全文获取类型
收费全文 | 55426篇 |
免费 | 262篇 |
国内免费 | 550篇 |
专业分类
系统科学 | 1229篇 |
丛书文集 | 243篇 |
教育与普及 | 298篇 |
理论与方法论 | 515篇 |
现状及发展 | 31963篇 |
研究方法 | 701篇 |
综合类 | 19098篇 |
自然研究 | 2191篇 |
出版年
2013年 | 812篇 |
2012年 | 574篇 |
2011年 | 2577篇 |
2009年 | 625篇 |
2008年 | 803篇 |
2007年 | 864篇 |
2006年 | 965篇 |
2005年 | 1131篇 |
2004年 | 2287篇 |
2003年 | 1889篇 |
2002年 | 1563篇 |
2001年 | 1323篇 |
2000年 | 882篇 |
1999年 | 954篇 |
1998年 | 648篇 |
1997年 | 771篇 |
1996年 | 534篇 |
1994年 | 683篇 |
1993年 | 690篇 |
1992年 | 855篇 |
1991年 | 748篇 |
1990年 | 850篇 |
1989年 | 657篇 |
1988年 | 637篇 |
1987年 | 657篇 |
1986年 | 742篇 |
1985年 | 855篇 |
1984年 | 750篇 |
1983年 | 690篇 |
1982年 | 791篇 |
1981年 | 832篇 |
1980年 | 913篇 |
1979年 | 1387篇 |
1978年 | 1269篇 |
1977年 | 1229篇 |
1976年 | 1088篇 |
1975年 | 1102篇 |
1974年 | 975篇 |
1973年 | 1192篇 |
1972年 | 1263篇 |
1971年 | 1323篇 |
1970年 | 1374篇 |
1969年 | 1257篇 |
1968年 | 1244篇 |
1967年 | 1073篇 |
1966年 | 906篇 |
1965年 | 725篇 |
1964年 | 503篇 |
1958年 | 593篇 |
1957年 | 508篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
411.
T. Ohhashi T. Miyazawa T. Azuma M. Sakaguchi 《Cellular and molecular life sciences : CMLS》1981,37(4):377-378
Summary The conduction velocity of peristaltic movements of the canine ureter was measured under anaesthesia with a new type of diameter gauge using an image sensor. The peristaltic velocity was 34.1±6.2 mm/sec in 10 experiments. Noradrenaline at a low dosage of 1 g/kg i.v. reduced the resting diameter, increased the conduction velocity to 47–56 mm/sec, and approximately doubled the frequency of contraction. The application of acetylcholine also caused an increase in both frequency and conduction velocity (42–46 mm/sec). A plot of the conduction velocity against the mean period of peristaltic contraction was hyperbolic in shape. 相似文献
412.
Summary Subdermal injections of PGE2 (5 g) in the rat foot lead to increases in the potentials evoked in sensory nerve branches by the mechanical stimulation of the skin. This sensitization of both A and C fibres complements the previously described hyperalgesic effects of prostaglandins of the E series. 相似文献
413.
Summary In reserpinized mice the occurrence of goldthioglucose hypothalamic lesions was significantly lower than in control mice. Some protection was also conferred by serotonin-receptor blockers and by treatment with nialamide+DL--methyldopa, but the protective effect of reserpine was not reversed by serotonergic and dopaminergic agonists, alone or in combination, nor by insulin. 相似文献
414.
Summary -Galactosidase activity in intact cells of 21 species ofStreptomyces was measured using ONPG hydrolysis, without addition of a permeabilizing agent. Differences in the induction efficiency of ONPG-hydrolytic activity by lactose or galactose, which could have taxonomic implications, were observed among the species. 相似文献
415.
F. Bonneaux P. Labrude E. Dellacherie 《Cellular and molecular life sciences : CMLS》1981,37(8):884-886
Summary Stroma-free hemoglobin solutions present some drawbacks when used as blood substitutes, essentially because the hemoprotein has a low vascular retention, due to its small hydrodynamic volume. Covalent coupling of the protein with dextran derivatives artificially increases its size and affords polymeric conjugates whose oxygen-binding properties (Barcroft's curve, Hill coefficient) depend on the molecular weight.The authors wish to thank Prof. J. Neel and Prof. C. Vigneron for useful discussions and criticism. 相似文献
416.
J. M. Saavedra 《Cellular and molecular life sciences : CMLS》1981,37(9):1002-1003
Summary Adult spontaneously hypertensive rats (SHR) are less sensitive to painful stimuli than their normotensive controls, Wistar-Kyoto (WKY) rats. This difference can be eliminated by the specific opiate antagonist, naloxone, and by the -adrenergic blocking agent, propranol.Acknowledgment. The author wishes to thank Miss R. L. Holcomb for her editorial assistance. 相似文献
417.
G. Cimino A. Crispino S. De Rosa S. De Stefano G. Sodano 《Cellular and molecular life sciences : CMLS》1981,37(9):924-926
Summary Several high molecular weight polyacetylenes have been isolated from the spongePetrosia ficiformis found in dark caves. These compounds are related to, but different from, the polyacetylenes isolated from the same sponge living in its usual habitat.This work is a part of the Progetto finalizzato per l'Oceanografia e i Fondi Marini, CNR, Roma.The authors thank Mr G. Scognamiglio for the HPLC work, Mr C. Di Pinto for the NMR spectra and Mr G. Villani for the collection of the sponge. 相似文献
418.
Nicoletta Crespi-Perellino A. Guicciardi A. Minghetti C. Spalla 《Cellular and molecular life sciences : CMLS》1981,37(3):217-218
Summary
Claviceps purpurea 275 F.I. fed with -aminobutyric acid produces ergostine with the corresponding -hydroxy--aminoacid undiluted by endogenous aminoacid. Almost all the -aminobutyric acid not incorporated into the ergostine remains unchanged in the medium. The significance of these results in the biosynthesis of ergot alkaloids is discussed. 相似文献
419.
Summary A simple device is described, which permits us to quantify several parameters of spontaneous behaviour of small animals. Using this device with mice we obtained statistically satisfactory results, showing a strong genetic influence on the behavioural characteristics tested.We wish to thank Mr R. Laplace for technical help, Mr J. P. Arnould for electronic work as well as I.N.S.E.R.M.-SCR 3. 相似文献
420.
H. Takeuchi T. Morimasa M. Matsumoto 《Cellular and molecular life sciences : CMLS》1977,33(7):938-939
Summary Several peptides were separated from-chymotrypsin-treated physalaemin by high voltage paper electrophoresis, and inhibition of the excitability of a molluscan giant neurone (tonically autoactive neurone) by the tripeptide, Lys-Phe-Tyr, was demonstrated.We thank Dr Sadaaki Iwanaga of Osaka University and Dr Atsuo Inoue of Daiichi Pharmaceutical CO for their helpful advice and the donation of the tripeptide (Lys-Phe-Tyr). 相似文献