全文获取类型
收费全文 | 26413篇 |
免费 | 119篇 |
国内免费 | 255篇 |
专业分类
系统科学 | 411篇 |
丛书文集 | 429篇 |
教育与普及 | 99篇 |
理论与方法论 | 84篇 |
现状及发展 | 9756篇 |
研究方法 | 1098篇 |
综合类 | 14253篇 |
自然研究 | 657篇 |
出版年
2013年 | 303篇 |
2012年 | 576篇 |
2011年 | 1259篇 |
2010年 | 404篇 |
2009年 | 384篇 |
2008年 | 650篇 |
2007年 | 777篇 |
2006年 | 753篇 |
2005年 | 690篇 |
2004年 | 563篇 |
2003年 | 453篇 |
2002年 | 467篇 |
2001年 | 820篇 |
2000年 | 875篇 |
1999年 | 610篇 |
1994年 | 309篇 |
1992年 | 492篇 |
1991年 | 414篇 |
1990年 | 429篇 |
1989年 | 384篇 |
1988年 | 359篇 |
1987年 | 386篇 |
1986年 | 375篇 |
1985年 | 469篇 |
1984年 | 404篇 |
1983年 | 304篇 |
1982年 | 288篇 |
1981年 | 286篇 |
1980年 | 325篇 |
1979年 | 721篇 |
1978年 | 569篇 |
1977年 | 557篇 |
1976年 | 434篇 |
1975年 | 493篇 |
1974年 | 616篇 |
1973年 | 540篇 |
1972年 | 543篇 |
1971年 | 642篇 |
1970年 | 748篇 |
1969年 | 621篇 |
1968年 | 604篇 |
1967年 | 613篇 |
1966年 | 577篇 |
1965年 | 429篇 |
1959年 | 223篇 |
1958年 | 347篇 |
1957年 | 252篇 |
1956年 | 191篇 |
1955年 | 198篇 |
1954年 | 190篇 |
排序方式: 共有10000条查询结果,搜索用时 552 毫秒
161.
The spontaneous conversion of mammalian cyclic GMP-dependent protein kinase (G-PK) into modulator-dependent protein kinase (type II) (M-PKII) in the absence of cGMP or histone was observed in vitro. The findings, together with similarity in substrate protein specificity, suggest that M-PKII is the catalytic subunit of mammalian G-PK. 相似文献
162.
At ambient temperatures (Ta) of both 8 and 22 degrees C, intraventricular administration of TRH (10-80 microgram) produced a dose-dependent hypothermia in rats. The hypothermia was due to both decreased metabolic heat production and cutaneous vasodilatation. In contrast, at 30 degrees C Ta, TRH increased metabolic heat production (due to behavioral excitation) and led to hyperthermia. 相似文献
163.
Summary Silver-staining has been used to identify the nucleolus organizer regions (NORs) in the bharal. These show homology with sheep, goat, cattle and aoudad. The association of the NORs on both telomeres of chromosome 3 results in a ring chromosome. 相似文献
164.
H. L. Weinberg 《Cellular and molecular life sciences : CMLS》1980,36(5):548-549
Summary The hemolymph volume ofHeliothis zea larvae was determined by the amaranth dye method and found to vary from 28 to 288 l. It averaged 30.6% of b.wt, a value comparable to that obtained with C14 inulin. Amaranth became evenly distributed in the hemocoele in 3–5 min. 相似文献
165.
Summary The C-terminal amino acid sequences of human and of porcine antithrombin III have been determined as Gly-Arg-Val-Ala-Asn-Pro-Cys-Val-Lys and Gly-Arg-Val-Ala-Asn-Pro-Cys, respectively. These sequences are highly homologous with the C-terminal sequence of human -1-proteinase inhibitor. 相似文献
166.
T. Stojanovié B. M. Djuričić B. B. Mršulja 《Cellular and molecular life sciences : CMLS》1980,36(12):1348-1350
Summary The activity of (Na++K+)-ATPase and acetylcholine esterase were folloed in rat brain cerebral cortex, caudate, thalamus, hippocampus and medulla after i.v. administration of physostigmine. Both enzymes were found to be inhibited in a dose-dependent manner. The most pronounced inhibition of (Na++K+)-ATPase was found in caudate. where the highest activity of acetylcholine esterase is found.These studies were supported by a grant from the Union of Science of Republic Serbia, No. 40404-14. 相似文献
167.
Summary Contrary to Srdi and Gloor's report, we find crystal cells (cc) in the lymph glands ofD. melanogaster larvae; the size and number of inclusions in the cc cannot be used to distinguish the 2 sibling species,D. melanogaster andD. simulans; cc in the hemocoel are not phagocytic cells; the surface properties of the lamellocytes are consistent with their derivation from plasmatocytes and not cc.Supported by grant No. CA16619 awarded by the National Cancer Institute, DHEW, USPHS. 相似文献
168.
Comparison of white pock (h) mutants of monkeypox virus with parental monkeypox and with variola-like viruses isolated from animals 总被引:5,自引:0,他引:5
Monkeypox mutants arising spontaneously or after serial, high multiplicity passage were characterized phenotypically and by restriction endonuclease mapping. Some resemble "whitepox" and variola viruses in several of the markers tested but all are distinguishable phenotypically from these. None resembles "whitepox" viruses in genome structure although near-terminal deletions or symmetrical, terminal rearrangements, relative to parental monkeypox, occurred. "Whitepox" viruses isolated from animals closely resemble variola in both phenotype and genome structure. 相似文献
169.
L. de Napoli E. Fattorusso Silvana Magno L. Mayol 《Cellular and molecular life sciences : CMLS》1981,37(11):1132-1132
Summary Furocaulerpin, an acetylenic sesquiterpenoid possessing a furan ring, has been isolated from the marine algaCaulerpa prolifera, and its stereostructure elucidated mainly on the basis of physico-chemical data.This work was carried out in the frame work of the Progetto Finalizzato per l'Oceanografia e i Fondi Marini, CNR, Rome. Thanks are due to the Centro di Metodologie Chimico-Fisiche of the University of Naples (Mr I. Giudicianni) for the determination of PMR-spectra. 相似文献
170.
T. Kuroiwa S. Nishibayashi S. Kawano T. Suzuki 《Cellular and molecular life sciences : CMLS》1981,37(9):969-971
Summary DNA-containing areas in various phages (T4, , T7 and 29) could be observed at the light microscopic level using ethidium bromide epi-fluorescent microscopy. The fluorescent intensity per phage was in linear proportion to the DNA content in each phage.Acknowledgements. This work was supported in part by the grant No. 521708 and No. 511212 from the Japan Ministry of Education, Science and Culture. 相似文献