全文获取类型
收费全文 | 10266篇 |
免费 | 266篇 |
国内免费 | 108篇 |
专业分类
化学 | 6525篇 |
晶体学 | 100篇 |
力学 | 273篇 |
数学 | 2234篇 |
物理学 | 1508篇 |
出版年
2022年 | 76篇 |
2021年 | 85篇 |
2020年 | 117篇 |
2019年 | 137篇 |
2018年 | 123篇 |
2017年 | 75篇 |
2016年 | 215篇 |
2015年 | 198篇 |
2014年 | 228篇 |
2013年 | 558篇 |
2012年 | 528篇 |
2011年 | 603篇 |
2010年 | 385篇 |
2009年 | 331篇 |
2008年 | 492篇 |
2007年 | 506篇 |
2006年 | 580篇 |
2005年 | 559篇 |
2004年 | 497篇 |
2003年 | 385篇 |
2002年 | 401篇 |
2001年 | 131篇 |
2000年 | 118篇 |
1999年 | 110篇 |
1998年 | 130篇 |
1997年 | 128篇 |
1996年 | 168篇 |
1995年 | 113篇 |
1994年 | 93篇 |
1993年 | 99篇 |
1992年 | 99篇 |
1991年 | 86篇 |
1990年 | 72篇 |
1989年 | 74篇 |
1988年 | 60篇 |
1987年 | 77篇 |
1986年 | 66篇 |
1985年 | 115篇 |
1984年 | 139篇 |
1983年 | 100篇 |
1982年 | 109篇 |
1981年 | 130篇 |
1980年 | 150篇 |
1979年 | 105篇 |
1978年 | 114篇 |
1977年 | 89篇 |
1976年 | 101篇 |
1975年 | 110篇 |
1974年 | 102篇 |
1973年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Corinne Rondeau-Mouro Mireille Cambert Laurent Blondel Yves Diascorn Léo Mbaya Nor Nadiah Binti Ahmad Nazari Sarah Helary Tiphaine Lucas 《Magnetic resonance in chemistry : MRC》2022,60(7):678-691
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample. 相似文献
3.
Florence Drui Emmanuel Franck Philippe Helluy Laurent Navoret 《Comptes Rendus Mecanique》2019,347(3):259-269
The over-relaxation approach is an alternative to the Jin–Xin relaxation method in order to apply the equilibrium source term in a more precise way. This is also a key ingredient of the lattice Boltzmann method for achieving second-order accuracy. In this work, we provide an analysis of the over-relaxation kinetic scheme. We compute its equivalent equation, which is particularly useful for devising stable boundary conditions for the hidden kinetic variables. 相似文献
4.
Transition Metal Chemistry - (η5-Dp)Ru(PPh3)2H (Dp?=?C8H9?, 1,2-dihydropentalenyl) was synthesized in 90% yield by reaction of (η5-Dp)Ru(PPh3)2Cl with sodium formate.... 相似文献
5.
6.
Investment projects and businesses can be entered or exited at a cost, and the theory of real option teaches us how to find optimal activity levels that should trigger entry or exit. However, in practice, different managers or owners operate under different constraints and might apply different thresholds to the same business. We are interested in the hedging of the risk related to the cost of sub-optimal entry or exit. We introduce a new class of derivative products that can hedge this risk. The pricing of these derivatives involves the joint law of a Brownian excursion and its supremum, which is calculated thanks to Bessel processes-related distribution laws. 相似文献
7.
Daniel L. Feldheim Del R. Lawson Charles R. Martin 《Journal of Polymer Science.Polymer Physics》1993,31(8):953-957
We report a strong dependence of the thermal stability of Nafion® perfluorosulfonate ionomer on the nature of the counterion associated with the fixed sulfonate site. These results were obtained using thermal gravimetric analysis on a series of alkali metal and alkyl ammonium cation-exchanged Nafion films. We have found that the temperature of decomposition of Nafion is inversely dependent on the size of the exchanged cation; i.e., Nafion films show improved thermal stability as the size of the counter cation decreases. We attribute this inverse relationship of thermal stability with counterion size to an initial decomposition reaction which is strongly influenced by the strength of the sulfonate-coun-terion interaction. © 1993 John Wiley & Sons, Inc. 相似文献
8.
9.
10.
Charles J. Colbourn Sosina S. Martirosyan Gary L. Mullen Dennis Shasha George B. Sherwood Joseph L. Yucas 《组合设计杂志》2006,14(2):124-138
A covering array CA(N;t,k, v is an N × k array such that every N × t subarray contains all t‐tuples from v symbols at least once, where t is the strength of the array. Covering arrays are used to generate software test suites to cover all t‐sets of component interactions. The particular case when t = 2 (pairwise coverage) has been extensively studied, both to develop combinatorial constructions and to provide effective algorithmic search techniques. In this paper, a simple “cut‐and‐paste” construction is extended to covering arrays in which different columns (factors) admit different numbers of symbols (values); in the process an improved recursive construction for covering arrays with t = 2 is derived. © 2005 Wiley Periodicals, Inc. J Combin Designs 14: 124–138, 2006 相似文献