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   5934篇
  免费   332篇
  国内免费   49篇
耳鼻咽喉   47篇
儿科学   109篇
妇产科学   165篇
基础医学   1032篇
口腔科学   169篇
临床医学   441篇
内科学   968篇
皮肤病学   119篇
神经病学   621篇
特种医学   219篇
外国民族医学   1篇
外科学   629篇
综合类   22篇
预防医学   777篇
眼科学   125篇
药学   438篇
中国医学   15篇
肿瘤学   418篇
  2022年   52篇
  2021年   100篇
  2020年   66篇
  2019年   84篇
  2018年   108篇
  2017年   95篇
  2016年   91篇
  2015年   106篇
  2014年   169篇
  2013年   188篇
  2012年   319篇
  2011年   352篇
  2010年   191篇
  2009年   160篇
  2008年   288篇
  2007年   313篇
  2006年   256篇
  2005年   328篇
  2004年   306篇
  2003年   252篇
  2002年   278篇
  2001年   196篇
  2000年   204篇
  1999年   165篇
  1998年   75篇
  1997年   60篇
  1996年   50篇
  1995年   59篇
  1994年   33篇
  1992年   78篇
  1991年   73篇
  1990年   100篇
  1989年   86篇
  1988年   67篇
  1987年   64篇
  1986年   71篇
  1985年   74篇
  1984年   53篇
  1983年   57篇
  1980年   29篇
  1979年   66篇
  1978年   34篇
  1977年   32篇
  1975年   29篇
  1974年   39篇
  1973年   31篇
  1972年   33篇
  1971年   33篇
  1969年   39篇
  1968年   29篇
排序方式: 共有6315条查询结果,搜索用时 62 毫秒
81.
This study aims to investigate whether the immunohistochemical levels of expression of galectin-3 and the macrophage migration inhibitory factor (MIF) are associated with prognostic values in human colorectal tumors. This was performed on 99 specimens including 69 colorectal tumors (17 Dukes A, 19 Dukes B, 15 Dukes C and 18 metastatic tumors that we labeled as D), 10 hepatic metastases from colorectal cancers and 20 normal specimens (biopsies). The immunohistochemical levels of expression of MIF and galectin-3 were quantified on routine histological slides by means of computer-assisted microscopy. Separate analyses were performed on epithelial and connective tissue. The levels of expression of both MIF and galectin-3 were very significantly higher in epithelial tumor tissue when compared with normal epithelial specimens. A positive and significant correlation between MIF and galectin-3 expression was evidenced in connective tumor tissue, and in particular in the cases associated with short survival periods (less than 5 years). In the case of the Dukes A or B tumors, we established two new prognostic groups (labeled I and II) on the basis of the levels of galectin-3 expression measured in the tumor epithelium. In the case of the Dukes C or D tumors, we established two other prognostic groups (labeled III and IV) on the basis of the levels of MIF expression measured in the connective tissue. Kaplan-Meyer analyses confirmed the additional prognostic values (as compared with conventional clinical staging) given by this new classification (groups I to IV). They show that the Dukes A or B tumors characterized by low levels of galectin-3 expression in the tumor epithelium are associated with significantly better prognoses than those characterized by high levels. In addition, the Dukes C or D tumors characterized by high levels of MIF expression in the connective tumor tissue are associated with significantly better prognoses than those characterized by low levels. In conclusions, MIF and galectin-3 expression levels in colorectal tumors are related to their levels of biological aggressiveness. These markers could be used to identify patients at risk, for whom more aggressive adjuvant therapy seems to be indicated.  相似文献   
82.
N-(2-mercaptoethyl)-lt3-diaminopropane (WR1065) protects againstradiation-induced cell killing and mutagenesis at the hypoxanthine-guaninephosphoribosyl transferase (HGPRT) locus in V79 Chinese hamsterhing fibroblast cells. At a concentration of 4 mM, WR1065 wasfound to be effective in protecting against radiation-inducedcell lethality only if present during irradiation, e.g., a dosemodification factor (DMF) of 1.9. No protective effect was observedif the protector was added within 5 min after irradiation or3 h later, e.g., DMFs of 1.0 and 1.1, respectively. The effectof WR1065 on radiation-induced mutation, expressed as resistanceto the cytotoxic purine analogue 6-thioguanine (HGPRT), wasalso investigated. In contrast to the treatment-schedule dependencefor protection by WR1065 against cell killing, this agent waseffective in reducing radiation-induced mutations regardlessof when it was administered. Following a dose of 10 Gy of 60Co-rays, the mutation frequencies observed per 106 survivors were77 ± 8, 27 ± 6, 42 ± 7, and 42 ±7 for radiation only, and WR1065 present during, immediatelyafter, or 3 h after irradiation. These data suggest that althougha segment of radiation-induced damage leading to reproductivedeath cannot be modulated through the postirradiation actionof WR1065, processes leading to the fixation of gross geneticdamage and mutation induction in surviving cells can be effectivelyaltered and interfered with leading to a marked reduction inmutation frequency.  相似文献   
83.
Death with a functioning graft and death‐censored renal allograft failure remain major problems for which effective preventative protocols are lacking. The retrospective cohort study aimed to determine whether histologic changes on a 5‐year surveillance kidney biopsy predict adverse outcomes after transplantation in recipients who had: both Type 2 diabetes (T2DM) and obesity (BMI ≥ 30 kg/m2) at the time of transplantation (T2DM/Obesity, n = 75); neither (No T2DM/No obesity, n = 78); No T2DM/Obesity (n = 41), and T2DM/No obesity (n = 47). On 5‐year biopsies, moderate‐to‐severe mesangial expansion was more common in the T2DM/Obesity group (Banff mm score ≥2 = 49.3%; Tervaert classification MS ≥ 2b = 26.7%) compared to the other groups (p < .001 for both scores). Risk factors included older age, higher BMI, HbA1C, and triglycerides at 1‐year post‐transplant. Moderate‐to‐severe mesangial expansion correlated with death with function (HR 1.74 (1.01, 2.98), p = .045 Banff and 1.89 (1.01, 3.51) p = .045 Tervaert) and with death‐censored graft loss (HR 3.2 (1.2, 8.8), p = .02 Banff and HR 3.8 (1.3, 11.5), p = .01 Tervaert) over a mean of 11.6 years of recipient follow‐up post‐transplant. These data suggest that mesangial expansion in recipients with T2DM and obesity may reflect systemic vascular injury and might be a novel biomarker to predict adverse outcomes post renal transplant.  相似文献   
84.
Patients with chronic myelofibrosis often suffer from osteosclerosis, which is associated with bone pain and may lead to bone marrow failure. The pathogenesis of myelofibrosis is linked to aberrant megakaryocyte development and function. Null and loss-of-function mutations in MPIG6B, which codes for the inhibitory heparan sulfate receptor G6b-B, result in severe macrothrombocytopenia, large megakaryocyte clusters, and focal primary myelofibrosis in mice and humans. We investigated the development of osteosclerosis in Mpig6b null (Mpig6b−/−) mice. Although male and female Mpig6b−/− mice presented with elevated bone marrow megakaryocyte number and macrothrombocytopenia, female Mpig6b−/− mice developed progressive splenomegaly starting at 8 weeks of age. Micro–computed tomography (μCT) of femurs showed that female Mpig6b−/− mice had increased cortical thickness and reduced bone marrow area starting at 8 weeks of age and developed occlusion of the medullary cavity by trabeculae by 16 weeks of age. In contrast, male Mpig6b−/− mice developed only a small number of trabeculae in the medullary cavity at the proximal diaphysis and demonstrated a temporary decrease in bone volume fraction and trabecular thickness at 16 weeks. Ovariectomy of 10-week-old female Mpig6b−/− mice prevented the development of medullary cavity osteosclerosis, whereas orchiectomy of male Mpig6b−/− mice did not exacerbate their disease. Importantly, ovariectomized female Mpig6b−/− mice also demonstrated improvement in spleen weight compared to sham-operated Mpig6b−/− mice, establishing estrogen as a contributing factor to the severity of the megakaryocyte-driven osteosclerosis. © 2021 American Society for Bone and Mineral Research (ASBMR).  相似文献   
85.
BackgroundTo evaluate whether stone extraction with a loop ureteral catheter (LUC) in distal ureteral stones is associated with a higher frequency of ureteral strictures compared to treatment with primary ureteroscopic stone removal (p-URS) or ureteroscopic laser lithotripsy (l-URS).MethodsFive hundred and forty-seven consecutive patients were primarily endourologically treated for distal ureteral stones in our department between 2005 and 2019 and included in the study protocol. Data was retrospectively obtained from the patients’ charts and medical reports as well as from office-based urologists. Data analysis was performed using Fisher’s exact test, Mann-Whitney test or Student’s t-test as appropriate. A level of P<0.05 was assigned statistical significance.ResultsFour hundred and twelve patients were treated by URS (p-URS n=304, l-URS n=108) and another 135 by LUC stone extraction. Median follow-up was 41 [2–159] months. There was no difference between the groups concerning age, gender, proportion of patients with ureteral stenting, operating time, hospitalization or readmission rates. The number of ureteric strictures was small in all procedures [n=3 (1.0%) in p-URS, n=2 (1.9%) in l-URS and n=2 (1.5%) in LUC] and there was no difference between the groups concerning this serious complication (p-URS vs. LUC: P=0.6465; l-URS vs. LUC: P=0.9999).ConclusionsIn small distal stones, LUC stone extraction still is an alternative to URS procedures in stone management with comparable results concerning postinterventional ureteral strictures. In experienced hands, it still has its value in accurately selected patients.  相似文献   
86.
Members of the filamentous fungal genus Fusarium are among the agents most frequently causing keratomycosis in humans. Fusarium keratitis is most common among agricultural workers in geographical regions with hot, humid, tropical or semi-tropical climates, but can occur more rarely in countries with temperate climates, such as Hungary. Keratitis is usually treated with a topical antifungal agent, sometimes in combination with sub-conjunctival injections and/or antimycotic agents, but therapeutic keratoplasty may be needed for patients whose corneal infection does not resolve. Early and accurate diagnosis, coupled with appropriate antifungal therapy, is crucial for improving the chances of complete recovery.  相似文献   
87.
Intracytoplasmic sperm injection in the mouse   总被引:9,自引:0,他引:9  
Intracytoplasmic sperm injection (ICSI) into mouse oocytes involvesa very low survival rate. This study was designed to determinewhy ICSI frequently fails in mice. Metaphase II oocytes wereobtained from superovulated 4–6 week old F1 hybrid mice.Spermatozoa were retrieved from the epididymis of 12–14week old F1 hybrid mice. The spiked microinjection pipette usedto inject a spermatozoon into the ooplasm had outer and innerdiameters of 10 and 8 µm respectively. The oocytes usedin the first part of the study were not activated (group 1).Some oocytes were incubated with calcium ionophore for 5 min(group 2). The injected oocytes were evaluated 6, 20, 48 and72 h after injection. A total of 143 eggs in each group underwentICSI. In group 1, sperm heads escaped into the perivitellinespace. In all, 63 (47%) of the remaining oocytes were damagedduring the injection or had degenerated by the first evaluation.The survival rate was 53%, but fertilization did not occur.In group 2, 31 oocytes (22%) were damaged during microinjectionor soon degenerated. Two oocytes underwent accidental subzonalinsemination. Six oocytes were fertilized (4.2%) among the 78%of survivors. After injection, the sperm tail was found in thecytoplasm (27 and 31% in groups 1 and 2 respectively), the perivitellinespace (45% in both groups) or protruding through the zona pellucida(28 and 23% respectively). More oocytes degenerated when thetail remained in the cytoplasm, i.e. 78% in group 1 and 36%in group 2.  相似文献   
88.
The purpose of this study was to examine the impact of participation in the Wellness--Paths to Health Physical Fitness Program on selected physiological and personal health variables including blood pressure, pulse, body weight, trunk flexibility, cardiovascular endurance, abdominal strength, percent body fat and a cumulative fitness score. The subjects (N = 129) of this study were divided into four levels of adherence to this exercise-based health program. Data analysis examined relationships between adherence levels and changes in the selected physiological and personal health variables across two measures. In addition, data from high-risk participants were analyzed. The results of the study found statistical significant changes in the selected variables between repeated assessment measures. In addition, statistically significant relationships were found between levels of adherence to the program and six of the dependent variables.  相似文献   
89.
The effects of AN-207, a new targeted cytotoxic analog of LH-RH, were evalued in rats bearing hormone-dependent Dunning R-3327-H prostate carcinomas. AN-207 consists of the agonist [D-Lys(6)]LH-RH linked to 2-pyrrolino-doxorubicin, an intensely potent derivative of doxorubicin. In the first experiment, 2-pyrrolinodoxorubicin was administered at a concentration of 50 nmol/kg, as a single drug (AN-201) and as an unconjugated mixture with [D-Lys(6)]LH-RH or conjugated to the carrier [D-Lys(6)]LH-RH (AN-207). Following the second administration of radical AN-201 alone or mixed with the carrier, all rats died with signs of general toxicity, but all animals treated with the conjugate AN-207, survived. After 5 weeks of treatment with a total dose of 150 nmol/kg AN-207, the tumors regressed from an initial volume of 8.35 +/- 1.7 cm(3) to 4.47 +/- 0.8 cm(3), while tumors in the control group measured 17.84 +/- 2.2 cm(3). The therapy with AN-207 also significantly reduced tumor weight and tumor burden. In the second experiment, we compared the efficacy and toxicity of 3 injections of 25 nmol/kg AN-201 or 25 nmol/kg and 50 nmol/kg AN-207. The initial tumor volume in all groups was between 3.9 and 4.5 cm(3). After 5 weeks of therapy, the tumors of rats treated with 50 nmol/kg AN-207 regressed to 2.3 +/- 0.51 cm(3), whereas 25 nmol/kg AN-201 was still toxic in contrast to 25 nmol/kg AN-207, while the reduction in final tumor volume was similar (6.76 +/- 1.4 cm(3) and 6.74 +/- 1 cm(3), respectively), as compared to 15.6 +/- 2.2 cm(3) for untreated animals. High capacity LH-RH receptors were found in the membranes of untreated Dunning tumor specimens, but after treatment with AN-207, they could no longer be detected. This is the first demonstration that the new targeted cytotoxic LH-RH analog AN-207 is an effective antitumor agent. Our work indicates that the cytotoxic analog AN-207 is much less toxic than the antineoplastic radical (AN-201) incorporated, and significantly more active in inhibiting tumor growth. Further development of approaches based on targeted cytotoxic analog AN-207 may lead to major improvements in current palliative therapy of prostate cancer.  相似文献   
90.
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