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   1285677篇
  免费   98165篇
  国内免费   2024篇
耳鼻咽喉   18492篇
儿科学   44734篇
妇产科学   35187篇
基础医学   183145篇
口腔科学   33929篇
临床医学   111894篇
内科学   259769篇
皮肤病学   28207篇
神经病学   101039篇
特种医学   51369篇
外国民族医学   660篇
外科学   197255篇
综合类   27089篇
现状与发展   1篇
一般理论   380篇
预防医学   96116篇
眼科学   28048篇
药学   95155篇
  2篇
中国医学   2444篇
肿瘤学   70951篇
  2018年   13326篇
  2017年   10102篇
  2016年   11101篇
  2015年   12587篇
  2014年   17383篇
  2013年   26557篇
  2012年   36525篇
  2011年   38556篇
  2010年   23084篇
  2009年   22084篇
  2008年   37064篇
  2007年   39698篇
  2006年   39871篇
  2005年   38804篇
  2004年   37944篇
  2003年   36710篇
  2002年   36090篇
  2001年   64046篇
  2000年   66527篇
  1999年   56456篇
  1998年   15178篇
  1997年   13803篇
  1996年   14240篇
  1995年   13480篇
  1994年   12786篇
  1993年   11832篇
  1992年   44578篇
  1991年   43489篇
  1990年   42238篇
  1989年   40135篇
  1988年   36907篇
  1987年   36258篇
  1986年   33629篇
  1985年   32298篇
  1984年   24158篇
  1983年   20285篇
  1982年   11744篇
  1981年   10708篇
  1980年   9538篇
  1979年   21352篇
  1978年   14834篇
  1977年   12548篇
  1976年   11713篇
  1975年   12643篇
  1974年   14669篇
  1973年   14131篇
  1972年   12957篇
  1971年   11735篇
  1970年   11057篇
  1969年   10033篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Gastrin-17 induces hypocalcemia in the rat without stimulating calcitonin release. The gastrin-induced hypocalcemia persisted after thyroparathyroidectomy or parathyroidectomy. In contrast, gastrectomy or extirpation of the acid-producing part of the stomach prevented the hypocalcemic effect, suggesting the involvement of the proximal stomach in the gastrin-evoked lowering of blood calcium. The drop in blood calcium upon injection of gastrin-17 did not reflect a loss of calcium via the gastric juice or via the urine. Extracts of the acid-producing mucosa of the rat stomach had a hypocalcemic effect. The extracts were purified by gel chromatography and reversed-phase high-performance liquid chromatography. Digestion with leucine aminopeptidase destroyed the hypocalcemic activity, while trypsin had no effect, suggesting a peptide (or peptides) with an unprotected NH2 terminus and without basic amino acid residues (or with protected basic amino acids). Both gastrin-17 and the mucosal extract stimulated the uptake of 45Ca into bone (radius and sternum). Gastrin-17 was without effect in rats that had undergone gastrectomy, while the mucosal extract was equally effective in gastrectomized and unoperated rats. We suggest that the effects of gastrin-17 on blood calcium and on calcium transfer into bone are indirect and that gastrin-17 stimulates the release of a peptide hormone, tentatively named gastrocalcin, from the acid-producing mucosa of the stomach. Gastrocalcin stimulates the uptake of 45Ca into bone, thereby causing hypocalcemia.  相似文献   
992.
Three different sensory loss tests, for anaesthesia to light touch, for diminished pain sensation and for loss of thermosensation, were compared with histopathological examination results in the diagnosis of suspected tuberculoid leprosy in 120 individuals with 126 lesions. Though none of the 3 tests used in this study was found to be strikingly superior to any of the others, the results indicate potentially important differences in their usefulness in different subgroups of suspected patients. The methodological problems inherent in such studies are discussed.  相似文献   
993.
Glucocorticoid effects on kainic acid-induced motor seizures and wet dog shakes in rats were investigated by adrenalectomy and dexamethasone treatment. One-day adrenalectomy attenuated kainic acid-induced wet dog shakes and seizure activity. These effects were restored by dexamethasone. Administration of dexamethasone to non-adrenalectomized rats potentiated kainic acid-induced wet dog shakes and severity of seizure activity. These results suggest that glucocorticoids may play an important role in modulating the severity of kainic acid-induced seizures and wet dog shakes.  相似文献   
994.
Quantitative autoradiographic analysis was used to identify regions in the brain of the male primate where androgen binding sites may be involved in the actions of testosterone. Three days after castration, adult male rhesus monkeys received a subcutaneous injection of either dihydrotestosterone propionate (DHTP, 20 mg, n = 6), testosterone propionate (TP, 100 mg, n = 2), or oil vehicle (control males, n = 4). Three hours later, 5 mCi [3H]testosterone was administered as an i.v. bolus. At 60 min, brains were rapidly removed and the left halves were used for autoradiography. In control males, highest percentages of labeled neurons (20-84% using a rigorous Poisson criterion) were observed in the ventromedial, arcuate and premammillary nuclei (n.) of the hypothalamus, medial preoptic n., bed n. of stria terminalis, intercalated mammillary n., lateral septal n. and the medial, cortical and accessory basal n. of the amygdala. Pretreatment with DHTP eliminated labeling in androgen target tissues of the genital tract, and reduced the percentages of labeled neurons to 4-22% of control values in the arcuate, lateral septal, premammillary and intercalated mammillary n., indicating that in these regions testosterone acted predominantly at androgen binding sites. However, in the medial preoptic n., the ventromedial hypothalamic n. and the accessory basal amygdaloid n., DHTP pretreatment resulted in much less blocking which, together with other data, suggested that in these sites, testosterone's actions involved aromatization and interaction with estrogen-binding sites.  相似文献   
995.
Modern identification of Neisseria gonorrhoeae may be either accomplished by direct detection of gonococcal antigen, i.e. without microbiological culturing, or, following culturing, by rapid culture confirmation. The direct detection of gonococcal antigen in an enzyme immuno-assay (Gonozyme) shows reduced specifity especially with mixed microbial flora, and decreased sensitivity with small numbers of organisms. Culture confirmation may be achieved by a rapid sugar degradation test (API----quadFERM+), by specific enzyme detection using chromogenic substrates (Gonochek II), or by demonstration of protein I specific for Neisseria gonorrhoeae by means of monoclonal antibodies (Mikrotrak, Phadebact monoclonal GC, Gonogen II). Detection of protein I is highly sensitive and specific in both the tests of immunofluorescence and coagglutination.  相似文献   
996.
Endoscopic pictures of the bronchi were studied in 509 new cases of pulmonary tuberculosis. Tuberculosis of the bronchi and its aftereffects such as cicatricial lesions were detected in 31.1 per cent of the children and adolescents, 7.9 per cent of the adults at the age of 18 to 29 years, 9.0 per cent of the adults at the age of 30 to 55 years and 14.7 per cent of the adults at the age of 56 to 75 years. Nonspecific endobronchitis was diagnosed in 27.9 per cent of the children and adolescents, 44.9 per cent of the adults at the age of 18 to 29 years, 46.3 per cent at the age of 30 to 55 years and 44.1 per cent at the age of 56 to 75 years. The incidence and nature of tuberculosis of the bronchi and nonspecific endobronchitis were not related to the patients' age.  相似文献   
997.
We tested the efficacy of a thin flexible testosterone-impregnated membrane applied to the scrotum for the long term treatment of male hypogonadism. Ten men with primary hypogonadism were treated for 3 months (2 men) or 13 months (8 men). Serum testosterone concentrations increased in all 10 men, to within the normal range in 8. Serum dihydrotestosterone concentrations increased to supranormal values in all of the men, decreased to the normal range in 6, indicating the biological effectiveness of the testosterone in those subjects. Two men whose serum LH concentrations did not fall to normal had small or distorted scrotal surfaces. Seven of the 8 men whose serum testosterone concentrations became normal said that their hypogonadal symptoms were corrected by this treatment. We conclude that the transdermal administration of testosterone is an effective means of treating the majority of hypogonadal men who have a normal scrotum.  相似文献   
998.
This study examined longitudinal health and intelligence data to determine whether sensory or motor deficits account for some of the age-related intellectual changes that are commonly seen from midlife onward. Although sensory and motor functioning did not account for the age-related decrements in performance on speeded, visual perceptual tasks found for this sample in previous work, we did find that hearing deficits added error variance to performance estimates on two verbal subtests of the Wechsler scales.  相似文献   
999.
1000.
This study examined selective reminding and recognition memory performance of 21 severe closed-head injured patients tested within 6 months of regaining consciousness and then again after at least 1 year. Performances on selective reminding parameters were highly correlated and patients performed significantly worse at both testings than did hospitalized controls matched for age, education, and sex. Patients improved from testing 1 to testing 2 on only four of six memory variables. Average Impairment Rating at testing 1 was a marginally better predictor of memory performance at testing 2 than was length of coma. Results are discussed in terms of (a) utility of selective reminding parameters and predictors of outcome and (b) dissociations in recovery of memory parameters.  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