全文获取类型
收费全文 | 12595篇 |
免费 | 34篇 |
国内免费 | 62篇 |
专业分类
系统科学 | 74篇 |
丛书文集 | 50篇 |
教育与普及 | 41篇 |
理论与方法论 | 65篇 |
现状及发展 | 4240篇 |
研究方法 | 825篇 |
综合类 | 7135篇 |
自然研究 | 261篇 |
出版年
2016年 | 64篇 |
2013年 | 69篇 |
2012年 | 320篇 |
2011年 | 636篇 |
2010年 | 123篇 |
2009年 | 62篇 |
2008年 | 373篇 |
2007年 | 421篇 |
2006年 | 390篇 |
2005年 | 447篇 |
2004年 | 451篇 |
2003年 | 368篇 |
2002年 | 431篇 |
2001年 | 433篇 |
2000年 | 452篇 |
1999年 | 305篇 |
1996年 | 61篇 |
1994年 | 274篇 |
1992年 | 257篇 |
1991年 | 204篇 |
1990年 | 234篇 |
1989年 | 198篇 |
1988年 | 185篇 |
1987年 | 191篇 |
1986年 | 204篇 |
1985年 | 266篇 |
1984年 | 205篇 |
1983年 | 172篇 |
1982年 | 145篇 |
1981年 | 149篇 |
1980年 | 148篇 |
1979年 | 339篇 |
1978年 | 272篇 |
1977年 | 222篇 |
1976年 | 193篇 |
1975年 | 197篇 |
1974年 | 211篇 |
1973年 | 183篇 |
1972年 | 208篇 |
1971年 | 253篇 |
1970年 | 310篇 |
1969年 | 231篇 |
1968年 | 228篇 |
1967年 | 199篇 |
1966年 | 224篇 |
1965年 | 151篇 |
1959年 | 75篇 |
1958年 | 123篇 |
1957年 | 81篇 |
1954年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
S. Fujino K. Satoh T. Nakai K. Togashi T. Kado M. Fujino T. Arima M. Fujino 《Cellular and molecular life sciences : CMLS》1993,49(2):138-144
The excitation-contraction (E-C) coupling process in single twitch fibres from frog toe muscle was inhibited selectively by phenylglyoxal (PGO), a specific guanidyl modifying reagent. A new protein (31.5 kDa), which has PGO-binding ability and seems to play a key role in the E-C coupling process, was solubilized from transverse tubule membrane-junctional sarcoplasmic reticulum complexes (TTM-JSR) of frog skeletal muscles, using14C-PGO. The monoclonal antibody against this protein applied extracellularly inhibited the E-C coupling process of the single fibres. This protein appears to constitute the very first step of input for E-C coupling. It is considered to behave as an indispensable part of an electrometer to measure membrane potentials. Therefore, the name electrometrin is suggested for the new protein. 相似文献
72.
The cyclicity and intensity of gastric motlity were examined following glucose injection into the portal vein with an intragastric balloon in anesthetized rats. Enhanced gastric motility caused by insulin administration was influenced by 4 mM glucose (25 l) injected into the portal vein; glucose provoked a shift in the cyclicity power spectrum without any change in intensity. The peak power spectrum shifted from 4.0–5.0 cpm to 2.0–3.0 cpm. Hepatic branch vagotomy abolished the response.The results suggest that glucose signals in the hepatic vagal branch modulate the cyclicity of gastric motiligy. 相似文献
73.
H. Fujioka K. Horiike M. Takahashi T. Ishida M. Kinoshita M. Nozaki 《Cellular and molecular life sciences : CMLS》1993,49(1):47-50
The vascular effects of 2-mercaptoethanol, cysteamine, L-cysteine, glutathione (GSH), cystamine and oxidized GSH (GSSG) on the isometric tension of isolated dog coronary arterial strips were examined, and these effects were compared with the triphasic response induced by dithiothreitol (DTT); a rapid and weak contraction (phase A), an intervening slow relaxation (phase B) and a slowly-developing strong contraction (phase C) which we previously reported. The responses of the arteries induced by 2-mercaptoethanol, cysteamine and L-cysteine consisted of phases A, B and C. The order of contractile potency (ED50 of phase C) was DTTL-cysteine>2-mercaptoethanolcysteamine, while the order of relaxant potency (ED50 of phase B) was DTT>cysteamine2-mercaptoethanol. GSSG and cystamine mainly produced relaxation, which corresponded to phase B. The phase C contraction was specific to the reduced forms of thiols, except for GSH, which produced only relaxation. The participation of endothelial cells was not essential for the contracting or relaxing effects of the thiol compounds. The phase C contraction was depressed by W-7, a calmodulin antagonist, while phase A was not. Therefore calmodulin-dependent protein kinases may participate in phase C, not in phase A. 相似文献
74.
W. F. Osswald J. P. Shapiro R. E. McDonald R. P. Niedz R. T. Mayer 《Cellular and molecular life sciences : CMLS》1993,49(10):888-892
Several acidic chitinase and chitosanase isoforms were found in 4-week-old nonembryogenic sweet orange (Valencia [Citrus sinensis (L.) Osbeck]) callus tissue. Two isoforms (designated A1-CF1 and A1-CF2) were purified to homogeneity using HPLC size exclusion, anion exchange, and chromatofocusing techniques. Both hydrolase isoforms exhibited activity with either colloidal chitin or solubilized shrimp shell chitosan. Specific activities for the purified isoforms could not be calculated because of the lack of protein and contamination of ampholytes. However, the specific activities for chitinase and chitosanase after anion exchange were respectively 404 nmol GlcNAc per min per mg protein and 2,475 nmol GlcN per min per mg protein. The Mr for both enzymes was 30,500. The homogeneous proteins cross-reacted in western blots with antiserum against a basic class I potato leaf chitinase. 相似文献
75.
Summary Replicative DNA synthesis in permeable mouse sarcoma cells was more sensitive to ethidium bromide (EtBr) than bleomycin-induced unscheduled DNA synthesis (UDS). A similar difference in sensitivity to EtBr was observed between DNA polymerases and . The difference in sensitivity to EtBr of replicative DNA synthesis and UDS in the present system seems to reflect mainly the sensitivity difference between DNA polymerases and .Acknowledgments. The authors wish to thank Nippon Kayaku Co. (Tokyo, Japan) for providing copper-free bleomycin A2. This research was supported in part by a grant from the Japan Ministry of Education, Science and Culture. 相似文献
76.
77.
T. T. Yen J. A. Allan D. V. Pearson J. M. Acton 《Cellular and molecular life sciences : CMLS》1978,34(12):1542-1543
Summary Treating VY/WfL-A
vy
/a mice with 5-androstan-17-one, a mammalian glucose-6-phosphate dehydrogenase inhibitor, prevented the mice from becoming obese. The weight difference between treated and controlA
vy
/a mice was mainly due to a decreased accumulation of triacylglycerol. The compound did not suppress appetite, had no detectable toxicity and did not affect the lipogenesis rates in the liver and carcass. The weight-controlling effect of 5-androstan-17-one inA
vy
/a mice was reversible upon withdrawal of treatment.The authors wish to thank Mr W.R. Gibson and Drs C.G. Culbertson and P.N. Harris for performing the pathological examinations. 相似文献
78.
79.
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
80.
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