全文获取类型
收费全文 | 12175篇 |
免费 | 933篇 |
国内免费 | 4篇 |
专业分类
13112篇 |
出版年
2023年 | 66篇 |
2022年 | 144篇 |
2021年 | 312篇 |
2020年 | 189篇 |
2019年 | 228篇 |
2018年 | 377篇 |
2017年 | 301篇 |
2016年 | 422篇 |
2015年 | 642篇 |
2014年 | 719篇 |
2013年 | 895篇 |
2012年 | 1033篇 |
2011年 | 974篇 |
2010年 | 600篇 |
2009年 | 517篇 |
2008年 | 714篇 |
2007年 | 618篇 |
2006年 | 627篇 |
2005年 | 553篇 |
2004年 | 454篇 |
2003年 | 450篇 |
2002年 | 450篇 |
2001年 | 162篇 |
2000年 | 154篇 |
1999年 | 141篇 |
1998年 | 142篇 |
1997年 | 108篇 |
1996年 | 90篇 |
1995年 | 70篇 |
1994年 | 76篇 |
1993年 | 59篇 |
1992年 | 96篇 |
1991年 | 74篇 |
1990年 | 80篇 |
1989年 | 57篇 |
1988年 | 55篇 |
1987年 | 44篇 |
1986年 | 31篇 |
1985年 | 47篇 |
1984年 | 27篇 |
1983年 | 39篇 |
1982年 | 42篇 |
1981年 | 32篇 |
1980年 | 20篇 |
1979年 | 29篇 |
1977年 | 21篇 |
1976年 | 15篇 |
1975年 | 13篇 |
1973年 | 11篇 |
1968年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Production of moss‐dominated biocrusts to enhance the stability and function of the margins of artificial water bodies 下载免费PDF全文
Ricardo Cruz de Carvalho Patrícia dos Santos Cristina Branquinho 《Restoration Ecology》2018,26(3):419-421
Margins of water reservoirs associated with dams can have high‐frequency tides, promoting soil erosion and nutrient leaching. We propose the use of biocrusts for restoration and ecological engineering purposes, due to their poikilohydric character, to stabilize reservoir margins. We promoted biocrust growth under controlled conditions, testing two types of substrate: native sand and organic substrate. After 2 months, biocrusts grew on organic substrate covering almost all the area, but not on native sand. This fast and easy nature‐based solution for soil stabilization can be used as an environmental engineering tool in highly degraded sites. 相似文献
102.
103.
A comparative analysis of microscopic alterations in modern and ancient undecalcified and decalcified dry bones 下载免费PDF全文
104.
Ana B. Fagundo Susana Jiménez-Murcia Cristina Giner-Bartolomé Mohammed Anisul Islam Rafael de la Torre Antoni Pastor Felipe F. Casanueva Ana B. Crujeiras Roser Granero Rosa Ba?os Cristina Botella Jose M. Fernández-Real Gema Frühbeck Javier Gómez-Ambrosi José M. Menchón Francisco J. Tinahones Fernando Fernández-Aranda 《PloS one》2015,10(6)
The prefrontal (PFC) and orbitofrontal cortex (OFC) appear to be associated with both executive functions and olfaction. However, there is little data relating olfactory processing and executive functions in humans. The present study aimed at exploring the role of olfaction on executive functioning, making a distinction between primary and more cognitive aspects of olfaction. Three executive tasks of similar difficulty were used. One was used to assess hot executive functions (Iowa Gambling Task-IGT), and two as a measure of cold executive functioning (Stroop Colour and Word Test-SCWT and Wisconsin Card Sorting Test-WCST). Sixty two healthy participants were included: 31 with normosmia and 31 with hyposmia. Olfactory abilities were assessed using the ‘‘Sniffin’ Sticks’’ test and the olfactory threshold, odour discrimination and odour identification measures were obtained. All participants were female, aged between 18 and 60. Results showed that participants with hyposmia displayed worse performance in decision making (IGT; Cohen’s-d = 0.91) and cognitive flexibility (WCST; Cohen’s-d between 0.54 and 0.68) compared to those with normosmia. Multiple regression adjusted by the covariates participants’ age and education level showed a positive association between odour identification and the cognitive inhibition response (SCWT-interference; Beta = 0.29; p = .034). The odour discrimination capacity was not a predictor of the cognitive executive performance. Our results suggest that both hot and cold executive functions seem to be associated with higher-order olfactory functioning in humans. These results robustly support the hypothesis that olfaction and executive measures have a common neural substrate in PFC and OFC, and suggest that olfaction might be a reliable cognitive marker in psychiatric and neurologic disorders. 相似文献
105.
Ingelman-Sundberg M Rodriguez-Antona C 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2005,360(1460):1563-1570
The majority of phase I- and phase II-dependent drug metabolism is carried out by polymorphic enzymes which can cause abolished, quantitatively or qualitatively decreased or enhanced drug metabolism. Several examples exist where subjects carrying certain alleles do not benefit from drug therapy due to ultrarapid metabolism caused by multiple genes or by induction of gene expression or, alternatively, suffer from adverse effects of the drug treatment due to the presence of defective alleles. It is likely that future predictive genotyping for such enzymes might benefit 15-25% of drug treatments, and thereby allow prevention of adverse drug reactions and causalities, and thus improve the health of a significant fraction of the patients. However, it will take time before this will be a reality within the clinic. We describe some important aspects in the field with emphasis on cytochrome P450 and discuss also polymorphic aspects of foetal expression of CYP3A5 and CYP3A7. 相似文献
106.
Nardelli B Zaritskaya L Semenuk M Cho YH LaFleur DW Shah D Ullrich S Girolomoni G Albanesi C Moore PA 《Journal of immunology (Baltimore, Md. : 1950)》2002,169(9):4822-4830
IFN-kappa is a recently identified type I IFN that exhibits both structural and functional homology with the other type I IFN subclasses. In this study, we have investigated the effect of IFN-kappa on cells of the innate immune system by comparing cytokine release following treatment of human cells with either IFN-kappa or two recombinant IFN subtypes, IFN-beta and IFN-alpha2a. Although IFN-alpha2a failed to stimulate monocyte cytokine secretion, IFN-kappa, like IFN-beta, induced the release of several cytokines from both monocytes and dendritic cells, without the requirement of a costimulatory signal. IFN-kappa was particularly effective in inhibiting inducible IL-12 release from monocytes. Unlike IFN-beta, IFN-kappa did not induce release of IFN-gamma by PBL. Expression of the IFN-kappa mRNA was observed in resting dendritic cells and monocytes, and it was up-regulated by IFN-gamma stimulation in monocytes, while IFN-beta mRNA was minimally detectable under the same conditions. Monocyte and dendritic cell expression of IFN-kappa was also confirmed in vivo in chronic lesions of psoriasis vulgaris and atopic dermatitis. Finally, biosensor-based binding kinetic analysis revealed that IFN-kappa, like IFN-beta, binds strongly to heparin (K(d): 2.1 nM), suggesting that the cytokine can be retained close to the local site of production. The pattern of cytokines induced by IFN-kappa in monocytes, coupled with the unique induction of IFN-kappa mRNA by IFN-gamma, indicates a potential role for IFN-kappa in the regulation of immune cell functions. 相似文献
107.
Airoldi C Zona C Sironi E Colombo L Messa M Aurilia D Gregori M Masserini M Salmona M Nicotra F La Ferla B 《Journal of biotechnology》2010,156(4):317-324
Curcumin derivatives with high chemical stability, improved solubility and carrying a functionalized appendage for the linkage to other entities, have been synthesized in a straightforward manner. All compounds retained Curcumin ability to bind Aβ peptide oligomers without inducing their aggregation. Moreover all Curcumin derivatives were able to stain very efficiently Aβ deposits. 相似文献
108.
Juliana Stein Silvina C. Pessino Eric J. Martínez María Pía Rodriguez Lorena A. Siena Camilo L. Quarin Juan Pablo Amelio Ortiz 《Molecular breeding : new strategies in plant improvement》2007,20(2):153-166
Paspalum notatum Flügge is a warm-season forage grass with mainly diploid (2n = 20) and autotetraploid (2n = 40) representatives. Diploid
races reproduce sexually and require crosspollination due to a self-incompatible mating system, while autotetraploids reproduce
by aposporous apomixis. The objectives of this work were to develop a genetic linkage map of Paspalum notatum Flügge at the tetraploid level, identify the linkage/s group/s associated with apomixis and carry out a general characterization
of its mode of inheritance. A pseudo test-cross F1 family of 113 individuals segregating for the mode of reproduction was obtained by crossing a synthetic completely sexual
tetraploid plant (Q4188) as female parent with a natural aposporous individual (Q4117) as pollen donor. Map construction was
based on single-dose markers (SDAFs) segregating from both parents. Two linkage maps (female and male) were constructed. Within
each map, homologous groups were assembled by detecting repulsion-phase linked SDAFs. Putative Q4188 and Q4117 homolog groups
were identified by mapping shared single dose markers (BSDF). The Q4188 map consisted of 263 markers distributed on 26 co-segregation
groups over a total genetic distance of 1.590.6 cM, while the Q4117 map contained 216 loci dispersed on 39 co-segregation
groups along 2.265.7 cM, giving an estimated genome coverage of 88% and 83%, respectively. Seven and 12 putative homologous
chromosomes were detected within Q4188 and Q4117 maps, respectively. Afterward, ten female and male homologous chromosomes
were identified by mapping BSDFs. In the Q4117 map, a single linkage group was associated with apospory. It was characterized
by restriction in recombination and preferential chromosome pairing. A BPSD marker mapping within this group allowed the detection
of the female homolog and the putative four male groups of the set carrying apospory. 相似文献
109.
Vijayachandran LS Viola C Garzoni F Trowitzsch S Bieniossek C Chaillet M Schaffitzel C Busso D Romier C Poterszman A Richmond TJ Berger I 《Journal of structural biology》2011,175(2):198-208
Multiprotein complexes catalyze vital biological functions in the cell. A paramount objective of the SPINE2 project was to address the structural molecular biology of these multiprotein complexes, by enlisting and developing enabling technologies for their study. An emerging key prerequisite for studying complex biological specimens is their recombinant overproduction. Novel reagents and streamlined protocols for rapidly assembling co-expression constructs for this purpose have been designed and validated. The high-throughput pipeline implemented at IGBMC Strasbourg and the ACEMBL platform at the EMBL Grenoble utilize recombinant overexpression systems for heterologous expression of proteins and their complexes. Extension of the ACEMBL platform technology to include eukaryotic hosts such as insect and mammalian cells has been achieved. Efficient production of large multicomponent protein complexes for structural studies using the baculovirus/insect cell system can be hampered by a stoichiometric imbalance of the subunits produced. A polyprotein strategy has been developed to overcome this bottleneck and has been successfully implemented in our MultiBac baculovirus expression system for producing multiprotein complexes. 相似文献
110.