全文获取类型
收费全文 | 39447篇 |
免费 | 129篇 |
国内免费 | 155篇 |
专业分类
系统科学 | 370篇 |
丛书文集 | 830篇 |
教育与普及 | 68篇 |
理论与方法论 | 125篇 |
现状及发展 | 18001篇 |
研究方法 | 1564篇 |
综合类 | 18184篇 |
自然研究 | 589篇 |
出版年
2013年 | 247篇 |
2012年 | 531篇 |
2011年 | 1153篇 |
2010年 | 237篇 |
2008年 | 647篇 |
2007年 | 817篇 |
2006年 | 690篇 |
2005年 | 744篇 |
2004年 | 786篇 |
2003年 | 723篇 |
2002年 | 698篇 |
2001年 | 1211篇 |
2000年 | 1177篇 |
1999年 | 767篇 |
1992年 | 754篇 |
1991年 | 539篇 |
1990年 | 600篇 |
1989年 | 573篇 |
1988年 | 554篇 |
1987年 | 579篇 |
1986年 | 622篇 |
1985年 | 780篇 |
1984年 | 552篇 |
1983年 | 475篇 |
1982年 | 436篇 |
1981年 | 498篇 |
1980年 | 555篇 |
1979年 | 1258篇 |
1978年 | 1003篇 |
1977年 | 983篇 |
1976年 | 784篇 |
1975年 | 787篇 |
1974年 | 1172篇 |
1973年 | 978篇 |
1972年 | 1007篇 |
1971年 | 1151篇 |
1970年 | 1572篇 |
1969年 | 1280篇 |
1968年 | 1116篇 |
1967年 | 1154篇 |
1966年 | 1045篇 |
1965年 | 794篇 |
1964年 | 251篇 |
1959年 | 430篇 |
1958年 | 756篇 |
1957年 | 509篇 |
1956年 | 415篇 |
1955年 | 395篇 |
1954年 | 417篇 |
1948年 | 260篇 |
排序方式: 共有10000条查询结果,搜索用时 960 毫秒
361.
G. M. Hanozet M. Simonetta D. Barisio A. Guerritore 《Cellular and molecular life sciences : CMLS》1976,32(10):1246-1249
Summary The three enzymes of ethanol metabolism alcohol dehydrogenase, aldehyde dehydrogenase and acetyl-CoA synthetase in the obligate aerobic yeastRhodotorula gracilis are repressed by glucose and induced by C2 metabolic fuels with a regulatory pattern indicating a correlation in the control mechanisms. To try an identification of the molecular signals involved in the transmission of the inducing stimulus, experiments were carried out by blocking with 2 mM pyrazole the ethanol acetaldehyde metabolic step. Results indicate that ethanol is not specifically required as a molecular signal for induction.This work was supported by a grant from the Italian Consiglio Nazionale delle Ricerche. 相似文献
362.
Summary The central and the peripheral areas of the head-fold stage rat embryo ectoderm develop into both the neural tissue and the epidermis when grafted under the kidney capsule of adult rats.This investigation was supported by the grant No. IV/3 from the Research Foundation of S.R. Croatia, and in part by NIH PL 480 Agreement No. 02-038-1. 相似文献
363.
Summary Tryptic treatment of muscle thick filaments reveals the underlying backbones of aggregatedl-meromyosin as a coli of 3 secondary filaments (helical repeat 130 nm) each in turn a coli of a 3 finer ones. 相似文献
364.
A. J. Rein D. D. Saperstein S. H. Pines P. C. Radlick 《Cellular and molecular life sciences : CMLS》1976,32(10):1352-1354
Summary Using Raman spectroscopy, we demonstrate that low levels of -carotene, lycopene, and xanthophyll give rise to resonance enhanced bands in blood plasma. These results explain the significance of previously unidentified spectral maxima which have been related to the state of health of the blood donor. 相似文献
365.
W. Rittel R. Maier M. Brugger B. Kamber B. Riniker P. Sieber 《Cellular and molecular life sciences : CMLS》1976,32(2):246-248
Summary Assays of 8 synthetic analogues of human calcitonin in rats showed that their hypocalcaemic activity was drastically reduced by deletion of the C-terminal amide group, chain-shortening or opening of the disulphide ring, but unaffected or enhanced by modification of the N-terminal amino group.
II. vgl.R. Maier, B. Kamber, B. Riniker andW. Rittel, Hormon. Metab. Res.7, 511 (1975).
Die hier verwendete, abgekürzte Schreibweise für Peptide folgt den Empfehlungen der IUPAC-IUB Kommission für Biochemische Nomenklatur, J.B.C.247, 977 (1972). Weitere Abkürzungen: HCT, Human-Calcitonin; PCT, Schweinecalcitonin; Bmp, -Mercaptopropionsäure (Desaminocystein); NMet, Normethionin (S-Methylcystein); -OMe, Methylester. 相似文献
II. vgl.R. Maier, B. Kamber, B. Riniker andW. Rittel, Hormon. Metab. Res.7, 511 (1975).
Die hier verwendete, abgekürzte Schreibweise für Peptide folgt den Empfehlungen der IUPAC-IUB Kommission für Biochemische Nomenklatur, J.B.C.247, 977 (1972). Weitere Abkürzungen: HCT, Human-Calcitonin; PCT, Schweinecalcitonin; Bmp, -Mercaptopropionsäure (Desaminocystein); NMet, Normethionin (S-Methylcystein); -OMe, Methylester. 相似文献
366.
H. P. Striebel 《Cellular and molecular life sciences : CMLS》1976,32(4):457-458
Summary 4-isothiocyanato-4-nitrodiphenylamine was found to possess activity against intestinal nematodes in mice, against schistosomes in various hosts including primates and against two filarial species in the mongolian jird. Upon administration in a single oral dose it is equally effective againstS. haematobium, S. mansoni andS. japonicum. 相似文献
367.
M. Aušková K. Řežábek A. Černý M. Krajcrová M. Semonský 《Cellular and molecular life sciences : CMLS》1976,32(10):1310-1310
D-6-Methyl-8-[-isopropylaminoethyl] ergoline-I [VÚFB-10726], beginning from the dose of 0.05 mg/kg p.o., suppresses lactation through the inhibition of prolactin secretion in nursing rats. 相似文献
368.
Summary Rat brain mitochondria contain a significant proportion of poly(A) associated RNA which is higher than that found in microsomes from the same source. When steady state poly(A) RNA of brain mitochondria was analyzed by microelectrophoresis, it displayed a characteristic separation pattern with a large amount of free poly(A). 相似文献
369.
H. N. Nigg J. A. Svoboda M. J. Thompson S. R. Dutky J. N. Kaplanis W. E. Robbins 《Cellular and molecular life sciences : CMLS》1976,32(4):438-439
Summary An ecdysone 20-hydroxylase enzyme system that converts -ecdysone to 20-hydroxyecdysone was prepared from the midgut of the tobacco hornworm prepupa. This partially purified enzyme is NADPH dependent and is localized in the mitochondrial fraction of the midgut tissue. 相似文献
370.
H. A. Robertson 《Cellular and molecular life sciences : CMLS》1976,32(5):552-554
Summary The octopamine, dopamine and noradrenaline content of the brain of the locust,Schistocerca gregaria has been determined using sensitive radiochemical-enzymatic assays. Octopamine and dopamine are present in high concentration but the noradrenaline content is only 1/25 that of octopamine. Both reserpine and fusaric acid (a dopamine--hydroxylase inhibitor) produce a significant depletion of the octopamine stores.The author is a M.R.C. of Canada Fellow. Thanks are due to Drs.A. A. Boulton, A. V. Juorio, andP. H. Wu for helpful discussion. 相似文献