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   99189篇
  免费   6788篇
  国内免费   515篇
耳鼻咽喉   1228篇
儿科学   2400篇
妇产科学   1420篇
基础医学   12751篇
口腔科学   2364篇
临床医学   9718篇
内科学   21957篇
皮肤病学   1560篇
神经病学   9520篇
特种医学   4017篇
外国民族医学   1篇
外科学   16445篇
综合类   810篇
一般理论   194篇
预防医学   6706篇
眼科学   1870篇
药学   5938篇
中国医学   142篇
肿瘤学   7451篇
  2023年   879篇
  2022年   1513篇
  2021年   3333篇
  2020年   1850篇
  2019年   2896篇
  2018年   3402篇
  2017年   2407篇
  2016年   2600篇
  2015年   2910篇
  2014年   4043篇
  2013年   5149篇
  2012年   7760篇
  2011年   7909篇
  2010年   4359篇
  2009年   3776篇
  2008年   6483篇
  2007年   6286篇
  2006年   6061篇
  2005年   5998篇
  2004年   5408篇
  2003年   4961篇
  2002年   4452篇
  2001年   699篇
  2000年   596篇
  1999年   769篇
  1998年   922篇
  1997年   728篇
  1996年   591篇
  1995年   578篇
  1994年   470篇
  1993年   466篇
  1992年   396篇
  1991年   360篇
  1990年   323篇
  1989年   300篇
  1988年   307篇
  1987年   283篇
  1986年   301篇
  1985年   296篇
  1984年   368篇
  1983年   313篇
  1982年   342篇
  1981年   340篇
  1980年   265篇
  1979年   156篇
  1978年   196篇
  1977年   183篇
  1976年   132篇
  1975年   141篇
  1974年   138篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Mielke  H.  Daniel  W.  Deicher  H.  Drommer  W.  Fischer  M.  Fritsch  R.  M&#;ller-Vahl  H.  Sybrecht  G. W. 《Clinical rheumatology》1987,6(2):26-34
Clinical Rheumatology - Rheumatoid arthritis (RA) as a systemic disease can attack many other organs in addition to the joints. A variety of pathological lesions of the blood vessels are...  相似文献   
24.
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   
25.
26.
Extracellular single-unit recordings were made in somatosensory cortical barrels of fentanyl-sedated rats. Whiskers were deflected singly or in paired combinations. lontophoretically-applied (−)-baclofen disproportionately reduced weak responses, and phaclofen disproportionately increased them, resulting in more tightly focused or more broadly focused receptive fields, respectively. Both drugs had only minor effects on surround inhibition. In light of previous findings, we conclude that GABAA and GABAB mechanisms both act to enhance spatial contrast, but that the former plays a much greater role in enhancing temporal resolution.  相似文献   
27.
Species-level identification of Acanthamoeba isolates is difficult and gives little or no indication of the isolate's pathogenicity. We identified two amplification-based genetic markers that were highly correlated with pathogenicity in Acanthamoeba spp. One marker, designed to amplify a 485-bp fragment of the small-subunit ribosomal RNA gene (ssrDNA), was preferentially amplified from the nonpathogenic strains; amplifications from the pathogenic strains yielded anomalous fragments of 650 and 900?bp. A second marker was developed on the basis of the anomalous 650-bp fragment. Primers to this sequence preferentially amplified a noncoding locus (called Ac6) only from the pathogenic strains. These two genetic markers may be useful for identification of pathogenic Acanthamoeba spp. strains.  相似文献   
28.
We describe the presence of cylindrical spirals on muscle biopsy from a 31-year-old man who developed rhabodomyolysis following a long run. He had a prior history of exertional cramps and myoglobinuria. His maternal grandfather had similar symptoms. Transmission electron micrographs demonstrated continuity between the lamellae of the cylindrical spirals and native myofilaments. Whether these unusual structures confer a derangement in myofilament function is uncertain.  相似文献   
29.
A new technique of forehead rhytidectomy is presented that combines the best features of the coronal incision with those of the anterior hairline incision. The plane of dissection is formed by an anterior subcutaneous plane dissecting a lateral subgaleal plane. This approach is particularly valuable in patients with high foreheads, severe static wrinkling, and asymmetrical eyebrows.Presented in part at the Annual Meeting of the American Society of Aesthetic Plastic Surgeons, Boston, MA, 1984  相似文献   
30.
The in vitro capacity of sympathetic superior cervical ganglia (SCG) to take up [3H]choline from the extracellular medium, to synthesize acetylcholine from [3H]choline, and to release [3H]acetylcholine in response to a high K+ concentration, were examined in rats throughout a 24-h cycle. Both the release of [3H]acetylcholine and the synthesis of [3H]acetylcholine from [3H]choline exhibited significant diurnal variations, showing maxima during the first half of the night. After these maxima, nocturnal acetylcholine release and synthesis decayed to daytime levels and remained low until the end of the night. [3H]Choline uptake by rat SCG did not vary significantly throughout a 24-h period. A 1.5-h exposure of rats to darkness at the 5th hour of light phase of the daily photoperiod did not change significantly any parameter studied. A 20-min, 5-Hz, electrical stimulation of the preganglionic trunk of SCG excised from rats at noon increased significantly subsequent K+-induced [3H]acetylcholine release but did not change [3H]acetylcholine synthesis. In decentralized SCG of rats subjected to a unilateral SCG decentralization and a contralateral sham-operation 7 days earlier, [3H]acetylcholine release and synthesis were highly reduced or abolished at the decentralized side, while [3H]choline uptake remained unaltered. The present results suggest that an activation of preganglionic rat SCG neurons takes place during the first half of the scotophase.  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