全文获取类型
收费全文 | 28514篇 |
免费 | 86篇 |
国内免费 | 75篇 |
专业分类
系统科学 | 280篇 |
丛书文集 | 507篇 |
教育与普及 | 49篇 |
理论与方法论 | 113篇 |
现状及发展 | 12645篇 |
研究方法 | 1148篇 |
综合类 | 13484篇 |
自然研究 | 449篇 |
出版年
2013年 | 195篇 |
2012年 | 428篇 |
2011年 | 876篇 |
2010年 | 170篇 |
2008年 | 463篇 |
2007年 | 514篇 |
2006年 | 548篇 |
2005年 | 533篇 |
2004年 | 542篇 |
2003年 | 504篇 |
2002年 | 438篇 |
2001年 | 858篇 |
2000年 | 813篇 |
1999年 | 501篇 |
1992年 | 499篇 |
1991年 | 431篇 |
1990年 | 469篇 |
1989年 | 383篇 |
1988年 | 426篇 |
1987年 | 447篇 |
1986年 | 394篇 |
1985年 | 567篇 |
1984年 | 437篇 |
1983年 | 369篇 |
1982年 | 300篇 |
1981年 | 310篇 |
1980年 | 406篇 |
1979年 | 880篇 |
1978年 | 747篇 |
1977年 | 708篇 |
1976年 | 571篇 |
1975年 | 653篇 |
1974年 | 853篇 |
1973年 | 727篇 |
1972年 | 771篇 |
1971年 | 875篇 |
1970年 | 1162篇 |
1969年 | 916篇 |
1968年 | 795篇 |
1967年 | 836篇 |
1966年 | 770篇 |
1965年 | 573篇 |
1964年 | 163篇 |
1959年 | 304篇 |
1958年 | 468篇 |
1957年 | 349篇 |
1956年 | 302篇 |
1955年 | 272篇 |
1954年 | 305篇 |
1948年 | 207篇 |
排序方式: 共有10000条查询结果,搜索用时 320 毫秒
61.
T lymphocytes recognize antigen in the form of peptides that associate with specific alleles of class I or class II major histocompatibility (MHC) molecules. By contrast with the clear MHC allele-specific binding of peptides to purified class II molecules purified solubilized class I molecules either bind relatively poorly or show degenerate specificity. Using photo-affinity labelling, we demonstrate here the specific interaction of peptides with cell-associated MHC class I molecules and show that this involves metabolically active processes. 相似文献
62.
Ramsés Fuenmayor 《Systemic Practice and Action Research》1991,4(5):473-490
Both an ontoepistemology for reductionist modern science (counter-ontoepistemology) and an ontology for interpretive Systemology have been outlined in the two preceding papers in this special issue ofSystems Practice. In the present article, the notion of “truth” is interpreted in terms of both the ontoepistemology of “reductionism” and the ontology of interpretive systemology. Both interpretations are discussed. Such a discussion represents the objective of this paper, that is, to outline the epistemological “face” of the ontoepistemology of interpretive systemology. In order to design that “epistemological face,” the relation between ontology and epistemology must be clarified. Such a relation is seen from the standpoint already provided by the ontology. After the discussion on the notion of truth, the general shape of a systemic-interpretive inquiring process is outlined. 相似文献
63.
R. Cavelti 《Cellular and molecular life sciences : CMLS》1948,4(12):487-489
Summary (1) Doubly refracting lipoid droplets can be demonstrated in normal and pathological sera by means of alcohol ether extraction. This is not possible with ether extraction alone.(2) These lipoid droplets can be demonstrated only, or almost only, when they are precipitated out of alcohol or ether alcohol 相似文献
64.
LANE RE 《Advancement of science》1948,5(18):96-118
65.
66.
67.
68.
R. Auerbach 《Cellular and molecular life sciences : CMLS》1948,4(12):473-474
Summary The preceding empirical relation was found between the surface tension of liquids, the specific weight of liquids, and the velocity of sound:=6.3 · 10–4
3/2. In place of the vèocity of sound can be used, with suitable changes in the equation, the compressibility or, in the case of solid substances, the elasticity of the material in question. The range of validity of this relation is so large that it is possible by means of it to calculate the surface tension of solid substances and of gases. 相似文献
69.
Summary An alcaloid C16H19NO3 has been isolated fromErythrina tholloniana; the iodohydrate of this erythroidine has a melting point of 225°C and 239°C for its chlorhydrate. It has a powerful curare-like action on the frog or on its isolated sciatic-sartorius preparation; at a concentration of less than 1/1,000,000, a complete neuromuscular block is produced: the electrical stimulation of the motor nerve does not produce any contraction, but the muscle reacts by an end-plate potential having the same characteristics (shape, duration, possibility of summation) as the electrical waves produced in the same preparation curarized by ordinary curare or by quaternary ammonium derivatives. Decurarization by veratrine 1/200,000 is accompanied by the same electrical reactions as those which have been described in preparations treated by curare.On mammals, the alcaloid has little curariform activity; on the isolated phrenic-diaphragm preparation of the rat, incomplete block was produced at a concentration of 1/5000. 相似文献
70.
R. Cavelti 《Cellular and molecular life sciences : CMLS》1948,4(12):489-490
Summary (1) No double refractile Iipoid droplets can be obtained by alcohol ether extraction from urine or from urinary protein as it is possible from blood serum.(2) The conclusion is drawn that the double refractile lipoids droplets in urinary sediment do not pass through the glomeruli and therefore are not reabsorbed by the tubuli, but that they come from the own lipoproteins of the epithelial cells of renal tubuli and pass into urine by dissolution and desquamation of these cells. 相似文献