全文获取类型
收费全文 | 1128篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
化学 | 609篇 |
晶体学 | 5篇 |
力学 | 29篇 |
数学 | 192篇 |
物理学 | 329篇 |
出版年
2021年 | 9篇 |
2019年 | 12篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 27篇 |
2015年 | 23篇 |
2014年 | 13篇 |
2013年 | 40篇 |
2012年 | 55篇 |
2011年 | 56篇 |
2010年 | 44篇 |
2009年 | 39篇 |
2008年 | 39篇 |
2007年 | 47篇 |
2006年 | 40篇 |
2005年 | 37篇 |
2004年 | 38篇 |
2003年 | 28篇 |
2002年 | 29篇 |
2001年 | 30篇 |
2000年 | 32篇 |
1999年 | 18篇 |
1998年 | 25篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 17篇 |
1993年 | 20篇 |
1992年 | 17篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 17篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 18篇 |
1976年 | 8篇 |
1975年 | 16篇 |
1974年 | 10篇 |
1973年 | 11篇 |
1972年 | 7篇 |
1970年 | 8篇 |
1969年 | 9篇 |
排序方式: 共有1164条查询结果,搜索用时 15 毫秒
101.
Ferroelectric Liquid Crystals (FLCs) are presented which comprise charge-transfer functional groups, such that highly efficient NonLinear Optical (NLO) properties and pronounced ferroelectricity result. By operating the NLO-FLCs in one of the two Bistable states of the Short-pitch Ferroelectric (SPF) conformation, stable, planar waveguides result. The NLO-FLCs exhibit exceptionally large second-order NLO-coefficientsd
22 = 5 pm/V. Moreover, their linear electrooptical effect is shown to be essentially electronic in nature. This renders ultrafast electrooptical modulators with NLO-FLCs feasible. 相似文献
102.
The present paper summarizes and extends previous publications on magnetic recording which described a recording model, that offers the possibility of quantifying the importance of various parameters of the medium and the hardware. Within this model computer simulations of the read/write process elucidate the broad scope of magnetic recording to an extent, nonexistent so far. All computations follow or adapt common measuring procedures which facilitate the verification of our theoretical findings by comparison with experimental data. In this first of two papers the theoretical analysis applies to digital recording, only. The presented results permit objective comparisons between different techniques and media. Moreover, they yield clear statements about the feasibility for improvements of magnetic recording. 相似文献
103.
104.
Simulation von Einspiel- und Rißbildungsvorgängen in Faserverbundwerkstoffen mit metallischer Matrix
Übersicht Faserverbundstrukturen mit metallischer Matrix sind oft Belastungen ausgesetzt, die zu einer Plastifizierung der Matrix führen. Wird die Struktur zudem zyklisch belastet, so kann sie als Folge fortschreitender Plastifizierung versagen. Vor diesem Hintergrund ist besonders die Einspielneigung und die Rißbildung der Struktur von großem Interesse. In der vorliegenden Arbeit werden daher verschiedene Faser/Matrix-Kombinationen in einer numerischen Simulation untersucht. Der Zugang erfolgt dabei über die Finite-Element-Methode.
Herrn Prof. Dr.-Ing. E. h. Th. Lehmann zum 70. Geburtstag am 10. August 1990 gewidmet. 相似文献
Study of shakedown and crack initiation in fibre composites with metallic matrices
Summary Composite materials with a metal matrix are often subjected to loads which lead to plastification of the matrix. If, in addition, the structure undergoes cyclical loading, it may fail as a result of the continuing plastification. Under these circumstances, the shakedown and the crack growth of the structure are of special interest. Hence, in the present work various fibre/matrix combinations have been investigated by numerical simulation using the finite element method.
Herrn Prof. Dr.-Ing. E. h. Th. Lehmann zum 70. Geburtstag am 10. August 1990 gewidmet. 相似文献
105.
Nannocystin A: an Elongation Factor 1 Inhibitor from Myxobacteria with Differential Anti‐Cancer Properties 下载免费PDF全文
Philipp Krastel Silvio Roggo Markus Schirle Nathan T. Ross Francesca Perruccio Peter Aspesi Jr. Thomas Aust Kathrin Buntin David Estoppey Brigitta Liechty Felipa Mapa Klaus Memmert Howard Miller Xuewen Pan Ralph Riedl Christian Thibaut Jason Thomas Trixie Wagner Eric Weber Xiaobing Xie Esther K. Schmitt Dr. Dominic Hoepfner 《Angewandte Chemie (International ed. in English)》2015,54(35):10149-10154
Cultivation of myxobacteria of the Nannocystis genus led to the isolation and structure elucidation of a class of novel cyclic lactone inhibitors of elongation factor 1. Whole genome sequence analysis and annotation enabled identification of the putative biosynthetic cluster and synthesis process. In biological assays the compounds displayed anti‐fungal and cytotoxic activity. Combined genetic and proteomic approaches identified the eukaryotic translation elongation factor 1α (EF‐1α) as the primary target for this compound class. Nannocystin A ( 1 ) displayed differential activity across various cancer cell lines and EEF1A1 expression levels appear to be the main differentiating factor. Biochemical and genetic evidence support an overlapping binding site of 1 with the anti‐cancer compound didemnin B on EF‐1α. This myxobacterial chemotype thus offers an interesting starting point for further investigations of the potential of therapeutics targeting elongation factor 1. 相似文献
106.
107.
Diketopyrrolopyrrole‐Porphyrin Conjugates with High Two‐Photon Absorption and Singlet Oxygen Generation for Two‐Photon Photodynamic Therapy 下载免费PDF全文
Julie Schmitt Prof. Valérie Heitz Dr. Angélique Sour Dr. Frédéric Bolze Dr. Hussein Ftouni Prof. Jean‐Francois Nicoud Dr. Lucia Flamigni Dr. Barbara Ventura 《Angewandte Chemie (International ed. in English)》2015,54(1):169-173
Two‐photon photodynamic therapy is a promising therapeutic method which requires the development of sensitizers with efficient two‐photon absorption and singlet‐oxygen generation. Reported here are two new diketopyrrolopyrrole‐porphyrin conjugates as robust two‐photon absorbing dyes with high two‐photon absorption cross‐sections within the therapeutic window. Furthermore, for the first time the singlet‐oxygen generation efficiency of diketopyrrolopyrrole‐containing systems is investigated. A preliminary study on cell culture showed efficient two‐photon induced phototoxicity. 相似文献
108.
Phan-Xuan T Durand D Nicolai T Donato L Schmitt C Bovetto L 《Langmuir : the ACS journal of surfaces and colloids》2011,27(24):15092-15101
Stable suspensions of protein microgels are formed by heating salt-free β-lactoglobulin solutions at concentrations up to about C = 50 g·L(-1) if the pH is set within a narrow range between 5.75 and 6.1. The internal protein concentration of these spherical particles is about 150 g·L(-1) and the average hydrodynamic radius decreases with increasing pH from 200 to 75 nm. The formation of the microgels leads to an increase of the pH, which is a necessary condition to obtain stable suspensions. The spontaneous increase of the pH during microgel formation leads to an increase of their surface charge density and inhibits secondary aggregation. This self-stabilization mechanism is not sufficient if the initial pH is below 5.75 in which case secondary aggregation leads to precipitation. Microgels are no longer formed above a critical initial pH, but instead short, curved protein strands are obtained with a hydrodynamic radius of about 15-20 nm. 相似文献
109.
Destribats M Lapeyre V Sellier E Leal-Calderon F Schmitt V Ravaine V 《Langmuir : the ACS journal of surfaces and colloids》2011,27(23):14096-14107
Emulsions were prepared using poly(N-isopropylacrylamide) microgels as thermoresponsive stabilizers. The latter are well-known for their sensitivity to temperature: they are swollen by water below the so-called volume phase transition temperature (VPTT = 33 °C) and shrink when heated above it. Most of the studies reported in the literature reveal that the corresponding emulsions are of the oil-in-water type (O/W) and undergo fast destabilization upon warming above the VPTT. In the present study, whereas O/W emulsions were obtained with a wide panel of oils of variable polarity and were all thermoresponsive, water-in-oil (W/O) emulsions were found only in the presence of fatty alcohols and did not exhibit any thermal sensitivity. To understand the peculiar behavior of emulsions based on fatty alcohols, we investigated the organization of microgels at the oil-water interface and we studied the interactions of pNIPAM microgels with octanol. By combining several microscopy methods and by exploiting the limited coalescence process, we provided evidence that W/O emulsions are stabilized by multilayers of nondeformed microgels located inside the aqueous drops. Such behavior is in contradiction with the empirical Finkle rule stating that the continuous phase of the preferred emulsion is the one in which the stabilizer is preferentially dispersed. The study of microgels in nonemulsified binary water/octanol systems revealed that octanol diffused through the aqueous phase and was incorporated in the microgels. Thus, W/O emulsions were stabilized by microgels whose properties were substantially different from the native ones. In particular, after octanol uptake, they were no longer thermoresponsive, which explained the loss of responsiveness of the corresponding W/O emulsions. Finally, we showed that the incorporation of octanol modified the interfacial properties of the microgels: the higher the octanol uptake before emulsification, the lower the amount of particles in direct contact with the interface. The multilayer arrangement was thus necessary to ensure efficient stabilization against coalescence, as it increased interface cohesiveness. We discussed the origin of this counterexample of the Finkle's rule. 相似文献
110.
Functional surfaces and especially the control of surface properties depending on external parameters such as light illumination
have gained increasing importance in the last few years. We present the characterization of polymers from the cycloolefin
(co)polymer class (COC/COP) functionalized with an aminosilane as a basis for the further immobilization of compounds. In
a first step, an assay using AlexaFluor?647 fluorescent dye was used to assess surface homogeneity and reproducibility. A
coefficient of variation of less than 15% for dot-to-dot and less than 25% for chip-to-chip could be achieved. The same amino-functionalized
surfaces were then used to immobilize a biotinylated photolabile linker compound, binding AlexaFluor?647-labeled streptavidin.
The linker was photocleaved with high efficiency at λ = 365 nm and P = 0.15 mW/cm2. Fluorescence measurements show that polymers of the COC/COP class can be used as versatile surfaces for the photoinduced
release of compounds immobilized via photolabile linkers. 相似文献