全文获取类型
收费全文 | 17235篇 |
免费 | 42篇 |
国内免费 | 53篇 |
专业分类
系统科学 | 253篇 |
丛书文集 | 444篇 |
教育与普及 | 36篇 |
理论与方法论 | 50篇 |
现状及发展 | 7948篇 |
研究方法 | 724篇 |
综合类 | 7727篇 |
自然研究 | 148篇 |
出版年
2012年 | 203篇 |
2011年 | 409篇 |
2010年 | 97篇 |
2009年 | 94篇 |
2008年 | 272篇 |
2007年 | 346篇 |
2006年 | 291篇 |
2005年 | 298篇 |
2004年 | 273篇 |
2003年 | 325篇 |
2002年 | 261篇 |
2001年 | 609篇 |
2000年 | 609篇 |
1999年 | 344篇 |
1992年 | 328篇 |
1991年 | 253篇 |
1990年 | 298篇 |
1989年 | 271篇 |
1988年 | 262篇 |
1987年 | 276篇 |
1986年 | 284篇 |
1985年 | 338篇 |
1984年 | 242篇 |
1983年 | 219篇 |
1982年 | 200篇 |
1981年 | 238篇 |
1980年 | 261篇 |
1979年 | 568篇 |
1978年 | 463篇 |
1977年 | 469篇 |
1976年 | 351篇 |
1975年 | 374篇 |
1974年 | 583篇 |
1973年 | 455篇 |
1972年 | 413篇 |
1971年 | 510篇 |
1970年 | 656篇 |
1969年 | 573篇 |
1968年 | 492篇 |
1967年 | 528篇 |
1966年 | 439篇 |
1965年 | 330篇 |
1964年 | 86篇 |
1959年 | 198篇 |
1958年 | 293篇 |
1957年 | 192篇 |
1956年 | 172篇 |
1955年 | 167篇 |
1954年 | 159篇 |
1948年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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
102.
Summary The female: male sex ratio in litters born to C57 black mice immunized with male spleen preparations is 21 and males were stillborn. In additionDrosophila busckii males are H-Y antigen positive. It is argued that H-Y is the primary testicular determinant and that this role is evolutionarily ancient. 相似文献
103.
B. Lejczak H. Starzemska P. Mastalerz 《Cellular and molecular life sciences : CMLS》1981,37(5):461-462
Summary Analogues of glutamic acid, -methylglutamic acid and glutamine in which the -or -COOH groups are replaced by PO3H2 or P(O)(OH3)OH functions competitively inhibit rat liver glutamine synthetase. The K1 values are comparable to or lower than KM for L-glutamate.This study was supported by grant R.1.9. 相似文献
104.
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
105.
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
106.
M. Larpent-Gourgaud M. P. Aumaître 《Cellular and molecular life sciences : CMLS》1977,33(12):1601-1602
Summary The radiations coming from Blanc Brillant de Luxe' fluorescent stimulate the growth and ramification of protonema ofCeratodon purpureus (Hedw.) Brid. This stimulation is caused by red light (660 nm). Multidirectional lightening is more favorable than unidirectional exposition. 相似文献
107.
Non-mendelial female sterility in Drosophila melanogaster: demonstration of an inducer chromosome 4]
A Pélisson 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,284(23):2399-2402
Crosses between two classes of Drosophila melanogaster strains (reactive and inducer) may lead to partially sterile F1 females. This sterility, called S.F. sterility, can be characterized by its physiological features. It appears to be the result of an interaction between two factors: "R" brought into the initial croos by the reactive mother and "I" by chromosomes of the inducer father. Except for chromosome 4, each chromosome of the well known inducer strains may carry the I factor (inducer chromosomes). The present results provide evidence for the presence of an inducer fourth chromosome in the inducer strain Nagasaki. 相似文献
108.
J P Garrec J Jourdan B Blanchard A Hartmann J P Lassalles M Thellier 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,285(5):579-582
The use of the stable isotopes 6 and 7 of lithium, and detection with the ionic analyser, allow the measurement of unidirectional transepithelial Li-fluxes, between "external" and "internal" solutions which both contain 80% Na and 20% Li. Efflux was found to be bigger than influx. An important lag-phase on the curve, reveals the interference of a Li-compartment, with a high capacity, in the epithelium itself. 相似文献
109.
110.
Transposable genetic elements as agents of gene instability and chromosomal rearrangements. 总被引:31,自引:0,他引:31
Transposable genetic elements in prokaryotes and eukaryotes, when inserted at a given locus, can control expression of the locus and cause large scale rearrangements of adjacent DNA sequences. Striking similarities in genetic behaviour between the two groups of elements have led to the proposal of a molecular model of eukaryotic controlling elements, and to suggestions about the part such elements may play in evolution and differentiation. 相似文献