Lagodzinskaya G. V. Eremenko I. L. 《Russian Chemical Bulletin》2002,51(1):157-159
The reactions of ethylene glycol mononitrate and glycerol 1,3-dinitrate with methylphosphonic dichloride afforded new nitroxyalkyl methylphosphonates. 相似文献
212.
Michael Giudici 《Designs, Codes and Cryptography》2006,39(2):163-172
We determine all linear codes C containing the constant code E, for which there is a weight-preserving group of semilinear automorphisms which acts transitively on the set of nontrivial
cosets of E in C.
Michael Giudici - The author holds an Australian Postdoctoral Fellowship. 相似文献
213.
External difference families (EDFs) are a type of new combinatorial designs originated from cryptography. In this paper, some
earlier ideas of recursive and cyclotomic constructions of combinatorial designs are extended, and a number of classes of
EDFs and disjoint difference families are presented. A link between a subclass of EDFs and a special type of (almost) difference
sets is set up. 相似文献
214.
Tatsuo Nakagawa Satoshi Fukura Munenori Nakai Kazumasa Sugiyama Ryohei Kokawa Hiroyuki Kagi 《Optical Review》2006,13(4):269-275
We constructed a scanning near-field optical microscope (SNOM) on a commercially available atomic force microscopy (AFM) apparatus
(SPM-9500J2; Shimadzu Corp.) to measure the stress distribution in ceramic composite materials. Features of our SNOM system
are: (1) a compact SNOM head substituted for the original AFM head; (2) a wide scanning range (125 × 125 μm2) inherited from the original scanner; (3) use of conventional shear-force regulation; (4) an optical system for the illumination-collection
(I-C) mode; (5) excitation by a 488 nm line of an Ar-ion laser, and (6) light detection by photon counting or a polychromator
equipped with an electronically cooled charge coupled device (CCD). This SNOM system was used to measure the surface structure
and stress distribution of an Al2O3/ZrO2 eutectic composite. We simultaneously measured topographic images and fluorescence spectra of an Al2O3/ZrO2 eutectic composite. We estimated its peak intensity, peak position, and peak width from the fluorescence spectrum during
scanning, which respectively correspond to the abundance of Al2O3, stress in the grain, and the anisotropy of that stress. Mapping images showed that the stress and its anisotropy were weaker
in the center of the Al2O3 grain than its boundary between Al2O3 and ZrO2. That observation suggests that Al2O3 underwent intense anisotropic stress induced by volume expansion in the phase transition of ZrO2 from the cubic phase to the monoclinic phase during preparation. 相似文献
215.
216.
The Rio de la Plata is a large and shallow water body that discharges onto the Atlantic Ocean. The main driving forces for the river flow are the bathymetry, tides, the outflow from the Paraná and Uruguay rivers and the winds. A numerical model covering the entire river was set up with the objective of increasing our understanding of the hydrographical features and morphological dynamics in the Estuary. The simulations revealed a counter-clockwise residual circulation in the Samborombón Bay and an eastward net flow near the Uruguayan coast. The residual flow is forced by both the tides and the bathymetry. The residence time for the entire river ranges from 40 to 80 days. However, residence times above 120 days was found in the Samborombón Bay. Three corridors of flow have been identified. 相似文献
217.
根据生产实际,综合利用并列、赋闲列和拟水平试验设计,运用多重比较进行方差分析,寻找水泥熟料的最佳工艺.不仅解决了不同水平多因素试验问题,同时还可考虑交互作用,大大减少了试验次数,从而提高经济效益. 相似文献
218.
M. A. Posypkin I. Kh. Sigal 《Computational Mathematics and Mathematical Physics》2006,46(12):2187-2202
The efficiency of parallel implementations of the branch-and-bound method in discrete optimization problems is considered. A theoretical analysis and comparison of two parallel implementations of this method is performed. A mathematical model of the computation process is constructed and used to obtain estimates of the maximum possible speedup. Examples of problems in which none of these two parallel implementations can speed up the computations are considered. 相似文献
219.
Youssef Randjiou 《Journal of Theoretical Probability》2006,19(3):701-720
Let μ+(t) and μ−(t) be the locations of the maximum and minimum, respectively, of a standard Brownian motion in the interval [0,t]. We establish a joint integral test for the lower functions of μ+(t) and μ−(t), in the sense of Paul Lévy. In particular, it yields the law of the iterated logarithm for max(μ+(t),μ−(t)) as a straightforward consequence. Our result is in agreement with well-known theorems of Chung and Erdős [(1952) Trans. Amer. Math. Soc. 72, 179–186.], and Csáki, F?ldes and Révész [(1987) Prob. Theory Relat. Fields
76, 477–497].
相似文献
220.
用三个关系式与Mathematica软件求第二类自然数幂和公式 总被引:1,自引:1,他引:0
首先介绍三个第二类自然数幂和关系式并对其中的两式给出证明,接着利用这些关系式与数学软件M athem atica4.0,给出求解第二类自然数幂和公式的若干机械计算方法. 相似文献