全文获取类型
收费全文 | 2572篇 |
免费 | 55篇 |
国内免费 | 15篇 |
专业分类
化学 | 1846篇 |
晶体学 | 11篇 |
力学 | 46篇 |
数学 | 379篇 |
物理学 | 360篇 |
出版年
2020年 | 25篇 |
2019年 | 29篇 |
2016年 | 48篇 |
2015年 | 46篇 |
2014年 | 43篇 |
2013年 | 96篇 |
2012年 | 128篇 |
2011年 | 152篇 |
2010年 | 76篇 |
2009年 | 70篇 |
2008年 | 152篇 |
2007年 | 121篇 |
2006年 | 127篇 |
2005年 | 109篇 |
2004年 | 93篇 |
2003年 | 79篇 |
2002年 | 94篇 |
2001年 | 39篇 |
2000年 | 36篇 |
1999年 | 41篇 |
1998年 | 33篇 |
1997年 | 42篇 |
1996年 | 41篇 |
1995年 | 32篇 |
1994年 | 28篇 |
1993年 | 38篇 |
1992年 | 30篇 |
1991年 | 26篇 |
1990年 | 22篇 |
1989年 | 32篇 |
1988年 | 30篇 |
1987年 | 20篇 |
1985年 | 40篇 |
1984年 | 43篇 |
1983年 | 28篇 |
1982年 | 38篇 |
1981年 | 32篇 |
1980年 | 49篇 |
1979年 | 41篇 |
1978年 | 44篇 |
1977年 | 23篇 |
1976年 | 26篇 |
1975年 | 31篇 |
1974年 | 19篇 |
1973年 | 27篇 |
1971年 | 19篇 |
1968年 | 14篇 |
1966年 | 16篇 |
1960年 | 14篇 |
1959年 | 15篇 |
排序方式: 共有2642条查询结果,搜索用时 0 毫秒
1.
Feel like writing a review for The Mathematical Intelligencer? You are welcome to submit an unsolicited review of a book of your choice; or, if you would welcome being assigned a book to review, please write us, telling us your expertise and your predilections. 相似文献
2.
Mark Doyle Susan A. Mulligan Tetsuya Matsuda Gerald M. Pohost 《Magnetic resonance imaging》1992,10(6):887-892
A new “bright blood” strategy, outflow refreshment imaging, is introduced in which a number of overlapping slices are excited in rapid succession. Flowing spins that refresh each overlapped slice portion contribute a bright signal. Additionally, static tissue in each non-overlapped slice portion also yields a bright signal. However, the flow/static contrast is comparable to that produced in inflow refreshment images, and angiograms can be generated by conventional maximum intensity projection processing. The dual ability to visualize angiograms and static tissue images is a major benefit of the strategy. Computer simulations of flow sensitivities and in vivo results are presented which compare the outflow and inflow refreshment imaging strategies. 相似文献
3.
4.
5.
Vladimir B. Arion Alexey A. Nazarov Christian G. Hartinger Gerald Giester Bernhard K. Keppler 《应用有机金属化学》2003,17(9):723-724
For the unsymmetrical title compound, 1‐bromo‐1′‐[(2S)‐N‐(1‐hydroxy‐3‐methylbutane‐2‐yl)]‐ferroceneamide, two independent molecules were found in the asymmetric unit. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
6.
Gerald W. Evans Robert Fairbairn 《The Journal of the Operational Research Society》1989,40(11):971-981
A 0-1 integer linear programme for the selection and scheduling of US National Aeronautics and Space Administration (NASA) missions over a long planning horizon is presented. This model was formulated to allow a higher-level user-interaction with an advanced missions database currently being developed. The model implicitly considers the multi-objective nature of the problem, which results from the desire to maximize benefits in several categories as well as from the desire to minimize cost. In addition, the model allows the planner much flexibility in the selection process. This is accomplished by allowing the planner the ability to specify long- or short-term budget constraints, precursor/follow-on mission requirements, or any number of other idiosyncratic constraints which might be of importance in the decision process. Small example problems are solved in order to illustrate the approach, and areas for further research are discussed. 相似文献
7.
Gerald Koitz Walter Fabian Hans-Werner Schmidt Hans Junek 《Monatshefte für Chemie / Chemical Monthly》1981,112(8-9):973-985
The synthesis of several 2-aminopyridines is described. The reaction of tetracyanoethylene with 3-imino-propane-carbonitrile gives 2-amino-3,4,5-tricyano-pyridines with alkyl and aryl-substituents, resp., in position 6. Nucleophilic substitution of 2-amino-6-chloro-3,5-dicyanopyridines and 2-amino-6-chloro-3,4,5-tricyano-pyridines with phenolates leads to a variety of pyridines. Spectroscopical data of absorption and fluorescence are presented and the influence of the cyano groups is discussed. The results are in good agreement with quantum chemical calculations (PPP).
Herrn Univ-Prof. Dr.A. Holasek zum 60. Geburtstag gewidmet. 相似文献
8.
Generalizing the work of Einstein and Mayer, it is assumed that at each point of space-time there exists a vector-spinor space with Nv vector dimensions and Ns spinor dimensions, where Nv=2k and Ns=2
k, k3. This space is decomposed into a tangent space with4 vector and4 spinor dimensions and an internal space with Nv–4 vector and Ns–4 spinor dimension. A variational principle leads to field equations for geometric quantities which can be identified with physical fields such as the electromagnetic field, Yang-Mills gauge fields, and wave functions of bosons and fermions. 相似文献
9.
As part of a fundamental study of the behaviour of mixed plastics during reprocessing and in service, blends of low density polyethylene (LDPE) and polyvinyl chloride (PVC) have been investigated. It was found that Young's modulus increased steadily from pure LDPE to pure PVC whereas both tensile strength at break and elongation at break passed through a minimum at about 5% PVC. Optical and scanning electron microscope studies have related this mechanical behaviour to morphological changes in the two phase system under stress. 相似文献
10.
Gerald Kainz und Eugen Wachberger 《Fresenius' Journal of Analytical Chemistry》1966,222(2):278-282
Zusammenfassung Zur Bestimmung des Sauerstoffs wird die organische Probe in Helium-Atmosphäre gecrackt; die sauerstoffhaltigen Crackprodukte werden über Kohle zu Kohlenmonoxid konvertiert. Um das Kohlenmonoxid von den übrigen Crackprodukten, wie H2, N2 und CH4 abzutrennen, wird es zu Kohlendioxid oxydiert und danach an einem Molekularsieb bei 20° C durch Adsorption zurückgehalten; H2, N2 und CH4 werden aus der Apparatur gespült. Sobald in der Probeleitung reines Spülgas auftritt, wird das adsorbierte Kohlendioxid durch Erhitzen desorbiert und im Detektor gemessen.
Es ist uns eine angenehme Pflicht, der Shell Austria AG., Wien, insbesondere Herrn Direktor Dipl.-Ing. R. Wallner, für die Gewährung eines Forschungsstipendiums an den einen von uns (E. W.) ergebenst zu danken. 相似文献
Summary For the determination of oxygen the organic sample is cracked in helium atmosphere. Cracking products, containing oxygen, are converted to carbon monoxide by coal. For separation from the remaining cracking products (H2, N2, CH4) carbon monoxide is oxidized and then adsorbed on molecular sieve 5A at 20°C; H2, N2 and CH4 are flushed out. As soon as pure carrier gas flows through the sample pipe, carbon dioxide is desorbed by heating the molecular sieve and flushed to the detector.
Es ist uns eine angenehme Pflicht, der Shell Austria AG., Wien, insbesondere Herrn Direktor Dipl.-Ing. R. Wallner, für die Gewährung eines Forschungsstipendiums an den einen von uns (E. W.) ergebenst zu danken. 相似文献