全文获取类型
收费全文 | 29377篇 |
免费 | 84篇 |
国内免费 | 158篇 |
专业分类
系统科学 | 146篇 |
丛书文集 | 499篇 |
教育与普及 | 42篇 |
理论与方法论 | 104篇 |
现状及发展 | 13786篇 |
研究方法 | 1304篇 |
综合类 | 13338篇 |
自然研究 | 400篇 |
出版年
2013年 | 280篇 |
2012年 | 430篇 |
2011年 | 836篇 |
2010年 | 181篇 |
2008年 | 552篇 |
2007年 | 600篇 |
2006年 | 598篇 |
2005年 | 558篇 |
2004年 | 553篇 |
2003年 | 512篇 |
2002年 | 521篇 |
2001年 | 943篇 |
2000年 | 872篇 |
1999年 | 622篇 |
1992年 | 596篇 |
1991年 | 415篇 |
1990年 | 487篇 |
1989年 | 497篇 |
1988年 | 464篇 |
1987年 | 549篇 |
1986年 | 478篇 |
1985年 | 601篇 |
1984年 | 492篇 |
1983年 | 366篇 |
1982年 | 342篇 |
1981年 | 369篇 |
1980年 | 471篇 |
1979年 | 901篇 |
1978年 | 763篇 |
1977年 | 744篇 |
1976年 | 618篇 |
1975年 | 640篇 |
1974年 | 855篇 |
1973年 | 769篇 |
1972年 | 786篇 |
1971年 | 852篇 |
1970年 | 1082篇 |
1969年 | 824篇 |
1968年 | 826篇 |
1967年 | 808篇 |
1966年 | 692篇 |
1965年 | 477篇 |
1964年 | 158篇 |
1959年 | 254篇 |
1958年 | 444篇 |
1957年 | 297篇 |
1956年 | 265篇 |
1955年 | 256篇 |
1954年 | 245篇 |
1948年 | 166篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
E. Häfliger 《Cellular and molecular life sciences : CMLS》1948,4(6):223-225
Summary The action of DDT on honey-bees depends to a high extent on the temperature (see graph). At 36°C (breeding temperature) DDT has a far weaker insecticidal action than at 20°C (laboratory temperature). This shows that the insecticidal properties of DDT diminish with the raise of temperature.This resistance to DDT at higher temperature is most propitious for bee-keeping and also explains the fact why in agricultural practice there has been no corroborated case of poisoning of bees, though in laboratory tests DDT avered itself to be toxic to bees. 相似文献
103.
104.
105.
106.
107.
108.
Starch-binding domains in the post-genome era 总被引:1,自引:1,他引:0
Starch belongs to the most abundant biopolymers on Earth. As a source of energy, starch is degraded by a large number of various
amylolytic enzymes. However, only about 10% of them are capable of binding and degrading raw starch. These enzymes usually
possess a distinct sequence-structural module, the so-called starchbinding domain (SBD). In general, all carbohydrate-binding
modules (CBMs) have been classified into the CBM families. In this sequence-based classification the individual types of SBDs
have been placed into seven CBM families: CBM20, CBM21, CBM25, CBM26, CBM34, CBM41 and CBM45. The family CBM20, known also
as a classical C-terminal SBD of microbial amylases, is the most thoroughly studied. The three-dimensional structures have
already been determined by X-ray crystallography or nuclear magnetic resonance for SBDs from five CBM families (20, 25, 26,
34 and 41), and the structure of the CBM21 has been modelled. Despite differences among the amino acid sequences, the fold
of a distorted β-barrel seems to be conserved together with a similar way of substrate binding (mainly stacking interactions
between aromatic residues and glucose rings). SBDs have recently been discovered in many non-amylolytic proteins. These may,
for example, have regulatory functions in starch metabolism in plants or glycogen metabolism in mammals. SBDs have also found
practical uses.
Received 25 May 2006; received after revision 26 June 2006; accepted 3 August 2006 相似文献
109.
Maller JB Fagerness JA Reynolds RC Neale BM Daly MJ Seddon JM 《Nature genetics》2007,39(10):1200-1201
The association of variants in complement factors H and B with age-related macular degeneration has led to more intense genetic and functional analysis of the complement pathway. We identify a nonsynonymous coding change in complement factor 3 that is strongly associated with risk of age-related macular degeneration in a large case-control sample. 相似文献
110.
Gout AM;ADPKD Gene Variant Consortium Ravine D Harris PC Rossetti S Peters D Breuning M Henske EP Koizumi A Inoue S Shimizu Y Thongnoppakhun W Yenchitsomanus PT Deltas C Sandford R Torra R Turco AE Jeffery S Fontes M Somlo S Furu LM Smulders YM Mercier B Ferec C Burtey S Pei Y Kalaydjieva L Bogdanova N McCluskey M Geon LJ Wouters CH Reiterova J Stekrová J San Millan JL Aguiari G Del Senno L 《Nature genetics》2007,39(4):427-428