首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1881篇
  免费   148篇
  国内免费   2篇
  2024年   6篇
  2023年   13篇
  2022年   36篇
  2021年   87篇
  2020年   44篇
  2019年   46篇
  2018年   50篇
  2017年   57篇
  2016年   87篇
  2015年   125篇
  2014年   119篇
  2013年   110篇
  2012年   138篇
  2011年   134篇
  2010年   93篇
  2009年   75篇
  2008年   77篇
  2007年   85篇
  2006年   53篇
  2005年   73篇
  2004年   55篇
  2003年   51篇
  2002年   44篇
  2001年   30篇
  2000年   31篇
  1999年   28篇
  1998年   18篇
  1997年   13篇
  1996年   14篇
  1995年   11篇
  1994年   11篇
  1993年   13篇
  1992年   22篇
  1991年   12篇
  1990年   13篇
  1989年   9篇
  1988年   10篇
  1987年   9篇
  1986年   15篇
  1985年   7篇
  1984年   7篇
  1983年   6篇
  1981年   6篇
  1980年   5篇
  1977年   5篇
  1974年   4篇
  1973年   9篇
  1935年   3篇
  1925年   3篇
  1923年   3篇
排序方式: 共有2031条查询结果,搜索用时 31 毫秒
141.
Journal of Plant Growth Regulation - It is a well-established fact that nitric oxide (NO) is a multifaceted signaling molecule, which plays diverse role in organisms. In the past two decades,...  相似文献   
142.
We evaluated the effects of Leishmania spp infection on several population parameters of Lutzomyia longipalpis sensu lato andLutzomyia pseudolongipalpis, vectors of visceral leishmaniasis in Venezuela, under experimental conditions during the first post-feeding period. Females of both species were allowed to feed and engorge on a suspension of fresh washed human red blood cells in foetal calf serum. These blood cells were either non-infected or infected with one of the fourLeishmania spp strains and were offered through a chicken skin membrane. The longevity, life expectancy and the fecundity of uninfected flies were similar in both species, but the fertility was significantly lower in uninfected Lu. longipalpis females. In all cases, the infection of Lu. longipalpis and Lu. pseudolongipalpis by the Leishmania strains resulted in significant detrimental effects, which exerted a fitness cost expressed by reduced survival and life expectancy, as well as decreased fertility and fecundity compared with the control groups. Nevertheless, differences in these parameters were observed between these vector species depending on whether they were infected with the autochthonous Venezuelan Leishmania infantum strain (NESA) or the Brazilian reference strain (PP75). The experimental data obtained agree with field data on the natural infection of these vector species and the significance of this scenario is discussed.  相似文献   
143.
144.
145.
The concept of positional information is central to our understanding of how cells determine their location in a multicellular structure and thereby their developmental fates. Nevertheless, positional information has neither been defined mathematically nor quantified in a principled way. Here we provide an information-theoretic definition in the context of developmental gene expression patterns and examine the features of expression patterns that affect positional information quantitatively. We connect positional information with the concept of positional error and develop tools to directly measure information and error from experimental data. We illustrate our framework for the case of gap gene expression patterns in the early Drosophila embryo and show how information that is distributed among only four genes is sufficient to determine developmental fates with nearly single-cell resolution. Our approach can be generalized to a variety of different model systems; procedures and examples are discussed in detail.  相似文献   
146.
Kiss1, a neuropeptide predominantly expressed in the habenula, modulates the serotonin (5‐HT) system to decrease odorant cue [alarm substance (AS)]‐evoked fear behaviour in the zebrafish. The purpose of this study was to assess the interaction of Kiss1 with the 5‐HT system as well as to determine the involvement of the 5‐HT receptor subtypes in AS‐evoked fear. We utilized 0. 28 mg/kg WAY 100635 (WAY), a selective 5‐HT1A receptor antagonist, to observe the effects of Kiss1 administration on AS‐evoked fear. We found WAY significantly inhibited the anxiolytic effects of Kiss1 (< 0.001) with an exception of freezing behaviour. Based on this, we utilized 92.79 mg/kg methysergide, a 5‐HT1 and 5‐HT2 receptor antagonist, and found that methysergide significantly blocked the anxiolytic effects of Kiss1 in the presence of the AS (< 0.001). From this, we conclude that Kiss1 modulates AS‐evoked fear responses mediated by the 5‐HT1A and 5‐HT2 receptors.

  相似文献   

147.
The nephroprotective effect of coenzyme Q10 and epigallocatechin gallate was investigated in rats with acute renal injury induced by a single nephrotoxic dose of cisplatin. Two days prior to cisplatin administration, epigallocatechin gallate and coenzyme Q10 alone and in four different combinations were given for 6 days. The treatment with antioxidants significantly protected the cisplatin‐induced increase in the levels of blood urea nitrogen and serum creatinine. Both the antioxidants alone or in different combinations significantly compensated the increased malondialdehyde and reduced glutathione levels. Moreover, the decrease in the activities of superoxide dismutase, catalase, and glutathione peroxidase and the concentration of selenium, zinc, and copper ions were significantly attenuated in renal tissue. In conclusion, epigallocatechin gallate and coenzyme Q10 are equally effective against cisplatin‐induced nephrotoxicity, whereas the intervention by combining these two antioxidants was found to be highly effective at low doses in attenuating oxidative stress in rat kidney.  相似文献   
148.
Resistance to broad-spectrum beta-lactams, mediated by extended-spectrum beta-lactamase enzymes (ESBL), is an increasing problem worldwide. The present study was undertaken to determine the incidence of ESBL-production among the clinical isolates of Pseudomonas aeruginosa and their susceptibility to selected antimicrobials. A total of one eighty-seven clinical specimens were tested for the presence of ESBL production using the double-disc synergy test. Of these, 25.13% (n = 47) isolates of P. aeruginosa were observed as ESBL positive. The maximum number of ESBL-producing strains were found in sputum (41.67%; n = 24) followed by pus (28.36%; n = 19), cerebrospinal fluid and other body fluids (21.74%; n = 5), urine (20.45%; n = 9) and blood (13.79%; n = 4). ESBL producing isolates exhibited co-resistance to an array of antibiotics tested. Imipenem and meropenem can be suggested as the drugs of choice in our study.  相似文献   
149.
150.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号