全文获取类型
收费全文 | 14790篇 |
免费 | 626篇 |
国内免费 | 501篇 |
专业分类
化学 | 3392篇 |
晶体学 | 166篇 |
力学 | 587篇 |
综合类 | 69篇 |
数学 | 6777篇 |
物理学 | 4926篇 |
出版年
2024年 | 29篇 |
2023年 | 168篇 |
2022年 | 247篇 |
2021年 | 256篇 |
2020年 | 401篇 |
2019年 | 390篇 |
2018年 | 353篇 |
2017年 | 319篇 |
2016年 | 315篇 |
2015年 | 343篇 |
2014年 | 634篇 |
2013年 | 774篇 |
2012年 | 441篇 |
2011年 | 1284篇 |
2010年 | 858篇 |
2009年 | 990篇 |
2008年 | 1137篇 |
2007年 | 995篇 |
2006年 | 779篇 |
2005年 | 695篇 |
2004年 | 575篇 |
2003年 | 473篇 |
2002年 | 499篇 |
2001年 | 261篇 |
2000年 | 277篇 |
1999年 | 281篇 |
1998年 | 216篇 |
1997年 | 201篇 |
1996年 | 190篇 |
1995年 | 167篇 |
1994年 | 186篇 |
1993年 | 172篇 |
1992年 | 149篇 |
1991年 | 109篇 |
1990年 | 88篇 |
1989年 | 85篇 |
1988年 | 59篇 |
1987年 | 57篇 |
1986年 | 56篇 |
1985年 | 71篇 |
1984年 | 59篇 |
1983年 | 38篇 |
1982年 | 54篇 |
1981年 | 42篇 |
1980年 | 40篇 |
1979年 | 20篇 |
1978年 | 30篇 |
1977年 | 18篇 |
1976年 | 17篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Panagiotis Soules 《Archiv der Mathematik》2003,80(5):449-457
For soluble groups, the Fitting length is bounded by a function of the maximum order
of the Fitting subgroups of 2-generator subgroups. 相似文献
92.
In this paper, we study the Hilbert–Samuel function of a generic standard graded K-algebrawhen refined by an (ℓ)-adic filtration, ℓ being a linear form. From this we obtain a structure theorem which describes the stairs of a generic complete intersection for the degree-reverse-lexicographic order. We show what this means for generic standard (or Gröbner) bases for this order; in particular, we consider an “orderly filling up” conjecture, and we propose a strategy for the standard basis algorithm which could be useful in generic-like cases. 相似文献
K[X1,…,Xn]/(g1,…,gm)
93.
Janusz Mierczyński Wenxian Shen Xiao-Qiang Zhao 《Journal of Differential Equations》2004,204(2):471-510
The purpose of this paper is to investigate uniform persistence for nonautonomous and random parabolic Kolmogorov systems via the skew-product semiflows approach. It is first shown that the uniform persistence of the skew-product semiflow associated with a nonautonomous (random) parabolic Kolmogorov system implies that of the system. Various sufficient conditions in terms of the so-called unsaturatedness and/or Lyapunov exponents for uniform persistence of the skew-product semiflows are then provided. Among others, it is shown that if the associated skew-product semiflow has a global attractor and its restriction to the boundary of the state space has a Morse decomposition which is unsaturated or whose external Lyapunov exponents are positive, then it is uniformly persistent. More specific conditions are discussed for uniform persistence in n-species, particularly 3-species, random competitive systems. 相似文献
94.
Elvira Vidović Doris Klee Hartwig Höcker 《Journal of polymer science. Part A, Polymer chemistry》2007,45(19):4536-4544
Poly(D ,L ‐lactide) and poly(D ,L ‐lactide‐co‐glycolide) with various composition and with one methacrylate and one carboxylate end group were synthesized and grafted onto poly(vinyl alcohol) (PVA) via the carboxylate group. The graft copolymers were crosslinked via the methacrylate groups using a free radical initiator. The polymer networks were characterized by means of NMR and studied qualitatively by means of IR spectroscopy. The influence of the glycolide content in the polyester grafts and of the number of ester units in the grafts on thermal properties and swellability were studied as well. The high swellability in water is characteristic of all hydrogels. Differential scanning calorimetry (DSC) showed a single glass transition temperature that occurs in the range between 51 and 69 °C. Thermogravimetric analysis (TGA) of the networks showed the main loss in weight in the temperature range between 290 and 370 °C. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4536–4544, 2007 相似文献
95.
Implementation and experimental study on fast object modeling based on multiple structured stripes 总被引:6,自引:0,他引:6
In this paper, a practical structured light-based system for fast object modeling and reconstruction is reported. The system consists of an off-the-shelf digital projector, a video camera and a turntable. The system calibration is implemented accurately and automatically by taking a single image of an illuminated calibration template. The multiple color light stripes emitted by the projector adopt only three colors and the color can be modified easily according to the surface texture of the object. This makes the system widely applicable in many situations, and the assumption about color neutrality, which is a limitation to other similar systems, can be largely relaxed. The registration and merging algorithm is greatly simplified by employing a turntable. The validity and high accuracy of the method are demonstrated by extensive real experiments. 相似文献
96.
Akira Sakakura 《Tetrahedron》2004,60(33):7067-7075
To obtain information on the chemical modification of biomolecules with jolkinolide D, a bioactive diterpenoid of plant origin, jolkinolide D pharmacophore was synthesized, and its reactivity toward amino acids, nucleosides, and DNA was investigated. 相似文献
97.
K. Popov-Pergal L. Cuckovic M. Rancic M. Pergal D. Djokovic 《Chemistry of Heterocyclic Compounds》2003,39(8):1090-1093
A series of methyl 2-(arylidene-2,4-dioxotetrahydrothiazol-3-yl)propionates were prepared. A study of the 3D structure was performed. The log P values are given for all the synthesized compounds. 相似文献
98.
Anatol Odzijewicz 《Journal of Functional Analysis》2004,217(1):103-125
The extension of Banach Lie-Poisson spaces is studied and linked to the extension of a special class of Banach Lie algebras. The case of W∗-algebras is given particular attention. Semidirect products and the extension of the restricted Banach Lie-Poisson space by the Banach Lie-Poisson space of compact operators are given as examples. 相似文献
99.
Lenny Fukshansky 《Journal of Number Theory》2004,108(1):29-43
Given a quadratic form and M linear forms in N+1 variables with coefficients in a number field K, suppose that there exists a point in KN+1 at which the quadratic form vanishes and all the linear forms do not. Then we show that there exists a point like this of relatively small height. This generalizes a result of D.W. Masser. 相似文献
100.
Gravimetric measurements of thermodesorption of n-hexane and n-heptane were performed under quasi-equilibrium conditions. Differential thermodesorption profiles for ZSM-5 and ZSM-11 showed two peaks, but for Y zeolites, only one thermodesorption peak was observed. A model function, derived from the Langmiur adsorption model, was fitted to the experimental data, and the model parameters (the adsorption entropy and enthalpy) were estimated. The two-step desorption profiles observed for ZSM-5 and ZSM-11 were attributed to the commensurate freezing effect, i.e. a transition in the adsorbed phase resulting in ordering of the adsorbed molecules in the zeolite channels. The results observed for ZSM-11 indicate that the zigzag channels typical for ZSM-5 micropore system are not necessary for this transition to occur. 相似文献