全文获取类型
收费全文 | 35602篇 |
免费 | 96篇 |
国内免费 | 184篇 |
专业分类
系统科学 | 164篇 |
丛书文集 | 534篇 |
教育与普及 | 70篇 |
理论与方法论 | 121篇 |
现状及发展 | 16225篇 |
研究方法 | 1491篇 |
综合类 | 16740篇 |
自然研究 | 537篇 |
出版年
2013年 | 290篇 |
2012年 | 477篇 |
2011年 | 1035篇 |
2010年 | 203篇 |
2008年 | 625篇 |
2007年 | 694篇 |
2006年 | 664篇 |
2005年 | 673篇 |
2004年 | 655篇 |
2003年 | 623篇 |
2002年 | 618篇 |
2001年 | 1146篇 |
2000年 | 1077篇 |
1999年 | 764篇 |
1994年 | 358篇 |
1992年 | 730篇 |
1991年 | 543篇 |
1990年 | 621篇 |
1989年 | 614篇 |
1988年 | 564篇 |
1987年 | 651篇 |
1986年 | 596篇 |
1985年 | 762篇 |
1984年 | 602篇 |
1983年 | 483篇 |
1982年 | 436篇 |
1981年 | 454篇 |
1980年 | 551篇 |
1979年 | 1118篇 |
1978年 | 932篇 |
1977年 | 883篇 |
1976年 | 753篇 |
1975年 | 788篇 |
1974年 | 986篇 |
1973年 | 881篇 |
1972年 | 922篇 |
1971年 | 1022篇 |
1970年 | 1317篇 |
1969年 | 996篇 |
1968年 | 999篇 |
1967年 | 944篇 |
1966年 | 871篇 |
1965年 | 598篇 |
1959年 | 311篇 |
1958年 | 539篇 |
1957年 | 358篇 |
1956年 | 305篇 |
1955年 | 286篇 |
1954年 | 288篇 |
1948年 | 212篇 |
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
1.
2.
Photon emission of phagocytes in relation to stress and disease. 总被引:1,自引:0,他引:1
Phagocytes, the first-line cells of the body's defence mechanisms against invading pathogens, kill microorganisms by means of lysosomal degradative enzymes and highly toxic reactive oxygen intermediates. The reactive oxygen compounds are produced, in a process called the 'respiratory burst', by the NADPH oxidase complex in plasma membranes, and by myeloperoxidase in phagolysosomes after degranulation. These processes generate electronically excited states which, on relaxation, emit photons, giving rise to phagocyte chemiluminescence (CL). This paper describes the conditions for the measurement of CL, and reviews the activity of phagocytes from individuals undergoing stress or disease. The capability of phagocytes to emit photons reflects remarkably well the pathophysiological state of the host. In many cases even the magnitude of the stress, the presence of a pathogen in the body, or the activity of the disease can be estimated. Physiological changes, e.g. in the reproductive cycle, can also be predicted. 相似文献
3.
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
4.
5.
Alcaïs A Alter A Antoni G Orlova M Nguyen VT Singh M Vanderborght PR Katoch K Mira MT Vu HT Ngyuen TH Nguyen NB Moraes M Mehra N Schurr E Abel L 《Nature genetics》2007,39(4):517-522
Host genetics has an important role in leprosy, and variants in the shared promoter region of PARK2 and PACRG were the first major susceptibility factors identified by positional cloning. Here we report the linkage disequilibrium mapping of the second linkage peak of our previous genome-wide scan, located close to the HLA complex. In both a Vietnamese familial sample and an Indian case-control sample, the low-producing lymphotoxin-alpha (LTA)+80 A allele was significantly associated with an increase in leprosy risk (P = 0.007 and P = 0.01, respectively). Analysis of an additional case-control sample from Brazil and an additional familial sample from Vietnam showed that the LTA+80 effect was much stronger in young individuals. In the combined sample of 298 Vietnamese familial trios, the odds ratio of leprosy for LTA+80 AA/AC versus CC subjects was 2.11 (P = 0.000024), which increased to 5.63 (P = 0.0000004) in the subsample of 121 trios of affected individuals diagnosed before 16 years of age. In addition to identifying LTA as a major gene associated with early-onset leprosy, our study highlights the critical role of case- and population-specific factors in the dissection of susceptibility variants in complex diseases. 相似文献
6.
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
7.
8.
Hermann T 《Cellular and molecular life sciences : CMLS》2007,64(14):1841-1852
Aminoglycoside antibiotics kill bacteria by binding to the ribosomal decoding site and reducing fidelity of protein synthesis.
Since the discovery of these natural products over 50 years ago, aminoglycosides have provided a mainstay of antibacterial
therapy of serious Gram-negative infections. In recent years, aminoglycosides have become important tools to study molecular
recognition of ribonucleic acid (RNA). In an ingenious exploitation of the aminoglycosides’ mechanism of action, it has been
speculated that drug-induced readthrough of premature stop codons in mutated messenger RNAs might be used to treat patients
suffering from certain heritable genetic disorders.
Received 23 January 2007; received after revision 25 February 2007; accepted 29 March 2007 相似文献
9.
10.