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   2150篇
  免费   100篇
  国内免费   524篇
测绘学   62篇
大气科学   250篇
地球物理   1070篇
地质学   745篇
海洋学   298篇
天文学   93篇
综合类   98篇
自然地理   158篇
  2023年   18篇
  2022年   21篇
  2021年   29篇
  2020年   18篇
  2019年   19篇
  2018年   25篇
  2017年   9篇
  2016年   34篇
  2015年   26篇
  2014年   51篇
  2013年   47篇
  2012年   118篇
  2011年   166篇
  2010年   41篇
  2009年   60篇
  2008年   142篇
  2007年   141篇
  2006年   143篇
  2005年   148篇
  2004年   136篇
  2003年   90篇
  2002年   102篇
  2001年   78篇
  2000年   97篇
  1999年   43篇
  1998年   36篇
  1997年   44篇
  1996年   57篇
  1995年   68篇
  1994年   45篇
  1993年   81篇
  1992年   66篇
  1991年   88篇
  1990年   80篇
  1989年   56篇
  1988年   58篇
  1987年   42篇
  1986年   35篇
  1985年   30篇
  1984年   24篇
  1983年   15篇
  1982年   14篇
  1981年   13篇
  1980年   22篇
  1978年   5篇
  1976年   6篇
  1974年   8篇
  1948年   8篇
  1947年   8篇
  1943年   4篇
排序方式: 共有2774条查询结果,搜索用时 15 毫秒
951.
In previous papers Jansson's method was found to be successful at deconvolving severely overlapped gaschromatographic peaks.In the most recent paper the method was evaluated with respect to quantitativeaceuracy,peak area and retention time repeatability.The problems associated with deconvolving noisydata and some alternatives which can improve the ability of Jansson's method to deconvolve noisy dataare discussed.These alternatives include presmoothing the data with a nine-point,third-order polynomialfilter and data reblurring.This paper will test these methods on peaks with various degrees of resolutionand signal-to-noise ratios.  相似文献   
952.
953.
A previously developed model of a 2-dimensional air flow with constant horizontal shear is used to estimeate the accuracy of the geostrophic momentum approximation by comparison of exact solutions when exist with approximate ones.  相似文献   
954.
Pure fraction (92% - 95%) of phagocytes (FP) and a mixture of amoebocytes (62%) and morula cells (38 % )-FPMC- of the holothurian Eupentacta fraudatrix ( Holothuroidea,Dendrochirota ) were obtained by using ficoll-verographine step gradient. Basal production of reactive oxygen species (ROS) in FP quantified by using reduction of nitroblue tetrazolium (NBT) was more than twice that in FPMC. Thermostable toxin of Yersinia pseudotuberculosis (TST) at differentconcentrations ( 0.2; 0.5; 2.5 μg/ml, but not 0.1 μg/ml) stimulated NBT reduction in FPMC after 24 h incubation. In FP, TST at concentrations of 0.1 and 0.2 μg/ml inhibited and at concentrations of 0.5 and 2.5 μg/ml stimulated NBT reduction after 24 h incubation. Maximal effect was observed in FP and FPMC at TST concentrations of 0.5 and 0.2 μg/ml, respectively. Addition of catalase (0.7 μg/ml) to the cells treated with TST (2.5 μg/ml) was followed by a decrease in NBT reduction compared to that under toxin treatment alone. TST stimulated superoxide dismutase activity in ccncentration-dependent manner (maximum at 0.5 μg/ml concentration in FP) after 24 htreatment, and this stimulation was prevented by a commercial catalase. Plant lectin concanavalin A stimulated NBT reduction more than 5-fold in FPMC compared to the control. With addition of TST, lectin stimulated ROS to lesser extent than that with lectin alone. When catalase, TST, and lectin were added into the FPMC simultaneously, ROS increase was similar to that under lectin treatment alone. On the whole, data obtained indicated that ROS generation in holothurian coelomocytes especially occurs in both stimulated and not stimulated phagocytes, and that changes in ROS production by these cells may be one of the mechanisms of antibacterial protection of holothurians.  相似文献   
955.
1 NEEDFORNEWCOMPETITIVENESSINTHEPEARLRIVERDELTAIn1978ChinaadoptedanewapproachofOpen andReforminitsdevelopment.Priortothis,HongKongwasaBritish-runenclaveoffreetrade,andwaslittlerelatedeconomicallywithitsnextdoorneighborandnaturalhinterland—thePearl(Zhujiang)RiverDelta(PRD)(SIT,1991).Sincethen,localinitiativesofGuangdongProvinceanditsconstituentmunicipalitieshaveprovidedanattractivemilieuforHongKongin-vestment.IthassoongrownintoHongKong'snewmanufacturingbasewhileHong…  相似文献   
956.
One of the major applications of factor analysis in the chemical literature,self-modeling curve resolution(SMCR),is covered in this review,including a historical account of the inethods derived from Lawtonand Sylvestre's original method.Papers treating the theory or applications of SMCR are included.Qualitative and quantitative applications are described where appropriate.  相似文献   
957.
958.
A case study of the convectively driven monsoon boundary layer has been carried out using the aerological observations at four stations in the region of monsoon trough during Monsoon Trough Boundary Layer Experiment (MONTBLEX) 1988. The Convective Boundary Layer (CBL) in the region of monsoon trough did not show double mixing line structure. A single mixing line representing the CBL with different stabilities with respect to the convective activities was observed.  相似文献   
959.
该书的作者们独辟蹊径地研究整个显生宙地层剖面,其目的是从这些剖面可能揭示出一系列地外成因的事件。暂且不论这费劲的工作收益有多大,一个引人深思的问题在于,象这样一本书在10年前能否被接受并出版?但正是在这10年间,许多地质学家已注意到:他们研究的课题同天文学和天体物理学有联系。1980年出现了观念性的变化,在这之前,任何一种把  相似文献   
960.
从1985年开始,安娜大学水资源中心在马德拉斯含水层系统(MAS)有规律地进行了水文地球化学研究,该含水层系统包括北-西北部多层含水层和南部半承压含水层。马德拉斯大城市居民的60~70~*%,供水来自马德拉斯含水层系统,在干旱年份,近  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