全文获取类型
收费全文 | 1988篇 |
免费 | 151篇 |
国内免费 | 1篇 |
出版年
2023年 | 15篇 |
2022年 | 38篇 |
2021年 | 67篇 |
2020年 | 33篇 |
2019年 | 45篇 |
2018年 | 41篇 |
2017年 | 34篇 |
2016年 | 60篇 |
2015年 | 127篇 |
2014年 | 105篇 |
2013年 | 117篇 |
2012年 | 149篇 |
2011年 | 152篇 |
2010年 | 92篇 |
2009年 | 81篇 |
2008年 | 110篇 |
2007年 | 105篇 |
2006年 | 87篇 |
2005年 | 83篇 |
2004年 | 71篇 |
2003年 | 70篇 |
2002年 | 53篇 |
2001年 | 22篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 19篇 |
1996年 | 14篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 13篇 |
1992年 | 23篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 18篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1970年 | 4篇 |
1952年 | 4篇 |
排序方式: 共有2140条查询结果,搜索用时 31 毫秒
1.
2.
Elena C. Guzman Alfonso Jimenez-Sanchez Elisha Orr Robert H. Pritchard 《Molecular & general genetics : MGG》1988,212(2):203-206
Summary A temperature shift-up accompanied by a reduction in RNA polymerase activity in Escherichia coli causes an increased rate of initiation leading to a 1.7- to 2.2-fold increase in chromosome copy number. A temperature shift-up without a reduction in polymerase activity induces only a transient non-scheduled initiation of chromosome replication caused by heat shock with no detectable effect on chromosome copy number. 相似文献
3.
The gorgoniid Eugorgia is exclusively an eastern Pacific genus. It has a wide geographic and bathymetric range of distribution, found from California to Perú and extends down to 65 m deep. Two new species are herein described. The morphological characters were analyzed and illustrated by light and scanning electron microscopy. Eugorgia beebei
sp. n. can be distinguished by its white, ascending, sparse colony growth. Eugorgia mutabilis
sp. n. can be distinguished by its white colony that changes color after collection, and the conspicuous sharp-crested disc sclerites. From a morphological point of view the new species are related to the daniana-group, the rubens-group and the siedenburgae-group of Eugorgia; their affiliations, and the proposal of a new group are discussed. These new species increases the number of species in the genus to 15, and contribute to the knowledge of the eastern Pacific octocoral biodiversity. 相似文献
4.
5.
Heidi Weberru? Raphael Pirzer Robert Dalla Pozza Heinrich Netz Renate Oberhoffer 《PloS one》2016,11(3)
Carotid intima-media thickness (cIMT) is a surrogate marker of early atherosclerotic changes in children. cIMT-studies are hard to compare, due to variations in ultrasound protocols, especially regarding the common carotid artery (CCA) segment measured in relation to the bulb. This study’s purpose was therefore to compare two distinct CCA segments in children, to see if cIMT values differ substantially according to the site of measurement. cIMT was assessed after power calculation in 30 children (15 girls) aged 8–17, using B-Mode ultrasound (5–13 MHz) at two CCA locations. The first measurement was performed over a distance of 1 cm immediately after the bulb (A), the second 1cm proximal the bulb (B) over the same distance of 1cm length. Means of end-diastolic far wall cIMT were compared between measurement A and B. cIMT in 30 participants was 0.51±0.06 mm for measurement A and 0.51±0.05 mm for measurement B. Results did not differ significantly (p = .947) over a distance of 2 cm after the bulb. According to our results, studies measuring CCA IMT within the first 2 cm, either close to the bulb or further proximal, can be compared. This will improve interpretation of data and application of reference values. 相似文献
6.
7.
8.
9.
Raphael Chijioke Njoku 《Dialectical Anthropology》2007,31(1-3):45-64
It is difficult to completely understand the life history of an intellectual excluding an understanding of his family upbringing
and formative years. Family upbringing and childhood environment, often the less known part of a life history, play crucial
roles in shaping the ideas and values individuals espouse in their adult life. Notwithstanding, this paper is not concerned
with Don C. Ohadike’s childhood. It rather focuses on the professional career of our able historian – that is the part of
his life as revealed by his most outstanding published writings. Ohadike’s published works contain a wellspring of idioms
that tell much about his values, quality of mind, and his mission as an African historian. Ohadike was a humanist, an African
patriot, and a nationalist crusader. His entire philosophy centered on safeguarding his African identity in an emergent world
of cultural imperialism.
The funds for this research were provided by a NEH-funded fellowship at the Schomburg Center, New York in the Spring of 2007.
I owe a lot of gratitude to Professor John McLeod and Dean Blaine Hudson for granting me the extra incentives to pursue my
research in New York. While all errors and misinterpretations are mine, I wish to thank the editors and anonymous reviewers
for Journal of Dialectical Anthropology for their perspective comments and suggestions on earlier drafts of this paper. 相似文献
10.