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   15245篇
  免费   1408篇
  国内免费   24篇
耳鼻咽喉   162篇
儿科学   556篇
妇产科学   410篇
基础医学   2209篇
口腔科学   273篇
临床医学   1897篇
内科学   2863篇
皮肤病学   194篇
神经病学   1445篇
特种医学   365篇
外科学   1953篇
综合类   199篇
一般理论   17篇
预防医学   1812篇
眼科学   245篇
药学   885篇
中国医学   9篇
肿瘤学   1183篇
  2023年   115篇
  2022年   147篇
  2021年   428篇
  2020年   268篇
  2019年   416篇
  2018年   480篇
  2017年   330篇
  2016年   352篇
  2015年   407篇
  2014年   530篇
  2013年   745篇
  2012年   1052篇
  2011年   1070篇
  2010年   560篇
  2009年   471篇
  2008年   832篇
  2007年   854篇
  2006年   775篇
  2005年   750篇
  2004年   604篇
  2003年   584篇
  2002年   524篇
  2001年   298篇
  2000年   340篇
  1999年   276篇
  1998年   160篇
  1997年   129篇
  1996年   111篇
  1995年   105篇
  1994年   101篇
  1993年   102篇
  1992年   210篇
  1991年   205篇
  1990年   163篇
  1989年   181篇
  1988年   171篇
  1987年   188篇
  1986年   148篇
  1985年   162篇
  1984年   119篇
  1983年   87篇
  1982年   67篇
  1981年   79篇
  1980年   66篇
  1979年   102篇
  1978年   93篇
  1976年   64篇
  1973年   66篇
  1972年   60篇
  1971年   62篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
A newly developed enzyme immunoassay (EIA) was used to detect the presence of pneumococcal teichoic and lipoteichoic acids in cerebrospinal fluid (CSF) from patients with Streptococcus pneumoniae meningitis who were being treated with antibiotics. All initial CSF samples, which on culture grew S. pneumoniae, were positive in the EIA. A total of 14 subsequent culture-negative samples gave clear signals in the EIA up to day 15 after the onset of antibiotic treatment. For 11 CSF specimens, culture, microscopy, and latex agglutination were negative while the EIA detected pneumococcal antigens. The EIA did not react either with CSF of patients with meningitis caused by bacteria other than S. pneumoniae or by viral pathogens. In conclusion, this EIA can be a valuable tool for the diagnosis of S. pneumoniae meningitis from CSF samples in cases in which prior antimicrobial therapy minimizes the usefulness of culture or other antigen detection tests.  相似文献   
102.
A reciprocal translocation is described, t(4;21)(q27;p11), which occurs in a balanced carrier mother and her Down's syndrome child, 47,XX,t(4q-;21p+),+21. A review is presented of Down's syndrome associated with reciprocal translations involving chromosome No. 21.  相似文献   
103.
Immunocytochemical staining for papillomavirus antigen was carried out on 1147 consecutive cervical punch biopsy specimens over 12 months. Of 876 cases with cervical intraepithelial neoplasia (CIN) 351, were antigen positive and of 49 cases with histological evidence of human papillomavirus (HPV) infection but no CIN, 14 were positive. There were 204 cases reported to be normal on routine histological examination and 12 cases reported to show features suggestive but not diagnostic of HPV infection. Of the normal group, 24 (12%) were antigen positive and of the equivocal group, two were positive. In 122 of the normal or equivocal groups cytological examination was repeated at the time of colposcopy, and dyskaryosis was reported in 36. In only four cases was disease shown by HPV antigen staining when there was no diagnostic histological or cytological abnormality. HPV antigen staining assists in the recognition of the range of histological changes associated with productive HPV infection but is an insensitive test and has only limited value in supplementing histological and cytological examinations as a diagnostic aid in routine colposcopic pathology.  相似文献   
104.
Ecological explanations have been put forward to account for the precocious or delayed development of patency in ducts leading to the vomeronasal organ (VNO) in certain mammals. Perinatal function may be related, in part, to the patency or fusion of the vomeronasal and nasopalatine (NPD) ducts. However, few studies have focused on NPD development in primates, which generally have a prolonged period of dependence during infancy. In this study we examined 24 prenatal primates and 13 neonatal primates, and a comparative sample of fetal mice and insectivores. In embryonic and early fetal Microcebus murinus, the NPD was completely fused, whereas in fetuses of later stages the duct was partially fused or completely patent. M. myoxinus of all stages demonstrated some degree of NPD fusion. In all other prenatal primates, the NPD was fused to some extent. Four prenatal insectivores (Tenrec ecaudatus) showed some degree of NPD fusion. In Mus musculus at 19 days gestation, the NPD was patent, although the anatomically separate VNO duct was fused. T. ecaudatus and most of the neonatal primates revealed complete NPD patency. An exception was Saguinus geoffroyi, which exhibited fusion of the NPD near the VNO opening. These observations may relate to differences in perinatal VNO function. The differences noted in our study suggest that M. murinus and M. myoxinus may differ in perinatal VNO functionality and perhaps in related behavior. Observations of neonatal primates suggest that NPD patency may be relatively common at birth and could serve other purposes in addition to being an access route for VNO stimuli.  相似文献   
105.
The inhalation of Francisella tularensis biovar A causes pneumonic tularemia associated with high morbidity and mortality rates in humans. Exposure to F. tularensis usually occurs by accident, but there is increasing awareness that F. tularensis may be deliberately released in an act of bioterrorism or war. The development of a vaccine against pneumonic tularemia has been limited by a lack of information regarding the mechanisms required to protect against this disease. Vaccine models for F. tularensis in inbred mice would facilitate investigations of the protective mechanisms and significantly enhance vaccine development. Intranasal vaccination with the attenuated live vaccine strain (LVS) of F. tularensis reproducibly protected BALB/c mice, but not C57BL/6 mice, against intranasal and subcutaneous challenges with a virulent clinical isolate of F. tularensis biovar A (NMFTA1). The resistance of LVS-vaccinated BALB/c mice to intranasal NMFTA1 challenge was increased 100-fold by boosting with live NMFTA1 but not with LVS. The protective response was specific for F. tularensis and required both CD4 and CD8 T cells. The vaccinated mice appeared outwardly healthy for more than 2 months after NMFTA1 challenge, even though NMFTA1 was recovered from more than half of the vaccinated mice. These results show that intranasal vaccination induces immunity that protects BALB/c mice from intranasal infection by F. tularensis biovar A.  相似文献   
106.
During a study on the epidemiology of Staphylococcus aureus colonization in newborns, mothers, and hospital staff, S. aureus was isolated from 536 of 1,945 specimens. Ninety-three isolates of S. aureus from the three groups of individuals were included in a study to evaluate the potential of DNA fingerprinting for strain differentiation. The 93 isolates were also phage typed and their plasmid profiles were analyzed. Cleavage of DNA with BamHI resulted in 13 different DNA restriction endonuclease band patterns (DNA REBPs), one of which consisted of eight isolates whose DNA was not cleaved with BamHI. The DNAs from these eight isolates were easily cleaved with HindIII. The different DNA REBPs were stable both during in vitro and in vivo growth and allowed strain differentiation within phage groups or types. We could not show any strong association between DNA REBP classes, phage types or groups, and plasmid profiles. Of the 93 isolates, 27 (29.0%) could not be phage typed and 12 (12.9%) lacked plasmids. We therefore conclude that DNA fingerprinting is a powerful tool, in addition to phage typing and plasmid profile analysis, for strain differentiation of S. aureus.  相似文献   
107.

Objective

The purpose of this study was to evaluate websites providing information on treatment for depression to the public, and to evaluate changes in the quality of website information over time.

Methods

Websites (N?=?25) addressing depression treatment were identified through the use of the Google search engine and by suggestions from healthcare professionals. Each website was evaluated based on the extent to which it addressed content areas deemed important by the public identified in previous research, overall quality as determined by the DISCERN, and reading level.

Results

Overall, the quality of depression websites varied greatly. The majority of websites did not adequately answer the public’s questions about treatment options, and presented higher quality information in the area of pharmacological treatments as compared to other treatment options. An average reading level of 10.0 was found across websites. Upon re-evaluation, only 14 of 25 websites added new content, and the majority of websites did not improve in their overall website quality (as measured by the DISCERN).

Conclusion and Practice Implications

Websites could be improved by addressing important questions that consumers have concerning depression, as well as by creating higher quality content in the areas of psychological, neurotherapeutic, and alternative treatments.  相似文献   
108.
Blood culture records from 1994 to 1995 from five U.S. medical centers all using the Difco ESP continuous monitoring blood culture system were reviewed retrospectively. Among a total of 7,362 isolates of bacteria and yeasts, only 0.1% of possibly significant isolates would have been missed had blood cultures been routinely incubated for 4 days instead of the 5 days recommended by the manufacturer. Conversely, numerous contaminants, detected only on day 5, would have been eliminated by a 4-day incubation period.  相似文献   
109.
The relationship of toxoplasma antigen(s) to the origin and long-term persistence of the mononuclear cell inflammatory infiltrate that is present in the brains of mice chronically infected with Toxoplasma gondii was studied by using the peroxidase-antiperoxidase immunohistochemical staining technique. C3H/Km mice were infected with the avirulent C37 strain of T. gondii and sequentially sacrificed over the ensuing 107 days. Comparable sections of each brain were prepared for routine light microscopy. Antisera to toxoplasma made in rabbits were used for immunohistological staining, and adjacent slides were also stained with conventional histological stains. The peroxidase-antiperoxidase stain demonstrated toxoplasma tissue cysts, tachyzoites, and intra- and extracellular antigen-antibody reaction products. Early infection was characterized by small tight clusters of free tachyzoites gaining access to brain substance in the absence of an inflammatory response. Once there was disruption of neural parenchyma, a mononuclear cellular infiltrate rapidly ensued. After the first days of infection, mononuclear cells were always present in all infected brains and were anatomically associated with some component of toxoplasma antigen(s). The histological picture of late infection suggested that recurrent episodes of hematogenous dissemination of tachyzoites occurred in infected mice and that such episodes were at least partially responsible for persistence of an antigenic stimulus.  相似文献   
110.
Using multiple PCR primer sets, we tried to optimize the detection of human papillomavirus (HPV) in DNA samples isolated from 361 frozen biopsy specimens from patients with invasive cervical carcinomas. The HPVs detected were placed into three distinct groups, including group I/Inex at Telelab (Skien, Norway) and group Ineg and group II at the Norwegian Radium Hospital (Oslo, Norway). The consensus primer sets were Oli-1b-oli-2i, My09-My11, Gp5-Gp6, and Gp(5+)-Gp6+ from the HPV L1 gene and CpI-CpIIG from the E1 gene. Using these consensus primers together with the type-specific primers from E6-E7, we found that 355 patients (98%) were HPV positive. Type-specific primers for HPV types 11, 16, 18, 31, 33, and 35 detected more HPV-infected patients than the most sensitive consensus primer set, while the three consensus primer sets My, Gp/Gp+, and Cp together detected more HPV-positive patients than the type-specific primers. Testing of sensitivity of the PCR with SiHa cells serially diluted in lymphocytes (HPV-negative cells) indicated a detection limit of 6,300 HPV type 16 DNA copies with consensus primers (My, Gp+, and Cp) and 126 original HPV type 16 DNA copies with type-specific primers. Comparison of the amplification results for consensus L1 primers and type-specific E6-E7 primers indicated the presence of L1 deletions in 23 of 56 samples. The conclusion is that in PCR detection systems, multiple consensus primers and type-specific primers should be used in order to detect all patients harboring HPV.  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