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   1769篇
  免费   99篇
  国内免费   18篇
耳鼻咽喉   18篇
儿科学   31篇
妇产科学   7篇
基础医学   215篇
口腔科学   21篇
临床医学   102篇
内科学   477篇
皮肤病学   2篇
神经病学   115篇
特种医学   48篇
外科学   390篇
综合类   6篇
预防医学   33篇
眼科学   39篇
药学   147篇
中国医学   7篇
肿瘤学   228篇
  2023年   19篇
  2022年   41篇
  2021年   72篇
  2020年   35篇
  2019年   31篇
  2018年   50篇
  2017年   29篇
  2016年   46篇
  2015年   49篇
  2014年   58篇
  2013年   61篇
  2012年   92篇
  2011年   103篇
  2010年   56篇
  2009年   38篇
  2008年   90篇
  2007年   92篇
  2006年   75篇
  2005年   83篇
  2004年   78篇
  2003年   101篇
  2002年   88篇
  2001年   52篇
  2000年   43篇
  1999年   38篇
  1998年   32篇
  1997年   18篇
  1996年   19篇
  1995年   14篇
  1994年   17篇
  1993年   10篇
  1992年   19篇
  1991年   19篇
  1990年   16篇
  1989年   15篇
  1988年   15篇
  1987年   21篇
  1986年   20篇
  1985年   21篇
  1984年   29篇
  1983年   10篇
  1982年   7篇
  1980年   7篇
  1979年   8篇
  1978年   5篇
  1976年   5篇
  1975年   10篇
  1974年   6篇
  1972年   5篇
  1971年   4篇
排序方式: 共有1886条查询结果,搜索用时 10 毫秒
1.
In this study, we used a novel 4-fluid nozzle spray drier to prepare composite microparticles of a water-insoluble drug, flurbiprofen (FP), and a water-soluble drug, sodium salicylate (SS), for the purpose of improving the water solubility of FP. An ethanol solution of FP and an aqueous SS solution were simultaneously introduced through different liquid passages in the 4-fluid nozzle spray drier and then spray-dried. Quantitative elemental analysis suggested that the FP/SS ratio in each composite microparticle was nearly the same as the formulation ratio. We also found that SS and FP exist in a low crystallinity state in the composite particles. Release of FP from dissolved composite microparticles was markedly improved because of an increase in the effective surface area following rapid dissolution of SS. This study shows that it is possible to prepare FP-SS composite microparticles using a 4-fluid nozzle spray drier in single process and that this can improve the ability of FP to dissolve in water.  相似文献   
2.
Fetal tissues from time-pregnant female A/J mice of 16- and 19-day pregnancies and from neonates 1 day after birth, as well as from fetal cells in culture, absorbed significant amounts of anti-epiglycanin antibody. Detergent-solubilized glycoproteins, with epiglycanin activity, from fetal tissues and cells were separated by polyacrylamide gel electrophoresis, and the protein bands electroblotted onto a nitrocellulose gel. After the antigens were labeled with rabbit anti-epiglycanin antiserum and [125I]epiglycanin, autoradiography revealed two major bands containing the antigenic determinant at Mr 90,000 and 82,000. Bands of similar molecular weights, but with no demonstrated immunologic cross-reactivity, were observed by fluorography, if intact cells prior to solubilization were labeled by galactose oxidase followed by sodium borotritiide. Immunoreactive epiglycanin activity could be destroyed by Pronase, endo-N-acetyl-alpha-D-galactosaminidase (Diplococcus pneumoniae), or periodate oxidation. Activity was enhanced with neuraminidase. The spleen, liver, or erythrocytes from adult A/J mice did not possess the antigen, but incubation of adult spleen or liver with neuraminidase (Vibrio cholerae) exposed the epitope.  相似文献   
3.
4.
Effects of trichostatins on differentiation of murine erythroleukemia cells   总被引:8,自引:0,他引:8  
M Yoshida  S Nomura  T Beppu 《Cancer research》1987,47(14):3688-3691
The fungistatic antibiotics trichostatins (TS) A and C were isolated from culture broth of Streptomyces platensis No. 145 and were found to be potent inducers of differentiation in murine erythroleukemia (Friend and RV133) cells at concentrations of 1.5 X 10(-8) M for TSA and 5 X 10(-7) M for TSC. Differentiation induced by TS was cooperatively enhanced by UV irradiation but not by treatment with dimethyl sulfoxide. This enhanced activity was completely inhibited by adding cycloheximide to the culture medium 2 h after exposure to TS, suggesting that TS are dimethyl sulfoxide-type inducers of erythroid differentiation. No inhibitory effect of TS was observed on macromolecular synthesis in cultured cells.  相似文献   
5.
We report herein a case of spontaneous subcapsular hepatic hemorrhage which occurred in a 33-year-old woman 1 day after she had been delivered of her second child by cesarean section following an uneventful pregnancy. She complained of right upper quadrant pain on the 1st postoperative day, and computed tomography (CT) showed subcapsular low-density masses in both liver lobes, while extravasation was demonstrated by CO2 intraarterial digital subtraction angiography (IADSA). The hemorrhage was successfully controlled by transcatheter arterial embolization (TAE). However, on the 3rd day after TAE, an exploratory laparotomy was performed to establish an exact diagnosis to explain the persistent abdominal pain and abnormal liver function tests. Subcapsular hematomas in both lobes were confirmed and no visible laceration was present. The patient recovered gradually by spontaneous absorption of the hematomas and was discharged on the 22nd postoperative day. Spontaneous hepatic hemorrhage associated with pregnancy is a very rare complication, and establishing a correct diagnosis and initiating appropriate therapy are essential for this life-threatening disease.  相似文献   
6.
Mucin-producing tumor in the bile duct is referred to clinically as mucin-producing bile duct tumor (MPBT). Intraductal papillary neoplasm of the biliary tract that resembles an intraductal papillary mucinous neoplasm (IPMN) of the pancreas is a rare category of MPBT and is not well characterized. We, herein, report a case of MPBT of the caudate lobe of the liver that showed papillary growth and communicated with the bile duct of the caudate lobe and protruded into the common hepatic duct. Histologically, MPBT cells showed papillary overgrowth with abundant mucinous secretions, resembling an IPMN of the pancreas. The MPBT cells showed the same immunostaining pattern as that of cells from IPMN of the pancreas.  相似文献   
7.
Chronotropic and inotropic effects of histamine were examined in isolated atrial and ventricular preparations from embryonic and hatched chicken hearts. Histamine produced positive chronotropic and inotropic responses both in embryonic and hatched hearts. The responses to histamine in middle embryonic myocardia, which were observed in the micromolar range, were antagonized by H2 antagonists but not by H1, H3 antagonists and propranolol. Isobutylmethylxantine, an inhibitor of phosphodiesterase, produced a leftward shift of the concentration-response curve for the chronotropic effect of histamine in the embryo. The responses to histamine in myocardia from hatched chicks, which were observed in the milimolar range, appeared concurrently with the responses to tyramine during development and were antagonized by beta adrenoceptor antagonists but not by any of the histamine antagonists. The positive inotropic response to histamine in hatched ventricular preparations were greatly attenuated by reserpine pretreatment or in the presence of desipramine. Thus, we demonstrated that exogenously applied histamine produces positive chronotropic and inotropic responses in developing chicken hearts and that the mechanisms are different between embryonic and hatched chicks: direct action on H2 receptors in the embryonic heart and release of norepinephrine from sympathetic nerve terminals in hatched hearts.  相似文献   
8.
Opioid supplements are often required in total intravenous anesthesia (TIVA). Most ϰ-opiate receptors are found in the spinal cord, wherea μ-opiate receptors are widespread throughout the brain and spinal cord. Buprenorphine has a strong μ-action with a minute ϰ-action, while eptazocine stimulates ϰ-receptors only. From these, epidural eptazocine is expected to exert strong spinal analgesia by ϰ-stimulation without μ-action, which produces circulatory and respiratory depression. Therefore, the clinical effects of epidural opioids on circulation, respiration, and analgesia were compared. Continuous epidural administration of eptazocine or buprenorphine was combined with TIVA in patients scheduled for elective abdominal surgery. Epidural opioid administration was continued throughout and for 72h after anesthesia. A significant analgesic effect (P<0.01) of epidural eptazocine without circulatory and respiratory depression was observed. With epidural buprenorphine, circulatory and respiratory depression during and immediately after anesthesia were significant (P<0.05). These results suggest that medullary μ-stimulation by an epidural opioid induces circulatory (hypervagotonicity and hypervagosensitivity) and respiratory depression, while ϰ-stimulation produces only minimal effects on circulatory and respiratory systems.  相似文献   
9.
That Melanesians of non-Austronesian genetic ancestry may be relatively resistant to glucose intolerance was supported by the results of a study of two semitraditional non-Austronesian villages in the Papua New Guinean highlands in 1983, in which an absence of diabetes and a high degree of glucose tolerance and insulin sensitivity were observed. The second of this series of surveys was conducted in 1985 in three non-traditional communities: a periurban, non-Austronesian village in the highlands, and rural and periurban Austronesian villages in coastal locations. Although an absence of diabetes was demonstrated once again in the highlanders, these periurban subjects showed an unexpectedly high insulin response which may be a precursor of glucose intolerance. The notion that highland communities that are living in non-traditional circumstances in Papua New Guinea presently are in "metabolic transition" towards diabetes and other non-communicable diseases, if correct, is of importance to the public health of the nation. In the periurban, coastal-dwelling Austronesians, diabetes with severe hyperglycaemia was demonstrated, and there was some evidence of a secular trend towards increasing glucose intolerance. The two-hour plasma glucose concentrations were shown to be associated with obesity, modernity and Seventh-Day Adventist religious persuasion. However, important and unexplained differences in glucose tolerance remained between rural and periurban coastal dwellers after taking these factors into account.  相似文献   
10.
BACKGROUND: A small number of malignant peripheral nerve sheath tumours (MPNSTs) are low grade, and the nature of these low grade tumours has never been systematically assessed. AIMS: To describe the clinicopathological, immunohistochemical, and ultrastructural features of low grade MPNST and to discuss the main differential diagnoses. METHODS: Four cases of low grade MPNST were studied, including one coexistent with neurofibromatosis type 1. The tumours were analysed with respect to nuclear atypia, cellularity, nuclear enlargement, hyperchromasia, mitotic rate, and necrosis. Immunohistochemistry was performed by standard techniques, and an ultrastructural study was performed on one tumour. RESULTS: The ages of the patients ranged from 32 to 72 years (mean, 58). Two were male and two were female. Three tumours occurred in the deep tissue, including one in the retroperitoneum, and one was located in the dermal and subcutaneous tissue. The maximum diameters of the tumours ranged from 3.5 to 8.0 cm. Microscopically, all tumours showed moderate hypercellularity, an increased nuclear to cytoplasmic ratio, and hyperchromasia, but exhibited varied growth patterns, including those that were atypical neurofibroma-like, low grade fibromyxoid sarcoma-like, low grade epithelioid, and haemangiopericytoma-like. All tumours showed immunoreactivity for S-100 protein and vimentin. CONCLUSIONS: These findings suggest that careful clinical and histological evaluation, along with S-100 protein immunostaining, are essential for the accurate diagnosis of low grade MPNST.  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