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   10737篇
  免费   1037篇
  国内免费   56篇
耳鼻咽喉   80篇
儿科学   292篇
妇产科学   238篇
基础医学   1536篇
口腔科学   172篇
临床医学   1455篇
内科学   1975篇
皮肤病学   225篇
神经病学   655篇
特种医学   753篇
外科学   1424篇
综合类   334篇
一般理论   6篇
预防医学   1017篇
眼科学   134篇
药学   661篇
  2篇
中国医学   39篇
肿瘤学   832篇
  2022年   77篇
  2021年   151篇
  2020年   103篇
  2019年   153篇
  2018年   160篇
  2017年   137篇
  2016年   131篇
  2015年   161篇
  2014年   236篇
  2013年   364篇
  2012年   488篇
  2011年   521篇
  2010年   331篇
  2009年   346篇
  2008年   473篇
  2007年   489篇
  2006年   482篇
  2005年   456篇
  2004年   440篇
  2003年   414篇
  2002年   359篇
  2001年   297篇
  2000年   316篇
  1999年   289篇
  1998年   177篇
  1997年   178篇
  1996年   162篇
  1995年   150篇
  1994年   123篇
  1993年   122篇
  1992年   225篇
  1991年   241篇
  1990年   191篇
  1989年   195篇
  1988年   210篇
  1987年   177篇
  1986年   185篇
  1985年   173篇
  1984年   128篇
  1983年   114篇
  1982年   82篇
  1981年   83篇
  1979年   85篇
  1978年   100篇
  1977年   93篇
  1976年   92篇
  1975年   76篇
  1974年   93篇
  1973年   83篇
  1972年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We have used serological proteome analysis in conjunction with tandem mass spectrometry to identify and sequence a novel protein, Mtb81, which may be useful for the diagnosis of tuberculosis (TB), especially for patients coinfected with human immunodeficiency virus (HIV). Recombinant Mtb81 was tested by an enzyme-linked immunosorbent assay to detect antibodies in 25 of 27 TB patients (92%) seropositive for HIV as well as in 38 of 67 individuals (57%) who were TB positive alone. No reactivity was observed in 11 of 11 individuals (100%) who were HIV seropositive alone. In addition, neither sera from purified protein derivative (PPD)-negative (0 of 29) nor sera from healthy (0 of 45) blood donors tested positive with Mtb81. Only 2 of 57 of PPD-positive individuals tested positive with Mtb81. Sera from individuals with smear-positive TB and seropositive for HIV but who had tested negative for TB in the 38-kDa antigen immunodiagnostic assay were also tested for reactivity against Mtb81, as were sera from individuals with lung cancer and pneumonia. Mtb81 reacted with 26 of 37 HIV(+) TB(+) sera (70%) in this group, compared to 2 of 37 (5%) that reacted with the 38-kDa antigen. Together, these results demonstrate that Mtb81 may be a promising complementary antigen for the serodiagnosis of TB.  相似文献   
102.
Previous studies from our laboratory, using p53 transgenic mice, have suggested that ultraviolet (UV) light-induced keratinocyte apoptosis in the skin is not affected by overexpression of mutant p53 protein. To further elucidate a possible role for p53 in UV-induced keratinocyte cell death, we now examine apoptosis in skin and isolated keratinocytes from p53 null (−/−) mice and assess the influence of cell differentiation on this process. In vivo, using this knockout model, epidermal keratinocytes in p53−/− mice exhibited only a 5.2-fold increase in apoptosis after 2000 J/m2 UVB irradiation compared with a 26.3-fold increase in normal control animals. If this p53-dependent apoptosis is important in elimination of precancerous, UV-damaged keratinocytes, then it should be active in the undifferentiated cells of the epidermal basal layer. To test this hypothesis, we examined the effect of differentiation on UV-induced apoptosis in primary cultures of murine and human keratinocytes. Apoptosis was p53-independent in undifferentiated murine keratinocytes, which exhibited relative resistance to UVB-induced killing with only a 1.5-fold increase in apoptosis in p53+/+ cells and a 1.4-fold increase in p53−/− cells. Differentiated keratinocytes, in contrast, showed a 9.4-fold UVB induction of apoptosis in p53+/+ cells, almost three times the induction observed in p53−/− cells. This UV-induced difference in apoptosis was observed when keratinocytes were cultured on type IV collagen substrate, but not on plastic alone. Western blotting of UV-irradiated, differentiated keratinocytes did not support a role for either Bax or Bcl-2 in this process. In support of these findings in mice, cell death in human cultured keratinocytes also occurred in a differentiation-associated fashion. We conclude that p53-induced apoptosis eliminates damaged keratinocytes in the differentiated cell compartment, but this mechanism is not active in the basal, undifferentiated cells and is therefore of questionable significance in protection against skin cancer induction.  相似文献   
103.

Background

Disease activity may correlate with environmental aeroallergen exposure in eosinophilic esophagitis. The association between seasons and flares of eosinophilic esophagitis (EoE) histologic activity has not been extensively studied.

Objective

We aimed to assess the frequency of seasonal exacerbations of eosinophilic esophagitis, as well as changes in symptom reporting, endoscopic findings, and histologic findings attributed to aeroallergens in an EoE cohort.

Methods

In this retrospective cohort study, we analyzed EoE patients in histologic remission (<15 eosinophil/high-power field) but who doubled the esophageal eosinophil count between seasons without change in eosinophilic esophagitis–specific therapy. Outcomes were: symptomatic global worsening (yes/no); change in endoscopic severity (EREFS scoring system); and histologic change (peak eosinophil count).

Results

Of 782 patients, 13 (4%) met inclusion criteria (mean age: 36.2; 85% male; 86% white; 85% atopic disease diagnosis), and 14 exacerbations were recorded. Of these, 71% occurred in fall and summer months. Peak eosinophil counts increased from 6.8 to 86.8 eosinophil per high-power field (P < .001). Four patients (31%) reported worsening of seasonal allergies and 5 (38%) a global worsening of symptoms. Endoscopic severity was also significantly worse during seasonal exacerbations (total EREFS 3.7 vs 1.7; P = .01). Baseline features differed by atopic diagnoses and endoscopic findings between patients with and without seasonal exacerbations.

Conclusion

Seasonal exacerbations of eosinophilic esophagitis were uncommon in this cohort and most commonly recorded over the summer and fall months. These data support a role of aeroallergens in the pathogenesis of eosinophilic esophagitis in some patients, and clinicians should consider aeroallergens as a potential cause of disease exacerbation.  相似文献   
104.
We have studied the development of anti-idiotypic antibodies to HLA and of autoantibodies reacting with alloactivated T lymphoblasts in a woman with herpes gestationis (HG). This primigravida developed an elevated titer of anti-HLA antibodies, (Ab1), in association with a low titer and late appearance of anti-anti-HLA antibodies (Ab2). At delivery she developed only minimal levels of antibodies reacting with autologous T lymphoblasts (T1), sensitized against the immunizing HLA antigens of the child. Her serum reacted, however, with T lymphoblasts, primed in AMLC against autologous T blasts alloactivated in vitro against her husband (T2). Because healthy gravidae do not show such antibodies, it appears that they are peculiar to and may represent a perturbation of the idiotypic network in regard to the immune  相似文献   
105.
Each of 5 patients with acute nitrofurantoin pleuropulmonary reactions had profound lymphopenia and 4 had eosinophilia developing early in the clinical course after the drug was withdrawn. The 2 patients tested had only one third of the normal numbers of E rosettes (T lymphocytes) in the peripheral blood during recovery. Lymphoblastic transformation tests with purified nitrofurantoin were done in 3 patients and all of them were negative; responses to phytohemagglutinin, concanavalin A, and pokeweed were decreased but still normal. The diagnosis of various nitrofurantoin hypersensitivity reactions relies on clinical data. The mechanisms of these reactions presently remain unclear.  相似文献   
106.
BACKGROUND: Health promotion activity in general practice has increased greatly since 1990. A large proportion of this work is undertaken by practice nurses. Little is known about patients' views about the providers of health promotion or their views about general practice health promotion clinics. AIM: A study was carried out in 1992 to determine patients' views about the provision of health promotion advice by general practitioners and practice nurses and their views about attending health promotion clinics. METHOD: A postal questionnaire was sent to a random sample of 1750 patients aged 16 years and over from five general practices in south Tyneside. The questionnaire explored patients' preferences regarding health promotion advice from the general practitioner or practice nurse in relation to four areas of lifestyle advice and factors that might encourage patients to attend a health promotion clinic. RESULTS: A response rate of 75% was obtained from 1639 eligible patients. Receiving health promotion advice from either the general practitioner or the practice nurse was the most commonly preferred option expressed by patients overall. The ability of health promotion clinic staff to deal with patients' concerns about their illness and short waiting times were more likely to influence patients' attendance at health promotion clinics than the presence of a general practitioner or practice nurse. CONCLUSION: In the present study, many patients found health advice received from practice nurses and general practitioners equally acceptable. However, it was the ability of health professionals to respond to patients' health concerns in the health promotion clinic rather than the type of health professional running the clinic that was important for patients.  相似文献   
107.
The expression of the apoptosis-regulating genes Bcl-2, Bcl-x, Bax, Mcl-1, and p53 analyzed in 4 cases of human immunodeficiency virus (HIV)-associated Hodgkin's disease, in 36 cases of HIV-related non-Hodgkin's lymphomas (NHLs), and in 109 cases of non-HIV-related NHLs by using immunohistochemistry. HIV-associated Hodgkin's disease samples were positive for all markers. For the HIV-related NHL samples, 36, 66, 88, 100, and 94% of the cases were Bcl-2, Bcl-x, Bax, Mcl-1, and p53 were found to be expressed in 69, 65, 82, 83, and 42%, respectively. No significant differences were observed in Bax and Mcl-1 staining between HIV-unrelated NHLs of B cell and T cell types. In contrast, Bcl-2 was positive in 66/79 (83%) and 10/30 (33%) of B cell and T cell HIV-unrelated NHLs, respectively (P2 < 0.001). Peculiar patterns were observed for hairy cell leukemia (Bax+, Bcl-2+, Mcl-1-) and for anaplastic large cell lymphoma (Bax+, Mcl-1+, Bcl-2-) in HIV-unrelated NHLs. Of interest, all cases with a positive expression of Bax were also found to express either Mcl-1 and/or Bcl-2, suggesting that Mcl-1 and Bcl-2 may counteract the pro-apoptosis function of Bax in vivo by protein-protein interaction within the tumor cell, as demonstrated previously in vitro. These results suggest that apoptosis regulation may have a role in the pathogenesis of some HIV-related and HIV-unrelated NHLs.  相似文献   
108.
Webs of Araneus diadematus Cl. were obtained under drugged (dextroamphetamine) and control conditions at three age-periods in the development of the spider from juvenility to sexual maturity. Although certain features of construction are affected in all periods and some exhibit differential effects with age, it was not possible to separate the latter from changes in body mass between periods.  相似文献   
109.
110.
The causes of stroke following coronary-artery bypass surgery are largely unknown. To determine whether carotid bruits increase the risk of these events, we compared 54 patients with postoperative stroke or transient ischemic attacks with 54 randomly selected control patients. Both groups were drawn from 5915 consecutive patients who had coronary bypass surgery at our hospital from 1970 to 1984. Carotid bruits were noted preoperatively in 13 patients with postoperative stroke and in 4 control patients. Case-control analysis showed that the presence of carotid bruits increased the risk of stroke or transient ischemic attacks by 3.9-fold (95 percent confidence interval, 1.2 to 12.8; P less than 0.05). This increased risk remained essentially unchanged after adjustment for potentially confounding variables in a multiple logistic regression analysis. Other factors associated with a significantly increased risk (P less than 0.05) of these neurologic deficits were a history of stroke or transient ischemic attack (odds ratio, 6.0; 95 percent confidence interval, 1.6 to 22.1), a history of congestive heart failure (odds ratio, 5.3; confidence interval, 1.6 to 17.0), mitral regurgitation (odds ratio, 4.3; confidence interval, 1.4 to 12.9), postoperative atrial fibrillation (odds ratio, 3.0; confidence interval, 1.4 to 6.7), a cardiopulmonary-bypass pump time of more than two hours (odds ratio, 2.7; confidence interval, 1.1 to 6.7), and a previous myocardial infarction (odds ratio, 2.3; confidence interval, 1.1 to 5.1). We conclude that the presence of carotid bruits increases the risk of stroke after coronary-artery bypass surgery. However, the absolute magnitude of this risk, 2.9 percent, is small and comparable to the reported risk of stroke from carotid endarterectomy.  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