全文获取类型
收费全文 | 30698篇 |
免费 | 84篇 |
国内免费 | 80篇 |
专业分类
系统科学 | 294篇 |
丛书文集 | 514篇 |
教育与普及 | 83篇 |
理论与方法论 | 125篇 |
现状及发展 | 12809篇 |
研究方法 | 1153篇 |
综合类 | 15286篇 |
自然研究 | 598篇 |
出版年
2013年 | 188篇 |
2012年 | 394篇 |
2011年 | 1031篇 |
2010年 | 159篇 |
2008年 | 469篇 |
2007年 | 523篇 |
2006年 | 556篇 |
2005年 | 547篇 |
2004年 | 587篇 |
2003年 | 550篇 |
2002年 | 479篇 |
2001年 | 892篇 |
2000年 | 899篇 |
1999年 | 534篇 |
1992年 | 546篇 |
1991年 | 469篇 |
1990年 | 497篇 |
1989年 | 453篇 |
1988年 | 480篇 |
1987年 | 487篇 |
1986年 | 454篇 |
1985年 | 650篇 |
1984年 | 488篇 |
1983年 | 398篇 |
1982年 | 320篇 |
1981年 | 346篇 |
1980年 | 434篇 |
1979年 | 928篇 |
1978年 | 762篇 |
1977年 | 732篇 |
1976年 | 628篇 |
1975年 | 695篇 |
1974年 | 880篇 |
1973年 | 791篇 |
1972年 | 769篇 |
1971年 | 946篇 |
1970年 | 1288篇 |
1969年 | 952篇 |
1968年 | 862篇 |
1967年 | 902篇 |
1966年 | 872篇 |
1965年 | 606篇 |
1964年 | 198篇 |
1959年 | 346篇 |
1958年 | 564篇 |
1957年 | 398篇 |
1956年 | 372篇 |
1955年 | 305篇 |
1954年 | 332篇 |
1948年 | 275篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
221.
222.
The spontaneous conversion of mammalian cyclic GMP-dependent protein kinase (G-PK) into modulator-dependent protein kinase (type II) (M-PKII) in the absence of cGMP or histone was observed in vitro. The findings, together with similarity in substrate protein specificity, suggest that M-PKII is the catalytic subunit of mammalian G-PK. 相似文献
223.
224.
R. Riehl 《Cellular and molecular life sciences : CMLS》1980,36(8):961-962
Summary The gonopodium of the mosquitofishHeteradria formosa was studied by transmission electron microscopy. In cross-section the gonopodium shows the following structure from the outside inwards: mutilayered epidermis, basal lamina and central supporting tissue, in which vessels and nerves are embedded. At the top of the gonopodium giant collagen fibres are found, which measure up to 150 m in length and 6 m in diameter. These fibres reinforce the gonopodium.This research was supported by the Deutsche Forschungsgemeinschaft. Address for reprints: Forschungsgruppe Dermatologie der Universität Heidelberg, Im Neuenheimer Feld 324, D-6900 Heidelberg. 相似文献
225.
Summary We analyzed inheritance of 5Es-1 alleles inP. leucopus and found them to be co-dominant and segregating from a single autosomal locus, thereby verifying assumptions of Mendelian inheritance imfield data. We also described an allele that is silent in hemolysate, but is active in liver extract.Acknowledgment. Laboratory analysis was partially supported by a grant-in-aid (No. 0171-02-240-76) to Kaufman from the Research Foundation of State University of New York. 相似文献
226.
J. Kędziora M. Soszyński G. Bartosz H. Witas W. Leyko 《Cellular and molecular life sciences : CMLS》1980,36(8):926-927
Summary A statistically significant decrease of prealbumin and statistically significant increases of alpha2-macroglobulin and IgA were found in blood plasma of patients with Down's syndrome using quantitative crossed immunoelectrophoresis.We are indebted to Prof. T.C. Bøg-Hansen, University of Copenhagen, for the helpful discussion of our results. 相似文献
227.
R. Dalwadi-Bhattacharya 《Cellular and molecular life sciences : CMLS》1980,36(1):74-75
Summary The circadian rhythm of rat liver-glucuronidase has been studied in animals kept under highly standardized laboratory condition. A clear 24 h rhythm has been observed for this enzyme with a peak activity at 01.00 h and a trough at 13.00 h.The work was carried out in Institut für Anatomie I, Medical School, Hannover (Federal Republic of Germany). Supported by grants from Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 146 and VW Stiftung, Hannover A2 11.2000. 相似文献
228.
W. D. MacRae G. F. Q. Chan Chi-Kit Wat G. H. N. Towers J. Lam 《Cellular and molecular life sciences : CMLS》1980,36(9):1096-1097
Summary -Terthienyl and 5 polyacetylenes were examined for chromosome damaging activity using Syrian hamster cells. None of these naturally occurring compounds induced sister chromatid exchanges and neither -terthienyl nor phenylheptatriyne induced chromosome aberrations.The authors wish to thank the National Science and Engineering Research Council for financial support of this research. 相似文献
229.
Summary
-adrenoceptor stimulation by isoprenaline increases the potassium efflux in beating guinea-pig atria. This effect is not mimicked by 8-bromo-cyclic AMP, a cyclic AMP analogue which exerts a positive inotropic effect in this preparation. 相似文献
230.
D. V. Amin R. B. Doctor A. O. Girdhar U. H. Shah 《Cellular and molecular life sciences : CMLS》1980,36(12):1410-1411
Summary Prostaglandin (PG) release was measured from the isolated perfused rabbit heart. The effects of -adrenergic stimulation and blockade suggest that PG synthesis is regulated in part by adrenergic mechanisms. 相似文献