全文获取类型
收费全文 | 99314篇 |
免费 | 7870篇 |
国内免费 | 32篇 |
出版年
2021年 | 898篇 |
2018年 | 1371篇 |
2017年 | 1284篇 |
2016年 | 1745篇 |
2015年 | 1857篇 |
2014年 | 2230篇 |
2013年 | 3122篇 |
2012年 | 3419篇 |
2011年 | 3519篇 |
2010年 | 2585篇 |
2009年 | 2190篇 |
2008年 | 3145篇 |
2007年 | 3100篇 |
2006年 | 2923篇 |
2005年 | 2732篇 |
2004年 | 2730篇 |
2003年 | 2609篇 |
2002年 | 2419篇 |
2001年 | 4441篇 |
2000年 | 4217篇 |
1999年 | 3265篇 |
1998年 | 1057篇 |
1997年 | 1048篇 |
1996年 | 926篇 |
1995年 | 845篇 |
1993年 | 837篇 |
1992年 | 2453篇 |
1991年 | 2463篇 |
1990年 | 2466篇 |
1989年 | 2215篇 |
1988年 | 2069篇 |
1987年 | 1983篇 |
1986年 | 1828篇 |
1985年 | 1821篇 |
1984年 | 1498篇 |
1983年 | 1300篇 |
1982年 | 934篇 |
1981年 | 877篇 |
1979年 | 1440篇 |
1978年 | 1128篇 |
1977年 | 1018篇 |
1976年 | 976篇 |
1975年 | 1156篇 |
1974年 | 1262篇 |
1973年 | 1348篇 |
1972年 | 1187篇 |
1971年 | 1043篇 |
1970年 | 928篇 |
1969年 | 956篇 |
1968年 | 838篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
D. V. Popov D. V. Swirkun A. I. Netreba O. S. Tarasova A. B. Prostova I. M. Larina A. S. Borovik O. L. Vinogradova 《Human physiology》2006,32(5):609-614
The study was designed to test the hypothesis that, during strength training, a restricted blood supply to the working muscles stimulates the secretion of anabolic hormones and an increase in the muscle mass and strength can be achieved with significantly lower training loads. During eight weeks, three times a week, 18 young, physically active males trained their leg extensor muscles. Nine subjects (group I) worked at 80% of the maximal voluntary contraction (MVC), whereas the rest (group II) performed their exercise without relaxation and at a lower load (50% MVC). The total training load in group II was significantly lower than in group I (77 ± 5 vs. 157 ± 7 kJ, respectively). The eight-week training of both groups significantly increased the mean maximum strength (by 35 and 21% in groups I and II, respectively) and volume (by 17 and 9%, respectively) of the muscles trained (however, the differences between the groups with respect to these changes were nonsignificant). Group I displayed a higher increase in the blood level of creatine phosphokinase than group II, while group II showed a greater increase in the blood concentration of lactate. In contrast to group I, group II displayed a significant increase in the blood concentrations of growth hormone, insulin-like growth factor 1 (IGF-1), and cortisol. Hence, the suggestion that the secretion of metabolic hormones is triggered by a metabolic, rather than mechanical, stimulus from working muscles seems plausible. 相似文献
143.
We have constructed four deletion derivatives of the cloned dnaK gene. Plasmid pDD1, in which the last 10 amino acids of the DnaK protein have been replaced by three different amino acids derived from the pBR322 vector, was as effective as plasmid pKP31, from which it was derived, in restoring the ability of a dnaK null mutant, Escherichia coli BB1553, to plate lambda phage and to grow at high temperatures. The other three mutations, involving much larger deletions of the dnaK gene, did not restore the ability to plate lambda phage or the ability to grow at high temperatures. Plasmid pKUC2, which contains the whole dnaK gene and its promoters, was capable of restoring the ability of E. coli BB1553 to plate lambda phage but, surprisingly, it did not restore the ability to grow at high temperatures, even though it was shown that the DnaK protein was efficiently expressed in these cultures. By transposon mutagenesis and sub-cloning, we have shown the presence of a second gene in plasmid pKP31 which is required for high-temperature growth of E. coli BB1553. This gene, which we call htg A, is presumably also defective in the dnaK null mutant E. coli BB1553. We have also demonstrated that the inability of E. coli K756 to grow above 43.5 degrees C is complemented by sub-clones which contain the htg A gene, but not by plasmid pKUC2. 相似文献
144.
E. I. Domaratskaya E. I. Bueverova O. D. Payushina V. I. Starostin 《Biology Bulletin》2005,32(3):216-220
Effect of alkylating agent dipin was studied on hematopoietic (CFU-S) and stromal (CFU-F) progenitor cells. Single administration of dipin (0.06 mg/g) to adult (CBA × C57Bl/6) F1 hybrid mice induced a long-term (2 years) oscillations in the numbers of day 7 CFU-S and day 11 CFU-S in the bone marrow and spleen. Dipin also damaged the hematopoietic stroma as indicated by decreased numbers of CFU-F which remained low for at least a year. The capacity of stromal cells to form ectopic hematopoietic foci was considerably decreased and also remained low for 10 months. The obtained data suggest high dipin sensitivity of the earliest hematopoietic and stromal cells. The dynamics of CFU-S numbers in the hematopoietic organs supports their functioning on the basis of clonal succession (Kay, 1965).__________Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 3, 2005, pp. 267–272.Original Russian Text Copyright © 2005 by Domaratskaya, Bueverova, Payushina, Starostin. 相似文献
145.
146.
O Chisaka K Araki T Ochiya T Tsurimoto W Hiranyawasitte-Attatippaholkun N Yanaihara K Matsubara 《Gene》1987,60(2-3):183-189
A fused gene containing 94% of the hepatitis B virus (HBV) open reading frame X was expressed in Escherichia coli, and its 17-kDa product was purified by ion-exchange chromatography. Antibody elicited against the X-gene product reacted with materials proximal to the nuclear membrane of a human hepatoblastoma cell line producing HBV particles. No such reaction was observed with the same cell line that did not produce HBV particles. 相似文献
147.
148.
149.
The epididymis of buffalo is differentiated into 6 regions. The head represents the first 3 regions, the body the 4th region and the tail the 5th and 6th region. At 3-30 weeks, the epithelium is simple high columnar with few basal cells in region I, simple low columnar with few basal cells in region II, pseudostratified low columnar in regions III, IV, V, and pseudostratified low columar in region VI. As age advances, the epithelium increases in height and shows a tendency toward advanced pseudostratification. The basal cells are greater in number in regions III, IV and V than in the other regions of the epididymis. The epithelial cells contain stereocilia in region I at 3 weeks and regions III, IV and V at 30 weeks, whereas they are absent in regions II and VI. The tubules in region I are the smallest in diameter while the tubules in region VI have the largest diameter. 相似文献
150.