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   1700915篇
  免费   123980篇
  国内免费   3810篇
耳鼻咽喉   21786篇
儿科学   55738篇
妇产科学   46235篇
基础医学   241795篇
口腔科学   48827篇
临床医学   151640篇
内科学   335277篇
皮肤病学   38705篇
神经病学   131762篇
特种医学   64018篇
外国民族医学   242篇
外科学   257916篇
综合类   38980篇
现状与发展   4篇
一般理论   536篇
预防医学   124596篇
眼科学   40414篇
药学   123992篇
  8篇
中国医学   4490篇
肿瘤学   101744篇
  2021年   12980篇
  2019年   13686篇
  2018年   20133篇
  2017年   15358篇
  2016年   16753篇
  2015年   19106篇
  2014年   26408篇
  2013年   38249篇
  2012年   53175篇
  2011年   55843篇
  2010年   33020篇
  2009年   30920篇
  2008年   51897篇
  2007年   55201篇
  2006年   55647篇
  2005年   52881篇
  2004年   50996篇
  2003年   48422篇
  2002年   46606篇
  2001年   91854篇
  2000年   93650篇
  1999年   77004篇
  1998年   19775篇
  1997年   17305篇
  1996年   17424篇
  1995年   16768篇
  1994年   15313篇
  1993年   14086篇
  1992年   57414篇
  1991年   55296篇
  1990年   52992篇
  1989年   50775篇
  1988年   46152篇
  1987年   44955篇
  1986年   42240篇
  1985年   40001篇
  1984年   29359篇
  1983年   24915篇
  1982年   13912篇
  1979年   25535篇
  1978年   17582篇
  1977年   14913篇
  1976年   13882篇
  1975年   14569篇
  1974年   17637篇
  1973年   16946篇
  1972年   15677篇
  1971年   14453篇
  1970年   13435篇
  1969年   12518篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVE: To assess the impact of activity restriction (AR) on the incidence of preterm birth in women treated for preterm labor testing negative for fetal fibronectin (fFN). STUDY DESIGN: Women who were diagnosed with preterm labor and tocolyzed with magnesium sulfate were concurrently screened with fFN for the purpose of subsequent management. Included were consenting patients with negative fFN, gestational age 23 0/7-33 6/7 weeks, cervical dilation < or =3 cm, and minimal vaginal bleeding. Patients were randomized to AR or no AR. Primary study outcome was incidence of preterm delivery and interval from randomization to delivery. RESULTS: A total of 73 women with negative fFN were randomized (36 with AR, 37 without AR). The overall preterm birth rate was 40%, with 44.4% of patients with AR and 35.1% of patients without AR delivering preterm, p=0.478. CONCLUSION: Maternal AR did not impact pregnancy outcome. The incidence of preterm birth in symptomatic women testing fFN negative was higher than previously reported.  相似文献   
992.
Bone and joint sepsis   总被引:1,自引:0,他引:1  
  相似文献   
993.
Abstract: We have designed and synthesized a new series of azapeptides which act as potential inhibitors of cathepsin B and/or cathepsin K. Their structures are based upon the inhibitory sites of natural cysteine protease inhibitors, cystatins. For the synthesized azapeptides, the equilibrium constants for dissociation of inhibitor–enzyme complex, Ki, were determined. Comparison of these values indicated that all of the azainhibitors act much stronger toward cathepsin B. Z‐Arg‐Leu‐His‐Agly‐Ile‐Val‐OMe ( 7 ) proved to be approximately 500 times more potent for cathepsin B than for cathepsin K. To be able to explain the obtained experimental values we used the molecular dynamics procedures to analyze the interactions between cathepsin B and compound 7 . We also determined the structure of the most potent and selective cathepsin B azainhibitor by means of NMR studies and theoretical calculations. In this report, we describe SAR studies of azapeptide inhibitors indicating the influence of the conformational flexibility of the examined compounds on inhibition of cathepsins B and K.  相似文献   
994.
The article presents an original method of laparoscopic anti-reflux surgery, immediate and long-term results of the treatment of 132 patients with esophageal opening hernia. It also describes the analysis of the life quality of patients with the gastroesophageal reflux disease before and after the surgery.  相似文献   
995.
Among many conventional techniques, nuclear techniques have shown to be faster, more reliable, and more effective in detecting explosives. In the present work, neutrons from a 5 Ci Am-Be neutron source being in water tank are captured by elements of soil and landmine (TNT), namely (14)N, H, C, and O. The prompt capture gamma-ray spectrum taken by a NaI (Tl) scintillation detector indicates the characteristic photo peaks of the elements in soil and landmine. In the high-energy region of the gamma-ray spectrum, besides 10.829 MeV of (15)N, single escape (SE) and double escape (DE) peaks are unmistakable photo peaks, which make the detection of concealed explosive possible. The soil has the property of moderating neutrons as well as diffusing the thermal neutron flux. Among many elements in soil, silicon is more abundant and (29)Si emits 10.607 MeV prompt capture gamma-ray, which makes 10.829 MeV detection difficult. The Monte Carlo simulation was used to adjust source-target-detector distances and soil moisture content to yield the best result. Therefore, we applied MCNP4C for configuration very close to reality of a hidden landmine in soil.  相似文献   
996.
997.
998.
BACKGROUND: Alternaria alternata is one of the most important allergenic fungi worldwide. Mannitol dehydrogenase (MtDH) has previously been shown to be a major allergen of Cladosporium herbarum and cross-reactivity has been demonstrated for several fungal allergens. OBJECTIVE: The present study's objective was to clone the MtDH from an A. alternata cDNA library, express and purify the recombinant non-fusion protein and test its IgE-binding properties. Methods A cDNA library prepared from A. alternata hyphae and spores was screened for mannitol dehydrogenase by DNA hybridization with the radioactively labelled C. herbarum homologue as a probe. The resulting clone was sequenced and heterologously expressed in Escherichia coli as a recombinant non-fusion protein, which was purified to homogeneity and analysed for its IgE-binding capacity. RESULTS: The coding sequence of the full-length cDNA clone comprises 798 bp encoding a protein with a molecular mass of 28.6 kDa and a predicted pI of 5.88. Protein sequence analysis revealed an identity of 75% and a homology of 86% between the MtDHs of A. alternata and C. herbarum. The functional mannitol dehydrogenase was expressed in the E. coli strain BL21(DE3) transformed with the vector pMW172 and purified to homogeneity. The enzyme catalyses the NADPH-dependent conversion of d-fructose to d-mannitol. In IgE-ELISA and immunoblots, MtDH is recognized by 41% of A. alternata-allergic patients. In vivo immunoreactivity of the recombinant MtDH was verified by skin prick testing. Finally, inhibition-ELISA experiments confirmed cross-reactivity between the MtDHs of A. alternata and C. herbarum. CONCLUSION: Mannitol dehydrogenase (Alt a 8) represents an important new allergen of the ascomycete A. alternata that might be suitable for improving diagnostic and therapeutic procedures.  相似文献   
999.
1000.

Background  

Acromioclavicular injuries are common in sports medicine. Surgical intervention is generally advocated for chronic instability of Rockwood grade III and more severe injuries. Various methods of coracoclavicular ligament reconstruction and augmentation have been described. The objective of this study is to compare the biomechanical properties of a novel palmaris-longus tendon reconstruction with those of the native AC+CC ligaments, the modified Weaver-Dunn reconstruction, the ACJ capsuloligamentous complex repair, screw and clavicle hook plate augmentation.  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