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   456216篇
  免费   31944篇
  国内免费   8039篇
耳鼻咽喉   5987篇
儿科学   9060篇
妇产科学   11255篇
基础医学   63060篇
口腔科学   13088篇
临床医学   40643篇
内科学   89858篇
皮肤病学   9481篇
神经病学   31479篇
特种医学   16868篇
外国民族医学   135篇
外科学   68506篇
综合类   20384篇
现状与发展   22篇
一般理论   83篇
预防医学   22326篇
眼科学   12342篇
药学   39076篇
  68篇
中国医学   6300篇
肿瘤学   36178篇
  2022年   4211篇
  2021年   6633篇
  2020年   4571篇
  2019年   5523篇
  2018年   7464篇
  2017年   5887篇
  2016年   6049篇
  2015年   7713篇
  2014年   10280篇
  2013年   11390篇
  2012年   15969篇
  2011年   16649篇
  2010年   10155篇
  2009年   8857篇
  2008年   13575篇
  2007年   14258篇
  2006年   14295篇
  2005年   13234篇
  2004年   11453篇
  2003年   10967篇
  2002年   10193篇
  2001年   29779篇
  2000年   30298篇
  1999年   25481篇
  1998年   6359篇
  1997年   5448篇
  1996年   4762篇
  1995年   4361篇
  1994年   3848篇
  1993年   3301篇
  1992年   16547篇
  1991年   15217篇
  1990年   14550篇
  1989年   14302篇
  1988年   12874篇
  1987年   12288篇
  1986年   11286篇
  1985年   10476篇
  1984年   6999篇
  1983年   5662篇
  1982年   2750篇
  1979年   5532篇
  1978年   3366篇
  1977年   2983篇
  1975年   2652篇
  1974年   3089篇
  1973年   2882篇
  1972年   2836篇
  1971年   2784篇
  1969年   2559篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
2-Cyclohexene-1-one (CHX) dose-dependently caused the elevation of blood glucose levels in both fed and fasted mice. Adrenalectomy considerably prevented the elevated blood glucose with CHX, and plasma adrenaline assays revealed about a three- to fifteen-fold rise after CHX treatment. These findings indicate that the CHX-induced hyperglycemia may be largely mediated by adrenaline released from the adrenal medulla.  相似文献   
992.
The basis for the antitumor activities of the exocyclic amino nucleosides 4-amino-(ARPP) and 4-methoxy-8-(D-ribofuranosylamino)pyrimido[5,4-d]pyrimidine (MRPP) was investigated. The primary target of these nucleosides appeared to be 5-phospho-alpha-D-ribofuranose-1-pyrophosphate (PRPP) synthetase. MRPP-5'-monophosphate was a competitive inhibitor (Ki = 40 microM) of the activation of this enzyme by the cofactor inorganic phosphate (K alpha = 2.2 mM). Consequently, ARPP and MRPP treatment of WI-L2 cultures rapidly inhibited both de novo pyrimidine and purine synthesis as well as the nucleotide salvage reactions dependent on PRPP, ARPP or MRPP treatment completely prevented [14C]bicarbonate incorporation into acid-soluble pyrimidine and purine nucleotides. The rate of salvage of [8-14C]hypoxanthine to form IMP was decreased by 85%. Treatment of cells with these agents caused a 50% reduction in the steady-state level of PRPP. When the capacity of the treated cells for sustained synthesis of PRPP was examined by adenine incorporation, the rate of adenine uptake was inhibited by greater than 50%. In vivo treatment of BDF1 mice with a single dose of ARPP (173 mg/kg) or MRPP (62 mg/kg) extended the mean life span of the mice, which had been inoculated intraperitoneally 1 day earlier with 1 x 10(6) L1210 murine leukemia cells, by 62 and 82% respectively. These studies indicate that MRPP and ARPP inhibit PRPP synthetase, and that PRPP synthetase may be a viable target in the development of certain antitumor agents.  相似文献   
993.
We tested 2 prototypes of an operating fiberoptic nephroureteroscope, measuring 3.5 and 4.5 mm. in diameter, that have an adequate working channel for auxiliary instruments and irrigation. Difficulty in passing the fiberscope through the ureteral orifice was overcome by dilation with balloon and polytetrafluoroethylene (Teflon) dilators. Our initial trial for stone retrieval under fiberscopic control was performed on 21 patients with upper ureteral and renal calculi. A stone was removed successfully in 15 of the 21 patients (71 per cent). After electrohydraulic lithotripsy calculi were extracted successfully in 9 of 11 patients (82 per cent). Three patients suffered ureteral perforation. The fiberscope was especially helpful when an upper ureteral stone moved back to the kidney during stone manipulation.  相似文献   
994.
Optically pure (+)- and (-)-trans-stilbene oxide (TSO) enantiomers were administered to immature male Sprague-Dawley rats. (+)-TSO was the more potent inducer of liver microsomal cytochrome P-450-dependent monooxygenases. The greater potency of (+)-TSO may be explained on the basis of stereoselective metabolism since a far greater concentration of TSO was found in liver microsomes of (+)-TSO-treated rats. Furthermore, of the enzymes known to metabolize TSO, cytosolic epoxide hydrolase turned over the (-)-TSO enantiomer at a faster rate, consistent with the greater persistence of the (+)-enantiomer. Although this report is of chiral effects in potency of enzyme induction, stereoselective metabolism (i.e. disposition) rather than inherent structural characteristics (recognition) may be responsible for these effects.  相似文献   
995.
A case of generalized eruptive histiocytoma (GEH) was evaluated and examined histopathologically and ultrastructurally. A 24-year-old male had an episode of high fever and drug-induced eruption prior to the appearance of multiple skin lesions. Uniform, red to dark-red papular lesions appeared on his cheeks and then became generalized. The lesions were composed of a massive dermal infiltrate of histiocytes, which had oval nuclei and amphophilic cytoplasm. The cytoplasm contained unique annular structures, myeloid bodies and vacuoles. The specificity of these structures is as yet unknown. Reactive stimulation rather than neoplastic proliferation may be a causative factor in GEH.  相似文献   
996.
The promoting effect of the Chinese medicinal herb, Wikstroemia chamaedaphne and Tung oil extracts (WC and HHPA) on carcinoma of uterine cervix induced by HSV-2 or MCA in mice was studied. The results showed that WC and HHPA extracts were not carcinogenic themselves. After carcinogen HSV-2 and MCA treatment, WC and HHPA were added separately. The inducing rates by HSV-2 increased from 7.4% to 21.1% and 26.3%, those by MCA increased from 56.5% to 82.8% and 84.4%. There was a significant difference between the combined groups and groups with HSV-2 or MCA only. The experimental results suggest that these two kinds of extracts play a promoting effect on carcinogenesis. The relation between the carcinogenesis of uterine cervix or nasopharynx and WC or HHPA extracts is discussed.  相似文献   
997.
A 44-year-old female with Cushing's disease associated with a pituitary macroadenoma was treated with cyproheptadine, 24 mg per day, after partial surgical resection of the tumor. A large residual tumor remained. There was no clear suppression of serum and urinary cortisol during therapy, but both levels rose markedly to beyond pre cyproheptadine levels, on withdrawal of the drug. This is the first report on the use of cyproheptadine in Cushing's disease associated with a pituitary macroadenoma. The response in this patient indicates an influence of cyproheptadine on ACTH secretion by the macroadenoma.  相似文献   
998.
999.
孙风华 《中国保健》2007,15(10):9-10
目的研究理想的分娩镇痛方法及护理.方法根据疼痛的情况,在设定的范围的内持续追加麻醉药,以阻断T10~12和S2~4节段的神经传导.结果理想的理想分娩阵痛能减免产妇分娩疼痛.结论阵痛分娩可消除产妇精神紧张、恐惧、疲惫及缺乏自信和不良刺激等因素.  相似文献   
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