全文获取类型
收费全文 | 18550篇 |
免费 | 1440篇 |
国内免费 | 8篇 |
出版年
2023年 | 97篇 |
2022年 | 251篇 |
2021年 | 476篇 |
2020年 | 259篇 |
2019年 | 337篇 |
2018年 | 475篇 |
2017年 | 416篇 |
2016年 | 667篇 |
2015年 | 965篇 |
2014年 | 1074篇 |
2013年 | 1268篇 |
2012年 | 1614篇 |
2011年 | 1595篇 |
2010年 | 1001篇 |
2009年 | 753篇 |
2008年 | 1169篇 |
2007年 | 1040篇 |
2006年 | 996篇 |
2005年 | 965篇 |
2004年 | 843篇 |
2003年 | 729篇 |
2002年 | 701篇 |
2001年 | 199篇 |
2000年 | 161篇 |
1999年 | 183篇 |
1998年 | 158篇 |
1997年 | 101篇 |
1996年 | 95篇 |
1995年 | 79篇 |
1994年 | 70篇 |
1993年 | 79篇 |
1992年 | 98篇 |
1991年 | 70篇 |
1990年 | 92篇 |
1989年 | 79篇 |
1988年 | 63篇 |
1987年 | 57篇 |
1986年 | 51篇 |
1985年 | 47篇 |
1984年 | 48篇 |
1983年 | 34篇 |
1982年 | 37篇 |
1981年 | 27篇 |
1980年 | 29篇 |
1979年 | 34篇 |
1978年 | 26篇 |
1975年 | 28篇 |
1974年 | 27篇 |
1969年 | 31篇 |
1968年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 33 毫秒
31.
Michelle de C. S. Azevedo Patricia S. Rosa Cleverson T. Soares Luciana R. V. Fachin Ida Maria F. D. Baptista William J. Woods Gustavo P. Garlet Ana Paula F. Trombone Andrea de F. F. Belone 《PloS one》2015,10(12)
Jorge Lobo’s disease (JLD) is a chronic infection that affects the skin and subcutaneous tissues. Its etiologic agent is the fungus Lacazia loboi. Lesions are classified as localized, multifocal, or disseminated, depending on their location. Early diagnosis and the surgical removal of lesions are the best therapeutic options currently available for JLD. The few studies that evaluate the immunological response of JLD patients show a predominance of Th2 response, as well as a high frequency of TGF-β and IL-10 positive cells in the lesions; however, the overall immunological status of the lesions in terms of their T cell phenotype has yet to be determined. Therefore, the objective of this study was to evaluate the pattern of Th1, Th2, Th17 and regulatory T cell (Treg) markers mRNA in JLD patients by means of real-time PCR. Biopsies of JLD lesions (N = 102) were classified according to their clinical and histopathological features and then analyzed using real-time PCR in order to determine the expression levels of TGF-β1, FoxP3, CTLA4, IKZF2, IL-10, T-bet, IFN-γ, GATA3, IL-4, IL-5, IL-13, IL-33, RORC, IL-17A, IL-17F, and IL-22 and to compare these levels to those of healthy control skin (N = 12). The results showed an increased expression of FoxP3, CTLA4, TGF-β1, IL-10, T-bet, IL-17F, and IL-17A in lesions, while GATA3 and IL-4 levels were found to be lower in diseased skin than in the control group. When the clinical forms were compared, TGF-β1 was found to be highly expressed in patients with a single localized lesion while IL-5 and IL-17A levels were higher in patients with multiple/disseminated lesions. These results demonstrate the occurrence of mixed T helper responses and suggest the dominance of regulatory T cell activity, which could inhibit Th-dependent protective responses to intracellular fungi such as L. loboi. Therefore, Tregs may play a key role in JLD pathogenesis. 相似文献
32.
Susan J. Harrison-Uy Julie A. Siegenthaler Andrea Faedo John L. R. Rubenstein Samuel J. Pleasure 《PloS one》2013,8(3)
We examined the role of the orphan nuclear hormone receptor CoupTFI in mediating cortical development downstream of meningeal retinoic acid signaling. CoupTFI is a regulator of cortical development known to collaborate with retinoic acid (RA) signaling in other systems. To examine the interaction of CoupTFI and cortical RA signaling we utilized Foxc1-mutant mice in which defects in meningeal development lead to alterations in cortical development due to a reduction of RA signaling. By analyzing CoupTFI−/−;Foxc1H/L double mutant mice we provide evidence that CoupTFI is required for RA rescue of the ventricular zone and the neurogenic phenotypes in Foxc1-mutants. We also found that overexpression of CoupTFI in Foxc1-mutants is sufficient to rescue the Foxc1-mutant cortical phenotype in part. These results suggest that CoupTFI collaborates with RA signaling to regulate both cortical ventricular zone progenitor cell behavior and cortical neurogenesis. 相似文献
33.
Elia Pintus Silvia Sorbolini Andrea Albera Giustino Gaspa Corrado Dimauro Roberto Steri Gabriele Marras Nicolò P. P. Macciotta 《Animal genetics》2014,45(1):1-11
Selection is the major force affecting local levels of genetic variation in species. The availability of dense marker maps offers new opportunities for a detailed understanding of genetic diversity distribution across the animal genome. Over the last 50 years, cattle breeds have been subjected to intense artificial selection. Consequently, regions controlling traits of economic importance are expected to exhibit selection signatures. The fixation index (Fst) is an estimate of population differentiation, based on genetic polymorphism data, and it is calculated using the relationship between inbreeding and heterozygosity. In the present study, locally weighted scatterplot smoothing (LOWESS) regression and a control chart approach were used to investigate selection signatures in two cattle breeds with different production aptitudes (dairy and beef). Fst was calculated for 42 514 SNP marker loci distributed across the genome in 749 Italian Brown and 364 Piedmontese bulls. The statistical significance of Fst values was assessed using a control chart. The LOWESS technique was efficient in removing noise from the raw data and was able to highlight selection signatures in chromosomes known to harbour genes affecting dairy and beef traits. Examples include the peaks detected for BTA2 in the region where the myostatin gene is located and for BTA6 in the region harbouring the ABCG2 locus. Moreover, several loci not previously reported in cattle studies were detected. 相似文献
34.
35.
36.
Uta Kühne Branka Filjak Hans Kröger 《Biochimica et Biophysica Acta (BBA)/General Subjects》1975,399(1):42-49
An injection of cortisone acetate at a dose of 5 mg/100 g body weight concomitant with dibutryl cyclic AMP prevents the increase in the activity of rat liver cytosol serine aminotransferase (L-serine: pyruvate aminotransferase, EC 2.6.1.51) elicited by the nucleotide with a lag of about 2 h. If the glucocorticoid is given 2 h prior to the nucleotide inducer, the lag disappears. The inhibitory effect of cortisone acetate gradually decays and is no longer detectable 12 h following its administration. Theophylline, insulin and glucose at doses which affect significantly the level of tyrosine aminotransferase, have no effect on the level of serine aminotransferase and on the cortisone inhibition. The inhibitory effect of the glucocorticoid on the dibutyryl cyclic AMP-mediated increase in serine aminotransferase diminishes with the age of animals. Increase in the enzyme activity by a single dose of glucagon can also be inhibited by cortisone acetate and actinomycin D as in the case with dibutyrl cyclic AMP as an inducer. The possibility of the existence of a specific inhibitory factor which is formed in response to cortisone acetate is discussed. 相似文献
37.
Oligonucleotides containing 8-aza-7-deaza-2'-deoxyisoguanosine (4) were investigated regarding their self-assembly in aqueous solution. The aggregation of 4 was compared with that of oligonucleotides containing 2'-deoxyisoguanosine (2b) and 2'-deoxyguanosine (1b). For this purpose the phosphoramidite of 4 was synthesized which was protected by a dibutylaminomethylidene residue at the amino group and a diphenylcarbamoyl residue at the 2-oxo function. Solid-phase synthesis furnished oligonucleotide containing short runs of the nucleoside 4. The self-assembly of the oligonucleotide 5'-d(T(4)4(4)T2) was studied by ion-exchange chromatography. The formation of a pentaplex was observed in the presence of Cs+, while a tetraplex is formed when the counter ion is Na+ or Rb+. The cation selectivity of the oligonucleotide 5'-d(T(4)4(4)T2) was found to be different from the parent 5'-d(T(4)isoG(4)T2) which was forming the tetraplex as well as a pentaplex in aq RbCl solution. 相似文献
38.
Andrea Schrödel 《当今生物学》2007,37(5):289-289
39.
40.
Construction of chlorobenzene-utilizing recombinants by progenitive manifestation of a rare event 总被引:10,自引:0,他引:10
Separate continuous cultures of Pseudomonas putida R5-3, grown on toluene, and Pseudomonas alcaligenes C-O, grown on benzoate, were concentrated and continuously amalgamated on a ceramic bead column, which was subjected to a continuous stream of chlorobenzene vapors. A recombinant strain, P. putida CB1-9, was isolated in less than 1 month. P. alcaligenes C-0 grew on benzoate and 3-chlorobenzoate but not on toluene, P. putida R5-3 grew on benzoate and toluene but not on 3-chlorobenzoate, and neither strain grew on chlorobenzene or 1,4-dichlorobenzene; however, the recombinant P. putida CB1-9 grew on all of these substrates. Chlorobenzene-utilizing strains were not found in continuous cultures run at the lowest growth rate (0.05/h) or in the absence of the donor strain, P. alcaligenes C-0. Chloride was released in stoichiometric amounts when P. putida CB1-9 was grown on either chlorobenzene or 1,4-dichlorobenzene. The recombinant strain was related to P. putida R5-3, phenotypically and genetically. Restriction enzyme digests of the single 57-kilobase (kb) plasmid in R5-3 and of the single 33-kb plasmid in CB1-9 were similar, but also indicated rearrangement of plasmid DNA. Coincidental or causal to the loss of the 24-kb fragment was the observation that the recombinant--unlike its parent, R5-3--did not grow on xylenes or methylbenzoates. Although both ortho-pyrocatechase (OP) and meta-pyrocatechase (MP) were found in CB1-9 and R5-3, MP activity was 20- to 50-fold higher in R5-3 cells grown on 4-methylbenzoate than in the same cells grown on benzene.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献