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   8520篇
  免费   603篇
  国内免费   1篇
  2023年   39篇
  2022年   90篇
  2021年   162篇
  2020年   109篇
  2019年   146篇
  2018年   221篇
  2017年   187篇
  2016年   260篇
  2015年   427篇
  2014年   487篇
  2013年   650篇
  2012年   727篇
  2011年   701篇
  2010年   429篇
  2009年   415篇
  2008年   547篇
  2007年   516篇
  2006年   505篇
  2005年   410篇
  2004年   428篇
  2003年   367篇
  2002年   367篇
  2001年   86篇
  2000年   74篇
  1999年   80篇
  1998年   70篇
  1997年   61篇
  1996年   46篇
  1995年   41篇
  1994年   32篇
  1993年   30篇
  1992年   44篇
  1991年   38篇
  1990年   39篇
  1989年   31篇
  1988年   31篇
  1987年   18篇
  1986年   18篇
  1985年   28篇
  1984年   23篇
  1983年   21篇
  1982年   17篇
  1981年   12篇
  1980年   7篇
  1979年   8篇
  1977年   12篇
  1974年   8篇
  1973年   9篇
  1968年   8篇
  1964年   5篇
排序方式: 共有9124条查询结果,搜索用时 15 毫秒
131.
Photosynthesis Research - The photosynthesis process is determined by the intensity level and spectral quality of the light; therefore, leaves need to adapt to a changing environment. The incident...  相似文献   
132.
Plant and Soil - The ecological study of root systems lags behind the understanding of the aboveground components of plant communities, mainly due to methodological challenges. As ecological root...  相似文献   
133.
134.
Molecular Biology Reports - Benign metastasizing leiomyoma (BML) is a rare disease characterized by extrauterine benign leiomyomatosis in patients with a previous or concomitant history of uterine...  相似文献   
135.
136.
137.
138.
Synaptic transmission is the key system for the information transfer and elaboration among neurons. Nevertheless, a synapse is not a standing alone structure but it is a part of a population of synapses inputting the information from several neurons on a specific area of the dendritic tree of a single neuron. This population consists of excitatory and inhibitory synapses the inputs of which drive the postsynaptic membrane potential in the depolarizing (excitatory synapses) or depolarizing (inhibitory synapses) direction modulating in such a way the postsynaptic membrane potential. The postsynaptic response of a single synapse depends on several biophysical factors the most important of which is the value of the membrane potential at which the response occurs. The concurrence in a specific time window of inputs by several synapses located in a specific area of the dendritic tree can, consequently, modulate the membrane potential such to severely influence the single postsynaptic response. The degree of modulation operated by the synaptic population depends on the number of synapses active, on the relative proportion between excitatory and inbibitory synapses belonging to the population and on their specific mean firing frequencies. In the present paper we show results obtained by the simulation of the activity of a single Glutamatergic excitatory synapse under the influence of two different populations composed of the same proportion of excitatory and inhibitory synapses but having two different sizes (total number of synapses). The most relevant conclusion of the present simulations is that the information transferred by the single synapse is not and independent simple transition between a pre- and a postsynaptic neuron but is the result of the cooperation of all the synapses which concurrently try to transfer the information to the postsynaptic neuron in a given time window. This cooperativeness is mainly operated by a simple mechanism of modulation of the postsynaptic membrane potential which influences the amplitude of the different components forming the postsynaptic excitatory response.  相似文献   
139.
Heat shock protein 27 (HSP27), an intracellular molecular chaperone, is involved in the pathogenesis of cancer by promoting both tumor cell proliferation and resistance to therapy. HSP27 is also present in the circulation and circulating HSP27 (sHSP27) can elicit an autoimmune response with production of antibodies. Levels of sHSP27 are enhanced in patients with hepatocellular carcinoma (HCC); it is, however, unknown whether changes in HSP27 antibody levels occur in patients with HCC and can be exploited as a circulating biomarker of HCC. Our aim was to assess the potential association between newly diagnosed HCC and serum anti-HSP27 antibody levels. In this cross-sectional study, anti-HSP27 antibody levels were measured in serum samples from 71 HCC patients, 80 subjects with chronic liver disease, and 38 control subjects by immunoenzymatic assay. Anti-HSP27 antibody levels did not differ significantly among groups. However, in patients with chronic active hepatitis/cirrhosis, anti-HSP27 levels were significantly higher in subjects with a positive history of alcoholism (p = 0.03). Our data do not support the hypothesis that anti-HSP27 antibody levels may help identify patients with HCC among subjects with chronic liver disease. However, our finding that alcohol-related liver disease is associated with higher anti-HSP27 levels is novel and deserves further investigations.  相似文献   
140.
Alonso  Alberto  Pérez  Javier  Monroy  Silvia  López-Rojo  Naiara  Basaguren  Ana  Bosch  Jaime  Boyero  Luz 《Ecosystems》2021,24(6):1436-1449
Ecosystems - Leaf litter of alder (Alnus glutinosa) is a key resource to detrital stream food webs. Due to its high quality and palatability, it is readily colonised by microorganisms and consumed...  相似文献   
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