全文获取类型
收费全文 | 1358篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
化学 | 937篇 |
晶体学 | 8篇 |
力学 | 33篇 |
数学 | 237篇 |
物理学 | 173篇 |
出版年
2022年 | 12篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 17篇 |
2016年 | 26篇 |
2015年 | 23篇 |
2014年 | 31篇 |
2013年 | 56篇 |
2012年 | 65篇 |
2011年 | 59篇 |
2010年 | 43篇 |
2009年 | 38篇 |
2008年 | 64篇 |
2007年 | 56篇 |
2006年 | 50篇 |
2005年 | 59篇 |
2004年 | 68篇 |
2003年 | 50篇 |
2002年 | 39篇 |
2001年 | 20篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 18篇 |
1997年 | 20篇 |
1996年 | 24篇 |
1995年 | 26篇 |
1994年 | 15篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 19篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 16篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1973年 | 18篇 |
1972年 | 8篇 |
1943年 | 10篇 |
1929年 | 7篇 |
1928年 | 10篇 |
1920年 | 7篇 |
排序方式: 共有1388条查询结果,搜索用时 31 毫秒
161.
162.
The microwave part of the dielectric spectrum (ν ? 1 GHz) is considered of aqueous phospholipid solutions in the limit of high water content. A continuum model is presented which allows to calculate in the water relaxation region the frequency-dependent complex permittivity of solutions in which the bilayers form globular single-walled vesicles as well as multilamellar liposomes. The model is not only capable of explaining the strikingly small values of the extrapolated static permittivity and of the main dielectric relaxation time which became evident in many measurements on colloidal aqueous solutions of phospholipids. It also allows the positive and negative step-like changes in the dielectric properties of solutions, which have been found at the main (order-disorder) phase transition temperature of the bilayers, to be explained by dimensional changes as resulting from vesicle growth and fusion. 相似文献
163.
Soils developed from recent basalts of Marion Island in the Sub-Antarctic contain about 20% of a poorly crystalline iron oxide. The association of this phase with Al and Si appears to have a major influence on its Mössbauer spectra: whereas room-temperature spectra indicate a relatively regular structure, the magnetic hyperfine fields at 4.2K are lower than those of even the most poorly crystalline pure ferrihydrites. 相似文献
164.
165.
166.
J. Gwinner H. Läpple Ch. Schneeweiß H. G. Bartels E. Kaspar K. -H. Waldmann R. Horst R. Hebel H. Späth 《Mathematical Methods of Operations Research》1977,21(4):B159-B164
Ohne Zusammenfassung 相似文献
167.
168.
169.
Karl Cammann Udo Lemke Anja Rohen Jürgen Sander Hildegard Wilken Babette Winter 《Angewandte Chemie (International ed. in English)》1991,30(5):516-539
Chemical and environmental engineering and biotechnology are among the fields now being transformed by continually increasing levels of automation. Whereas the objective in other sectors of industry is simply to increase efficiency, here considerations of system theory or safety demand a high level of automation. Either the processes are too complex and require multifunctional control with feedback, or an analysis of the safety requirements shows the necessity for a certain degree of redundancy in the safety measures, and for elimination of human error as a risk factor. With regard to quality control, cost-benefit analyses lead to striking conclusions which again indicate the need for highly automated, and above all reliable, systems to eliminate rejects. The crux of any automated system is the measurement and control technology; of central importance is the rapid, reliable, and in some cases continuous, measurement and interpretation of key processes or control variables. For this purpose a wide variety of recording instruments and sensors are used to give as accurate a picture as possible of the state of the system. It is obvious from this that the performance of the control system is critically dependent on the sensors. Errors in the measured quantities can become amplified in the control variables or, in dynamic systems, can lead to undesirable operating conditions. Moreover, as a consequence of great advances in microelectronics, “intelligent sensors” which can calibrate and control themselves will be one of the key technologies of the nineties. Unless fast and immediate information on the true current status of a system is available, microprocessors as control devices react blindly and unpredictably to errors in input information. New discoveries in the fields of electronic, electrochemical, and optical transducers are now being applied in heterogeneous catalysis and surface physics, and in biochemistry (enzymology and immunology); in these fields new chemical sensor principles are being tested, which could revolutionize instrumental methods of molecular analysis in particular, owing to their very favorable cost-performance relationship. This article aims to give an up-to-date overview of the current state of the art in these developments, with emphasis on their importance for analysis and their significance in relation to the chemist's interest in mechanisms for identifying substances. 相似文献
170.