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   1391273篇
  免费   91232篇
  国内免费   3426篇
耳鼻咽喉   16657篇
儿科学   46662篇
妇产科学   35784篇
基础医学   191783篇
口腔科学   33282篇
临床医学   124032篇
内科学   269494篇
皮肤病学   26586篇
神经病学   117192篇
特种医学   56514篇
外国民族医学   318篇
外科学   213921篇
综合类   28691篇
现状与发展   1篇
一般理论   553篇
预防医学   110758篇
眼科学   30346篇
药学   95921篇
  4篇
中国医学   2944篇
肿瘤学   84488篇
  2021年   11571篇
  2019年   11814篇
  2018年   37951篇
  2017年   29755篇
  2016年   34224篇
  2015年   16591篇
  2014年   22623篇
  2013年   32901篇
  2012年   51091篇
  2011年   67854篇
  2010年   46007篇
  2009年   37404篇
  2008年   63347篇
  2007年   69162篇
  2006年   46103篇
  2005年   46882篇
  2004年   46776篇
  2003年   46198篇
  2002年   42447篇
  2001年   49095篇
  2000年   50011篇
  1999年   42331篇
  1998年   13940篇
  1997年   12421篇
  1996年   12045篇
  1995年   11518篇
  1994年   10668篇
  1993年   9987篇
  1992年   33243篇
  1991年   32451篇
  1990年   31888篇
  1989年   30663篇
  1988年   27884篇
  1987年   28006篇
  1986年   26114篇
  1985年   25310篇
  1984年   19276篇
  1983年   16299篇
  1982年   10317篇
  1981年   9266篇
  1979年   17381篇
  1978年   12744篇
  1977年   10742篇
  1976年   10208篇
  1975年   10474篇
  1974年   12635篇
  1973年   12088篇
  1972年   11039篇
  1971年   10259篇
  1970年   9510篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Inorganic sling materials when used for treatment of urinary stress incontinence have a high success rate of achieving continence. They unfortunately attract the complication of vaginal tape erosion. When used for Transobturator tape procedure (TOT) we found the Obtape sling (Mentor-Porges, Le Plessis-Robinson, France) attracted a high rate of erosion, likely due to the tape properties. We describe a series of tape erosions with the Obtape sling, the presentation, conservative and surgical management with favourable rates of maintenance of continence. We suggest the use of larger pore sized tapes to decrease the occurrence of vaginal tape erosion.  相似文献   
932.
Immune modulation by heavy metals may cause serious adverse health effects in humans, although the mechanisms involved are not well understood. Both cadmium and lead are important environmental and occupational toxins. Therefore, in the current study, the costimulatory/adjuvant effects and the T-cell-activating potential of these metals (i.e., CdCl2 and PbCl2), are examined. These immune-modulating properties are critical in the development of conditions such as allergy, hypersensitivity, and autoimmunity. Using the direct popliteal lymph node assay (PLNA) and reporter antigen-popliteal lymph node assay (RA-PLNA) both metals were examined individually for immunotoxicity. Mercury (i.e., HgCl2) was included for comparative purposes as its effects in the RA-PLNA are well documented. Seven days following a single footpad injection containing metal and/or RA (trinitrophenyl-ovalbumin [TNP-OVA] or TNP-Ficoll), BALB/c mice were sacrificed and the popliteal lymph nodes (PLNs) removed. PLN cellularity, TNP-specific antibody-secreting cells (ASCs), and lymphocyte subsets were assessed. All three metals strongly stimulated T- and B-cell proliferation and ASC production following coinjection with the RA TNP-OVA. In each case, ASC production was skewed towards the IgG1 isotype. In addition, all three metals induced IgG production to TNP-Ficoll (although relatively weakly in the case of Cd). These results show that each of these metals can provide adjuvant signals to promote lymphocyte proliferation and enhance adaptive immune responses to unrelated antigens. Skewing of immune responses towards T helper type 2 responses suggests that each of these metals can enhance allergic and hypersensitivity reactions to environmental antigens. Furthermore, the induction of IgG responses to TNP-Ficoll, a T-cell-independent antigen, indicates that each of these metals can activate neoantigen-specific T cells. T-cell activation by metals can lead to metal hypersensitivity and has been implicated in the development of autoimmunity. This is the first report of immune modulation by CdCl2 and PbCl2 in the RA-PLNA.  相似文献   
933.
The most important physiological parameter influencing tissue response to heat is blood flow. At mild hyperthermia temperatures blood perfusion increases in many tumours and this effect is heating time-, temperature- and tumour-dependent. These flow increases can improve tumour oxygenation. When heating is terminated, perfusion and oxygenation commonly recover, although how quickly this occurs appears to be tumour-specific. While these effects are unlikely to have any anti-tumour activity they can be exploited to improve the combination of heat with other therapies. However, since similar physiological effects should occur in normal tissues, such combination therapies must be carefully applied. Heating tumours to higher temperatures typically causes a transient increase in perfusion during heating, followed by vascular collapse which if sufficient will increase tumour necrosis. The speed and degree of vascular collapse is dependent on heating time, temperature and tumour model used. Such vascular collapse generally occurs at temperatures that cause a substantial blood flow increase in certain normal tissues, thus preferential anti-tumour effects can be achieved. The tumour vascular supply can also be exploited to improve the response to heat. Decreasing blood flow, using transient physiological modifiers or longer acting vascular disrupting agents prior to the initiation of heating, can both increase the accumulation of physical heat in the tumour, as well as increase heat sensitivity by changing the tumour micro-environmental parameters, primarily an increase in tumour acidity. Such changes are generally not seen in normal tissues, thus resulting in a therapeutic benefit.  相似文献   
934.
BACKGROUND: Studies of the association between indoor allergen exposure and the development of allergic diseases have often measured allergen exposure at one point in time. OBJECTIVE: We investigated the variability of house dust mite (Der p 1, Der f 1) and cat (Fel d 1) allergen in Dutch homes over a period of 8 years. METHODS: Data were obtained in the Dutch PIAMA birth cohort study. Dust from the child's mattress, the parents' mattress and the living room floor was collected at four points in time, when the child was 3 months, 4, 6 and 8 years old. Dust samples were analysed for Der p 1, Der f 1 and Fel d 1 by sandwich enzyme immuno assay. RESULTS: Mite allergen concentrations for the child's mattress, the parents' mattress and the living room floor were moderately correlated between time-points. Agreement was better for cat allergen. For Der p 1 and Der f 1 on the child's mattress, the within-home variance was close to or smaller than the between-home variance in most cases. For Fel d 1, the within-home variance was almost always smaller than the between-home variance. Results were similar for allergen levels expressed per gram of dust and allergen levels expressed per square metre of the sampled surface. Variance ratios were smaller when samples were taken at shorter time intervals than at longer time intervals. CONCLUSION: Over a period of 4 years, mite and cat allergens measured in house dust are sufficiently stable to use single measurements with confidence in epidemiological studies. The within-home variance was larger when samples were taken 8 years apart so that over such long periods, repetition of sampling is recommended.  相似文献   
935.
936.
937.
938.
939.
Attenuation correction (AC) for myocardial perfusion SPECT (MPS) had not been evaluated separately in women despite specific considerations in this group because of breast photon attenuation. We aimed to evaluate the performance of AC in women by using automated quantitative analysis of MPS to avoid any bias. METHODS: Consecutive female patients--134 with a low likelihood (LLk) of coronary artery disease (CAD) and 114 with coronary angiography performed within less than 3 mo of MPS--who were referred for rest-stress electrocardiography-gated 99mTc-sestamibi MPS with AC were considered. Imaging data were evaluated for contour quality control. An additional 50 LLk studies in women were used to create equivalent normal limits for studies with AC and with no correction (NC). An experienced technologist unaware of the angiography and other results performed the contour quality control. All other processing was performed in a fully automated manner. Quantitative analysis was performed with the Cedars-Sinai myocardial perfusion analysis package. All automated segmental analyses were performed with the 17-segment, 5-point American Heart Association model. Summed stress scores (SSS) of > or =3 were considered abnormal. RESULTS: CAD (> or =70% stenosis) was present in 69 of 114 patients (60%). The normalcy rates were 93% for both NC and AC studies. The SSS for patients with CAD and without CAD for NC versus AC were 10.0 +/- 9.0 (mean +/- SD) versus 10.2 +/- 8.5 and 1.6 +/- 2.3 versus 1.8 +/- 2.5, respectively; P was not significant (NS) for all comparisons of NC versus AC. The SSS for LLk patients for NC versus AC were 0.51 +/- 1.0 versus 0.6 +/- 1.1, respectively; P was NS. The specificity for both NC and AC was 73%. The sensitivities for NC and AC were 80% and 81%, respectively, and the accuracies for NC and AC were 77% and 78%, respectively; P was NS for both comparisons. CONCLUSION: There are no significant diagnostic differences between automated quantitative MPS analyses performed in studies processed with and without AC in women.  相似文献   
940.
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