全文获取类型
收费全文 | 1420篇 |
免费 | 29篇 |
国内免费 | 2篇 |
专业分类
化学 | 1047篇 |
晶体学 | 3篇 |
力学 | 17篇 |
数学 | 197篇 |
物理学 | 187篇 |
出版年
2023年 | 8篇 |
2021年 | 11篇 |
2020年 | 18篇 |
2019年 | 9篇 |
2016年 | 31篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 36篇 |
2012年 | 62篇 |
2011年 | 67篇 |
2010年 | 40篇 |
2009年 | 38篇 |
2008年 | 48篇 |
2007年 | 60篇 |
2006年 | 44篇 |
2005年 | 57篇 |
2004年 | 51篇 |
2003年 | 36篇 |
2002年 | 39篇 |
2001年 | 26篇 |
2000年 | 32篇 |
1999年 | 26篇 |
1998年 | 23篇 |
1997年 | 24篇 |
1996年 | 27篇 |
1995年 | 28篇 |
1994年 | 42篇 |
1993年 | 19篇 |
1992年 | 25篇 |
1991年 | 27篇 |
1990年 | 13篇 |
1989年 | 27篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 19篇 |
1985年 | 32篇 |
1984年 | 32篇 |
1983年 | 11篇 |
1982年 | 29篇 |
1981年 | 29篇 |
1980年 | 31篇 |
1979年 | 25篇 |
1978年 | 22篇 |
1977年 | 17篇 |
1976年 | 21篇 |
1975年 | 17篇 |
1974年 | 15篇 |
1973年 | 12篇 |
1972年 | 9篇 |
1971年 | 12篇 |
排序方式: 共有1451条查询结果,搜索用时 15 毫秒
101.
102.
Trusch M Ehlert S Bertsch A Kohlbacher O Hildebrand D Schlüter H Tallarek U 《Journal of separation science》2010,33(21):3283-3291
The influence of packing process parameters (packing pressure, application of ultrasound) and the stationary phase particle size (3.5 and 5 μm) on the chromatographic performance of HPLC/MS chips was systematically investigated for proteomic samples. First, reproducibility and detection limits of the separation were evaluated with a low‐complexity sample of tryptic BSA peptides. The influence of adsorbent packing quality on protein identification was then tested with a typical proteomics sample of high complexity, a human plasma protein fraction (Cohn fraction IV‐4). All HPLC/MS chips provided highly reproducible separations of these proteomic samples, but improved packing conditions and smaller particle sizes resulted in chromatograms with narrower peaks and correspondingly higher signal intensities. Improved separation performance increased the peak capacity, the number of identified peptides, and thus the sequence coverage in the proteomic samples, particularly for low sample amounts. 相似文献
103.
Future of diamondoids. Although the class of diamondoids has been known for many decades, the renaissance of these molecular nanodiamonds has only begun very recently. In the last century there has already been a great deal of research work and some relevant applications in the area of adamantane (rarely diamantane or triamantane) but the higher diamondoids were virtually left unexplored. The selective chemical modification of diamondoids represents a formidable scientific challenge but inherits the potential for many advances and unique applications. While other nanoscale diamond materials often have problems with size distributions and purity, diamondoids possess welldefined structures and are of high purity. Only seven years after the first isolation of higher diamondoids from crude oil we conclude that research and development in this field proceeds at an amazing pace. 相似文献
104.
In this paper we present a pneumatically driven Stewart platform as a basis for motion simulators. Motion platforms, that simulate perceived situations in aeroplanes, cars or ships, have workspace constraints in every degree of freedom. Therefore it is necessary to adapt the accelerations and angular rates in order to stay within the physical restrictions. For realizing a flight or ride simulator on the basis of the Stewart platform, “ Washout Filters” are used to change the signals of the open source software FlightGearand to minimize the sensation error between simulator and aircraft. Different filter concepts are implemented and evaluated. The platform presented in this document is a parallel kinematic robot, driven by fluidic muscles. The pneumatically actuated muscles are only able to produce tensile forces. Therefore a spiral spring from a passenger car is used to apply the compressive forces and torques. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
105.
Robert Ahrends Björn Lichtner Andreas Bertsch Oliver Kohlbacher Diana Hildebrand Maria Trusch Hartmut Schlüter 《Journal of chromatography. A》2010,1217(19):3321-3329
It was the aim of this study to compare the performance of displacement chromatography with gradient elution chromatography both applied as the cation-exchange separation step for a proteome analysis in a bottom-up approach using multidimensional chromatography for the separation of tryptic peptides prior to their mass spectrometric analysis. The tryptic digest of the human Cohn fraction IV-4 served as a sample. For both chromatography modes commonly used operating parameters were chosen thus ensuring optimal separation results of equal sample amounts for each mode. All resulting fractions were analyzed with an HPLC-chip–LC–MS system. The eluate of the HPLC-chip column was ionized by electrospray ionization (ESI) and analyzed with an ion-trap mass spectrometer. For guaranteeing high confidence concerning the identity of the peptides, the mass spectrometric data were processed by different bioinformatic tools applying stringent criteria. By the displacement approach the total amount of identified proteins (78) was significantly higher than in the gradient mode (58). The results showed that displacement chromatography is a well suited alternative in comparison to gradient elution separation for analysis of proteomes via the bottom-up approach applying multidimensional chromatography, especially in those cases when larger quantities of proteins are available. 相似文献
106.
Zeidler A Salmon PS Fischer HE Neuefeind JC Simonson JM Lemmel H Rauch H Markland TE 《Physical review letters》2011,107(14):145501
The method of oxygen isotope substitution in neutron diffraction is introduced as a site specific structural probe. It is employed to measure the structure of light versus heavy water, thus circumventing the assumption of isomorphism between H and D as used in more traditional neutron diffraction methods. The intramolecular and intermolecular O-H and O-D pair correlations are in excellent agreement with path integral molecular dynamics simulations, both techniques showing a difference of ?0.5% between the O-H and O-D intramolecular bond distances. The results support the validity of a competing quantum effects model for water in which its structural and dynamical properties are governed by an offset between intramolecular and intermolecular quantum contributions. 相似文献
107.
108.
Stefan Buschhorn Frank Brüssing Radu Abrudan Hartmut Zabel 《Journal of synchrotron radiation》2011,18(2):212-216
A new set‐up is presented to measure element‐selective magnetization dynamics using the ALICE chamber [Grabis et al. (2003), Rev. Sci. Instrum. 74 , 4048–4051] at the BESSY II synchrotron at the Helmholtz‐Zentrum Berlin. A magnetic‐field pulse serves as excitation, and the magnetization precession is probed by element‐selective X‐ray resonant magnetic scattering. With the use of single‐bunch‐generated X‐rays a temporal resolution well below 100 ps is reached. The ALICE diffractometer environment enables investigations of thin films, described here, multilayers and laterally structured samples in reflection or diffuse scattering geometry. The combination of the time‐resolved set‐up with a cryostat in the ALICE chamber will allow temperature‐dependent studies of precessional magnetization dynamics and of damping constants to be conducted over a large temperature range and for a large variety of systems in reflection geometry. 相似文献
109.
Jewart CM Chen T Lindner E Fiebrandt J Rothhardt M Schuster K Kobelke J Bartelt H Chen KP 《Optics letters》2011,36(23):4491-4493
This Letter presents simulation and experimental results that explore bending insensitivity of fiber Bragg gratings in suspended-core optical fibers. The implementation of thin silica bridge in the fibers enhances index contrast of the fiber core and reduces bending-induced strain transfer to the fiber core. This fiber design lead to a reduction of over 7 times in strain-induced fiber Bragg grating resonant peak shifts in the suspended-core fiber compared with that in standard telecommunication fiber, and an 0.14 dB bending loss at a bending radius of 6.35 mm. 相似文献
110.