全文获取类型
收费全文 | 62110篇 |
免费 | 6049篇 |
国内免费 | 22篇 |
出版年
2022年 | 416篇 |
2021年 | 883篇 |
2020年 | 579篇 |
2019年 | 742篇 |
2018年 | 921篇 |
2017年 | 860篇 |
2016年 | 1442篇 |
2015年 | 2528篇 |
2014年 | 2606篇 |
2013年 | 3399篇 |
2012年 | 3854篇 |
2011年 | 3488篇 |
2010年 | 2390篇 |
2009年 | 2181篇 |
2008年 | 2927篇 |
2007年 | 2883篇 |
2006年 | 2675篇 |
2005年 | 2587篇 |
2004年 | 2462篇 |
2003年 | 2174篇 |
2002年 | 2197篇 |
2001年 | 1601篇 |
2000年 | 1537篇 |
1999年 | 1427篇 |
1998年 | 882篇 |
1997年 | 787篇 |
1996年 | 789篇 |
1995年 | 752篇 |
1994年 | 716篇 |
1993年 | 749篇 |
1992年 | 1295篇 |
1991年 | 985篇 |
1990年 | 989篇 |
1989年 | 975篇 |
1988年 | 867篇 |
1987年 | 758篇 |
1986年 | 784篇 |
1985年 | 880篇 |
1984年 | 739篇 |
1983年 | 562篇 |
1982年 | 509篇 |
1981年 | 442篇 |
1980年 | 383篇 |
1979年 | 503篇 |
1978年 | 442篇 |
1977年 | 354篇 |
1976年 | 306篇 |
1975年 | 272篇 |
1974年 | 369篇 |
1973年 | 344篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.
A double helix B-type geometry based on high-resolution proton NMR of single-helical DNA fragments: d(TA)5 x d(TA)5. 总被引:2,自引:2,他引:0
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J R Mellema P N van Kampen C N Carlson H E Bosshard C Altona 《Nucleic acids research》1983,11(9):2893-2905
A single-helical B-type geometry is presented based on 1H NMR observations on d(TATA) and several other small single-helical DNA fragments. The structure is extended to one complete turn of double-helical DNA and its characteristics are compared with other known B-type structures. 相似文献
992.
Synthesis of short RNA fragments by the benzotriazolyl phosphotriester approach 总被引:6,自引:6,他引:0
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Analytical and experimental evidence will be presented to show that addition of a slight excess of 2-chlorophenyl-0,0-bis[1-benzotriazolyl]phosphate to a properly 2',5'-protected ribonucleoside gives an intermediate 3'-phosphotriester, which, after addition of a 2'-protected ribonucleoside, affords a dimer containing solely a 3'-5'-internucleotide linkage. The above phosphorylation procedure has been used in the synthesis of the pentamer UpApCpGpC. 相似文献
993.
Summary A simultaneous light and electron microscopic study of mouse gastric mucosa was made to determine whether the silver nitrate methenamine stain of Duk-Ho Lee could be used to stain gastric endocrine-like cells in plastic embedded tissue. Examination of consecutive thick and thin sections showed that this stain blackened the granules of the predominant type of endocrine-like cell present. Blackening of the granules with silver occured in tissue fixed in osmium tetroxide solution with or without dichromate salt or in tissue fixed in glutaraldehyde then treated with osmium. The intensity of staining was deepest in the osmium-dichromate fixed tissue, but the glutaraldehyde-osmium procedure gave less interference from diffuse silver impregnation and better preservation of detail for electron microscopy. 相似文献
994.
Henriette M. C. Put H. van Doren W. R. Warner J. Th. Kruiswijk 《Journal of applied microbiology》1972,35(1):7-27
S ummary : This review summarizes the work on the subject carried out mainly in the authors'laboratories but also in the associated laboratories of Metal Box Co. Ltd., London, and Plat Manufaktor, Malmö, Sweden. Special attention is paid to the mechanism of bacterial reinfection and how it is influenced by deviations in can construction or can handling procedures. Methods of preventing bacterial reinfection at the most critical points in the canning operation are considered and certain guiding principles are derived. 相似文献
995.
996.
997.
998.
From the Silberberg Quarry, type locality of the Silberberg Formation (Martini &Ritzkowski 1968), some planktonic foraminifera are described:Globigerina officinalis Subbotina, Globigerina ouachitaensisHowe &Wallace,G. praebulloides leroyi Blow &Banner, G.praebulloides occlusa Blow &Banner which taxa are here suggested to form intergrading morphotypes within the range of variation of a population dominated byG. officinalis. In addition,G. cf.danvillensis Howe &Wallace is found. The planktonic fauna, together with some elements in the benthonic fauna, suggests a possible correlation with the Danville Landing Member of the Jackson Formation, Louisiana, traditionally ascribed to the Upper Eocene. There is some similarity with European Uppermost Eocene — Lower Oligocene faunas described by various authors. The Silberberg Formation was suggested to be a Neostratotype for the Latdorfian Stage of the Lower Oligocene byMartini &Ritzkowski (1968). It is suggested that the Silberberg Formation may well be coeval with the Upper Priabonian as proposed byCita 1969. 相似文献
999.
1000.
Summary (RS)-Abscisic acid, a natural plant hormone, has been found to inhibit photosynthesis in both detached and attached primary wheat leaves. The action occurs rapidly and is accompanied by large increases in stomatal diffusive resistance.This research was supported by the Wheat Industry Research Council. 相似文献