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   95938篇
  免费   6913篇
  国内免费   505篇
耳鼻咽喉   1203篇
儿科学   2285篇
妇产科学   1382篇
基础医学   12397篇
口腔科学   2307篇
临床医学   9468篇
内科学   21106篇
皮肤病学   1517篇
神经病学   9198篇
特种医学   3942篇
外国民族医学   1篇
外科学   16028篇
综合类   793篇
一般理论   194篇
预防医学   6484篇
眼科学   1826篇
药学   5841篇
中国医学   139篇
肿瘤学   7245篇
  2023年   768篇
  2022年   1090篇
  2021年   3284篇
  2020年   1821篇
  2019年   2822篇
  2018年   3316篇
  2017年   2350篇
  2016年   2541篇
  2015年   2854篇
  2014年   3941篇
  2013年   5045篇
  2012年   7637篇
  2011年   7738篇
  2010年   4266篇
  2009年   3703篇
  2008年   6369篇
  2007年   6143篇
  2006年   5948篇
  2005年   5865篇
  2004年   5280篇
  2003年   4844篇
  2002年   4349篇
  2001年   616篇
  2000年   487篇
  1999年   684篇
  1998年   891篇
  1997年   710篇
  1996年   573篇
  1995年   565篇
  1994年   451篇
  1993年   459篇
  1992年   364篇
  1991年   324篇
  1990年   296篇
  1989年   288篇
  1988年   291篇
  1987年   265篇
  1986年   289篇
  1985年   287篇
  1984年   355篇
  1983年   308篇
  1982年   339篇
  1981年   338篇
  1980年   263篇
  1979年   151篇
  1978年   193篇
  1977年   181篇
  1976年   130篇
  1975年   134篇
  1974年   132篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
The clinical and post mortem findings of a case of malignant angioendotheliosis are described. The patient presented with neurological signs attributable to repeated episodes of cerebral and spinal cord infarction. Histological examination showed multifocal intravascular proliferation of mononuclear cells. Immunocytochemical characterisation of these neoplastic cells supports the recent suggestion that this disease represents an unusual form of intravascular lymphoma, which appears to show a predilection for blood vessels of the nervous system.  相似文献   
134.
Akt, a Serine/Threonine protein kinase, mediates growth factor-associated cell survival. Constitutive activation of Akt (phosphorylated Akt, P-Akt) has been observed in several human cancers, including lung cancer and may be associated with poor prognosis and chemotherapy and radiotherapy resistance. The clinical relevance of P-Akt in non-small cell lung cancer (NSCLC) is not well described. In the present study, we examined 82 surgically resected snap-frozen and paraffin-embedded stage I to IIIA NSCLC samples for P-Akt and Akt by Western blotting and for P-Akt by immunohistochemistry. P-Akt protein levels above the median, measured using reproducible semiquantitative band densitometry, correlated with a favorable outcome (P = 0.007). Multivariate analysis identified P-Akt as a significant independent favorable prognostic factor (P = 0.004). Although associated with a favorable prognosis, high P-Akt levels correlated with high tumor grade (P = 0.02). Adenocarcinomas were associated with low P-Akt levels (P = 0.039). Akt was not associated with either outcome or clinicopathologic variables.Cytoplasmic (CP-Akt) and nuclear (NP-Akt) P-Akt tumor cell staining was detected in 96% and 42% of cases, respectively. Both CP-Akt and NP-Akt correlated with well-differentiated tumors (P = 0.008 and 0.017, respectively). NP-Akt also correlated with nodal metastases (P = 0.022) and squamous histology (P = 0.037).These results suggest P-Akt expression is a favorable prognostic factor in NSCLC. Immunolocalization of P-Akt, however, may be relevant as NP-Akt was associated with nodal metastases, a known poor prognostic feature in this disease. P-Akt may be a potential novel therapeutic target for the management of NSCLC.  相似文献   
135.
Background: A new eight-wavelength pulse oximeter is designed to measure methemoglobin and carboxyhemoglobin, in addition to the usual measurements of hemoglobin oxygen saturation and pulse rate. This study examines this device's ability to measure dyshemoglobins in human volunteers in whom controlled levels of methemoglobin and carboxyhemoglobin are induced.

Methods: Ten volunteers breathed 500 ppm carbon monoxide until their carboxyhemoglobin levels reached 15%, and 10 different volunteers received intravenous sodium nitrite, 300 mg, to induce methemoglobin. All were instrumented with arterial cannulas and six Masimo Rad-57 (Masimo Inc., Irvine, CA) pulse oximeter sensors. Arterial blood was analyzed by three laboratory CO-oximeters, and the resulting carboxyhemoglobin and methemoglobin measurements were compared with the corresponding pulse oximeter readings.

Results: The Rad-57 measured carboxyhemoglobin with an uncertainty of +/-2% within the range of 0-15%, and it measured methemoglobin with an uncertainty of 0.5% within the range of 0-12%.  相似文献   

136.
137.
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   
138.
139.
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   
140.
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