全文获取类型
收费全文 | 26394篇 |
免费 | 73篇 |
国内免费 | 102篇 |
专业分类
系统科学 | 127篇 |
丛书文集 | 290篇 |
教育与普及 | 46篇 |
理论与方法论 | 100篇 |
现状及发展 | 12732篇 |
研究方法 | 1089篇 |
综合类 | 11899篇 |
自然研究 | 286篇 |
出版年
2012年 | 349篇 |
2011年 | 603篇 |
2010年 | 138篇 |
2009年 | 134篇 |
2008年 | 382篇 |
2007年 | 441篇 |
2006年 | 462篇 |
2005年 | 458篇 |
2004年 | 521篇 |
2003年 | 416篇 |
2002年 | 459篇 |
2001年 | 782篇 |
2000年 | 766篇 |
1999年 | 522篇 |
1992年 | 474篇 |
1991年 | 372篇 |
1990年 | 414篇 |
1989年 | 380篇 |
1988年 | 369篇 |
1987年 | 410篇 |
1986年 | 435篇 |
1985年 | 548篇 |
1984年 | 423篇 |
1983年 | 363篇 |
1982年 | 360篇 |
1981年 | 369篇 |
1980年 | 372篇 |
1979年 | 906篇 |
1978年 | 770篇 |
1977年 | 655篇 |
1976年 | 587篇 |
1975年 | 616篇 |
1974年 | 797篇 |
1973年 | 632篇 |
1972年 | 689篇 |
1971年 | 813篇 |
1970年 | 1023篇 |
1969年 | 761篇 |
1968年 | 797篇 |
1967年 | 788篇 |
1966年 | 636篇 |
1965年 | 524篇 |
1964年 | 208篇 |
1959年 | 269篇 |
1958年 | 477篇 |
1957年 | 333篇 |
1956年 | 270篇 |
1955年 | 264篇 |
1954年 | 258篇 |
1948年 | 182篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Summary Pronase and -chymotrypsin digested the major glycoprotein in the human and mouse red cell membranes and in SDS gel electrophoresis the glycoprotein disappeared accompanied by the appearance of a new band of lower mol.wt. However in the membranes of sheep, rat and rabbit, no digestion was demonstrated. The effects of pronase on anion permeability were almost identical for human and animal erythrocytes. 相似文献
192.
Summary A convenient one-step procedure, based upon the tyrosinase co-oxidation of dopa and cysteine, is reported for the synthesis of 5-S-cysteinyldopa (I) in 74% yield. Secondary products of the reaction turned out to be 2-S-cysteinyldopa (II, 14%), 2,5-S, S-dicysteinyldopa (IV, 5%), and the hitherto unknown 6-S-cysteinyldopa (III, 1%).The generic term cysteinyldopa is proposed to designate the various cotechol amino-acids arising from addition of cysteine to dopaquinone.This work was supported in part by a grant from Consiglio Nazionale delle Ricerche, Roma. 相似文献
193.
Summary N-(5-Phosphopyridoxyl)-4-aminobutyric acid, a stable adduct of pyridoxal phosphate and 4-aminobutyric acid, has been shown to be a potent inhibitor of rat brain 4-aminobutyric acid aminotransferase (GABA-T) with a Ki of 1.4 M.Acknowledgments. This work was supported in part by the United Parkinson Foundation, l'Association Canadienne l'Ataxie de Friedreich, and the Medical Research Council of Canada. 相似文献
194.
J. Kapitola H. Dlouhá Dr. J. Křeček J. Zicha 《Cellular and molecular life sciences : CMLS》1977,33(12):1615-1616
Summary Neurohypophyseal blood flow increases in water-deprived rats. This increase is independent of vasopressin release, since it occurs even in rats with hereditary defect of hypothalamic vasopressin synthesis.Acknowledgment. The technical assistance of D. Vilimovská is acknowledged. 相似文献
195.
M. D. Adams J. T. Earnhardt B. R. Martin L. S. Harris W. L. Dewey R. K. Razdan 《Cellular and molecular life sciences : CMLS》1977,33(9):1204-1205
Summary Abnormal-8-tetrahydrocannabidiol (ABN-8-THC) failed to elicit central nervous system and cardiovascular effects in laboratory animals. Abnormal-cannabidiol (ABN-CBD) was also devoid of overt behavioral effects but produced marked hypotension with only slight bradycardia in anesthesized dogs.Acknowledgment. This work was supported by NIDA (grant No. DA-00574-01 and DA-00490) and Virginia Heart Society (grant No. RR-05697) 相似文献
196.
R. K. Raina D. Njoroge J. N. Ng'ang'a B. V. Telang 《Cellular and molecular life sciences : CMLS》1977,33(11):1499-1500
Summary
Naja mossambica pallida venom administered i.v. (300 /kg) produces an initial brief fall in blood pressure, due to a direct myocardial depressant effect, and a sustained fall due to central depressant effect.This study was supported by University of Nairobi research grants (670–376). We also thank Mr E. Njogu for photographic assistance. 相似文献
197.
G. Apostol Constanţa Matei-Vladescu Valeria Popescu 《Cellular and molecular life sciences : CMLS》1977,33(3):345-347
Summary Contrary to earlier findings in rats, cerebral lateral ventricular infusions of 1×10–3 M or 2×10–3 M solutions of phloridzin at a rate of 2.5 l/min for 90 min had no significant stimulating effects on food intake and weight gain in hens and cocks. These different responses to intraventricular phloridzin might reflect a difference of sensitivity to the inhibitory action of phloridzin on glucose transport in cerebral cells or certain peculiarities of mechanisms controlling food intake in chickens. 相似文献
198.
Molecular analysis of spontaneous somatic mutants. 总被引:17,自引:0,他引:17
Eukaryotic structural gene mutations occurring spontaneously in a mouse myeloma cell line offer the opportunity to study somatic mutation in animal cells at the molecular level. Studies on the myeloma protein and on mRNA have enabled us to characterise four such mutants representing four different mutation mechanisms. The results may have some bearing on the origin of antibody diversity. 相似文献
199.