全文获取类型
收费全文 | 4790篇 |
免费 | 314篇 |
国内免费 | 5篇 |
专业分类
5109篇 |
出版年
2023年 | 13篇 |
2022年 | 26篇 |
2021年 | 61篇 |
2020年 | 23篇 |
2019年 | 54篇 |
2018年 | 62篇 |
2017年 | 67篇 |
2016年 | 99篇 |
2015年 | 146篇 |
2014年 | 177篇 |
2013年 | 324篇 |
2012年 | 291篇 |
2011年 | 304篇 |
2010年 | 160篇 |
2009年 | 171篇 |
2008年 | 300篇 |
2007年 | 286篇 |
2006年 | 286篇 |
2005年 | 286篇 |
2004年 | 284篇 |
2003年 | 255篇 |
2002年 | 230篇 |
2001年 | 77篇 |
2000年 | 65篇 |
1999年 | 84篇 |
1998年 | 62篇 |
1997年 | 53篇 |
1996年 | 44篇 |
1995年 | 43篇 |
1994年 | 52篇 |
1993年 | 45篇 |
1992年 | 45篇 |
1991年 | 54篇 |
1990年 | 67篇 |
1989年 | 63篇 |
1988年 | 44篇 |
1987年 | 41篇 |
1986年 | 41篇 |
1985年 | 54篇 |
1984年 | 35篇 |
1983年 | 25篇 |
1982年 | 27篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1978年 | 18篇 |
1976年 | 14篇 |
1970年 | 12篇 |
1969年 | 13篇 |
1968年 | 10篇 |
1967年 | 11篇 |
排序方式: 共有5109条查询结果,搜索用时 0 毫秒
1.
Masayuki Nakamichi 《Primates; journal of primatology》1984,25(2):192-203
Fourteen female Japanese monkeys of the Arashiyama-B group ranging in age from 11 to 29 years were observed to elucidate the
behavioral characteristics of aging monkeys. A positive significant correlation was found between the occurrences of rest
and age, and a negative significant correlation between the occurrences of auto-grooming and age. Younger female monkeys tended
to be in contact with or in proximity to group members, while older female monkeys tended to spend much more time alone. As
for the grooming interactions, younger female monkeys more often groomed others than did older female monkeys. Also, the former
engaged in grooming more frequently than in being groomed, while the latter spent more time in being groomed than in grooming.
The old female monkeys showed no marked decline in rank, but some of them were surpassed by their adult daughters. 相似文献
2.
3.
The cdc6 mutants of Schizosaccharomyces pombe have been classified as being defective in progression through the G2 phase of the cell cycle. We cloned an S. pombe gene that could complement the temperature-sensitive growth of the cdc6-23 mutant. Unexpectedly, the cloned gene was allelic to pol3, which encodes the catalytic subunit of DNA polymerase δ. Integration mapping confirmed that cdc6 and pol3 are identical. The cdc6-23 mutant carries one amino acid substitution in the conserved N3 region of Pol3.
Received: 17 October 1996 / Accepted: 19 November 1996 相似文献
4.
5.
6.
Humans, other primates, and guinea pigs are missing an enzyme L-gulono-gamma-lactone oxidase which catalyzes the last step of L-ascorbic acid biosynthesis. We have recently isolated a cDNA encoding this enzyme of the rat (T. Koshizaka, M. Nishikimi, T. Ozawa, and K. Yagi (1988) J. Biol. Chem. 263, 1619-1621). Northern blot hybridization using this cDNA as a probe demonstrated that guinea pigs lack mRNA for L-gulono-gamma-lactone oxidase. Nevertheless, existence of a DNA sequence related to this enzyme in the genome of this animal was shown by Southern blot hybridization. The human genome was also found to contain a sequence that is hybridizable with the cDNA probe; however, the degree of hybridization was less than those of hybridization with the L-gulono-gamma-lactone oxidase genes of animals possessing the enzyme, suggesting that the human L-gulono-gamma-lactone oxidase gene has diverged more rapidly than the genes of L-ascorbic acid-synthesizing species. This hypothesis was confirmed by comparison of a partial nucleotide sequence of the human gene with that of the rat one. The L-gulono-gamma-lactone oxidase-related sequences in the guinea pig and human genomes may represent the remnants of the gene of the enzyme that were once active but became nonfunctional during the course of evolution. 相似文献
7.
The axial ligations of nitrogenous bases to the five-coordinate chloro-meso-tetraphenylporphyrinatochromium(III) [Cr(III)(TPP)(Cl)] were studied in a non-coordinating solvent, dichloromethane (CH2Cl2), by spectrophotometric methods. A correlation exists between log K for the axial ligation: and pKa for the N-donor ligand. This correlation suggests that ligand to metal σ bonding contributes to the complex formation, rather than does metal to ligand π back-donation. 相似文献
8.
9.
Reverse effect of gram-positive bacteria vs. gram-negative bacteria on adjuvant-induced arthritis in germfree rats 总被引:5,自引:0,他引:5
O Kohashi Y Kohashi T Takahashi A Ozawa N Shigematsu 《Microbiology and immunology》1985,29(6):487-497
Germfree (GF) F344 rats developed severe adjuvant-induced arthritis with a 100% incidence after a single intradermal injection of heat-killed Mycobacterium bovis (BCG). Specific pathogene-free (SPF) rats developed less severe arthritis with a lower incidence. The rats colonized with Escherichia coli or Bacteroides developed mild disease comparable to that in SPF rats. The rats colonized with Bifidobacterium, Propionibacterium acnes, Lactobacillus casei, L. fermentum, L. murini, and L. acidophilus developed more severe disease than that in GF rats. Furthermore, the rats colonized with a mixture of E. coli and the above lactobacilli developed very mild disease similar to that in SPF rats. These results suggest that gram-negative bacteria, such as E. coli and Bacteroides, may suppress the disease, possibly through their lipopolysaccharides, and may be responsible for the lower susceptibility of SPF rats; gram-positive bacteria, such as Bifidobacterium, P. acnes, and lactobacilli, may enhance the disease, possibly through their peptidoglycans; and E. coli may play a dominant role in modulating the development of adjuvant-induced arthritis. 相似文献
10.