全文获取类型
收费全文 | 20692篇 |
免费 | 176篇 |
国内免费 | 255篇 |
专业分类
系统科学 | 188篇 |
丛书文集 | 261篇 |
教育与普及 | 133篇 |
理论与方法论 | 60篇 |
现状及发展 | 7654篇 |
研究方法 | 673篇 |
综合类 | 11996篇 |
自然研究 | 158篇 |
出版年
2012年 | 311篇 |
2011年 | 472篇 |
2010年 | 206篇 |
2009年 | 255篇 |
2008年 | 417篇 |
2007年 | 421篇 |
2006年 | 408篇 |
2005年 | 412篇 |
2004年 | 443篇 |
2003年 | 429篇 |
2002年 | 451篇 |
2001年 | 640篇 |
2000年 | 603篇 |
1999年 | 583篇 |
1998年 | 250篇 |
1996年 | 220篇 |
1995年 | 209篇 |
1994年 | 436篇 |
1992年 | 389篇 |
1991年 | 332篇 |
1990年 | 389篇 |
1989年 | 356篇 |
1988年 | 341篇 |
1987年 | 346篇 |
1986年 | 317篇 |
1985年 | 352篇 |
1984年 | 234篇 |
1983年 | 257篇 |
1982年 | 212篇 |
1981年 | 204篇 |
1980年 | 245篇 |
1979年 | 508篇 |
1978年 | 434篇 |
1977年 | 390篇 |
1976年 | 314篇 |
1975年 | 386篇 |
1974年 | 474篇 |
1973年 | 422篇 |
1972年 | 431篇 |
1971年 | 562篇 |
1970年 | 608篇 |
1969年 | 531篇 |
1968年 | 532篇 |
1967年 | 459篇 |
1966年 | 408篇 |
1965年 | 294篇 |
1958年 | 322篇 |
1957年 | 253篇 |
1956年 | 202篇 |
1955年 | 200篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
Urease inhibition by hydroxamic acids 总被引:1,自引:0,他引:1
H. A. Akers 《Cellular and molecular life sciences : CMLS》1981,37(3):229-230
Summary Ureases from jack beans andRhodototorula pilimanae were observed to be inhibited by primary hydroxamic acids but were not inhibited by acyclic-secondary (N-alkyl) hydroxamic acids.This project was supported by a Lamar University organized research grant. 相似文献
992.
Single units in the cat lateral geniculate nucleus and primary visual cortex show changes in both spontaneous and visually evoked firing as a function of the state of wakefulness. On arousal spontaneous firing is smoother and often reduced, whereas evoked responses are usually enhanced; the result is an increase in the signal-to-noise ratio. Single- and double-label 2-deoxyglucose autoradiographs show further that slow-wave sleep differentially depresses visually evoked activity in the deeper layers of the visual cortex. 相似文献
993.
H. Magloire J. Dumont J. A. Grimaud A. Joffre G. Benay D. Herbage 《Cellular and molecular life sciences : CMLS》1981,37(10):1103-1105
Summary
Actinomyces viscosus Be 66, added to pulpal cells in culture, does not cause apparent cellular damage. The extracellular matrix consists of altered collagen fibrils and thin filaments, immunochemically identified as type I collagen. They probably represent the first steps of collagen degradation.This work was supported by INSERM (ATP: 77-85) and CNRS (RCP: 533). 相似文献
994.
Summary The formation of the myotomes to chick embryos was studied by using experimental and scanning electron microscope techniques. With the aid of the quail-chick marker system, it was demonstrated that the dermatome gives rise to the myotome plate. SEM studies support the conclusion that the myotome cells originate only from the edges of the dermatome.Supported by the Deutsche Forschungsgemeinschaft (Ch 44/2). 相似文献
995.
Summary Studies which indicate the fusion of rat liver microsomal vesicles show that the rate of fusion of microsomal vesicles, as revealed by electron microscopic examinations, is dependent on the fusion temperature and the amount of detergent present in the microsomal suspension.Acknowledgments. We thank Miss R. Kannler for excellent technical assistance. The electron microscopy was performed in Anatomisches Institut and the Strahlenzentrum of the University of Giessen. This investigation was supported by the Deutsche Forschungsgemeinschaft (Schu 54/5) and by the Stiftung Volkswagenwerk (AZ 11 2454). 相似文献
996.
997.
H Bartels R Bartels R Baumann R Fons K D Jürgens P Wright 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(16):1195-1198
A high oxygen capacity combined with a low oxygen affinity and a large Bohr effect achieve a high oxygen transport capacity in small shrews. The high metabolic rate (Suncus estruscus: 100 to 350 ml O2/kg. min) can be explained by the combination of the favorable blood parameters with a high relative heart weight (1,2% of body weight) and heart frequencies of 1,000 to 1,350 per minute. 相似文献
998.
K. Silberbauer H. Sinzinger Maya Winter W. Feigl F. Ring 《Cellular and molecular life sciences : CMLS》1978,34(11):1471-1472
Summary Morphological control of Moncada's bioassay for prostacyclin (PG I2) activity measurement shows that the activity depends not only on endothelium, but in important amounts on subendothelial tissue too. Therefore, it can be concluded that platelet thrombus formation after endothelial cell injury does not depend only on the PG I2-producing ability of the tissue. 相似文献
999.
1000.
Neurophysiological basis of directional hearing in amphibia 总被引:2,自引:0,他引:2
Discrete regions of neural tissue along the anterior-posterior axis of the torus semicircularis act as resonators, each one broadly tuned to a different range of frequencies, and each one responding optimally to the incident sound from a different direction. In this way, a map of auditory space is represented in the midbrain. 相似文献