全文获取类型
收费全文 | 578篇 |
免费 | 6篇 |
专业分类
系统科学 | 26篇 |
丛书文集 | 1篇 |
教育与普及 | 1篇 |
理论与方法论 | 9篇 |
现状及发展 | 278篇 |
研究方法 | 54篇 |
综合类 | 202篇 |
自然研究 | 13篇 |
出版年
2020年 | 5篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 11篇 |
2013年 | 10篇 |
2012年 | 33篇 |
2011年 | 38篇 |
2010年 | 17篇 |
2008年 | 29篇 |
2007年 | 21篇 |
2006年 | 21篇 |
2005年 | 24篇 |
2004年 | 22篇 |
2003年 | 20篇 |
2002年 | 19篇 |
2001年 | 16篇 |
2000年 | 9篇 |
1999年 | 13篇 |
1998年 | 7篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1972年 | 11篇 |
1971年 | 7篇 |
1970年 | 8篇 |
1969年 | 10篇 |
1968年 | 10篇 |
1967年 | 4篇 |
1966年 | 9篇 |
1965年 | 5篇 |
1964年 | 3篇 |
排序方式: 共有584条查询结果,搜索用时 15 毫秒
241.
In this introductory paper to the special issue ofSystems Practice devoted to Interpretive Systemology, some of the conditions under which this trend in systems thinking has come to life are briefly depicted. For that purpose a wider and a narrower scene are presented. The wider scene presents the general questions and problems that are to be tackled by Interpretive Systemology, within a wide international perspective of systems thinking and practice. The narrower scene, which is related to more particular conditions, shows how some circumstances connected to the socalled Third World or underdeveloped countries have helped to trigger the launching of Interpretive Systemology. Finally, a brief outline of the research program for Interpretive Systemology is introduced. 相似文献
242.
Summary An apparent suppression of dot-like exchanges in C-bands and late replicating DNA-rich regions of chromosomes has been observed inAllium cepa. This result suggests that the occurrence of SCE very near each other could be avoided in these chromosomal regions. 相似文献
243.
O. Suzuki M. Oya Y. Katsumata T. Matsumoto S. Yada 《Cellular and molecular life sciences : CMLS》1979,35(10):1289-1290
Summary Mitochondrial monoamine oxidase (MAO) was found in human semen, showing its Km and Vmax values of 91.7 M and 290 pmoles/mg of protein/60 min, respectively, with kynuramine as substrate. A major part of the activity was due to type A MAO. 相似文献
244.
245.
DNA double-strand breaks (DSBs) are repaired by two principal mechanisms: non-homologous end-joining (NHEJ) and homologous recombination (HR). HR is the most accurate DSB repair mechanism but is generally restricted to the S and G2 phases of the cell cycle, when DNA has been replicated and a sister chromatid is available as a repair template. By contrast, NHEJ operates throughout the cell cycle but assumes most importance in G1 (refs 4, 6). The choice between repair pathways is governed by cyclin-dependent protein kinases (CDKs), with a major site of control being at the level of DSB resection, an event that is necessary for HR but not NHEJ, and which takes place most effectively in S and G2 (refs 2, 5). Here we establish that cell-cycle control of DSB resection in Saccharomyces cerevisiae results from the phosphorylation by CDK of an evolutionarily conserved motif in the Sae2 protein. We show that mutating Ser 267 of Sae2 to a non-phosphorylatable residue causes phenotypes comparable to those of a sae2Delta null mutant, including hypersensitivity to camptothecin, defective sporulation, reduced hairpin-induced recombination, severely impaired DNA-end processing and faulty assembly and disassembly of HR factors. Furthermore, a Sae2 mutation that mimics constitutive Ser 267 phosphorylation complements these phenotypes and overcomes the necessity of CDK activity for DSB resection. The Sae2 mutations also cause cell-cycle-stage specific hypersensitivity to DNA damage and affect the balance between HR and NHEJ. These findings therefore provide a mechanistic basis for cell-cycle control of DSB repair and highlight the importance of regulating DSB resection. 相似文献
246.
García-Castellanos R Bonet-Figueredo R Pallarés I Ventura S Avilés FX Vendrell J Gomis-Rütha FX 《Cellular and molecular life sciences : CMLS》2005,62(17):1996-2014
Treatment of advanced stages of prostate carcinoma with histone-deacetylase inhibitors entails expression of human procarboxypeptidase-A4 (hPCPA4). The three-dimensional structure of hPCPA4 has been solved and shows the features of related metallocarboxypeptidase zymogens, with a preformed α/β/-hydrolase active-enzyme moiety (hCPA4) and an inhibiting pro-domain (PD). The protease moiety recalls a sphere, out of which a spherical cone has been cut. This results in a funnel-like structure, at the bottom of which the active-site cleft resides. The border of this funnel is shaped by loops, which are responsible for the interaction with the PD, characterised by a large interface area and relatively few contacts. Such an inhibitory mode is evocative of the recently reported structure of the human inhibitor latexin in its complex with hCPA4. The main contacting structure of latexin is similar to the one employed for PD inhibition. In both cases, active-site blocking relies mainly on a loop provided by the central part of a β sheet.R. Garcia-Castellanos and R. Bonet-Figueredo contributed equally to this study and share first authorship.Received 28 April 2005; received after revision 1 June 2005; accepted 29 June 2005 相似文献
247.
Sakuntabhai A Turbpaiboon C Casadémont I Chuansumrit A Lowhnoo T Kajaste-Rudnitski A Kalayanarooj SM Tangnararatchakit K Tangthawornchaikul N Vasanawathana S Chaiyaratana W Yenchitsomanus PT Suriyaphol P Avirutnan P Chokephaibulkit K Matsuda F Yoksan S Jacob Y Lathrop GM Malasit P Desprès P Julier C 《Nature genetics》2005,37(5):507-513
248.
The impact of population structure on association studies undertaken to identify genetic variants underlying common human diseases is an issue of growing interest. Spurious associations of alleles with disease phenotypes may be obtained or true associations overlooked when allele frequencies differ notably among subpopulations that are not represented equally among cases and controls. Population structure influences even carefully designed studies and can affect the validity of association results. Most study designs address this problem by sampling cases and controls from groups that share the same nationality or self-reported ethnic background, with the implicit assumption that no substructure exists within such groups. We examined population structure in the Icelandic gene pool using extensive genealogical and genetic data. Our results indicate that sampling strategies need to take account of substructure even in a relatively homogenous genetic isolate. This will probably be even more important in larger populations. 相似文献
249.
250.
J H Espié N Legendre S Després 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1979,288(4):405-408
Turnover of desmodontal ligament is analysed in the Baboon using labeling, biochemical and histological techniques. In Baboons, as previously observed in rodents, turnover of proteins labelled by 3H glycine may be described by a single exponential after the ninth day, the half life of which is more than two weeks. Biochemical data show that proteins renewed are mostly collagen. 相似文献