全文获取类型
收费全文 | 12368篇 |
免费 | 96篇 |
国内免费 | 83篇 |
专业分类
系统科学 | 69篇 |
丛书文集 | 145篇 |
教育与普及 | 16篇 |
理论与方法论 | 36篇 |
现状及发展 | 5717篇 |
研究方法 | 606篇 |
综合类 | 5809篇 |
自然研究 | 149篇 |
出版年
2012年 | 172篇 |
2011年 | 339篇 |
2010年 | 81篇 |
2009年 | 79篇 |
2008年 | 253篇 |
2007年 | 280篇 |
2006年 | 231篇 |
2005年 | 228篇 |
2004年 | 328篇 |
2003年 | 206篇 |
2002年 | 227篇 |
2001年 | 415篇 |
2000年 | 434篇 |
1999年 | 299篇 |
1992年 | 204篇 |
1991年 | 182篇 |
1990年 | 169篇 |
1989年 | 156篇 |
1988年 | 153篇 |
1987年 | 184篇 |
1986年 | 177篇 |
1985年 | 274篇 |
1984年 | 191篇 |
1983年 | 158篇 |
1982年 | 142篇 |
1981年 | 168篇 |
1980年 | 169篇 |
1979年 | 370篇 |
1978年 | 310篇 |
1977年 | 299篇 |
1976年 | 249篇 |
1975年 | 273篇 |
1974年 | 332篇 |
1973年 | 263篇 |
1972年 | 283篇 |
1971年 | 346篇 |
1970年 | 484篇 |
1969年 | 350篇 |
1968年 | 308篇 |
1967年 | 358篇 |
1966年 | 297篇 |
1965年 | 218篇 |
1964年 | 83篇 |
1959年 | 118篇 |
1958年 | 180篇 |
1957年 | 151篇 |
1956年 | 124篇 |
1955年 | 94篇 |
1954年 | 124篇 |
1948年 | 88篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
991.
Thymectomized, lethally irradiated rats reconstituted with syngeneic bone marrow were injected with rat brain in complete Freund adjuvant mixture. Both, they and sham-thymectomized, irradiated and bone marrow protected rats displayed a higher incidence of leg paralysis than normal non-irradiated animals. Thymectomy lowered the incidence of the disease. 相似文献
992.
993.
994.
Distribution of calcitonin cells in the thyroid glands of normal adult rhesus monkey Macaca mulatta.
The calcitonin cells of adult rhesus monkey Macaca mulatta are located in the central region of thyroid along the median axis. The anterior and posterior poles, the isthmus and peripheral regions of thyroid are completely devoid of C cells. The parathyroid also lacks C cells. 相似文献
995.
996.
本书论述细长桥梁或其他类似的土木工程结构在风力作用下的随机理论,为了预测这种结构在风力作用下的波动位移和截面力,需要建立计算理论,书中阐述发展这种理论所用的基本假设和方法,还给出了一些实际例子,以便读者更好地理解及应用所述的理论。 相似文献
997.
高度地概括了白俄罗斯泥炭沼泽研究进展和主要研究成果,探讨了人类活动对泥炭沼泽的影响,亦研究了白俄罗斯泥炭沼泽的开发利用,从沼泽学到沼泽业所走过的漫长而复杂的道路 相似文献
998.
N. Fraeyman G. De Bruecker A. De Schaepdryver 《Cellular and molecular life sciences : CMLS》1985,41(3):388-390
Summary Membrane resting potentials (MRP) were measured systematically in cultured mouse N2A neuroblastoma cells: 1) in the logarithmic growth phase; 2) in subconfluent cultures; 3) in confluent cultures; 4) after dBcAMP had induced morphological differentiation. Neurite extension was accompanied by a significant increase in MRP as compared to the appropriate controls. No significant differences in MRP were observed with regard to the different growth phases. 相似文献
999.
Dr. A. Shukla K. N. Agarwal G. S. Shukla 《Cellular and molecular life sciences : CMLS》1989,45(4):343-345
Summary A diet containing 18–20 mg iron/kg to young weaned rats for 8 weeks altered the metabolism of gamma-aminobutyric acid and glutamate in the central nervous system without affecting blood hemoglobin. Subsequent rehabilitation with 390 mg iron/kg diet for 2 weeks normalized these changes. 相似文献
1000.
Water molecules influence molecular interactions in all biological systems, yet it is extremely difficult to understand their effects in precise atomic detail. Here we present evidence, based on highly refined atomic structures of the complexes of the L-arabinose-binding protein with L-arabinose, D-fucose and D-galactose, that bound water molecules, coupled with localized conformational changes, can govern substrate specificity and affinity. The atoms common to the three sugars are identically positioned in the binding site and the same nine strong hydrogen bonds are formed in all three complexes. Two hydrogen-bonded water molecules in the site contribute further to tight binding of L-arabinose but create an unfavourable interaction with the methyl group of D-fucose. Equally tight binding of D-galactose is attained by the replacement of one of the hydrogen-bonded water molecules by its--CH2OH group, coordinated with localized structural changes which include a shift and redirection of the hydrogen-bonding interactions of the other water molecule. These observations illustrate how ordered water molecules can contribute directly to the properties of proteins by influencing their interaction with ligands. 相似文献