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   11215篇
  免费   1111篇
  国内免费   38篇
耳鼻咽喉   175篇
儿科学   347篇
妇产科学   210篇
基础医学   1458篇
口腔科学   97篇
临床医学   1401篇
内科学   2583篇
皮肤病学   111篇
神经病学   1119篇
特种医学   364篇
外科学   1893篇
综合类   120篇
一般理论   4篇
预防医学   855篇
眼科学   398篇
药学   590篇
中国医学   7篇
肿瘤学   632篇
  2023年   120篇
  2022年   211篇
  2021年   439篇
  2020年   224篇
  2019年   355篇
  2018年   430篇
  2017年   312篇
  2016年   346篇
  2015年   369篇
  2014年   475篇
  2013年   605篇
  2012年   915篇
  2011年   890篇
  2010年   460篇
  2009年   418篇
  2008年   675篇
  2007年   607篇
  2006年   566篇
  2005年   558篇
  2004年   493篇
  2003年   405篇
  2002年   361篇
  2001年   110篇
  2000年   87篇
  1999年   76篇
  1998年   70篇
  1997年   53篇
  1994年   36篇
  1992年   78篇
  1991年   56篇
  1990年   66篇
  1989年   55篇
  1988年   66篇
  1987年   90篇
  1986年   79篇
  1985年   70篇
  1984年   66篇
  1983年   61篇
  1982年   63篇
  1981年   52篇
  1980年   35篇
  1979年   55篇
  1978年   44篇
  1976年   42篇
  1975年   34篇
  1974年   47篇
  1973年   40篇
  1972年   45篇
  1971年   35篇
  1969年   35篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
SYNOPSIS
These experiments investigate thermographic patterns in the posterior cervical/thoracic (PCT) region of 530headache patients and 30 headache/injury-free volunteers. The study examines: The longitudinal persistence ofProximal and Distal patterns; three distinct midline patterns (PCT I, II, and III); and their correlation with diagnosis,injury, and pain.
Twenty-four (80%) of 30 randomly selected subjects displayed unchanged Proximal patterns at the meanobservation period of 5.5 months. PCT pattern fluctuations occurred in 13/30 (43.3%) subjects. The distinctivenessof each subject's Proximal and Distal patterns was verified by blind calling of thermogram pairs. Patternpersistence was validated with alcohol spray-Patterns were identical regardless of using a 0.5°C or 1.0°Ctemperature setting. Temperature settings of 1.0°C yielded more distinct Proximal and Distal patterns.
Chi square analysis determined that there was no significant difference in the number of PCT III patterns in theexperimental or control groups.
In conclusion, it appears that Proximal and Distal Patterns may be consistent over time and individually unique,but that PCT patterns fluctuate and, therefore, do not correlate with chronic headaches.  相似文献   
32.
33.
Secretory products of macrophages.   总被引:159,自引:29,他引:130       下载免费PDF全文
  相似文献   
34.
Background Acute cocaine poisoning is a common problem in the United States. Sedation with benzodiazepines is the standard treatment, but animal studies have suggested that ziprasidone is also protective.
Objectives To assess whether the combination of these two medications would offer more protection than either treatment alone.
Methods This was a randomized, blinded, placebo-controlled trial in CF-1 mice. The authors administered intraperitoneal injections of 2 mg/kg diazepam (group D), 4 mg/kg ziprasidone (group Z), the same dose of both drugs (group DZ), or saline 15 minutes before intraperitoneal administration of 105 mg/kg cocaine (an estimated lethal dose to 70%). The number of animals with seizures and apparent lethality over the following 30 minutes was recorded.
Results All treatments increased survival relative to placebo (relative risk: D = 2.6, Z = 2.3, DZ = 2.9) and decreased seizures (relative risk: D = 0.5, Z = 0.3, DZ = 0.02).
Conclusions This study suggests that diazepam and ziprasidone have efficacy for preventing lethality from cocaine poisoning in an animal model but that the combination offers little addition to either therapy alone. However, the combination may be more effective for prevention of cocaine-induced seizures.  相似文献   
35.
36.
Fresh bone marrow from 43 cases of myeloma and three cases of plasma cell leukaemia has been phenotyped both by indirect immune-rosetting and, on fixed cytospin preparations, by indirect immunofluorescence. Both clustered and unclustered B cell associated antibodies from the IIIrd International Workshop on Human Leucocyte Differentiation Antigens were used. The results confirm the lack of many pan-B antigens on the surface of myeloma plasma cells, i.e. CD19-23, 37, 39, w40. Strong surface reactivity is seen with CD38 antibodies and with one CD24 antibody (HB8). Weak reactions are sometimes obtained with CD9, 10 and 45R. On cytospin preparations CD37, 39 and w40 are sometimes weakly positive, and anti-rough endoplasmic reticulum antibodies are always strongly positive. Specific and surface-reacting antiplasma cell antibodies are still lacking.  相似文献   
37.
The immune response in steroid deficient mice   总被引:1,自引:0,他引:1       下载免费PDF全文
Adrenalectomy, gonadectomy and combined adrenalectomy—gonadectomy resulted in increased spleen weights, spleen cell counts and 19S plaque-forming cells following primary and secondary immunization of mice with SRBC when compared to controls. Plaque-forming cells of the 7S type in the spleen did not increase when measured on the eleventh day following the primary or the third day following secondary sensitization. Combined adrenalectomy—gonadectomy had a greater effect on spleen cell counts, spleen weights and plaque-forming cells in the primary and secondary response than either operation alone. Haemolysin titres were not significantly different between test and sham operated animals in the primary and secondary responses.

In the primary responses, it appears that the increase in spleen weight and cell count is responsible for the increase in 19S plaque-forming cells. The response to a second injection of SRBC demonstrated that 19S antibody-producing cells increased three-fold in steroid depleted mice above the control values. In the test animals the 19S antibody-producing cells of the spleen were relatively enriched above that of the controls.

  相似文献   
38.
BACKGROUND: The increased consumption of foods containing sesame seeds is paralleled by an increase in reported sesame-induced allergic reactions. OBJECTIVE: This study aimed at identifying and characterizing the linear B-cell epitopes of the 14-kd beta-globulin, the major allergen of sesame seed. METHODS: A peptide containing 71 amino acids (peptide B) was previously identified by us as the IgE-binding region on beta-globulin. To determine the amino acid sequence of the IgE-binding sites on peptide B, we synthesized overlapping peptides 20 and 10 amino acid residues long that span the entire length of peptide B, which were offset from each other by 10 and 2 amino acid residues, respectively. Sera from 20 subjects given diagnoses of allergy to sesame beta-globulin served to identify the epitopes by using the dot-blot test. RESULTS: At least 9 different IgE-recognition sites were identified on peptide B. Three of them, numbers 2, 3, and 13 (corresponding to amino acids 46-55, 48-57, and 76-86, respectively, in the beta-globulin sequence), appeared to be immunodominant IgE-binding epitopes. Also, these peptides were best recognized in terms of intensity of response. There was no obvious sequence motif shared by the 9 different IgE-binding epitopes of beta-globulin. However, approximately 60% of the amino acids represented in the epitopes are hydrophobic residues. CONCLUSION: Identification of the IgE-binding epitopes might provide a better understanding of the functional role the allergens play in the disease and might have implications for immunodiagnosis and probably immunotherapy.  相似文献   
39.
Cell division in Escherichia coli requires the recruitment of at least 10 essential proteins to the bacterial midcell. Recruitment of these proteins follows a largely linear dependency pathway in which depletion of one cell division protein leads to the absence from the division site of "downstream" proteins in the pathway. Analysis of events that underlie this pathway is complicated by the fact that a protein's ability to recruit "downstream" proteins is dependent on its own recruitment by "upstream" proteins. Hence, one cannot separate the individual contributions of various upstream proteins to any specific recruitment step. Here we present a method--premature targeting--for bypassing the normal localization requirements of a cell division protein and apply it to FtsQ, a protein recruited midway through the pathway. We fused FtsQ to the FtsZ-binding protein ZapA such that FtsQ was targeted to FtsZ rings independently of proteins FtsA and FtsK, which are normally required for FtsQ localization. Analysis of the resulting ZapA-FtsQ fusion suggests that FtsQ associates with a large complex of cell division proteins and that premature targeting of FtsQ can restore localization of this complex under conditions in which neither FtsQ nor the associated proteins would normally be localized.  相似文献   
40.
Ethanol tolerance, a decrease in drug responsiveness with repeated administrations, is an important diagnostic criterion for alcoholism. Rapid tolerance develops within 8-24 hours of an initial ethanol exposure and shares many similarities with chronic tolerance. The genetic contribution to rapid tolerance to ethanol-induced ataxia was estimated using a panel of inbred strains of mice. Strains differed significantly in the degree of rapid tolerance development, which had a broad-sense heritability estimate of 0.11. Artificial selection was carried out to develop lines of mice that would show High (HRT) and Low (LRT) levels of Rapid Tolerance. Starting with HS/Npt mice, derived from a systematic cross of eight inbred strains, a significant response to selection was seen in replicate 1 by the third selection generation. No difference was found in replicate 2. Heritability estimates after the fourth generation were 0.25 for HRT-1 mice and 0.06 for LRT-1 mice. HRT-1 and LRT-1 mice also differed significantly in chronic tolerance development to four doses of ethanol. These studies provide evidence for a genetic contribution to rapid tolerance and support a genetic link between rapid and chronic tolerance to ethanol's ataxic effects.  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