全文获取类型
收费全文 | 1437篇 |
免费 | 81篇 |
出版年
2021年 | 11篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2017年 | 20篇 |
2016年 | 29篇 |
2015年 | 36篇 |
2014年 | 30篇 |
2013年 | 80篇 |
2012年 | 52篇 |
2011年 | 53篇 |
2010年 | 36篇 |
2009年 | 32篇 |
2008年 | 80篇 |
2007年 | 63篇 |
2006年 | 65篇 |
2005年 | 68篇 |
2004年 | 52篇 |
2003年 | 68篇 |
2002年 | 57篇 |
2001年 | 51篇 |
2000年 | 68篇 |
1999年 | 50篇 |
1998年 | 17篇 |
1997年 | 12篇 |
1996年 | 14篇 |
1995年 | 19篇 |
1994年 | 7篇 |
1993年 | 13篇 |
1992年 | 37篇 |
1991年 | 32篇 |
1990年 | 25篇 |
1989年 | 29篇 |
1988年 | 23篇 |
1987年 | 27篇 |
1986年 | 23篇 |
1985年 | 21篇 |
1984年 | 19篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1974年 | 16篇 |
1973年 | 7篇 |
1972年 | 14篇 |
1971年 | 9篇 |
排序方式: 共有1518条查询结果,搜索用时 328 毫秒
41.
42.
43.
Yukio Takahata Naoki Koyama Michael A. Huffman Koshi Norikoshi Hisayo Suzuki 《Primates; journal of primatology》1995,36(4):571-574
Based on a sample of 237 live births recorded over a period of 30 years, a tendency for longer interbirth intervals following
the birth of daughters than sons was recognized, in the provisioned Arashiyama troop of Japanese macaques. This may indicate
that female infants were more costly to produce than male infants. This tendency seemed to be independent of a mother’s rank. 相似文献
44.
Molecular cloning of two tandemly arranged peroxidase genes from Populus kitakamiensis and their differential regulation in the stem 总被引:2,自引:0,他引:2
Keishi Osakabe Hirokazu Koyama Shinya Kawai Yoshihiro Katayama Noriyuki Morohoshi 《Plant molecular biology》1995,28(4):677-689
A genomic library was prepared from Populus kitakamiensis and screened with the cDNA for an anionic peroxidase from P. kitakamiensis. One genomic clone was isolated that contained two tandemly oriented genes for anionic peroxidases, prxA3a and prxA4a. Both genes consisted of four exons and three introns; the introns had consensus nucleotides, namely, GT and AG, at their 5 and 3 ends, respectively. The prxA3a and prxA4a genes encoded 347 and 343 amino acid residues, respectively, including putative signal sequences at the amino-termini. Putative promoters and polyadenylation signals were found in the flanking regions of both genes. The sequence of the coding region of prxA3a was completely identical to that of the cDNA clone pA3, whereas the sequence of the coding region of prxA4a was only 73% identical to that of the cDNA clone pA3. Northern blot analysis showed that the patterns of expression of the mRNAs that corresponded to prxA3a and prxA4a differed in stems of P. kitakamiensis. 相似文献
45.
Clarence E. Jones Catherine T. Lee Wayne Skinner Peggy Koyama DeAnn Prescott 《Cancer immunology, immunotherapy : CII》1984,18(2):82-86
Summary The immune status of C57BL/6J mice implanted with Lewis T241 fibrosarcoma or Lewis lung (LL) carcinoma was investigated on days 14 and 28 after implantation. Splenic lymphocyte responses were assessed in mitogen (Con A, LPS) mixed lymphocyte culture (MLC), natural killer (NK), graft-vs-host (GVH), and interleukin production assays. Except for NK-cell cytotoxicity, all other immunologic parameters were either comparable to those in medium-implanted controls or augmented. NK cytotoxicity was reduced in both tumor-bearing groups on day 28. The provision of NK potentiation therapy (-interferon, polyinosinic: polycytidylic acid) to T241 mice under various treatment conditions did not have any significant effect on lung metastasis or survival.The results of this study do not support the thesis that T241-or LL-bearing C57BL/6J mice are generally immunosuppressed. Indeed, when immune functions were assessed on the basis of total splenic activity, each of the measured immunologic parameters was substantially greater in animals with tumors than without. Further it seems improbable, considering the magnitude of the NK-cell defect in T241 mice on days 14 and 28 after implantation and the absence of a therapeutic response to NK-cell stimulants, that NK-cell cytotoxicity is intrinsically associated with resistance to tumor progression in this model. 相似文献
46.
Staphylococcus aureus, which usually forms grape-like clusters, has the ability to form regularly arranged cell packets. These regular cell packets are formed when the activity of its separation enzyme(s) is lost either by treatment with detergents, such as sodium dodecyl sulfate or Trition X-100, or by mutation of the cells. These cell packets consisted of 8 to 64 spherical cells that have a three-dimensional arrangement. Some irregularity in the arragement of cells in packets, however, can be observed by scanning electron microscopy. It is concluded that S. aureus fundametally divides along three definitely oriented planes that are located at right angles to each other. After cell division, the cells usually become translocated due to the action of a separation enzyme(s) to form grape-like clusters. 相似文献
47.
48.
Noriyuki Koyama Kazuo Koshiya Yoshiaki Nosoh 《Archives of biochemistry and biophysics》1980,199(1):103-109
ATPase was purified from an alkalophilic Bacillus. The enzyme has a molecular weight of 410,000 and consists of five types of subunits of molecular weights of 60,000 (α), 58,000 (β), 34,000 (γ), 14,000 (δ), and 11,000 (?). The subunit structure is suggested to be α3β3γδ?. The enzyme is activated by Mg2+ and Ca2+. The pH optima of the enzyme with 0.1 and 2.0 mm Mg2+ are 9 and 6, and those with 1 and 10 mm Ca2+ are 8–9 and 7, respectively. Ca2+-ATPase hydrolyzes only ATP, whereas Mg2+-ATPase hydrolyzes GTP and, to a lesser extent, ATP. The values of V and Km of the enzyme with ATP in the presence of 10 mm Ca2+ or 0.6 mm Mg2+ at pH 7.2 are 17 or 0.5 units/mg protein and 1.2 or 0.3 mm, respectively. The enzyme with Mg2+ is appreciably activated by HCO?3. Relationship of the ATPase to the active transport system in the bacterium is suggested. 相似文献
49.
Establishment and characterization of a cell line from the American opossum (Didelphys virginiana) 总被引:4,自引:0,他引:4
A permanent tissue-cultured cell line (designated OK) has been established from kidney tissue of an adult American opossum. The OK line has been characterized with respect to morphology, chromosome constitution, tissue-culture requirements, and attainable mitotic arrest. The cells are epithelial-like with a stable nondiploid chromosomal modal number of 23. Cells grown in Eagle's minimal essential medium with 10% fetal bovine serum have a mean doubling time of 18 hr. The cell line OK is potentially useful for the isolation and purification of the mammalian X chromosome because of the size differential between the smaller X's and the larger autosomes. 相似文献
50.
An anti-Mos protein monoclonal antibody, 4A6, was used to investigate the distribution of the antigen in the epididymis, in which the c-mos gene is reportedly expressed. The 4A6-reactive antigen was found on the basement membrane and luminal surface of the epithelial cells in the caput epididymis of BALB/c male mice as well as in the proximal corpus epididymis, the cauda epididymis, and the vas deferens. The 4A6 antigen was also found on the luminal surface of the epithelial cells in the epididymis of male germ cell-deficient C57BL/6J-Wv/Wv mice. This confirmed that the 4A6 antigen does not derive entirely from the testicular c-Mos protein but is synthesized in the epididymis. Western blot analysis revealed that the molecular weight of the epididymal 4A6 antigen was 50 kDa, which is unusually high for the c-Mos protein. With its specific distribution in the epididymis, the protein should play a specific role in functions of the epididymis. 相似文献