全文获取类型
收费全文 | 2307篇 |
免费 | 46篇 |
国内免费 | 13篇 |
专业分类
化学 | 1284篇 |
晶体学 | 5篇 |
力学 | 70篇 |
数学 | 308篇 |
物理学 | 699篇 |
出版年
2020年 | 12篇 |
2019年 | 18篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 39篇 |
2015年 | 24篇 |
2014年 | 41篇 |
2013年 | 109篇 |
2012年 | 96篇 |
2011年 | 139篇 |
2010年 | 84篇 |
2009年 | 55篇 |
2008年 | 153篇 |
2007年 | 143篇 |
2006年 | 115篇 |
2005年 | 101篇 |
2004年 | 92篇 |
2003年 | 67篇 |
2002年 | 73篇 |
2001年 | 51篇 |
2000年 | 52篇 |
1999年 | 19篇 |
1998年 | 22篇 |
1997年 | 22篇 |
1996年 | 44篇 |
1995年 | 61篇 |
1994年 | 40篇 |
1993年 | 44篇 |
1992年 | 42篇 |
1991年 | 27篇 |
1990年 | 26篇 |
1989年 | 24篇 |
1988年 | 23篇 |
1987年 | 28篇 |
1986年 | 17篇 |
1985年 | 20篇 |
1984年 | 25篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 32篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1978年 | 24篇 |
1977年 | 24篇 |
1976年 | 29篇 |
1975年 | 26篇 |
1974年 | 17篇 |
1973年 | 21篇 |
1971年 | 15篇 |
1970年 | 12篇 |
排序方式: 共有2366条查询结果,搜索用时 15 毫秒
1.
2.
Towards a microchannel‐based X‐ray detector with two‐dimensional spatial and time resolution and high dynamic range 下载免费PDF全文
Bernhard W. Adams Anil U. Mane Jeffrey W. Elam Razib Obaid Matthew Wetstein Matthieu Chollet 《Journal of synchrotron radiation》2015,22(5):1202-1206
X‐ray detectors that combine two‐dimensional spatial resolution with a high time resolution are needed in numerous applications of synchrotron radiation. Most detectors with this combination of capabilities are based on semiconductor technology and are therefore limited in size. Furthermore, the time resolution is often realised through rapid time‐gating of the acquisition, followed by a slower readout. Here, a detector technology is realised based on relatively inexpensive microchannel plates that uses GHz waveform sampling for a millimeter‐scale spatial resolution and better than 100 ps time resolution. The technology is capable of continuous streaming of time‐ and location‐tagged events at rates greater than 107 events per cm2. Time‐gating can be used for improved dynamic range. 相似文献
3.
Early Membrane Responses to Magnetic Particles are Predictors of Particle Uptake in Neural Stem Cells 下载免费PDF全文
Alinda R. Fernandes Christopher F. Adams David N. Furness Divya M. Chari 《Particle & Particle Systems Characterization》2015,32(6):661-667
Magnetic particles (MPs) offer several advantages for neural cell therapy, but limited particle uptake by neural cells is a barrier to translation. It is recently proved that tailoring particle physicochemical properties (by enhancing their iron content) dramatically improves uptake in neural stem cells (NSCs)—a major transplant population. High‐throughput screening of particles with varying physicochemical properties can therefore aid in identifying particles with optimal uptake features, but research is hampered by the lack of simple methodologies for studying neural cell membrane responses to nanoparticle platforms. A high‐resolution–high throughput method has been used to study early membrane responses of primary rodent NSCs to particles of variant magnetite loading, to attempt to correlate these responses with known particle internalization profiles. Membrane imaging is enhanced through sequential staining with osmium (O) and thiocarbohydrazide (T), a method termed OTOTO, combined with field‐emission scanning electron microscopy (FESEM). A five‐point classification system was used to systematically evaluate early MP‐induced membrane responses to particles possessing distinct physicochemical properties. Significantly different profiles of membrane activation were noted that correlate with particle uptake profiles. It is suggested that our method can serve as a valuable predictor of particle internalization in neural cells for diverse particle platforms. 相似文献
4.
Adissu Alemayehu Asfaw Juan Aspromonte Kris Wolfs Ann Van Schepdael Erwin Adams 《Journal of separation science》2019,42(1):214-225
Sample preparation and introduction techniques are very critical steps in gas chromatography analysis and particularly in the analysis of volatiles in solid samples. In these cases, they can be divided into two main categories: direct and indirect approaches, based on how the solid sample is treated, i.e. with and without dissolution (or extraction) of analytes from the solid sample. To enable routine application, coupling with sample preparation techniques (especially solid or solvent‐based microextractions) is needed to achieve automation. Here, an overview of the most common sample introduction techniques for gas chromatography with their advantages and drawbacks is presented and discussed, including references to relevant examples. So, this review can serve as guidance for new users. 相似文献
5.
6.
Shengyun Huang Andrea Cel Erwin Adams Zdenk Glatz Ann Van Schepdael 《Journal of separation science》2020,43(17):3565-3572
Capillary electrophoresis is a modern separation technique characterized by many benefits, which qualify it also for enzyme assays and the study of enzyme kinetics during drug development. Homogeneous or heterogeneous approaches can be followed for the enzymatic incubation. In this study, an immobilization procedure of aldehyde oxidase on magnetic particles was developed considering their integration with capillary electrophoresis. A number of magnetic nano/microparticle types were tested for this purpose, showing that aldehyde oxidase was most active when immobilized on bare silica magnetic nanoparticles. Primarily, the reusability of the enzyme immobilized on bare silica nanoparticles was tested. Three consecutive incubations with substrate could be performed, but the activity considerably dropped after the first incubation. One reason could be an enzyme detachment from the nanoparticles, but no release was detected neither at 4°C nor at 37°C during 5 h. The drop in enzymatic activity observed in consecutive incubations, could also be due to inactivation of the enzyme over time at given temperature. For the immobilized enzyme stored at 4°C, the activity decreased to 83% after 5 h, in contrast with a steep decrease at 37°C to 37%. 相似文献
7.
8.
Peter De Maesschalck Freddy Dumortier Robert Roussarie 《Comptes Rendus Mathematique》2014,352(4):317-320
We introduce transitory canard cycles for slow–fast vector fields in the plane. Such cycles separate “canards without head” and “canards with head”, like for example in the Van der Pol equation. We obtain optimal upper bounds on the number of periodic orbits that can appear near the cycle under whatever condition on the related slow divergence integral I , including the challenging case I=0. 相似文献
9.
Dr. Richard D. Adams Dr. Vitaly Rassolov Yuen Onn Wong 《Angewandte Chemie (International ed. in English)》2014,53(41):11006-11009
The electronically unsaturated dirhenium complex [Re2(CO)8(µ‐AuPPh3)(µ‐Ph)] ( 1 ) was obtained from the reaction of [Re2(CO)8{µ‐η2‐C(H)?C(H)nBu}(µ‐H)] with [Au(PPh3)Ph]. The bridging {AuPPh3} group was replaced by a bridging hydrido ligand to yield the unsaturated dirhenium complex [Re2(CO)8(µ‐H)(µ‐Ph)] ( 2 ) by reaction of 1 with HSnPh3. Compound 2 reductively eliminates benzene upon addition of NCMe at 25 °C. The electronic structure of 2 and the mechanism of the reductive elimination of the benzene molecule in its reaction with NCMe were investigated by DFT computational analyses. 相似文献
10.