全文获取类型
收费全文 | 4096篇 |
免费 | 382篇 |
国内免费 | 1篇 |
专业分类
4479篇 |
出版年
2023年 | 22篇 |
2022年 | 65篇 |
2021年 | 115篇 |
2020年 | 46篇 |
2019年 | 75篇 |
2018年 | 110篇 |
2017年 | 80篇 |
2016年 | 142篇 |
2015年 | 240篇 |
2014年 | 267篇 |
2013年 | 266篇 |
2012年 | 364篇 |
2011年 | 296篇 |
2010年 | 204篇 |
2009年 | 159篇 |
2008年 | 184篇 |
2007年 | 196篇 |
2006年 | 182篇 |
2005年 | 154篇 |
2004年 | 130篇 |
2003年 | 130篇 |
2002年 | 110篇 |
2001年 | 69篇 |
2000年 | 68篇 |
1999年 | 59篇 |
1998年 | 30篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 22篇 |
1992年 | 39篇 |
1991年 | 29篇 |
1990年 | 30篇 |
1989年 | 30篇 |
1988年 | 27篇 |
1987年 | 27篇 |
1986年 | 28篇 |
1985年 | 25篇 |
1984年 | 26篇 |
1983年 | 22篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1979年 | 27篇 |
1977年 | 17篇 |
1976年 | 27篇 |
1975年 | 17篇 |
1974年 | 27篇 |
1973年 | 19篇 |
1972年 | 16篇 |
1971年 | 20篇 |
1970年 | 18篇 |
排序方式: 共有4479条查询结果,搜索用时 14 毫秒
131.
Elie Fux Claire Marcaillou Florence Mondeguer Ronel Bire Philipp Hess 《Harmful algae》2008,7(5):574-583
It has been demonstrated that polymeric resins can be used as receiving phase in passive samplers designed for the detection of lipophilic marine toxins at sea and was referred to as solid phase adsorption toxin tracking (SPATT). The present study describes the uptake and desorption behaviour of the lipophilic marine toxins okadaic acid (OA) and dinophysistoxin-1 (DTX1) from Prorocentrum lima cultures by five styrene—divinylbenzene based polymeric resins Sepabeads® SP850, Sepabeads® SP825L, Amberlite® XAD4, Dowex® Optipore® L-493 and Diaion® HP-20. All resins accumulated OA and DTX1 from the P. lima culture with differences in adsorption rate and equilibrium rate. Following statistical evaluation, HP-20, SP850 and SP825L demonstrated similar adsorption rates. However, possibly due to its larger pore size, the HP-20 did not seem to reach equilibrium within 72 h exposure as opposed to the SP850 and SP825L. This was confirmed when the resins were immersed at sea for 1 week on the West Coast of Ireland. Furthermore, this work also presents a simple and efficient extraction method suitable to SPATT samplers exposed to artificial or natural culture media. 相似文献
132.
Fink B Grammer K Mitteroecker P Gunz P Schaefer K Bookstein FL Manning JT 《Proceedings. Biological sciences / The Royal Society》2005,272(1576):1995-2001
The average human male face differs from the average female face in size and shape of the jaws, cheek-bones, lips, eyes and nose. It is possible that this dimorphism is determined by sex steroids such as testosterone (T) and oestrogen (E), and several studies on the perception of such characteristics have been based on this assumption, but those studies focussed mainly on the relationship of male faces with circulating hormone levels; the corresponding biology of the female face remains mainly speculative. This paper is concerned with the relative importance of prenatal T and E levels (assessed via the 2D : 4D finger length ratio, a proxy for the ratio of T/E) and sex in the determination of facial form as characterized by 64 landmark points on facial photographs of 106 Austrians of college age. We found that (i) prenatal sex steroid ratios (in terms of 2D : 4D) and actual chromosomal sex dimorphism operate differently on faces, (ii) 2D : 4D affects male and female face shape by similar patterns, but (iii) is three times more intense in men than in women. There was no evidence that these effects were confounded by allometry or facial asymmetry. Our results suggest that studies on the perception of facial characteristics need to consider differential effects of prenatal hormone exposure and actual chromosomal gender in order to understand how characteristics have come to be rated 'masculine' or 'feminine' and the consequences of these perceptions in terms of mate preferences. 相似文献
133.
Jürgen Glas Julia Seiderer Melinda Nagy Christoph Fries Florian Beigel Maria Weidinger Simone Pfennig Wolfram Klein J?rg T. Epplen Peter Lohse Matthias Folwaczny Burkhard G?ke Thomas Ochsenkühn Julia Diegelmann Bertram Müller-Myhsok Darina Roeske Stephan Brand 《PloS one》2010,5(4)
Background
Recent studies demonstrated an association of STAT4 variants with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), indicating that multiple autoimmune diseases share common susceptibility genes. We therefore investigated the influence of STAT4 variants on the susceptibility and phenotype of inflammatory bowel diseases (IBD) in a large patient and control cohort.Methodology/Principal Findings
Genomic DNA from 2704 individuals of Caucasian origin including 857 patients with Crohn''s disease (CD), 464 patients with ulcerative colitis (UC), and 1383 healthy, unrelated controls was analyzed for seven SNPs in the STAT4 gene (rs11889341, rs7574865, rs7568275, rs8179673, rs10181656, rs7582694, rs10174238). In addition, a detailed genotype-phenotype analysis was performed. Our analysis revealed an association of the STAT4 SNP rs7574865 with overall decreased susceptibility to CD (p = 0.047, OR 0.86 [95% CI 0.74–0.99]). However, compared to CD patients carrying the wild type genotype, the STAT4 SNP rs7574865 was significantly associated with early CD onset (p = 0.021) and colonic CD (p = 0.008; OR = 4.60, 95% CI 1.63–12.96). For two other STAT4 variants, there was a trend towards protection against CD susceptibility (rs7568275, p = 0.058, OR 0.86 [95% CI 0.74–1.00]; rs10174238, p = 0.057, OR 0.86 [95% CI 0.75–1.00]). In contrast, we did not observe any association with UC susceptibility. Evidence for weak gene-gene interaction of STAT4 with the IL23R SNP rs11209026 was lost after Bonferroni correction.Conclusions/Significance
Our results identified the STAT4 SNP rs7574865 as a disease-modifying gene variant in colonic CD. However, in contrast to SLE and RA, the effect of rs7574865 on CD susceptibility is only weak. 相似文献134.
Carrot (Daucus carota L.) cell suspension cultures grew well when provided with glucose, fructose, sucrose or raffinose. Galactose and melibiose supported less growth unless supplemented with glucose or fructose. In combination with ten different sugar mixtures, 2-deoxy-D-glucose (dGlc) inhibited culture growth. Inhibitory effects of dGlc were more marked with fructose, melibiose, raffinose or mixtures of these sugars in the culture medium. The presence of glucose or galactose reduced the inhibitory effects of dGlc on culture growth. Experiments with radioactive labelled sugars demonstrated that dGLc uptake was greater in the presence of fructose than glucose, and that growth inhibition of dGlc coincided with its uptake. Reduced protein content was also associated with the inhibitory effects of dGlc. Cultured cells contained lower levels of invertase (EC 3.2.1.26) activity during the active phase of culture growth (up to 25 days after subculture) than when growth had peaked and subsequently declined. Acid and alkaline invertase activities were not greatly reduced by exogenous hexoses. Invertase activity was greatest during periods of low protein content in all cultures and was inhibited by dGlc during the latter phases of the culture period. Free intracellular sugars throughout the culture period consisted mainly of glucose and fructose. 相似文献
135.
The antifungal drug amphotericin B promotes inflammatory cytokine release by a Toll-like receptor- and CD14-dependent mechanism 总被引:5,自引:0,他引:5
Sau K Mambula SS Latz E Henneke P Golenbock DT Levitz SM 《The Journal of biological chemistry》2003,278(39):37561-37568
Amphotericin B is the most effective drug for treating many life-threatening fungal infections. Amphotericin B administration is limited by infusion-related toxicity, including fever and chills, an effect postulated to result from proinflammatory cytokine production by innate immune cells. Because amphotericin B is a microbial product, we hypothesized that it stimulates immune cells via Toll-like receptors (TLRs) and CD14. We show here that amphotericin B induces signal transduction and inflammatory cytokine release from cells expressing TLR2 and CD14. Primary murine macrophages and human cell lines expressing TLR2, CD14, and the adapter protein MyD88 responded to amphotericin B with NF-kappaB-dependent reporter activity and cytokine release, whereas cells deficient in any of these failed to respond. Cells mutated in TLR4 were less responsive to amphotericin B stimulation than cells expressing normal TLR4. These data demonstrate that TLR2 and CD14 are required for amphotericin B-dependent inflammatory stimulation of innate immune cells and that TLR4 may also provide stimulation of these cells. Our results provide a putative molecular basis for inflammatory responses elicited by amphotericin B and suggest strategies to eliminate the acute toxicity of this drug. 相似文献
136.
Anne-Christin St?whas Tsogyal D. Latshang Christian M. Lo Cascio Sina Lautwein Katrin Stadelmann Noemi Tesler Lisa Ayers Kaspar Berneis Philipp A. Gerber Reto Huber Peter Achermann Konrad E. Bloch Malcolm Kohler 《PloS one》2013,8(8)
Background
Travel to mountain areas is popular. However, the effects of acute exposure to moderate altitude on the cardiovascular system and metabolism are largely unknown.Objectives
To investigate the effects of acute exposure to moderate altitude on vascular function, metabolism and systemic inflammation.Methods
In 51 healthy male subjects with a mean (SD) age of 26.9 (9.3) years, oxygen saturation, blood pressure, heart rate, arterial stiffness, lipid profiles, low density lipoprotein (LDL) particle size, insulin resistance (HOMA-index), highly-sensitive C-reactive protein and pro-inflammatory cytokines were measured at 490 m (Zurich) and during two days at 2590 m, (Davos Jakobshorn, Switzerland) in randomized order. The largest differences in outcomes between the two altitudes are reported.Results
Mean (SD) oxygen saturation was significantly lower at 2590 m, 91.0 (2.0)%, compared to 490 m, 96.0 (1.0)%, p<0.001. Mean blood pressure (mean difference +4.8 mmHg, p<0.001) and heart rate (mean difference +3.3 bpm, p<0.001) were significantly higher at 2590 m, compared to 490 m, but this was not associated with increased arterial stiffness. At 2590 m, lipid profiles improved (median difference triglycerides −0.14 mmol/l, p = 0.012, HDL +0.08 mmol/l, p<0.001, total cholesterol/HDL-ratio −0.25, p = 0.001), LDL particle size increased (median difference +0.45 nm, p = 0.048) and hsCRP decreased (median difference −0.18 mg/l, p = 0.024) compared to 490 m. No significant change in pro-inflammatory cytokines or insulin resistance was observed upon ascent to 2590 m.Conclusions
Short-term stay at moderate altitude is associated with increased blood pressure and heart rate likely due to augmented sympathetic activity. Exposure to moderate altitude improves the lipid profile and systemic inflammation, but seems to have no significant effect on glucose metabolism.Trial Registration
ClinicalTrials.gov NCT01130948相似文献137.
138.
Jan-Wolfhard Kellmann Tatjana Kleinow Kerstin Engelhardt Christina Philipp Dorothee Wegener Jeff Schell Peter H. Schreier 《Plant molecular biology》1996,30(2):351-358
Two different genes encoding class II chitinases from peanut (Arachis hypogaea L. cv. NC4), A.h.Chi2;1 and A.h.Chi2;2, have been cloned. In peanut cell suspension cultures, mRNA levels of A.h.Chi2;2 increased after ethylene or salicylate treatment and in the presence of conidia from Botrytis cinerea. The second gene, A.h.Chi2;1, was only expressed after treatment with the fungal spores. Transgenic tobacco plants containing the complete peanut A.h.Chi2;1 gene exhibited essentially the same expression pattern in leaves as observed in peanut cell cultures. Expression characteristics of transgenic tobacco carrying a promoter-GUS fusion of A.h.Chi2;1 are described. 相似文献
139.
Walter K. F. Seelentag Ursula Günthert Parvin Saremaslani Eva Futo Madeleine Pfaltz Philipp U. Heitz Jürgen Roth 《Histochemistry and cell biology》1996,106(3):283-289
CD44 isoforms have been implicated in tumor progression and metastasis formation. This study presents a thorough immunohistochemical
analysis of CD44 standard and isoform expression in normal human skin appendages and epidermis applying monoclonal antibodies
against CD44s, CD44v3, -v4, -v5, -v6, and -v9. An improved immunohistochemical protocol with microwave-based antigen retrieval
in paraffin sections and heavy metal amplification of the diaminobenzidine reaction product provided enhanced resolution and
sensitivity as compared to studies on frozen sections. The hair follicle, the seborrheic and eccrine sweat glands were strongly
positive for all CD44 isoforms studied. In the latter, the clear cells but not the dark (intercalated) cells were positive.
The sudoriferous ducts adjacent to the glands were weakly positive for all CD44 isoforms and strongly positive near the skin
surface. In the apocrine glands, the basal cells showed only a moderate positivity. The myoepithelial cells expressed only
CD44s. In the epidermis, all CD44 isoforms were detectable, with strongest CD44 immunostaining in the lower third of the stratum
spinosum and weaker staining in the stratum basale and the upper two-thirds of the stratum granulosum. The stratum granulosum
and corneum were unreactive. Thus, a regional and cell type-specific CD44 expression was revealed.
Accepted: 10 May 1996 相似文献
140.
Martha P. Brown Dimitri Toptygin K. B. Lee Theresa Animashaun R. C. Hughes Y. C. Lee Ludwig Brand 《Journal of Protein Chemistry》1998,17(2):149-159
The plant lectin Tetracarbidium conophorum agglutinin II binds to glycoproteins and glycopeptides in a structurally specific manner [Animashaun et al., (1994) Glycoconjugate J.
11, 299–303]. We have characterized the steady-state and time-resolved fluorescence of the tryptophan residues of this lectin. The fluorescence (ex = 295 nm, em = 350 nm) decay is complex and can be described by four decay times with the following values: 1 = 7.4nsec, 1 = 0.22; 2 = 2.9 nsec, 2 = 0.25; 3 = l.0 nsec, 3 = 0.34; 4 = 0.2 nsec, 4 = 0.18. The addition of a biantennary glycopeptide
to the lectin results in a quench and an 8 nm blue shift of the emission spectrum. The effect is saturable, and is described by an association constant of 1.8×105 M–1. The tryptophan fluorescence of Tetracarbidium conophorum agglutinin II may therefore be utilized to characterize thermodynamically the binding interactions between this lectin and complex glycoprotein. 相似文献