全文获取类型
收费全文 | 143934篇 |
免费 | 2320篇 |
国内免费 | 614篇 |
专业分类
化学 | 80951篇 |
晶体学 | 2137篇 |
力学 | 5466篇 |
综合类 | 6篇 |
数学 | 15450篇 |
物理学 | 42858篇 |
出版年
2020年 | 1085篇 |
2019年 | 1119篇 |
2018年 | 1037篇 |
2016年 | 1931篇 |
2015年 | 1622篇 |
2014年 | 1915篇 |
2013年 | 5871篇 |
2012年 | 4597篇 |
2011年 | 5798篇 |
2010年 | 3498篇 |
2009年 | 3157篇 |
2008年 | 4956篇 |
2007年 | 4939篇 |
2006年 | 5030篇 |
2005年 | 4860篇 |
2004年 | 4185篇 |
2003年 | 3727篇 |
2002年 | 3605篇 |
2001年 | 3890篇 |
2000年 | 2944篇 |
1999年 | 2439篇 |
1998年 | 2103篇 |
1997年 | 2124篇 |
1996年 | 2048篇 |
1995年 | 1978篇 |
1994年 | 1730篇 |
1993年 | 1726篇 |
1992年 | 1941篇 |
1991年 | 1870篇 |
1990年 | 1791篇 |
1989年 | 1794篇 |
1988年 | 1793篇 |
1987年 | 1782篇 |
1986年 | 1685篇 |
1985年 | 2273篇 |
1984年 | 2391篇 |
1983年 | 1978篇 |
1982年 | 2321篇 |
1981年 | 2130篇 |
1980年 | 2165篇 |
1979年 | 2150篇 |
1978年 | 2284篇 |
1977年 | 2181篇 |
1976年 | 2196篇 |
1975年 | 2126篇 |
1974年 | 1973篇 |
1973年 | 2170篇 |
1972年 | 1319篇 |
1968年 | 1084篇 |
1967年 | 1118篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
1.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献
2.
3.
Low-flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for MS have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow LC, the types of columns employed, and strategies for multidimensionality of separations, which are key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend toward biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy-to-use platform. 相似文献
4.
Theoretical and Mathematical Physics - Dynamic systems acting on the plane and possessing the Wada property have been observed. There exist only two topological types, symmetric and antisymmetric,... 相似文献
5.
6.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
7.
Ajit Kumar Singh Seulgi Ji Baghendra Singh Chittaranjan Das Heechae Choi Prashanth W. Menezes Arindam Indra 《Materials Today Chemistry》2022
Herein, we report a Mott-Schottky catalyst by entrapping cobalt nanoparticles inside the N-doped graphene shell (Co@NC). The Co@NC delivered excellent oxygen evolution activity with an overpotential of merely 248 mV at a current density of 10 mA cm–2 with promising long-term stability. The importance of Co encapsulated in NC has further been demonstrated by synthesizing Co nanoparticles without NC shell. The synergy between the hexagonal close-packed (hcp) and face-centered cubic (fcc) Co plays a major role to improve the OER activity, whereas the NC shell optimizes the electronic structure, improves the electron conductivity, and offers a large number of active sites in Co@NC. The density functional theory calculations have revealed that the hcp Co has a dominant role in the surface reaction of electrocatalytic oxygen evolution, whereas the fcc phase induces the built-in electric field at the interfaces with N-doped graphene to accelerate the H+ ion transport. 相似文献
8.
Nonlinear Dynamics - In this paper, we analyze the effect which the choice of a friction model has on tippe top inversion in the case where the resulting action of all dissipative forces is... 相似文献
9.
Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.
相似文献10.
The growth-fragmentation equation describes a system of growing and dividing particles, and arises in models of cell division, protein polymerisation and even telecommunications protocols. Several important questions about the equation concern the asymptotic behaviour of solutions at large times: at what rate do they converge to zero or infinity, and what does the asymptotic profile of the solutions look like? Does the rescaled solution converge to its asymptotic profile at an exponential speed? These questions have traditionally been studied using analytic techniques such as entropy methods or splitting of operators. In this work, we present a probabilistic approach: we use a Feynman–Kac formula to relate the solution of the growth-fragmentation equation to the semigroup of a Markov process, and characterise the rate of decay or growth in terms of this process. We then identify the Malthus exponent and the asymptotic profile in terms of a related Markov process, and give a spectral interpretation in terms of the growth-fragmentation operator and its dual. 相似文献