全文获取类型
收费全文 | 2508篇 |
免费 | 244篇 |
出版年
2021年 | 29篇 |
2019年 | 22篇 |
2018年 | 31篇 |
2017年 | 36篇 |
2016年 | 38篇 |
2015年 | 66篇 |
2014年 | 83篇 |
2013年 | 93篇 |
2012年 | 94篇 |
2011年 | 112篇 |
2010年 | 61篇 |
2009年 | 71篇 |
2008年 | 99篇 |
2007年 | 83篇 |
2006年 | 70篇 |
2005年 | 86篇 |
2004年 | 80篇 |
2003年 | 85篇 |
2002年 | 77篇 |
2001年 | 88篇 |
2000年 | 84篇 |
1999年 | 48篇 |
1998年 | 22篇 |
1997年 | 26篇 |
1996年 | 27篇 |
1995年 | 34篇 |
1992年 | 48篇 |
1991年 | 47篇 |
1990年 | 51篇 |
1989年 | 53篇 |
1988年 | 47篇 |
1987年 | 43篇 |
1986年 | 28篇 |
1985年 | 41篇 |
1984年 | 36篇 |
1983年 | 32篇 |
1982年 | 22篇 |
1981年 | 27篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1978年 | 24篇 |
1977年 | 30篇 |
1975年 | 28篇 |
1974年 | 35篇 |
1973年 | 34篇 |
1972年 | 25篇 |
1971年 | 35篇 |
1970年 | 32篇 |
1969年 | 28篇 |
1968年 | 21篇 |
排序方式: 共有2752条查询结果,搜索用时 15 毫秒
1.
2.
Barry Barnes 《New genetics and society》2013,32(3):292-302
The concern of this paper is with how the accounts of human beings and their behaviour now emerging from genetics, genomics and the new human biotechnology should be related to traditional accounts in which we identify ourselves as responsible agents, capable of choice, who normally act freely and voluntarily. The paper addresses these apparently competing accounts in terms of their functions and modes of use, and thereby arrives at a general solution to this current version of the ancient problem of free will and determinism. The causal scientific discourse of genetics and the everyday discourse of responsibility and choice do different things for us, it suggests, and should not be regarded as articulating conflicting theories. Whilst the former is oriented to the task of naturalistic explanation, the latter is predominantly, if not entirely, a medium of communication through which we affect each other and thereby mutually regulate our conduct. If this is indeed the case, then interesting implications follow concerning the proper relationship of the two kinds of account, which need no longer be regarded as incompatible with each other. And insights emerge into both the limitations and the profound importance of the contribution that genetics and genomics seem destined to make to the understanding of human behaviour. 相似文献
3.
4.
How reliable are dung counts for estimating elephant numbers? 总被引:4,自引:0,他引:4
R. F. W. Barnes 《African Journal of Ecology》2001,39(1):1-9
Dung counts are the most commonly used techniques for estimating elephant numbers in forests, yet there is considerable scepticism concerning their accuracy. Published accounts of dung counts show that they give estimates similar to those from other methods for vertebrates ranging in size from lizards to elephants. For ungulates, macropods and elephants there are strong correlations between estimates from dung counts and other methods. Thus, dung counts are as accurate or inaccurate as other methods for estimating vertebrate numbers, including elephants. Dung counts for elephants give estimates that are as precise as, and sometimes more precise than, those from aerial surveys of elephants. This is because the variance in dung density is usually low and results in a lower than expected variance for the final elephant estimate when combined with the variances of defecation and decay rates. Dung counts may be more appropriate than aerial surveys for monitoring small or declining elephant populations. 相似文献
5.
One hundred and forty five women who had undergone hemiarthroplasty for a subcapital fracture of the femoral neck but who were otherwise fit were studied to determine whether undue delay between injury and operation influenced their social circumstances three months after surgery. The median delay for those patients who showed good rehabilitation at three months was 29 hours, but for those who showed poor rehabilitation it was 57 hours. This difference was significant. It is suggested that a subcapital fracture in an otherwise fit elderly patient should therefore be regarded as a surgical emergency. 相似文献
6.
7.
8.
9.
The detection of 5-lipoxygenase and cyclo-oxygenase products in sputum of patients with chronic bronchitis and bronchiectasis 总被引:1,自引:0,他引:1
Leukotrienes (LTs) and prostanoids (Ps) were detected in sputum of patients with chronic bronchitis and/or bronchiectasis (CB/B) using selective superfusion bioassay and radioimmunoassay (RIA) techniques. Analysis of sputum extracts showed a 4-fold increase in the level of LTB4 compared to the cysteinyl-containing LTs (LTC4/LTD4). The measurement of cyclo-oxygenase products (COPs) indicated relatively greater amounts of the vasodilator prostaglandin E2 (PGE2) and prostacyclin (PGI2) compared to the vasoconstrictor prostaglandin F2 alpha (PGF2 alpha) and thromboxane A2 (TxA2) agents (70:30% of total COPs respectively). The presence of eicosanoids (LTs and Ps) in sputum of patients with CB/B suggest that these biologically active substances may act as mediators of bronchoconstriction and inflammation in these diseases. 相似文献
10.
Thomas M. Becker Jack D. Poland Thomas J. Quan Mark E. White Jonathan M. Mann Allan M. Barnes 《The Western journal of medicine》1987,147(5):554-557
Meningitis caused by Yersinia pestis developed in 6 (6%) of a total of 105 patients with plague reported to the Centers for Disease Control from 1970 to 1979. Five of the six cases occurred in children aged 10 to 15 years. All six patients received antibiotic therapy before meningitis developed, which appeared between the 9th and 14th days after the onset of acute illness in five of the six patients. There were no neurologic sequelae. The antigenic and biochemical profiles of the Y pestis strains isolated from cerebrospinal fluid in the meningitis cases did not differ from those of the Y pestis strains obtained from blood and bubo aspirates in the other 99 patients, and neither did in vitro studies suggest antibiotic resistance. While plague meningitis is an uncommon complication of acute plague infection, physicians in the western United States should be aware that it may develop as much as 14 days after antibiotic therapy for the acute plague infection has been initiated. 相似文献