全文获取类型
收费全文 | 11707篇 |
免费 | 1259篇 |
国内免费 | 829篇 |
专业分类
化学 | 4040篇 |
晶体学 | 113篇 |
力学 | 3065篇 |
综合类 | 115篇 |
数学 | 2160篇 |
物理学 | 4302篇 |
出版年
2024年 | 8篇 |
2023年 | 99篇 |
2022年 | 162篇 |
2021年 | 227篇 |
2020年 | 360篇 |
2019年 | 260篇 |
2018年 | 267篇 |
2017年 | 341篇 |
2016年 | 406篇 |
2015年 | 340篇 |
2014年 | 597篇 |
2013年 | 724篇 |
2012年 | 546篇 |
2011年 | 724篇 |
2010年 | 540篇 |
2009年 | 722篇 |
2008年 | 704篇 |
2007年 | 802篇 |
2006年 | 719篇 |
2005年 | 595篇 |
2004年 | 557篇 |
2003年 | 551篇 |
2002年 | 436篇 |
2001年 | 392篇 |
2000年 | 379篇 |
1999年 | 329篇 |
1998年 | 285篇 |
1997年 | 221篇 |
1996年 | 191篇 |
1995年 | 172篇 |
1994年 | 155篇 |
1993年 | 131篇 |
1992年 | 122篇 |
1991年 | 122篇 |
1990年 | 93篇 |
1989年 | 55篇 |
1988年 | 55篇 |
1987年 | 56篇 |
1986年 | 47篇 |
1985年 | 38篇 |
1984年 | 39篇 |
1983年 | 22篇 |
1982年 | 40篇 |
1981年 | 23篇 |
1980年 | 37篇 |
1979年 | 42篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1973年 | 9篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Hidetoshi Shimodaira 《Annals of the Institute of Statistical Mathematics》1997,49(3):395-410
The asymptotic error probability of Linhart's model selection test isevaluated, and compared with the nominal significance level. We examine thecase where the expected discrepancies of the candidate models from the truemodel are asymptotically equal. The local alternatives method is employed inthe limiting operation of the asymptotic evaluation. Although the errorprobability under the null hypothesis is actually shown to be equal to orless than the level for most situations, intolerable violations of the errorcontrol are observed for nested models: It is often erroneously concludedthat the smaller model is significantly better than the larger model. Toprevent this violation, a modification of Linhart's test statistic isproposed. The effectiveness of the proposed test is confirmed throughtheoretical analysis and numerical simulations. 相似文献
62.
Fusion-evaporation cross-sections for the α-induced reactions upon197Au,193Ir,191Ir,185Re,181Ta,121Sb and69Ga nuclei at bombarding energies near the Coulomb barrier have been measured by off-line observation of the γ-rays emitted
in the radioactive decay of the residual nuclei using stacked foil technique. The total fusion cross-section for the systems
have been compared with simple statistical model calculations using the code ALICE/91 as well as with the coupled channel
calculations that include the β2 and ν4 slatic deformations and dynamic couplings of the vibrational/rotational states of the target and the projet tile using the
code CCDEF. 相似文献
63.
Structural characterisation of such bio-objects as fibrinogen solution, yeast cells, wheat seeds and bone tissues has been done using two versions of cryoporometry based on the integral Gibbs-Thomson (IGT) equation for freezing point depression of pore liquids and the measurements by 1H NMR spectroscopy (180-200 < T < 273 K) and the thermally stimulated depolarisation current (TSDC) method (90 < T < 273 K) of structured water. The IGT equation was solved using a self-consisting regularization procedure including the maximum entropy principle applied to the distribution function of pore size (PSD). Both methods give clear pictures of changes in the structural characteristics caused, e.g., by hydration and swelling of wheat seeds and yeast cells, coagulation and interaction of fibrinogen with solid nanoparticles in the aqueous media, and the human bone tissue disease. 相似文献
64.
等腰三角形Mindlin板的自由振动分析 总被引:2,自引:0,他引:2
提出了一种新方法来对基于 Mindlin剪切变形理论的等腰三角形板进行自由振动分析 .此方法采用了一种新的基函数并利用 pb-2 Rayleigh-Ritz边界函数得到了一种新型的 Ritz方法 .这种方法的有效性通过收敛性和对比性分析得到了证实 .数值结果表明此方法相当精确有效 . 相似文献
65.
The surgery obstruction of a normal map to a simple Poincaré pair (X, Y) lies in the relative surgery obstruction group L *(π 1(Y) → π 1(X)). A well-known result of Wall, the so-called π-π-theorem, states that in higher dimensions a normal map of a manifold with boundary to a simple Poincaré pair with π 1(X) ? π 1(Y) is normally bordant to a simple homotopy equivalence of pairs. In order to study normal maps to a manifold with a submanifold, Wall introduced the surgery obstruction groups LP * for manifold pairs and splitting obstruction groups LS *. In the present paper, we formulate and prove for manifold pairs with boundary results similar to the π-π-theorem. We give direct geometric proofs, which are based on the original statements of Wall’s results and apply obtained results to investigate surgery on filtered manifolds. 相似文献
66.
67.
1 Introduction Inrecentyears,boththetheoreticalandexperimentalinvestigationsonlasercoolingandtrappinghavebecomeoneofthemajorfieldsinatomic,molecularandoptical physics[1~ 8] .Thedevelopmentoflasercoolingandtrappingtechnologyisimportantfortheapplicationssu… 相似文献
68.
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
69.
70.
Optical trapping forces of polystyrene microspheres are analyzed both theoretically and experimentally, and comparisons are
made between the two. Discrepancies are mainly caused by straight-ray approximation for axial trapping, and by trapping-position
vertical displacement due to gravity for transverse trapping. 相似文献