全文获取类型
收费全文 | 1141856篇 |
免费 | 124677篇 |
国内免费 | 488篇 |
专业分类
1267021篇 |
出版年
2018年 | 10286篇 |
2016年 | 13504篇 |
2015年 | 17787篇 |
2014年 | 21366篇 |
2013年 | 30513篇 |
2012年 | 34244篇 |
2011年 | 34892篇 |
2010年 | 23808篇 |
2009年 | 21705篇 |
2008年 | 30992篇 |
2007年 | 32554篇 |
2006年 | 30510篇 |
2005年 | 29442篇 |
2004年 | 29252篇 |
2003年 | 28166篇 |
2002年 | 27757篇 |
2001年 | 48901篇 |
2000年 | 49436篇 |
1999年 | 39273篇 |
1998年 | 13769篇 |
1997年 | 14164篇 |
1996年 | 13471篇 |
1995年 | 12906篇 |
1994年 | 12816篇 |
1993年 | 12463篇 |
1992年 | 33612篇 |
1991年 | 33266篇 |
1990年 | 32526篇 |
1989年 | 31598篇 |
1988年 | 29746篇 |
1987年 | 28159篇 |
1986年 | 26183篇 |
1985年 | 26605篇 |
1984年 | 21878篇 |
1983年 | 19201篇 |
1982年 | 14653篇 |
1981年 | 13200篇 |
1980年 | 12523篇 |
1979年 | 21665篇 |
1978年 | 16754篇 |
1977年 | 15452篇 |
1976年 | 14585篇 |
1975年 | 16338篇 |
1974年 | 17506篇 |
1973年 | 17308篇 |
1972年 | 16015篇 |
1971年 | 14361篇 |
1970年 | 12584篇 |
1969年 | 12060篇 |
1968年 | 10999篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
Although phorbol 12-myristate 13-acetate (PMA) inhibits apoptosis and promotes the growth of some types of cells, it induces apoptosis in other cells. We evaluated the apoptotic effects of PMA on murine fibroblasts (L-929) that had been exposed to ultraviolet-B (UV-B) radiation at 312 nm, which promotes tumor cell growth. Exposure to PMA alone did not induce Fas, Fas-L, or apoptosis. Cells exposed to mild UV-B irradiation (80 J/m(2)) alone exhibited a slight expression of Fas and Fas-L 36 to 48 h after the exposure, and exhibited apoptosis as evidenced by DNA fragmentation 72 h after exposure. The addition of PMA (0.8 x 10(-5) to 3.2 x 10(-5) M) to the medium 24 h after the UV-B exposure markedly and dose-dependently enhanced these cell responses. Confluent untreated cells, cells cocultured with PMA, and cells cocultured with PMA for 24 h after the UV-B exposure consistently expressed mRNAs for wild-type p53, bcl-2, and ICE. Expression of c-myc mRNA was initially observed, but became undetectable in the cells cocultured for 24 h with a high concentration of PMA (3.2 x 10(-5) M) following UV-B exposure. Such cells subsequently exhibited the maximal apoptotic response. We conclude that mild exposure to UV-B altered murine fibroblast cells in such a way as to facilitate their death by apoptosis upon addition of PMA. 相似文献
83.
84.
M R Chandler 《Perspectives in biology and medicine》1991,35(1):105-115
Over the past 10 years the AIDS crisis has produced a large volume of writing. Much of this is documentary. Dozens of studies of AIDS from various clinical and political perspectives have been complemented by just as many published diaries, autobiographies, novels, plays, and poems. A few of these works have risen to the surface not only as extraordinarily valuable testimonies to the changes AIDS has wrought in individual and collective life but also as first-rate literary works, worth reading because beyond their immediate purposes they articulate with extraordinary lucidity and compassion some deep truths about the human--and the modern--condition. Paul Monette's Borrowed Time is among the most distinctive of those. It speaks not only for the community of people with AIDS and those who support them but for a generation. 相似文献
85.
Argon laser surgery is an effective treatment for ectasias and congenital port-wine stains; however, its use in children under the age of 13 is controversial. This paper reviews 202 children under the age of 13 who underwent argon laser treatments for congenital port-wine stains, spider angiomas, epidermal nevi, and lentigines. The clinical characteristics of port-wine stains in 170 children are discussed. Good to excellent results (moderate to complete clearing) in port-wine stains were obtained in 60 percent of patients and seemed to correlate best with lack of blanchability on pressure. Hypertrophic scarring was seen in only 7 children, all of whom had undressed wounds; no significant scarring has been seen in any subsequent child who had maintained a dressed wound postoperatively. 相似文献
86.
87.
88.
89.
90.