全文获取类型
收费全文 | 13518篇 |
免费 | 32篇 |
国内免费 | 61篇 |
专业分类
系统科学 | 68篇 |
丛书文集 | 82篇 |
教育与普及 | 41篇 |
理论与方法论 | 90篇 |
现状及发展 | 5345篇 |
研究方法 | 801篇 |
综合类 | 6927篇 |
自然研究 | 257篇 |
出版年
2013年 | 123篇 |
2012年 | 321篇 |
2011年 | 582篇 |
2010年 | 145篇 |
2009年 | 72篇 |
2008年 | 305篇 |
2007年 | 397篇 |
2006年 | 343篇 |
2005年 | 378篇 |
2004年 | 351篇 |
2003年 | 333篇 |
2002年 | 352篇 |
2001年 | 386篇 |
2000年 | 371篇 |
1999年 | 274篇 |
1992年 | 239篇 |
1991年 | 183篇 |
1990年 | 209篇 |
1989年 | 194篇 |
1988年 | 204篇 |
1987年 | 208篇 |
1986年 | 161篇 |
1985年 | 251篇 |
1984年 | 171篇 |
1983年 | 149篇 |
1982年 | 170篇 |
1981年 | 135篇 |
1980年 | 172篇 |
1979年 | 385篇 |
1978年 | 295篇 |
1977年 | 293篇 |
1976年 | 251篇 |
1975年 | 287篇 |
1974年 | 311篇 |
1973年 | 310篇 |
1972年 | 344篇 |
1971年 | 345篇 |
1970年 | 429篇 |
1969年 | 363篇 |
1968年 | 383篇 |
1967年 | 352篇 |
1966年 | 320篇 |
1965年 | 203篇 |
1959年 | 107篇 |
1958年 | 204篇 |
1957年 | 137篇 |
1956年 | 122篇 |
1955年 | 105篇 |
1954年 | 81篇 |
1948年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
1.
从“十四五”保护与发展的生态关系角度,探讨了生态保护与绿色发展的十大生态关系,阐述了生态保护和绿色发展中的一系列有关生态关系的生态智慧及生态技术,并对长江、黄河等流域的生态保护和修复提出了相关建议。 相似文献
2.
3.
Ten-day treatment with nicotine (5, 25 or 50 micrograms/ml drinking water) dose-dependently intensified gastric ulceration induced by cold-restraint, and emptying rate. Stomach contractions produced by graded doses of bethanechol i.v. were elevated further by nicotine treatment. It is suggested that chronic nicotine administration produces hypersensitivity of the gastric muscarinic receptors; stomach hypermotility contributes to the ulcer-worsening action of the alkaloid. 相似文献
4.
The Shwachman-Bodian-Diamond syndrome protein mediates translational activation of ribosomes in yeast 总被引:1,自引:0,他引:1
Menne TF Goyenechea B Sánchez-Puig N Wong CC Tonkin LM Ancliff PJ Brost RL Costanzo M Boone C Warren AJ 《Nature genetics》2007,39(4):486-495
The autosomal recessive disorder Shwachman-Diamond syndrome, characterized by bone marrow failure and leukemia predisposition, is caused by deficiency of the highly conserved Shwachman-Bodian-Diamond syndrome (SBDS) protein. Here, we identify the function of the yeast SBDS ortholog Sdo1, showing that it is critical for the release and recycling of the nucleolar shuttling factor Tif6 from pre-60S ribosomes, a key step in 60S maturation and translational activation of ribosomes. Using genome-wide synthetic genetic array mapping, we identified multiple TIF6 gain-of-function alleles that suppressed the pre-60S nuclear export defects and cytoplasmic mislocalization of Tif6 observed in sdo1Delta cells. Sdo1 appears to function within a pathway containing elongation factor-like 1, and together they control translational activation of ribosomes. Thus, our data link defective late 60S ribosomal subunit maturation to an inherited bone marrow failure syndrome associated with leukemia predisposition. 相似文献
5.
6.
7.
Hellgren M Strömberg P Gallego O Martras S Farrés J Persson B Parés X Höög JO 《Cellular and molecular life sciences : CMLS》2007,64(4):498-505
The metabolism of all-trans- and 9-cis-retinol/ retinaldehyde has been investigated with focus on the activities of human, mouse and rat alcohol dehydrogenase 2
(ADH2), an intriguing enzyme with apparently different functions in human and rodents. Kinetic constants were determined with
an HPLC method and a structural approach was implemented by in silico substrate dockings. For human ADH2, the determined Km values ranged from 0.05 to 0.3 μM and kcat values from 2.3 to 17.6 min−1, while the catalytic efficiency for 9-cis-retinol showed the highest value for any substrate. In contrast, poor activities
were detected for the rodent enzymes. A mouse ADH2 mutant (ADH2Pro47His) was studied that resembles the human ADH2 setup.
This mutation increased the retinoid activity up to 100-fold. The Km values of human ADH2 are the lowest among all known human retinol dehydrogenases, which clearly support a role in hepatic
retinol oxidation at physiological concentrations.
Received 12 October 2006; received after revision 6 December 2006; accepted 8 January 2007 相似文献
8.
9.
Houlden H Johnson J Gardner-Thorpe C Lashley T Hernandez D Worth P Singleton AB Hilton DA Holton J Revesz T Davis MB Giunti P Giunti P Wood NW 《Nature genetics》2007,39(12):1434-1436
The microtubule-associated protein tau (encoded by MAPT) and several tau kinases have been implicated in neurodegeneration, but only MAPT has a proven role in disease. We identified mutations in the gene encoding tau tubulin kinase 2 (TTBK2) as the cause of spinocerebellar ataxia type 11. Affected brain tissue showed substantial cerebellar degeneration and tau deposition. These data suggest that TTBK2 is important in the tau cascade and in spinocerebellar degeneration. 相似文献
10.
Risheg H Graham JM Clark RD Rogers RC Opitz JM Moeschler JB Peiffer AP May M Joseph SM Jones JR Stevenson RE Schwartz CE Friez MJ 《Nature genetics》2007,39(4):451-453
Opitz-Kaveggia syndrome (also known as FG syndrome) is an X-linked disorder characterized by mental retardation, relative macrocephaly, hypotonia and constipation. We report here that the original family for whom the condition is named and five other families have a recurrent mutation (2881C>T, leading to R961W) in MED12 (also called TRAP230 or HOPA), a gene located at Xq13 that functions as a thyroid receptor-associated protein in the Mediator complex. 相似文献