全文获取类型
收费全文 | 1783篇 |
免费 | 132篇 |
国内免费 | 3篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 75篇 |
妇产科学 | 170篇 |
基础医学 | 241篇 |
口腔科学 | 41篇 |
临床医学 | 144篇 |
内科学 | 389篇 |
皮肤病学 | 38篇 |
神经病学 | 126篇 |
特种医学 | 96篇 |
外科学 | 190篇 |
综合类 | 20篇 |
一般理论 | 1篇 |
预防医学 | 121篇 |
眼科学 | 27篇 |
药学 | 84篇 |
1篇 | |
中国医学 | 2篇 |
肿瘤学 | 137篇 |
出版年
2023年 | 20篇 |
2022年 | 16篇 |
2021年 | 36篇 |
2020年 | 31篇 |
2019年 | 35篇 |
2018年 | 44篇 |
2017年 | 28篇 |
2016年 | 29篇 |
2015年 | 43篇 |
2014年 | 61篇 |
2013年 | 56篇 |
2012年 | 96篇 |
2011年 | 90篇 |
2010年 | 64篇 |
2009年 | 45篇 |
2008年 | 66篇 |
2007年 | 60篇 |
2006年 | 73篇 |
2005年 | 76篇 |
2004年 | 53篇 |
2003年 | 55篇 |
2002年 | 55篇 |
2001年 | 36篇 |
2000年 | 31篇 |
1999年 | 39篇 |
1998年 | 38篇 |
1997年 | 32篇 |
1996年 | 45篇 |
1995年 | 32篇 |
1994年 | 34篇 |
1993年 | 29篇 |
1992年 | 32篇 |
1991年 | 35篇 |
1990年 | 39篇 |
1989年 | 34篇 |
1988年 | 36篇 |
1987年 | 35篇 |
1986年 | 21篇 |
1985年 | 43篇 |
1984年 | 18篇 |
1983年 | 24篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 22篇 |
1977年 | 17篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1968年 | 5篇 |
1967年 | 4篇 |
排序方式: 共有1918条查询结果,搜索用时 15 毫秒
81.
Gene genealogies reveal global phylogeographic structure and reproductive isolation among lineages of Fusarium graminearum, the fungus causing wheat scab 下载免费PDF全文
O'Donnell K Kistler HC Tacke BK Casper HH 《Proceedings of the National Academy of Sciences of the United States of America》2000,97(14):7905-7910
During the past decade, the plant disease called scab or Fusarium head blight of wheat and barley has reached epidemic proportions in North America and elsewhere in the world. Scab is an economically devastating plant disease, not only because it causes significant reduction in seed yields and quality, but also because infested seeds are often contaminated with trichothecene and estrogenic mycotoxins that pose a serious threat to animal health and food safety. To test whether the primary etiological agent of scab, the fungus Fusarium graminearum, is panmictic throughout its range, allelic genealogies were constructed from six single-copy nuclear genes from strains selected to represent the global genetic diversity of this pathogen. Excluding one hybrid strain, all six genealogies recovered the same seven biogeographically structured lineages, suggesting that they represent phylogenetically distinct species among which gene flow has been very limited during their evolutionary history. Parsimony analysis of the combined data set comprising 7,120 aligned nucleotide characters resolved most relationships among the seven lineages of the F. graminearum clade and related fusaria included in the study. Phylogenetic evidence is also presented for introgressive hybridization and intragenic recombination among lineages of the F. graminearum clade in nature. 相似文献
82.
A detrimental effect of transient elevation of plasma prolactin (PRL) during in vitro fertilization (IVF) has not been proven; however, treatment with a dopamine agonist has been suggested. The present study was undertaken to determine if transient, midcycle hyperprolactinemia exerted a deleterious effect on the number of oocytes retrieved or on fertilization of oocytes in vitro. Fifty-three infertile patients with midcycle hyperprolactinemia (PRL>20 g/liter) during ovarian hyperstimulation for IVF were compared with 53 matched controls who remained normoprolactinemic. Mean (±SE) serum PRL levels on the day after hCG were significantly higher in the study group (29.5±1 g/liter) than in the control (13.1±0.5 g/liter) (P<0.0005), whereas the mean estradiol (E2) concentrations on the same day were not significanily different (4822±287 and 4492±269 pmol/liters, respectively). Fertilization rates (72±4 and 70±4%, respectively) and the mean number of oocytes recovered (4.2±0.3 and 3.7±0.3, respectively) did not differ between the two groups. No correlation was observed between serum PRL and E2 levels, fertilization rates, or the number of oocytes retrieved in either group. Eleven patients with elevated PRL levels as a result of ovarian hyperstimulation were treated with 2.5 mg bromocriptine daily during the next IVF cycle. Serum PRL levels were significantly lower in the treated (5.6±1.8 g/liter) than in the untreated cycles (35.6±3.1 g/liter) (P<0.0005), whereas serum E2 concentrations did not differ. Although the mean number of oocytes recovered was significantly higher in the treated (6.2±1.1) than in the untreated (4.7±0.7) (P<0.02) cycles, the fertilization rates were significantly lower when the patients were treated with bromocriptine compared with the previous untreated cycle (55±8.0 and 76.5±7.0%, respectively;P<0.05). Our data demonstrate that a transient elevation of PRL during ovarian stimulation for IVF does not adversely affect the endocrine response, number of oocytes retrieved, or fertilization rates. No improvement in these parameters was observed in bromocriptine-treated cycles. These results do not support the treatment of transient hyperprolactinemia with dopamine agonists in IVF patients. 相似文献
83.
Prediction of implantation by the sonographic appearance of the endometrium during controlled ovarian stimulation for in vitro fertilization (IVF) 总被引:13,自引:0,他引:13
The texture and the thickness of the endometrium as assessed by transvaginal sonography were prospectively evaluated in 123 patients undergoing IVF treatment. Three different types of endometrial patterns could be distinguished: (A) an entirely homogeneous, hyperechogenic endometrium; (B) an intermediate type characterized by the same reflectivity of ultrasound as the myometrium, with a nonprominent or absent central echogenic line; and (C) a multilayered endometrium consisting of prominent outer and midline hyperechogenic lines and inner hypoechogenic regions. On the day before oocyte retrieval, endometrial thickness was significantly greater in the group of patients who achieved pregnancy than in the group who did not (8.7±0.4 vs 7.5±0.2 mm, respectively; P<0.01) and significantly more patients had multilayered, pattern C, endometrium (75% in pregnant women vs 42.4% in nonpregnant women; P<0.01). No pregnancy occurred when the endometrial thickness was less than 6 mm. When type C endometrium >-6 mm thick was seen, the pregnancy rate per embryo transfer was 39%. When type A or B endometrial pattern was seen, the negative predictive value for the occurrence of pregnancy was 90.5%. Our results suggest that transvaginal sonographic evaluation of endometrial texture and thickness may be an indicator of the likelihood of achieving pregnancy. 相似文献
84.
W C Williard C Collin E S Casper S I Hajdu M F Brennan 《Surgery, gynecology & obstetrics》1992,175(5):389-396
The role of amputation in soft tissue sarcoma of the extremity has decreased at Memorial Sloan-Kettering Cancer Center during the last 20 years. In an attempt to determine the reasons for this change in therapy, an analysis of two separate databases involving 1,057 patients compiled during the periods of 1968 to 1978 and 1982 to 1990 was performed. The patients requiring amputation for soft tissue sarcoma of the extremity in the two databases (n = 233) were compared in an attempt to determine any significant differences between the two time periods. The groups were specifically compared for differences in risk factors, indications for amputations and the effect a decreasing incidence of amputation in the 1982 to 1990 group had on local recurrence and overall survival between the two groups. Despite similarity of risk factors and indications for amputation, the decreased incidence of amputation during the 1982 to 1990 period was associated with a significant decrease in local recurrence after amputation and no significant change in overall survival compared with the 1968 to 1978 group. Absence of local recurrence was associated with significant improvement in survival. Possible reasons for the shift in therapy, as well as the present and future role of amputation in soft tissue sarcoma of the extremity, are discussed. 相似文献
85.
Dysphonia in the aging: physiology versus disease. 总被引:5,自引:0,他引:5
A chart review from 151 dysphonic patients over the age of 60 was done to define aging related voice disorders. Overwhelmingly, patients suffered from dysphonia due to disease processes associated with aging rather than to physiologic aging alone. These include: 1. central neurological disorders affecting laryngeal function (e.g., stroke, Parkinson's disease, essential tremor, Alzheimer's disease); 2. benign vocal fold lesions (e.g., Reinke's edema, benign and dysplastic epithelial lesions); 3. inflammatory disorders (e.g., laryngitis sicca, medication effect); 4. laryngeal neoplasia; and 5. laryngeal paralysis. Typical laryngeal findings of vocal fold bowing and breathiness consistent with presbylarynges were present in only six patients. Presbylarynges is not a common disorder and should be a diagnosis of exclusion made only after careful medical and speech evaluation. 相似文献
86.
In a retrospective study pregnancy and labour after cerclage had been studied in comparison to 160 patients with singleton pregnancies and a matched pair control group of multiple pregnancies without operative cervix closure. Cervical incompetence in multiple pregnancy observed more frequently than in singleton ones is not correlated to obstetric history, but has a bad prognosis because of necessity of tocolysis during pregnancy, marked shortening of duration of pregnancy, lowering of length and weight of newborns. An increase in frequency of amniotic infections had to be calculated following cerclage in multiple pregnancies, too. Our results especially in multiple pregnancies are not so optimistic. This statement is valid also for the indication to its prophylactic use. 相似文献
87.
J T Casper R R Truitt L A Baxter-Lowe R C Ash 《The American journal of pediatric hematology/oncology》1990,12(4):434-448
For young adults and children who have a bone marrow donor who is a genotypic or phenotypic sibling match, bone marrow transplantation is now the preferred treatment for severe aplastic anemia. For those who lack such a matched donor, use of matched unrelated donors and family member donors who are mismatched for a single HLA antigen have been successful and appear to be the treatment of choice. Patients lacking either of these alternatives should receive antilymphocyte globulin, either alone or combined with cyclosporine as a first step. Although the success rate of marrow transplants in our series using mismatched family donors is similar to that following treatment with antilymphocyte globulin, several caveats must be kept in mind. First, the results reported with use of alternative donors must be confirmed with study of larger numbers of patients and longer follow-up. Second, the preparative regimen given prior to bone marrow transplantation destroys the patient's residual bone marrow, whereas antilymphocyte globulin cyclosporine A and androgens do not. The sequence of immunosuppression followed by transplantation with alternative donor marrow should produce greater long-term hematopoietic improvement. Unfortunately, when marrow transplant follows one or more courses of immunosuppressive therapy, nonengraftment is then a problem because of sensitization to blood cell antigens. It should also be kept in mind that studies done in children, especially in those younger than 6 years old, show that these patients respond better to transplantation than to treatment regimens not including marrow transplantation. Therefore, for the child with severe aplastic anemia, every effort should be made to identify a suitable bone marrow donor. Finally, we need to determine the specific components of the conditioning regimen and the constitution of the donor marrow necessary for engraftment and to minimize potential long-term complications, and there should be only a tolerable degree of graft-versus-host disease. Many of the transplant-related problems that plagued us in the 1970s have still not been fully resolved, but many have shown improvement. As we enter the 1990s, increasing the pool of marrow donors for patients with severe aplastic anemia who lack an HLA-matched sibling will continue to be a top priority for research. 相似文献
88.
KH Mak ES Ang ASW Goh KX Na FX Sundram ATH Tan 《Journal of Medical Imaging and Radiation Oncology》1995,39(2):112-117
Technetium-99m hexakis-2-methoxy-isobutyl-isonitrile(99mTc sestamibi) has been used for myocardial perfusion imaging in the evaluation of coronary artery disease (CAD) since 1990. The experience of its use in an Asian population with and without previous myocardial infarction (Ml), diabetes mellitus (DM), hypertension (HPT) and collateral circulation (COL) is reported. One hundred and thirty-nine patients who underwent treadmill exercise testing with 99mTc sestamibi single photon emission computed tomography (SPECT) and coronary angiogram were studied. The overall sensitivity for the detection of CAD was 91.0% and specificity was 64.7%. For patients without previous myocardial infarction, the sensitivity was 83.8% and specificity was 83.3%. Patients with COL had a higher sensitivity while those with HPT had a lower specificity. Sensitivity was higher in patients with multi-vessel disease (MVD) than single vessel disease (SVD). The overall detection for individual artery stenosis was 74.1% with a specificity of 73.1 %. Amongst the three major coronary arteries, sensitivity was highest for the right coronary artery and specificity was highest for the left circumflex artery. Specificity was higher in patients without MI or COL. We found that the agreement between 99mTc sestamibi SPECT and coronary angiogram for the extent of CAD was only 52.5%. The concordance rate was higher for patients with MVD than SVD. It is concluded that 99mTc sestamibi SPECT is a sensitive and specific test for the detection of CAD and localization of disease to individual coronary arteries in our patients with some differences in the subgroups. Agreement between coronary angiogram and 99mTc sestamibi for the extent of coronary artery disease was also satisfactory. 相似文献
89.
90.
L A Shatford M T Hearn A A Yuzpe S E Brown R F Casper 《American journal of obstetrics and gynecology》1988,158(5):1099-1107
We describe a study designed to assess the role of infertility diagnosis in differentiating participants in an in vitro fertilization program on psychological variables. Three hundred forty-eight in vitro fertilization candidates representative of five diagnostic categories (tubal problems, endometriosis, male factor, multiple factors, and idiopathic) underwent psychological assessment before entering the in vitro fertilization program. Measures of personality functioning, depression, anxiety, social support, coping ability, and marital adjustment were obtained. Analyses revealed significant differences among diagnostic groups on several psychological measures. As well, candidates were categorized as having either organic or functional (idiopathic) infertility, and analyses revealed several differences between these two groups. Results suggest ways of providing individualized psychological support in vitro fertilization participants. 相似文献