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   1658篇
  免费   154篇
  国内免费   7篇
耳鼻咽喉   6篇
儿科学   36篇
妇产科学   16篇
基础医学   264篇
口腔科学   23篇
临床医学   197篇
内科学   283篇
皮肤病学   14篇
神经病学   223篇
特种医学   95篇
外科学   192篇
综合类   28篇
一般理论   5篇
预防医学   158篇
眼科学   11篇
药学   184篇
中国医学   1篇
肿瘤学   83篇
  2021年   17篇
  2019年   19篇
  2018年   20篇
  2017年   12篇
  2016年   24篇
  2015年   35篇
  2014年   38篇
  2013年   44篇
  2012年   63篇
  2011年   56篇
  2010年   39篇
  2009年   41篇
  2008年   71篇
  2007年   83篇
  2006年   85篇
  2005年   82篇
  2004年   75篇
  2003年   79篇
  2002年   53篇
  2001年   33篇
  2000年   32篇
  1999年   29篇
  1998年   30篇
  1997年   26篇
  1996年   33篇
  1995年   18篇
  1994年   20篇
  1993年   20篇
  1992年   29篇
  1991年   30篇
  1990年   25篇
  1989年   27篇
  1988年   30篇
  1987年   18篇
  1986年   17篇
  1985年   22篇
  1984年   19篇
  1983年   22篇
  1980年   20篇
  1979年   21篇
  1978年   9篇
  1977年   16篇
  1976年   14篇
  1975年   12篇
  1973年   11篇
  1972年   9篇
  1971年   9篇
  1968年   9篇
  1925年   9篇
  1924年   20篇
排序方式: 共有1819条查询结果,搜索用时 296 毫秒
101.
Of 2,545 in-patients with primary lung cancer, pathological proof of the diagnosis was obtained by sputum cytology in 48%, by bronchoscopy in 32%, by biopsy from miscellaneous sites in 12%, and at thoracotomy or necropsy only in 19%. The diagnosis was made solely on clinical and radiological evidence in 8%.  相似文献   
102.
Assessing release courses in vocational training   总被引:1,自引:1,他引:0       下载免费PDF全文
A series of visits to selected vocational training schemes revealed a wide variation in attendance by trainees, content of release courses, use of teaching methods, and participation in planning by trainees. The principal criticism made by ex-trainees was the absence of enough teaching on practice management.

I suggest that it is important to clarify as soon as possible the division of teaching responsibilities between training practices and release courses.

  相似文献   
103.
104.
Histology and ultrastructure of an oncocytic adenoma of the human pituitary   总被引:3,自引:0,他引:3  
A M Landolt  U W Oswald 《Cancer》1973,31(5):1099-1105
  相似文献   
105.
In the search of genes potentially implicated in the aetiology of affective disorders (AD), SUBSTANCE P (SP) pathway is receiving increased interest. SP receptor antagonists, such as MK-869 and L-759274, have been shown to have antidepressant effect. Results from preclinical and human studies implicate SP and its pathway in the pathophysiology of mood disorders. We investigated a possible association between 20 single nucleotide polymorphisms (SNPS) among four SP-related genes and unipolar and bipolar ad (UPAD and BPAD) in a first sample of 92 UPAD patients and 92 control individuals and in a replication sample of 92 UPAD patients and 92 control individuals. An additional sample of 113 BPAD patients has also been ascertained. Our results showed a significant association between the angiotensin-converting enzyme gene (ACE1) and UPAD in our first sample, but not in the replication sample. No significant evidence of association was found in other SP-related genes. We did not find any association in the BPAD sample. When pooling first and replication UPAD samples, an association was found between ACE1 and a subgroup of patients remaining depressed after an adequate antidepressant treatment. In conclusion, our findings do not support a major contribution of SP-related genes in UPAD and BPAD, but provides some evidence of an ace influence in treatment response to antidepressants.  相似文献   
106.
BACKGROUND: Currently, no evidence is available on the putative associations between a novel single nucleotide polymorphism of the 5,10-methylenetetrahydrofolate reductase gene MTHFR 1793G>A and plasma levels of vitamin B(12), folate, or total homocysteine (tHcy). METHODS: In a cross-sectional study of 730 kidney allograft recipients, patients were categorized by MTHFR 1793G>A genotype. In univariate and multivariate linear regression models that allowed the outcome variables vitamin B(12), folate, and tHcy plasma levels to follow a gamma distribution, we tested for possible associations of allelic variants of MTHFR 1793G>A and these three dependent variables. As hypothesized in previous work, we specifically evaluated possible effect modification between the MTHFR 1793G>A and 1298A>C mutations on these outcomes. RESULTS: The allele frequency for MTHFR 1793G>A was 0.052. Heterozygosity (N= 72) or homozygosity (N= 2) for MTHFR 1793G>A was not independently associated with plasma levels of vitamin B(12) (P= 0.33) or tHcy (P= 0.70), but a borderline association with higher folate concentrations was detected (Deltafolate = 1.91 nmol/L) (95% CI -0.03 to 3.86 nmol/L) (P= 0.05). Further, we found strong and significant positive interactions between the MTHFR 1793G>A and 1298A>C mutations on vitamin B(12) concentrations. CONCLUSION: Higher folate concentrations in kidney transplant recipients with MTHFR 1793GA or 1793AA and markedly higher concentrations of vitamin B(12) in patients with combined MTHFR 1793G>A and 1298A>C mutations may contribute to the survival advantage that has been postulated for such patients showing these genotypes.  相似文献   
107.
PURPOSE: Endogenous and exogenous insulin is suggested to stimulate hypertrophic wound-healing responses and therefore may promote neointimal hyperplasia and restenosis after balloon angioplasty. The ratio of C-peptide to insulin reflects endogenous insulin secretion. In diabetic patients with insulin substitution, lower ratios display a higher proportion of exogenous insulin. The association and interaction of insulin and C-peptide with restenosis after percutaneous transluminal angioplasty (PTA) was investigated in type II diabetic and nondiabetic patients. MATERIALS AND METHODS: The study group included 76 patients (median age, 68 years; interquartile range [IQR], 58-74 years; 55 men [72%]; 31 patients [41%] with type II diabetes) with intermittent claudication (n = 49; 64%) or critical limb ischemia (n = 27; 36%) who underwent primary successful femoral PTA. C-peptide and insulin levels were measured at baseline, and patients were followed to determine restenosis (> or =50%) at 12 months by color-coded duplex sonography. RESULTS: Restenosis was found in 34 patients (45%) at 12 months. Patients with restenosis had higher insulin levels (median, 21.3 microU/mL IQR, 11.3-35.5 microU/mL) and a lower C-peptide/insulin ratio (median, 16; IQR, 10-21) compared with patients without restenosis (median insulin level, 11.6 microU/mL; IQR, 9.1-22.0 microU/mL [P = .008]; median ratio, 19 [IQR, 17-25], P = .039). In nondiabetic patients, insulin levels were significantly associated with restenosis (P = .046), whereas the ratio of C-peptide to insulin showed no association with restenosis. In patients with type II diabetes (n = 31; 41%), in contrast, the C-peptide/insulin ratio was associated with restenosis (P = .047), whereas insulin levels showed no significant association with restenosis (P = .14). CONCLUSIONS: Insulin levels and the C-peptide/insulin ratio were associated with restenosis after femoral PTA. Exogenous and endogenous insulin may play a role in the pathogenesis of recurrent lumen loss after balloon angioplasty.  相似文献   
108.
DNA vaccination using vectors expressing the gag/pol and env genes of feline leukaemia virus (FeLV) and plasmids encoding feline interleukin-12 (IL-12) and IL-18 completely protected cats from viraemia following challenge [Hanlon L, Argyle D, Bain D, Nicolson L, Dunham S, Golder MC, et al. Feline leukaemia virus DNA vaccine efficacy is enhanced by coadministration with interleukin-12 (IL-12) and IL-18 expression vectors. J Virol 2001;75:8424-33]. However, the relative contribution of each cytokine gene towards protection is unknown. This study aimed to resolve this issue. IL-12 and IL-18 constructs were modified to ensure effective expression, and bioactivity was demonstrated using specific assays. Kittens were immunised intramuscularly with FeLV DNA and various cytokine constructs. Together with control kittens, these were challenged oronasally with FeLV and monitored for 15 weeks. All six kittens given FeLV, IL-12 and IL-18 were protected from the establishment of persistent viraemia and four from latent infection. Of six kittens immunised with FeLV DNA and IL-18, all were protected from viraemia and five from latent infection. In contrast, three of five kittens given FeLV DNA and IL-12 became persistently viraemic. Therefore, the adjuvant effect on the FeLV DNA vaccine appears to reside in the expression of IL-18.  相似文献   
109.
Compressive neuropathies are highly prevalent, debilitating conditions with variable functional recovery after surgical decompression. Chronic nerve compression injury induces concurrent Schwann cell proliferation and apoptosis in the early stages of the disorder, independent of axonal injury. These proliferating Schwann cells locally demyelinate and remyelinate in the region of injury. Furthermore, Schwann cells upregulate vascular endothelial growth factor secondary to chronic nerve compression injury and induce neovascularization to facilitate the recruitment of macrophages. In contrast to Wallerian degeneration, macrophage recruitment occurs gradually with chronic nerve compression injury and continues for a longer time. Schwann cells change their gene and protein expression in response to mechanical stimuli as shear stress decreases the expression of myelin associated glycoprotein and myelin basic protein mRNA and protein for in vitro promyelinating Schwann cells. The local down-regulation of myelin associated glycoprotein in the region of compression injury creates an environment allowing axonal sprouting that may be reversed with intraneural injections of purified myelin associated glycoprotein. These studies suggest that while the reciprocal relationship between neurons and glial cells is maintained, chronic nerve compression injury is a Schwann cell-mediated disease.  相似文献   
110.
STUDY DESIGN: Test-retest methodological design using a sample of convenience. OBJECTIVE: To determine the criterion-related validity and the reliability of measuring first ray mobility with a ruler. BACKGROUND: Studies have questioned the accuracy of assessing first ray mobility by manual examination. Use of a ruler and adherence to strict guidelines in positioning of the patient may improve the measure. This study investigates the validity, and the intrarater and interrater reliability of measuring dorsal first ray mobility with a ruler while following recent recommendations to standardize the position of measurement. A valid and reliable mechanical device designed to measure first ray mobility was used as the validation criterion of measurement. METHODS: Three clinicians performed ruler measurement of dorsal mobility on 14 subjects. A separate examiner measured dorsal mobility with the mechanical device. Intraclass correlation coefficients (ICCs) and standard error of measurements (SEMs) were computed to quantify the intrarater reliability of both testing procedures and the interrater reliability of the ruler measurement. ICCs of agreement were also computed to determine the concurrent validity of the ruler measurement for each clinician. RESULTS: Mechanical device intrarater reliability ICC was 0.98 (SEM = 0.15 mm). Ruler intrarater ICCs were equal or less than -0.06 (SEMs = 1.1 mm); ruler interrater ICC was 0.05 (SEM = 1.2 mm). The ICCs of agreement between the mechanical device and ruler method ranged from -0.44 to 0.06. CONCLUSION: The ruler method of testing demonstrates poor reliability and validity as a clinical measure.  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