全文获取类型
收费全文 | 858篇 |
免费 | 72篇 |
国内免费 | 1篇 |
专业分类
931篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 17篇 |
2021年 | 39篇 |
2020年 | 24篇 |
2019年 | 31篇 |
2018年 | 47篇 |
2017年 | 19篇 |
2016年 | 22篇 |
2015年 | 44篇 |
2014年 | 41篇 |
2013年 | 64篇 |
2012年 | 67篇 |
2011年 | 57篇 |
2010年 | 34篇 |
2009年 | 29篇 |
2008年 | 51篇 |
2007年 | 61篇 |
2006年 | 37篇 |
2005年 | 39篇 |
2004年 | 32篇 |
2003年 | 25篇 |
2002年 | 30篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1971年 | 3篇 |
1960年 | 1篇 |
1904年 | 1篇 |
排序方式: 共有931条查询结果,搜索用时 15 毫秒
81.
Haselton MG Mortezaie M Pillsworth EG Bleske-Rechek A Frederick DA 《Hormones and behavior》2007,51(1):40-45
Humans differ from many other primates in the apparent absence of obvious advertisements of fertility within the ovulatory cycle. However, recent studies demonstrate increases in women's sexual motivation near ovulation, raising the question of whether human ovulation could be marked by observable changes in overt behavior. Using a sample of 30 partnered women photographed at high and low fertility cycle phases, we show that readily-observable behaviors - self-grooming and ornamentation through attractive choice of dress - increase during the fertile phase of the ovulatory cycle. At above-chance levels, 42 judges selected photographs of women in their fertile (59.5%) rather than luteal phase (40.5%) as "trying to look more attractive." Moreover, the closer women were to ovulation when photographed in the fertile window, the more frequently their fertile photograph was chosen. Although an emerging literature indicates a variety of changes in women across the cycle, the ornamentation effect is striking in both its magnitude and its status as an overt behavioral difference that can be easily observed by others. It may help explain the previously documented finding that men's mate retention efforts increase as their partners approach ovulation. 相似文献
82.
M V Mina 《Ontogenez》2001,32(6):471-476
The possibilities of the investigation of ontogenetic changes in the morphological features of fish using multidimensional "ontogenetic channels," within which individual ontogenetic trajectories run, are demonstrated using African barbs. (Barbus intermedius complex) as an example. The position of ontogenetic channels allows one to judge how the differences of adult individuals in morphological characters arise during development and how their morphological diversity is formed. 相似文献
83.
Maniataki E Martinez de Alba AE Sägesser R Tabler M Tsagris M 《RNA (New York, N.Y.)》2003,9(3):346-354
Viroids are noncoding circular single-stranded RNAs that are propagated systemically in plants. VirP1 is a protein from tomato, which is an excellent host for potato spindle tuber viroid (PSTVd), and it has been isolated by virtue of its specific in vitro binding to PSTVd RNA. We report on the specific in vivo interaction of VirP1 with full-length viroid RNA as well as with subfragments in the three-hybrid system. The terminal right domain (TR) of PSTVd was identified as a strong interacting partner for VirP1. A weaker partner is provided by a right-hand subfragment of hop stunt viroid (HSVd), a viroid that infects tomato poorly. We present a sequence and structural motif of the VirP1-interacting subfragments. The motif is disturbed in the replicative but nonspreading R+ mutant of the TR. According to our in vivo and in vitro binding assays, the interaction of this mutant with VirP1 is compromised. We propose that the AGG/CCUUC motif bolsters recognition of the TR by VirP1 to achieve access of the viroid to pathways that propagate endogenous RNA systemic signals in plants. Systemic trafficking has been suggested for miRNA precursors, of which the TR, as a stable bulged hairpin 71 nt long, is quite reminiscent. 相似文献
84.
The bph operon of Pseudomonas sp. KKS102 is constituted of 11 bph genes which encode enzymes for biphenyl assimilation. Growth of a mutant in which a large part of the bph operon was deleted was inhibited by biphenyl in a concentration-dependent manner. We constructed a series of bph operon deletion mutants and tested for their biphenyl sensitivity. Growth inhibition by biphenyl was more prominent with the mutants defective in bphA1, bphB, bphC, and bphD, which were clustered in the bph operon and working in the early stage of the biphenyl degradation. The mutant defective in bphE, which was working at the late stage and forming a different cluster from the early stage genes, was not much inhibited by biphenyl. These indicate that biphenyl is detoxified by enzymes which function in the early stage of biphenyl assimilation and thus detoxification of substrates as well as energy acquisition could have played an important role in the evolution of the KKS102 bph operon. 相似文献
85.
Barry AE Trieu A Fowkes FJ Pablo J Kalantari-Dehaghi M Jasinskas A Tan X Kayala MA Tavul L Siba PM Day KP Baldi P Felgner PL Doolan DL 《Molecular & cellular proteomics : MCP》2011,10(11):M111.008326
Individuals that are exposed to malaria eventually develop immunity to the disease with one possible mechanism being the gradual acquisition of antibodies to the range of parasite variant surface antigens in their local area. Major antibody targets include the large and highly polymorphic Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) family of proteins. Here, we use a protein microarray containing 123 recombinant PfEMP1-DBLα domains (VAR) from Papua New Guinea to seroprofile 38 nonimmune children (<4 years) and 29 hyperimmune adults (≥15 years) from the same local area. The overall magnitude, prevalence and breadth of antibody response to VAR was limited at <2 years and 2-2.9 years, peaked at 3-4 years and decreased for adults compared with the oldest children. An increasing proportion of individuals recognized large numbers of VAR proteins (>20) with age, consistent with the breadth of response stabilizing with age. In addition, the antibody response was limited in uninfected children compared with infected children but was similar in adults irrespective of infection status. Analysis of the variant-specific response confirmed that the antibody signature expands with age and infection. This also revealed that the antibody signatures of the youngest children overlapped substantially, suggesting that they are exposed to the same subset of PfEMP1 variants. VAR proteins were either seroprevalent from early in life, (<3 years), from later in childhood (≥3 years) or rarely recognized. Group 2 VAR proteins (Cys2/MFK-REY+) were serodominant in infants (<1-year-old) and all other sequence subgroups became more seroprevalent with age. The results confirm that the anti-PfEMP1-DBLα antibody responses increase in magnitude and prevalence with age and further demonstrate that they increase in stability and complexity. The protein microarray approach provides a unique platform to rapidly profile variant-specific antibodies to malaria and suggests novel insights into the acquisition of immunity to malaria. 相似文献
86.
Here, we describe a simple micromolding method to construct three-dimensional arrays of organotypic epithelial tissue structures that approximate in vivo histology. An elastomeric stamp containing an array of posts of defined geometry and spacing is used to mold microscale cavities into the surface of type I collagen gels. Epithelial cells are seeded into the cavities and covered with a second layer of collagen. The cells reorganize into hollow tissues corresponding to the geometry of the cavities. Patterned tissue arrays can be produced in 3-4 h and will undergo morphogenesis over the following 1-3 d. The protocol can easily be adapted to study a variety of tissues and aspects of normal and neoplastic development. 相似文献
87.
Changes of external morphological characters in three forms (morphotypes) of African barbs from Lake Tana (Ethiopia) belonging
to Barbus intermedius complex were traced using electronic tags. It was shown that within age interval from two to four years individual ontogenetic
allometric curves often cannot be described with a single power function equation. Individual ontogenetic trajectories in
the principal components space within this interval strongly differ in shape meandering within ontogenetic channels outlined
on the basis of cross-sectional data. Morphological differences between siblings are found that do not allow to classify some
of them with the morphotype of their parents. 相似文献
88.
The insoluble cytoskeletal material remaining after detergent lysis of 'Normal' Murine Mammary Gland (NMuMG) cells, growing on plastic or collagen gel substrata, was analyzed by two-dimensional gel electrophoresis. The identity of the cytoskeletal elements was determined by their solubility properties, electrophoretic separation pattern, and immunoreactivity using monoclonal antibodies against intermediate filament proteins (AIF), keratins (AE1 and AE3) and actin. The electrophoretic pattern of the cytoskeletal elements from the NMuMG cell strain was found to be very similar to that of primary mouse mammary epithelial cells. Both NMuMG and primary mammary epithelial cells when grown on collagen exhibited an increased expression of a 49 kD protein with a pI of 5.6, that appeared to be a cytokeratin. Many of the cytoskeletal proteins remained tightly attached to the collagen gel substratum after cell lysis. These results demonstrate that the NMuMG cell strain has retained a stable expression of cytokeratins that remains responsive to the presence of extracellular matrix material. 相似文献
89.
K. F. Dzerzhinskii F. N. Shkil Belay Abdissa Wondie Zelalem M. V. Mina 《Journal of Ichthyology》2007,47(8):639-646
Direct observations on three forms (morph types) of spawning barbs, considered by some authors as different species, were
carried out in September–October 2005 at the Gumara River and its small tributary, the Ducalit, in the Lake Tana basin. The
spawning barbs were sampled using cast nets. Barbs of different morphotypes composed common spawning aggregations and were
caught together. It is likely that troutlike females mate extensively with intermedius males and, probably, with bigmouth
small-eye males. Experiments in artificial fertilization and rearing showed that, during the embryonic period, there was no
increase in mortality of progeny from crosses of barbs of different morphotypes, in comparison with homonomic crosses, thus
suggesting an absence of postzygotic reproductive isolation between the morphotypes. At the same time, mortality of progeny
from crossing barbs with Varicorhinus beso Rüppell, 1836 was very high during the earliest stages of development, suggesting strong, even if incomplete, reproductive
isolation ensured by postzygotic mechanisms.
Published in Voprosy Ikhtiologii, 2007, Vol. 47, No. 5, pp. 676–683.
The article was translated by the authors. 相似文献
90.