全文获取类型
收费全文 | 3313篇 |
免费 | 98篇 |
国内免费 | 24篇 |
专业分类
系统科学 | 122篇 |
丛书文集 | 3篇 |
教育与普及 | 2篇 |
理论与方法论 | 26篇 |
现状及发展 | 1084篇 |
研究方法 | 46篇 |
综合类 | 2137篇 |
自然研究 | 15篇 |
出版年
2024年 | 14篇 |
2023年 | 27篇 |
2022年 | 11篇 |
2020年 | 12篇 |
2017年 | 13篇 |
2016年 | 37篇 |
2015年 | 56篇 |
2014年 | 39篇 |
2013年 | 25篇 |
2012年 | 151篇 |
2011年 | 170篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 18篇 |
2005年 | 204篇 |
2004年 | 510篇 |
2003年 | 469篇 |
2002年 | 145篇 |
2001年 | 78篇 |
2000年 | 141篇 |
1999年 | 76篇 |
1992年 | 38篇 |
1991年 | 27篇 |
1990年 | 36篇 |
1989年 | 36篇 |
1988年 | 33篇 |
1987年 | 17篇 |
1986年 | 27篇 |
1985年 | 40篇 |
1984年 | 28篇 |
1983年 | 31篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 72篇 |
1978年 | 49篇 |
1977年 | 33篇 |
1976年 | 31篇 |
1975年 | 40篇 |
1974年 | 57篇 |
1973年 | 52篇 |
1972年 | 50篇 |
1971年 | 67篇 |
1970年 | 56篇 |
1969年 | 70篇 |
1968年 | 64篇 |
1967年 | 44篇 |
1966年 | 55篇 |
1965年 | 42篇 |
1964年 | 11篇 |
排序方式: 共有3435条查询结果,搜索用时 87 毫秒
61.
Khan ZU Martín-Montañez E Baxter MG 《Cellular and molecular life sciences : CMLS》2011,68(10):1737-1754
Visual perception and memory are the most important components of vision processing in the brain. It was thought that the
perceptual aspect of a visual stimulus occurs in visual cortical areas and that this serves as the substrate for the formation
of visual memory in a distinct part of the brain called the medial temporal lobe. However, current evidence indicates that
there is no functional separation of areas. Entire visual cortical pathways and connecting medial temporal lobe are important
for both perception and visual memory. Though some aspects of this view are debated, evidence from both sides will be explored
here. In this review, we will discuss the anatomical and functional architecture of the entire system and the implications
of these structures in visual perception and memory. 相似文献
62.
63.
64.
65.
An inflammatory drug prospect. 总被引:2,自引:0,他引:2
66.
电梯上高峰模式下动态分区算法的研究 总被引:1,自引:0,他引:1
研究了电梯群控系统(EGCS)上行高峰时期的动态分区群控方法.动态分区是根据大楼乘客流量的大小和分布情况动态地调整楼层区域的划分;同时提出了一致的UPPINT的目标函数,将动态分区问题归结为一个最优化问题,用直接搜索法对其进行求解;并对群控的几种算法进行了仿真比较,验证了动态分区算法的良好效果. 相似文献
67.
Anderson BH Kasher PR Mayer J Szynkiewicz M Jenkinson EM Bhaskar SS Urquhart JE Daly SB Dickerson JE O'Sullivan J Leibundgut EO Muter J Abdel-Salem GM Babul-Hirji R Baxter P Berger A Bonafé L Brunstom-Hernandez JE Buckard JA Chitayat D Chong WK Cordelli DM Ferreira P Fluss J Forrest EH Franzoni E Garone C Hammans SR Houge G Hughes I Jacquemont S Jeannet PY Jefferson RJ Kumar R Kutschke G Lundberg S Lourenço CM Mehta R Naidu S Nischal KK Nunes L Ounap K Philippart M Prabhakar P Risen SR 《Nature genetics》2012,44(3):338-342
Coats plus is a highly pleiotropic disorder particularly affecting the eye, brain, bone and gastrointestinal tract. Here, we show that Coats plus results from mutations in CTC1, encoding conserved telomere maintenance component 1, a member of the mammalian homolog of the yeast heterotrimeric CST telomeric capping complex. Consistent with the observation of shortened telomeres in an Arabidopsis CTC1 mutant and the phenotypic overlap of Coats plus with the telomeric maintenance disorders comprising dyskeratosis congenita, we observed shortened telomeres in three individuals with Coats plus and an increase in spontaneous γH2AX-positive cells in cell lines derived from two affected individuals. CTC1 is also a subunit of the α-accessory factor (AAF) complex, stimulating the activity of DNA polymerase-α primase, the only enzyme known to initiate DNA replication in eukaryotic cells. Thus, CTC1 may have a function in DNA metabolism that is necessary for but not specific to telomeric integrity. 相似文献
68.
69.
Microautophagy: lesser-known self-eating 总被引:1,自引:1,他引:0
Microautophagy, the non-selective lysosomal degradative process, involves direct engulfment of cytoplasmic cargo at a boundary
membrane by autophagic tubes, which mediate both invagination and vesicle scission into the lumen. With its constitutive characteristics,
microautophagy of soluble substrates can be induced by nitrogen starvation or rapamycin via regulatory signaling complex pathways.
The maintenance of organellar size, membrane homeostasis, and cell survival under nitrogen restriction are the main functions
of microautophagy. In addition, microautophagy is coordinated with and complements macroautophagy, chaperone-mediated autophagy,
and other self-eating pathways. Three forms of selective microautophagy, including micropexophagy, piecemeal microautophagy
of the nucleus, and micromitophagy, share common ground with microautophagy to some degree. As the accumulation of experimental
data, the precise mechanisms that govern microautophagy are becoming more appreciated. Here, we review the microautophagic
molecular machinery, its physiological functions, and relevance to human diseases, especially in diseases involving multivesicular
bodies and multivesicular lysosomes. 相似文献
70.
Angela M. Ortega-León Maricela Villagrán-Santa Cruz J. Jamie Zú?iga-Vega Raúl Cueva-del Castillo Fausto R. Méndez-de la Cruz 《西北部美国博物学家》2011,69(1)
Asynchronous reproduction is a common phenomenon in high-elevation populations of lizards from Central México. Sperm storage in the reproductive tract of females is the mechanism for making oocyte fertilization possible. Our study addresses questions related to functional oviductal sperm storage of females mating on different dates throughout the reproductive season. A population of Sceloporus mucronatus with copulation in the summer and ovulation in the fall was chosen for this experiment. Eleven females that copulated in the field during June and 13 females that copulated in captivity during August were maintained in the laboratory until parturition. The number of pregnant females and the litter sizes produced in each experimental group were indicative of the viability of the stored sperm. Sperm stored in the reproductive tract of females were able to fertilize eggs after 4 months. No significant differences were found in the number of pregnant females between the 2 experimental groups nor in the litter sizes that they produced. We found that the amount of time sperm were held in the female reproductive tract (ca. 3 months) had no effect on the capacity of sperm to fertilize eggs. Histological examination of 8 oviducts collected before the mating season eliminated the possibility of sperm storage from one year to the next. In this system, sperm retention could have evolved as a response mechanism to deal with the asynchrony between sexes in the reproductive cycles. However, we cannot rule out alternative hypotheses. 相似文献