全文获取类型
收费全文 | 38177篇 |
免费 | 3057篇 |
国内免费 | 1767篇 |
专业分类
43001篇 |
出版年
2024年 | 76篇 |
2023年 | 287篇 |
2022年 | 730篇 |
2021年 | 1119篇 |
2020年 | 793篇 |
2019年 | 1036篇 |
2018年 | 1227篇 |
2017年 | 936篇 |
2016年 | 1403篇 |
2015年 | 2175篇 |
2014年 | 2530篇 |
2013年 | 2666篇 |
2012年 | 3445篇 |
2011年 | 3241篇 |
2010年 | 2090篇 |
2009年 | 1782篇 |
2008年 | 2424篇 |
2007年 | 2186篇 |
2006年 | 1870篇 |
2005年 | 1702篇 |
2004年 | 1566篇 |
2003年 | 1335篇 |
2002年 | 1314篇 |
2001年 | 860篇 |
2000年 | 839篇 |
1999年 | 639篇 |
1998年 | 312篇 |
1997年 | 244篇 |
1996年 | 197篇 |
1995年 | 149篇 |
1994年 | 146篇 |
1993年 | 109篇 |
1992年 | 205篇 |
1991年 | 167篇 |
1990年 | 123篇 |
1989年 | 129篇 |
1988年 | 90篇 |
1987年 | 84篇 |
1986年 | 86篇 |
1985年 | 68篇 |
1984年 | 59篇 |
1983年 | 46篇 |
1982年 | 32篇 |
1981年 | 28篇 |
1979年 | 30篇 |
1978年 | 32篇 |
1976年 | 38篇 |
1975年 | 38篇 |
1973年 | 34篇 |
1969年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Jae-Seong Lee Ryeo-Ok Kim Jae-Sung Rhee Jeonghoon Han Dae-Sik Hwang Beom-Soon Choi Chang Joo Lee Yong-Dal Yoon Jong-Sung Lim Young-Mi Lee Gyung Soo Park Atsushi Hagiwara Ik-Young Choi 《Hydrobiologia》2011,662(1):65-75
The monogonont rotifer, Brachionus ibericus (S type), is considered to be a promising model species for developmental biology, evolution, and environmental genomics. In an attempt to accelerate the molecular understanding of B. ibericus, we sequenced 680.5 Mb of genomic DNA using the genome sequencer GS-FLX-Titanium. We obtained 2,062,621 reads (average read length 329.9 bp) and 145,418 contigs (total contigs length 125.7 Mb) after excluding small reads (less than 200 bp) from the assembly, and finally obtained 10,133 unigenes (E value ?? 9.00E?04) after non-redundant (NR) BLAST search. In this article, we summarize the genomic DNA sequences of B. ibericus and discuss their potential use in the study of reproductive biology, endocrinology, environmental genomics, and ecotoxicological studies, and for providing insight into the genetic basis of mechanisms such as egg formation, antioxidant stress defense, and xenobiotic metabolism. 相似文献
113.
Allan M. Prior Xufen Yu Eun-Jung Park Tamara P. Kondratyuk Yan Lin John M. Pezzuto Dianqing Sun 《Bioorganic & medicinal chemistry letters》2017,27(24):5393-5399
In our ongoing effort of discovering anticancer and chemopreventive agents, a series of 2-arylindole derivatives were synthesized and evaluated toward aromatase and quinone reductase 1 (QR1). Biological evaluation revealed that several compounds (e.g., 2d, IC50?=?1.61?μM; 21, IC50?=?3.05?μM; and 27, IC50?=?3.34?μM) showed aromatase inhibitory activity with half maximal inhibitory concentration (IC50) values in the low micromolar concentrations. With regard to the QR1 induction activity, 11 exhibited the highest QR1 induction ratio (IR) with a low concentration to double activity (CD) value (IR?=?8.34, CD?=?2.75?μM), while 7 showed the most potent CD value of 1.12?μM. A dual acting compound 24 showed aromatase inhibition (IC50?=?9.00?μM) as well as QR1 induction (CD?=?5.76?μM) activities. Computational docking studies using CDOCKER (Discovery Studio 3.5) provided insight in regard to the potential binding modes of 2-arylindoles within the aromatase active site. Predominantly, the 2-arylindoles preferred binding with the 2-aryl group toward a small hydrophobic pocket within the active site. The C-5 electron withdrawing group on indole was predicted to have an important role and formed a hydrogen bond with Ser478 (OH). Alternatively, meta-pyridyl analogs may orient with the pyridyl 3′-nitrogen coordinating with the heme group. 相似文献
114.
115.
Grace X. Ma Steve Shive Yin Tan Wanzhen Gao Joanne Rhee Micah Park Jaesool Kim Jamil I. Toubbeh 《Cancer epidemiology》2009,33(5):381-386
Background: Despite evidence of a decline in both incidence and prevalence of colorectal cancer nationwide, it remains the second most commonly diagnosed cancer and the third highest cause of mortality among Asian Americans, including Korean Americans. This community-based and theoretically guided study evaluated a culturally appropriate intervention program that included a bilingual cancer educational program among Korean Americans including information on CRC risks, counseling to address psychosocial and access barriers, and patient navigation assistance. Methods: A two-group quasi-experimental design with baseline and post-intervention assessment and a 12-month follow-up on screening was used in the study. Korean Americans (N = 167) were enrolled from six Korean churches. The intervention group received culturally appropriate intervention program addressing accessibility and psychosocial barriers, and navigation assistance for screening. The control group received general health education that included cancer-related health issues and screening. Results: There was a significant difference (p < 0.05) between the post-intervention and control groups in awareness of CRC risk factors. There was also a significant improvement in the pre–post across HBM measures in the intervention group for perceived susceptibility (p < 0.05) and benefits and barriers to screening (p < 0.001). At baseline, 13% of participants in the intervention group and 10% in control group reported having had a CRC cancer screening test in the previous year. At the 12-month post-intervention follow-up, 77.4% of participants in the intervention group had obtained screening compared to 10.8% in the control group. Conclusion: While health disparities result from numerous factors, a culturally appropriate and church-based intervention can be highly effective in increasing knowledge of and access to, and in reducing barriers to CRC screening among underserved Koreans. 相似文献
116.
117.
118.
Piao S Kim S Kim JH Park JW Lee BL Ha NC 《The Journal of biological chemistry》2007,282(14):10783-10791
A family of serine proteases (SPs) mediates the proteolytic cascades of embryonic development and immune response in invertebrates. These proteases, called easter-type SPs, consist of clip and chymotrypsin-like SP domains. The SP domain of easter-type proteases differs from those of typical SPs in its primary structure. Herein, we report the first crystal structure of the SP domain of easter-type proteases, presented as that of prophenoloxidase activating factor (PPAF)-I in zymogen form. This structure reveals several important structural features including a bound calcium ion, an additional loop with a unique disulfide linkage, a canyon-like deep active site, and an exposed activation loop. We subsequently show the role of the bound calcium and the proteolytic susceptibility of the activation loop, which occurs in a clip domain-independent manner. Based on biochemical study in the presence of heparin, we suggest that PPAF-III, highly homologous to PPAF-I, contains a surface patch that is responsible for enhancing the catalytic activity through interaction with a nonsubstrate region of a target protein. These results provide insights into an activation mechanism of easter-type proteases in proteolytic cascades, in comparison with the well studied blood coagulation enzymes in mammals. 相似文献
119.
Duck‐Oung Jung Dae‐Sup Park Jae‐Kyoung Shim Sukchan Lee Jaeho Pyee Kyeong‐Yeoll Lee 《Entomological Research》2019,49(1):72-77
Mites are one of the serious pests of turfgrass. Our survey of turfgrass fields from 2013 to 2015 in Korea showed that the occurrence of leaf chlorotic symptom has gradually extended to at least 60% of the examined golf courses. We identified the zoysiae mite Aceria zoysiae in most damaged zoysiagrasses. Artificial infestation of A. zoysiae into zoysiagrasses in pots resulted in symptoms of chlorosis and marginal rolling of the leaves within 3 weeks. We firstly determined the nucleotide sequence of mitochondrial cytochrome c oxidase subunit I (COI) and internal transcribed spacer 2 (ITS2) of the nuclear ribosomal DNA region of A. zoysiae. The variations in COI and ITS2 between A. zoysiae and other species of the genus were 20.9%–43.0% and 7.5%–67.3%, respectively, suggesting significant genetic divergence within the genus. Our study provides valuable information for the rapid diagnosis and infestation monitoring of A. zoysiae in turfgrass fields. 相似文献
120.