全文获取类型
收费全文 | 399篇 |
免费 | 39篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 12篇 |
2015年 | 6篇 |
2014年 | 20篇 |
2013年 | 28篇 |
2012年 | 21篇 |
2011年 | 20篇 |
2010年 | 16篇 |
2009年 | 8篇 |
2008年 | 17篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 27篇 |
2004年 | 23篇 |
2003年 | 14篇 |
2002年 | 22篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1967年 | 2篇 |
1963年 | 2篇 |
1960年 | 1篇 |
排序方式: 共有438条查询结果,搜索用时 171 毫秒
71.
Lajos Mátés Claudia Nicolae Matthias M?rgelin Ferenc Deák Ibolya Kiss Attila Aszódi 《Matrix biology》2004,23(3):195-204
Matrilins are putative adaptor proteins of the extracellular matrix (ECM) which can form both collagen-dependent and collagen-independent filamentous networks. While all known matrilins (matrilin-1, -2, -3, and -4) are expressed in cartilage, only matrilin-2 and matrilin-4 are abundant in non-skeletal tissues. To clarify the biological role of matrilin-2, we have developed a matrilin-2-deficient mouse strain. Matrilin-2 null mice show no gross abnormalities during embryonic or adult development, are fertile, and have a normal lifespan. Histological and ultrastructural analyses indicate apparently normal structure of all organs and tissues where matrilin-2 is expressed. Although matrilin-2 co-localizes with matrilin-4 in many tissues, Northern hybridization, semiquantitative RT-PCR, immunohistochemistry and biochemical analysis reveal no significant alteration in the steady-state level of matrilin-4 expression in homozygous mutant mice. Immunostaining of wild-type and mutant skin samples indicate no detectable differences in the expression and deposition of matrilin-2 binding partners including collagen I, laminin-nidogen complexes, fibrillin-2 and fibronectin. In addition, electron microscopy reveals an intact basement membrane at the epidermal-dermal junction and normal organization of the dermal collagen fibrils in mutant skin. These data suggest that either matrilin-2 and matrilin-2-mediated matrix-matrix interactions are dispensable for proper ECM assembly and function, or that they are efficiently compensated by other matrix components including wild-type levels of matrilin-4. 相似文献
72.
Lajos Sasvári Zoltán Hegyi & Péter Péczely 《Ethology : formerly Zeitschrift fur Tierpsychologie》2006,112(4):355-361
This study addressed the question of whether maternal condition during egg laying or the rearing environment has a greater effect on offspring testosterone levels. We tested this in field experiments on a population of tawny owls Strix aluco in Duna‐Ipoly National Park, Hungary. In the experiments with females of poor condition, when broods were supplied with extra food none of the nestlings died, whereas in control broods, which were not supplied with extra food, some nestlings did die. Large differences in testosterone levels were correlated positively with hatching order both in experimental and control broods. However, it was only in control broods that the later‐hatched nestlings with low testosterone concentrations, died. In the experiments with females of good condition, the males were removed and females and their broods were supplied with restricted amounts of food. In these broods starving nestlings, whose growth had stopped, were considered as having died and were removed from the nest and hand‐reared. In control broods all nestlings fledged, and both in experimental and control broods testosterone concentrations were more even between siblings. Both types of trials confirmed a maternal influence on offspring testosterone concentration: large between‐sibling differences in concentrations in the broods of females of poor condition, where some nestlings died, could not be reduced with increased food supply, and the more even concentrations in the broods of females in good condition, where all nestlings survived, could also not be increased by restricting the food supply. 相似文献
73.
74.
Jan Sejbal Yunjun Wang John R. Cann John M. Stewart Lajos Gera George Kotovych 《Biopolymers》1997,42(5):521-535
Extensive proton magnetic resonance experiments were carried out on three bradykinin peptide antagonists B-9430, B-9436, and B-9858 in aqueous solutions as well as in sodium dodecylsulphate micelles (B-9430 and B-9436) and CD3OH/H2O (60%/40%) mixtures for B-9858. All three peptides showed no observable secondary structure in aqueous solution. However, in their respective structure-inducing solvents, B-9430 (B1 and B2 receptor antagonist) and B-9436 (a B2 receptor antagonist) exhibit a type II β-turn involving residues 2–5, and B-9430 also exhibits a type II′ β-turn involving residues 6–9 (in sodium dodecylsulfate micellar solutions), whereas B-9858, a B1-specific receptor antagonist, exhibits only a type II β-turn involving residues 2–5 (in CD3OH/H2O solutions). Simulated annealing calculations on B-9858 confirm the experimental conclusions based on the nmr data. In addition, simulated annealing of the (2S, 3aS, 7aS)-octahydroindole-2-carboxylic acid (Oic residue), which is present in two of the three decapeptides studied, show that the one-chair conformation of the six-membered ring predominates, in agreement with the experimental data. The activities of these peptides are compared with their secondary structures and the specific receptor activity appears to depend on the presence of specific amino acid residues, such as N-(2-indanyl)glycine (Nig) and D[α-(2-indanyl)glycine] (D-Igl) as well as on elements of secondary structure. © 1997 John Wiley & Sons, Inc. Biopoly 42: 521–535, 1997 相似文献
75.
76.
During the extremely dry period between 2000 and 2003, the water level of Lake Balaton decreased by 82 cm and 80% of the stony littoral, an important habitat for the zebra mussel (Dreissena polymorpha), became dry. A recovery period started in 2004 due to intense precipitation, which increased water levels in the lake. Seasonal and spatial variations of the relative abundance, population density, population structure and biomass of the zebra mussel and the relative abundance of the amphipod Chelicorophium curvispinum were monitored in the period of 2003–2005 at four different shoreline sections and in two different portions (on the bottom and near the surface portion of the rip-rap) of Lake Balaton. Along with these studies, a quantitative survey of mussel larvae found in the plankton and of the abundance of mussel feeding diving ducks were made. As a consequence of the water level fall, on the dried part of the stony littoral, numerous zebra mussel druses perished. Following the dry period in early 2004, the relative abundance of the mussel on the bottom stones was smaller than in 2003 and the bottom community was dominated by C. curvispinum. By the end of 2004 and during 2005, the water level returned to normal and the surfaces of the reinundated stones were conducive to the successful colonization of zebra mussels. Hence, they returned as the dominant fauna in 2005. The stones near the surface might provide a new substrate for the recruitment of zebra mussels, probably offering more suitable substrata for the settlement in 2005 than in 2003. Therefore, the new substrata available in 2005 may have encouraged better and more rapid zebra mussel colonization than before. Zebra mussels may be better competitors for new space than C. curvispinum. A minor change of water-level fluctuation in 2005 and the reduction in population size of the mussel feeding waterfowl could have contributed to the intensive spread of zebra mussel by 2005. 相似文献
77.
Kiss A Balikó G Csorba A Chuluunbaatar T Medzihradszky KF Alföldi L 《Journal of bacteriology》2008,190(19):6448-6457
Upon induction, Bacillus megaterium 216 produces the bacteriocin megacin A-216, which leads to lysis of the producer cell and kills B. megaterium and a few other bacterial species. The DNA region responsible for megacinogeny was cloned in B. megaterium. The nucleotide sequence of a 5,494-bp-long subfragment was determined, and the function of the genes on this fragment was studied by generating deletions and analyzing their effects on MegA phenotypes. An open reading frame (ORF) encoding a 293-amino-acid protein was identified as the gene (megA) coding for megacin A-216. BLAST searches detected sequence similarity between megacin A-216 and proteins with phospholipase A2 activity. Purified biologically active megacin A-216 preparations contained three proteins. Mass spectrometry analysis showed that the largest protein is the full-length translation product of the megA gene, whereas the two shorter proteins are fragments of the long protein created by cleavage between Gln-185 and Val-186. The molecular masses of the three polypeptides are 32,855, 21,018, and 11,855 Da, respectively. Comparison of different megacin preparations suggests that the intact chain as well as the two combined fragments can form biologically active megacin. An ORF located next to the megA gene and encoding a 91-amino-acid protein was shown to be responsible for the relative immunity displayed by the producer strain against megacin A-216. Besides the megA gene, at least two other genes, including a gene encoding a 188-amino-acid protein sharing high sequence similarity with RNA polymerase sigma factors, were shown to be required for induction of megacin A-216 expression. 相似文献
78.
Picoeukaryotes dominate the phytoplankton of Lake Balaton—the largest shallow lake in Central Europe—in the winter period.
We examined the annual dynamics of picoplankton abundance and composition in the lake in order to establish if the picoeukaryotes
merely survive the harsher winter conditions or they are able to grow in the ice-covered lake when the entire phytoplankton
is limited by low light and temperature. Lake Balaton has an annual temperature range of 1–29°C, and it is usually frozen
between December and February for 30–60 days. In the spring-autumn period phycocyanin and phycoerythrin rich Cyanobacteria
are the dominant picoplankters, and picoeukaryotes are negligible. Our five-year study shows the presence of three types of
picophytoplankton assemblages in Lake Balaton: (1) Phycoerythrin-rich Cyanobacteria—the dominant summer picoplankters in the
mesotrophic lake area; (2) Phycocyanin-rich Cyanobacteria—the most abundant summer picoplankters in the eutrophic lake area
and; (3) Picoeukaryotes—the dominant winter picoplankters in the whole lake. The observed winter abundance of picoeukaryotes
was high (up to 3 × 105 cells ml−1), their highest biomass (520 μg l−1) exceeded the maximum summer biomass of picocyanobacteria (500 μg l−1). Our results indicate that the winter predominance of picoeukaryotes is a regular phenomenon in Lake Balaton, irrespective
of the absence or presence of the ice cover. Picoeukaryotes are able to grow at as low as 1–2°C water temperature, while the
total phytoplankton biomass show the lowest annual values in the winter period. In agreement with earlier findings, the contribution
of picocyanobacteria to the total phytoplankton biomass in Lake Balaton is inversely related to the total phytoplankton biomass,
whereas no such relationship was observable in the case of picoeukaryotes. 相似文献
79.
Szatmari I Vámosi G Brazda P Balint BL Benko S Széles L Jeney V Ozvegy-Laczka C Szántó A Barta E Balla J Sarkadi B Nagy L 《The Journal of biological chemistry》2006,281(33):23812-23823
80.
According to current estimations ~95% of multi-exonic human protein-coding genes undergo alternative splicing (AS). However, for 4000 human proteins in PDB, only 14 human proteins have structures of at least two alternative isoforms. Surveying these structural isoforms revealed that the maximum insertion accommodated by an isoform of a fully ordered protein domain was 5 amino acids, other instances of domain changes involved intrinsic structural disorder. After collecting 505 minor isoforms of human proteins with evidence for their existence we analyzed their length, protein disorder and exposed hydrophobic surface. We found that strict rules govern the selection of alternative splice variants aimed to preserve the integrity of globular domains: alternative splice sites (i) tend to avoid globular domains or (ii) affect them only marginally or (iii) tend to coincide with a location where the exposed hydrophobic surface is minimal or (iv) the protein is disordered. We also observed an inverse correlation between the domain fraction lost and the full length of the minor isoform containing the domain, possibly indicating a buffering effect for the isoform protein counteracting the domain truncation effect. These observations provide the basis for a prediction method (currently under development) to predict the viability of splice variants. 相似文献