全文获取类型
收费全文 | 3299篇 |
免费 | 388篇 |
国内免费 | 178篇 |
专业分类
化学 | 910篇 |
晶体学 | 2篇 |
力学 | 135篇 |
综合类 | 21篇 |
数学 | 880篇 |
物理学 | 532篇 |
无线电 | 1385篇 |
出版年
2024年 | 4篇 |
2023年 | 43篇 |
2022年 | 66篇 |
2021年 | 86篇 |
2020年 | 97篇 |
2019年 | 76篇 |
2018年 | 67篇 |
2017年 | 121篇 |
2016年 | 123篇 |
2015年 | 121篇 |
2014年 | 162篇 |
2013年 | 313篇 |
2012年 | 221篇 |
2011年 | 220篇 |
2010年 | 196篇 |
2009年 | 178篇 |
2008年 | 155篇 |
2007年 | 222篇 |
2006年 | 169篇 |
2005年 | 145篇 |
2004年 | 158篇 |
2003年 | 130篇 |
2002年 | 97篇 |
2001年 | 92篇 |
2000年 | 80篇 |
1999年 | 94篇 |
1998年 | 60篇 |
1997年 | 53篇 |
1996年 | 45篇 |
1995年 | 46篇 |
1994年 | 36篇 |
1993年 | 29篇 |
1992年 | 24篇 |
1991年 | 24篇 |
1990年 | 5篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有3865条查询结果,搜索用时 15 毫秒
1.
Elise Laszlo Gregory De Crescenzo Alfonso Nieto-Argüello Xavier Banquy Davide Brambilla 《Advanced functional materials》2021,31(46):2106061
The noninvasive sampling of dermal interstitial fluid (ISF) for the monitoring of clinical biomarkers is a greatly appealing area of research. The identification of molecular biomarkers in biological fluids has been accelerated with -omics analyses but remains limited in ISF because of its time-consuming and complex extraction process. Here, the generation of microneedle (MN) patches made of superabsorbent acrylate-based hydrogels for the rapid sampling of dermal ISF is described to explore its proteome. In depth, iterative optimization allows the identification of novel acrylate-based compositions with the required chemical, mechanical, and biocompatibility properties allowing proteomic analysis of the extracted ISF for the first time after sampling with swelling MNs. The generated MN arrays show no cytotoxic effect, successfully cross the stratum corneum, and can collect up to 6 µL of dermal ISF in 10 min in vivo. Proteomics lead to the detection of 176 clinically relevant biomarkers in the collected samples validating the use of ISF as a relevant bodily fluid for disease monitoring and diagnostic. Importantly, it is discovered that extraction fingerprint is strongly dependent on the MNs chemistry, and thus specific biomarkers could be selectively extracted by tuning the composition of the patch, making the system versatile and specific. 相似文献
2.
Mariusz Marć Marek Tobiszewski Bożena Zabiegała Miguel de la Guardia Jacek Namieśnik 《Analytica chimica acta》2015
This review summarizes the different tools and concepts that are commonly applied in air quality monitoring. The monitoring of atmosphere is extremely important as the air quality is an important problem for large communities. Main requirements for analytical devices used for monitoring include a long period of autonomic operation and portability. These instruments, however, are often characterized by poor analytical performance. Monitoring networks are the most common tools used for monitoring, so large-scale monitoring programmes are summarized here. Biomonitoring, as a cheap and convenient alternative to traditional sample collection, is becoming more and more popular, although its main drawback is the lack of standard procedures. Telemonitoring is another approach to air monitoring, which offers some interesting opportunities, such as ease of coverage of large or remote areas, constituting a complementary approach to traditional strategies; however, it requires huge costs. 相似文献
3.
4.
在数据采集中采用带通采样,可大大降低采样率,但系统中的抗混叠滤波器会造成相位的非线性。采用对滤波后的信号进行带通采样,然后再用FRR滤波器校正相位的非线性,从而不失真地还原原信号,最后在Matlab中进行仿真,验证了该方法的有效性。 相似文献
5.
6.
可变抽样区间的非参数控制图 总被引:1,自引:1,他引:0
最近几年一些学者研究了可变抽样区间的质量控制图。Amin等提出了可变抽样区间(VSI)的非参数控制图———符号 (Sign)统计量图〔1〕。本文在此基础上研究位置VSI符号控制图的制定方法 ,并设计离散VSI符号控制图。符号控制图的优点是对非正态总体亦可应用 ,并且不需要过程方差的信息。本文将所设计的VSI符号控制图同固定抽样区间 (FSI)的常规图作比较 ,并举实例说明符号控制图的应用 相似文献
7.
8.
Let {Xk}k?1 be a strictly stationary time series. For a strictly increasing sampling function g:?→? define Yk=Xg(k) as the deterministic sub‐sampled time series. In this paper, the extreme value theory of {Yk} is studied when Xk has representation as a moving average driven by heavy‐tailed innovations. Under mild conditions, convergence results for a sequence of point processes based on {Yk} are proved and extremal properties of the deterministic sub‐sampled time series are derived. In particular, we obtain the limiting distribution of the maximum and the corresponding extremal index. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
Omer Ozturk Steven N. MacEachern 《Annals of the Institute of Statistical Mathematics》2004,56(4):701-720
We develop a method of randomizing units to treatments that relies on subjective judgement or on possible coarse modeling
to produce restrictions on the randomization. The procedure thus fits within the general framework of ranked set sampling.
However, instead of selecting a single unit from each set for full measurement, all units within a set are used. The units
within a set are assigned to different treatments. Such an assignment translates the positive dependence among units within
a set into a reduction in variation of contrasting features of the treatments.
A test for treatment versus control comparison, with controlled familywise error rate, is developed along with the associated
confidence intervals. The new procedure is shown to be superior to corresponding procedures based on completely randomized
or ranked set sample designs. The superiority appears both in asymptotic relative efficiency and in power for finite sample
sizes. Importantly, this test does not rely on perfect rankings; rather, the information in the data on the quality of rankings
is exploited to maintain the level of the test when rankings are imperfect. The asymptotic relative efficiency of the test
is not affected by estimation of the quality of rankings, and the finite sample performance is only mildly affected. 相似文献
10.