全文获取类型
收费全文 | 89804篇 |
免费 | 4912篇 |
国内免费 | 11729篇 |
专业分类
化学 | 70525篇 |
晶体学 | 1167篇 |
力学 | 2362篇 |
综合类 | 844篇 |
数学 | 12729篇 |
物理学 | 18818篇 |
出版年
2024年 | 82篇 |
2023年 | 631篇 |
2022年 | 1554篇 |
2021年 | 1784篇 |
2020年 | 2181篇 |
2019年 | 2145篇 |
2018年 | 1841篇 |
2017年 | 2692篇 |
2016年 | 2833篇 |
2015年 | 2363篇 |
2014年 | 3284篇 |
2013年 | 6586篇 |
2012年 | 6205篇 |
2011年 | 4958篇 |
2010年 | 4188篇 |
2009年 | 5746篇 |
2008年 | 5945篇 |
2007年 | 6149篇 |
2006年 | 5579篇 |
2005年 | 4719篇 |
2004年 | 4376篇 |
2003年 | 3625篇 |
2002年 | 4861篇 |
2001年 | 2791篇 |
2000年 | 2588篇 |
1999年 | 2432篇 |
1998年 | 2113篇 |
1997年 | 1663篇 |
1996年 | 1409篇 |
1995年 | 1352篇 |
1994年 | 1195篇 |
1993年 | 995篇 |
1992年 | 948篇 |
1991年 | 632篇 |
1990年 | 533篇 |
1989年 | 515篇 |
1988年 | 374篇 |
1987年 | 300篇 |
1986年 | 276篇 |
1985年 | 226篇 |
1984年 | 237篇 |
1983年 | 138篇 |
1982年 | 212篇 |
1981年 | 175篇 |
1980年 | 194篇 |
1979年 | 183篇 |
1978年 | 169篇 |
1977年 | 123篇 |
1976年 | 108篇 |
1973年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
261.
J. Schropp 《Numerische Mathematik》1997,78(1):87-101
Summary. We use the qualitative properties of the solution flow of the gradient equation to compute a local minimum of a real-valued function . Under the regularity assumption of all equilibria we show a convergence result for bounded trajectories of a consistent,
strictly stable linear multistep method applied to the gradient equation. Moreover, we compare the asymptotic features of
the numerical and the exact solutions as done by Humphries, Stuart (1994) and Schropp (1995) for one-step methods. In the
case of -stable formulae this leads to an efficient solver for stiff minimization problems.
Received July 10, 1995 / Revised version received June 27, 1996 相似文献
262.
本文得到了广义区间空间中几个参数型非空交定理,并用此结果证明了一些新型极大极小定理,截口定理,重合定理,以及变分不等式解的存在性定理。本文中的结果包含(1,3,5-12,14-16)中相应结果。 相似文献
263.
264.
Banach空间中一类非线性算子Ishikawa迭代序列收敛定理 总被引:7,自引:1,他引:6
柴国庆 《数学物理学报(A辑)》1998,18(4):459-466
在一般的Banach空间中,研究了Ishikawa迭代序列收敛问题,去掉了通常文献中关于空间X的一致光滑或S-一致光滑的严格要求,此外,还去掉或减弱了其它某些条件。因而本质地改进了近期文献的一系列相应定理。 相似文献
265.
Genkai Zhang 《manuscripta mathematica》1998,97(3):371-388
Let X=G
* be a compact Hermitian symmetric space. We study the Berezin transform on L
2(X) and calculate its spectrum under the decomposition of L
2(X) into the irreducible representations of G
*. As applications we find the expansion of powers of the canonical polynomial (Bergman reproducing kernel for the canonical
line bundle) in terms of the spherical polynomials on X, and we find the irreducible decomposition of tensor products of Bergman spaces on X.
Received: 10 September 1996 / Revised version: 10 September 1997 相似文献
266.
267.
该文讨论了形变诺振子相干态的一些有意义的性质,利用量子代数SUq(3)的形变谐振子实现,构造了SU3(q)在玻色、费米两种情况下的相干态. 相似文献
268.
269.
270.
Benjamin S. Hsiao Rong-Ming Ho Stephen Z. D. Cheng 《Journal of Polymer Science.Polymer Physics》1995,33(17):2439-2447
Unique crystallization and melting behavior in poly(aryl ether ketone ketone) containing alternated terephthalic and isophthalic moieties were studied by time-resolved synchrotron x-ray methods. Recently, this material has been shown to exhibit three polymorphs (forms I, II, and III). In this work, we further investigated their distinctive thermal properties and found that form I is the dominating and the most thermally stable phase while form II is favored by fast nucleation conditions and is the least stable phase. On the other hand, form III represents a minor intermediate phase that usually coexists with form I and can be transferred from form II and to form I. Structural and morphological changes in form I have been followed by simultaneous wide-angle x-ray diffraction (WAXD)/small-angle x-ray scattering (SAXS) measurements during cold- or melt-crystallization and subsequent melting. In all cases, a larger dimensional change was found in the crystallographic a-axis than the b-axis during heating and cooling. This may be due to the greater lateral stress variation with respect to temperature along the a direction of the primary lamellae which is induced by either the formation of secondary lamellae or the preferential chain-folding direction in poly(aryl ether ketone ketone)s. During the phase transitions of form II ← III in the cold-crystallized specimen and form III ← I in the melt-crystallized samples, lamellar variables (long period, lamellar thickness, and invariant) obtained from SAXS remain almost constant. This indicates that the density distribution in the long spacing is independent of the melting in form II or III. For melt-crystallization, the corresponding changes in unit-cell dimensions and lamellar morphology during the annealing-induced low endotherm are most consistent with the argument that these changes are due to the melting of thin lamellar population. © 1995 John Wiley & Sons, Inc. 相似文献