全文获取类型
收费全文 | 26849篇 |
免费 | 80篇 |
国内免费 | 118篇 |
专业分类
系统科学 | 309篇 |
丛书文集 | 471篇 |
教育与普及 | 57篇 |
理论与方法论 | 78篇 |
现状及发展 | 12700篇 |
研究方法 | 1095篇 |
综合类 | 12073篇 |
自然研究 | 264篇 |
出版年
2012年 | 367篇 |
2011年 | 652篇 |
2010年 | 162篇 |
2009年 | 154篇 |
2008年 | 426篇 |
2007年 | 531篇 |
2006年 | 491篇 |
2005年 | 479篇 |
2004年 | 428篇 |
2003年 | 479篇 |
2002年 | 462篇 |
2001年 | 898篇 |
2000年 | 900篇 |
1999年 | 544篇 |
1992年 | 510篇 |
1991年 | 401篇 |
1990年 | 466篇 |
1989年 | 415篇 |
1988年 | 427篇 |
1987年 | 451篇 |
1986年 | 440篇 |
1985年 | 545篇 |
1984年 | 433篇 |
1983年 | 366篇 |
1982年 | 350篇 |
1981年 | 386篇 |
1980年 | 402篇 |
1979年 | 894篇 |
1978年 | 758篇 |
1977年 | 691篇 |
1976年 | 611篇 |
1975年 | 591篇 |
1974年 | 810篇 |
1973年 | 646篇 |
1972年 | 638篇 |
1971年 | 786篇 |
1970年 | 988篇 |
1969年 | 787篇 |
1968年 | 765篇 |
1967年 | 789篇 |
1966年 | 671篇 |
1965年 | 489篇 |
1964年 | 179篇 |
1959年 | 276篇 |
1958年 | 441篇 |
1957年 | 279篇 |
1956年 | 254篇 |
1955年 | 248篇 |
1954年 | 228篇 |
1948年 | 149篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
R. K. A. Giger H. R. Loosli M. D. Walkinshaw B. J. Clark J. M. Vigouret 《Cellular and molecular life sciences : CMLS》1987,43(10):1125-1130
Summary We report the synthesis, stereochemistry and preliminary pharmacological evaluation of DCN 203-922, a novel ergot alkaloid of the cyclol type, which contains in its peptide moiety the uncommon amino acid L-allo-isoleucine.Part of this paper was reported by this author at the Herbstversammlung der Schweizerischen Chemischen Gesellschaft, Bern, in October 1986. 相似文献
72.
Summary Larvae of the cabbage white butterfly,Pieris brassicae, have a dietary requirement for linolenic acid (C183n3) and were found to accumulate two other members of the n-3 family, C203n3 and C205n3 (eicosapentaenoic acid) especially in testicular phospholipids. Arachidonic acid was observed in trace amounts only. During diapause the relative titer of eicosapentaenoic acid increased in testicular phospholipids to about 4.2% of the fatty acids. Eicosapentaenoic acid is a possible precursor of prostaglandins, suggesting that prostaglandins of the 3-series predominate in this insect. 相似文献
73.
Summary Cell pairs isolated from adult rat and guinea pig ventricles were used to study the electrical properties of the nexal membrane. Each cell of a pair was connected to a voltage-clamp system so as to enable whole-cell, tight-seal recording. The current-voltage relationship of the nexal membrane was found to be linear, revealing a resistance rn of 2–4 M. rn was insensitive to the sarcolemmal membrane potential (range:–90 to +30 mV), and exerted no time-dependent gating behavior (range: 0.1 to 10 s). Lowering pHi yielded a small increase in rn. Vigorous elevations in [Ca2+]i gave rise to an increase in rn which was associated with a cell shortening. Uncoupling caused by aliphatic alcohols or halothane did not produce cell shortening. Cell pairs were also used to study action potential transfer. 相似文献
74.
Chromosomal localization of human haemoglobin structural genes 总被引:15,自引:0,他引:15
75.
MSI and MSII made on ribosome in idling step of protein synthesis 总被引:56,自引:0,他引:56
76.
The significance of glycosylated proteins 总被引:15,自引:0,他引:15
77.
Growth of the bacterial cell 总被引:56,自引:0,他引:56
78.
RNA-DNA hybrids at the cytological level 总被引:37,自引:0,他引:37
79.
G. Deby-Dupont J. Pincemail A. Thirion C. Deby M. Lamy P. Franchimont 《Cellular and molecular life sciences : CMLS》1991,47(9):952-957
In order to obtain a radioimmunoassay (RIA) technique for the measurement of human plasma myeloperoxidase (MPO), we purified the enzyme from polymorphonuclear granulocytes (neutrophils), and compared three methods of labeling it with125Iodine: chloramine T, lactoperoxidase, and an original technique of self labeling based on the ability of the enzyme to oxidize and bind125I in the presence of H2O2. The chloramine T technique produced a degraded protein, as well shown by a high non-specific binding of tracer to antibody. The lactoperoxidase technique did not succeed in labeling MPO with an adequate specific activity. In contrast, the self-labeling method gave a stable tracer with a specific activity of 23 Ci/gmg MPO (85 MBq), a satisfactory level of immunoreactivity, and a low-specific binding (3%). After labeling, purification of tracer was achieved by gel filtration chromatography in phosphate buffer (0.05 M; pH7) to which 0.1% poly-L-lysine was added. The labeled molecule remained stable for 40 days and could be used for RIA with a polyclonal antibody raised in rabbits. 相似文献
80.
J. L. Lacuara S. R. de Barioglio P. P. de Oliva A. S. Bernacchi A. F. de Culasso J. A. Castro B. M. Franke de Cazzulo J. J. Cazzulo 《Cellular and molecular life sciences : CMLS》1991,47(6):612-616
Summary The tricyclic anti-calmodulin drug trifluoperazine (TFP) inhibited growth and motility of epimastigotes ofTrypanosoma cruzi, at concentrations lower than 100 M, and motility and infectivity of the bloodstream trypomastigote form at 200 M. Electron microscopy of TFP-treated epimastigotes showed that the major effect was at the mitochondrial level, with gross swelling and disorganization. The oligomycin-sensitive, mitochondrial ATPase was completely inhibited by 20 M TFP, and the same drug concentration caused a 60% decrease in intracellular ATP content. The results suggest that the trypanocidal effect of TFP may be related more to mitochondrial damage than to the well-known anticalmodulin effect of the drug. 相似文献