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   59202篇
  免费   4895篇
  国内免费   46篇
  2023年   180篇
  2022年   304篇
  2021年   1088篇
  2020年   625篇
  2019年   811篇
  2018年   1234篇
  2017年   981篇
  2016年   1687篇
  2015年   2742篇
  2014年   3079篇
  2013年   3617篇
  2012年   4656篇
  2011年   4435篇
  2010年   2813篇
  2009年   2456篇
  2008年   3543篇
  2007年   3271篇
  2006年   3013篇
  2005年   2715篇
  2004年   2625篇
  2003年   2338篇
  2002年   1985篇
  2001年   1668篇
  2000年   1549篇
  1999年   1236篇
  1998年   546篇
  1997年   486篇
  1996年   415篇
  1995年   403篇
  1994年   317篇
  1993年   303篇
  1992年   649篇
  1991年   523篇
  1990年   487篇
  1989年   488篇
  1988年   414篇
  1987年   396篇
  1986年   331篇
  1985年   338篇
  1984年   282篇
  1983年   236篇
  1982年   199篇
  1981年   167篇
  1980年   176篇
  1979年   224篇
  1978年   203篇
  1977年   189篇
  1976年   177篇
  1974年   204篇
  1972年   163篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
71.
Rabbit alveolar macrophages exhibit a chemiluminescent response which is associated with phagocytosis of zymosan and polystyrene-butadiene particles. The chemiluminescence reaches a peak in 15 to 25 minutes and then gradually diminishes over the next 1 to 3 hours. During the time of maximal light emission there appears to be no actual uptake of particles, but the response is dependent upon the particle concentration. The metabolic inhibitor, DNP (2,4-dinitrophenol), causes a rapid inhibition of the chemiluminescent response. The addition of ATP to the medium prior to exposure of the cells to particles causes the chemiluminescent response to be greatly diminished, i.e., 0.3mM ATP virtually abolishes the response. These experiments suggest that some metabolic response of the cell to phagocytosis is responsible for the chemiluminescence.  相似文献   
72.
Although acupuncture therapy is widely used in traditional Asian medicine for the treatment of diverse internal organ disorders, its underlying biological mechanisms are largely unknown. Here, we investigated the functional involvement of acupuncture stimulation (AS) in the regulation of inflammatory responses. TNF-α production in mouse serum, which was induced by lipopolysaccharide (LPS) administration, was decreased by manual acupuncture (MAC) at the zusanli acupoint (stomach36, ST36). In the spleen, TNF-α mRNA and protein levels were also downregulated by MAC and were recovered by using a splenic neurectomy and a vagotomy. c-Fos, which was induced in the nucleus tractus solitarius (NTS) and dorsal motor nucleus of the vagus nerve (DMV) by LPS and electroacupuncture (EAC), was further increased by focal administration of the AMPA receptor blocker CNQX and the purinergic receptor antagonist PPADS. TNF-α levels in the spleen were decreased by CNQX and PPADS treatments, implying the involvement of inhibitory neuronal activity in the DVC. In unanesthetized animals, both MAC and EAC generated c-Fos induction in the DVC neurons. However, MAC, but not EAC, was effective in decreasing splenic TNF-α production. These results suggest that the therapeutic effects of acupuncture may be mediated through vagal modulation of inflammatory responses in internal organs.  相似文献   
73.
Rapid and reproducible method is described here for the purification of the 43 kDa fimbrial protein from P. gingivalis by preferential fractionation in the presence of 1% SDS and 0.2M of a bivalent cation at pH 6.5. Homogeneity of the purified 43 kDa was confirmed by SDS-PAGE and Western blot analysis using monoclonal and polyclonal antibodies raised against this protein. Amino acid composition and the amino acid sequence of the first 30 amino acid residues of the purified fimbriae are consistent with the composition and sequence predicted from the cloned gene of the fimbrial subunit. Circular dichroism spectra shows high levels of beta-sheet structure. The purified 43 kDa polymer shows fimbriae-like morphology under the electron microscope. Ultrastructural localization of the 43 kDa protein by the immunogold technique revealed specific labeling of the fimbriae with a diameter of approximately 3.5 to 5.0 nm. Localization of this protein suggest that the 43 kDa component is a fimbrial subunit.  相似文献   
74.
Avian oviductal fluids contain phosphorylating-dephosphorylating enzymes that might function in sperm-oocyte interactions. Phosphorprotein phosphatase and protein kinase have been purified 20-fold and 40-fold, respectively. The latter easily aggregates and is highly labile. Other properties are comparable to those of holoenzymes.  相似文献   
75.
76.
77.
78.
79.
80.
88 rice and 75 soybean samples were collected from 8 provinces of Korea from March through September in 1988. The Fusarium mycotoxins, zearalenone was analyzed by direct competitive enzyme linked immunosorbent assay. 10.2% of rice and 9.3 % of soybean samples contained detectable zearalenone. The average levels of zearalenone of rice and soybean samples were 11.78μg/kg and 7.70μ/kg, respectively.  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