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   99866篇
  免费   7127篇
  国内免费   321篇
耳鼻咽喉   1273篇
儿科学   2563篇
妇产科学   2313篇
基础医学   12468篇
口腔科学   2064篇
临床医学   9749篇
内科学   21742篇
皮肤病学   1071篇
神经病学   8656篇
特种医学   3401篇
外国民族医学   3篇
外科学   16326篇
综合类   1401篇
现状与发展   1篇
一般理论   75篇
预防医学   7890篇
眼科学   2648篇
药学   6367篇
中国医学   148篇
肿瘤学   7155篇
  2023年   365篇
  2022年   582篇
  2021年   1647篇
  2020年   881篇
  2019年   1591篇
  2018年   1909篇
  2017年   1407篇
  2016年   1555篇
  2015年   1840篇
  2014年   2729篇
  2013年   4332篇
  2012年   6199篇
  2011年   6473篇
  2010年   3630篇
  2009年   3356篇
  2008年   6152篇
  2007年   6840篇
  2006年   6530篇
  2005年   6684篇
  2004年   6505篇
  2003年   6125篇
  2002年   6125篇
  2001年   797篇
  2000年   559篇
  1999年   778篇
  1998年   1289篇
  1997年   1141篇
  1996年   963篇
  1995年   967篇
  1994年   845篇
  1993年   743篇
  1992年   568篇
  1991年   518篇
  1990年   451篇
  1989年   465篇
  1988年   435篇
  1987年   452篇
  1986年   446篇
  1985年   498篇
  1984年   708篇
  1983年   754篇
  1982年   978篇
  1981年   915篇
  1980年   866篇
  1979年   450篇
  1978年   529篇
  1977年   580篇
  1976年   490篇
  1975年   428篇
  1974年   340篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
Conclusions  Noninvasive imaging of neurohumoral upregulation in remodeled myocardium suggests that an imaging strategy can be developed for predicting the rate of remodeling and likelihood of HF development. This should allow a more judicious use of neurohumoral antagonists especially in subjects who do not have manifest HF.74 In others specific targeted imaging may allow timely selection of individualized treatment strategies and ensure optimization of therapeutic intervention. Similar to ACE and AII receptors, multiple other targets in the hormonal cascades can identify the likelihood of adverse and favorable remodeling.74  相似文献   
123.
A novel injectable scaffolding matrix (E-Matrix) has been developed to accelerate wound healing in diabetic foot ulcers. This porcine collagen-derived matrix is designed to mimic tertiary embryonic connective tissue and to stimulate fetal wound repair mechanisms including angiogenesis. In vitro and animal studies have indicated a beneficial effect on tissue growth and an acceptable safety profile. In this report, we describe the initial use of this product in a pilot study of six humans with chronic nonhealing diabetic foot ulcers. A dramatic initial response to injection was seen, with an average wound size reduction of 72% 2 weeks after injection. Randomized trials are underway to define the potential benefit of this new treatment modality for diabetic foot ulcers.  相似文献   
124.
Ultrasensitive bright field in situ hybridization assays using enzyme metallography (EnzMet) have been developed and validated, but little is known regarding the applicability of EnzMet for immunophenotypic detection of protein via IHC. Superior resolution via discrete metallographic deposits offers the potential for enhancing high-resolution immunophenotyping. Using high-complexity tissue microarrays (TMAs), 88 common solid tumors were evaluated by automated EnzMet (Nanoprobes and Ventana). Targets were chosen to assess the ability of EnzMet to specifically localize encoded antigens in the nucleus (estrogen receptor), cytoplasm (cytokeratins), and cytoplasmic membrane (HER2) in TMAs. Results were compared with conventional IHC diaminobenzidine (DAB) immunostaining. There was full concordance between the EnzMet and conventional IHC results. Furthermore, the EnzMet reaction products did not appreciably diffuse, were dense and sharply defined, and provided excellent high-resolution differentiation of cellular compartments in paraffin sections for the nuclear, cytoplasmic, and cell membrane-localized antigens evaluated. The higher density of elemental silver deposited during enzyme metallography permitted evaluation of core immunophenotypes at a relatively low magnification, allowing more tissue to be screened in an efficient manner. This preliminary study shows the utility of using enzyme metallography for high-resolution immunophenotyping in TMAs.  相似文献   
125.
A previously reported paradigm in which rats run down a runway for food reward followed by morphine injection was analyzed to assess the utility of the paradigm in studies of opiate reinforcement. One experiment replicated the original report that post-trial morphine caused both an increase in runway speed and a decrease in food consumption (taste aversion) over successive trials, and showed in addition that the increase in runway speed did not occur as a result of food deprivation alone, but required the animals to have consumed food in the goal box. A second study using the quaternary opiate antagonist methyl naltrexone to block the peripheral effects of morphine suggested that the increase in runway speed has a peripheral locus while the taste aversion has a central one. A third experiment in which morphine was microinjected into either the lateral ventricle or the ventral tegmental area supported these observations, in that intracranial morphine failed to result in an increased runway speed, but did produce taste aversion after microinjection into either site. These findings also suggest that the increase in runway speed caused by post-trial morphine in this experiment has a peripheral locus of effect, which is probably distinct from the central effect that supports morphine self-administration and conditioned place preference. Offprint requests to: W.A.CorrigallThe views expressed in this publication are those of the authors and do not necessarily reflect those of the Addiction Research Foundation  相似文献   
126.

Background  

Colorectal cancer, if detected early, has greater than 90% 5-year survival. However, survival has been shown to vary across racial/ethnic groups in the United States, despite the availability of early detection methods.  相似文献   
127.
Background: Bupivacaine retards myocardial acidosis during ischemia. The authors measured function of rat isolated hearts after prolonged storage to determine whether bupivacaine improves cardiac protection compared with standard cardioplegia alone.

Methods: After measuring cardiac function on a Langendorff apparatus, hearts were perfused with cardioplegia alone (controls), cardioplegia containing 500 [mu]m bupivacaine, or cardioplegia containing 2 mm lidocaine; were stored at 4[degrees]C for 12 h; and were then reperfused. Heart rate and left ventricular developed pressures were measured for 60 min. Maximum positive rate of change in ventricular pressure, oxygen consumption, and lactate dehydrogenase release were also measured.

Results: All bupivacaine-treated, four of five lidocaine-treated, and no control hearts beat throughout the 60-min recovery period. Mean values of heart rate, left ventricular developed pressure, maximum positive rate of change in ventricular pressure, rate-pressure product, and efficiency in bupivacaine-treated hearts exceeded those of the control group (P < 0.001 at 60 min for all). Mean values of the lidocaine group were intermediate. Oxygen consumption of the control group exceeded the other groups early in recovery, but not at later times. Lactate dehydrogenase release from the bupivacaine group was less than that from the control group (P < 0.001) but did not differ from baseline.  相似文献   

128.
129.
Akt, a Serine/Threonine protein kinase, mediates growth factor-associated cell survival. Constitutive activation of Akt (phosphorylated Akt, P-Akt) has been observed in several human cancers, including lung cancer and may be associated with poor prognosis and chemotherapy and radiotherapy resistance. The clinical relevance of P-Akt in non-small cell lung cancer (NSCLC) is not well described. In the present study, we examined 82 surgically resected snap-frozen and paraffin-embedded stage I to IIIA NSCLC samples for P-Akt and Akt by Western blotting and for P-Akt by immunohistochemistry. P-Akt protein levels above the median, measured using reproducible semiquantitative band densitometry, correlated with a favorable outcome (P = 0.007). Multivariate analysis identified P-Akt as a significant independent favorable prognostic factor (P = 0.004). Although associated with a favorable prognosis, high P-Akt levels correlated with high tumor grade (P = 0.02). Adenocarcinomas were associated with low P-Akt levels (P = 0.039). Akt was not associated with either outcome or clinicopathologic variables.Cytoplasmic (CP-Akt) and nuclear (NP-Akt) P-Akt tumor cell staining was detected in 96% and 42% of cases, respectively. Both CP-Akt and NP-Akt correlated with well-differentiated tumors (P = 0.008 and 0.017, respectively). NP-Akt also correlated with nodal metastases (P = 0.022) and squamous histology (P = 0.037).These results suggest P-Akt expression is a favorable prognostic factor in NSCLC. Immunolocalization of P-Akt, however, may be relevant as NP-Akt was associated with nodal metastases, a known poor prognostic feature in this disease. P-Akt may be a potential novel therapeutic target for the management of NSCLC.  相似文献   
130.
When you treat the congenital absence of mandibular second premolars by extracting the residual deciduous second molar and closing the space, you run the risk of flattening facial fullness, especially in patients with nonextraction features--diminished facial fullness, absence of crowding, and reduced tooth size. This challenge is heightened by the increased likelihood that these features will occur in patients who have agenesis. This article describes a new approach that has been shown to minimize such a loss of anchorage. The technique is called hemisection and involves buccolingual sectioning of the second deciduous molar, followed by removal of its distal half. As necessary, the mesial half is also removed, and space closure can be completed. The advantages, philosophy, and technique are discussed in detail.  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