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   144935篇
  免费   9529篇
  国内免费   3424篇
耳鼻咽喉   1724篇
儿科学   3307篇
妇产科学   4482篇
基础医学   21443篇
口腔科学   4068篇
临床医学   12846篇
内科学   25794篇
皮肤病学   2668篇
神经病学   9544篇
特种医学   4912篇
外国民族医学   24篇
外科学   19352篇
综合类   9252篇
现状与发展   5篇
一般理论   35篇
预防医学   10655篇
眼科学   3451篇
药学   12902篇
  23篇
中国医学   2221篇
肿瘤学   9180篇
  2022年   1653篇
  2021年   2496篇
  2020年   1688篇
  2019年   2010篇
  2018年   2602篇
  2017年   2099篇
  2016年   2018篇
  2015年   2689篇
  2014年   3346篇
  2013年   3778篇
  2012年   5480篇
  2011年   5952篇
  2010年   3521篇
  2009年   3015篇
  2008年   4728篇
  2007年   4868篇
  2006年   4864篇
  2005年   4433篇
  2004年   3864篇
  2003年   3480篇
  2002年   3312篇
  2001年   7256篇
  2000年   7481篇
  1999年   6343篇
  1998年   2218篇
  1997年   1771篇
  1996年   1235篇
  1995年   1131篇
  1992年   3929篇
  1991年   3963篇
  1990年   3690篇
  1989年   3690篇
  1988年   3545篇
  1987年   3378篇
  1986年   3187篇
  1985年   3046篇
  1984年   2080篇
  1983年   1818篇
  1982年   1000篇
  1979年   1922篇
  1978年   1196篇
  1977年   992篇
  1975年   1196篇
  1974年   1367篇
  1973年   1415篇
  1972年   1360篇
  1971年   1257篇
  1970年   1146篇
  1969年   1125篇
  1968年   1032篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
91.
92.
93.
Changes in semen parameters are presented for 4708 patients treated for infertility. The largest group comprised patients with oligoasthenozoospermia of various grades (57.7%). Improvement in the seminal state was noted in 70.3%. The percentage of achieved normospermia increased proportionally to the initial semen state. Pregnancy rate also increased proportionally to the initial seminal state. Among the patients' wives 20.4% conceived: 28.2% of these pregnancies had occurred after having achieved normospermia, while in 71.8% the seminal states were still below the accepted normal values.  相似文献   
94.
We report a series of 33 consecutive hospitalized geriatric diabetic patients who were referred for evaluation of diabetic nephropathy, defined as proteinuria greater than or equal to 1 g/d (1,000 mg/24 h) or a serum creatinine concentration greater than or equal to 177 mumol/d (greater than or equal to 2 mg/dL). The study population was 60 years old or older (mean age, 68 +/- 6 years), was comprised mainly of women (24 of 33, 72.7%), and was predominantly black (25 of 33, 75.8%). All patients had type II diabetes. A family history of diabetes in parent or sibling was elicited in 24 (72.7%) patients. There were eight patients undergoing maintenance hemodialysis and 25 with less severe nephropathy (mean proteinuria, 2.7 g/d [2,700 mg/24 h]; mean creatinine clearance, 0.57 mL-s [34 mL/min]). Cardiac disorders were noted in the majority of patients: congestive failure in 20 (60.6%), myocardial infarction in eight (24.2%), and active angina in five (15.2%). Other comorbid diseases were present in both hemodialysis patients and the subset of nondialyzed azotemic-proteinuric patients, and consisted of peripheral neuropathy in 31 (93.9%), gastroparesis in 16 (48.5%), retinopathy in 28 (84.8%), and legal blindness in 11 (33%). We conclude that geriatric diabetic nephropathy in type II diabetes is similar in presentation and severity of comorbid extrarenal complications to the syndrome described in younger adults. This inference must be tempered by both the small size and the limitation imposed by the demographics of the study population, which is predominantly composed of black patients receiving treatment at inner city hospitals.  相似文献   
95.
Central administration of bombesin elicits excessive grooming and locomotor activity in rats. This grooming activity is one characterised by vigorous scratching of the face, nape and body flanks. Pretreatment with the D1 receptor antagonist SCH 23390 inhibited the expression of bombesin-induced activity with grooming being more inhibited than locomotion. Blockade of D2 receptors with eticlopride significantly attenuated the behavioral responses to bombesin. When SCH 23390 and eticlopride were administered concurrently, it was apparent that D1 blockade had a greater effect on grooming and D2 blockade a larger effect on locomotion. Stimulation of D1 receptors by SKF 38393 elicited non-stereotyped locomotor activity and a form of grooming behavior characterised by vigorous washing of the face and ventral body surfaces. Co-administration of bombesin and SKF 38393 resulted in a form of grooming which resembled that elicited by SKF 38393 alone. The specific D2 agonist PPHT elicited a form of locomotion characterised by a downward oriented head posture and slow ambulatory activity around the cage perimeter. Co-administration of PPHT and bombesin resulted in a complete suppression of bombesin-induced behaviors and was largely indistinguishable from activity observed under PPHT alone conditions. These data implicate both D1 and D2 receptor based mechanisms in the modulation/mediation of the behavioral effects of bombesin. Part of the bombesin-induced behavioral effects may be explained by (indirect) activation of (a) dopamine system(s).  相似文献   
96.
The content of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and norepinephrine (NE) was analysed in 71 human spinal cords obtained post-mortem. The highest content of 5-HT, 5-HIAA and NE was found in the lumbar enlargement of the spinal cord. 5-HT and 5-HIAA content increased from fetal to adult spinal cord whereas the content of NE decreased. Characteristic segmental distribution of measured monoamines was present in adult spinal cord only. In two patients spinal cord lesion led to the reduction in spinal cord content of 5-HT, 5-HIAA and NE and loss of characteristic segmental distribution of these substances. These results are in general agreement with observations on spinal cord of different animal species.  相似文献   
97.
Gerbils are much more sensitive to the hepatotoxic and lethal effects of CCl4 than rats as indicated by 48-hr LD50 values (0.08 vs 2.8 ml/kg). On the other hand, gerbils are refractory to chlordecone (CD) potentiation of CCl4 toxicity. To investigate the possible mechanism underlying the high sensitivity of gerbils to CCl4 lethality, the metabolism of CCl4 was studied in gerbils pretreated with dietary CD, phenobarbital (PB), or mirex (M) at 10, 225, and 10 ppm, respectively. The hepatic content of 14CCl4, the expiration of 14CCl4 and 14CCl4-derived 14CO2, and lipid peroxidation were measured and the results were compared with the previous data for rats. After the 15-day dietary pretreatment, male gerbils (60-80 g) received 14CCl4 (0.08 ml/kg; sp act 0.04 mCi/mmol) ip in corn oil and the radioactivity present in the expired air was collected for 6 hr. More than 80% of the parent compound as represented by the 14C-label in the toluene trap was expired in 6 hr regardless of the pretreatments. Expiration of 14CO2 measured during the 6 hr after 14CCl4 administration in control gerbils was 3.5-fold more than that in rats and was significantly increased in pretreated groups (M greater than PB greater than CD). PB and M pretreatments resulted in a significant increase of 14C-label bound to the nonlipid fraction of the liver as compared with CD-treated or control gerbils. The radiolabel present in the livers of control gerbils was 5-fold higher than that of rats. In vivo lipid peroxidation measured as diene conjugation in lipid extracts from the livers was lower in gerbils than in rats, and none of the pretreatments significantly affected lipid peroxidation. The serum alanine aminotransferase and aspartate aminotransferase were significantly elevated at 6 hr after CCl4 injection in all groups of gerbils. These data indicate that the more extensive metabolism of CCl4, as represented by 14CO2 formation and 14C-label bound to hepatic tissue, in gerbils as compared with rats, may partially explain the high sensitivity of gerbils to CCl4 toxicity. However, the enhanced metabolism of CCl4 found in CD-, PB-, or M-pretreated gerbils did not lead to amplified hepatotoxic and lethal effects of CCl4. The reason gerbils may be refractory to CD amplification of CCl4 injury might be associated with other factors yet to be investigated.  相似文献   
98.
The Synergist Erection System (SES) was tested over a six-month period in 44 impotent patients with an organic etiology. The device was successfully used by 73 percent. The duration of erection for 75 percent of the patients was as long as they wanted to wear the device. The frequency of use was once a week for 47 percent. The quality of erection was rated satisfactory by 63 percent of the patients and 78 percent of the couples rated satisfactory intercourse. It appears the SES option is a valid one with high success and satisfaction rating at least on a short-term basis. In addition, it offers prophylactic protection.  相似文献   
99.
100.
A patient with primary malignant melanoma localized to the right gluteal region is described. Four years later and alter intercurrent influenza, disseminated metastases of malignant melanoma to the skin occurred. After a further 6 months melanodermia developed and lasted until the death of the patient (6 months later). Autopsy revealed melanosis of the visceral organs. Histology taken from internal organs using S-100 protein and HMB-45 melanoma methods confirmed metastases of malignant melanoma to the skin, oral cavity, palatal tonsils, nasal and nasopharyngeal mucosae, lungs, myocardium and brain. The authors discuss the mechanism of melanosis—a rare sign in patients with metastasizing malignant melanoma.  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