全文获取类型
收费全文 | 1455篇 |
免费 | 140篇 |
国内免费 | 2篇 |
出版年
2023年 | 9篇 |
2022年 | 12篇 |
2021年 | 31篇 |
2020年 | 14篇 |
2019年 | 17篇 |
2018年 | 24篇 |
2017年 | 21篇 |
2016年 | 37篇 |
2015年 | 61篇 |
2014年 | 74篇 |
2013年 | 90篇 |
2012年 | 113篇 |
2011年 | 103篇 |
2010年 | 64篇 |
2009年 | 71篇 |
2008年 | 100篇 |
2007年 | 95篇 |
2006年 | 79篇 |
2005年 | 86篇 |
2004年 | 70篇 |
2003年 | 73篇 |
2002年 | 83篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1990年 | 5篇 |
1988年 | 6篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1980年 | 5篇 |
1978年 | 5篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1971年 | 4篇 |
1969年 | 4篇 |
1966年 | 4篇 |
1908年 | 5篇 |
1899年 | 3篇 |
1889年 | 4篇 |
1887年 | 3篇 |
排序方式: 共有1597条查询结果,搜索用时 15 毫秒
51.
Three different software packages for the probe-level analysis of high-density oligonucleotide microarray data were compared using an experiment-derived data set that was validated using real-time PCR. The efficiency with which these three programs could identify true positives in this data set was assessed. In addition, estimates of false-positive and false-negative rates were determined. The performance of the programs using very small data sets was also compared, and recommendations for use are suggested. 相似文献
52.
53.
Role of endothelial nitric oxide synthase in endothelial activation: insights from eNOS knockout endothelial cells 总被引:3,自引:0,他引:3
Kuhlencordt PJ Rosel E Gerszten RE Morales-Ruiz M Dombkowski D Atkinson WJ Han F Preffer F Rosenzweig A Sessa WC Gimbrone MA Ertl G Huang PL 《American journal of physiology. Cell physiology》2004,286(5):C1195-C1202
The objective of this study was to determine whether absence of endothelial nitric oxide synthase (eNOS) affects the expression of cell surface adhesion molecules in endothelial cells. Murine lung endothelial cells (MLECs) were prepared by immunomagnetic bead selection from wild-type and eNOS knockout mice. Wild-type cells expressed eNOS, but eNOS knockout cells did not. Expression of neuronal NOS and inducible NOS was not detectable in cells of either genotype. Upon stimulation, confluent wild-type MLECs produced significant amounts of NO compared with N-monomethyl-L-arginine-treated wild-type cells. eNOS knockout and wild-type cells showed no difference in the expression of E-selectin, P-selectin, intracellular adhesion molecule-1, and vascular cell adhesion molecule-1 as measured by flow cytometry on the surface of platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31)-positive cells. Both eNOS knockout and wild-type cells displayed the characteristics of resting endothelium. Adhesion studies in a parallel plate laminar flow chamber showed no difference in leukocyte-endothelial cell interactions between the two genotypes. Cytokine treatment induced endothelial cell adhesion molecule expression and increased leukocyte-endothelial cell interactions in both genotypes. We conclude that in resting murine endothelial cells, absence of endothelial production of NO by itself does not initiate endothelial cell activation or promote leukocyte-endothelial cell interactions. We propose that eNOS derived NO does not chronically suppress endothelial cell activation in an autocrine fashion but serves to counterbalance signals that mediate activation. vascular biology; atherosclerosis; mouse models 相似文献
54.
Olivera-Martinez I Viallet JP Michon F Pearton DJ Dhouailly D 《The International journal of developmental biology》2004,48(2-3):107-115
Skin morphogenesis occurs following a continuous series of cell-cell interactions which can be subdivided into three main stages: 1- the formation of a dense dermis and its overlying epidermis in the future appendage fields (macropattern); 2- the organization of these primary homogeneous fields into heterogeneous ones by the appearance of cutaneous appendage primordia (micropattern) and 3- cutaneous appendage organogenesis itself. In this review, we will first show, by synthesizing novel and previously published data from our laboratory, how heterogenetic and heterospecific dermal/epidermal recombinations have allowed us to distinguish between the respective roles of the dermis and the epidermis. We will then summarize what is known from the work of many different research groups about the molecular signaling which mediates these interactions in order to introduce the following articles of this Special Issue and to highlight what remains to done. 相似文献
55.
Renault J Bernard A Brajeul S Verhaeghe P Butt S Fabis F Dauphin F Uriac P Rault S 《Journal of enzyme inhibition and medicinal chemistry》2004,19(6):577-583
A series of N-omega-aminoalkyl- or N-omega-amidinoalkyl-2,4,6-triisopropyl benzenesulfonamides has been synthesized and their respective affinity indices on 5-HT6 receptor determined. This evaluation clearly showed that the compounds possessing an arylpiperazine moiety or an amidine function exhibited good affinity for the model. 相似文献
56.
Terradot L Durnell N Li M Li M Ory J Labigne A Legrain P Colland F Waksman G 《Molecular & cellular proteomics : MCP》2004,3(8):809-819
We have investigated a large set of interactions from the Helicobacter pylori protein interaction map previously identified by high-throughput yeast two-hybrid (htY2H)-based methods. This study had two aims: i) to validate htY2H as a source of protein-protein interaction complexes for high-throughput biochemical and structural studies of the H. pylori interactome; and ii) to validate biochemically interactions shown by htY2H to involve components of the H. pylori type IV secretion systems. Thus, 17 interactions involving 31 proteins and protein fragments were studied, and a general strategy was designed to produce protein-interacting partners for biochemical and structural characterization. We show that htY2H is a valid source of protein-protein complexes for high-throughput proteome-scale characterization of the H. pylori interactome, because 76% of the interactions tested were confirmed biochemically. Of the interactions involving type IV secretion proteins, three could be confirmed. One interaction is between two components of the type IV secretion apparatus, ComB10 and ComB4, which are VirB10 and VirB4 homologs, respectively. Another interaction is between a type IV component (HP0525, a VirB11 homolog) and a non-type IV secretion protein (HP01451), indicating that proteins other than the core VirB (1-11)-VirD4 proteins may play a role in type IV secretion. Finally, a third interaction was biochemically confirmed between CagA, a virulence factor secreted by the type IV secretion system encoded by the Cag pathogenicity island, and a non-type IV secretion protein, HP0496. 相似文献
57.
Austerlitz F Dick CW Dutech C Klein EK Oddou-Muratorio S Smouse PE Sork VL 《Molecular ecology》2004,13(4):937-954
Pollen dispersal is a critical process that shapes genetic diversity in natural populations of plants. Estimating the pollen dispersal curve can provide insight into the evolutionary dynamics of populations and is essential background for making predictions about changes induced by perturbations. Specifically, we would like to know whether the dispersal curve is exponential, thin-tailed (decreasing faster than exponential), or fat-tailed (decreasing slower than the exponential). In the latter case, rare events of long-distance dispersal will be much more likely. Here we generalize the previously developed TWOGENER method, assuming that the pollen dispersal curve belongs to particular one- or two-parameter families of dispersal curves and estimating simultaneously the parameters of the dispersal curve and the effective density of reproducing individuals in the population. We tested this method on simulated data, using an exponential power distribution, under thin-tailed, exponential and fat-tailed conditions. We find that even if our estimates show some bias and large mean squared error (MSE), we are able to estimate correctly the general trend of the curve - thin-tailed or fat-tailed - and the effective density. Moreover, the mean distance of dispersal can be correctly estimated with low bias and MSE, even if another family of dispersal curve is used for the estimation. Finally, we consider three case studies based on forest tree species. We find that dispersal is fat-tailed in all cases, and that the effective density estimated by our model is below the measured density in two of the cases. This latter result may reflect the difficulty of estimating two parameters, or it may be a biological consequence of variance in reproductive success of males in the population. Both the simulated and empirical findings demonstrate the strong potential of TWOGENER for evaluating the shape of the dispersal curve and the effective density of the population (d(e)). 相似文献
58.
It has been reported that auxin induces an epinastic growth response in plant leaf tissues. Leaf strips of tobacco (Nicotiana tabacum L. 'Bright Yellow 2') were used to study the effects of indole-3-acetic acid (IAA), the principal form of auxin in higher plants, and a synthetic auxin, 2,4-dichlorophenoxyacetic acid (2,4-D), on epinastic leaf curvature. Incubation of leaf strips with 10 micro M IAA resulted in a marked epinastic curvature response. Unexpectedly, 2,4-D showed only a weak IAA-like activity in inducing epinasty. Interestingly, the presence of 2,4-D resulted in inhibition of the IAA-dependent epinastic curvature. In vivo Lineweaver-Burk kinetic analysis clearly indicated that the interaction between IAA and 2,4-D reported here is not a result of competitive inhibition. Using kinetic analysis, it was not possible to determine whether the mode of interaction between IAA and 2,4-D was non-competitive or uncompetitive. 2,4-D inhibits the IAA-dependent epinasty via complex and as yet unidentified mechanisms. 相似文献
59.
El-Sayed NM Ghedin E Song J MacLeod A Bringaud F Larkin C Wanless D Peterson J Hou L Taylor S Tweedie A Biteau N Khalak HG Lin X Mason T Hannick L Caler E Blandin G Bartholomeu D Simpson AJ Kaul S Zhao H Pai G Van Aken S Utterback T Haas B Koo HL Umayam L Suh B Gerrard C Leech V Qi R Zhou S Schwartz D Feldblyum T Salzberg S Tait A Turner CM Ullu E White O Melville S Adams MD Fraser CM Donelson JE 《Nucleic acids research》2003,31(16):4856-4863
60.
The wood anatomy of 16 of the 37 genera within the epacrids (Styphelioideae, Ericaceae s.l.) is investigated by light and scanning electron microscopy. Several features in the secondary xylem occur consistently at the tribal level: arrangement of vessel-ray pits, distribution of axial parenchyma, ray width, and the presence and location of crystals. The primitive nature of Prionoteae and Archerieae is supported by the presence of scalariform perforation plates with many bars and scalariform to opposite vessel pitting. The wood structure of Oligarrheneae is similar to that of Styphelieae, but the very narrow vessel elements, exclusively uniseriate rays and the lack of prismatic crystals in Oligarrheneae distinguish these two tribes. The secondary xylem of Monotoca tamariscina indicates that it does not fit in Styphelieae; a position within Oligarrheneae is possible. Like most Cosmelieae, all Richeeae are characterized by exclusively scalariform perforation plates with many bars, a very high vessel density and paratracheal parenchyma, although they clearly differ in ray width (exclusively uniseriate rays in Cosmelieae vs. uniseriate and wide multiseriate rays in Richeeae). Several wood anatomical features confirm the inclusion of epacrids in Ericaceae s.l. Furthermore, there are significant ecological implications. The small vessel diameter and high vessel frequency in many epacrids are indicative of a high conductive safety to avoid embolism caused by freeze-thaw cycles, while the replacement of scalariform by simple vessel perforation plates and an increase in vessel diameter would suggest an increased conductive efficiency, which is especially found in mesic temperate or tropical Styphelieae. 相似文献