全文获取类型
收费全文 | 418篇 |
免费 | 34篇 |
专业分类
452篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 17篇 |
2013年 | 20篇 |
2012年 | 25篇 |
2011年 | 25篇 |
2010年 | 27篇 |
2009年 | 23篇 |
2008年 | 34篇 |
2007年 | 34篇 |
2006年 | 25篇 |
2005年 | 21篇 |
2004年 | 30篇 |
2003年 | 23篇 |
2002年 | 22篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1974年 | 5篇 |
排序方式: 共有452条查询结果,搜索用时 15 毫秒
101.
The effects of trees and contamination on microbial metabolic activity, especially that of hydrocarbon degrading bacteria, were compared during phytoremediation to find which conditions increase diesel fuel removal. Diesel fuel utilisation, microbial extracellular enzyme activities and utilisation of Biolog ECO plate carbon sources by soil bacteria were determined during phytoremediation experiments consisting of two separate diesel applications. Diesel fuel removal after 28 days of second diesel application was 20–30% more than after the first application 1 year earlier. Soil microbiota utilised 26–31 of the 31 Biolog ECO plate carbon sources. Carbon source utilisation profiles indicated minor differences in microbiota in soil vegetated with pine compared to microbiota in soil vegetated with poplar. The potential maximum rates of aminopeptidase activity were 10–102
M AMC/h/g dry soil prior to and after second diesel application, except 14days after the second diesel addition, where the rates were at the scale of 103M AMC/h/g dry soil. The potential maximum rates of esterase activity were 103–104M MUF/h/g dry soil. The presence of plants did not influence the activity of esterases. The utilisation of diesel by soil bacteria in Biolog MT2 plate assay was higher in contaminated soil, especially when vegetated, than in uncontaminated soil, measured both as lag times and maximum specific utilisation rates. MT2 plate assay detected the biological response after diesel fuel addition better than general activity methods. 相似文献
102.
Background
Diagnosing depression in chronic pain is challenging due to overlapping somatic symptoms. In questionnaires, such as the Beck Depression Inventory (BDI), responses may be influenced more by pain than by the severity of depression. In addition, previous studies have suggested that symptoms of negative self-image, a key element in depression, are uncommon in chronic pain-related depression. The object of this study is to assess the relationship of the somatic and cognitive-emotional items of BDI with the diagnosis of depression, pain intensity, and disability.Methods
One hundred consecutive chronic pain patients completed the Structured Clinical Interview for DSM Disorders (SCID) for the diagnosis of major depressive disorder (MDD) according to DSM-IV. Two subscales of BDI (negative view of self and somatic-physical function) were created according to the factor model presented by Morley.Results
In the regression analysis, the somatic-physical function factor associated with MDD, while the negative view of self factor did not. Patients with MDD had higher scores in several of the BDI items when analysed separately. Insomnia and weight loss were not dependent on the depression diagnosis.Limitations
The relatively small sample size and the selected patient sample limit the generalisability of the results.Conclusions
Somatic symptoms of depression are also common in chronic pain and should not be excluded when diagnosing depression in pain patients. Regardless of the assessment method, diagnosing depression in chronic pain remains a challenge and requires careful interpretation of symptoms. 相似文献103.
104.
Alun Evans G Caroline M Van Baal Peter McCarron Marlies DeLange Thorkild I Soerensen Eco J C De Geus Kirsten Kyvik Nancy L Pedersen Tim D Spector Toby Andrew Christopher Patterson John B Whitfield Gu Zhu Nicholas G Martin Jaakko Kaprio Dorret I Boomsma 《Twin research》2003,6(5):432-441
Despite the decline in coronary heart disease in many European countries, the disease remains an enormous public health problem. Although we know a great deal about environmental risk factors for coronary heart disease, a heritable component was recognized a long time ago. The earliest and best known examples of how our genetic constitution may determine cardiovascular risk relate to lipoprotein(a), familial hypercholesterolaemia and apolipoprotein E. In the past 20 years a fair number of polymorphisms assessed singly have shown strong associations with the disease but most are subject to poor repeatability. Twins constitute a compelling natural experiment to establish the genetic contribution to coronary heart disease and its risk factors. GenomEUtwin, a recently funded Framework 5 Programme of the European Community, affords the opportunity of comparing the heritability of risk factors in different European Twin Registries. As an illustration we present the heritabilities of systolic and diastolic blood pressure, based on data from over 4000 twin pairs from six different European countries and Australia. Heritabilities for systolic blood pressure are between 52 and 66% and for diastolic blood pressure between 44 and 66%. There is no evidence of sex differences in heritability estimates and very little to no evidence for a significant contribution of shared family environment. A non-twin based prospective case/cohort study of coronary heart disease and stroke (MORGAM) will allow hypotheses relating to cardiovascular disease, generated in the twin cohorts, to be tested prospectively in adult populations. Twin studies have also contributed to our understanding of the life course hypothesis, and GenomEUtwin has the potential to add to this. 相似文献
105.
Genome Scan for Predisposing Loci for Distal Interphalangeal Joint Osteoarthritis: Evidence for a Locus on 2q 总被引:12,自引:0,他引:12 下载免费PDF全文
Jenni Lepp?vuori Urho Kujala Jaakko Kinnunen Jaakko Kaprio Martti Nissil? Markku Heli?vaara Nina Klinger Jukka Partanen Joseph D. Terwilliger Leena Peltonen 《American journal of human genetics》1999,65(4):1060-1067
The genetic contribution to common forms of osteoarthritis (OA) is well established but poorly understood. We performed a genome scan, using 302 markers for loci predisposing to distal interphalangeal joint (DIP) OA. To minimize genetic heterogeneity in our study sample, we identified siblings with a severe, radiologically defined phenotype from the nationwide registers of Finland. In the initial genome scan, linkage analysis in 27 sibships gave a pairwise LOD score (Z) >1.00 with nine of the screening markers. In the second stage, additional markers and family members were genotyped in these chromosomal regions. On 2q12-q13, IL1R1 resulted in Z=2.34 at recombination fraction (theta) 0, allowing a dominant mode of inheritance. Association analysis of markers D2S2264, IL1R1, D2S373, and D2S1789 jointly provided some evidence for a shared haplotype among the affected individuals (P value of.012). Also, multipoint nonparametric linkage analysis yielded a P value of.0001 near the locus IL1R1 and P=.0007 approximately 20 cM telomeric near marker D2S1399, which, in two-point analysis, gave Z=1.48 (straight theta=. 02). This chromosomal region on 2q harbors the interleukin 1 gene cluster and, thus, represents a good candidate region for inflammatory and autoimmune disorders. Three additional chromosomal regions-4q26-q27, 7p15-p21, and Xcen-also provided some evidence for linkage, and further analyses would be justified to clarify their potential involvement in the genetic predisposition to DIP OA. 相似文献
106.
Genetic and environmental influences on the relationship between aggression and hyperactivity-impulsivity as rated by teachers and parents. 总被引:1,自引:0,他引:1
This study examined genetic and environmental contributions to the covariance between aggression and hyperactivity-impulsivity as rated by twins' teachers and parents. Sex-differences in these genetic and environmental contributions and rater bias/sibling interaction effects were of interest as well. Part of an ongoing nation-wide twin-family study of behavioral development and health habits, the sample consisted of 1636 Finnish twin pairs ascertained from five consecutive and complete twin birth cohorts. Data were collected at ages 11-12, using teacher and parental rating forms of the Multidimensional Peer Nomination Inventory. Bivariate analyses were performed using structural equation modeling allowing sex-limitation effects. Results show that, in addition to significant genetic and environmental influences specific to each behavior, aggression and hyperactivity-impulsivity share common genetic and environmental etiology. Results provide evidence that both genetic and environmental factors are important in creating the observed correlation between aggression and hyperactivity-impulsivity. 相似文献
107.
Peltola M Kanto Oqvist C Ekman J Kosonen M Jokela S Kolari M Korhonen P Salkinoja-Salonen M 《Journal of industrial microbiology & biotechnology》2008,35(12):1651-1657
Deinococcus geothermalis has frequently been isolated from pink colored deposits of paper industry processes. Laboratory studies have shown that D. geothermalis is capable of forming on nonliving surfaces patchy biofilms that are resistant to adverse agents such as extreme pH, desiccation,
solubilising detergents and biocides. This study was done to quantitatively assess the role of D. geothermalis as a biofouler in paper industry. Colored deposits were collected from 24 European and North American paper and board machines
and the densities of the bacterial 16S rRNA genes and those of the red slime producers D. geothermalis and Meiothermus spp. were measured by QPCR (quantitative real time PCR). D. geothermalis was found at nine machines, usually from splash area deposits, but its contribution was minor, 0.001–1%, to the total bacterial
burden of 8.3 to log 10.5 log units per gram wet-weight of the deposits. When D. geothermalis was found in a measurable quantity, Meiothermus spp. also was found, often in bulk quantity (7–100% of the total bacteria). The data are in line with the properties of D. geothermalis known from laboratory biofilm studies, indicating this species is a pioneer coloniser of machine surfaces and may help other
bacteria to adhere and grown into biofilms, rather than competing with them. 相似文献
108.
We have used genotypic variation in birch (Betula pendula Roth) to investigate the roles of ozone (O(3))-induced ethylene (ET), jasmonic acid, and salicylic acid in the regulation of tissue tolerance to O(3). Of these hormones, ET evolution correlated best with O(3)-induced cell death. Disruption of ET perception by transformation of birch with the dominant negative mutant allele etr1-1 of the Arabidopsis ET receptor gene ETR1 or blocking of ET perception with 1-methylcyclopropene reduced but did not completely prevent the O(3)-induced cell death, when inhibition of ET biosynthesis with aminooxyacetic acid completely abolished O(3) lesion formation. This suggests the presence of an ET-signaling-independent but ET biosynthesis-dependent component in the ET-mediated stimulation of cell death in O(3)-exposed birch. Functional ET signaling was required for the O(3) induction of the gene encoding beta-cyanoalanine synthase, which catalyzes detoxification of the cyanide formed during ET biosynthesis. The results suggest that functional ET signaling is required to protect birch from the O(3)-induced cell death and that a decrease in ET sensitivity together with a simultaneous, high ET biosynthesis can potentially cause cell death through a deficient detoxification of cyanide. 相似文献
109.
Bark beetle diversity at different spatial scales 总被引:3,自引:1,他引:2
To determine how the scale of observation affects ecological patterns we studied bark beetle (Coleoptera, Scolytidae) diversity in southern Finland. A block covering 160 × 160 m of a forest was delimited in four stands of different site types. Each block was divided into 256 squares (10 × 10 m) in which the occurrence of bark beetle species was recorded. In addition, environmental variables describing site type, trees, and breeding material appropriate for bark beetles were measured. The species presence/absence data were combined at different scales of resolution (10 × 10 m. 20 × 20 m, 40 × 40 m, 80 × 80 m, 160 × 160 m). At the finest scale a recently thinned pine stand showed relatively high diversity compared to other study stands due to a few evenly distributed and abundant species. However, the species diversity increased faster toward larger scales in mature spruce stands with several sporadically distributed species. According to logistic regression analyses, breeding material and site characteristics explained the occurrence of most beetle species. However, these variables did not explain the occurrence of the six most frequent species, probably because the factors regulating their distribution and occurrence operate at larger scales. 相似文献
110.
Jorma J. Ohisalo Ilmo E. Hassinen Jaakko P. Pispa 《Biochimica et Biophysica Acta (BBA)/General Subjects》1974,362(1):48-52
Hepatic tyrosine aminotransferase (l-tyrosine:2-oxoglutarate aminotransferase, EC 2.6.1.5) is known to be induced by α-methyl-p-tyrosine, a well-known catecholamine depletor, in both intact and adrenalectomized rats. The authors have studied this subject further and their results show that α-methyl-p-tyrosine does not influence the activity of tyrosine aminotransferase in the isolated, perfused liver and that hypophysectomy totally abolishes the induction of the enzyme by this agent. The involvement of hypophyseal hormones is discussed. 相似文献