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   18598篇
  免费   880篇
  国内免费   45篇
耳鼻咽喉   416篇
儿科学   738篇
妇产科学   339篇
基础医学   2234篇
口腔科学   476篇
临床医学   1067篇
内科学   5005篇
皮肤病学   722篇
神经病学   1207篇
特种医学   424篇
外科学   2697篇
综合类   120篇
一般理论   5篇
预防医学   1634篇
眼科学   366篇
药学   988篇
中国医学   85篇
肿瘤学   1000篇
  2023年   79篇
  2022年   55篇
  2021年   353篇
  2020年   179篇
  2019年   423篇
  2018年   707篇
  2017年   419篇
  2016年   352篇
  2015年   395篇
  2014年   446篇
  2013年   702篇
  2012年   1213篇
  2011年   1360篇
  2010年   697篇
  2009年   515篇
  2008年   1118篇
  2007年   1207篇
  2006年   1146篇
  2005年   1183篇
  2004年   1090篇
  2003年   917篇
  2002年   974篇
  2001年   702篇
  2000年   866篇
  1999年   555篇
  1998年   72篇
  1997年   47篇
  1996年   63篇
  1995年   38篇
  1994年   47篇
  1993年   32篇
  1992年   197篇
  1991年   195篇
  1990年   158篇
  1989年   127篇
  1988年   104篇
  1987年   117篇
  1986年   98篇
  1985年   96篇
  1984年   44篇
  1983年   49篇
  1982年   23篇
  1979年   38篇
  1978年   25篇
  1976年   21篇
  1974年   30篇
  1972年   28篇
  1971年   25篇
  1970年   28篇
  1968年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
We analyzed the characteristics of the inflammatory response occurring in blood during pulmonary infections in human immunodeficiency virus (HIV)-infected patients. A prospective study of consecutive hospital admissions of HIV-infected patients with new-onset radiologic pulmonary infiltrates was carried out in a tertiary university hospital from April 1998 to May 2001. Plasma cyclic AMP receptor protein (CRP), interleukin 1β (IL-1β), IL-6, IL-8, IL-10, and tumor necrosis factor alpha (TNF-α) levels were determined at the time of admission and 4, 5, and 6 days later. Patients were included in a protocol addressed to study etiology and outcome of disease. A total of 249 episodes of infection were included, with the main diagnoses being bacterial pneumonia (BP) (118 episodes), Pneumocystis carinii pneumonia (PCP) (41 episodes), and mycobacteriosis (36 episodes). For these three patient groups, at the time of admission the median CRP and cytokine levels were as follows: CRP, 10.2, 3.8 and 5 mg/dl, respectively (P = 0.0001); IL-8, 19, 3, and 2.9 pg/ml (P = 0.045); and TNF-α, 46.4, 44, and 75 pg/ml, respectively (P = 0.029). There were no significant differences in levels of IL-1β, IL-6, or IL-10 among the patient groups. A total of 23 patients died. At the time of admission, HIV-infected patients with BP had higher plasma CRP and IL-8 levels than did PCP and mycobacteriosis patients. TNF-α levels were higher in patients with mycobacteriosis. An elevated IL-8 level (>61 pg/ml) at the time of admission was an independent factor associated with higher mortality (odds ratio, 12; 95% confidence interval, 1.2 to 235.5).  相似文献   
94.
OBJECTIVE: An alternative to the categorical classification of psychiatric diseases is the dimensional study of the signs and symptoms of psychiatric syndromes. To date, there have been few reports about the dimensions of mania, and the existence of a depressive dimension in mania remains controversial. The aim of this study was to investigate the dimensions of manic disorder by using classical scales to study the signs and symptoms of affective disorders. METHODS: One-hundred and three consecutively admitted inpatients who met DSM IV criteria for bipolar disorder, manic or mixed were rated with the Young Mania Rating Scale (YMRS) and the Hamilton Depression Rating Scale (HDRS-21). A principal components factor analysis of the HDRS-21 and the YMRS was carried out. RESULTS: Factor analysis showed five independent and clinically interpretable factors corresponding to depression, dysphoria, hedonism, psychosis and activation. The distribution of factor scores on the depressive factor was bimodal, whereas it was unimodal on the dysphoric, hedonism and activation factors. Finally, the psychosis factor was not normally distributed. LIMITATIONS: Patients of the sample were all medicated inpatients. CONCLUSIONS: Mania seems to be composed of three core dimensions, i.e. hedonism, dysphoria and activation, and is frequently accompanied by a psychotic and a depressive factor. The existence of a depressive factor suggests that it is essential to evaluate depression during mania, and the distribution of the depressive factor supports the existence of two different states in mania.  相似文献   
95.
The performance of two DNA line probe assays, a new version of INNO-LiPA Mycobacteria (Innogenetics, Ghent, Belgium) and the GenoType Mycobacterium (Hain Diagnostika, Nehren, Germany), were evaluated for identification of mycobacterial species isolated from liquid cultures. Both tests are based on a PCR technique and designed for simultaneous identification of different mycobacterial species by reverse hybridization and line probe technology. The INNO-LiPA Mycobacteria v2 targeting the 16S-23S rRNA gene spacer region was developed for the simultaneous identification of 16 different mycobacterial species. The GenoType Mycobacterium, which targets the 23S rRNA gene, allows simultaneous identification of 13 mycobacterial species. Both tests were evaluated on 110 mycobacterial strains belonging to 22 different mycobacterial species (20 reference strains, 83 clinical strains, and 4 Mycobacterium kansasii strains isolated from tap water) that were previously inoculated into MB/BacT bottles. The sensitivity of both methods, defined as the number of positive results obtained with the Mycobacterium genus probe together with an interpretable result on the number of samples tested was 110 of 110 (100%) for INNO-LiPA and 102 of 110 (92.7%) for GenoType. For samples with interpretable results, INNO-LiPA was able to correctly identify 109 of 110 samples (99.1%), whereas the GenoType correctly identified 100 of 102 samples (98.0%). Both tests were easy to perform, rapid, and reliable when applied to mycobacterial identification directly from MB/BacT bottles.  相似文献   
96.
BACKGROUND: Human follicular fluid contains several substances, such as cytokines and growth factors, which may affect follicular growth and maturation. The present study examines the relative contribution of macrophages and granulosa cells in the production of vascular endothelial growth factor (VEGF) and adrenomedullin in the human ovulatory follicle. METHODS: Both follicular fluid samples and blood samples were obtained at the time of oocyte retrieval following ovarian stimulation from 20 women undergoing IVF treatment because of male infertility. Human follicular fluid macrophages and luteinized granulosa cells were obtained from pooled follicular fluid of individual patients. Accumulation of VEGF and adrenomedullin in the culture medium of the isolated macrophages and human granulosa cells was determined at variable time intervals ranging from 0 to 48 h. Plasma and follicular fluid concentrations of VEGF and adrenomedullin were also measured. RESULTS: The follicular fluid concentrations of VEGF and adrenomedullin were significantly higher than those found in plasma. After 48 h, accumulation of VEGF in the culture medium of follicular fluid macrophages was significantly higher than that released in the culture medium of luteinized granulosa cells. In contrast, the production rate of adrenomedullin by follicular fluid macrophages was similar to that found in granulosa cells. VEGF secreted by follicular fluid macrophages increased progressively within 48 h of cell culture. A similar response pattern was observed with the culture medium of luteinized granulosa cells, but with lower production rates. CONCLUSIONS: This study suggests for the first time that both luteinized granulosa cells and macrophages actively secrete VEGF and adrenomedullin into follicular fluid in the human ovary.  相似文献   
97.
An experimental method has been developed for in vivo measurement of electrical parameters. It is thus possible to evaluate not only the instantaneous corrosion rate of implants but also their susceptibility to pitting corrosion. It has also been shown that when the method is applied to stainless steel/ceramic electrodes, these remain in the passive condition. If an eventual breakdown of the passivating film occurs, it will quickly regenerate itself.  相似文献   
98.
We used the single strand conformation polymorphism (SSCP) method to investigate 13 apparently unrelated Spanish patients with familial hypercholesterolemia (FH) for mutations in the promoter region and the 18 exons and their flanking intron sequences of the low density lipoprotein (LDL) receptor gene. We found 16 aberrant SSCP patterns, and the underlying mutations were characterized by DNA sequencing. Five novel missense mutations, Q71E, C74G, C95R, C281Y and D679E, and one nonsense mutation, Q133X, were identified. We also found six missense mutations, S156L, D200Y, D200G, E256K, T413K and C646Y, and one stop codon mutation, W(-18)X, that were previously described in patients from other populations. A new frameshift mutation, 2085del19, was found in one patient. We also identified three splicing mutations; two of them are novel mutations, 1706-10G->A and 2390-1G->A, and the other one has been reported recently, 313+1G->C. Four patients were found to carry two different mutations in the same allele: Q71E and 313+1G->C; C95R and D679E; W(-18)X and E256K, and C281Y and 1706-10G->A. Our results demonstrate that there is a broad spectrum of mutations in the LDL receptor gene in the Spanish population.  相似文献   
99.
We have designed species-specific oligonucleotides which permit the differential detection of two species of cestodes, Taenia saginata and Taenia solium. The oligonucleotides contain sequences established for two previously reported, noncoding DNA fragments cloned from a genomic library of T. saginata. The first, which is T. saginata specific (fragment HDP1), is a repetitive sequence with a 53-bp monomeric unit repeated 24 times in direct tandem along the 1, 272-bp fragment. From this sequence the two oligonucleotides that were selected (oligonucleotides PTs4F1 and PTs4R1) specifically amplified genomic DNA (gDNA) from T. saginata but not T. solium or other related cestodes and had a sensitivity down to 10 pg of T. saginata gDNA. The second DNA fragment (fragment HDP2; 3,954 bp) hybridized to both T. saginata and T. solium DNAs and was not a repetitive sequence. Three oligonucleotides (oligonucleotides PTs7S35F1, PTs7S35F2, and PTs7S35R1) designed from the sequence of HDP2 allowed the differential amplification of gDNAs from T. saginata, T. solium, and Echinococcus granulosus in a multiplex PCR, which exhibits a sensitivity of 10 pg.  相似文献   
100.
The effect of two-thirds hepatectomy on biliary lipid secretion was studied in fasted rats. Bile acids, cholesterol and phospholipids were determined in the bile of rats with biliary drainage. Bile acid and phospholipid concentrations were not significantly modified during liver regeneration but there was a significant decrease in cholesterol concentrations in bile at 12 h after hepatectomy, with a gradual return to normal values. The molar percentage of cholesterol and the calculated lithogenic index of bile were also significantly decreased by 12 h. The biliary secretion of bile acids and phospholipids, expressed per gram of liver, showed a tendency to increase regeneration, but cholesterol secretion was significantly decreased from 12 to 48 h following liver resection. Some possibilities to explain the uncoupling between cholesterol secretion and bile acid secretion are discussed.  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