全文获取类型
收费全文 | 924篇 |
免费 | 6篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 29篇 |
丛书文集 | 1篇 |
理论与方法论 | 9篇 |
现状及发展 | 519篇 |
研究方法 | 98篇 |
综合类 | 263篇 |
自然研究 | 13篇 |
出版年
2020年 | 6篇 |
2018年 | 7篇 |
2017年 | 11篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 20篇 |
2012年 | 50篇 |
2011年 | 53篇 |
2010年 | 27篇 |
2009年 | 5篇 |
2008年 | 46篇 |
2007年 | 30篇 |
2006年 | 37篇 |
2005年 | 34篇 |
2004年 | 33篇 |
2003年 | 29篇 |
2002年 | 22篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 17篇 |
1979年 | 23篇 |
1978年 | 23篇 |
1977年 | 20篇 |
1976年 | 15篇 |
1975年 | 12篇 |
1974年 | 14篇 |
1973年 | 21篇 |
1972年 | 19篇 |
1971年 | 23篇 |
1970年 | 31篇 |
1969年 | 23篇 |
1968年 | 18篇 |
1967年 | 15篇 |
1966年 | 20篇 |
1965年 | 8篇 |
1954年 | 4篇 |
排序方式: 共有932条查询结果,搜索用时 15 毫秒
51.
A Dautigny I Bernier J Jollès J Colombani P Jollès 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,285(16):1535-1536
Two serologically active urinary glycoproteins (HLA-A 9 and HLA-B 12) were isolated from urine provided by a patient suffering from tubular proteinuria. Their N-terminal sequences were automatically determined. The latter were identical with the sequence of another urinary glycoprotein (protein HC). The relationship between protein HC and the serological activity is discussed. 相似文献
52.
Summary In the normal and hypothyroid 6-day-old rat, the specific radioactivity (RSA) and the relative RSA (ratio of the RSA to the [3H] leucine concentration of the acido soluble phase) of the cerebral and cerebellar proteins, change during the day synchronally. They show a maximum at 15.00 h and a minimum at 03.00 h. At all stages studied, these values are significantly lower in the hypothyroid animals than in normal ones. 相似文献
53.
54.
Jacoueline Chauvet Marie-Thérèse Chauvet R. Acher 《Cellular and molecular life sciences : CMLS》1972,28(12):1493-1495
Résumé Les propriétés pharmacologiques de la Ser4-Arg8-ocytocine (Ser4-vasotocine) synthétique ont été étudiées. La substitution en position 4 de la glutamine par la sérine diminue considérablement l'activité pressique de la vasotocine, ce qui montre l'importance de cette position dans les interactions entre les hormones neurohypophysaires et le récepteur vasopressique.
The authors are indebted to Dr.Albert Jöhl (Ciba-Geigy Laboratories) for a sample of synthetic Ser4-Arg8-oxytocin. They thank Mrs.Christine Gaullier for ther skilled technical assistance. 相似文献
The authors are indebted to Dr.Albert Jöhl (Ciba-Geigy Laboratories) for a sample of synthetic Ser4-Arg8-oxytocin. They thank Mrs.Christine Gaullier for ther skilled technical assistance. 相似文献
55.
A. Léonard A. Declève J. R. Maisin 《Cellular and molecular life sciences : CMLS》1971,27(10):1212-1214
Résumé L'utilisation d'une race de souris (AKR/T1Ald) ne possédant que 38 chromosomes a permis de montrer que les cellules de moelle que l'on injecte à un individu irradié repeuplent directement la moelle, le thymus et la rate du receveur. Si le donneur est irradié, la pénétration des cellules n'est importante que dans la rate du receveur.
Acknowledgements. This work was supported by grants from the Fonds de la Recherche scientifique fondamentale collective. The helpful assistance of Mr.G. Linden andG. Mattelin is gratefully acknowledged. 相似文献
Acknowledgements. This work was supported by grants from the Fonds de la Recherche scientifique fondamentale collective. The helpful assistance of Mr.G. Linden andG. Mattelin is gratefully acknowledged. 相似文献
56.
57.
Many receptors and allosteric proteins function through binding of a molecule to induce a conformational change, which then influences a remote active site. In synthetic systems, comparable intramolecular information transfer can be effected by using the shape of one part of a molecule to control the stereoselectivity of reactions occurring some distance away. However, the need for direct communication with the reaction site usually limits such remote stereocontrol to distances of not more than about five bond lengths. Cyclic structures overcome this problem by allowing the controlling centre and the reaction site to approach each other, but the information transfer spans only short absolute distances. Truly remote stereocontrol can, however, be achieved with rigid compounds containing amide groups: the conformation of the amides can be controlled by stereogenic centres and responds to that of neighbouring amide groups and in turn influences stereoselective reactions. This strategy has allowed remote stereocontrol spanning 8 (ref. 11) or 9 (ref. 12) bonds. Here we demonstrate stereocontrol over a reaction taking place more than 20 bond lengths from the controlling centre, corresponding to a linear distance of over 2.5 nm. This transmission of information, achieved by conformational changes relayed through the molecule, provides a chemical model of allostery and might serve as a molecular mechanism for communicating and processing information. 相似文献
58.
Evidence for cultivar adoption and emerging complexity during the mid-Holocene in the La Plata basin
Iriarte J Holst I Marozzi O Listopad C Alonso E Rinderknecht A Montaña J 《Nature》2004,432(7017):614-617
Multidisciplinary investigations at the Los Ajos archaeological mound complex in the wetlands of southeastern Uruguay challenge the traditional view that the La Plata basin was inhabited by simple groups of hunters and gatherers for much of the pre-Hispanic era. Here we report new archaeological, palaeoecological and botanical data indicating that during an increasingly drier mid-Holocene, at around 4,190 radiocarbon (14C) years before present (bp), Los Ajos became a permanent circular plaza village, and its inhabitants adopted the earliest cultivars known in southern South America. The architectural plan of Los Ajos during the following Ceramic Mound Period (around 3,000-500 14C yr bp) is similar to, but earlier than, settlement patterns demonstrated in Amazonia, revealing a new and independent architectural tradition for South America. 相似文献
59.
Strong evidence for a genetic basis of variation in physical performance has accumulated. Considering one of the basic tenets of evolutionary physiology--that physical performance and darwinian fitness are tightly linked--one may expect phenotypes with exceptional physiological capacities to be promoted by natural selection. Why then does physical performance remain considerably variable in human and other animal populations? Our analysis of locomotor performance in the common lizard (Lacerta vivipara) demonstrates that initial endurance (running time to exhaustion measured at birth) is indeed highly heritable, but natural selection in favour of this trait can be unexpectedly weak. A manipulation of dietary conditions unravels a proximate mechanism explaining this pattern. Fully fed individuals experience a marked reversal of performance within only one month after birth: juveniles with low endurance catch up, whereas individuals with high endurance lose their advantage. In contrast, dietary restriction allows highly endurant neonates to retain their locomotor superiority as they age. Thus, the expression of a genetic predisposition to high physical performance strongly depends on the environment experienced early in life. 相似文献
60.
The knockout mouse project 总被引:1,自引:0,他引:1
Austin CP Battey JF Bradley A Bucan M Capecchi M Collins FS Dove WF Duyk G Dymecki S Eppig JT Grieder FB Heintz N Hicks G Insel TR Joyner A Koller BH Lloyd KC Magnuson T Moore MW Nagy A Pollock JD Roses AD Sands AT Seed B Skarnes WC Snoddy J Soriano P Stewart DJ Stewart F Stillman B Varmus H Varticovski L Verma IM Vogt TF von Melchner H Witkowski J Woychik RP Wurst W Yancopoulos GD Young SG Zambrowicz B 《Nature genetics》2004,36(9):921-924
Mouse knockout technology provides a powerful means of elucidating gene function in vivo, and a publicly available genome-wide collection of mouse knockouts would be significantly enabling for biomedical discovery. To date, published knockouts exist for only about 10% of mouse genes. Furthermore, many of these are limited in utility because they have not been made or phenotyped in standardized ways, and many are not freely available to researchers. It is time to harness new technologies and efficiencies of production to mount a high-throughput international effort to produce and phenotype knockouts for all mouse genes, and place these resources into the public domain. 相似文献