全文获取类型
收费全文 | 9353篇 |
免费 | 820篇 |
国内免费 | 553篇 |
专业分类
化学 | 1977篇 |
晶体学 | 46篇 |
力学 | 247篇 |
综合类 | 79篇 |
数学 | 1857篇 |
物理学 | 1862篇 |
无线电 | 4658篇 |
出版年
2024年 | 23篇 |
2023年 | 78篇 |
2022年 | 89篇 |
2021年 | 151篇 |
2020年 | 206篇 |
2019年 | 223篇 |
2018年 | 179篇 |
2017年 | 253篇 |
2016年 | 267篇 |
2015年 | 326篇 |
2014年 | 550篇 |
2013年 | 635篇 |
2012年 | 546篇 |
2011年 | 612篇 |
2010年 | 429篇 |
2009年 | 480篇 |
2008年 | 573篇 |
2007年 | 616篇 |
2006年 | 593篇 |
2005年 | 460篇 |
2004年 | 417篇 |
2003年 | 449篇 |
2002年 | 368篇 |
2001年 | 314篇 |
2000年 | 277篇 |
1999年 | 262篇 |
1998年 | 233篇 |
1997年 | 172篇 |
1996年 | 149篇 |
1995年 | 125篇 |
1994年 | 86篇 |
1993年 | 84篇 |
1992年 | 76篇 |
1991年 | 67篇 |
1990年 | 38篇 |
1989年 | 41篇 |
1988年 | 32篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 21篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 25篇 |
1981年 | 15篇 |
1980年 | 26篇 |
1979年 | 25篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1974年 | 3篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
41.
42.
43.
On‐Line Monitoring of Chemical Reactions by using Bench‐Top Nuclear Magnetic Resonance Spectroscopy 下载免费PDF全文
Dr. E. Danieli Dr. J. Perlo Dr. A. L. L. Duchateau G. K. M. Verzijl Dr. V. M. Litvinov Prof. Dr. B. Blümich Dr. F. Casanova 《Chemphyschem》2014,15(14):3060-3066
Real‐time nuclear magnetic resonance (NMR) spectroscopy measurements carried out with a bench‐top system installed next to the reactor inside the fume hood of the chemistry laboratory are presented. To test the system for on‐line monitoring, a transfer hydrogenation reaction was studied by continuously pumping the reaction mixture from the reactor to the magnet and back in a closed loop. In addition to improving the time resolution provided by standard sampling methods, the use of such a flow setup eliminates the need for sample preparation. Owing to the progress in terms of field homogeneity and sensitivity now available with compact NMR spectrometers, small molecules dissolved at concentrations on the order of 1 mmol L?1 can be characterized in single‐scan measurements with 1 Hz resolution. Owing to the reduced field strength of compact low‐field systems compared to that of conventional high‐field magnets, the overlap in the spectrum of different NMR signals is a typical situation. The data processing required to obtain concentrations in the presence of signal overlap are discussed in detail, methods such as plain integration and line‐fitting approaches are compared, and the accuracy of each method is determined. The kinetic rates measured for different catalytic concentrations show good agreement with those obtained with gas chromatography as a reference analytical method. Finally, as the measurements are performed under continuous flow conditions, the experimental setup and the flow parameters are optimized to maximize time resolution and signal‐to‐noise ratio. 相似文献
44.
Yufei Shu Dr. Xing Lin Dr. Haiyan Qin Zhuang Hu Prof. Yizheng Jin Prof. Xiaogang Peng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22496-22507
This article offers a materials-chemistry perspective for colloidal quantum dots (QDs) in the field of display, including QD-enhanced liquid-crystal-display (QD-LCD) and QD-based light-emitting-diodes (QLEDs) display. The rapid successes of QDs for display in the past five years are not accidental but have a deep root in both maturity of their synthetic chemistry and their unique chemical, optical, and optoelectronic properties. This article intends to discuss the natural match of QD emitters for display and chemical means to eventually bring about their full potential. 相似文献
45.
Frantiek Rybnik 《Journal of Polymer Science.Polymer Physics》1996,34(11):1935-1940
Thin film polymerization/crystallization of poly-4-oxybenzoate (P-4-OB) from melt or dilute solutions yields on mica cleavage surface an epitaxial overgrowth with crystal blocks oriented in 1 to 3 substrate directions rotated by 60°. The b and c crystal axes of P-4-OB lie in the mica cleavage plane, with the a axis being perpendicular to it. At higher polymerization temperatures a different type of P-4-OB orientation on mica was also observed: two P-4-temperatures a different type of P-4-OB orientation on mica was also observed: two P-4-OB phase I crystals, again with b- and c-axes lying parallel to mica cleavage plane, were oriented perpendicular to each other. There is a pronounced tendency of the relatively thick P-4-OB overgrowth to form complex crystal structures involving both phase I and II with different types of orientation on mica substrate. © 1996 John Wiley & Sons, Inc. 相似文献
46.
Mario S. Valds-Tresanco Andrea Molina-Zapata Alaín Gonzlez Pose Ernesto Moreno 《Molecules (Basel, Switzerland)》2022,27(7)
Single domain antibodies from camelids, or nanobodies, are a unique class of antibody fragments with several advantageous characteristics: small monomeric size, high stability and solubility and easy tailoring for multiple applications. Nanobodies are gaining increasing acceptance as diagnostic tools and promising therapeutic agents in cancer and other diseases. While most nanobodies are obtained from immunized animals of the camelid family, a few synthetic nanobody libraries constructed in recent years have shown the capability of generating high quality nanobodies in terms of affinity and stability. Since this synthetic approach has important advantages over the use of animals, the recent advances are indeed encouraging. Here we review over a dozen synthetic nanobody libraries reported so far and discuss the different approaches followed in their construction and validation, with an emphasis on framework and hypervariable loop design as critical issues defining their potential as high-class nanobody sources. 相似文献
47.
翁寿松 《电子工业专用设备》2007,36(3):11-13
介绍了系统级芯片(SoC)、可制造性设计(DFM)和电子设计自动化(EDA)的最新发展动态。SoC正在从单核向双核、四核和多核过渡。SoC设计必须采用DFM和EDA。采用DFM和EDA的优点:(1)提高芯片的生产效率和良率;(2)降低芯片生产成本;(3)缩短芯片生产周期,加速上市。 相似文献
48.
49.
Sébastien Aumaître Kirone Mallick François Pétrélis 《Journal of statistical physics》2006,123(4):909-927
A bifurcating system subject to multiplicative noise can exhibit on–off intermittency close to the instability threshold. For a canonical system, we discuss the dependence of this intermittency on the Power Spectrum Density (PSD) of the noise. Our study is based on the calculation of the Probability Density Function (PDF) of the unstable variable. We derive analytical results for some particular types of noises and interpret them in the framework of on-off intermittency. Besides, we perform a cumulant expansion (N. G. van Kampen, 24, 171 (1976).) for a random noise with arbitrary power spectrum density and we show that the intermittent regime is controlled by the ratio between the departure from the threshold and the value of the PSD of the noise at zero frequency. Our results are in agreement with numerical simulations performed with two types of random perturbations: colored Gaussian noise and deterministic fluctuations of a chaotic variable. Extensions of this study to another, more complex, system are presented and the underlying mechanisms are discussed.
PACS Number: 05.40.-a, 05.45.-a, 91.25.-r 相似文献
50.