全文获取类型
收费全文 | 732篇 |
免费 | 92篇 |
国内免费 | 46篇 |
专业分类
化学 | 274篇 |
晶体学 | 16篇 |
力学 | 8篇 |
综合类 | 19篇 |
数学 | 43篇 |
物理学 | 510篇 |
出版年
2024年 | 6篇 |
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 13篇 |
2020年 | 27篇 |
2019年 | 36篇 |
2018年 | 19篇 |
2017年 | 26篇 |
2016年 | 27篇 |
2015年 | 33篇 |
2014年 | 53篇 |
2013年 | 87篇 |
2012年 | 40篇 |
2011年 | 31篇 |
2010年 | 35篇 |
2009年 | 27篇 |
2008年 | 36篇 |
2007年 | 42篇 |
2006年 | 38篇 |
2005年 | 33篇 |
2004年 | 25篇 |
2003年 | 35篇 |
2002年 | 33篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 18篇 |
1998年 | 16篇 |
1997年 | 12篇 |
1996年 | 23篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有870条查询结果,搜索用时 15 毫秒
121.
研究了纯相位菲涅尔计算全息图的制作方法,给出了一种生成纯相位菲涅尔计算全息图的算法.首先研究了菲涅尔衍射的数值模拟算法,分析了两种数值模拟算法的计算速度.将计算速度较快的菲涅尔衍射数值模拟算法和迭代算法相结合,并引入比例反馈,得到纯相位菲涅尔计算全息图的反馈迭代算法.其次,对比例反馈系数的选取进行了实验研究,得到其最优经验值范围,然后进行了仿真实验.仿真结果表明,该算法降低了重构误差,提高了全息图重构质量.最后基于新型空间光调制器反射型硅基液晶,建立了全息显示光电实验系统,对该算法进行了验证. 相似文献
122.
针对传统LED显示屏光能利用率和图像画面填充比低的缺点,基于非成像光学理论,提出了一种提高光能利用率和画面填充比的全彩LED显示模块结构系统和设计方法。利用复合抛物面集光器CPC对LED管芯发出光线的发散角进行变换压缩,从而避免了外表面全反射损耗,大幅度提高了系统的光能利用率。利用积分方腔匀光原理和散射元件对光能的二次分配,提高了显示屏的画面填充比、单位像素均匀度及基色复用面积。作为实例,根据上述方法设计了一个P10 mm全彩LED显示模块,利用光学设计软件LIGHTTOOLS对该显示模块系统进行了仿真建模和光线追迹,并对设计结果进行了分析。结果表明,系统光能利用率大于70%,画面填充比接近100%,单位像素区域内均匀度好于85%。显示模块具有能量利用率高、高画面填充比、显示效果均匀柔和、易于生产和装调的优点。 相似文献
123.
为满足便携式投影仪的市场需求,设计了一种基于LED微型阵列的投影系统。该系统由显示单元和投影物镜构成。采用尺寸为12 mm×9 mm的自发光LED微型阵列作为系统的显示单元,利用光学设计软件设计了投影物镜。投影物镜采用反远距光学结构,全视场角为80°,焦距为8 mm,属于强光、广角镜头。在空间频率20 lp/mm处,该物镜的调制传递函数大于0. 85,畸变小于2%,符合投影系统的设计要求。该投影系统具有体积小,结构简单,投影效果好,易加工等诸多优势,可为第三代投影技术的发展提供参考。 相似文献
124.
125.
126.
127.
V.B. Markov 《Optics & Laser Technology》1996,28(4):319-325
Possible applications of holography for cultural heritage study, demonstration and restoration, particularly in practical museum applications, are discussed. In this respect two main applications of holography are of interest: display holography and technical holography. The latter includes holographic NDT methods, three-dimensional measurements of objects, memory systems, and so on. 相似文献
128.
Affinity Chromatography of Insulin with a Heptapeptide Ligand Selected from Phage Display Library 总被引:1,自引:0,他引:1
A heptapeptide phage display library was screened with insulin to find its ligands for affinity chromatography. The peptide was synthesized and coupled to EAH Sepharose 4B (5.4 mol mL–1 bed). Then, insulin chromatography was carried out with mobile phases of different pH values and by the addition of urea and ethylene glycol. It was found that electrostatic interactions were predominant for the affinity binding, and hydrogen bonding might also contribute somewhat to the affinity. Finally, frontal analysis was performed and the dynamic binding capacity of the affinity column for insulin at 50% breakthrough was estimated at 60.6 mg mL–1 bed, which was about two times higher than the theoretical binding capacity of the monomeric insulin. The result suggests that insulin was bound in dimer state in a stoichiometric relationship with the coupled peptide, indicating the high binding efficiency of the peptide ligand for insulin. 相似文献
129.
Capacity of Bacillus thuringiensis S-layer protein displaying polyhistidine peptides on the cell surface 总被引:4,自引:0,他引:4
S-layer protein of Bacillus thuringiensis strain CTC was used as the carrier protein to display polyhistidine (poly[6His]) peptides on the cell surface. Poly(6His)
n
was fused with S-layer protein at two different sites, inserting just downstream of the S-layer protein homologous domain
(slh) and replacing the non-slh region of S-layer protein, respectively. The two series chimeric proteins were both expressed by crystal negative B. thuringiensis strain 4Q7 and strain 171, respectively, as shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The recombinant
B. thuringiensis cells gained Ni2+- and Cd2+-binding ability and had a capacity to display up to nine copies of poly(6His). The Cd2+ adsorption quantity of the recombinant strain with the strongest adsorption ability was twice that of the host strain. 相似文献
130.
Proteolytic antibodies appear to utilizecatalytic mechanisms akin to nonantibody serine proteases, assessed from mutagenesis
and protease-inhibitor studies. The catalytic efficiency derives substantially from the ability to recognize the ground state
with high affinity. Because the proteolytic activity is germline-encoded, catalysts with specificity for virtually any target
polypeptide could potentially be developed by applying appropriate immunogens and selection strategies. Analysis of transition-state
stabilizing interactions suggests that chemical reactivity ofactive-site serine residues is an important contributor to catalysis.
A prototype antigen analog capable of reacting covalently with nucleophilic serine residues permitted enrichment of the catalysts
from a phage-displayed lupus light-chain library. Further mechanistic developments in understanding proteolytic antibodies
may lead to the isolation of catalysts suitable for passive immunotherapy of major diseases, and elicitation of catalytic
immunity as a component of prophylactic vaccination. 相似文献