全文获取类型
收费全文 | 1687篇 |
免费 | 135篇 |
国内免费 | 8篇 |
出版年
2020年 | 18篇 |
2019年 | 21篇 |
2018年 | 16篇 |
2017年 | 22篇 |
2016年 | 18篇 |
2015年 | 44篇 |
2014年 | 55篇 |
2013年 | 56篇 |
2012年 | 75篇 |
2011年 | 54篇 |
2010年 | 61篇 |
2009年 | 57篇 |
2008年 | 73篇 |
2007年 | 77篇 |
2006年 | 70篇 |
2005年 | 58篇 |
2004年 | 48篇 |
2003年 | 50篇 |
2002年 | 31篇 |
2001年 | 54篇 |
2000年 | 30篇 |
1999年 | 46篇 |
1998年 | 27篇 |
1997年 | 21篇 |
1996年 | 24篇 |
1995年 | 18篇 |
1994年 | 16篇 |
1992年 | 24篇 |
1991年 | 28篇 |
1990年 | 18篇 |
1989年 | 20篇 |
1988年 | 24篇 |
1987年 | 16篇 |
1986年 | 33篇 |
1985年 | 16篇 |
1980年 | 13篇 |
1979年 | 28篇 |
1978年 | 17篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1974年 | 14篇 |
1973年 | 14篇 |
1958年 | 24篇 |
1957年 | 26篇 |
1956年 | 27篇 |
1955年 | 26篇 |
1954年 | 22篇 |
1953年 | 15篇 |
1952年 | 14篇 |
排序方式: 共有1830条查询结果,搜索用时 203 毫秒
1.
2.
3.
4.
Martin Knapp 《BMJ (Clinical research ed.)》1984,289(6437):107-108
5.
The microbial degradation of morpholine 总被引:5,自引:1,他引:4
Morpholine can be completely degraded microbiologically, and two organisms have been isolated, each capable of growth in a simple mineral salts medium with morpholine as the sole source of carbon, nitrogen and energy. Excess nitrogen is liberated as ammonia. The enzymes responsible for the oxidation of morpholine are inducible and, in organism Mor G, will also oxidize piperidine, piperazine and pyrrolidine, which are not growth substrates. Ethanolamine is a likely intermediate, though the metabolic steps in morpholine degradation do not give rise solely to acetyl-CoA. After a period of acclimation, a laboratory scale activated sludge plant effectively removed morpholine over the long period it was operated; the sludge was also capable of nitrification. The possible effects of other chemicals in trade wastes containing morpholine on nitrification and morpholine oxidation are described. 相似文献
6.
Teresa Sadras Mickaël Martin Kohei Kume Mark E. Robinson Supraja Saravanakumar Gal Lenz Zhengshan Chen Joo Y. Song Tanya Siddiqi Laura Oksa Anne Marie Knapp Jevon Cutler Kadriye Nehir Cosgun Lars Klemm Veronika Ecker Janet Winchester Dana Ghergus Pauline Soulas-Sprauel Markus Müschen 《Molecular cell》2021,81(10):2094-2111.e9
7.
8.
Leslie A. Knapp 《Evolutionary anthropology》2005,14(1):28-37
The major histocompatibility complex (MHC) contains the most diverse genes known in vertebrates. These genes encode cell‐surface molecules that play a central role in controlling immunological activity and, as a consequence, in tissue rejection, autoimmunity, and immune responses to infectious diseases. In vertebrates, there are many different MHC genes, most with many alleles. This is true for all primates studied thus far. Multiple loci and alleles allow for an increased peptide‐binding repertoire; their variety has a profound impact on an organism's ability to battle constantly evolving pathogens. The argument that infectious disease is a driving force for MHC variability is supported by observations that most of the allelic variation centers on the amino acid residues that directly interact with foreign peptides. However, while MHC diversity could be maintained through heterozygote advantage, frequency‐dependent selection, or both, the direct evidence that natural selection enhances diversity is limited. Indeed, it is not wholly clear whether selection operates only with respect to disease resistance or if behavioral and biological mechanisms also contribute to the extreme variation that has been observed for many species. Furthermore, reproductive behavior and biology may also help to maintain genetic variability at MHC loci. 相似文献
9.
10.