全文获取类型
收费全文 | 9611篇 |
免费 | 1568篇 |
国内免费 | 1296篇 |
专业分类
化学 | 7086篇 |
晶体学 | 147篇 |
力学 | 421篇 |
综合类 | 109篇 |
数学 | 1097篇 |
物理学 | 3615篇 |
出版年
2024年 | 37篇 |
2023年 | 161篇 |
2022年 | 336篇 |
2021年 | 355篇 |
2020年 | 371篇 |
2019年 | 446篇 |
2018年 | 321篇 |
2017年 | 315篇 |
2016年 | 434篇 |
2015年 | 511篇 |
2014年 | 610篇 |
2013年 | 732篇 |
2012年 | 899篇 |
2011年 | 894篇 |
2010年 | 686篇 |
2009年 | 670篇 |
2008年 | 741篇 |
2007年 | 650篇 |
2006年 | 561篇 |
2005年 | 432篇 |
2004年 | 380篇 |
2003年 | 279篇 |
2002年 | 259篇 |
2001年 | 200篇 |
2000年 | 154篇 |
1999年 | 157篇 |
1998年 | 112篇 |
1997年 | 103篇 |
1996年 | 113篇 |
1995年 | 101篇 |
1994年 | 80篇 |
1993年 | 69篇 |
1992年 | 59篇 |
1991年 | 47篇 |
1990年 | 39篇 |
1989年 | 25篇 |
1988年 | 34篇 |
1987年 | 21篇 |
1986年 | 20篇 |
1985年 | 27篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
In the present paper, a super-extension of the Yang hierarchy is proposed by super-matrix Lie algebras, and the super-Yang hierarchy with self-consistent sources is established. Furthermore, we establish infinitely many conservation laws of the super-integrable hierarchy. The methods presented by us can be generalized to other nonlinear equation hierarchies with self-consistent sources. 相似文献
82.
在缺乏特征红外振动的情况下追踪具有四极或八极对称性分子的激发态对称性破缺电荷转移通常是很困难的.本文以一种具有八极对称性的三苯胺衍生物为研究对象,利用飞秒时间分辨瞬态荧光光谱方法获得发光跃迁偶极矩的演化动力学,进而实时表征了其溶剂诱导对称性破缺电荷转移的动力学过程.当该分子处于弱极性甲苯溶液中时,在激发态弛豫过程中其发射偶极矩变化较小;当处于较强极性的四氢呋喃溶液中时,其发射偶极矩在数皮秒内快速减小.在对比单体偶极分子的荧光动力学后,推断八极分子的发光态在强极性溶剂中经历溶剂诱导的结构变化,由激子耦合的八极对称性降低至激发定域的偶极对称性;而在较弱极性的溶剂中,其八极对称性在溶剂化稳定中得以较大程度的保持. 相似文献
83.
84.
A linear optical unambiguous discrimination of hyperentangled Bell states is proposed for two‐photon systems entangled in both the polarization and momentum degrees of freedom (DOFs) assisted by time bin. This unambiguous discrimination scheme can completely identify 16 orthogonal hyperentangled Bell states using only linear optical elements, where the function of the auxiliary entangled Bell state is replaced by time bin. Moreover, the possibility of extending this scheme for distinguishing hyperentangled Bell states in n DOFs is discussed, and it shows that hyperentangled Bell states in n ( ) DOFs can be distinguished with k ( ) auxiliary entangled states of additional DOFs by introducing a time delay, which decreases the auxiliary entanglement resource required for unambiguous discrimination of hyperentangled Bell state. Therefore, this scheme provides a new way for distinguishing hyperentangled states with current technology, which will extend the application of discrimination of hyperentangled states via linear optics to other quantum information protocols besides hyperdense coding schemes in the future. 相似文献
85.
86.
This article presents an original work aimed at rationally designing molecularly imprinted polymer (MIP) toward a high specific adsorbent. Assembling with cobalt as the pivot, the MIP was prepared by coordinating polymerizable monomers around an inducible template. The use of pivot obviously plays a positive role on increasing the specificity of MIP, so as to adsorb more for the template and less for its analogue. Related studies indicate that these may be a result of increasing specific interaction, which makes the MIP capable of recognizing the imprint species. Further information from thermodynamic analysis reveals that the increasing specific interaction, in logic, can be due to a higher fidelity of imprint, which specifically allures the template to bind. 相似文献
87.
Fangqiang Fan Zhengbin Xia Qingying Li Zhong Li Huanqin Chen 《Journal of Thermal Analysis and Calorimetry》2013,114(3):937-946
Phosphorus-containing styrene–acrylic copolymers are synthesized by free radical seeded emulsion polymerization with the monomers of MMA/St/BA/MAA and phosphorus-containing vinyl monomer (SIPOMER PAM100). The properties of copolymer films are characterized by water adsorption test, thermogravimetry, Fourier transform infrared spectroscopy (FTIR), and energy dispersive spectroscopy (EDS), etc. The copolymer emulsions are used as the binder in an intumescent coatings formulation, and the fire-retardant performances of the coatings are determined by an instrument which the furnace temperature is analoging the cellulose fire temperature. The water adsorption of copolymer film increases remarkably owing to the increasing of phosphoric acid group in the polymer chain. The thermal decomposition stability and thermal-oxidative decomposition stability of the copolymer are improved when PAM100 is introduced into its chain, which is strongly supported by the FTIR and EDS results of copolymer residual treated at different temperature. The EDS results also illustrate that the fire retardancy enhanced by PAM100 during combustion owing to the condensed-phase mechanism. The fire-retardant test results show that the intumescent coatings using StA-P1.5 copolymer emulsion as the binder obtains the best fire retardant performance. We suggested that StA-P1.5 presents the lower reactivity with the acid source (APP) in 275–400 °C, and the higher reactivity with APP when the temperature is greater than 500 °C would be benefit for the swelling–charring process and the final fire retardant performance. The exorbitant crosslinking in StA-P7 brings a negative effect on the fire-retardant performance of intumescent coatings, even if it introduces a densy swollen char layer. 相似文献
88.
An approximate method has been established to calculate the depth of the potential acting on an electron in a molecule at the saddle point along a chemical bond, denoted by Dpb. It is a new indicator which can be used for predicting the strength of a chemical bond. In this work, as a practical application for demonstrating thismethod, we calculated the Dpb of deoxyribonucleosides and ribonucleosides along all C-H and N-H chemical bonds using the method. The results are in fair agreement with those results of previously reported experimental and theoretical observations. 相似文献
89.
Qiongbo Zhou Xuzhuo Sun Haibo Zhang Chunlan Xia Xiaohai Zhou 《Journal of Cluster Science》2013,24(4):969-977
A crystal structure of {H2O@CB[5]·(NH4PF6)2}·9(H2O) which consists of supramolecular chains self-assembled by water clusters and water capsules alternately was demonstrated. A water molecule is encapsulated in the cavity of CB[5] whose portals are occupied by two NH4 +, resulting in the formation of water capsule. The water clusters are made up of (H2O)4 and (H2O)5 clusters. The (H2O)4 cluster forms zigzag line and (H2O)5 features “Y-shape” structure. Moreover, anion channels consisting of six parallel supramolecular chains are occupied by PF6 ?. 相似文献
90.
Wen-Yan Ji Xiao-Li Xia Xiao-Hui Ren Fang Wang Hai-Jun Wang Kai-Sheng Diao 《Structural chemistry》2013,24(1):49-54
Ab initio calculations have been performed on the complexes of CF2Cl2 with NO and SO2, and a set of stable configurations for CF2Cl2–NO and CF2Cl2–SO2 were found with no imaginary frequencies by the MP2 method. In addition, the binding energy and the NBO analysis were used to evaluate the relative stability of the complexes. The calculated results indicate that the weak interactions in the CF2Cl2–NO and CF2Cl2–SO2 systems involved are enhanced with the increase of the number of non-covalent bonds. Further studies predict that the CF2Cl2–SO2 system may play a more important role than the CF2Cl2–NO system in environmental problem because the former offers a stronger interaction than the latter. Furthermore, the non-covalent binding interactions of Cl···N and Cl···O for CF2Cl2–NO system, Cl···O, Cl···S and F···S for CF2Cl2–SO2 system, are the dominant forces, which seem to be very significant as a driving force influencing the arrangement of molecules, especially in CF2Cl2–SO2 system. 相似文献