全文获取类型
收费全文 | 21921篇 |
免费 | 1498篇 |
国内免费 | 9篇 |
专业分类
23428篇 |
出版年
2024年 | 19篇 |
2023年 | 126篇 |
2022年 | 311篇 |
2021年 | 580篇 |
2020年 | 351篇 |
2019年 | 470篇 |
2018年 | 593篇 |
2017年 | 478篇 |
2016年 | 809篇 |
2015年 | 1215篇 |
2014年 | 1343篇 |
2013年 | 1659篇 |
2012年 | 1948篇 |
2011年 | 1892篇 |
2010年 | 1174篇 |
2009年 | 1016篇 |
2008年 | 1376篇 |
2007年 | 1287篇 |
2006年 | 1179篇 |
2005年 | 1081篇 |
2004年 | 981篇 |
2003年 | 927篇 |
2002年 | 751篇 |
2001年 | 117篇 |
2000年 | 106篇 |
1999年 | 135篇 |
1998年 | 125篇 |
1997年 | 115篇 |
1996年 | 89篇 |
1995年 | 86篇 |
1994年 | 90篇 |
1993年 | 88篇 |
1992年 | 53篇 |
1991年 | 58篇 |
1990年 | 62篇 |
1989年 | 45篇 |
1988年 | 50篇 |
1987年 | 38篇 |
1986年 | 42篇 |
1985年 | 51篇 |
1984年 | 39篇 |
1983年 | 44篇 |
1982年 | 32篇 |
1981年 | 42篇 |
1980年 | 26篇 |
1979年 | 34篇 |
1978年 | 32篇 |
1977年 | 29篇 |
1976年 | 25篇 |
1975年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Sensitive and specific detection of microRNAs by northern blot analysis using LNA-modified oligonucleotide probes 总被引:13,自引:5,他引:8
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Válóczi A Hornyik C Varga N Burgyán J Kauppinen S Havelda Z 《Nucleic acids research》2004,32(22):e175
We describe here a new method for highly efficient detection of microRNAs by northern blot analysis using LNA (locked nucleic acid)-modified oligonucleotides. In order to exploit the improved hybridization properties of LNA with their target RNA molecules, we designed several LNA-modified oligonucleotide probes for detection of different microRNAs in animals and plants. By modifying DNA oligonucleotides with LNAs using a design, in which every third nucleotide position was substituted by LNA, we could use the probes in northern blot analysis employing standard end-labelling techniques and hybridization conditions. The sensitivity in detecting mature microRNAs by northern blots was increased by at least 10-fold compared to DNA probes, while simultaneously being highly specific, as demonstrated by the use of different single and double mismatched LNA probes. Besides being highly efficient as northern probes, the same LNA-modified oligonucleotide probes would also be useful for miRNA in situ hybridization and miRNA expression profiling by LNA oligonucleotide microarrays. 相似文献
992.
993.
Dancsházy Z Dér A Groma GI Janka Z Járdánházy T Makai A Szentistványi I Vasadi A 《Chronobiology international》2004,21(2):309-314
The aim of the study was to determine any alteration of the 24 h motor activity pattern of a bipolar patient in different mood states. Actigraphic records were collected on an outpatient basis for a total of 387 days. The daily actograms were synchronized in phase to the time of morning awakening before averaging, which significantly enhanced the structure of the averaged traces. The actograms were divided into three groups based on total daily count. The daily motor activity patterns of the low- and high-activity days have a different circadian pattern. We propose it may have a relevance to the different mood states. The phase-synchronization of the 24 h actograms to the patient's sleep-wake cycle, specifically to the time of awaking from the nighttime sleep, may help reveal differences in the daily temporal patterns of motor activity. 相似文献
994.
Holeva MC Bell KS Hyman LJ Avrova AO Whisson SC Birch PR Toth IK 《Molecular plant-microbe interactions : MPMI》2004,17(9):943-950
Soft rot Erwinia spp., like other closely related plant pathogens, possess a type III secretion system (TTSS) (encoded by the hrp gene cluster) implicated in disease development. We report the sequence of the entire hrp gene cluster and adjacent dsp genes in Erwinia carotovora subsp. atroseptica SCRI1039. The cluster is similar in content and structural organization to that in E. amylovora. However, eight putative genes of unknown function located within the E. carotovora subsp. atroseptica cluster do not have homologues in the E. amylovora cluster. An arrayed set of Tn5 insertional mutants (mutation grid) was constructed and pooled to allow rapid isolation of mutants for any given gene by polymerase chain reaction screening. This novel approach was used to obtain mutations in two structural genes (hrcC and hrcV), the effector gene dspE/A, and the helper gene hrpN. An improved pathogenicity assay revealed that these mutations led to significantly reduced virulence, showing that both the putative E. carotovora subsp. atroseptica TTSS-delivered effector and helper proteins are required for potato infection. 相似文献
995.
Zarnowski R Jaromin A Certik M Czabany T Fontaine J Jakubik T Iqbal MC Grandmougin-Ferjani A Kozubek A Pietr SJ 《Zeitschrift für Naturforschung. C, Journal of biosciences》2004,59(5-6):321-326
The oil of Adenanthera pavonina L. seeds was analysed by chromatographic and instrumental means. The oil was found to be rich in neutral lipids (86.2%), and low in polar lipids (13.8%). The neutral lipids consisted mainly of triacylglycerols (64.2%). Unsaturated fatty acids were found as high as 71%, while the percentage of saturated fatty acids was only 29%. GC and GC/MS analyses revealed linoleic, oleic and lignocerotic acid to be predominant among all fatty acids in the A. pavonina oil, whereas stigmasterol was the major steroid identified within this study. Subsequently, the oil was used for preparation of submicron oil-in-water (o/w) lipid emulsions. Lipid emulsions were formulated by using soybean lecithin (SL) to investigate their particle size, Zeta potential and stability at the different oil and SL ratios. The results obtained indicate possible applications of the tested oil in pharmaceutical and medical fields as drug and cosmetic active ingredient carriers. 相似文献
996.
Anna?LewandowskaEmail author Zenon?Foltynowicz 《The International Journal of Life Cycle Assessment》2004,9(3):180-186
Goal, Scope and Background This paper is the second part of the publication which is devoted to comparative LCA analysis of the industrial pumps. The
previous paper deals with the methodological aspects concerning quality assessment and forms an independent work. This paper
uses practically only the methodological suggestions made there. The main aim of the presented study is to make a comparison
between the industrial pumps which are based on two different technologies. The Life Cycle Assessment method is used to check
whether the differences of the manufacturing processes influence the level of the potential environmental impact during the
whole life cycle of the analysed products.
Methods The Life Cycle Assessment is carried out using the Ecoindicator99 method. Additionally, an extensive quality analysis of the
LCA study is made (Part I). To make the process of an identification of the data easier and faster, they are assigned to a
special data documentation form. To ensure the credibility of the LCA results different methods of interpretation are used.
Results and Discussion The LCA analysis shows clear superiority of the pumps manufactured using modern technology. It seems that this superiority
results not only from the differences in the emissions, but also from different characteristics of effectiveness in the usage
stage. Thanks to the uncertainty analysis, each LCA result is provided with the range of uncertainty.
Conclusions The LCA results are supported by different techniques of interpretation: the sensitivity-, the contribution-, the comparative-,
the discernability- and the uncertainty analysis. There is strong evidence of the superiority of the pumps based on the modern
technology.
Recommendations and Outlook The main source of the environmental impact in the case of pumps is the usage stage and the consumption of energy. That is
why it should be the main area to improve. The LCA results show that actions taken in the usage stage and energy consumption
can lead to a considerable reduction of the environmental impacts. 相似文献
997.
998.
999.
Pseudomonas syringae pv. tomato DC3000 causes bacterial speck disease in tomato, and it elicits the hypersensitive response (HR) in non-host plants such as Nicotiana tabacum and Nicotiana benthamiana. The compatible and incompatible interactions of DC3000 with tomato and Nicotiana spp., respectively, result in plant cell death, but the HR cell death occurs more rapidly and is associated with effective plant defense. Both interactions require the Hrp (HR and pathogenicity) type III secretion system (TTSS), which injects Hop (Hrp outer protein) effectors into plant cells. Here, we demonstrate that HopPtoN is translocated into tomato cells via the Hrp TTSS. A hopPtoN mutant produced eightfold more necrotic 'speck' lesions on tomato leaves than did DC3000, but the mutant and the wild-type strain grew to the same level in infected leaves. In non-host N. tabacum leaves, the hopPtoN mutant produced more cell death, whereas a DC3000 strain overexpressing HopPtoN produced less cell death and associated electrolyte leakage in comparison with wild-type DC3000. Transient expression of HopPtoN via infection with a PVX viral vector enabled tomato and N. benthamiana plants to tolerate, with reduced disease lesions, challenge infections with DC3000 and P. syringae pv. tabaci 11528, respectively. HopPtoN showed cysteine protease activity in vitro, and hopPtoN mutants altered in the predicted cysteine protease catalytic triad (C172S, H283A and D299A) lost HR suppression activity. These observations reveal that HopPtoN is a TTSS effector that can suppress plant cell death events in both compatible and incompatible interactions. 相似文献
1000.
Katzburg S Hendel D Waisman A Posner GH Kaye AM Somjen D 《The Journal of steroid biochemistry and molecular biology》2004,88(2):213-219
Pretreatment with 1 nM 1,25-dihydroxyvitamin D(3) (1,25), or non-hypercalcemic Vitamin D analogs, upregulated the response of creatine kinase (CK) to 17beta-estradiol (30 nM E(2)), raloxifene (3000 nM RAL) or dihydrotestosterone (300 nM DHT) in primary human bone cells. Previously, we reported that these osteoblast-like cells responded to gonadal steroids in a sex specific manner. Bone cells derived from pre-menopausal women showed greater stimulation of CK specific activity by E(2) than bone cells from post-menopausal women; in male-derived cells no age related difference was found. In this study, we treated cells derived from female or male bones, at different ages, with the side chain modified analogs of Vitamin D: CB 1093 (CB), EB 1089 (EB), MC 1288 (MC) and the demonstrably non-calcemic hybrid analog JK 1624 F2-2 (JKF), by daily addition of 1 nM, for 3 days. On day 4, cells were incubated with sex steroids for 4h and cell extracts were prepared. Pretreatment with JKF or CB significantly upregulated the response to 30 nM E(2) in all female-derived cells and to 300 nM DHT in mature male-derived cells. In cells from older males, only JKF caused augmentation of DHT action. Bone cells from pre- or post-menopausal females responded to 3000 nM RAL by increased CK activity to the same extent as to 30 nM E(2); however, RAL and E(2), when applied together, resulted in mutual annihilation of their agonist activities. Vitamin D analogs prevented the antagonistic effect of RAL in the presence of E(2), possibly due to increased numbers of ERs. Both estrogen receptors, alpha (ERalpha) and beta (ERbeta), were expressed in male- as well as in female-derived cells. However, only in female-derived cells were ERalpha and ERbeta upregulated by pretreatment with Vitamin D analogs. This study raises the possibility of testing combined Vitamin D analog and estrogen replacement treatment for post-menopausal women to prevent osteoporosis. 相似文献