全文获取类型
收费全文 | 64897篇 |
免费 | 4908篇 |
国内免费 | 1404篇 |
专业分类
71209篇 |
出版年
2024年 | 99篇 |
2023年 | 392篇 |
2022年 | 1080篇 |
2021年 | 1667篇 |
2020年 | 1137篇 |
2019年 | 1371篇 |
2018年 | 1726篇 |
2017年 | 1426篇 |
2016年 | 2222篇 |
2015年 | 3420篇 |
2014年 | 3966篇 |
2013年 | 4362篇 |
2012年 | 5541篇 |
2011年 | 5302篇 |
2010年 | 3266篇 |
2009年 | 3050篇 |
2008年 | 4001篇 |
2007年 | 3791篇 |
2006年 | 3332篇 |
2005年 | 3026篇 |
2004年 | 2813篇 |
2003年 | 2395篇 |
2002年 | 2057篇 |
2001年 | 1638篇 |
2000年 | 1493篇 |
1999年 | 1218篇 |
1998年 | 573篇 |
1997年 | 481篇 |
1996年 | 389篇 |
1995年 | 323篇 |
1994年 | 315篇 |
1993年 | 234篇 |
1992年 | 414篇 |
1991年 | 365篇 |
1990年 | 344篇 |
1989年 | 286篇 |
1988年 | 216篇 |
1987年 | 208篇 |
1986年 | 158篇 |
1985年 | 132篇 |
1984年 | 110篇 |
1983年 | 97篇 |
1982年 | 73篇 |
1981年 | 59篇 |
1980年 | 55篇 |
1979年 | 71篇 |
1978年 | 53篇 |
1977年 | 50篇 |
1976年 | 44篇 |
1974年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
143.
Tae-Joon Park Ji-Sun Kim Sung-Sub Choi Yongae Kim 《Biotechnology and Bioprocess Engineering》2011,16(3):477-481
The amyloid precursor protein (APP) is an integral transmembrane protein which has been suggested to play a central role in the pathogenesis of Alzheimer’s disease. Despite the enormous amount of research conducted on amyloid protein, the precise mechanism of its toxic effect is not yet fully understood. To better understand the mechanism and function of amyloid protein, it is critical to elucidate the three-dimensional structure of the single transmembrane spanning region of human APP (hAPP-TM). Unfortunately, it is difficult to prepare the peptide sample because hAPP-TM is a membrane-bound protein that transverses the lipid bilayer of the cell membrane. Generally, the preparation of a transmembrane peptide is very difficult and time-consuming. In fact, high yield production of transmembrane peptides has been limited by experimental difficulties related to insufficient yields and the low solubility of such peptides. In this study, we describe experimental processes developed to optimize the expression, purification, and NMR measurement conditions for hAPP-TM transmembrane peptide. 相似文献
144.
Myung-Pyo Jung Hea-Son Bang Myung-Hyun Kim Kee-Kyung Kang Deog-Bae Lee 《Journal of Asia》2011,14(3):289-292
This study was conducted to monitor the abundance and distribution of the ussur brown katydid, Paratlanticus ussuriensis in South Korea, and to gather basic information about potential outbreak areas of this species. P. ussuriensis samples were collected from April to July in 2009 and 2010 using the transect method at the city or gun level. P. ussuriensis were identified in 86 cities or guns, and eight guns were determined to be potential risk areas of P. ussuriensis outbreaks. The current distribution of P. ussuriensis is well matched with the distribution of broadleaf trees. Their distribution and population density are expected to increase due to the expanding distribution of Quercus spp., the major food source of P. ussuriensis. 相似文献
145.
The genus Cryptaphis Hille Ris Lambers 1947 is described for the first time in Korea with new records of two species, Cryptaphis geranicola (Shinji 1935) and Cryptaphis menthae Takahashi 1961. Cryptaphis geranicola was collected from Geranium thunbergii (Lamiaceae) and C. menthae was collected from Isodon inflexus (Lamiaceae). Important characteristics are re-described, illustrated, and measured in apterous and alate viviparous females. 相似文献
146.
147.
Naturally occurring TAP-dependent specific T-cell tolerance for a variant of an immunodominant retroviral cytotoxic T-lymphocyte epitope 下载免费PDF全文
Upon immunization and restimulation with tumors induced by the endogenous AKR/Gross murine leukemia virus (MuLV), C57BL/6 mice generate vigorous H-2K(b)-restricted cytotoxic T-lymphocyte (CTL) responses to a determinant (KSPWFTTL) derived from the p15E transmembrane portion of the viral envelope glycoprotein. By contrast, the highly homologous determinant RSPWFTTL, expressed by tumor cells induced by Friend/Moloney/Rauscher (FMR) MuLV, is not immunogenic, even when presented to the immune system as vaccinia virus-encoded cytosolic or endoplasmic reticulum (ER)-targeted minigene products. Such minigene products are usually highly immunogenic since they bypass the need for cells to liberate the peptide or transport the peptide into the ER by the transporter associated with antigen processing (TAP). Using KSPWFTTL-specific CTLs that cross-react with RSPWFTTL, we previously demonstrated that presentation of RSPWFTTL from its natural viral gene product is TAP dependent. Here, we show first that C57BL/6 mice express mRNA encoding RSPWFTTL but not KSPWFTTL and second that the ER-targeted RSPWFTTL minigene product is highly immunogenic in C57BL/6 mice with a targeted deletion in TAP1. These findings provide the initial demonstration of TAP-dependent tolerance induction to a specific self peptide and demonstrate that this contributes to the differential recognition of RSPWFTTL and KSPWFTTL by C57BL/6 mice. 相似文献
148.
Aromatherapy is an anecdotal method for modifying sleep and mood. However, whether olfactory exposure to essential oils affects night‐time objective sleep remains untested. Previous studies also demonstrate superior olfactory abilities in women. Therefore, this study investigated the effects of an olfactory stimulus on subsequent sleep and assessed gender differences in such effects. Thirty‐one young healthy sleepers (16 men and 15 women, aged 18 to 30 yr, mean±SD, 20.5±2.4 yr) completed 3 consecutive overnight sessions in a sleep laboratory: one adaptation, one stimulus, and one control night (the latter 2 nights in counterbalanced order). Subjects received an intermittent presentation (first 2 min of each 10 min interval) of an olfactory (lavender oil) or a control (distilled water) stimulus between 23:10 and 23:40 h. Standard polysomnographic sleep and self‐rated sleepiness and mood data were collected. Lavender increased the percentage of deep or slow‐wave sleep (SWS) in men and women. All subjects reported higher vigor the morning after lavender exposure, corroborating the restorative SWS increase. Lavender also increased stage 2 (light) sleep, and decreased rapid‐eye movement (REM) sleep and the amount of time to reach wake after first falling asleep (wake after sleep onset latency) in women, with opposite effects in men. Thus, lavender serves as a mild sedative and has practical applications as a novel, nonphotic method for promoting deep sleep in young men and women and for producing gender‐dependent sleep effects. 相似文献
149.
150.