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   7169篇
  免费   540篇
  国内免费   13篇
耳鼻咽喉   28篇
儿科学   170篇
妇产科学   83篇
基础医学   1059篇
口腔科学   244篇
临床医学   645篇
内科学   1665篇
皮肤病学   275篇
神经病学   479篇
特种医学   241篇
外科学   1036篇
综合类   123篇
一般理论   4篇
预防医学   637篇
眼科学   248篇
药学   310篇
  1篇
中国医学   5篇
肿瘤学   469篇
  2021年   63篇
  2019年   70篇
  2018年   77篇
  2017年   63篇
  2016年   64篇
  2015年   67篇
  2014年   102篇
  2013年   189篇
  2012年   235篇
  2011年   272篇
  2010年   141篇
  2009年   140篇
  2008年   301篇
  2007年   310篇
  2006年   279篇
  2005年   272篇
  2004年   265篇
  2003年   230篇
  2002年   203篇
  2001年   264篇
  2000年   205篇
  1999年   193篇
  1998年   69篇
  1997年   63篇
  1992年   218篇
  1991年   189篇
  1990年   199篇
  1989年   176篇
  1988年   153篇
  1987年   188篇
  1986年   166篇
  1985年   178篇
  1984年   127篇
  1983年   101篇
  1982年   66篇
  1981年   80篇
  1980年   65篇
  1979年   123篇
  1978年   85篇
  1977年   81篇
  1976年   68篇
  1975年   84篇
  1974年   92篇
  1973年   104篇
  1972年   81篇
  1971年   74篇
  1970年   80篇
  1969年   89篇
  1968年   76篇
  1967年   59篇
排序方式: 共有7722条查询结果,搜索用时 46 毫秒
91.
Epstein-Barr virus (EBV)-specific cytotoxic T cell precursors, present in the circulation of previously infected (seropositive) individuals, have been reactivated in vitro by challenging with autologous EBV-transformed cells, and the reactivated populations subsequently expanded as interleukin 2 (IL2)-dependent cell lines. These lines were dominated by T cells possessing the cytotoxic/suppressor cell surface phenotype and, when tested for effector function in chromium-release assays, demonstrated potent EBV-specific, HLA-A and -B antigen-restricted cytotoxicity even when derived from seropositive donors whose initial cytotoxic response to in vitro reactivation was relatively weak. With all the lines tested from 10 seropositive donors, strong killing of autologous EBV-transformed cells was observed in the absence of any significant lysis of autologous mitogen-stimulated lymphoblasts or of a panel of EBV genome-negative cell lines sensitive to natural killing. Furthermore, the availability of IL2-expanded effectors cell populations allowed their being tested upon a wide panel of allogeneic EBV-transformed targets such that the dominant HLA-restricted reactivities within these populations could be identified. Monoclonal antibody blocking experiments confirmed that lysis of the autologous EBV-transformed cell line by IL2-expanded effectors could be specifically inhibited (a) by pretreatment of the target cells with antibodies binding to the HLA/beta 2-microglobulin complex, and (b) by pretreatment of the effector cells with the cytotoxic/suppressor T cell-specific antibody Leu 2a.  相似文献   
92.
Tardive dyskinesia (TD) is a drug-induced syndrome of involuntary movements often associated with neuroleptic treatment of psychiatric conditions. Huntington's disease (HD) and other neurological conditions are caused by CAG nucleotide repeat expansions in specific genes. We, therefore, explore the hypothesis that TD may be related to CAG repeat expansion by using the repeat expansion detection (RED) method as a measure of CAG content without knowledge of the location of the responsible gene. The number of CAG repeats ([CAG](n)) from persons with schizophrenia or schizoaffective disorders with (n = 10) and without (n = 9) TD are determined. A comparison of [CAG](n) in persons with (56.90 +/- 23.45 repeats) and without (57.00 +/- 19.35 repeats) TD was not statistically different. The total [CAG](n) was determined by combining [CAG](n) for both groups. The median of 45 repeats was used to divide the total into two groups (SG1 and SG2 with smaller and larger [CAG](n) fragments, respectively) and a means analysis of the two subgroups based on [CAG](n) demonstrated that SG1 (n = 10 samples at 45 repeats per sample, mean [CAG](n) = 45.00 +/- 0.00) was significantly smaller than SG2 (n = 9, ranging from 48 to 120 repeats, mean = 70.22 +/- 24.83; P < 0.005). Thus, this lends support to the idea of CAG repeat expansions in the study population. Results are encouraging that a larger population and a more structured subject selection process may yield more meaningful information about the relationship between CAG repeat expansion and TD.  相似文献   
93.
CLB5: a novel B cyclin from budding yeast with a role in S phase.   总被引:50,自引:1,他引:50  
  相似文献   
94.
Tumour cell lines were established in vitro from 16 cases of Epstein-Barr (EB) virus genome-positive Burkitt's lymphoma (BL), 7 of "endemic" origin (i.e. from holoendemic malarial areas of Africa and of New Guinea) and 9 of "sporadic" origin (i.e. from outside such high-incidence areas). All the BL cell lines thus established were monoclonal by immunoglobulin isotype expression and displayed a characteristic chromosomal translocation, t(8:14) or t(8:22), confirming their malignant origin. Clear differences observed between the individual BL cell lines appeared to be related to their endemic or sporadic status. All 7 endemic cell lines began growth as a carpet of single cells, often with small, loose clumps appearing in later passage. Whilst 3 lines of sporadic origin displayed a similar pattern to the above, the majority of sporadic lines grew as large, tight clumps of cells from the first passage onwards. These differences in growth pattern were reflected by differences in cell surface phenotype, as defined in indirect immunofluorescence tests using a panel of monoclonal antibodies (MAbs) specific for B-lineage-associated antigens. BL cell lines could be classified into 3 separate groups on the basis of their reactivity with 6 particular antibodies (MHM6, AC2, Ki-1, Ki-24, J5 and 38.13). All 7 endemic BL cell lines and 2 of the 3 sporadic BL cell lines which began growth as single cells showed a group-I cell-surface phenotype (MHM6, AC2, Ki-1, Ki-24 negative; J5, 38.13 positive) in early passage. In contrast, all 6 sporadic BL cell lines which began growth in large clumps displayed a distinct group-II phenotype (MHM6, AC2, Ki-1 positive/negative; Ki-24, J5, 38.13 positive); in later passage most of these sporadic lines progressed to a group-III phenotype (MHM6, AC2, Ki-1, Ki-24 positive; J5, 38.13 negative) without loss of those immunoglobulin and chromosomal markers identifying the cells' malignant origin. These clear differences between endemic BL cell lines on the one hand and the majority of sporadic BL cell lines on the other suggest that endemic BL arises from a more restricted range of progenitor B cells than does the sporadic form of the disease.  相似文献   
95.
The transperineal percutaneous template permanent iodine interstitial brachytherapy under "C-arm" fluoroscopic guidance is a simple, easily-learned, accurate and rapid procedure which can be performed without subjecting the patient to celiotomy. We have treated 58 patients by the transperineal percutaneous permanent interstitial brachytherapy. The use of transperineal percutaneous technique with C-arm fluoroscopic guidance improves the symmetry and dosimetry of the implant. This results in reduction of the incidence of chronic radiation-induced complications. In the group of 22 patients who underwent brachytherapy without celiotomy and lymphadenectomy and without adjuvant external-beam radiotherapy, there were no major complications.  相似文献   
96.
A massive hemispheric high-grade astrocytoma, diagnosed in a 6-week-old infant, was totally excised by means of two craniotomies. The child is still alive and well with minimal neurological dysfunction 1.5 years after operation. This case report illustrates the benefit of aggressive surgical excision (without radiation or chemotherapy) of massive malignant neonatal astrocytomas. While surgical deficits may be minimized by the plasticity of the developing nervous system, extensive excision may yield occasional long-term palliation.  相似文献   
97.
Toxicologic analysis cannot supplant physician skills in the diagnosis and management of poisoning; however, it is a useful adjunct when properly used. Laboratory use should reflect critical consideration of clinical contribution as well as insight into institutional capability. A detailed historic review and interview of multiple sources may provide more useful and expeditious information than the blind "drug screen." Test ordering should be limited to that which directly contributes to clinical patient management.16 Similarly, test results must be interpreted in the clinical context of patient presentation. The reported units of measurement must be carefully scrutinized; and the potential for laboratory error must be appreciated. Most importantly, communication and cooperation must be maintained between the physician and laboratory personnel if the resource is to be optimally used.  相似文献   
98.
Activities of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase of calf trabecular meshwork were measured and found to be 0.23 and 0.47 mumole/min/g tissue, respectively. Glucose 6-phosphate dehydrogenase was purified 450-fold with a yield of 91% by anion exchange chromatography and 2',5'-ADP agarose affinity chromatography. It was activated by Ca2+, Mg2+, and Mn2+. It was deactivated by p-chloromecuribenzoate, p-chloromercuribenzene sulfonate, and iodoacetamide, but this deactivation could be prevented by pretreatment with cysteine or glutathione. Its rate was regulated by the NADPH/NADP+ ratio, being maximal at a ratio of 0, and negligible at a ratio of 10. At the physiological ratio of 5, its rate was approximately half maximal. On disc gel electrophoresis of both the crude and purified enzyme, seven bands of glucose 6-phosphate dehydrogenase activity could be seen. The isozyme pattern was similar to that of calf retina, but different from that of calf liver. These data suggest that trabecular meshwork is well supplied with the capacity to generate NADPH. Typical demands for NADPH may be to detoxify H2O2 and/or organic peroxides through the glutathione peroxidase/glutathione reductase system, and both generating and removing products of the "killing reaction" during phagocytosis.  相似文献   
99.
The International Labour Office (ILO) classification of radiographs of pneumoconiosis is a standard means of assessing the presence or absence of pneumoconiosis in workers exposed to mineral dusts. Using this classification, 200 admission chest radiographs were reviewed on hospitalized patients in an urban university medical center to determine the prevalence and possible significance of "small opacities" in a population without known industrial exposure. Seventy-one men and 129 women were screened with the mean age of 44.2 years (range, 15-84). Thirty-six (18%) of the 200 patients had small opacities at profusion level 1/0 or greater, and this constituted the "positive radiographs" group. Twenty-two patients (11%) with positive radiographs had no documentable dust exposure or other specific medical etiology that would explain the presence of their lung opacities. The high prevalence of small opacities in "normal" older individuals has important implications in the assessment of patients with suspected pneumoconiosis.  相似文献   
100.
Carcinoma of the esophagus with adenoid cystic differentiation   总被引:6,自引:0,他引:6  
J I Epstein  D L Sears  R S Tucker  J W Eagan 《Cancer》1984,53(5):1131-1136
Adenoid cystic carcinoma of the esophagus is a relatively rare lesion which characteristically exhibits a clinically aggressive behavior. In spite of this aggressive nature, it is most often referred to as a counterpart of the more common adenoid cystic carcinoma of salivary gland origin, a comparatively indolent tumor. In this report, the clinical and pathologic findings in a series of six cases of esophageal adenoid cystic carcinomas are contrasted with those of typical salivary gland lesions, and also compared to similar tumors exhibiting "adenoid cystic" differentiation arising in other extrasalivary gland sites. It is concluded that the esophageal tumors, as well as certain similar lesions arising in other extrasalivary gland sites, represent a class of poorly differentiated basaloid neoplasms distinct both clinically and morphologically from the common adenoid cystic carcinoma of salivary gland origin.  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