全文获取类型
收费全文 | 1472篇 |
免费 | 182篇 |
专业分类
1654篇 |
出版年
2021年 | 19篇 |
2019年 | 15篇 |
2016年 | 18篇 |
2015年 | 38篇 |
2014年 | 38篇 |
2013年 | 45篇 |
2012年 | 56篇 |
2011年 | 57篇 |
2010年 | 40篇 |
2009年 | 43篇 |
2008年 | 43篇 |
2007年 | 43篇 |
2006年 | 54篇 |
2005年 | 47篇 |
2004年 | 54篇 |
2003年 | 42篇 |
2002年 | 49篇 |
2001年 | 49篇 |
2000年 | 62篇 |
1999年 | 48篇 |
1998年 | 26篇 |
1997年 | 22篇 |
1996年 | 26篇 |
1995年 | 18篇 |
1994年 | 14篇 |
1993年 | 16篇 |
1992年 | 31篇 |
1991年 | 30篇 |
1990年 | 30篇 |
1989年 | 37篇 |
1988年 | 25篇 |
1987年 | 29篇 |
1986年 | 22篇 |
1985年 | 32篇 |
1984年 | 28篇 |
1983年 | 23篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1979年 | 26篇 |
1978年 | 17篇 |
1977年 | 13篇 |
1975年 | 20篇 |
1974年 | 21篇 |
1973年 | 22篇 |
1971年 | 14篇 |
1970年 | 17篇 |
1969年 | 25篇 |
1968年 | 15篇 |
1967年 | 15篇 |
1966年 | 14篇 |
排序方式: 共有1654条查询结果,搜索用时 10 毫秒
41.
Gunewardene MS Subach FV Gould TJ Penoncello GP Gudheti MV Verkhusha VV Hess ST 《Biophysical journal》2011,(6):1019-1528
Localization-based superresolution optical imaging is rapidly gaining popularity, yet limited availability of genetically encoded photoactivatable fluorescent probes with distinct emission spectra impedes simultaneous visualization of multiple molecular species in living cells. We introduce PAmKate, a monomeric photoactivatable far-red fluorescent protein, which facilitates simultaneous imaging of three photoactivatable proteins in mammalian cells using fluorescence photoactivation localization microscopy (FPALM). Successful probe identification was achieved by measuring the fluorescence emission intensity in two distinct spectral channels spanning only ∼100 nm of the visible spectrum. Raft-, non-raft-, and cytoskeleton-associated proteins were simultaneously imaged in both live and fixed fibroblasts coexpressing Dendra2-hemagglutinin, PAmKate-transferrin receptor, and PAmCherry1-β-actin fusion constructs, revealing correlations between the membrane proteins and membrane-associated actin structures. 相似文献
42.
Megasporogenesis and embryo sac development in the sexually reproducing taxa Bouteloua warnockii (2n = 22), B. media (2n = 20), B. uniflora Vasey var. uniflora (2n = 20), B. uniflora var. coahuilensis Gould and Kapadia (2n = 20), and B. curtipendula var. curlipendula (2n = 40) all were found to be of the Adoxa type, in which all 4 megaspores persist and divide once to form an 8-nucleate embryo sac. On the other hand, evidence indicated that plants of B. curtipendula var. caespitosa with high ancuploid chromosome numbers reproduce by pseudogamous fertilization of an aposporous embryo sac. In this taxon the megaspore mother cell did not go beyond the first anaphase of meiosis and the functional embryo sac developed from a nucellar cell. Although the 8-nucleate embryo sac was typical, a 3-nucleate embryo sac was observed to develop in some cases. 相似文献
43.
Maarten A. Jongsma Fred Gould Mathieu Legros Limei Yang Joop J. A. van Loon Marcel Dicke 《Evolutionary ecology》2010,24(5):1017-1030
The major lepidopteran insect pests of cotton and maize harbor intra-specific variation for behavior determining the selection
of host plants for oviposition. Yet, the consequences of behavioral adaptation for fitness have neither been modeled nor monitored
for Bt cotton and maize crops, the most widely grown transgenic herbivore-resistant plants. Here, we present a general two-locus
heuristic model to examine potential outcomes of natural selection when pest populations initially have low frequencies of
alleles for both physiological and behavioral adaptation to Bt crops. We demonstrate that certain ecological conditions allow for the evolution of behavioral choices favoring alternative
oviposition hosts that limit the increase in resistance alleles, even when they are phenotypically dominant. These results
have implications for current refuge policies, which should be adapted to promote the evolution of certain behavioral choices
for alternative oviposition hosts in addition to dilution of physiological resistance alleles. Collection of data on oviposition
host preference as a component of monitoring schemes will provide important insights into mechanisms underlying the durability
of Bt-transgenic host-plant resistance. 相似文献
44.
Susan F. Gould 《Restoration Ecology》2012,20(2):250-259
Rehabilitation of post‐mining lands frequently aims to create “self‐sustaining” systems. Where native vegetation is the designated post‐mining land use, it is generally assumed that rehabilitation that is similar to local native ecosystems is more likely to be sustainable. I compared landscape functionality, plant community composition, and vegetation structure in (1) reference sites representing pre‐mining native forest; (2) reference sites representing potential landscape analogues for the post‐mining landscape; and (3) a 23‐year chronosequence of post‐mining rehabilitation on the Weipa bauxite plateau, Cape York Peninsula, Australia. The trends across the post‐mining chronosequence indicate that vegetation growth is rapid in the first 5–8 years, and then slows with mean height approaching an asymptote after approximately 15 years. Landscape function indices showed a response that coincided with vegetation growth. Vegetation composition was significantly different from reference native forest. Most importantly, from the perspective of creating self‐sustaining ecosystems, the contribution of local framework species to vegetation in rehabilitation was significantly lower than in reference native forest. I discuss the results in relation to theoretical models of succession and conclude that without management intervention, differences between post‐mining rehabilitation and native forest are likely to be persistent. 相似文献
45.
Arfophilins are dual Arf/Rab 11 binding proteins that regulate recycling endosome distribution and are related to Drosophila nuclear fallout 下载免费PDF全文
Hickson GR Matheson J Riggs B Maier VH Fielding AB Prekeris R Sullivan W Barr FA Gould GW 《Molecular biology of the cell》2003,14(7):2908-2920
Arfophilin is an ADP ribosylation factor (Arf) binding protein of unknown function. It is identical to the Rab11 binding protein eferin/Rab11-FIP3, and we show it binds both Arf5 and Rab11. We describe a related protein, arfophilin-2, that interacts with Arf5 in a nucleotide-dependent manner, but not Arf1, 4, or 6 and also binds Rab11. Arfophilin-2 localized to a perinuclear compartment, the centrosomal area, and focal adhesions. The localization of arfophilin-2 to the perinuclear compartment was selectively blocked by overexpression of Arf5-T31N. In contrast, a green fluorescent protein-arfophilin-2 chimera or arfophilin-2 deletions were localized around the centrosome in a region that was also enriched for transferrin receptors and Rab11 but not early endosome markers, suggesting that the distribution of the endosomal recycling compartment was altered. The arfophilins belong to a conserved family that includes Drosophila melanogaster nuclear fallout, a centrosomal protein required for cellularization. Expression of green fluorescent protein-nuclear fallout in HeLa cells resulted in a similar phenotype, indicative of functional homology and thus implicating the arfophilins in mitosis/cytokinesis. We suggest that the novel dual GTPase-binding capacity of the arfophilins could serve as an interface of signals from Rab and Arf GTPases to regulate membrane traffic and integrate distinct signals in the late endosomal recycling compartment. 相似文献
46.
47.
John E. Gould James W. Overstreet Frederick W. Hanson 《Molecular reproduction and development》1985,12(1):47-54
The functional capacity for sperm interaction with the human zona pellucida and zona-free hamster oocyte was tested after human spermatozoa were capacitated by passage through a column of human cervical mucus. The results were compared with those obtained when spermatozoa from an aliquot of the same semen sample were capacitated by the standard laboratory methods involving sequential washing by dilution and centrifugation of the semen. Washed-capacitated sperm suspensions were more successful than mucus-capacitated sperm in attaching to the zona-free hamster oocyte and in fusing with its oolemma. However, the ability of mucus-capacitated sperm to penetrate the human zona pellucida was equal to washed capacitated sperm. These experiments demonstrate an approach that may be useful in comparative studies of human sperm capacitation in vivo and in vitro. 相似文献
48.
Identification of a cDNA encoding a long form of prolactin receptor in human hepatoma and breast cancer cells 总被引:19,自引:0,他引:19
J M Boutin M Edery M Shirota C Jolicoeur L Lesueur S Ali D Gould J Djiane P A Kelly 《Molecular endocrinology (Baltimore, Md.)》1989,3(9):1455-1461
Human PRL receptor cDNA clones from hepatoma (Hep G2) and breast cancer (T-47D) libraries were isolated by using a rat PRL receptor cDNA probe. The nucleotide sequence predicts a mature protein of 598 amino acids with a much longer cytoplasmic domain than the rat liver PRL receptor. Although this extended region has additional segments of localized sequence identity with the human GH receptor, there is no identity with any consensus sequences known to be involved in hormonal signal transduction. This cDNA will be a valuable tool to better understand the role of PRL in the development and growth of human breast cancer. 相似文献
49.
The prevailing hypothesis of HIV budding posits that the viral Gag protein drives budding, and that the Gag p6 peptide plays an essential role by recruiting host-cell budding factors to sites of HIV assembly. HIV also expresses a second Gag protein, p160 Gag-Pol, which lacks p6 and fails to bud from cells, consistent with the prevailing hypothesis of HIV budding. However, we show here that the severe budding defect of Gag-Pol is not caused by the absence of p6, but rather, by the presence of Pol. Specifically, we show that (i) the budding defect of Gag-Pol is unaffected by loss of HIV protease activity and is therefore an intrinsic property of the Gag-Pol polyprotein, (ii) the N-terminal 433 amino acids of Gag and Gag-Pol are sufficient to drive virus budding even though they lack p6, (iii) the severe budding defect of Gag-Pol is caused by a dominant, cis-acting inhibitor of budding in the HIV Pol domain, and (iv) Gag-Pol inhibits Gag and virus budding in trans, even at normal levels of Gag and Gag-Pol expression. These and other data support an alternative hypothesis of HIV budding as a process that is mediated by the normal, non-viral pathway of exosome/microvesicle biogenesis. 相似文献
50.
Motility patterns of caput epididymal chimpanzee sperm, caput epididymal chimpanzee sperm incubated in vitro with chimpanzee cauda epididymal fluid, and cauda epididymal chimpanzee sperm were assessed quantitatively. Sperm recovered from the caput epididymis showed no motility, whereas sperm recovered from cauda epididymis showed progressive forward motility. After incubation in cauda fluid, approximately 25% of caput epididymal sperm showed some motile activity. Electrophoretic analysis of 125I-labeled sperm plasma membrane preparations revealed that the surface of caput epididymal sperm, incubated in cauda fluid, was modified by the appearance of a major protein-glycoprotein surface component with an apparent molecular weight of 27 kilodaltons (kD). THis 27-kD component was not detected on caput epididymal sperm incubated in buffer or in caput fluid. However, it was present in cauda fluid and on cauda epididymal sperm. Binding to caput epididymal sperm was cell specific in that chimpanzee erythrocytes incubated in cauda fluid did not bind this 27-kD cauda fluid component. Motility patterns of ejaculated chimpanzee sperm and of ejaculated chimpanzee sperm incubated in the uterus of adult female chimpanzees also were assessed quantitatively. Ejaculated sperm showed progressive forward motility, whereas in utero incubated ejaculated sperm showed hyperactivated motility typical of capacitated sperm. Electrophoretic analysis of 125I-labeled sperm plasma membrane preparations revealed the loss of a 27-kD component from the surface of ejaculated sperm after in utero incubation. No significant change in the 125I-distribution pattern was detectable when ejaculated sperm were incubated in buffer. These results suggest that the lumenal fluid component, which becomes adsorbed to the surface of chimpanzee sperm during maturation in the epididymis and which is removed from the surface of mature chimpanzee sperm in the female reproductive tract, affects sperm motility. 相似文献