全文获取类型
收费全文 | 14304篇 |
免费 | 2603篇 |
国内免费 | 2280篇 |
专业分类
化学 | 10958篇 |
晶体学 | 265篇 |
力学 | 923篇 |
综合类 | 170篇 |
数学 | 1675篇 |
物理学 | 5196篇 |
出版年
2024年 | 63篇 |
2023年 | 376篇 |
2022年 | 693篇 |
2021年 | 634篇 |
2020年 | 737篇 |
2019年 | 699篇 |
2018年 | 583篇 |
2017年 | 537篇 |
2016年 | 708篇 |
2015年 | 743篇 |
2014年 | 850篇 |
2013年 | 1085篇 |
2012年 | 1292篇 |
2011年 | 1296篇 |
2010年 | 851篇 |
2009年 | 860篇 |
2008年 | 1002篇 |
2007年 | 860篇 |
2006年 | 731篇 |
2005年 | 660篇 |
2004年 | 472篇 |
2003年 | 427篇 |
2002年 | 413篇 |
2001年 | 357篇 |
2000年 | 301篇 |
1999年 | 274篇 |
1998年 | 221篇 |
1997年 | 203篇 |
1996年 | 218篇 |
1995年 | 185篇 |
1994年 | 160篇 |
1993年 | 129篇 |
1992年 | 115篇 |
1991年 | 92篇 |
1990年 | 81篇 |
1989年 | 54篇 |
1988年 | 43篇 |
1987年 | 42篇 |
1986年 | 26篇 |
1985年 | 33篇 |
1984年 | 18篇 |
1983年 | 21篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1957年 | 5篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
2.
3.
Pengjin Qin Li-An Wang Prof. Joseph M. O'Connor Prof. Kim K. Baldridge Yifan Li Burak Tufekci Jiyue Chen Prof. Arnold L. Rheingold 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18114-18121
Triene 6π electrocyclization, wherein a conjugated triene undergoes a concerted stereospecific cycloisomerization to a cyclohexadiene, is a reaction of great historical and practical significance. In order to circumvent limitations imposed by the normally harsh reaction conditions, chemists have long sought to develop catalytic variants based upon the activating power of metal–alkene coordination. Herein, we demonstrate the first successful implementation of such a strategy by utilizing [(C5H5)Ru(NCMe)3]PF6 as a precatalyst for the disrotatory 6π electrocyclization of highly substituted trienes that are resistant to thermal cyclization. Mechanistic and computational studies implicate hexahapto transition-metal coordination as responsible for lowering the energetic barrier to ring closure. This work establishes a foundation for the development of new catalysts for stereoselective electrocyclizations. 相似文献
4.
5.
Qin Yin Shou-Guo Wang Xiao-Wei Liang De-Wei Gao Jun Zheng Shu-Li You 《Chemical science》2015,6(7):4179-4183
An organocatalytic asymmetric chlorinative dearomatization of naphthols was realized for the first time, providing chiral naphthalenones with a Cl-containing all-substituted stereocenter in excellent yields and enantioselectivity (up to 97% yield and 96% ee). The reaction features mild reaction conditions, good tolerance of diverse functional groups and simple reaction operation. 相似文献
6.
讨论一类非齐次非线性椭圆边界值问题.利用极大值原理证明了该问题解的梯度估计.作为它的应用得到了解的效率比估计. 相似文献
7.
8.
Hierarchical motion planning at the acceleration level based on task priority matrix for space robot
Nonlinear Dynamics - A capacitive micromachined ultrasonic transducer (CMUT) due to many benefits is being considered as an imaging and therapeutic technology recently. The critical challenge is to... 相似文献
9.
Xiaoshuang Luo Xinxian Qin Zhengyi Liu Dan Chen Weiwei Yu Kankan Zhang Deyu Hu 《Biomedical chromatography : BMC》2020,34(1):e4694
A simple and rapid analytical method for the detection of trifloxystrobin, trifloxystrobin acid and tebuconazole in soil, brown rice, paddy plants and rice hulls was established and validated by liquid chromatography with tandem mass spectrometry. Acceptable linearity (R2 > 0.99), accuracy (average recoveries of 74.3–108.5%) and precision (intra- and inter-day relative standard deviations of 0.9–8.8%) were obtained using the developed determination approach. In the field trial, the half-lives of trifloxystrobin and tebuconazole in paddy plants were 5.7–8.3 days in three locations throughout China, and the terminal residue concentrations of trifloxystrobin and tebuconazole were <100 and 500 μg/kg (maximum residue limits set by China), respectively, at harvest, which indicated that, based on the recommended application procedure, trifloxystrobin and tebuconazole are safe for use on rice. The risk assessment results demonstrated that, owing to risk quotient values of both fungicides being <100%, the potential risk of trifloxystrobin and tebuconazole on rice was acceptable for Chinese consumers. These data could provide supporting information for the proper use and safety evaluation of trifloxystrobin and tebuconazole in rice. 相似文献
10.
Nonclassical light states are important for both conceptual and practical reasons: they are basic ingredients in testing and exploring quantum foundations, and are crucial resources in quantum technologies. Various useful criteria have been developed to detect nonclassicality in the literature, and several meaningful measures of nonclassicality have been introduced and measured experimentally. In this work, by use of a non-Hermitian generalization of the Wigner-Yanase-Dyson skew information and playing with operator ordering in evaluating average photon number, we develop a novel family of criteria for detecting nonclassicality of light based on Lieb's concavity, which is a deep and powerful result concerning interaction between quantum states and observables. We elucidate the information-theoretic as well as the physical meaning of the criteria, and illustrate their effectiveness in capturing and quantifying nonclassicality of various important light states. 相似文献