全文获取类型
收费全文 | 92294篇 |
免费 | 5986篇 |
国内免费 | 983篇 |
出版年
2023年 | 773篇 |
2022年 | 1036篇 |
2021年 | 2008篇 |
2020年 | 1588篇 |
2019年 | 1810篇 |
2018年 | 3105篇 |
2017年 | 2736篇 |
2016年 | 3656篇 |
2015年 | 4896篇 |
2014年 | 5043篇 |
2013年 | 6444篇 |
2012年 | 7545篇 |
2011年 | 6830篇 |
2010年 | 4173篇 |
2009年 | 3269篇 |
2008年 | 4952篇 |
2007年 | 4579篇 |
2006年 | 4296篇 |
2005年 | 3638篇 |
2004年 | 3477篇 |
2003年 | 3085篇 |
2002年 | 2813篇 |
2001年 | 1846篇 |
2000年 | 1833篇 |
1999年 | 1419篇 |
1998年 | 685篇 |
1997年 | 513篇 |
1996年 | 557篇 |
1995年 | 522篇 |
1994年 | 411篇 |
1993年 | 370篇 |
1992年 | 754篇 |
1991年 | 648篇 |
1990年 | 580篇 |
1989年 | 539篇 |
1988年 | 532篇 |
1987年 | 494篇 |
1986年 | 440篇 |
1985年 | 480篇 |
1984年 | 421篇 |
1983年 | 308篇 |
1982年 | 267篇 |
1981年 | 207篇 |
1980年 | 216篇 |
1979年 | 273篇 |
1978年 | 253篇 |
1975年 | 247篇 |
1974年 | 261篇 |
1973年 | 255篇 |
1972年 | 218篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
82.
83.
Zhenzhen Zhang Changjiu He Yu Gao Lu Zhang Yukun Song Tianqi Zhu Kuanfeng Zhu Dongying Lv Jing Wang Xiuzhi Tian Teng Ma Pengyun Ji Wei Cui Guoshi Liu 《Aging cell》2021,20(2)
The fecundity reduction with aging is referred as the reproductive aging which comes earlier than that of chronological aging. Since humans have postponed their childbearing age, to prolong the reproductive age becomes urgent agenda for reproductive biologists. In the current study, we examined the potential associations of α‐ketoglutarate (α‐KG) and reproductive aging in mammals including mice, swine, and humans. There is a clear tendency of reduced α‐KG level with aging in the follicle fluids of human. To explore the mechanisms, mice were selected as the convenient animal model. It is observed that a long term of α‐KG administration preserves the ovarian function, the quality and quantity of oocytes as well as the telomere maintaining system in mice. α‐KG suppresses ATP synthase and alterations of the energy metabolism trigger the nutritional sensors to down‐regulate mTOR pathway. These events not only benefit the general aging process but also maintain ovarian function and delay the reproductive decline. Considering the safety of the α‐KG as a naturally occurring molecule in energy metabolism, its utility in reproduction of large mammals including humans deserves further investigation. 相似文献
84.
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
85.
86.
Drahomíra Kenov Lucie oltysov Michal Pravenec Marie-Pierre Moisan W. Theodore Kurtz Vladimír Ken 《Journal of Experimental Animal Science》2000,41(1-2)
The SHR-Lx congenic strain carrying a differential segment of chromosome 8 of BN and PD origin was recently shown to exhibit a significant decrease in blood pressure as compared to the SHR strain. There were two positional candidate genes for blood pressure control mapped to the differential segment: the rat kidney epithelial potassium channel gene (Kcnj1) and brain dopamine receptor 2 gene (Drd2). Bot these genes were separated into SHR.BN-RNO8 congenic substrains. In this communication, we are presenting the assignment of two further putative candidate genes, which might be involved in blood pressure control to the BN/PD differential segment of the SHR-Lx congenic strain. These are: the gene coding for smooth muscle cell specific protein 22 (Sm22) defined by the D8Mcw1 marker and neuronal nicotinic acetylcholine receptor gene cluster, defined by the D8Bord1 marker. Moreover, the glutamate receptor gene Grik4 which also maps to the differential segment of the SHR-Lx should be taken into account. The genetic separation of all these putative candidate genes of blood pressure control is being performed by recombinations and subsequent selection using (SHR×SHR-Lx) intercross population. 相似文献
87.
88.
Three cases of neonatal alloimmune thrombocytopenia and one patient with post-transfusion purpura could be diagnosed only by introducing the platelet immunofluorescence test. Thrombocytopenia was caused by anti-PlA1 platelet alloantibodies detected neither in the agglutination nor by the complement fixation test. 相似文献
89.
90.
Ohne Zusammenfassung 相似文献