全文获取类型
收费全文 | 31360篇 |
免费 | 73篇 |
国内免费 | 142篇 |
专业分类
系统科学 | 190篇 |
丛书文集 | 396篇 |
教育与普及 | 82篇 |
理论与方法论 | 103篇 |
现状及发展 | 13684篇 |
研究方法 | 1395篇 |
综合类 | 15289篇 |
自然研究 | 436篇 |
出版年
2013年 | 225篇 |
2012年 | 474篇 |
2011年 | 888篇 |
2010年 | 193篇 |
2008年 | 563篇 |
2007年 | 645篇 |
2006年 | 639篇 |
2005年 | 647篇 |
2004年 | 640篇 |
2003年 | 598篇 |
2002年 | 552篇 |
2001年 | 1065篇 |
2000年 | 1010篇 |
1999年 | 653篇 |
1994年 | 343篇 |
1992年 | 606篇 |
1991年 | 470篇 |
1990年 | 539篇 |
1989年 | 483篇 |
1988年 | 440篇 |
1987年 | 521篇 |
1986年 | 517篇 |
1985年 | 626篇 |
1984年 | 489篇 |
1983年 | 434篇 |
1982年 | 389篇 |
1981年 | 393篇 |
1980年 | 426篇 |
1979年 | 1040篇 |
1978年 | 808篇 |
1977年 | 756篇 |
1976年 | 597篇 |
1975年 | 652篇 |
1974年 | 880篇 |
1973年 | 763篇 |
1972年 | 740篇 |
1971年 | 878篇 |
1970年 | 1171篇 |
1969年 | 856篇 |
1968年 | 780篇 |
1967年 | 843篇 |
1966年 | 741篇 |
1965年 | 530篇 |
1959年 | 292篇 |
1958年 | 481篇 |
1957年 | 345篇 |
1956年 | 323篇 |
1955年 | 269篇 |
1954年 | 268篇 |
1948年 | 235篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
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
182.
E. Knecht J. Renau-Piqueras J. Hernández-Yago S. Grisolía 《Cellular and molecular life sciences : CMLS》1981,37(5):456-457
Summary Protein from resting or phytohemagglutinin-stimulated human peripheral blood T-lymphocytes, pulse-labeled in vitro for 1 h with3H-leucine, had a half-life of 30 h. 相似文献
183.
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
184.
Summary In the sandal plant affected by spike disease, caused by mycoplasma-like organisms, the changes occurring in the 5-and 3-nucleotidase activities were studied and their possible significance discussed. 相似文献
185.
R. L. Tyson C. -j. Chang J. L. McLaughlin Y. Aynehchi J. M. Cassady 《Cellular and molecular life sciences : CMLS》1981,37(5):441-442
Summary A novel sesquiterpene lactone, 9--hydroxyparthenolide (1) was isolated from a chloroform extract ofAnvillea garcini that was collected in Iran. The structure of1 was assigned on the basis of high field NMR decoupling experiments and other spectroscopic evidence. This -methylene lactone has shown significant activity in both the 9KB cell culture and P388 mouse leukemia test systems.The authors acknowledge the support of contract No. N01-CM-97296 from the National Cancer Institute and the use of the Purdue University Biochemical Magnetic Resonance Laboratory (NIH grant No. RR01077). This is paper 16 in the series Potential Antitumor Agents. 相似文献
186.
R. Lenzhofer C. Cerni I. Fröhlich J. Prager H. Pointner 《Cellular and molecular life sciences : CMLS》1981,37(9):1015-1017
Summary The influence of somatostatin on tumor cell growth was studied in vivo in mice (sarcoma 180 ascites tumor and Lewis lung tumor) and in vitro on nontransformed and polyoma-transformed cell lines. 4 or 20 g/100 g of cyclic somatostatin and 4 g/100 g of linear protamin Zn-bound somatostatin were injected s.c. twice daily in the in vivo study. Cyclic somatostatin (1, 4 or 10 g/ml) was added twice daily to the cell cultures. Somatostatin administration influenced neither the survival of animals nor the growth rate of cultured cell lines. *** DIRECT SUPPORT *** A2025117 00011 相似文献
187.
Summary Subdermal injections of PGE2 (5 g) in the rat foot lead to increases in the potentials evoked in sensory nerve branches by the mechanical stimulation of the skin. This sensitization of both A and C fibres complements the previously described hyperalgesic effects of prostaglandins of the E series. 相似文献
188.
Summary -Galactosidase activity in intact cells of 21 species ofStreptomyces was measured using ONPG hydrolysis, without addition of a permeabilizing agent. Differences in the induction efficiency of ONPG-hydrolytic activity by lactose or galactose, which could have taxonomic implications, were observed among the species. 相似文献
189.
G. Cimino A. Crispino S. De Rosa S. De Stefano G. Sodano 《Cellular and molecular life sciences : CMLS》1981,37(9):924-926
Summary Several high molecular weight polyacetylenes have been isolated from the spongePetrosia ficiformis found in dark caves. These compounds are related to, but different from, the polyacetylenes isolated from the same sponge living in its usual habitat.This work is a part of the Progetto finalizzato per l'Oceanografia e i Fondi Marini, CNR, Roma.The authors thank Mr G. Scognamiglio for the HPLC work, Mr C. Di Pinto for the NMR spectra and Mr G. Villani for the collection of the sponge. 相似文献
190.
Nicoletta Crespi-Perellino A. Guicciardi A. Minghetti C. Spalla 《Cellular and molecular life sciences : CMLS》1981,37(3):217-218
Summary
Claviceps purpurea 275 F.I. fed with -aminobutyric acid produces ergostine with the corresponding -hydroxy--aminoacid undiluted by endogenous aminoacid. Almost all the -aminobutyric acid not incorporated into the ergostine remains unchanged in the medium. The significance of these results in the biosynthesis of ergot alkaloids is discussed. 相似文献