全文获取类型
收费全文 | 360516篇 |
免费 | 28030篇 |
国内免费 | 92篇 |
出版年
2018年 | 4182篇 |
2017年 | 4033篇 |
2016年 | 5093篇 |
2015年 | 4957篇 |
2014年 | 6608篇 |
2013年 | 9473篇 |
2012年 | 11067篇 |
2011年 | 11918篇 |
2010年 | 8298篇 |
2009年 | 7314篇 |
2008年 | 10596篇 |
2007年 | 11074篇 |
2006年 | 10582篇 |
2005年 | 9875篇 |
2004年 | 10100篇 |
2003年 | 9733篇 |
2002年 | 9709篇 |
2001年 | 15829篇 |
2000年 | 15707篇 |
1999年 | 12021篇 |
1998年 | 3817篇 |
1997年 | 3774篇 |
1996年 | 3427篇 |
1995年 | 3164篇 |
1992年 | 9531篇 |
1991年 | 9726篇 |
1990年 | 9487篇 |
1989年 | 9491篇 |
1988年 | 8753篇 |
1987年 | 8245篇 |
1986年 | 7530篇 |
1985年 | 7852篇 |
1984年 | 6333篇 |
1983年 | 5317篇 |
1982年 | 3614篇 |
1981年 | 3180篇 |
1980年 | 3132篇 |
1979年 | 5962篇 |
1978年 | 4646篇 |
1977年 | 4230篇 |
1976年 | 3993篇 |
1975年 | 4803篇 |
1974年 | 5313篇 |
1973年 | 5269篇 |
1972年 | 4790篇 |
1971年 | 4485篇 |
1970年 | 3896篇 |
1969年 | 3795篇 |
1968年 | 3554篇 |
1967年 | 3201篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
961.
962.
S. V. Ryzhkov 《Plasma Physics Reports》2011,37(13):1075-1081
As applied to a tokomak, a magnetic trap for confinement of a plasma with an inverted field or a magnetic field reversed configuration
(FRC) is one of the most promising alternatives of the systems with high β. A brief review of the latest data on FRC and potential
directions of using such configurations in addition to energy generation in thermonuclear reactors (TNRs) is proposed. 相似文献
963.
Frank H. Gleason Steve K. Schmidt Agostina V. Marano 《Extremophiles : life under extreme conditions》2010,14(5):417-425
Zoosporic true fungi are thought to be ubiquitous in many ecosystems, especially in cool, moist soils and freshwater habitats
which are rich in organic matter. However, some of the habitats where these fungi are found may periodically experience extreme
conditions, such as soils in extremely dry, hot and cold climates, acidic and alkaline soils, polluted rivers, anaerobic soil
and water, saline soil and water, periglacial soils, oligotrophic soils, tree canopies and hydrothermal vents. It is clear
that many ecotypes of zoosporic true fungi have indeed adapted to extreme or stressful environmental conditions. This conclusion
is supported by studies in both the field and in the laboratory. Therefore, in our opinion, at least some true zoosporic fungi
can be considered to be extremophiles. 相似文献
964.
The histones from slime mold Physarum polycephalum and calf thymus were characterized in terms of some physico-chemical properties. The molecular weights of six principal histone fractions of Ph. polycephalum were found to be the following: P1--22 700, P3--15 700, P4a--15 000, P4b--14 300, P5--12 800 and P6--10 500. Electrophoretically homogenous histone fractions H1, H2b and H4 of calf thymus and histones P1, P3, P4b and P6 of slime mold were obtained by gel-filtration on Acrylex P-60. These findings suggest that fractions P1, P4a, P4b, P5 and P6 of slime mold Ph. polycephalum are homologus with respect to the histone fractions H1, H3, H2b, H2a and H4 of calf thymus. Only fraction P3 has no corresponding fraction in the calf thymus histones; a fraction corresponding to histone P3 of slime mold was absent. 相似文献
965.
966.
967.
ACTH stimulation of adenyl cyclase in adrenal homogenates 总被引:6,自引:0,他引:6
968.
The stimulation of the phosphorylation of ribosomal protein S6 by cycloheximide and puromycin 总被引:7,自引:0,他引:7
The administration of cycloheximide or puromycin to rats in amounts that all but completely inhibited hepatic protein synthesis caused an increase in the amount of radioactive phosphate incorporated into the liver ribosomal protein S6; there was also an increase in the prominence of the derivatives of S6 which contain increasing numbers of phosphorylated serine residues. 相似文献
969.
It has been previously reported that fasting may result in decreased lung surfactant production. In order to investigate this relationship and the role of nutrition in lung phospholipid synthesis, 21-day-old rats were exposed for 60 h to one of five dietary regimens: standard rat chow (controls), fasting, pure glucose, pure fat, or pure protein. After the period of fasting there was a 33% decrease in lung protein content, but there was no change in DNA content. Exposure to any of the experimental diets resulted in a decrease in tissue total phospholipid and phosphatidylcholine content per lung, but not per unit lung protein. Similarly lung lavage phospholipid and phosphatidylcholine content was decreased by 25% after fasting when expressed per lung or per unit DNA, but not per unit protein. Pulmonary cholinephosphotransferase (EC 2.7.8.2) activity was decreased in the fasted animals and those fed the protein diet, but not in the glucose or fat-fed animals. The activities of acetyl-CoA carboxylase (EC 6.4.1.2) and microsomal fatty acid elongation were decreased in all the experimental groups except for the glucose-fed group. It is concluded that fasting results in a decrease in lung cell size but not in lung cell number. Total phospholipid and phosphatidylcholine content in lung tissue and lung lavage is decreased per cell but not per unit cell mass. 相似文献
970.