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   5873篇
  免费   284篇
  国内免费   40篇
耳鼻咽喉   38篇
儿科学   113篇
妇产科学   107篇
基础医学   564篇
口腔科学   133篇
临床医学   365篇
内科学   1525篇
皮肤病学   147篇
神经病学   437篇
特种医学   194篇
外科学   1054篇
综合类   19篇
一般理论   1篇
预防医学   136篇
眼科学   99篇
药学   271篇
中国医学   13篇
肿瘤学   981篇
  2023年   38篇
  2022年   54篇
  2021年   131篇
  2020年   87篇
  2019年   101篇
  2018年   148篇
  2017年   129篇
  2016年   146篇
  2015年   136篇
  2014年   176篇
  2013年   206篇
  2012年   378篇
  2011年   405篇
  2010年   246篇
  2009年   239篇
  2008年   356篇
  2007年   410篇
  2006年   370篇
  2005年   373篇
  2004年   382篇
  2003年   334篇
  2002年   370篇
  2001年   89篇
  2000年   85篇
  1999年   64篇
  1998年   67篇
  1997年   57篇
  1996年   57篇
  1995年   40篇
  1994年   29篇
  1993年   32篇
  1992年   51篇
  1991年   29篇
  1990年   41篇
  1989年   40篇
  1988年   30篇
  1987年   21篇
  1986年   17篇
  1985年   25篇
  1984年   16篇
  1983年   15篇
  1982年   12篇
  1981年   15篇
  1980年   17篇
  1979年   23篇
  1978年   14篇
  1977年   11篇
  1976年   13篇
  1971年   13篇
  1968年   7篇
排序方式: 共有6197条查询结果,搜索用时 46 毫秒
61.
It has been shown previously that soluble material extracted from Pasteurella multocida P-1059 by a 2.5% NaCl solution protects turkeys from generalized septicemia at a subsequent challenge exposure to the organism. In the present study, a protective antigen was purified from the crude soluble material by chromatographic methods. Four protein peaks were obtained by gel filtration with Sephadex G-200. The protective antigen was detected only in the first peak fraction, which contained a substantial amount of carbohydrate. The peak 1 fraction was adsorbed onto DEAE-cellulose and eluted by a linear gradient of NaCl. Fractions corresponding to a single protein peak were pooled and passed through an immunoadsorbent column to remove any possible serum component originating from the growth medium. The purified antigen had a carbohydrate/protein ratio of 1.5 and formed a single precipitin line with rabbit antiserum against the crude material in gel diffusion and immunoelectrophoresis analyses. The antigen produced antibodies in rabbits and turkeys which formed a single precipitin line against the crude material. Upon sodium dodecyl sulfate-polyacryl-amide gel electrophoresis, the purified antigen showed three protein bands, corresponding to molecular weights of 44,000, 31,000, and 25,000, and one carbohydrate band. The carbohydrate band did not correspond to any of the three protein bands. Upon isoelectric focusing gel analysis, the purified antigen showed two bands (pI = 3.5 to 4.0 and 4.5 to 5.5), but the two bands were antigenically identical by isoelectric focusing crossed immunoelectrophoresis. The 50% protective dose of the purified antigen was between 10 and 50 μg of protein in trials where two doses were given at 14-day intervals to 10- to 20-week-old turkeys.  相似文献   
62.
Urinary 1-microglobulin (U-A1M) was measured in healthy term infants on days 1, 4, 7, 14, 28, 90 and 180 of life. U-A1M was high until day 14 and declined thereafter. It was significantly correlated with urinary 2-microglobulin (U-B2M) throughout the study, but not with serum A1M on days 1 or 7. Similar to U-B2M, U-A1M in the clinically stable term infants with intrauterine growth retardation (n=4–7) was not elevated on days 1–7. In the sick infants who needed immediate resuscitatio at birth (n=4–8), U-A1M as well as U-B2M was high on days 1–7 and then decreased to normal levels, suggesting that U-A1M can be used as a sensitive marker of acute proximal tubular damage and its recovery. These observations indicate that U-A1M is a useful index of proximal tubular function in early infancy.  相似文献   
63.
64.
65.
Recombinant human ribonuclease 1 (RNasel) was chemically linked to recombinant human epidermal growth factor (EGF). The cytotoxicity of this conjugate was assayed using MTT assay. The EGF-RNase conjugate showed dose-dependent cytotoxicity against breast and squamous cell carcinomas overexpressing the EGF receptor (EGFR). The cytotoxicity of the conjugate correlated positively with the level of EGFR expression by each cell line. These results suggest that the EGF-RNase conjugate is a more effective anticancer agent with less immunogenicity and toxicity than conventional chimeric breast cancer toxins.  相似文献   
66.
Summary A simple qualitative method for identification of seminal stains based on a high activity of -glutamyltransferase (-GTP) in human semen is described. It employs the release of -naphthylamine from N--glutamyl--naphthylamide by the -GTP action; -naphthylamine couples with Fast Garnet GBC salt to produce a strong brownish-red color. The data on its simplicity, specificity, and stability show that the present method is suitable for medicolegal examination of seminal stains as a preliminary test.  相似文献   
67.
The possibility of radiographically diagnosing carcinoma with submucosal involvement (invasive carcinoma) is discussed based on 119 invasive carcinomas of the large bowel that had been treated surgically and colonoscopically over a period of 9 years (1989—1997) at the Cancer Institute Hospital in Tokyo. Of these lesions, 38 were superficial-type invasive carcinoma, accounting for 31.9% (38/119) of all invasive colorectal carcinomas, including 36 lesions (94.7%, 36/38) of types IIa and IIa+IIc and 2 lesions (5.3%, 2/38) of type IIc+IIa. No pure type IIc was seen. The radiographic images obtained were correlated with macroscopic findings and analyzed in terms of visualization of the lesion's contour, central depression, converging folds, and basal indentation. A definitive diagnosis of superficial invasive carcinoma can be made radiographically if a lesion measures 10 mm and reveals moderate to severe basal indentation in a complete or nearly complete profile radiographic image. Attention should be paid to the presence of superficial-type advanced carcinomas measuring 10 mm or less, which is not infrequently experienced in Japan. Polypoid invasive carcinoma can be definitively diagnosed in the same way with much more certainty than can the superficial type because few polypoid advanced carcinomas are less than 20 mm. The size and the radiographic sign of the basal indentation are the most important indicators for the diagnosis of invasive carcinoma. E-pub: 27 July 2000  相似文献   
68.
We investigated the biological effect of combining carbon-beam and X-ray in vitro. The results showed that when we employed Gray equivalent as the indication of therapeutic dose, the effects could be explained with simple additive way in the treatment plan. This fact provides important information about the combined therapy of carbon-beam and X-ray.  相似文献   
69.
70.
Vaquero J  Zurita M  Coca S  Oya S  Morales C 《Surgical neurology》2000,54(3):229-34; discussion 234
BACKGROUND: Keeping in mind that oligodendrogliomas have unpredictable biological behavior, the aim of this study is to investigate the prognostic significance of VEGF expression and microvessel density in a homogeneous series of low-grade oligodendrogliomas. METHODS: For this study 36 patients with a low-grade oligodendroglioma treated by surgical resection and radiotherapy were selected. At the time of surgery, in all cases the Karnofsky Performance Scale (KPS) score was more than 70, and the study of the resected tumor disclosed a Ki-67/MIB-1 labeling index (MBI-1 LI) less than 1%. In this homogeneous series, immunohistochemical studies were performed using monoclonal antibodies against VEGF in order to study the expression of this cytokine, and against vascular endothelial CD-34 antigen, in order to identify microvessels. RESULTS: Our results show that in contrast to low-grade astrocytomas, low-grade oligodendrogliomas lacked immunoreactive VEGF. Oligodendrogliomas with low vascular density (less than 20 microvessels per microscopical field, at 200 x) or high vascular density (more than 100 microvessels per field, at 200 x) were identified, but this factor had no influence on the survival rate of patients. On the other hand, analysis of the present series showed that clinical factors, such as age or extent of surgical resection, were not significantly associated with survival. CONCLUSIONS: In contrast to low-grade astrocytomas, the angiogenesis score of low-grade oligodendrogliomas (counting the number of microvessels in tumor tissue) adds little information to help predict tumor behavior.  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