全文获取类型
收费全文 | 1935篇 |
免费 | 238篇 |
出版年
2023年 | 9篇 |
2022年 | 17篇 |
2021年 | 44篇 |
2020年 | 19篇 |
2019年 | 22篇 |
2018年 | 32篇 |
2017年 | 35篇 |
2016年 | 49篇 |
2015年 | 76篇 |
2014年 | 75篇 |
2013年 | 111篇 |
2012年 | 125篇 |
2011年 | 132篇 |
2010年 | 90篇 |
2009年 | 81篇 |
2008年 | 121篇 |
2007年 | 129篇 |
2006年 | 106篇 |
2005年 | 104篇 |
2004年 | 90篇 |
2003年 | 99篇 |
2002年 | 76篇 |
2001年 | 32篇 |
2000年 | 31篇 |
1999年 | 28篇 |
1998年 | 23篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 24篇 |
1991年 | 25篇 |
1990年 | 14篇 |
1989年 | 22篇 |
1988年 | 20篇 |
1987年 | 10篇 |
1986年 | 24篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1974年 | 8篇 |
1968年 | 9篇 |
排序方式: 共有2173条查询结果,搜索用时 31 毫秒
51.
52.
Livers from normally fed male and female rats were perfused in vitro with different amounts of oleate, and the production and properties of the very low density lipoprotein (VLDL) were studied. The mobility of the VLDL in the zonal ultracentrifuge was dependent on the uptake of free fatty acid and on the sex of the animal from which the liver was obtained. A higher proportion of the VLDL secreted by livers from females displayed a more rapid mobility in the zonal ultracentrifuge and, in addition, contained less phospholipid and cholesterol per mole triglyceride than the VLDL from the male, suggestive of larger size of the VLDL secreted by livers from the female rats. Such differences were diminished when the VLDL was compared at equal output of triglyceride but unequal uptake of free fatty acid. These data suggest that the properties of the VLDL are only secondarily modulated by sex, and primarily result from differences in the capacities of livers from either male or female rats to synthesize triglyceride for transport as VLDL. The quantity of triglyceride secreted, regardless of sex, may be an important determinant of both size and number of the VLDL particles. The incorporation of endogenous hepatic fatty acid into VLDL triglyceride was diminished in livers from both sexes by increased uptake of oleate. The greater output of VLDL triglyceride by livers from female animals was dependent on both exogenous and endogenous fatty acids when relatively small quantities of exogenous oleate were available for uptake by the liver. The proportion of palmitate and oleate in the phospholipid of the VLDL secreted by livers from male rats decreased and the content of arachidonate increased with increasing uptake of oleate; no differences were observed in the composition of the phospholipid fatty acids among the various experimental female groups, although these contained more stearate and less oleate and linoleate compared to the male groups. The change of fatty acid composition of the VLDL phospholipid may reflect inclusion of specific types of phospholipid in the VLDL structure for transport of triglyceride from the liver under particular conditions. 相似文献
53.
Effect of araC gene product on catabolite repression in the L-arabinose regulon. 总被引:3,自引:3,他引:0
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The araCi protein differs in stability from araC+ protein and alters the concentration of cyclic adenosine-3', 5'-monophosphate required to maximally stimulate L-arabinose isomerase synthesis in an in vitro protein-synthesizing system. 相似文献
54.
F H Wilcox 《The Journal of heredity》1975,66(1):19-22
Rate of electrophoretic migration of prealbumin-2 of mouse blood plasma was found to be controlled by three autosomal codominant alleles. Presence and absence of a component next to albumin (prealbumin-4) was shown to be controlled by autosomal dominant and recessive alleles, respectively, and to be affected by sex. Evidence was presented for close linkage of the Pre-2 and Pre-4 loci, and for the control of albumin conformation by a separate locus. 相似文献
55.
R G Wilcox 《BMJ (Clinical research ed.)》1978,1(6126):1513-1515
In 70 obese women no correlation was found between body weight and serum cholesterol or triglyceride concentrations, but there was a significant correlation between weight and blood pressure. Weight reduction by diet or jejunoileal shunt was not accompanied by any significant change in serum lipid concentrations other than the decrease in serum cholesterol expected after intestinal bypass. Twelve months after bypass surgery was carried out on 14 patients, however, both systolic and diastolic blood pressures were significantly reduced and at levels appropriate to the patients'' new weights. These results suggest that obesity in women cannot be taken to indicate the presence of hyperlipidaemia and that sustained weight loss may lower blood pressure. 相似文献
56.
Nitrosoguanidine induced mutants of Anabaena cylindrica have been obtained, which are altered in heterocyst spacing. In the wild type organism the pattern is composed of single intercalary heterocysts. The mutant patterns fall into several classes: those with only terminal heterocysts, with both terminal and intercalary heterocysts, with groups of heterocysts and those totally lacking heterocysts. The mutants are described in detail, and the various pattern modifications are interpreted in terms of a model we have proposed. 相似文献
57.
Antoaneta Trendafilova Victoria Ivanova Miroslav Rangelov Milka Todorova Gulmira Ozek Suleyman Yur Temel Ozek Ina Aneva Ralitza Veleva Veselina Moskova‐Doumanova Jordan Doumanov Tanya Topouzova‐Hristova 《化学与生物多样性》2020,17(4)
Chlorogenic (5‐CQA), 1,5‐, 3,5‐, 4,5‐ and 3,4‐dicaffeoylquinic (DCQA) acids were identified and quantified in the methanol extracts of Inula oculus‐christi L., I. bifrons L., I. aschersoniana Janka var. aschersoniana, I. ensifolia L., I. conyza (Griess .) DC. and I. germanica L. by HPLC analysis. The amount of 5‐CQA varied from 5.48 to 28.44 mg/g DE and the highest content was detected in I. ensifolia. 1,5‐DCQA (4.05–55.25 mg/g DE) was the most abundant dicaffeoyl ester of quinic acid followed by 3,5‐DCQA, 4,5‐DCQA and 3,4‐DCQA. The extract of I. ensifolia showed the highest total phenolic content (119.92±0.95 mg GAE/g DE) and exhibited the strongest DPPH radical scavenging activity (69.41±0.55 %). I. bifrons extract was found to be the most active sample against ABTS.+ (TEAC 0.257±0.012 mg/mL) and the best tyrosinase inhibitor. The studied extracts demonstrated a low inhibitory effect towards acetylcholinesterase and possessed low cytotoxicity in concentration range from 10 to 300 μg/mL toward non‐cancer (MDCK II) and cancer (A 549) cells. 相似文献
58.
59.
60.
Wetlands Ecology and Management - Gas drilling into the Marcellus Shale play has been linked to environmental issues, including potential impacts on wildlife. In 2009, three separate accidents... 相似文献