全文获取类型
收费全文 | 1466篇 |
免费 | 112篇 |
国内免费 | 187篇 |
出版年
2024年 | 6篇 |
2023年 | 21篇 |
2022年 | 55篇 |
2021年 | 55篇 |
2020年 | 62篇 |
2019年 | 80篇 |
2018年 | 54篇 |
2017年 | 58篇 |
2016年 | 55篇 |
2015年 | 62篇 |
2014年 | 89篇 |
2013年 | 116篇 |
2012年 | 55篇 |
2011年 | 74篇 |
2010年 | 59篇 |
2009年 | 92篇 |
2008年 | 79篇 |
2007年 | 84篇 |
2006年 | 98篇 |
2005年 | 79篇 |
2004年 | 64篇 |
2003年 | 63篇 |
2002年 | 43篇 |
2001年 | 25篇 |
2000年 | 23篇 |
1999年 | 23篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1765条查询结果,搜索用时 218 毫秒
101.
db/db小鼠糖尿病肾病相关基因的分析和克隆 总被引:5,自引:0,他引:5
用GM-U74A基因芯片分别检测了正常对照组(db/m小鼠)、糖尿病肾病组(db/db小鼠)、大黄酸治疗组(大黄酸150 mg/kg治疗12周)肾脏基因表达谱.发现在12 437个基因(包括表达序列标签)中,与正常对照组相比,糖尿病肾病组有1 085个基因表达下调,37个基因表达上调,其中变化幅度大于2倍,表达下调的有166个和表达上调的有29个.与糖尿病肾病组相比,大黄酸治疗组有384个基因表达下调,155个表达上调,其中变化幅度大于2倍,表达下调的有47个和表达上调的有30个.在此基础上,对其中的一个差异表达的表达序列标签(EST)进行了详细的生物信息学分析,发现它是一个未知功能基因——“REKEN cDNA 0610006H10”基因的一部分.在用RT-PCR进一步验证了其与糖尿病肾病的相关性后,对“REKEN cDNA 0610006H10”基因进行了克隆. 相似文献
102.
Rose AD Woods MG Clement JG Thomas CD 《American journal of physical anthropology》2003,121(2):172-180
This study was designed to investigate the relationship between traditional skeletal cephalometric measurement and Fourier analysis of the lateral soft-tissue profile. A random sample of 121 untreated subjects of European descent, with wide ranges of malocclusions and underlying facial patterns, was selected in the Orthodontic Unit at the University of Melbourne. Lateral cephalograms were available for all subjects. Both traditional lateral cephalometric analysis and Fourier soft-tissue profile analysis were carried out. Multivariate statistical analysis among 11 hard-tissue cephalometric measurements and the first 50 Fourier harmonics was then performed. This analysis formed the basis for a subsequently proposed soft-tissue prediction model. From this model, 50 predicted x- and y-harmonics were generated for each subject in the total sample. Calculation of Pearson's correlation coefficients between the actual and predicted harmonics revealed strong relationships for many of the lower-order harmonics. To further test the model, the prediction-coefficients derived from all 121 subjects were then used to make predictions for the first 50 x- and y-harmonics for a subgroup of 10 independent test subjects. Once again, Pearson's correlations between the actual and predicted harmonics of the test model in the lower-order harmonics revealed strong associations. Superimposition of the actual and predicted soft-tissue outlines, however, revealed that much actual detail in the region between the nose and the chin was still lost using the predicted Fourier harmonics. This suggests that soft-tissue prediction based on this Fourier test model, while already useful in Forensic facial reconstruction, may not yet be appropriate for useful diagnosis and planning in clinical disciplines. 相似文献
103.
We predict a structure of the glutamine amidotransferase subunit (hisH) of imidazole glycerol phosphate synthase (IGPS) which catalyzes the fifth step of the histidine biosynthesis in Escherichia coli. The model is constructed using an energy-based threading program augmented by a multiple sequence to structure profile analysis. In developing our model we identified a conserved core region within hisH and a variable domain which is the likely site of interaction with the synthase subunit (hisF) of IGPS. Information available from structural and functional genomics studies was used to improve the structure prediction, to discuss parallels between histidine biosynthesis and other amino acid and nucleotide metabolic pathways, and to better understand the protein-protein interactions between the hisH and hisF domains of IGPS. This work allows us to develop a preliminary model for the structure of the entire IGPS holoenzyme. 相似文献
104.
105.
Analysis of far-red light-regulated genome expression profiles of phytochrome A pathway mutants in Arabidopsis 总被引:10,自引:0,他引:10
Wang H Ma L Habashi J Li J Zhao H Deng XW 《The Plant journal : for cell and molecular biology》2002,32(5):723-733
Phytochrome A (phyA) is the primary photoreceptor responsible for various far-red (FR) light-mediated responses. Previous studies have identified multiple phyA signaling mutants, including both positive and negative regulators of the phyA-mediated responses. How these defined intermediates act to mediate FR light responses is largely unknown. Here a cDNA microarray was used to examine effects of those mutations on the far-red light control of genome expression. Clustering analysis of the genome expression profiles supports the notion that phyA signaling may entail a network with multiple paths, controlling overlapping yet distinct sets of gene expression. FHY1, FAR1 and FHY3 most likely act upstream in the phyA signaling network, close to the phyA photoreceptor itself. FIN219, SPA1 and REP1 most likely act somewhere more downstream in the network and control the expression of smaller sets of genes. Further, this study also provides genomics evidence for the partial functional redundancy between FAR1 and FHY3. These two homologous proteins control the expression of a largely overlapping set of genes, and likely act closely together in the phyA-mediated FR light responses. 相似文献
106.
Sigrist CJ Cerutti L Hulo N Gattiker A Falquet L Pagni M Bairoch A Bucher P 《Briefings in bioinformatics》2002,3(3):265-274
Among the various databases dedicated to the identification of protein families and domains, PROSITE is the first one created and has continuously evolved since. PROSITE currently consists of a large collection of biologically meaningful motifs that are described as patterns or profiles, and linked to documentation briefly describing the protein family or domain they are designed to detect. The close relationship of PROSITE with the SWISS-PROT protein database allows the evaluation of the sensitivity and specificity of the PROSITE motifs and their periodic reviewing. In return, PROSITE is used to help annotate SWISS-PROT entries. The main characteristics and the techniques of family and domain identification used by PROSITE are reviewed in this paper. 相似文献
107.
Bernhard?Schlesier Frédéric?Bréton Hans-Peter?MockEmail author 《Plant Molecular Biology Reporter》2003,21(4):449-456
We developed a hydroponic cultivation system for growingArabidopsis plantlets under sterile, controlled environmental conditions. The system consists of a piece of stainless-steel wire cloth
(125 μm mesh size) that is fixed between 2 flat rings and held in place by 3 legs, placed in a commercially-available glass
jar, and covered by the original glass lid or a sheet of sterilized cellophane. Sterilized seeds were distributed evenly across
the mesh piece, the size of which allowed root growth and kept the seeds in place. After 3 weeks of cultivation, shoot and
root tissues were easily harvested without mechanical damage. Proteome and metabolite analyses were performed on root and
shoot tissues and demonstrated excellent reproducibility, indicating that the system is advantageous when biological variation
is minimized. Induction experiments can be performed by transferring the apparatus (with plants) to a new jar containing a
different nutrient solution. The apparatus is reusable and can easily be sterilized by autoclaving or dry heat. The system
can be adapted to other small-seed plants by varying the mesh size. 相似文献
108.
Ambrose L 《Primates; journal of primatology》2003,44(1):25-39
This study identifies populations currently classified as Allen's galago (Galago alleni) at ten locations in Gabon, Cameroon and Bioko Island. Morphological diversity was evident both within and between populations.
Attention to the loud calls revealed three distinct vocal profiles which are consistent within biogeographical regions. This
work is based on the Recognition Concept of Species which refers to a Specific Mate Recognition System. Galagos rely less
on visual signals than diurnal primates and recognise each other principally by means of auditory and olfactory signals. Galagos
possess repertoires of loud calls relating to contact and alarm which are thought to be species-specific. Other studies of
nocturnal prosimians (galagos, tarsiers) have demonstrated that the unique loud call repertoires are reliable indicators of
species boundaries; whereas characters such as body size and pelage coloration are highly variable, even within populations.
The vocal data in this study provide evidence of at least three acoustic forms of galago within the Allen's group which are
predicted to represent three distinct species: the Allen's form on Bioko Island and south-west Cameroon, the Gabon form in
southern Cameroon and northern Gabon and the Makandé form in Gabon south of the Ogooué river. Some populations may be vulnerable
to extinction due to limited distributions and habitat destruction.
Electronic Publication 相似文献
109.
110.
Jessica?Lagerstedtkth.se" title="jessica@md kth.se" itemprop="email" data-track="click" data-track-action="Email author" data-track-label="">Email author Conrad?Luttropp Lars-Gunnar?Lindfors 《The International Journal of Life Cycle Assessment》2003,8(3):160-166
Aim, Scope and Background The interest in environmental questions has increased enormously during the last decade. Environmental protection has become
an issue of strategic importance within the manufacturing industry and many companies are now working in the field of Design
for Environment (DFE). The main purpose of DFE is to create products and services for achieving a sustainable society. Designers
are widely believed to have a key role in adapting products to a sustainable society and one of the major instruments in the
context of Design for Environment is Life Cycle Assessment (LCA). However, product development creates particular challenges
for incorporating environmental issues that combine functional and environmental assessment. A natural and important part
of product design is to define and analyse the functions of the product. Consequently, the functional unit in LCA is a core
issue in DFE. Most recent research in DFE has focused on how to reduce the environmental impact of products throughout their
life-cycle by addressing environmental aspects, while little attention has been given to the functionality of the product.
Additionally, early product development phases, so called re-think phases, are considered to have the influence on major changes
in products in general. These phases have thus the highest potential for changing products and product systems towards a sustainable
development.
Main Features This paper discusses an extended functional representation in design for environment methods to evaluate sustainable design
solutions, especially in early (re-think) phases of product design. Based on engineering-design science and several case studies,
a concept has been developed describing how functional preferences can be visualised in design for environment and product
development. In addition, the functional unit in LCA is discussed. The concept is called Functional Profile (FP) and is additionally
exemplified in a case study on radio equipment.
Discussion The new functional characterisation concept helps identify functional priorities in design for environment. The Functional
Profile is a structured, systematic and creative concept for identifying the necessary functions of a new product. The FP
is envisioned to complement existing design for environment methods, not to replace them. Instead of being a product-development
tool or method, the concept is an approach that increases understanding of inter-reactions between functional characteristics
of products and their environmental characteristics, which furthermore facilitates trade-off decisions. One of the objectives
behind the concept is to highlight the importance of balancing functional requirements and environmental impacts, presenting
both the advantages and disadvantages of the product.
Outlook A second paper will be produced to complement the functional-environmental characterisation concept in early product development
phase, presenting the environmental characterisation part and illustrating correlations between the functional and environmental
sides. 相似文献