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   800篇
  免费   18篇
  国内免费   17篇
系统科学   5篇
丛书文集   5篇
教育与普及   14篇
理论与方法论   3篇
现状及发展   8篇
综合类   798篇
自然研究   2篇
  2024年   2篇
  2023年   6篇
  2022年   10篇
  2021年   7篇
  2020年   12篇
  2019年   8篇
  2018年   11篇
  2017年   26篇
  2016年   18篇
  2015年   18篇
  2014年   38篇
  2013年   25篇
  2012年   36篇
  2011年   47篇
  2010年   29篇
  2009年   45篇
  2008年   52篇
  2007年   57篇
  2006年   50篇
  2005年   56篇
  2004年   47篇
  2003年   48篇
  2002年   27篇
  2001年   36篇
  2000年   21篇
  1999年   24篇
  1998年   10篇
  1997年   16篇
  1996年   6篇
  1995年   9篇
  1994年   4篇
  1993年   5篇
  1992年   1篇
  1991年   6篇
  1990年   8篇
  1989年   7篇
  1988年   3篇
  1987年   3篇
  1985年   1篇
排序方式: 共有835条查询结果,搜索用时 713 毫秒
381.
目的:了解慢性腰椎间盘突出病人的心理状况.方法:对门诊治疗的78例腰椎间盘突出患者进行蒙医传统治疗后对躯体症状复发的、恐惧心理、焦虑、抑郁以及对药物依从性的情况采用SCL-90自评量表进行对照测查.结果:病人组与对照组有显著性差异,病人总体心理健康水平下降、应付能力差.结论:慢性疾病的反复发作及长期服药对病人的心理健康水平产生重要影响.  相似文献   
382.
383.
Hou  Shugui  Qin  Dahe  Yao  Tandong  Zhang  Dongqi  Chen  Tuo 《科学通报(英文版)》2002,47(20):1746-1749
Three ice cores recovered from the Himalayas (i.e. the East Rongbuk Glacier and the Far East Rongbuk Glacier at Mt. Qomolangma (Everest), and the Dasuopu Glacier at Xixiabangma) show a sharp decline in the accumulation rates since the 1950s, which is consistent with the precipitation fluctuation over India and the low northern latitude zone (5°-35°N). Correspondingly, an increasing trend is observed for the ice core accumulations from the central and northern Qingh ai-Tibetan Plateau (i.e. the Xiao Dongkemadi Glacier in the central Tanggula Mountains, the Guliya Ice Cap in the western Kunlun Mountains, and the Dunde Ice Cap in the Qilian Mountains) since the 1950s, which is consistent with the precipi tation fluctuation over the middle-high northern latitude zone (35°-70°N). However, the variation magnitude of the high-elevation ice core accumulations is more significant than that of precipitation at the low-eleva- tion places, suggesti ng its extra sensitivity of high-elevation areas to climatic change. The inter-d ecadal abrupt change of the African-Asian summer monsoon in the1960s may attribute to the recent ice core accumulation change during the recent decades.  相似文献   
384.
Using NCEP dataset we calculate the exchange of mass across the thermal tropopause by the Wei's method from 1978 to 1997 over the Tibetan Plateau and its surroundings. We also calculate the annual variation of aerosol and ozone of 100 hPa level with the monthly SAGE dataset from July 1988 to December 1993. Results indicate that ( i ) the mass from troposphere to stratosphere is magistral station in summer over the Tibetan Plateau and its surroundings. The air transport reaches the summit in midsummer with two large value centers, which lie in the north of Bengal Bay and southeastern Tibetan Plateau, respectively. A large value center, which lies over the Tibetan Plateau, is smaller than that aforementioned. In winter, the mass transport is from stratosphere to troposphere, and reaches the minimum in January. ( ii ) As far as the 19-year mean cross-tropopause mass exchange from June to September is concerned, the net mass transport is 14.84x1018 kg from troposphere to stratosphere. So the area from the Tibetan Plateau to the Bengal Bay is a channel through which the mass of lower atmosphere layer gets into upper troposphere and lower stratosphere. (iii) The cross-tropopause mass may take the lower level aerosol to the tropopause. Then, the concentration of aerosol near the tropopause becomes larger, which may cause the content of ozone to reduce.  相似文献   
385.
386.
40Ma前印度板块与欧亚板块的碰撞导致了特提斯海的封闭和西藏成陆,但40~20MaBP间地面很低。20Ma前的构造运动使青藏地区一些山地隆起,但而后又经历了长期的夷平,地貌与生物证据揭示,早上新世高原的高度仅约1000m。高原的强烈隆起开始于3.4Ma前,这被高原内外普遍的砾岩堆积和盆地演化记录了下来。青藏高原东部盆地演化与大河流发育研究表明,至少有10次强构造上升事件发生,它们分别开始于3.4、2.5、1.7、1.3、1.1、0.8、0.6、0.14、0.05和0.01MaBP。其中2.5、1.1、0.8、0.6和0.14MaBP五次上升事件对高原隆起十分重要。  相似文献   
387.
Short cores of about 80-cm retrieved from three main basins of th e deepwater areas in Qinghai Lake,the largest inland enclosed lake in China, were studied. Sta-ble isotopes of authigenlc carbonates, grain-size, carbonate and organic matter content at 5-year resolution are used to reconstruct the climatic history over the last 800 years in the Northeastern Tibetan Plateau. Chronology was established according to 210^pb dating and 137^Cs methods and the core corrdation. It is found that cores from different deep basins of the lake can be well correlated. The sedimentary rate is highest in the western basin of the lake and lowest in the east.In the southern basin of the lake where the short core Qing-6is located, the recent average sedimentation rate is 0.1004cm/yr. Variations in effective precipitation recorded by the oxygen isotopes and grain size data durine the last 800 years are consistent with the glacial accumulation record form the Dunde and Guliya ice cores. A dry climate lasted for 300 years from 1200 AD to 1500 AD, followed by a wet period from 1500 to 1560 AD. The two dry periods, 1560 to 1650 AD and 1780 to 1850 AD, were the results of southwest monsoon weakening. The effective precipitation generally increased since 1650 AD due to the strengthening of the Asian South-west Monsoon, resulting in a wet period until the 1950s. Ex-cept the early stage, the Little Ice Age on the Plateau is characterized b y increased effective moisture. Organic mat-ter content, with nearly 200-year cycles, shows similar trend with the atmospheric delta earbon-14 before the 1850s, indi-eating that the bioproductivity responds to solar activity.  相似文献   
388.
黄土高原景观生态特征及其生态恢复的意义   总被引:4,自引:0,他引:4  
对黄土高原景观生态学特征的分析表明:黄土高原景观在空间上具有明显的分带性,显著的黄土垂直节理特征,独特的坡面景观结构、微地貌景观以及农业景观,呈现以景观带为基质,斑、廊、缘为点缀的复杂景观镶嵌格局;在时间上存在明显的季节景观变化和地质时间尺度景观变化,沟蚀系统的发展决定了其地貌景观的基本骨架和发展方向.黄土高原的生态恢复要遵从景观生态学原理,科学理解黄土高原生态恢复的涵义,合理选择林草恢复措施等.  相似文献   
389.
为得到高原深水湖泊中微生物携带质粒情况,运用分子生物学方法对两个代表性高原湖泊—阳宗海(深水,贫营养)和滇池(浅水,富营养)中的PNSB的质粒进行提取。阳宗海中带质粒的PNSB全部来自13m以上,红细菌属的质粒检出率最高;滇池中,污染程度高的水域中分离的PNSB携带质粒几率高于中度和轻度污染位点,红假单胞菌属的质粒检出率最高。两湖PNSB质粒大小都在10000bp左右,滇池中PNSB质粒检出率(24.3%)高于阳宗海PNSB质粒检出率(7.04%)3倍以上。  相似文献   
390.
亲属称谓词是亲属制度在语言中的反映。借词是语言接触的必然结果,蒙古语亲属称谓词中的汉语借词反映了蒙、汉两个民族在婚姻家庭层面上的影响特点。从语言、文化和婚姻的角度可以说明汉语亲属称谓词的借入特点。  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