全文获取类型
收费全文 | 8979篇 |
免费 | 1024篇 |
国内免费 | 2篇 |
出版年
2021年 | 108篇 |
2019年 | 78篇 |
2018年 | 114篇 |
2017年 | 120篇 |
2016年 | 150篇 |
2015年 | 291篇 |
2014年 | 298篇 |
2013年 | 404篇 |
2012年 | 446篇 |
2011年 | 452篇 |
2010年 | 307篇 |
2009年 | 237篇 |
2008年 | 384篇 |
2007年 | 432篇 |
2006年 | 371篇 |
2005年 | 394篇 |
2004年 | 355篇 |
2003年 | 327篇 |
2002年 | 327篇 |
2001年 | 184篇 |
2000年 | 193篇 |
1999年 | 161篇 |
1998年 | 133篇 |
1997年 | 129篇 |
1996年 | 111篇 |
1995年 | 106篇 |
1994年 | 121篇 |
1993年 | 109篇 |
1992年 | 172篇 |
1991年 | 136篇 |
1990年 | 127篇 |
1989年 | 132篇 |
1988年 | 121篇 |
1987年 | 140篇 |
1986年 | 104篇 |
1985年 | 147篇 |
1984年 | 154篇 |
1983年 | 118篇 |
1982年 | 134篇 |
1981年 | 120篇 |
1980年 | 108篇 |
1979年 | 101篇 |
1978年 | 67篇 |
1977年 | 78篇 |
1976年 | 81篇 |
1975年 | 66篇 |
1974年 | 80篇 |
1973年 | 73篇 |
1972年 | 58篇 |
1971年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Russell L. Cecil 《BMJ (Clinical research ed.)》1932,2(3744):657-662
32.
33.
Caroline van Haaften-Day Peter Russell Susan Carr Lesley Wright 《In vitro cellular & developmental biology. Plant》1988,24(10):965-971
Summary A cell line derived from a human ovarian carcinosarcoma was established in tissue culture and in nude mice. Two sublines,
LDF and HDF, separated by discontinuous density centrifugation were also established from the parent line JoN. The cloning
efficiency of the JoN line was 21%. Morphologic features of adenocarcinoma cells characteristic of the parent JoN cells were
retained in the sublines and clones; all lines showed the same karyotype and DNA content (pseudodiploid and pseudotetraploid).
Keratin, as demonstrated immunohistochemically, was strongly expressed in the parent line JoN and the xenograft tumor, but
not at all in the LDF sublines and only moderately in the HDF sublines. Vimentin, however, was expressed in neither the parent
line JoN nor the xenograft tumor, but was present in both sublines. Transglutaminase and plasminogen activator activity was
high in the parent line JoN. Neither, sublines nor clones showed the same high enzyme activity as the parent line. It is concluded
that this human tumor line JoN is comprised of epithelial cells, capable of multidirectional differentiation. 相似文献
34.
35.
36.
William Russell 《BMJ (Clinical research ed.)》1984,288(6416):580
37.
38.
William Russell 《BMJ (Clinical research ed.)》1889,1(1463):70-71
39.
40.
Often we must balance being prepared to act quickly with being prepared to suddenly stop. The stop signal task (SST) is widely used to study inhibitory control, and provides a measure of the speed of the stop process that is robust to changes in subjects’ response strategy. Previous studies have shown that preparation affects inhibition. We used fMRI to separate activity that occurs after a brief (500 ms) warning stimulus (warning-phase) from activity that occurs during responses that follow (response-phase). Both of these phases could contribute to the preparedness to stop because they both precede stop signals. Warning stimuli activated posterior networks that signal the need for top-down control, whereas response phases engaged prefrontal and subcortical networks that implement top-down control. Regression analyses revealed that both of these phases affect inhibitory control in different ways. Warning-phase activity in the cerebellum and posterior cingulate predicted stop latency and accuracy, respectively. By contrast, response-phase activity in fronto-temporal areas and left striatum predicted go speed and stop accuracy, in pre-supplementary motor area affected stop accuracy, and in right striatum predicted stop latency and accuracy. The ability to separate hidden contributions to inhibitory control during warning-phases from those during response-phases can aid in the study of models of preparation and inhibitory control, and of disorders marked by poor top-down control. 相似文献