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   6022篇
  免费   397篇
  国内免费   5篇
耳鼻咽喉   97篇
儿科学   137篇
妇产科学   235篇
基础医学   951篇
口腔科学   86篇
临床医学   675篇
内科学   1203篇
皮肤病学   103篇
神经病学   668篇
特种医学   324篇
外科学   818篇
综合类   48篇
一般理论   1篇
预防医学   278篇
眼科学   124篇
药学   279篇
中国医学   12篇
肿瘤学   385篇
  2022年   46篇
  2021年   85篇
  2020年   53篇
  2019年   80篇
  2018年   84篇
  2017年   64篇
  2016年   90篇
  2015年   133篇
  2014年   174篇
  2013年   229篇
  2012年   305篇
  2011年   307篇
  2010年   223篇
  2009年   171篇
  2008年   282篇
  2007年   297篇
  2006年   310篇
  2005年   279篇
  2004年   252篇
  2003年   236篇
  2002年   215篇
  2001年   232篇
  2000年   216篇
  1999年   167篇
  1998年   76篇
  1997年   55篇
  1996年   64篇
  1995年   57篇
  1994年   39篇
  1993年   50篇
  1992年   113篇
  1991年   119篇
  1990年   106篇
  1989年   101篇
  1988年   92篇
  1987年   78篇
  1986年   62篇
  1985年   73篇
  1984年   54篇
  1983年   40篇
  1982年   31篇
  1979年   60篇
  1978年   32篇
  1977年   40篇
  1975年   32篇
  1974年   41篇
  1973年   43篇
  1972年   45篇
  1971年   36篇
  1968年   29篇
排序方式: 共有6424条查询结果,搜索用时 15 毫秒
51.
We report an unusual case of a nodular variation of pulmonary endometriosis. To our knowledge, there is no previous report on a morphological investigation of this entity. The etiology of this rare condition is still a matter of discussion. The well-circumscribed nodular mass is composed of cells identical to, or closely resembling, those of endometrial stroma containing sparse cysts and glands. Immunohistochemically, the cells showed an extensive co-expression of cytokeratin AE1/AE3 and vimentin and were highly positive for progesterone receptor (PRICA) and estrogen receptor (ERICA). Cells lining the cysts and glands as a monolayer were reactive for Ber-Ep4, cytokeratin Pan and cytokeratin AE1/AE3 and negative to all other markers used including PRICA and ERICA. The differential diagnosis of this entity included fibrous tumor of the pleura and metastatic low-grade-endometrial-stromal-sarcoma. The morphological findings are correlated with immunohistochemical studies and results of cell image analysis. This study details the clinicopathological features of the nodular variation of pulmonary endometriosis.  相似文献   
52.
An experimental verification of the recently developed XVMC code, a fast Monte Carlo algorithm to calculate dose distributions of photon beams in treatment planning, is presented. The treatment head is modelled by a point source with energy distribution (primary photons) and an additional head scatter contribution. Utility software is presented, allowing the determination of the parameters for this model using a single measured depth dose curve in water. The simple beam model is considered to be a starting point for more complex models being planned for future versions of the code. This paper is mainly focused on the influence of the different techniques on variance reduction and material property determination for dose distributions. It is demonstrated that XVMC and the simple beam model reproduce measured (by a diamond detector) relative dose distributions with an accuracy of better than +/-2% in various homogeneous and inhomogeneous phantoms. Furthermore, relative dose distributions in solid state phantoms have been measured by film. Also for these cases, measured and calculated dose distributions agree within experimental uncertainty. The short calculation time (depending on voxel resolution, statistical accuracy, field size and energy, a span of 1 min to 1 h using a present-day personal computer) and an interface to a commercial planning system will allow the implementation of the code for routine treatment planning of clinical electron and photon beams.  相似文献   
53.
Treatment of keratoconjunctivitis sicca with topical androgen   总被引:6,自引:0,他引:6  
Worda C  Nepp J  Huber JC  Sator MO 《Maturitas》2001,37(3):1938-212
Objective: Androgens have been reported to influence lipid production of sebaceous glands and even many ocular tissues. The effect of topical androgen therapy on a 54-year-old patient with keratoconjunctivitis sicca (KCS) and decreased lipid phase of the tear film is reported. Methods: For assessment of the lipid phase of the tear film, break up time (BUT) and lipid layer thickness (LLT) were monitored during 6 months before treatment as well as 3 months while using a daily topical androgen therapy. Results: During the topical androgen therapy the pathological lipid phase of the tear film was completely restored indicated by the normalisation of the values of BUT and LLT. Conclusion: These findings are consistent with animal experiments indicating that topical administered androgen can restore the decreased lipid phase of the tear film. This may open up new therapeutic strategies for KCS.  相似文献   
54.
BACKGROUND: Lack of endothelium-derived nitric oxide is associated with vasospasm and vascular infarction. We investigated the relationship between idiopathic recurrent miscarriage and a polymorphism of the gene encoding endothelial nitric oxide synthase (NOS3). METHOD: In a prospective case-control study, 105 women with idiopathic recurrent miscarriage and 91 healthy controls were investigated. We used the polymerase chain reaction to identify the different alleles of a 27 base pair tandem repeat polymorphism in intron 4 of the NOS3 gene. RESULTS: The wild type B allele was identified on 329 out of 392 chromosomes (frequency 0.84). The polymorphic A allele was present on 63 chromosomes (frequency 0.16). The genotype frequencies were as follows: 68% (B/B), 31% (A/B) and.5% (A/A). The distribution of genotype frequencies was significantly different between the study and control groups for allele A/B heterozygotes (NOS3(A/B)) (36.7 versus 23.8%, P = 0.03, OR 1.6, 95% CI 1.1--3.8). Only one individual was homozygous for the A allele (NOS3(A/A)). She was in the study group. Between women with primary and secondary recurrent miscarriages, no statistically significant difference between the distribution of NOS3(A/B) genotypes (28 versus 34%) was observed. CONCLUSIONS: These data support a role for the NOS3 gene as a genetic determinant of the risk of idiopathic recurrent miscarriage.  相似文献   
55.
Association between atrial fibrillation and central sleep apnea   总被引:3,自引:0,他引:3  
Leung RS  Huber MA  Rogge T  Maimon N  Chiu KL  Bradley TD 《Sleep》2005,28(12):1543-1546
BACKGROUND: We previously described an association between atrial fibrillation and central sleep apnea in a group of patients with congestive heart failure. We hypothesized that the prevalence of atrial fibrillation might also be increased in patients with central sleep apnea in the absence of other cardiac disease. METHODS AND RESULTS: We compared the prevalence of atrial fibrillation in a series of 60 consecutive patients with idiopathic central sleep apnea (apnea-hypopnea index > 10 events per hour, > 50% central events) with that in 60 patients with obstructive sleep apnea (apnea-hypopnea index > 10, > 50% obstructive events) and 60 patients without sleep apnea (apnea-hypopnea index < 10), matched for age, sex, and body mass index. Subjects with a history of congestive heart failure, coronary artery disease, or stroke were excluded from the study. The prevalence of atrial fibrillation among patients with idiopathic central sleep apnea was found to be significantly higher than the prevalence among patients with obstructive sleep apnea or no sleep apnea (27%, 1.7%, and 3.3%, respectively, P < .001). However, hypertension was most common and oxygen desaturation most extreme among patients with obstructive sleep apnea. CONCLUSIONS: We conclude that there is a markedly increased prevalence of atrial fibrillation among patients with idiopathic central sleep apnea in the absence of congestive heart failure. Moreover, the high prevalence of atrial fibrillation among patients with idiopathic central sleep apnea is not explainable by the presence of hypertension or nocturnal oxygen desaturation, since both of these were more strongly associated with obstructive sleep apnea.  相似文献   
56.
57.
Complement-dependent lymphocytotoxic autoantibodies (CLA) are invariably present in sera of patients with active systemic lupus erythematosus (SLE). This study aimed to test for the influence of such antibodies on the in vitro generation of human alloantigen reactive proliferative and cytotoxic T cell responses. Unsensitized or alloantigen primed memory cells were pre-treated with CLA in the presence or absence of complement. Following stimulation of the remaining cells with allogeneic peripheral blood mononuclears, the proliferative and cytotoxic capacity was evaluated. Results indicated that only pre-treatment with CLA and complement influenced these reactions whereas in the absence of complement antibodies were totally ineffective. Pre-treatment of unsensitized precursor cells reduced and delayed both proliferative and cytotoxic reactivity; in contrast, pre-treatment of memory cells exclusively reduced cellular cytotoxicity. It thus appears that such SLE associated autoantibodies in the presence of complement are capable of modifying the balance between different subsets of alloreactive T cells.  相似文献   
58.
Pulmonary alveolar macrophages were obtained by bronchopulmonary lavage from male rats after 30 consecutive days of in vivo exposure to marijuana and tobacco smoke. No significant differences were found between either group of experimental animals and controls in the number of cells recovered, the protein content per 10(6) cells, or the percentage of cells that adhered to plastic surfaces. The ability of macrophages to phagocytize viable bacteria was not affected by exposure to either marijuana or tobacco smoke in that both treatment groups ingested Staphylococcus aureus over a 60-min period as well as did control cells. Differences were found between the groups, however, with respect to cellular metabolism. Marijuana smoke inhalation caused a small decrease in the amount of oxygen consumed by macrophages during phagocytosis, as compared with control cells. This may have been reflected in the even greater decrease in superoxide formation observed during particle engulfment by these treated cells. Tobacco smoke, on the other hand, increased oxygen consumption and was without effect on superoxide release. Neither tobacco nor marijuana smoke treatment had an effect on the direct oxidation of glucose via the hexose monophosphate shunt. Our results indicate that, despite several metabolic alterations in response to marijuana and tobacco smoke, alveolar macrophages were not compromised with respect to their ability to ingest a particulate challenge.  相似文献   
59.
60.
Dyschondrosteosis (DCS) is an autosomal dominant form of mesomelic dysplasia that has been recently ascribed to large-scale deletions and nonsense mutations of the SHOX gene on the pseudoautosomal region of chromosome X and Y [Belin et al., 1998: Nat Genet 19:67-69; Shears et al., 1998: Nat Genet 19:70-73]. Here, we report the molecular analysis of a total of 23 DCS families including 16 previously reported pedigrees [Belin et al., 1998: Nat Genet 19:67-69; Huber et al., 2001: J Med Genet 38:281-284] and 7 novel DCS families. Linkage analyses in 21 of 23 families were consistent with linkage to the pseudoautosomal region. However, in 2 of 23 families, linkage studies excluded SHOX as the disease-causing gene, suggesting that this condition is genetically heterogeneous.  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