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   97373篇
  免费   7717篇
  国内免费   32篇
  2021年   834篇
  2018年   1303篇
  2017年   1213篇
  2016年   1640篇
  2015年   1738篇
  2014年   2099篇
  2013年   2979篇
  2012年   3273篇
  2011年   3357篇
  2010年   2505篇
  2009年   2107篇
  2008年   3061篇
  2007年   3013篇
  2006年   2833篇
  2005年   2680篇
  2004年   2667篇
  2003年   2550篇
  2002年   2376篇
  2001年   4404篇
  2000年   4167篇
  1999年   3226篇
  1998年   1047篇
  1997年   1038篇
  1996年   917篇
  1995年   839篇
  1993年   833篇
  1992年   2453篇
  1991年   2462篇
  1990年   2466篇
  1989年   2208篇
  1988年   2071篇
  1987年   1980篇
  1986年   1827篇
  1985年   1825篇
  1984年   1505篇
  1983年   1297篇
  1982年   932篇
  1981年   874篇
  1979年   1435篇
  1978年   1128篇
  1977年   1017篇
  1976年   973篇
  1975年   1162篇
  1974年   1257篇
  1973年   1345篇
  1972年   1186篇
  1971年   1042篇
  1970年   922篇
  1969年   956篇
  1968年   836篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
121.
Collozoum inerme (Müller) is a colonial Radiolarian containing numerous cells bound in a common gelatinous matrix. The cells do not possess a skeleton as observed in many unicellular Radiolaria, but the cytoplasmic organization is similar. The cells are multinucleate and a complex system of cellular processes containing mitochondria, Golgi, and numerous vacuoles radiate out from the nuclear region. The endoplasm is connected to the ectoplasm across a double membrane boundary by thin cytoplasmic strands called fusules whose structure resemble those in unicellular Radiolaria. The ectoplasm contains a lacy network of vacuoles containing an osmiophilic substance. Rhizopodia emerge from the ectoplasmic sheath. Some are thin and densely granular. Larger diameter rhizopodia, containing less dense cytoplasm, sequester the zooxanthellae which present a typical dinoflagellate fine structure. Some of the zooxanthellae are apparently cultivated since they are sometimes observed dividing and persist in large numbers when colonies are cultivated under illumination for several weeks in the laboratory. However, colonies maintained in the dark have a decline in number of zooxanthellae and light microscopic examination shows they are being drawn into the ectoplasm of the radiolarian cells. Electron microscopic examination of zooxanthellae drawn into the ectoplasm sheath indicates they are digested. C. inerme is a remarkable example of a simple cellular aggregate that has exploited its colonial habit to culture algae and use them as food thus possibly enhancing the viability of the colony.  相似文献   
122.
Power spectra and coherence function of EEG of various cortical areas of both hemispheres were analyzed in 9 patients with extremely protracted loss of consciousness. Five patients were in the state of posttraumatic apallic syndrome lasting for more than 4 years in one patient, and 4-9 months with successive lethal outcome in 4 patients. One patient for more than 2 years was in a state of areactivity to external signals. In 3 patients the process of recovery of consciousness and speech began in 1-2 months. At the apallic syndrome, only low-frequency EEG components were present in spectrograms, and the values of coherence function were sharply decreased. With recovering consciousness and speech, a gradual appearance of alpha-activity was observed as well as an increase of coherence values at the frequency of the alpha-rhythm. The recovery of intercentral EEG relations in the motor-verbal cortical area was shown to play a special role in further normalization of connections in the cerebral cortex.  相似文献   
123.
124.
125.
126.
127.
The perfusion procedure described in this paper produces high quality impregnation of pig visual and somatosensory cortical neurons with a Golgi-Cox solution. Starting within 30 min after death, pig heads were perfused with a fixative solution composed of a mixture (v/v) of liquid phenol, 5%; formalin, 14%; ethylene glycol, 25%; methanol, 28%; and water, 28% for two periods of 4 hr each. After perfusion, the heads were chilled for at least 18 hr. The entire brain was removed from the skull and then placed in 10% buffered formalin, where it remained for at least 10 days before taking the blocks that were to be immersed in the Golgi-Cox solution. Three weeks spent in the Golgi-Cox solution typically produced uniform neuron impregnation. The tissue blocks were then embedded in celloidin and sectioned at 120 micron. This procedure avoids the following difficulties: Golgi-Cox methods that produced excellent results with rodent or primate tissue were unsuccessful with pig tissue, placing fresh tissue in Golgi-Cox solution resulted in incomplete neuron impregnation, and immersion fixation in 10% buffered formalin without perfusion resulted in excessive staining of glia.  相似文献   
128.
129.
130.
The paper is concerned with analysis of the results of intraoperative phlebotesticulography, performed in 50 patients with varicocele of degree I-II during Ivanissevich's operation. The effect of surgical intervention was shown to depend upon the quality of ligation of the testicular vein, some parts of which are anastomosed between themselves. The localization of this anastomosis is revealed by means of intraoperative phlebotesticulography, which permits increasing the results of surgical treatment and predicting a course of a postoperative period.  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