全文获取类型
收费全文 | 43396篇 |
免费 | 94篇 |
国内免费 | 146篇 |
专业分类
系统科学 | 212篇 |
丛书文集 | 826篇 |
教育与普及 | 115篇 |
理论与方法论 | 231篇 |
现状及发展 | 19298篇 |
研究方法 | 1681篇 |
综合类 | 20746篇 |
自然研究 | 527篇 |
出版年
2013年 | 301篇 |
2012年 | 576篇 |
2011年 | 1117篇 |
2010年 | 258篇 |
2008年 | 754篇 |
2007年 | 782篇 |
2006年 | 821篇 |
2005年 | 830篇 |
2004年 | 734篇 |
2003年 | 792篇 |
2002年 | 768篇 |
2001年 | 1334篇 |
2000年 | 1217篇 |
1999年 | 805篇 |
1994年 | 373篇 |
1992年 | 786篇 |
1991年 | 619篇 |
1990年 | 681篇 |
1989年 | 673篇 |
1988年 | 642篇 |
1987年 | 685篇 |
1986年 | 682篇 |
1985年 | 857篇 |
1984年 | 670篇 |
1983年 | 570篇 |
1982年 | 523篇 |
1981年 | 499篇 |
1980年 | 603篇 |
1979年 | 1398篇 |
1978年 | 1180篇 |
1977年 | 1114篇 |
1976年 | 835篇 |
1975年 | 909篇 |
1974年 | 1245篇 |
1973年 | 1074篇 |
1972年 | 1072篇 |
1971年 | 1332篇 |
1970年 | 1754篇 |
1969年 | 1330篇 |
1968年 | 1284篇 |
1967年 | 1276篇 |
1966年 | 1126篇 |
1965年 | 820篇 |
1959年 | 483篇 |
1958年 | 729篇 |
1957年 | 565篇 |
1956年 | 496篇 |
1955年 | 433篇 |
1954年 | 470篇 |
1948年 | 298篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Bacillus thuringiensis delta-endotoxin: evidence that toxin acts at the surface of susceptible cells 总被引:4,自引:0,他引:4
Enzymically activated delta-endotoxin of Bacillus thuringiensis covalently bound to Sephadex beads, has the same effect on insect cells in tissue culture as free toxin. The effect is prevented by antitoxin antibody and heat denaturation and is not due to a nonspecific protein effect, the beads, or toxin released from the beads. The toxin, therefore, probably acts at the cell surface. 相似文献
962.
D Gerlier F Sakai J F Doré 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(5):439-442
The Gross virus associated cell surface antigen GCSAa was extracted from (C58NT)D cells by solubilization of membranes with detergent and partially purified. This antigen was entraped in liposomes. Absorption experiments of the cytotoxic activity towards EmaleG2 cells of a W/Fu anti (C58NT)D serum showed the presence of the antigen at the surface of sensibilized liposomes. 相似文献
963.
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
964.
D. Kritchevsky J. A. Story D. M. Klurfeld 《Cellular and molecular life sciences : CMLS》1978,34(10):1328-1328
Summary Addition of 0.05–0.20% of 3-hydroxy-3-methylglutaric acid to a lithogenic hamster diet resulted in a marked reduction in the incidence of gallstones in hamsters.Supported, in part, by grants HL-03299, AG-00076 and T32 CA-09171 and a Research Career Award, HL-0734 from the National Institutes of Health. 相似文献
965.
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
966.
S. Barrigón J. Tamargo P. D. Garcia de Jalón 《Cellular and molecular life sciences : CMLS》1978,34(6):770-770
Summary Bunaphtide induces a blockade in the3H-norepinephrine uptake and retention in the isolated guinea-pig left atrium. However, this blockade does not seems to be related with the cardiodepressant effect of the drug. 相似文献
967.
Summary A glucose concentration of 3.5 mg/ml is optimal for in vitro embryo attachment and trophoblastic cell outgrowth. Raising the concentration above 3.5 mg/ml does not improve embryo culture and can at certain concentrations be detrimental to embryo development. 相似文献
968.
Summary In the normal and hypothyroid 6-day-old rat, the specific radioactivity (RSA) and the relative RSA (ratio of the RSA to the [3H] leucine concentration of the acido soluble phase) of the cerebral and cerebellar proteins, change during the day synchronally. They show a maximum at 15.00 h and a minimum at 03.00 h. At all stages studied, these values are significantly lower in the hypothyroid animals than in normal ones. 相似文献
969.
A Jouve J P Truchot 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(4):331-334
At 15 degrees C, the oxygen uptake rate of Carcinus maenas was practically independent of the ambient oxygen pressure betueen 50 and 500 Torr. Within this range, hyperventilatory and hypoventilatory responses were observed in hypoxic and hyperoxic conditions respectively whereas the oxygen extraction coefficient remained more or less constant. 相似文献
970.
M J Alluchon-Gérard J Mellinger 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1978,286(21):1511-1514
In the adenohypophysis of very young spotted dogfish, only one kind of granulated cells show strcutural changes following thyroidectomy: the small granule cells of the ventral lobe (granule diameter about 110 nm). These cells are similar to the thyrotrophs of other Vertebrates, and well distinct from the supposed gonadotrophs found in the same lobe. 相似文献