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   4269篇
  免费   258篇
  国内免费   136篇
耳鼻咽喉   16篇
儿科学   55篇
妇产科学   232篇
基础医学   316篇
口腔科学   48篇
临床医学   202篇
内科学   258篇
皮肤病学   85篇
神经病学   221篇
特种医学   50篇
外科学   315篇
综合类   523篇
预防医学   310篇
眼科学   30篇
药学   1390篇
  2篇
中国医学   358篇
肿瘤学   252篇
  2024年   7篇
  2023年   34篇
  2022年   69篇
  2021年   92篇
  2020年   87篇
  2019年   83篇
  2018年   115篇
  2017年   123篇
  2016年   107篇
  2015年   119篇
  2014年   274篇
  2013年   331篇
  2012年   200篇
  2011年   254篇
  2010年   194篇
  2009年   182篇
  2008年   205篇
  2007年   223篇
  2006年   187篇
  2005年   174篇
  2004年   160篇
  2003年   125篇
  2002年   131篇
  2001年   89篇
  2000年   86篇
  1999年   72篇
  1998年   57篇
  1997年   66篇
  1996年   56篇
  1995年   59篇
  1994年   60篇
  1993年   53篇
  1992年   56篇
  1991年   49篇
  1990年   39篇
  1989年   36篇
  1988年   38篇
  1987年   42篇
  1986年   33篇
  1985年   61篇
  1984年   42篇
  1983年   24篇
  1982年   39篇
  1981年   27篇
  1980年   22篇
  1979年   22篇
  1978年   20篇
  1977年   16篇
  1975年   7篇
  1974年   6篇
排序方式: 共有4663条查询结果,搜索用时 15 毫秒
31.
In order to investigate superoxide production by pulmonary macrophages in the rat, a route was created by ligating both the inferior and superior venae cavae and resecting the aorta after cannulation through the inferior vena cava into the right atrium of the heart. Lung perfusion was performed via this route with nitro blue tetrazolium. Although there was no formazan deposition throughout the lung, it became detectable in both alveolar and interstitial macrophages when phorbol myristate acetate was added to the perfusate. This deposition was markedly enhanced by previous injection of Corynebacterium parvum. The deposition disappeared after further addition of Cu(Lys)2, a scavenger of superoxide anions. This procedure may be useful for estimating in situ the ability of pulmonary macrophages to produce superoxide in the rat.  相似文献   
32.
Objective:Evolving evidence of anti-inflammatory effects is observed in patients with rheumatoid arthritis or ulcerative colitis following periodic adsorptive granulocyte and monocyte (GM) apheresis with a column containing cellulose acetate (CA) beads as apheresis carriers. This study was undertaken to obtain insights into mechanisms of anti-inflammatory actions of adsorptive GM apheresis with CA beads. Methods:In a series of in-vitro experiments, we investigated the effects of plasma proteins and the leucocytes 2 integrin (CD18) on granulocyte adsorption to CA beads. Results:Granulocyte adsorption to CA beads required plasma IgG, the complement C3 and was inhibited by an antibody to leucocytes CD18. Further, hepatocyte growth factor (HGF) and interleukin-1 receptor antagonist (IL-1ra) which have strong anti-inflammatory actions were released by granulocytes that adhered to CA beads. Conclusions:Plasma IgG, C3 derived complement activation fragments and leucocytes CD18 are involved in granulocyte adhesion to CA beads and hence the release of HGF and IL-1ra.Received 27 October 2003; returned for revision 16 December 2003; accepted by M. J. Parnham 8 January 2004  相似文献   
33.
Summary A female patient is described in whom the diagnosis of idiopathic hypereosinophilic syndrome (HES) with heart disease and peripheral neuropathy was made at the age of 32 years. Although prednisone induced a prompt and longstanding complete hematological remission, progressive and eventually intractable heart failure developed, and the patient died 6 years later. Endomyocardial biopsy at diagnosis showed infiltration with intact and disintegrated eosinophils and Charcot-Leyden crystals. Echocardiographic follow-up (including Doppler-Echocardiography) revealed mitral regurgitation with thickening and impaired motility of the posterior mitral leaflet, as well as progressive dilated cardiomyopathy. At autopsy, a diffuse interstitial fibrosis with patchy prominence in an eccentric hypertrophic and highly dilated heart was found. There were no significant endocardial thickening and no mural thrombi. In contrast to the findings of the initial endomyocardial biopsy, autopsy revealed no eosinophilic infiltrate.In this case, eosinophil-induced heart disease manifested as dilated cardiomyopathy, without endocardial fibrosis as originally described by Löffler. We speculate, that eosinophils have been deposited predominantly in the myocard at an early stage of disease, and — activated locally — secreted their granule proteins producing an initial damage to capillary endothelial cells and myocytes. After prednisone-induced clearance of eosinophils from blood and tissues, progressive, self-perpetuating interstitial fibrosis of the myocard and loss of myocytes eventually resulted in end-stage dilated cardiomyopathy.Abkürzungsverzeichnis HES idiopathic hypereosinophilic syndrome - UBBC unsaturated vitamin B12 binding capacity - ECP eosinophil cationic protein - MBC major basic protein - EDD end-diastolic diameter of the left ventricle - LA left atrium diameter - LVEDP left ventricular end-diastolic pressure - NIH National Institutes of Health  相似文献   
34.
Summary We analyzed the results of clinical studies on the therapeutic efficacy of hormone monotherapy with tamoxifen, medroxyprogesterone acetate, and aminoglutethimide in metastatic breast cancer, which were published between 1971 and 1986 and involved altogether 7000 patients. The overall response rates in patients treated with these hormonal single agents at various dose levels ranged from 31%–42%. When only estrogen receptor-positive patients were considered, the response rates lay between 41% and 54% in groups which were treated with the antiestrogenic agents tamoxifen or aminoglutethimide. The duration of remission was 12 months for tamoxifen- and aminoglutethimide-treated women, whereas medroxy-progesterone acetate effected remissions lasting from 6–16 months. The overall mean survival from start of therapy in tamoxifen- and aminoglutethimide-treated groups was 20 months, whereas information concerning this therapeutic parameter was available only in a minority of medroxyprogesterone acetate-treated groups. With respect to the response by site of metastatic lesions, all three agents caused a significantly higher degree of remissions in the soft tissue as compared to visceral disease.Abbreviations AG Aminoglutethimide - MPA Medroxyprogesterone acetate - TAM Tamoxifen  相似文献   
35.
A monoclonal antibody (RH1-38) which blocks multiple systems of cell-mediated cytotoxicity was functionally characterized. RH1-38 specifically blocks, in the absence of complement, natural killer (NK) activity (K562 targets) without any effect on NK-K562 conjugate formation. Kinetic studies suggested that the antibody blocks a step that occurs 30-120 min after effector populations are mixed with target cells. Single-cell cytotoxicity assays in agarose, combined with standard 51Cr release assays and Michaelis-Menten analysis revealed that RH1-38 markedly decreases Vmax and the number of active NK cells, again without any effect on the number of target-binding cells. The maximum recycling capacity was usually decreased, but in some experiments unchanged, in the presence of the monoclonal antibody. RH1-38 inhibited equally well whole peripheral blood mononuclear leukocytes (PBML), Percoll-fractionated lymphocytes enriched for NK activity, and interferon (IFN)-boosted NK activity. PBML exposed to RH1-38 and then washed mediated depressed NK activity which was partially reversed by subsequent treatment with IFN. These studies are most consistent with the hypothesis that RH1-38 inhibits a step late in the NK cytolytic mechanism rather than through an effect on conjugate formation. The primary effect is probably not on the IFN-generating or boosting mechanism, but a secondary effect on IFN-related mechanisms cannot be ruled out. Inhibition through an effect on a small lymphocyte modulator of NK activity is also unlikely but not rigorously excluded. Thus, RH1-38 appears to inhibit NK activity through a direct effect on NK effector cells, probably by interfering with a cell-surface molecule which is important in the expression of NK activity. The companion paper demonstrates that this monoclonal antibody immunoprecipitates a molecule which is very similar or identical to the LFA-1 antigen. Thus, RH1-38 recognizes either a novel epitope on the LFA-1 molecule or alternatively a distinct, functional killer cell surface molecule. The epitope appears to be involved in a late step in the cytolytic mechanism, possibly part of the effector cell lytic machinery.  相似文献   
36.
BACKGROUND: The introduction of GnRH antagonists such as cetrorelix acetate has made possible the simplification of ovarian stimulation. However, the most effective protocol for their administration has not yet been clearly defined. METHODS: Forty women with male-factor infertility undergoing 40 ICSI cycles were included in the study. Clomiphene citrate at 100 mg a day was given from cycle day 3 through day 7. hMG at 150 IU was given on cycle days 4, 6 and 8, and was adjusted from day 9 according to the follicular and hormone responses. Cetrorelix acetate at 2.5 mg was administered when the leading follicle reached 14 mm. The remaining 0.5 mg was divided into two 0.25 mg injections for possible later use. Serum FSH, LH, estradiol and progesterone levels were measured daily from the day of cetrorelix acetate injection until hCG was given. RESULTS: Serum LH level was suppressed effectively for 4 days. Four patients (10%) needed one or two additional injections of 0.25 mg cetrorelix acetate. No premature LH surge was detected in any of the women treated. Sixteen women became pregnant (40%), of which 14 pregnancies (35%) were ongoing at the time of writing. CONCLUSIONS: This study demonstrates that this new protocol is feasible for couples with male-factor infertility undergoing ICSI.  相似文献   
37.
In the past endocrine toxicology has not been a common subject in routine toxicity studies. However, since the endocrine system is an important integrating system of the body, controlling the major physiological functions, it is important to investigate the mechanism of action of exogenous compounds in endocrine target organs or hormonal target cells. The following procedure is suggested to detect effects on the endocrine system in routine toxicity experiments: (1) determination of the weight of endocrine organs and histology as screening parameters; (2) determination of circulating hormones in combination with morphological or immunocytochemical methods: (3) specific function tests and in vitro methods to determine dysfunction of specific endocrine organs or cells. That the use of such an approach has provided insight into the mechanism of action of chemical compounds will be demonstrated by results of endocrine toxicity studies with the antibiotic compound sulphadimidine, interfering with thyroid hormone synthesis as a secondary mechanism leading to thyroid tumour formation, the androgenic compound trenbolone acetate, used for growth promotion, for which the disturbance of the gonadal function formed the basis for the establishment of the no-observed-hormonal-effect level, the antibacterial compound furazolidone, suspected of having an oestrogenic activity which was hypothesized as the underlying mechanism for the observed mammary tumour formation, and the antimicrobial agent carbadox, used as feed additive for pigs, for which the interference with adrenal function, resulted in a severe disturbance of the water and salt balance in target animals. Originally presented at ECCP 93.  相似文献   
38.
BACKGROUND: Abnormal uterine bleeding is commonly associated with progestin-only contraceptives, including depot medroxyprogesterone acetate (DMPA), and remains the main reason why these agents are discontinued. Matrix metalloproteinases (MMP), enzymes which degrade specific extracellular matrix components, and leukocytes are implicated in menstruation. Alteration in endometrial MMP-9 and leukocytes has been described in users of other progestin-only contraceptives, suggesting a potential role in the pathogenesis of abnormal uterine bleeding. METHODS: This study describes the immunohistochemical localization of MMP-9, the tissue inhibitors of metalloproteinases (TIMP)-1, TIMP-2 and TIMP-3, and leukocytes [CD3+ T lymphocytes, CD68+ macrophages and CD56+ uterine natural killer cells (uNK cells)] in the endometrium of women using DMPA. Comparison is made with perimenstrual endometria from normal cycling women. RESULTS: Similar to the perimenstrual period, an influx of MMP-9 positive cells (identified as neutrophils and CD3+ T cells on the basis of dual immunofluorescence), macrophages and uNK cells was observed in the endometrium of DMPA users. However, significantly more endometrial T lymphocytes were observed in DMPA users. Immunoreactive TIMP, present in all endometrial compartments, demonstrated a significantly decreased immunostaining intensity score in endometrial epithelium (TIMP-1 and TIMP-2), stroma (TIMP-1, TIMP-2 and TIMP-3), endothelium (TIMP-1 and TIMP-2) and vascular smooth muscle (TIMP-1) of DMPA users compared with controls. No correlation was observed between the parameters studied and bleeding patterns reported by subjects. CONCLUSIONS: These findings provide additional evidence for the importance of the MMP/TIMP balance in the loss/maintenance of endometrial integrity and in the complex pathological mechanisms involved in the troubling side-effect of menstrual bleeding disturbance.  相似文献   
39.
本文报道在白细胞介素2(IL-2)及黄芪多糖(PA)作用下,小鼠NK细胞的细胞化学和超微结构变化。实验表明,NK细胞酸性磷酸酶、酸性醋酸酯酶及氯醋酸AS-D酯酶均为阳性。经IL-2和PA的处理,前两种酶的活性增加,阳性细胞百分率增高,并与NK活性相关。IL-2培养后的NK细胞超微结构表现为胞体变大,表面不规则,胞质丰富,细胞器增多等特点。  相似文献   
40.
Following identification of the proportion of pelvic congestion among symptomatic patients complaining of chronic pelvic pain, and in a totally asymptomatic group of patients requesting tubal ligation, the efficiency of goserelin acetate versus medroxyprogesterone acetate was compared objectively using pelvic venogram scores, and subjectively by symptom resolution, improvement of psychological status and sexual functioning in a prospective randomized trial in 47 patients with pure pelvic congestion syndrome. Patients received either goserelin acetate (3.6 mg/month for 6 months) or medroxyprogesterone acetate (MPA; 30 mg/day for 6 months). Among patients with chronic pelvic pain, those with pure pelvic congestion were mostly parous, had the most severe pelvic signs and symptom scores, lowest rates of sexual functioning, and higher states of anxiety and depression as compared with others. At 1 year after treatment, goserelin remained superior to MPA in terms of pelvic venographic improvement as an objective measure. In alleviation of signs and symptomatology, improvement of sexual functioning and reduction of anxiety and depressive states as subjective measures, goserelin acetate achieved a statistically significant advantage (P = 0.0001) compared with MPA.  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