全文获取类型
收费全文 | 2680篇 |
免费 | 291篇 |
国内免费 | 342篇 |
专业分类
化学 | 733篇 |
晶体学 | 21篇 |
力学 | 336篇 |
综合类 | 76篇 |
数学 | 1213篇 |
物理学 | 934篇 |
出版年
2024年 | 8篇 |
2023年 | 28篇 |
2022年 | 53篇 |
2021年 | 58篇 |
2020年 | 53篇 |
2019年 | 61篇 |
2018年 | 54篇 |
2017年 | 91篇 |
2016年 | 91篇 |
2015年 | 93篇 |
2014年 | 167篇 |
2013年 | 222篇 |
2012年 | 168篇 |
2011年 | 183篇 |
2010年 | 129篇 |
2009年 | 179篇 |
2008年 | 188篇 |
2007年 | 192篇 |
2006年 | 151篇 |
2005年 | 153篇 |
2004年 | 120篇 |
2003年 | 114篇 |
2002年 | 111篇 |
2001年 | 91篇 |
2000年 | 75篇 |
1999年 | 83篇 |
1998年 | 66篇 |
1997年 | 66篇 |
1996年 | 51篇 |
1995年 | 33篇 |
1994年 | 33篇 |
1993年 | 14篇 |
1992年 | 28篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 4篇 |
1988年 | 15篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有3313条查询结果,搜索用时 0 毫秒
231.
选取江苏弶港地区JC-1203钻孔, 通过分析其岩性、沉积物粒度参数和概率累计曲线, 结合已有文献资料和测年数据, 将JC-1203钻孔0~50.00m段自上而下分为5个沉积单元(DU1、DU2、DU3、DU4和DU5). 研究表明: DU1段(0~4.00m), 中值粒径(Md)为3.40~4.94Φ, 平均4.31Φ, 分选系数(δ1)为0.94~1.82, 平均1.24, 粒度概率累积曲线由跃移?–悬浮两组分构成, 滚动组分缺失, 反映了MIS1末期研究区为潮坪相沉积环境; DU2段(4.00~27.39m), Md为1.96~4.87Φ, 均值3.30Φ, δ1为0.54~2.17, 均值1.25, 曲线形态为跃移?–悬浮两单元构成, 反映研究区MIS1中?–末期为潮流沙脊相沉积; DU3段(27.39~37.33m), Md为1.90~4.18Φ, 均值2.79Φ, δ1为0.54~2.24, 均值1.34, 曲线形态为跃移?–悬浮两单元构成, 反映研究区MIS1早?–中期为滨海相沉积环境; DU4段(37.33~45.54m), Md为4.14~6.79Φ, 均值6.00Φ, δ1为1.5~2.3, 均值1.8, 概率累积曲线形态复杂多变, 反映研究区MIS3中?–末期的陆相河流沉积环境; DU5段(45.54~ 50.00m), Md为3.18~6.40Φ, 均值4.94Φ, δ1为0.99~1.97, 均值1.67, 曲线形态以滚动?–跃移?–悬浮三单元构成为主, 反映研究区MIS3早期的浅海相沉积环境. 相似文献
232.
Voronov V. P. Belyakov M. Yu. Gorodetskii E. E. Kulikov V. D. Muratov A. R. Nagaev V. B. 《Transport in Porous Media》2003,51(2):123-140
The adiabatic calorimetry method is used to measure the isochoric heat capacity and the dew-bubble curves for the methane-normal pentane mixtures in bulk for three different mixture compositions of n-pentane. The near-critical behavior of the mixture heat capacity indicates that at low n-pentane concentrations, this system is close to the special point of the critical locus. The effect of porous medium has been investigated for one of the mixtures studied in bulk. It has been shown that in porous medium the essential shift of the dew-bubble curve takes place. In our opinion this shift is caused by the formation of wetting film on the surface of porous medium. The estimation of film thickness resulting from the data obtained yields the value 7–8 nm. 相似文献
233.
A set X of boundary points of a (possibly unbounded) convex body KE
d illuminating K from within is called primitive if no proper subset of X still illuminates K from within. We prove that for such a primitive set X of an unbounded, convex set KE
d (distinct from a cone) one has X=2 if d=2, X6 if d=3, and that there is no upper bound for X if d4. 相似文献
234.
Augusto Nobile 《Geometriae Dedicata》2000,80(1-3):1-27
First, a modern presentation of the theory of the Halphen transform is given. This method associates to a plane projective curve C, once a general conic has been chosen, another birationally equivalent plane curve, whose singularities are simpler than those of C. Repeating, a curve is obtained whose only singularities are nodes. Next, it is studied how to apply this process to a family of plane curves. With this technique it is possible to transform a given family (with irreducible general member) into one where, generically, the curves are nodal. Finally, it is studied a similar process, called the Halphen–Picard transformation, for surfaces in three-space. By suitably reiterating this procedure, a surface can be transformed into a birationally equivalent one (in the same projective space), such that the sections with planes in a general pencil are, generically, nodal curves. 相似文献
235.
Analysis of the Xedni Calculus Attack 总被引:3,自引:0,他引:3
Michael J. Jacobson Neal Koblitz Joseph H. Silverman Andreas Stein Edlyn Teske 《Designs, Codes and Cryptography》2000,20(1):41-64
The xedni calculus attack on the elliptic curve discrete logarithm problem (ECDLP) involves lifting points from the finite field
to the rational numbers
and then constructing an elliptic curve over
that passes through them. If the lifted points are linearly dependent, then the ECDLP is solved. Our purpose is to analyze the practicality of this algorithm. We find that asymptotically the algorithm is virtually certain to fail, because of an absolute bound on the size of the coefficients of a relation satisfied by the lifted points. Moreover, even for smaller values of p experiments show that the odds against finding a suitable lifting are prohibitively high. 相似文献
236.
垄断厂商在固定折扣率条件下的二度价格歧视研究 总被引:14,自引:1,他引:14
在线性需求函数的条件下,研究了垄断厂商实行二度价格歧视时确定最优固定折扣率的方法,研究结果表明,如果销售量和分段区间数既定,则最优固定折扣率存在。 相似文献
237.
用改进的变形参数法求得了激励的幅值不是小量时Mathieu方程的周期解及过渡曲线。 相似文献
238.
Martin Mller 《Mathematische Nachrichten》2005,278(9):1061-1077
Teichmüller curves are geodesic discs in Teichmüller space that project to algebraic curves C in the moduli space Mg. Some Teichmüller curves can be considered as components of Hurwitz spaces. We show that the absolute Galois group G? acts faithfully on the set of these embedded curves. We also compare the action of G? on π1(C) with the one on π1(Mg) and obtain a relation in the Grothendieck–Teichmüller group, seemingly independent of the known ones. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
239.
针对三种复苏液治疗失血性休克的血气指标,利用机理分析方法建立了血气指标的微分模型,给出血气指标的指数曲线表达式,并结合试验数据进行了曲线拟合,得到了指数曲线的具体形式,结果与试验数据高度吻合同时分析了用药的效果.利用统计分析方法给出三种复苏液治疗失血性休克的动脉血、静脉血和肠系膜静脉血的血气指标间的回归曲线关系式. 相似文献
240.
B.A. Kats 《Journal of Mathematical Analysis and Applications》2009,356(2):577-187
Let Γ be a closed non-rectifiable Jordan curve on the complex plane C. We consider the so-called jump problem, i.e. the boundary value problem for determination of a holomorphic in function with a given jump on Γ. The main result is a condition of solvability of the problem in terms of a new metric dimension of the curve. 相似文献