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   3693篇
  免费   157篇
  国内免费   12篇
耳鼻咽喉   13篇
儿科学   171篇
妇产科学   48篇
基础医学   476篇
口腔科学   78篇
临床医学   265篇
内科学   671篇
皮肤病学   70篇
神经病学   271篇
特种医学   111篇
外科学   479篇
综合类   92篇
一般理论   1篇
预防医学   229篇
眼科学   203篇
药学   421篇
中国医学   24篇
肿瘤学   239篇
  2023年   30篇
  2022年   80篇
  2021年   137篇
  2020年   72篇
  2019年   74篇
  2018年   107篇
  2017年   66篇
  2016年   97篇
  2015年   110篇
  2014年   125篇
  2013年   170篇
  2012年   255篇
  2011年   263篇
  2010年   132篇
  2009年   120篇
  2008年   185篇
  2007年   204篇
  2006年   185篇
  2005年   156篇
  2004年   138篇
  2003年   132篇
  2002年   143篇
  2001年   120篇
  2000年   104篇
  1999年   74篇
  1998年   30篇
  1997年   24篇
  1996年   38篇
  1995年   15篇
  1994年   6篇
  1993年   11篇
  1992年   31篇
  1991年   32篇
  1990年   39篇
  1989年   45篇
  1988年   40篇
  1987年   36篇
  1986年   29篇
  1985年   29篇
  1984年   25篇
  1983年   22篇
  1982年   15篇
  1981年   11篇
  1980年   14篇
  1979年   24篇
  1977年   13篇
  1974年   9篇
  1973年   6篇
  1971年   7篇
  1970年   9篇
排序方式: 共有3862条查询结果,搜索用时 15 毫秒
21.
A male patient of 60 years presented with a swelling in the left groin of 10 months duration. Past records showed bilateral lumbar sympathectomy and omentopexy done 20 and 6 years back, respectively, for Buerger’s disease. Abdominal examination revealed a huge hernial swelling in the left groin extending from the symphysis pubis to anterior superior iliac spine measuring 25 × 18 cm. On exploration, the contents were intestines and omentum, which were coming out through a defect of 5 × 3 cm in the lower fibers of the conjoint muscle 4 cm cephalad to the deep ring, a finding which made the final diagnosis as an incisional hernia. We present this interesting case as a very rare complication of omentopexy, probably not reported previously, and an unusual case of an incisional hernia presenting as an inguinal hernia which is very difficult to diagnose unless encountered before. Its rarity and clinical challenge is highlighted.  相似文献   
22.
Although abnormalities in serotonergic function have been the major focus of studies on suicidal behavior, several studies indicate that abnormalities of noradrenergic function may also be involved in the pathophysiology of suicide. In this paper, we have reviewed some of the noradrenergic studies in suicide, including studies of the biosynthetic enzyme for norepinephrine, tyrosine hydroxylase (TH), the receptors for norepinephrine, alpha- and beta-adrenergic receptors, as well as the signaling cascades linked to beta-adrenergic receptors. In general, these studies indicate that the protein expression of TH, as well as alpha2- and beta2-adrenergic receptors, is increased in the postmortem brain of suicide victims. More studies are needed in order to examine extensively the role of noradrenergic function in suicidal behavior.  相似文献   
23.
Consequent to the promising results reported with 99mTc(V)-DMSA for imaging certain types of soft tissue tumors, we have developed methods to prepare this radiopharmaceutical in three ways: from freshly prepared reagents, through the use of a two component kit and use of the standard renal DMSA kit by a modified recipe. The 99mTc(V)-DMSA complex has been subjected to paper electrophoretic and chromatographic procedures and also biodistribution studies. The distinctly different behaviour of this new product compared to that of the well known renal DMSA complex has been clearly established. Scintiimaging in a preliminary clinical trial in patients with medullary carcinoma of the thyroid has been encouraging.  相似文献   
24.
25.
OBJECTIVE: Visual pathways are vulnerable to vitamin B(12) deficiency but there is paucity of studies evaluating visual evoked potential (VEP) changes following vitamin B(12) supplementation. Our aim was to evaluate the visual evoked potential changes in patients with vitamin B(12) deficiency neurological syndrome and their changes after vitamin B(12) therapy. METHODS: Seventeen patients with vitamin B(12) deficiency neurological syndromes diagnosed on the basis of megaloblastic bone marrow or low serum vitamin B(12) level or both were subjected to testing of visual acuity, field of vision, colour vision and neurological examination. Cranial magnetic resonance imaging was done in 9 patients and pattern reversal VEP was carried out on admission. P(100) latency and amplitude were measured. Visual function and VEP studies were repeated at 3 and 6 months after vitamin B(12) therapy. RESULTS: The patients' age ranged between 17 and 69 years; 7 were females and 16 were lactovegetarians. The duration of symptoms ranged between 10 days and 10 years. Visual acuity, colour vision, field of vision and fundus oculi were normal. VEP revealed prolongation of P(100) latency in 10 patients (17 eyes) which was mild in 2, moderate in 10 and marked in 5 eyes. Six months after treatment, P(100) latency improved to normal in all except 4 eyes. VEP abnormality was related to duration of illness and antiparietal cell antibodies. CONCLUSIONS: VEP is frequently prolonged in patients with vitamin B(12) deficiency neurological syndrome although asymptomatic. It usually returns to normal after treatment.  相似文献   
26.
Carrier analysis and prenatal diagnosis of haemophilia A in North India   总被引:4,自引:0,他引:4  
The feasibility of DNA diagnosis for haemophilia A in North India was evaluated using intragenic polymorphic DNA markers in factor VIII gene for linkage analysis as well as direct detection of inversion mutation in intron 22 of the gene. The informativity of RFLP (HindIII, BclI and XbaI) and STR (introns 13 and 22) markers for linkage analysis in factor VIII gene was determined in 100 normal individuals. The observed heterozygosity for RFLP markers HindIII, BclI and XbaI was 0.63, 0.60 and 0.48 while that of STR markers introns 13 and 22 were 0.60 and 0.40 respectively. Six and four alleles were identified for introns 13 and 22 and the most frequent allele was 13(CA)26 and 22(AG)n(GT)26 with an allele frequency of 0.53 and 0.62 respectively. The heterozygosities observed for RFLP markers was higher (>70%) than the STR markers (50%) in the affected families with haemophilia A. Inversion mutation was detected in 37% of severely affected patients. Based on present and previous studies from India, a strategy has been proposed to provide molecular diagnosis to a large number of undiagnosed cases of haemophilia A.  相似文献   
27.
The role of calcium ions (Ca2+) in the cytotoxic activity of the dengue type 2 virus (DV)-induced macrophage (M phi) cytotoxin (CF2) was investigated in the present study. The findings show that CF2 prepared in Ca(2+)-free medium had no cytotoxic activity on normal mouse spleen cells suspended in Ca(2+)-free medium but killed the cells suspended in the medium with Ca2+. Substitution with calcium chloride restored the cytotoxic activity of CF2 the optimal dose being 10(-4) M concentration. CF2 induced an influx of Ca2+, as assayed by uptake of radiolabelled calcium chloride (45Ca), in the susceptible target cells, viz. M phi and T lymphocytes. The cytotoxic activity of CF2 as well as the CF2-induced influx of 45Ca was inhibited by treatment of the target cell with the calcium channel blocking drugs verapamil and nifedipine. Thus, the presence of Ca2+ is obligatory for the cytotoxic activity of CF2 and cell death is associated with increased intracellular Ca2+.  相似文献   
28.
We prepared recombinant Japanese encephalitis (JE) virus populations possessing random mutations at the envelope (E) protein region by a long PCR-based method. Neutralization-resistant mutants were selected from these populations by application of JE-specific virus neutralizing monoclonal antibody (mAb) 503, which possessed a 51,200-fold neutralization titer. We classified the mutants into three groups, each bearing two amino acid alterations at the E protein region: 52, Gln-Arg, and 136, Lys-Glu; 136, Lys-Glu, and 275, Ser-Pro; and 126, Ile-Thr, and 136, Lys-Glu, respectively. Three different genetically engineered variants, each bearing a single mutation, 126, Ile-Thr; 136, Lys-Glu; and 275, Ser-Pro, respectively, showed partial but not complete recovery of reactivity to mAb 503. Our results indicate that the amino acid substitutions at amino acid positions 52, 126, 136, and 275 altered the structure of the neutralization epitope for mAb 503 on the E protein. All these mutations were clustered at the junction of domains I and II of the E protein and it is likely that the epitope for mAb 503 is composed of at least E(0)-e, D(0)-a, and k strands of the E protein. We also demonstrated the efficacy of the long PCR-based recombinant virus technique as a useful tool for the creation of a variety of mutants bearing random mutations at targeted areas of the virus genome.  相似文献   
29.
Immunoglobulin GM and KM genes have been associated with antibody responses to a variety of antigens. A promoter-region polymorphism of interleukin-6 (IL-6) gene (-174 G/C) has been shown to be associated with antibody responses to heat-shock proteins (hsp) 60 and hsp65. To examine the possible epistatic effects of these unlinked genetic systems on the autoimmune responses to hsp60 and hsp65, 176 healthy Caucasian subjects from Finland were genotyped for several allelic determinants of GM, KM, and IL-6 genes by PCR-RFLP methods. IgG antibodies to hsp60 and hsp65 were measured by an ELISA. Significant interactive effects of GM f,z and IL-6-174 genotypes were noted for both anti-hsp60 (P=0.002) and anti-hsp65 (P=0.038) antibody levels. Since these autoantibodies have been implicated in susceptibility to coronary heart disease and carotid atherosclerosis, the associations reported here might be relevant to the etiology of these diseases.  相似文献   
30.
In vitro gene expression strategy was used for the production of polyclonal antiserum to the nucleocapsid protein (NP) of Groundnut bud necrosis virus (GBNV). The GBNV NP gene from cowpea isolate was cloned into 6x His-tagged UA cloning vector and expressed in Escherichia coli [M15] cells. The fusion protein was detected in insoluble fraction and was purified by using Ni-NTA agarose resin. The purified 6x His-fusion protein (32 kDa) was used for immunisation to produce a high titre polyclonal antiserum. The antiserum to the NP of GBNV at 1:4000 dilution detected successfully natural infection of GBNV and Watermelon bud necrosis virus in a wide range of cucurbitaceous, leguminous and solanaceous hosts from different locations.  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