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   90442篇
  免费   10651篇
  国内免费   4848篇
耳鼻咽喉   941篇
儿科学   1656篇
妇产科学   963篇
基础医学   5481篇
口腔科学   2004篇
临床医学   12072篇
内科学   9430篇
皮肤病学   1220篇
神经病学   2968篇
特种医学   3805篇
外国民族医学   1篇
外科学   7988篇
综合类   21647篇
现状与发展   13篇
一般理论   5篇
预防医学   12050篇
眼科学   1158篇
药学   9173篇
  119篇
中国医学   8482篇
肿瘤学   4765篇
  2024年   489篇
  2023年   1453篇
  2022年   2795篇
  2021年   3619篇
  2020年   3294篇
  2019年   1822篇
  2018年   2287篇
  2017年   2860篇
  2016年   2334篇
  2015年   3896篇
  2014年   4816篇
  2013年   6281篇
  2012年   7720篇
  2011年   8089篇
  2010年   7414篇
  2009年   6766篇
  2008年   6576篇
  2007年   6256篇
  2006年   5515篇
  2005年   4396篇
  2004年   3113篇
  2003年   2577篇
  2002年   2095篇
  2001年   1976篇
  2000年   1375篇
  1999年   737篇
  1998年   495篇
  1997年   472篇
  1996年   469篇
  1995年   390篇
  1994年   306篇
  1993年   289篇
  1992年   291篇
  1991年   224篇
  1990年   220篇
  1989年   234篇
  1988年   242篇
  1987年   189篇
  1986年   192篇
  1985年   178篇
  1984年   142篇
  1983年   119篇
  1982年   93篇
  1981年   95篇
  1980年   69篇
  1979年   65篇
  1978年   50篇
  1977年   63篇
  1976年   49篇
  1971年   34篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
Mycoplasma infection was present in the fetuses from three spontaneous abortions and in one second-trimester newborn. Gross examination revealed in most cases a severely infected placenta and membranes, with a fetus of normal appearance. The fetal infection presumably followed placental involvement and appeared to have been acquired shortly prior to delivery. Genital mycoplasmas, Ureaplasma urealyticum or Mycoplasma hominis, were isolated from the placentas and the fetal tissues, and from the genital tracts of the mothers. Isolation of mycoplasmas from the liver indicated that bloodstream dissemination of these organisms occurred in the fetus. In the fetus, the pathologic changes were variable. Lesions were identified in the lung by scanning electron microscopy of the bronchial tree in two cases and were accompanied by interstitial pneumonia. An abnormally dilated left ventricle suggestive of cardiomyopathy was observed in one case.  相似文献   
105.
In vitro studies to analyse the pharmacology of histamine-induced dilatation of resistance vessels in rat hindquarters have been made. Histamine caused dose-dependent dilatation of resistance vessels over the concentration range 10–9 to 10–6 mol. Responses to histamine were antagonized by cimetidine but not by mepyramine. Dimaprit also caused vasodilatation. Responses to dimaprit were inhibited by cimetidine 10–6 to 10–5 M. A pA2 of 6.43 (6.11–6.75, 95% confidence limits) was calculated for cimetidine in the resistance vessels of the hindquarters.  相似文献   
106.
Objective To study the distribution and quantity of CD44VCD24- cells in breast cancer tissue and the cell lines,and as well as its correlation with the expression of various breast cancer markers and molecular subtyping of breast carcinoma.Methods The expression of CD44 / CD24,estrogen receptor,progesterone receptor,HER2,human estrogen-induced protein PS2,bcl-2 and nm23 in 60 cases of invasive ductal carcinoma of breast were studied by either single or double immunohistochemical staining.The co-expression of CD44 and CD24 in 3 breast cancer cell lines (MCF-7,MDA-MB-468,and MDA-MB- 231) was also examined.Results The quantity and distribution of CD44 + /CD24- cells varied greatly and no specific patterns were identified.The percentage of CD44 + /CD24- in breast cancer was 65%.The amount of CD44+/CD24- cells did not correlate with the age of patients,lymph node metastasis,tumor  size,molecular subtypes and expression of various breast cancer markers in breast carcinoma.The proportion of CD44+/CD24- cells in MCF-7,MDA-MB-468,and MDA-MB-231 cell lines was < 1%,5% and > 80% ,respectively.Conclusions CD44+ /CD24- cells are demonstrated in certain breast cancer tissues and cell lines.However,there is no relationship obtained between the quantity or the distribution of these cells and the molecular subtyping or the clinicopathologic parameters in breast cancer.  相似文献   
107.
Immunization with a recombinant form of the protective antigen (rPA) from Bacillus anthracis has been carried out with rhesus macaques. Rhesus macaques immunized with 25 mug or more of B. subtilis-expressed rPA bound to alhydrogel had a significantly increased immunoglobulin G (IgG) response to rPA compared with macaques receiving the existing licensed vaccine from the United Kingdom (anthrax vaccine precipitated [AVP]), although the isotype profile was unchanged, with bias towards the IgG1 and IgG2 subclasses. Immune macaque sera from all immunized groups contained toxin-neutralizing antibody and recognized all the domains of PA. While the recognition of the N terminus of PA (domains 1 to 3) was predominant in macaques immunized with the existing vaccines (AVP and the U.S. vaccine anthrax vaccine adsorbed), macaques immunized with rPA recognized the N- and C-terminal domains of PA. Antiserum derived from immunized macaques protected macrophages in vitro against the cytotoxic effects of lethal toxin. Passive transfer of IgG purified from immune macaque serum into naive A/J mice conferred protection against challenge with B. anthracis in a dose-related manner. The protection conferred by passive transfer of 500 mug macaque IgG correlated significantly (P = 0.003; r = 0.4) with the titers of neutralizing antibody in donor macaques. Subsequently, a separate group of rhesus macaques immunized with 50 mug of Escherichia coli-derived rPA adsorbed to alhydrogel was fully protected against a target dose of 200 50% lethal doses of aerosolized B. anthracis. These data provide some preliminary evidence for the existence of immune correlates of protection against anthrax infection in rhesus macaques immunized with rPA.  相似文献   
108.
目的:介绍抗人DR5单抗YM366EC-阿霉素结合物的制备及其细胞毒作用,以探讨YM366EC作为内源性导向载体的可能性。方法:采用氧化葡聚糖(Dex)T-40作为中介载体,联结抗人DR5YM366EC与阿霉素(ADR)制备交联物366EC-Dex-ADR,交联物中ADR与366EC的克分子比为71:1。经ELISA测定交联物的抗体活性大部分保持。MTT法体外测定其细胞毒性。结果:交联物对表达DR5受体的肿瘤细胞处理24小时的IC50是游离ADM的5倍,并且和肿瘤细胞DR5受体表达相关。结论:YM366EC具有良好的导向作用,结合物对肿瘤细胞有选择性杀伤作用。  相似文献   
109.
110.
A wireless power transfer system for endoscopic micro-robot operating at 36 kHz is presented in this paper. The issue of patient' s health and safety regarding exposure to the electromagnetic field is addressed. The specific absorption rate and current density can be used to investigate the electromagnetic influences on the biological tissues surrounded by the wireless power launching coil. In view of this purpose, the limited close-ound solenoid electromagnetic model is built, the relationship between the electric intensity and the specific absorption rate and current density is deduced, and the simulation experiments are done. Experimental results show that the values of SAR and current density related to different tissue catalogs are all very small and do not exceed their own limits respectively when the resonance frequency of operation is 36 kHz.  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