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   3497篇
  免费   194篇
  国内免费   4篇
耳鼻咽喉   17篇
儿科学   177篇
妇产科学   61篇
基础医学   465篇
口腔科学   58篇
临床医学   223篇
内科学   616篇
皮肤病学   87篇
神经病学   236篇
特种医学   92篇
外科学   391篇
综合类   204篇
一般理论   1篇
预防医学   247篇
眼科学   49篇
药学   292篇
中国医学   15篇
肿瘤学   464篇
  2023年   15篇
  2022年   40篇
  2021年   97篇
  2020年   55篇
  2019年   48篇
  2018年   76篇
  2017年   56篇
  2016年   81篇
  2015年   82篇
  2014年   110篇
  2013年   156篇
  2012年   221篇
  2011年   233篇
  2010年   170篇
  2009年   108篇
  2008年   191篇
  2007年   182篇
  2006年   175篇
  2005年   142篇
  2004年   138篇
  2003年   138篇
  2002年   134篇
  2001年   117篇
  2000年   89篇
  1999年   83篇
  1998年   29篇
  1997年   25篇
  1996年   18篇
  1995年   26篇
  1994年   21篇
  1993年   27篇
  1992年   46篇
  1991年   48篇
  1990年   40篇
  1989年   30篇
  1988年   34篇
  1987年   25篇
  1986年   24篇
  1985年   24篇
  1984年   21篇
  1983年   25篇
  1979年   27篇
  1977年   17篇
  1976年   19篇
  1975年   15篇
  1974年   17篇
  1973年   16篇
  1972年   15篇
  1971年   16篇
  1968年   13篇
排序方式: 共有3695条查询结果,搜索用时 31 毫秒
31.
BackgroundInjuries involving upper cervical spine are serious and fatal injuries which are associated with alteration of normal occipital–cervical anatomy. These injuries may result in permanent neurologic deficits or neck deformity if not treated in a timely and appropriate manner.ObjectiveTo evaluate the outcomes of neglected upper cervical spine injuries treated by various methods.Study designRetrospective study.Materials and methodsTwelve patients attending ER or OPD with a history of neck trauma and who were diagnosed with fractures and fracture dislocations C1 and C2 were included in the study. Fresh injuries sustained within a week were excluded from study. The outcomes were measured in terms of improvement in VAS, ODI Scores and correction of the neck deformity. Surgical parameters like duration of surgery and blood loss were also observed.ResultsEleven males and one female. The mean age was 40.9 ± 16.9 (07–67 years). Eleven patients underwent posterior instrumentation, while one patient was treated anteriorly. The mean delay in presentation was 28 ± 8.67 days (15–42 days). The mean duration of surgery was 188.3 ± 34.35 min (120–240 min), average blood loss was 350 ± 111.8 ml (150–600 ml). The mean VAS improved from 8.45 ± 0.89 to 3.9 ± 0.51 (p < 0.05). The mean ODI Pre-operatively was 88.45 ± 5.89 which improved to 31.9 ± 4.01 (p < 0.05). The neck deformity/torticollis was corrected in all the patients.ConclusionsNeglected upper cervical spine injuries are difficult to treat and a posterior approach is helpful in reducing the subluxations indirectly and to obtain a posterior fusion.  相似文献   
32.
Mammary tumors of a newly isolated strain of Chinese wild mouse (JYG mouse) harbor exogenous mouse mammary tumor virus (MMTV). The complete nucleotide sequence of exogenous JYG-MMTV was determined on the proviral 5' long terminal repeat (LTR)(partial)-gag-pol-env-3' LTR (partial) fragment cloned into a plasmid vector and the cDNA sequence from JYG-MMTV producing cells. Similarly to the other MMTV species the LTR of JYG-MMTV contains an open reading frame (ORF). The amino acid sequence of the JYG-MMTV ORF resembles that of SW-MMTV (92% identity) and endogenous Mtv-7 (93% identity) especially at the C-terminal region. Thus, a functional similarity in T-cell receptor V beta recognition as a superantigen is implicated among these MMTV species. Analysis of the viral gag nucleotide sequence revealed that this gene is not disrupted by the bacterial insertion sequence IS1 or IS2, which have been reported to be present in the majority of the plasmids containing the gag region. Comparison of amino acid sequences of JYG-MMTV with those of BR6-MMTV showed that over 96% of the amino acids of gag, pol, protease and env products are identical. These results suggest the intact nature of the nucleotide sequence of the near full-length MMTV genome cloned in the plasmid.  相似文献   
33.
Frautschy SA  Sarkar DK 《Endocrine》1995,3(4):273-275
The role of estrogen in the regulation of hypothalamicβ-endorphin hormone secretion is studied by determiningβ-endorphin concentration in pituitary portal plasma of ovariectomized rats in the presence or absence of this steroid and/or the opioid antagonist naloxone. Twenty-six hours following s.c. injection of 10 /μg estradiol benzoate (estrogen) or oil, rats anesthetized with Saffan (alphaxolone/alphadolone) underwent pituitary stalk exposure and hypophysectomy, after which pituitary portal blood was continuously collected and stored in 15 min aliquots from 1100-1400 h. At 1100 h, animals were given an initial bolus iv injection of naloxone or saline (naloxone, 2 mg/ kg, or saline, 0.1 ml) and then infused (iv) continuously with naloxone (2 mg/kg/h) or saline (0.8 ml/h) until 1400 h. Plasma samples were extracted and assayed by radioimmunoassay forβ-endorphin. Treatment with estrogen increased the meanβ-endorphin levels twofold as compared to oil-treated controls. Naloxone potentiated estrogen action ofβ-endorphin secretion, but did not affect basalβ-endorphin secretion. These results suggest that estrogen enhancedβ-endorphin secretion from the hypothalamus. Furthermore, the hypersecretion ofβ-endorphin induced by naloxone with, but not without, estrogen supports the existence of an estrogen-activated short-loop negative feedback mechanism regulatingβ-endorphin secretion.  相似文献   
34.
The effect of alcohol on estrogen-regulated lactotropic cell proliferation was examined in Fisher 344 rats. Alcohol was administered for 2 weeks using liquid diet containing 8.7% ethanol (v/v) and 37% ethanol-derived calories. The control group was pair-fed with an isocaloric diet minus the ethanol or adlib-fed with normal diet. Ethanol-treated rats showed mean blood ethanol concentrations between 60-90 mg/dl. Alcohol treatment did not effect the body growth rate, but increased the DNA synthesis in lactotropes and reduced the levels of lactotropic growth inhibitory transforming growth factor-beta 1 (TGF-beta 1) protein and mRNA in the pituitary. These results suggest that alcohol promotes estrogen-induced lactotropic proliferation, possibly by down regulating the inhibitory TGF-beta 1 control of lactotropic function.  相似文献   
35.
Highly aggressive murine B16 melanoma was engineered to secrete IFN-alpha constitutively. Cells expressing IFN-alpha were injected into syngeneic C57BL/6 mice and the mice were monitored for tumor development. Secretion of IFN-alpha by B16 melanoma cells completely abrogated their tumorigenicity in syngeneic mice. LFN-alpha-secreting cells also abrogated the tumorigenicity of IFN-gamma-secreting and TNF-alpha-secreting cells when injected in combination whereas cells secreting either IFN-gamma or TNF-alpha grow progressively in mice when injected alone. Moreover, protected animals developed significant immunity against subsequent challenge with parental cells. Injection of parental cells and IFN-alpha-secreting cells together in a mixed tumor transplantation assay resulted in a significant reduction of tumorigenicity of the parental cells. Histopathological studies of the tissues from the injection site of the mice inoculated with a combination of parental and B16.IFN-alpha cells revealed the existence of a massive cellular infiltrate composed of lymphocytes and granulocytes at an early stage (7-11 days). In the later stages (22 days), no recognizable tumor tissue was detected. Injection of irradiated IFN-alpha-secreting cells in the mice carrying an established tumor completely prevented tumor development in 80% of the treated mice when injection was performed on the same side as the tumors. Injection of irradiated IFN-alpha-secreting cells in the contralateral site showed much less effect on the established tumor. Systemic antitumor effects on the established tumor can be enhanced by using a combination of irradiated IFN-alpha and IFN-gamma secreting cells as a vaccinating inoculum.  相似文献   
36.
37.
38.
Pathologic diagnosis of pancreatic adenocarcinoma is frequently a challenge, particularly in small biopsies, frozen sections, and in metastatic foci. Here we report a deceptively benign-appearing and morphologically distinctive pattern of ductal adenocarcinoma with prominent microvesicular cytoplasm, giving the cells a foamy appearance similar to that described in the prostate (Am J Surg Pathol 1996;20:419). This variant, which we refer to as foamy gland pattern (FGP), was frequently misdiagnosed in frozen sections or biopsies and its pathologic stage underestimated in surgical specimens. Histologically, the diagnostic features were: (1) white and crisply foamy, "microvesicular" cytoplasm; (2) often basally located and compressed, hyperchromatic nuclei reminiscent of endocervical glands (and so-called "adenoma malignum") or gastric foveolar glands; (3) irregular nuclear contours forming wrinkled (raisinoid) nuclei in some areas; and (4) a distinctive chromophilic condensation of the cytoplasmic material in the luminal aspect of the cells forming a brush border-like zone (BLZ). Histochemically, this BLZ was positive for mucicarmine, alcian blue, and high iron diamine, but not PAS. The remainder of the cytoplasm was negative for all these stains. In contrast, benign mucinous ducts, which constitute the major differential diagnosis, had more homogeneous acidophilic cytoplasm, lacked BLZ, and showed cytoplasmic staining with PAS. Immunohistochemically, the tumor cells were diffusely and strongly positive for CEA and cytokeratin 8 whereas B72.3 staining was focal and weak. MUC1 staining was largely confined to the BLZ. MUC2 was negative. P53 staining was detected in 16 of the 20 cases studied and was strong and diffuse in five. K-ras mutation was detected in 6 of 8 cases studied. The clinical findings in the 20 patients in this study (4 pure and 16 mixed with usual ductal carcinoma) did not appear to differ significantly from those of ordinary ductal adenocarcinoma of the pancreas. Eleven patients were men and nine were women; the mean age was 62 years and the mean tumor size was 4.4 cm. Follow-up information was available in 17 patients of whom 7 were alive at an average follow up of 23 months (range, 7-104 mos), and 10 were dead of disease at a median follow up of 15 months (range, 4-42 mos). The median survival of the four patients with pure FGP was 18 months. The median survival did not appear to be significantly longer than that of the patients with resectable ordinary ductal adenocarcinoma in the authors' experience (109 patients, median survival of 12 mos, p = 0.48). In conclusion, foamy gland pattern of invasive pancreatic ductal carcinoma is morphologically distinctive and is prone to misdiagnosis as a benign process. The pathologic stage is often underestimated as a result of the lack of its recognition and misinterpretation as mucinous ducts. Careful attention to its microscopic features is adequate for accurate diagnosis. Histochemical and immunohistochemical stains are useful in confirming the diagnosis of malignancy in challenging cases.  相似文献   
39.
A prospective study of 48 women was carried out to estimate the incidence of common genital pathogens in women referred to colposcopy clinic requiring diathermy loop excision and to compare patient morbidity in the subgroups with and without genital pathogens. Of the 43 women included in the analysis, genital pathogens were present in 24 cases (56%) and absent in 19 (44%) of the 24 positive cases, 19 (79%) women had pathogen(s) on the cervical swab, 24 (100%) had pathogen(s) on the high vaginal swab and 15 (63%) had both a positive cervical and high vaginal swab (HVS). The most frequently isolated groups of organisms were mixed anaerobes, alone (four HVS and four cervical) or in combination with Gardnerella vaginalis (four HVS and three cervical) or coliforms (two HVS and two cervical). The mean duration of bleeding and vaginal discharge in the two study groups was not statistically significant (t value 1.97, P 0.05; and t value 0.48, P 0.5, respectively). However, the mean duration of bleeding graded by the patient as being moderate to severe was significantly different in the two groups (t value 3.18 P 0.01). Fifty-six per cent of the women in the study had confirmed genital pathogens, predominantly anaerobes, and the prolonged moderate-to-severe bleeding in this group suggests a potential role for prophylactic bacteriocides, although the study size was unable to implicate a single pathogen.  相似文献   
40.
Leg ulcer is a leading cause of morbidity among older subjects, especially women in the Western world. About 400 years BC, Hippocrates wrote, "In case of an ulcer, it is not expedient to stand, especially if the ulcer be situated on the leg". Hippocrates himself had a leg ulcer. The best treatment of any leg ulcer depends upon the accurate diagnosis and the underlying aetiology. The majority of leg ulcers are due to venous disease and/or arterial disease, but the treatment of the underlying cause is far more important than the choice of dressing. The aetiology, pathogenesis, treatment, and the future trends in the management of the leg ulcers are discussed in this review.  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