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   159597篇
  免费   145724篇
  国内免费   29516篇
  2019年   3395篇
  2018年   3570篇
  2017年   3269篇
  2016年   3784篇
  2015年   4019篇
  2014年   4431篇
  2013年   5200篇
  2012年   5805篇
  2011年   6393篇
  2010年   6968篇
  2009年   11630篇
  2008年   6759篇
  2007年   6603篇
  2006年   5373篇
  2005年   5262篇
  2004年   5194篇
  2003年   4646篇
  2002年   5239篇
  2001年   8462篇
  2000年   5979篇
  1999年   9703篇
  1998年   9665篇
  1997年   9804篇
  1996年   9070篇
  1995年   9317篇
  1994年   8705篇
  1993年   8373篇
  1992年   9905篇
  1991年   9994篇
  1990年   10798篇
  1989年   9786篇
  1988年   9001篇
  1987年   8021篇
  1986年   7435篇
  1985年   6857篇
  1984年   5398篇
  1983年   4427篇
  1982年   4375篇
  1981年   3988篇
  1980年   3860篇
  1979年   4597篇
  1978年   4004篇
  1977年   3841篇
  1976年   3603篇
  1975年   3398篇
  1974年   3672篇
  1973年   3727篇
  1972年   3931篇
  1971年   3568篇
  1969年   3285篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
953.
954.
As previously reported, LPS and 8-derivatized guanosine (both generators of IL-1 release), as well as IL-1 itself interfere with the in vivo induction of tolerance to DHGG in A/J mice. In the present studies it was demonstrated that desensitization of either A/J or CBA/CaJ mice with LPS aborts the ability of LPS to interfere with the induction of tolerance to DHGG. The abrogation of the ability of LPS to interfere with tolerance by LPS desensitization is not the result of neutralization of LPS by antibody produced to LPS during desensitization. Desensitization with LPS also aborts the interference with tolerance induction by 7-methyl-8-oxoguanosine. LPS desensitization inhibits the ability of LPS and/or 7-methyl-8-oxoguanosine to both convert a tolerogenic signal to an immunogenic signal and interfere with the induction of a tolerant state to a subsequent injection of Ag. The effects resulting from desensitization may be in part attributed to the depletion of IL-1. LPS desensitization also modulates the antibody response to injection of the AG, AHGG. Desensitization with LPS markedly suppresses the antibody response to a subsequent injection of AHGG in CBA/CaJ mice. Desensitization with LPS also inhibits the anti-HGG antibody response in A/J mice, but in this strain its effect is dependent on the route of injection of AHGG. In an experiment directly comparing the responses of normal and desensitized A/J mice to either intravenous or intraperitoneal injection of AHGG, desensitization only suppressed the response in mice injected with AHGG i.p.. Desensitization with LPS also inhibits the ability of LPS to act as an adjuvant in a subsequent antibody response to AHGG. Not only does desensitization interfere with the primary antibody response to AHGG, but it also interferes with the secondary response, suggesting that the primary injection after desensitization induces a state of immunologic tolerance.  相似文献   
955.
956.
957.
958.
The thermotropic phase behavior of monosialoganglioside in a dilute aqueous dispersion at pH 6.8 was measured by using synchrotron radiation small-angle x-ray scattering and was analyzed by a shell-modeling method. Previous calorimetric studies on ganglioside systems have shown quite different thermotropic behaviors from other biological lipid systems, however, the details have still been ambiguous. Because of high statistical data and a shell-modeling analysis, we could elucidate the internal structural change of monosialoganglioside micelle induced by the elevation of temperature from 6 to 60 degrees C, that is, the shrinkage of the hydrophilic region and the slight expansion of the hydrophobic region occurring simultaneously, accompanying the elongation of the axial ratios of the ellipsoidal micelles. The model structures obtained explain the changes in the experimental scattering curves, the distance distribution functions, and the gyration radii. In addition we have also found an evident thermal hysteresis in the scattering curves and in the structural parameters. The present result suggests that the thickness of the hydrophilic region, namely, the conformation of oligosaccharide chains, is sensitive to a change of temperature.  相似文献   
959.
960.
The total monetary value of the harvestable stocks of commercial aquatic species in the Sea of Okhotsk, based on the Forecast of the Total Allowable Catch for 2014 and world prices for seafood, is estimated at $23.5 × 109 USD/year. The potential value of all the surveyed biological resources in the sea (including potential ones) in the case of their more complete economic use, $58.5 × 109 USD/year, is determined using the databases on macrofauna in the pelagic and benthic zones of the Far Eastern seas. Taking the mean value of ecosystem services per unit area in some parts of the World Ocean into account, the total value of ecosystem services for the Sea of Okhotsk may constitute $294.4 × 109 USD/year. The ecosystem services whose market values cannot be determined have a much higher cost than the traditionally exploited biological resources. The value of ecosystem services expressed in monetary terms can be considered as a tool to enhance the conservation importance of natural complexes in the course of the implementation of various industrial projects.  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