全文获取类型
收费全文 | 7920篇 |
免费 | 736篇 |
国内免费 | 454篇 |
专业分类
化学 | 1197篇 |
晶体学 | 6篇 |
力学 | 429篇 |
综合类 | 188篇 |
数学 | 5579篇 |
物理学 | 1711篇 |
出版年
2024年 | 14篇 |
2023年 | 79篇 |
2022年 | 200篇 |
2021年 | 241篇 |
2020年 | 190篇 |
2019年 | 224篇 |
2018年 | 165篇 |
2017年 | 285篇 |
2016年 | 334篇 |
2015年 | 197篇 |
2014年 | 434篇 |
2013年 | 687篇 |
2012年 | 386篇 |
2011年 | 413篇 |
2010年 | 362篇 |
2009年 | 486篇 |
2008年 | 493篇 |
2007年 | 453篇 |
2006年 | 403篇 |
2005年 | 390篇 |
2004年 | 306篇 |
2003年 | 259篇 |
2002年 | 254篇 |
2001年 | 213篇 |
2000年 | 212篇 |
1999年 | 213篇 |
1998年 | 190篇 |
1997年 | 139篇 |
1996年 | 122篇 |
1995年 | 103篇 |
1994年 | 84篇 |
1993年 | 68篇 |
1992年 | 63篇 |
1991年 | 62篇 |
1990年 | 46篇 |
1989年 | 32篇 |
1988年 | 24篇 |
1987年 | 41篇 |
1986年 | 22篇 |
1985年 | 50篇 |
1984年 | 30篇 |
1983年 | 20篇 |
1982年 | 20篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 20篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有9110条查询结果,搜索用时 15 毫秒
21.
C. H. Hesse 《Statistical Inference for Stochastic Processes》2007,10(1):75-95
In this work the Cauchy problem for the one-dimensional heat equation is considered. In contrast to existing literature it
is assumed that the initial state f is unknown and that information regarding f is obtained by some process of measurement. To enhance realism, both measurement errors and missing data are allowed for.
Under assumptions on f in the Fourier-domain first an approximation to f is derived from the data by means of a novel uncertainty principle. Then, it is studied how this perturbation in the initial
state propagates with time.
相似文献
22.
Lihong Wang 《Annals of the Institute of Statistical Mathematics》2004,56(2):251-264
The purpose of this paper is to investigate the asymptotic properties of the least squares estimates (L
2-estimates) and the least absolute deviation estimates (L
1-estimates) of the parameters of a nonlinear regression model subject to a set of equality and inequality restrictions, which
has a long-range dependent stationary process as its stochastic errors. Then we will compare the asymptotic relative efficiencies
of the above estimators. 相似文献
23.
林正炎 《数学物理学报(B辑英文版)》2003,23(3)
Let {X_n, n≥1} be a strictly stationary sequence of random variables, whichare either associated or negatively associated, f(·) be their common density. In this paper,the author shows a central limit theorem for a kernel estimate of f(·) under certain regularconditions. 相似文献
24.
Chin-Tsang Chiang Mei-Cheng Wang 《Annals of the Institute of Statistical Mathematics》2004,56(1):87-100
This paper proposes kernel estimation of the occurrence rate function for recurrent event data with informative censoring.
An informative censoring model is considered with assumptions made on the joint distribution of the recurrent event process
and the censoring time without modeling the censoring distribution. Under the validity of the informative censoring model,
we also show that an estimator based on the assumption of independent censoring becomes inappropriate and is generally asymptotically
biased. To investigate the asymptotic properties of the proposed estimator, the explicit form of its asymptotic mean squared
risk and the asymptotic normality are derived. Meanwhile, the empirical consistent smoothing estimator for the variance function
of the estimator is suggested. The performance of the estimators are also studied through Monte Carlo simulations. An epidemiological
example of intravenous drug user data is used to show the influence of informative censoring in the estimation of the occurrence
rate functions for inpatient cares over time. 相似文献
25.
估计死亡率分布的一个最大熵模型 总被引:1,自引:0,他引:1
本文提出了一种估计死亡率分布的新模型一最大熵模型。该模型直接从样本信息出发,不需要对待估分布的概率密度函数或先验分布作任何假定,从而克服了极大似然估计和贝叶斯估计的不足。而且通过两个例子的计算结果,表明该方法与样本数据的拟合效果要好于其它两种方法。 相似文献
26.
27.
《Electroanalysis》2004,16(9):748-756
A strategy for constructing a global multivariate calibration model that includes calibration samples measured over time on different days is developed and applied in electroanalysis. Both synthetic and real samples (tap, extracted and river water) are analyzed by differential‐pulse anodic stripping voltammetry, showing the suitability of the global model constructed that provides successful results similar to those of the usual multivariate calibration. In addition the capability of discrimination of this model is evaluated in prediction for the mean of three replicates with estimation of probability of false noncompliance, α, and false compliance, β, being found 3.1, 11.2, 6.7 and 64.7 nM for nominal concentrations of zinc, cadmium, lead and copper of 96.0, 40.4, 37.3 and 328.0 nM respectively when α=β=0.05. It has been proven that the use of the global calibration does not imply a loss of multivariate analytical sensitivity, using this parameter as quality index of the analytical procedure. The viability of using calibration maintenance strategies with electroanalytical techniques is shown, providing a way to save time and experimental effort when these techniques are used in routine analysis. 相似文献
28.
Yoshikazu Takada 《Annals of the Institute of Statistical Mathematics》1998,50(2):325-335
This paper gives a condition which implies the nonexistence of parametric statistical procedures with bounded risk or error performance characteristics. Many examples for which such a condition is satisfied are considered. 相似文献
29.
30.
无偏的岭回归迭代算法 总被引:1,自引:0,他引:1
本文探讨线性模型的无偏的岭回归迭代算法,这种算法保持最小二乘法的性质,当存在较为严重的共线性时,它能给出较为精确的参数及其协差阵的估计值;当存在严格的共线性时,给出参数及其协差阵的无穷多解中的一个,这个解由初值决定。文章还给出了算法的收敛性及一些其它性质的证明。 相似文献