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   90150篇
  免费   5954篇
  国内免费   5331篇
  101435篇
  2024年   187篇
  2023年   1448篇
  2022年   2161篇
  2021年   2870篇
  2020年   2781篇
  2019年   3841篇
  2018年   3293篇
  2017年   2521篇
  2016年   2548篇
  2015年   3164篇
  2014年   5569篇
  2013年   6981篇
  2012年   4408篇
  2011年   5539篇
  2010年   4288篇
  2009年   4858篇
  2008年   5006篇
  2007年   5118篇
  2006年   4566篇
  2005年   4116篇
  2004年   3649篇
  2003年   3045篇
  2002年   2645篇
  2001年   1823篇
  2000年   1444篇
  1999年   1440篇
  1998年   1474篇
  1997年   1137篇
  1996年   1064篇
  1995年   993篇
  1994年   899篇
  1993年   681篇
  1992年   670篇
  1991年   547篇
  1990年   447篇
  1989年   352篇
  1988年   343篇
  1987年   274篇
  1986年   216篇
  1985年   323篇
  1984年   498篇
  1983年   356篇
  1982年   371篇
  1981年   275篇
  1980年   208篇
  1979年   196篇
  1978年   178篇
  1977年   144篇
  1976年   118篇
  1975年   108篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Desulfurization of model and diesel oils by resting cells of Gordona sp.   总被引:2,自引:0,他引:2  
The desulfurization activity of the resting cells of Gordona sp. CYKS1 was strongly depended on harvest time and the highest value when the cells had been harvested in the early growth phase (0.12 mg sulfur g–1 cell–1 h–1). For the model oil, hexadecane containing dibenzothiophene, the specific desulfurization rate decreased as the reaction proceeded. Both the specific and the volumetric desulfurization rates were not significantly affected by the aqueous-to-oil phase ratio. The diesel oils, light gas oil and a middle distillate unit feed were desulfurized at higher rates (ca. 0.34 mg sulfur g–1 cell–1 h–1) than the model oil (0.12 mg sulfur g–1 cell–1 h–1).  相似文献   
2.
3.
Plant somatic cells have the capability to switch their cell fates from differentiated to undifferentiated status under proper culture conditions, which is designated as totipotency. As a result, plant cells can easily regenerate new tissues or organs from a wide variety of explants. However, the mechanism by which plant cells have such remarkable regeneration ability is still largely unknown. In this study, we used a set of meristem-specific marker genes to analyze the patterns of stem cell differentiation in the processes of somatic embryogenesis as well as shoot or root organogenesis in vitro. Our studies furnish preliminary and important information on the patterns of the de novo stem cell differentiation during various types of in vitro organogenesis.  相似文献   
4.
The cysteine-rich region (CRR) of the β2 integrin subunit was replaced by that of β1 to give the chimera β2NV1. β2NV1 can combine with αL to form a variant leukocyte-function-associated antigen (LFA)-1 on COS cell surface, suggesting that the specificity of the β2 interaction with αL does not lie in the CRR. Unlike those expressing wild-type LFA-1, COS cells expressing αLβ2NV1 are constitutively active in intercellular adhesion molecule (ICAM)-1 adhesion. These results suggest that activation of LFA-1 involves the release of an intramolecular constraint, which is maintained, in part, by the authentic β2 CRR.  相似文献   
5.
《Cell reports》2020,30(1):112-123.e4
  1. Download : Download high-res image (131KB)
  2. Download : Download full-size image
  相似文献   
6.
Peanut (Arachis hypogaea) agglutinin (PNA) is extensively used as tumour marker as it strongly recognises the cancer specific T antigen (Galβ1→3GalNAc-), but not its sialylated version. However, an additional specificity towards Galβ1→4GlcNAc (LacNAc), which is not tumour specific, had been attributed to PNA. For correct interpretation of lectin histochemical results we examined PNA sugar specificity using naturally occurring or semi-synthetic glycoproteins, matrix-immobilised galactosides and lectin-binding tissue glycoproteins, rather than mono- or disaccharides as ligands. Dot-blots, transfer blots or polystyrene plate coatings of the soluble glycoconjugates were probed with horse-radish peroxidase (HRP) conjugates of PNA and other lectins of known specificity. Modifications of PNA-binding glycoproteins, including selective removal of O-linked oligosaccharides and treatment with glycosidases revealed that Galβ1→4GlcNAc (LacNAc) was ineffective while terminal α-linked galactose (TAG) as well as exposed T antigen (Galβ1→3 GalNAc-) was excellent as sugar moiety in glycoproteins for their recognition by PNA. When immobilised, melibiose was superior to lactose in PNA binding. Results were confirmed using TAG-specific human serum anti-α-galactoside antibody.  相似文献   
7.
We encountered a fourth case of honey allergy in Japan. We characterized and identified the IgE-binding proteins in honey using the serum of a honey-allergenic patient. Immunoblot analysis revealed that IgE in the patient serum specifically bound to four proteins in each honey sample. At least three of these IgE-binding proteins were N-linked glycoproteins. To identify the 60-kDa IgE-binding protein in dandelion honey, the N-terminal sequences of the fragmented protein were analyzed, revealing the protein to be major royal jelly protein 1 (MRJP 1). Three IgE-binding proteins removed of N-linked oligosaccharide showed a large reduction in IgE-binding activity as compared with the intact protein. This suggests that the carbohydrates in the IgE-binding proteins are a major epitope for patient IgE.  相似文献   
8.
《Developmental cell》2022,57(8):995-1008.e5
  1. Download : Download high-res image (144KB)
  2. Download : Download full-size image
  相似文献   
9.
《Cell reports》2020,30(1):98-111.e5
  1. Download : Download high-res image (124KB)
  2. Download : Download full-size image
  相似文献   
10.
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