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   5446704篇
  免费   409905篇
  国内免费   16093篇
耳鼻咽喉   77096篇
儿科学   173281篇
妇产科学   145845篇
基础医学   803705篇
口腔科学   156634篇
临床医学   499853篇
内科学   992389篇
皮肤病学   127149篇
神经病学   450616篇
特种医学   212865篇
外国民族医学   1200篇
外科学   818110篇
综合类   152883篇
现状与发展   24篇
一般理论   3000篇
预防医学   448317篇
眼科学   130730篇
药学   393227篇
  28篇
中国医学   14081篇
肿瘤学   271669篇
  2021年   57199篇
  2019年   59513篇
  2018年   77095篇
  2017年   59210篇
  2016年   65795篇
  2015年   77928篇
  2014年   112374篇
  2013年   178236篇
  2012年   151442篇
  2011年   161084篇
  2010年   134403篇
  2009年   133217篇
  2008年   147196篇
  2007年   158316篇
  2006年   165300篇
  2005年   159425篇
  2004年   160411篇
  2003年   149574篇
  2002年   138700篇
  2001年   220716篇
  2000年   218967篇
  1999年   195084篇
  1998年   78594篇
  1997年   72452篇
  1996年   70480篇
  1995年   65869篇
  1994年   59826篇
  1993年   55430篇
  1992年   146853篇
  1991年   141509篇
  1990年   137090篇
  1989年   133358篇
  1988年   123272篇
  1987年   121160篇
  1986年   114878篇
  1985年   111867篇
  1984年   88879篇
  1983年   78010篇
  1982年   55473篇
  1981年   51045篇
  1980年   47702篇
  1979年   79955篇
  1978年   60457篇
  1977年   53177篇
  1976年   49259篇
  1975年   50946篇
  1974年   58110篇
  1973年   55653篇
  1972年   52281篇
  1971年   48797篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
大脑后动脉交通前段及其内穿支研究   总被引:2,自引:0,他引:2  
本文介绍Willis动脉环后半环大脑后动脉及其内穿支的显微解剖,大脑后动脉交通前段内穿支是脑深部的重要供血血管之一,100%的病例双侧具有该血管。  相似文献   
992.
993.
Noninvasive localized proton magnetic resonance spectroscopy (MRS) was used for differential diagnosis of a focal brain lesion in a 2.5-year-old girl. The clinical signs were a mild head tilt and neck pain. Magnetic resonance imaging (MRI) revealed a lesion in the right hemisphere of the cerebellum, but its nature remained obscure. In this lesion quantitative determinations of cerebral metabolites by fully relaxed, short-echo-time proton MRS revealed markedly lowered N-acetylaspartate (NAA) and pronounced elevations of choline-containing compounds (Cho) and myo-inositol (Ins), whereas metabolite concentrations in cortical gray matter and white matter were within normal ranges. The metabolite pattern of the lesion indicated loss of vital neuroaxonal tissue (low NAA) and enhanced glial proliferation (high Cho and Ins), which, together with the MRI morphology, suggested a brain tumor. The diagnosis was established by neurosurgical exploration and total extirpation of the tumor. Histology confirmed an astrocytoma (WHO II). After 2 weeks' recovery the child was discharged with no neurological signs.  相似文献   
994.
E R Broun  A Greist  G Tricot  R Hoffman 《JAMA》1990,264(11):1441-1443
Two patients with sideroblastic anemia secondary to zinc-induced copper deficiency absorbed excess zinc secondary to oral ingestion. The source of excess zinc was a zinc supplement in one case; in the other, ingested coins. In each case, the sideroblastic anemia was corrected promptly after removal of the source of excess zinc. These two cases emphasize the importance of recognizing this clinical entity, since the myelodysplastic features are completely reversible.  相似文献   
995.
Platelet activation factor (PAF)-, ADP and vasopressin-induced increments of platelet Ca2+ concentration were measured by quin-2 in 64 patients with essential hypertension and 16 normal donors. Basal concentration of free Ca2+ was 87 +/- 4 nM in donors, 106 +/- 5 nM in patients with labile hypertension (LH) and 122 +/- 6 nM in those with stable hypertension (SH) (p less than 0.01). PAF, ADP and vasopressin, added to platelets, increased [Ca]in by 448 +/- 58, 397 +/- 66, and 277 +/- 50 nM, respectively, in the donors, by 473 +/- 57, 479 +/- 54 and 195 +/- 32 nM, in LH patients, and by 607 +/- 85, 584 +/- 73 and 245 +/- 41 nM in SH patients. There were no significant variations between the three samples, using the ANOVA test. In 20 patients, whose both parents had essential hypertension, [Ca]in increment was 738 +/- 8 nM for PAF, 682 +/- 90 nM for ADP, and 320 +/- 61 nM for vasopressin. In 19 patients, who admitted to no essential hypertension in the family, these parameters were significantly lower: 310 +/- 40 nM for PAF, 389 +/- 61 nM for ADP, and 147 +/- 26 nM for vasopressin. The demonstrated changes may be making an important contribution to the maintenance of elevated vascular tone and provide an evidence in favor of a genetically-predetermined EH variety.  相似文献   
996.
A prognosis of patients with a curative resected advanced cancer of the lower gastric region was worse than that of the other region of the stomach. The 5 year survival rate was only 47.3%. One of the main reasons was that a rate of lymph node recurrence was higher. In this point of view, we studied on lymphatic flow of the lower gastric region using an activated carbon particle (CH40). Lymph nodes were stained black soon after the injection of CH40 into the lower gastric wall at laparotomy. The black stained rate of an each regional lymph node was as follows. 3. 58%, 4. 17%, 5. 50%, 6. 25%, 1. 21%, 7. 58%, 8. 83%, 9. 58%, 11. 17% and 12. 33% in case of injection into the greater curvature and and 4. 31%, 6. 100%, 8. 25%, 9. 25%, 14V and 56% in case of injection into the lesser curvature. The stained rate was relatively high in 12 and 14V lymph node which we had not routinely dissected. The rates of lymph nodes stained black were related to those of cancer metastasis. The results suggest that lymphadenectomy of 12 for the cancer at the lesser curvature and that of 14V for the cancer at the greater curvature might make a prognosis of lower gastric cancer better.  相似文献   
997.
998.
The role of caffeine or coffee in causing or promoting the incidence of serious disease is equivocal. Two design factors may account for the discrepancies in reported findings on the effects of coffee drinking: (a) imprecision of measurement and (b) confounding variables. A study of 2,714 white U.S. adults disclosed that, of 32 risk factors analyzed by linear and logistic regression, only sex and cigarette smoking were found to be important potential confounders of caffeine and coffee intake. Partial R2 values of the other 30 risk factors were relatively small and were inconsistent for each sex. It is unlikely that any of these factors could explain any of the reported associations between caffeine or coffee consumption and certain diseases. However, certain weak associations with caffeine or coffee intake should be included in the study design when they are known to be risk factors of a disease under investigation. These factors for men are dietary fat intake, vitamin C intake, and body mass index; and for women are vitamin use, alcohol intake, stress, and perceived health status.  相似文献   
999.
1000.
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