全文获取类型
收费全文 | 28269篇 |
免费 | 2557篇 |
国内免费 | 1686篇 |
出版年
2024年 | 49篇 |
2023年 | 210篇 |
2022年 | 513篇 |
2021年 | 834篇 |
2020年 | 618篇 |
2019年 | 773篇 |
2018年 | 875篇 |
2017年 | 734篇 |
2016年 | 1057篇 |
2015年 | 1612篇 |
2014年 | 1857篇 |
2013年 | 2070篇 |
2012年 | 2471篇 |
2011年 | 2257篇 |
2010年 | 1519篇 |
2009年 | 1301篇 |
2008年 | 1722篇 |
2007年 | 1581篇 |
2006年 | 1362篇 |
2005年 | 1313篇 |
2004年 | 1211篇 |
2003年 | 1054篇 |
2002年 | 984篇 |
2001年 | 627篇 |
2000年 | 487篇 |
1999年 | 408篇 |
1998年 | 276篇 |
1997年 | 218篇 |
1996年 | 184篇 |
1995年 | 165篇 |
1994年 | 121篇 |
1993年 | 105篇 |
1992年 | 176篇 |
1991年 | 140篇 |
1990年 | 135篇 |
1989年 | 135篇 |
1988年 | 127篇 |
1987年 | 122篇 |
1986年 | 93篇 |
1985年 | 105篇 |
1984年 | 79篇 |
1983年 | 68篇 |
1982年 | 63篇 |
1981年 | 49篇 |
1980年 | 49篇 |
1979年 | 76篇 |
1978年 | 67篇 |
1977年 | 53篇 |
1976年 | 63篇 |
1974年 | 51篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
S. H. Habib S.-E. Ooi Ond?ej Novák Danu?e Tarkowská Jakub Rol?ík Karel Dole?al S. S. R. Syed-Alwee C.-L. Ho P. Namasivayam 《Plant Growth Regulation》2012,68(2):313-317
Comparative mineral and hormonal analyses were made on tissue culture derived truncated leaf syndrome and wild type oil palm seedlings. Mineral analysis confirmed that Boron, Zinc and chlorophyll levels were significantly lower in truncated leaf syndrome leaves than those of wild type. Hormonal analysis also revealed various cytokinin derivatives such as trans-zeatin, trans-zeatin riboside, trans-zeatin O-glucoside and trans-zeatin riboside 5??mono phosphate were significantly higher in truncated leaf syndrome leaves compared to wild type leaves. Brassinolide level was also significantly higher in truncated leaf syndrome leaves than those of the wild type. These observations suggest that the truncated leaf syndrome abnormality could be associated to high cytokinin and brassinosteroid production which affects the uptake of Boron and Zinc. 相似文献
22.
23.
S. C. Ng A. H. Sathananthan P. C. Wong S. S. Ratnam J. Ho H. Mok M. N. Lee 《Molecular reproduction and development》1988,19(3):253-263
Previous studies by a French group (Fertil Steril 44:645–651, 1985) have shown that two-to eight-cell human embryos can survive slow freeze-thawing with propanediol in a biological freezer. These embryos were assessed for morphological appearance by phase-contrast microscopy. We assessed the structure of 25 frozen-thawed one- to 12-cell embryos, obtained from our in vitro fertilization (IVF) and GIFT programmes, by phase-contrast and electron microscopy, using the same method of cryopreservation. One-fourth of the embryos examined had all cells intact, and more than one-half the embryos had over 50% of their cells well preserved. Some of these embryos had unequal blastomeres and cytoplasmic fragments. Ultrastructural assessment revealed good preservation of fine structure in the intact blastomeres of all embryos and maintenance of cell-to-cell contacts. Most cytoplasmic organelles, cell membranes, and nuclei were well preserved compared to nonfrozen controls. The cells that were cryoinjured showed varying degrees of disorganization of the cell membrane, cytosol, and cellular membranes, including swelling and disruption of the nuclear envelope. Disruption of the zona was somewhat rare. Small cytoplasmic fragments were less prone to cryoinjury than blastomeres. The use of propanediol for embryo cryopreservation seems to be feasible; frozen embryos with more than 50% cells intact have produced 10 pregnancies after embryo transfer (Fertil Steril 46:268–272, 1986). Replacement of 17 frozen embryos in seven patients has resulted in a twin pregnancy in Singapore. However, the effects of freezing on the mitotic spindles of embryonic cells need to be investigated further. 相似文献
24.
25.
Mengmeng Zhuang Yuequ Deng Wenwen Zhang Bo Zhu Hao Yan Jiaqi Lou Pan Zhang Qingwei Cui Hao Tang Han Sun Yong Sun 《Cell death & disease》2021,12(6)
Intestinal mucosal injuries are directly or indirectly related to many common acute and chronic diseases. Long non-coding RNAs (lncRNAs) are expressed in many diseases, including intestinal mucosal injury. However, the relationship between lncRNAs and intestinal mucosal injury has not been determined. Here, we investigated the functions and mechanisms of action of lncRNA Bmp1 on damaged intestinal mucosa. We found that Bmp1 was increased in damaged intestinal mucosal tissue and Bmp1 overexpression was able to alleviate intestinal mucosal injury. Bmp1 overexpression was found to influence cell proliferation, colony formation, and migration in IEC-6 or HIEC-6 cells. Moreover, miR-128-3p was downregulated after Bmp1 overexpression, and upregulation of miR-128-3p reversed the effects of Bmp1 overexpression in IEC-6 cells. Phf6 was observed to be a target of miR-128-3p. Furthermore, PHF6 overexpression affected IEC-6 cells by activating PI3K/AKT signaling which was mediated by the miR-128-3p/PHF6 axis. In conclusion, Bmp1 was found to promote the expression of PHF6 through the sponge miR-128-3p, activating the PI3K/AKT signaling pathway to promote cell migration and proliferation.Subject terms: Cell growth, Cell migration 相似文献
26.
27.
N Shamala L W Lim F S Mathews W McIntire T P Singer D J Hopper 《Journal of molecular biology》1985,183(3):517-518
Single crystals of p-cresol methylhydroxylase, a flavocytochrome c from Pseudomonas putida, have been prepared. The crystals are orthorhombic, space group P212121 with unit cell parameters; a = 140.3 A, b = 130.6 A and c = 74.1 A. They contain a single non-symmetric dimer per asymmetric unit and diffract to at least 2.5 A resolution. 相似文献
28.
29.
30.