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   1497篇
  免费   112篇
  国内免费   2篇
耳鼻咽喉   23篇
儿科学   19篇
妇产科学   82篇
基础医学   172篇
口腔科学   5篇
临床医学   96篇
内科学   401篇
皮肤病学   33篇
神经病学   150篇
特种医学   26篇
外科学   155篇
综合类   59篇
预防医学   84篇
眼科学   116篇
药学   141篇
中国医学   1篇
肿瘤学   48篇
  2022年   36篇
  2021年   59篇
  2020年   13篇
  2019年   21篇
  2018年   29篇
  2017年   27篇
  2016年   37篇
  2015年   37篇
  2014年   54篇
  2013年   63篇
  2012年   101篇
  2011年   109篇
  2010年   49篇
  2009年   37篇
  2008年   96篇
  2007年   106篇
  2006年   100篇
  2005年   114篇
  2004年   109篇
  2003年   83篇
  2002年   76篇
  2001年   14篇
  2000年   10篇
  1999年   22篇
  1998年   5篇
  1997年   16篇
  1996年   5篇
  1995年   7篇
  1994年   6篇
  1993年   6篇
  1992年   9篇
  1991年   11篇
  1989年   6篇
  1988年   7篇
  1987年   8篇
  1986年   6篇
  1985年   12篇
  1984年   12篇
  1983年   6篇
  1982年   4篇
  1981年   6篇
  1979年   8篇
  1978年   5篇
  1975年   3篇
  1973年   3篇
  1972年   4篇
  1971年   9篇
  1969年   9篇
  1968年   7篇
  1967年   3篇
排序方式: 共有1611条查询结果,搜索用时 15 毫秒
1.
BACKGROUND: Incisional hernia is a common problem following Roux-en-Y gastric bypass for morbid obesity. PATIENTS AND MATERIALS: We report the preliminary results of nonrandomized prophylactic use of polypropylene mesh in a group of 60 consecutive patients. The patients with highest body mass index, and/or history of abdominal hernias and profound liver damage had abdominal wall reinforced with mesh during an operation. A year later the wound was assessed in all patients. RESULTS: In standard wound closure group (n=48) incisional hernia was found in 9 cases (20%). None of the patients with inserted mesh (n=12) developed hernia. The length of hospital stay in mesh group was similar to that in the nonmesh group and shorter than in patients with hernia occurrence. Mesh insertion was complicated with wound discharge in three patients. CONCLUSIONS: In our opinion prophylactic use of polypropylene mesh in bariatric patients is highly effective in postoperative hernia prevention.  相似文献   
2.
Loss of a thumb accounts for 60% decrease of functional value of the hand, thus any attempt of it's reconstruction is a priority in the field of hand surgery. Optimal reconstructive solution for subtotal thumb amputations has not been settled. The results of partial pollicization of ring finger in 5 adult men is presented. Four patients sustained distal subtotal thumb amputation (MCP joint level), one total amputation. In three patients the distal phalange of the ring finger was transferred with the DIP joint, FDP tendon and a fragment of extensor tendon. An effective movement of a newly created thumb's IP joint was achieved in two patients. In one patient with a total thumb amputation the transfer was followed by a pollicization of the second metacarpal with remnants of proximal phalange. The postoperative course was uneventful in all of the patients. The sensitivity tested on the pulp of the transferred finger equalized to the preoperative value, the hand strength was not diminished. The cosmetic result was excellent.  相似文献   
3.
A respiratory survey was undertaken in chrysotile asbestos miners in British Columbia consisting of a questionnaire, spirometry, chest radiography, and physical examination. The tests were performed in 1977 and again in 1983. The population groups studied included 63 "exposed" (working in the plant more than nine years), 52 "controls" (working in the plant less than five years), and 38 residents of the village at the minesite. A subset of 39 was identified with high exposure (worked in the mill more than five years). Measured levels of environmental particulates were similar over the entire period of operation of the plant (1.4 to 14.0 million particles per cubic foot and 0.7-88.0 fibres/cc in the mill; 0.2 to 2.7 mpcf and 0.6 to 9.3 f/cc in the mine). The exposed groups were more likely to report cough and breathlessness than the two other groups and were also more likely to have abnormal FVC and chest x ray films (the latter not significant, p greater than 0.05) and to be more likely to have a combination of these abnormalities. There was no trend to progression in the combination of abnormalities associated with exposure on follow up. The heavily exposed group showed a significantly worse trend in FVC. This adverse trend was confined to those with initial abnormalities. Tobacco smoking did not increase the trend to progression in this group.  相似文献   
4.
INTRODUCTION: The successful use of hepatocytes depends on a reliable demonstration of the functional and morphological integrity of isolated cells. Herein we investigated whether the isolation and cryopreservation of primary human hepatocytes can compromise cell viability and liver-specific characteristics. MATERIAL/METHODS: Hepatocytes were isolated from encapsulated human liver segments by a modified 2-step perfusion technique. Isolated cells were Percoll-purified, cryopreserved, and stored in liquid nitrogen for 1-12 months. For rapid assessment of fresh and cryopreserve/thawed hepatocyte yield and viability, the cells were stained with trypan blue or labeled with fluorochromes. For immunocytochemical analysis, the cells were labeled with monoclonal antibodies for the presence of the following antigens and chemokines: CD3, CD45Ro, CD45Ra, CD34, CD68, CD90, CD95, CD20, HLA-DR, Ki67, PCNA, Bcl-2, p53, CXCR3, CXCR4, and SDF-1. The cells were tested for several specific functions, such as ureagenesis, energy status, MTT activity, lactate dehydrogenase leakage, and total CYP450 content. RESULTS: Assessment of both freshly isolated (Percoll-purified) and cryopreserved/thawed hepatocytes revealed a low constitutive level of contamination by non-parenchymal cells compared with crude (unpurified) preparations and tissue sections. All viable hepatocytes showed intact morphology and retained CYP450 protein, energy status, and urea synthesis. CONCLUSIONS: Modifications in hepatocyte preparations, such as depletion of dead, damaged, and nonparenchymal cells, improves cell purity, which can be adapted to further evaluation of hepatocyte immunogenicity. These data illustrate the importance and feasibility of human hepatocyte banking.  相似文献   
5.
Multimers of soluble major histocompatibility complex class I and II molecules have proven to be useful reagents in quantifying and following specific T cell populations. This study describes the design, generation, and characterization of a novel, single chain I-A(b) molecule which utilizes a unique linker derived from the murine invariant chain. A fragment of the invariant chain, residues 58-85, binds to a region proximal to the class II peptide binding groove and stabilizes occupancy of the class II invariant chain-associated peptide. We have utilized this fragment, replacing CLIP with the Ealpha peptide sequence, to lock the attached peptide into the class II binding groove. The single chain I-A(b) molecule was recognized by a panel of conformation-sensitive, I-A(b)-specific, monoclonal antibodies. Membrane-bound and soluble forms of the single chain I-A(b) stimulated an antigen-specific T cell hybridoma, and tetramers made from soluble monomers stained these cells. The unique features of this molecule may be useful in the design of recombinant T cell receptor ligands containing peptides with low affinity for MHC.  相似文献   
6.
Blends containing poly(ethylene terephthalate) (PET) and a series of alkyloxy laterally substituted liquid-crystalline copolyesters (HTO5-X series 1 ) in various ratios were prepared in the melt at 260°C by mechanical mixing. The visual and light microscopical appearance of the blends in the solid state and in the melt was found to be homogeneous for those blends which contained an aliphatic-rich HT05-X copolyester. The homogeneous appearance can be explained by a colloidal dispersion of the liquid-crystalline polymer (LCP) in PET. Obvious phase separation in the melt occurs slowly after long periods of time. Phase separation is forced by annealing at about 270°C, where a change of viscosity is observed, and by shearing the sample. Characterization of theblends by DSC experiments shows that the thermal behaviour of all blends is dominated by the phase transitions of PET and that the LC-low-phase of the HTO5-X copolyesters with a high degree of alkyloxy substitution is suppressed. The WAXS diffraction patterns of all blends contained an amorphous halo. For blends with low HTO5-X concentration, inner reflexions from the nematic sanidic phase, as exhibited by the HTO5-X copolyester, could be observed. For blends with higher HTO5-X copolyester concentration, characteristic reflexions from HTO5-X copolyester crystals could be observed. The number of X-ray reflexions of the crystalline LCP in the blend is reduced compared to that of the pure LCP.  相似文献   
7.
Human papillomavirus (HPV) infection is associated with transformation and clonal expansion of infected epithelial cells, resulting in the production of a benign growth, i.e. a wart. Recently, however, HPV has emerged as the primary causative agent of cervical carcinoma, malignancy being associated with the presence of the viral genome (predominantly genotypes 16 and 18) in cancerous cells. The only HPV proteins reliably expressed in neoplastic lesions are the 'oncogenic' E6 and E7 proteins, that serve both as tumour-specific markers and potential targets for immunotherapeutic intervention. As intracellular (nuclear) proteins, the E6 and E7 gene products may be hidden from the humoral immune response. Attention has thus focused on the generation of a vaccine capable of inducing or stimulating a cellular immune response to HPV 16 and HPV 18 E6 and E7. Vaccine development has been constrained by the absence of an appropriate animal model, the oncogenic nature of E6 and E7 and technical difficulties associated with detection of cytotoxic T cell responses to these antigens. Despite these difficulties, vaccine strategies have now been devised based on immunisation with synthetic peptide, whole protein and a vaccinia virus recombinant. Phase I/II human clinical trials have been initiated, and preliminary results have demonstrated the induction of specific cellular immune responses after immunisation. The HPV-associated neoplasia in cervical cancer represents an excellent target for therapeutic intervention because the tumour-associated antigens are so clearly defined. As such, it provides an appropriate model for establishing the general principles of cancer immunotherapy in humans.  相似文献   
8.
Summary The effects of two types of acute exercise (1 h treadmill running at 20 m· min–1, or 6 × 10-s periods at 43 m · min–1, 0° inclination), as well as two training regimes (endurance and sprint) on the sensitivity of epitrochlearis muscle [fast twitch (FT) fibres] to insulin were measured in vitro in rats. The hormone concentration in the incubation medium producing the half maximal stimulation of lactate (la) production and glycogen synthesis was determined and used as an index of the muscle insulin sensitivity. A single period of moderate endurance as well as the sprint-type exercise increased the sensitivity of la production to insulin although the rate of la production enhanced markedly only after sprint exercise at 10 and 100 U· ml–1 of insulin. These effects persisted for up to 2 h after the termination of exercise. Both types of exercise significantly decreased the muscle glycogen content, causing a moderate enhancement in the insulin-stimulated rates of glycogen synthesis in vitro for up to 2 h after exercise. However, a significant increase in the sensitivity of this process to insulin was found only in the muscle removed 0.25 h after the sprint effort. Training of the sprint and endurance types increased insulin-stimulated rates of glycolysis 24 h after the last period of exercise. The sensitivity of this process to insulin was also increased at this instant. Both types of training increased the basal and maximal rates of glycogen snythesis, as well as the sensitivity of this process to insulin at the 24th following the last training session. It was concluded that in the epitrochlearis muscle, containing mainly FT fibres, both moderate and intensive exercise (acute and repeated) were effective in increasing sensitivity of glucose utilization to insulin. Thus, the response in this muscle type to increased physical activity differs from that reported previously in the soleus muscle, representing the slow-twitch, oxidative fibres in which sprint exercise did not produce any changes in the muscle insulin sensitivity.  相似文献   
9.
The double fluorescent retrograde technique was employed to examine the distribution of the inferior olive (IO) neurones projecting to the cortex of the rostral and caudal parts of the paramedian lobule (PML) in the rabbit cerebellum, known to be the face-forelimb and hindlimb receiving areas, respectively. Moreover, this technique was also used to investigate the possibility that IO projections reaching these two somatotopically non-homologous PML regions are collaterals of the same axones. No other reports have addressed this question. After non-overlapping unilateral injections of the cytoplasmic tracer fast blue (FB) and the nuclear dye diamidino yellow (DY) into the rostral and caudal PML, respectively, numerous single FB- or DY-labelled cells were found in the defined regions of the contralateral IO. These regions showed considerable overlap, apart from the dorsal accessory olive where a clear spatial separation of labelled cell groups was observed. Furthermore, double FB + DY-labelled neurones (n = 310) were seen in the medial accessory olive, the dorsal and ventral laminas of the principal olive, in the dorsomedial cell column and the beta nucleus. It suggests that IO neurones may branch to supply the two functionally different PML regions and in this way participate in the mechanisms of forelimb-hindlimb coordination.  相似文献   
10.
Precise localization of parathyroid glands using 99mTc-labeled hexakis-2-methoxyisobutylisonitrile (99mTc-MIBI) scintigraphy could be affected by various biological factors. There is increasing evidence that radiotracer retention could be controlled by members of multidrug resistance (MDR) system, especially P-glycoprotein (P-gp). Since the role of P-gp in tertiary hyperparathyroidism (T-HPTH) scintigraphic studies is poorly recognized, the aim of the study was to compare the correlation between parathyroid P-gp expression and results of their scintigraphy in T-HPTH versus primary hyperparathyroidism (P-HPTH). P-HPTH (n = 19) and T-HPTH (n = 18) patients were subjected to 99mTc-MIBI scintigraphy followed by surgical treatment. The parathyroid glands were assessed in routine hematoxylin-eosin staining and P-gp expression was analyzed using immunohistochemistry. Parathyroids collected during cadaver donor multi-organ harvesting were used as a control. It has been found that P-HPTH-derived parathyroid glands with predominating adenoma morphology expressed less P-gp, as compared to P-gp-rich T-HPTH glands, mainly displaying nodular or diffused hyperplasia phenotype. This finding reversely correlated with results of 99mTc-MIBI scintigraphy. However, we did not observe any difference in P-gp expression nor scintigraphy result between nodular or diffused hyperplasia. Altogether, these data suggest that P-gp overexpression in T-HPTH could be responsible for decreased sensitivity of 99mTc-MIBI scintigraphy in those patients. Therefore, the recently proposed reduced neck exploration or limited parathyroid resection on the basis of scintigraphy could create the risk of persisted/recurrent hyperparathyroidism. However, this problem requires further study.  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