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   13354篇
  免费   710篇
  国内免费   95篇
耳鼻咽喉   90篇
儿科学   227篇
妇产科学   123篇
基础医学   2174篇
口腔科学   98篇
临床医学   1352篇
内科学   2961篇
皮肤病学   356篇
神经病学   1310篇
特种医学   527篇
外科学   2031篇
综合类   48篇
一般理论   2篇
预防医学   659篇
眼科学   215篇
药学   967篇
中国医学   40篇
肿瘤学   979篇
  2023年   62篇
  2022年   85篇
  2021年   258篇
  2020年   151篇
  2019年   223篇
  2018年   323篇
  2017年   206篇
  2016年   236篇
  2015年   269篇
  2014年   376篇
  2013年   515篇
  2012年   910篇
  2011年   1027篇
  2010年   608篇
  2009年   539篇
  2008年   883篇
  2007年   1015篇
  2006年   906篇
  2005年   949篇
  2004年   881篇
  2003年   867篇
  2002年   841篇
  2001年   136篇
  2000年   103篇
  1999年   145篇
  1998年   212篇
  1997年   166篇
  1996年   164篇
  1995年   110篇
  1994年   109篇
  1993年   108篇
  1992年   96篇
  1991年   59篇
  1990年   56篇
  1989年   65篇
  1988年   51篇
  1987年   45篇
  1986年   46篇
  1985年   32篇
  1984年   45篇
  1983年   42篇
  1982年   41篇
  1981年   32篇
  1980年   35篇
  1979年   24篇
  1978年   25篇
  1977年   17篇
  1976年   10篇
  1975年   8篇
  1974年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
A cytomorphometric analysis of superficial vaginal cells inwomen in three groups of different types of hormonal concentrationwas made. There were 15 women in each group. Group I was studiedduring a natural cycle, group II under oral contraceptive therapyand group III during an in-vitro fertilization (IVF) stimulationprotocol. Morphometric parameters were measured on an imageanalyser. The area, perimeter and several form factors weremeasured separately for nuclei and cytoplasm. The nucleus:cytoplasmicratio was also determined. The cytoplasmic area was significantlyreduced in group II and was associated with a statisticallysignificant reduction of the nuclear area. The nucleus:cytoplasmicratio appeared significantly increased in group II and reducedin group III. Low oestradiol impregnation obtained with an oralminidosed contraceptive interfered with vaginal cell maturation.High oestradiol concentrations obtained during IVF protocolsinduced marked nuclear pycnosis but did not induce supra-physiologicalcell enlargement. Maximal cell size is genetically regulatedaccording to Driesch's law of volume invariance and hormonalover-stimulation has no effect on cell size. The nucleus:cytoplasmicratio appears to be a powerful parameter reflecting the oppositeeffects of hormones on cell compartments.  相似文献   
4.
5.
Edrophonium, an anticholinesterase, exerts a biphasic effect on cardiovascular autonomic drive in humans (lower doses enhance; higher doses reduce). Twenty-five anesthetized, mechanically respired (10 breaths. min(-1), constant tidal volume) patients were given either saline (n = 10) or edrophonium (0.01-1.0 mg. kg(-1), n = 15) following surgery. ECG, radial arterial pressure, and respiratory rate were sampled at 250 Hz to obtain time series for consecutive R-R intervals (RRIs), and systolic (SBP) and diastolic blood pressure (DBP). A Wigner distribution was used for time frequency mapping of spectral powers at high (HFP, 0.15-0.5 Hz) and low (LFP, 0.0-0.05 Hz) frequency. Edrophonium produced a dose-dependent decrease in heart rate [baseline 66.8 +/- 1.9 (S.E.M.) beats per minute; maximum decrease to 55.8 +/- 1.4 beats per minute with 1.0 mg. kg(-1), P < 0.01]. HFP of the RRI increased at low doses (0.2-0.4 mg. kg(-1); maximum increase to 111.0 +/- 58.2% baseline; P < 0.01) but decreased (-49.5 +/- 35.5% baseline; P < 0.01) at higher (1.0 mg. kg(-1)) doses. Edrophonium had no effect on SBP and DBP. HFP of SBP decreased with increasing doses (maximal decrease to -26.2 +/- 7.5% baseline, P < 0.01, 1.0 mg. kg(-1)). LFP of SBP was also decreased (-46.3 +/- 10.9% baseline, P < 0.01, 1.0 mg. kg(-1)). Edrophonium may enhance (lower dose) or reduce (higher dose) cardiovascular autonomic drive in humans, as evidenced by the significant changes it evokes in HFP of the RRI (parasympathetic drive), and in the HFP and LFP of SBP (sympathetic drive). These observations may account for the modest autonomic side effects of edrophonium when this drug is used clinically.  相似文献   
6.
The synaptic connections established by grafted noradrenergic (NA) neurons into the lesioned adult rat spinal cord were analysed using immunocytochemistry at the electron microscopic level. An embryonic cell suspension of the locus coeruleus region from E-13 rat embryos was transplanted into the spinal cord following either: (1) spinal cord transection or (2), partial selective denervation by 6-hydroxy dopamine (6-OH DA). One month after grafting, the NA-neurons established, in the two models, an innervation pattern similar to that found in the intact spinal cord. In both models, the transplanted NA-immunoreactive neurons formed extensive synaptic contacts with dendrites, spines and perikarya. The proportion of axodendritic and axospinous contacts was inverse in the two models. The first model thus reproduced more closely the normal synaptic pattern prefering dendritic targets, which could correspond to a better integration of the graft. In the second model, a partially NA-denervated spinal cord, there existed a competition between residual intrinsic and grafted neuron-derived fibres, which presumably affects synaptogenesis. In conclusion, the present study illustrate the complexity of cell interations conducting to the formation of a specific circuitry. Recognition phenomenon are likely modulated by space constraints, which ultimately shape-up the geometry of synaptic contacts.  相似文献   
7.
8.
9.
We report two patients with ipsilateral attacks of cluster headache and chronic paroxysmal hemicrania. The first patient, a 33-year-old man, started having attacks of chronic cluster headache at the age of 27. At 33, they were replaced by typical attacks of ipsilateral chronic paroxysmal hemicrania which showed a dramatic improvement with indomethacin 150 mg daily. After two days of complete remission, cluster headache attacks reappeared and persisted until verapamil, 360 mg a day, was added to indomethacin. The second patient, a 45-year-old man, first developed attacks of episodic cluster headache at the age of 35. At 44, he experienced ipsilateral typical attacks of chronic paroxysmal hemicrania, and two months later attacks of cluster headache. Under verapamil 240 mg daily, attacks of cluster headache disappeared, but those of chronic paroxysmal hemicrania increased in frequency until indomethacin 150 mg daily was added. These observations suggest a close relationship but not a similarity between cluster headache and chronic paraoxysmal hemicrania, and show the practical therapeutic interest of maintaining this distinction.  相似文献   
10.
We report the occurrence of knee joint effusion with prolonged functional impairment in a 17-year old boy with cystic fibrosis treated with pefloxacin for recurrent lower respiratory tract infections caused by Pseudomonas aeruginosa. Because the quinolone pefloxacin fairly often induces joint disease in pediatric age groups, we advocate restricting its use to those patients whose growth is completed. In growing individuals, it seems reasonable to use second generation quinolones only in infections caused by resistant organisms and to avoid exerting the joints during treatment.  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