全文获取类型
收费全文 | 187篇 |
免费 | 12篇 |
国内免费 | 11篇 |
专业分类
化学 | 92篇 |
晶体学 | 1篇 |
力学 | 15篇 |
综合类 | 1篇 |
数学 | 20篇 |
物理学 | 81篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 20篇 |
2012年 | 13篇 |
2011年 | 9篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 15篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有210条查询结果,搜索用时 531 毫秒
101.
Many biotechniques including protein microarray, drug screening, biosensors rely on the immobilization of recombinant proteins on the solid supports. It is well known that random orientation of the immobilized proteins could impair their biologic functions. Thus, it is very important to develop new site‐specific immobilization approach. In this study, we presented a chemoenzymatic approach for site‐specific conjugation of recombinant proteins onto solid support. In this strategy, the affinity tag on recombinant protein was enzymatically cleaved to expose the N‐terminal serine, which was oxidized to carry an aldehyde group and was then covalently coupled to hydrazide resin through hydrazone ligation. As this approach takes advantage of the most frequently used TEV protease, it requires no further sequence design on recombinant protein. This method was validated by site specific coupling of a synthetic peptide and a recombinant protein onto solid supports. It was found that the site specific immobilized SH2 domain is functional and could be used to enrich tyrosine phosphorylated peptides. 相似文献
102.
Understanding the effect of guest species on the host framework is important for the development of structure-based properties of inclusion compounds. Herein, the crystal structures of the noble gas hydrates encapsulating Xe, Kr, and Ar were studied by powder X-ray diffraction measurements. The crystal structures and hydration numbers of these noble gas hydrates were solved by Rietveld refinements using optimized models with the direct-space technique. It was revealed that host cage size of these hydrates changed depending on the type of guest species even though their unit-cell parameters were the same. Based on the structure models obtained, the densities of Xe, Kr, and Ar gas hydrates were also determined to be 1.837, 1.445 and 1.097 g/cm3 at 93 K, respectively. Our findings, from a crystallographic point of view, may give insight into further understanding the thermodynamic stability and physical properties of gas hydrates encapsulating small guests. 相似文献
103.
采用高温固相法制备一系列Sr2SiO4∶Eu0.01, Dyx(x=0.000 1, 0.002 5, 0.005, 0.01)应力发光材料,研究了不同掺杂浓度下,Sr2SiO4∶Eu, Dy的光致发光和应力发光性质。研究结果表明在掺杂Dy3+浓度较低时,样品同时存在α和β两种相,当掺杂Dy3+浓度增加时,则出现β到α的相转变。由于Eu2+占据Sr2+格位的不同,样品在蓝光区486 nm(Sr1)和绿光区530 nm(Sr2)有两个峰存在。而应力发光光谱与余辉光谱类似,均只呈现出530 nm的发光,这说明二者的发光来源于占据Sr2格位的Eu2+,都是通过改变陷阱的浓度实现发光性能的变化,但Sr2SiO4∶Eu, Dy的应力发光强度的变化还与其结构改变有关。同时,Sr2SiO4∶Eu, Dy应力发光强度与所施加的力之间呈良好的线性关系,并且可用眼睛观察到明显的黄色应力发光,这为应力发光传感器准确检测物体所受应力提供依据。结合余辉、热释以及应力发光性质,推测Sr2SiO4∶Eu, Dy的应力发光机制应是压电产生的电致发光。 相似文献
104.
First-principles calculations based upon the density functional theory have been carried out to investigate the alloying effects and site occupancies of Re in the C14 XCr2 (X?=?Nb, Ta, Ti, Zr, Hf) Laves phases. The calculated results indicate that Re tends to facilitate and participate in the formation of the Laves phases, generating X8Cr15Re accordingly. The partial density of states and charge density di?erence were analysed to re?ect the bonding characteristics. For X8Cr15Re, the bonding between the doped Re and its nearest neighbour Cr atoms all show covalent characteristics, which contribute to the phase stability. The substitution of Re on X sites is energetically unfavourable due to the weak bonding between Re and its nearest neighbour X atoms. 相似文献
105.
Three examples of the electrochemical deposition of intermetallic phases are shown. Electrodeposition of the single-phase -brass superlattice at underpotentials of Zn in Cu-Zn alloy plating is explained by an accumulative underpotential deposition (UPD) mechanism. Growth of the Cu-Sn intermetallic phase layer in the contact immersion deposition of Sn onto Cu is accounted for by a UPD/vertical solid-state diffusion mechanism. Ag3Sn formation in the Sn/Ag-nanoparticle composite plating is illustrated by atomic site exchange at the interface between the deposited Sn matrix and the occluded Ag nanoparticles. 相似文献
106.
Kitamura K Omran AA Takegami S Tanaka R Kitade T 《Analytical and bioanalytical chemistry》2007,387(8):2843-2848
The interaction of a non-steroidal anti-inflammatory drug, niflumic acid (NFA), with human serum albumin (HSA) has been investigated
by 19F nuclear magnetic resonance (NMR) spectroscopy. A 19F NMR spectrum of NFA in a buffered (pH 7.4) solution of NaCl (0.1 mol L−1) contained a single sharp signal of its CF3 group 14.33 ppm from the internal reference 2,2,2-trifluoroethanol. Addition of 0.6 mmol L−1 HSA to the NFA buffer solution caused splitting of the CF3 signal into two broadened signals, shifted to the lower fields of 14.56 and 15.06 ppm, with an approximate intensity ratio
of 1:3. Denaturation of HSA by addition of 3.0 mol L−1 guanidine hydrochloride (GU) restored a single sharp signal of CF3 at 14.38 ppm, indicating complete liberation of NFA from HSA as a result of its denaturation. These results suggest that
the binding is reversible and occurs in at least two HSA regions. Competitive 19F NMR experiments using warfarin, dansyl-l-asparagine, and benzocaine (site I ligands), and l-tryptophan and ibuprofen (site II ligands) revealed that NFA binds to site I at two different regions, Ia and Ib, in the
ratio 1:3. By use of 19F NMR with NFA as an 19F NMR probe the nonfluorinated site I-binding drugs sulfobromophthalein and iophenoxic acid were also found to bind sites
Ia and Ib, respectively. These results illustrate the usefulness and convenience of 19F NMR for investigation of the HSA binding of both fluorinated and nonfluorinated drugs. 相似文献
107.
在损毁城镇震后恢复重建工作中,场址的合理选择及安全性评估极为重要。选址问题涉及地震断裂、地质灾害、场地稳定及国计民生、经济发展等诸方面的复杂因素,是一个复杂的系统工程问题。考虑问题的基本原则应是,对于震后位于地震断裂带上,且地质环境恶化、存在严重地质灾害隐患的城镇,必须异地迁建;对于虽然损毁较严重,但远离断裂带,且不存在致命的地质灾害隐患的城镇,应按照"科学规划、规范避让、合理调整抗震设防标准"的原则,原址重建。灾后重建过程中,应重视地质灾害的隐蔽性、诱发因素的多重性与长期持续性等,加强地质环境的适宜性评价及地质灾害的风险性评估。本文结合震后的实际调查,对北川、青川两个县城及青川县木鱼镇的重建选址问题进行了探讨,在对场址工程地质和环境地质适宜性评估的基础上,提出了上述典型城镇的重建选址意见。 相似文献
108.
On a Two-Queue Priority System with Impatience and its Application to a Call Center* 总被引:5,自引:0,他引:5
We consider an s-server priority system with a protected and an unprotected queue. The arrival rates at the queues and the service rate may depend on the number n of customers being in service or in the protected queue, but the service rate is assumed to be constant for n > s. As soon as any server is idle, a customer from the protected queue will be served according to the FCFS discipline. However, the customers in the protected queue are impatient. If the offered waiting time exceeds a random maximal waiting time I, then the customer leaves the protected queue after time I. If I is less than a given deterministic time, then he leaves the system, else he will be transferred by the system to the unprotected queue. The service of a customer from the unprotected queue will be started if the protected queue is empty and more than a given number of servers become idle. The model is a generalization of the many-server queue with impatient customers. The global balance conditions seem to have no explicit solution. However, the balance conditions for the density of the stationary state process for the subsystem of customers being in service or in the protected queue can be solved. This yields the stability conditions and the probabilities that precisely n customers are in service or in the protected queue. For obtaining performance measures for the unprotected queue, a system approximation based on fitting impatience intensities is constructed. The results are applied to the performance analysis of a call center with an integrated voice-mail-server. 相似文献
109.
110.
用极限动力学模型研究了C60分子在有序-无序相变和玻璃态相变温度区间取向角为98°和38°的取向概率与温度的关系.计算结果在玻璃态相变点附近的85!K,90!K和有序-无序相变点的260!K分别与实验值相吻合,取向概率对实验值更精确的拟合及其对温度的二阶导数预言玻璃态相变点在84!K.导出了弛豫规律,其结果表明:双能级的C60分子从非平衡态到平衡态的弛豫行为与非指数因子β有关,其总的弛豫时间决定于其中一个较短的弛豫时间,展宽指数形式保持不变.讨论了KWW方程的非指数因子β与分子间协同作用的关系,发现与双取向态间的能级差有关,计算值与实验结果相同. 相似文献