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   7810篇
  免费   409篇
  国内免费   29篇
耳鼻咽喉   33篇
儿科学   134篇
妇产科学   74篇
基础医学   973篇
口腔科学   221篇
临床医学   485篇
内科学   2234篇
皮肤病学   60篇
神经病学   533篇
特种医学   312篇
外科学   1488篇
综合类   21篇
预防医学   166篇
眼科学   106篇
药学   548篇
中国医学   9篇
肿瘤学   851篇
  2023年   35篇
  2022年   78篇
  2021年   138篇
  2020年   87篇
  2019年   124篇
  2018年   150篇
  2017年   108篇
  2016年   142篇
  2015年   170篇
  2014年   210篇
  2013年   277篇
  2012年   356篇
  2011年   408篇
  2010年   247篇
  2009年   180篇
  2008年   408篇
  2007年   415篇
  2006年   429篇
  2005年   456篇
  2004年   440篇
  2003年   438篇
  2002年   452篇
  2001年   198篇
  2000年   205篇
  1999年   253篇
  1998年   132篇
  1997年   105篇
  1996年   134篇
  1995年   90篇
  1994年   101篇
  1993年   75篇
  1992年   169篇
  1991年   161篇
  1990年   140篇
  1989年   125篇
  1988年   141篇
  1987年   85篇
  1986年   81篇
  1985年   76篇
  1984年   66篇
  1983年   33篇
  1982年   17篇
  1981年   15篇
  1980年   10篇
  1979年   29篇
  1978年   12篇
  1977年   16篇
  1976年   4篇
  1975年   6篇
  1974年   3篇
排序方式: 共有8248条查询结果,搜索用时 31 毫秒
1.
2.
A 50-year-old Japanese man had a blue-black patch on the dorsum of his right wrist. Light and electron microscopic study of the lesion revealed dermal melanocytes containing mature melanosomes, predominantly in the upper dermis. This case was diagnosed as acquired dermal melanocytosis confined to the right wrist.  相似文献   
3.
PURPOSE: The purpose of this study was to examine changes of chewing movement and masticatory efficiency during the natural course of nonreducing disc displacement of the temporomandibular joint (TMJ). PATIENTS AND METHODS: The subjects were 15 patients who had been diagnosed with nonreducing disc displacement of the TMJ but had received no treatment. Chewing movement and masticatory efficiency were examined at the initial visit and at a mean follow-up of 21.7 months, using mandibular kinesiography and adenosine triphosphate ebteric-coated granules. As a control, 23 persons who had no current or previous TMJ symptoms were studied. RESULTS: The patients' clinical signs and symptoms tended to be alleviated during the follow-up period. In normal controls, chewing movement showed lateral excursion to the chewing side on both the right and left sides. In patients, chewing movement at the initial visit showed lateral excursion to the chewing side during chewing on the TMJ affected side, but no such deviation was noted during chewing on the TMJ unaffected side in the horizontal plane. However, chewing movement at follow-up became similar to that of controls. In patients, masticatory efficiency became better during the natural course, although that at follow-up did not always reach the control's level. CONCLUSION: In untreated patients with nonreducing disc displacement of the TMJ, chewing movement and masticatory efficiency tend to improve spontaneously.  相似文献   
4.
The pharmacokinetics of 1-(tetrahydro-2-furanyl)-5-fluorouracil (FT) and its conversion into 5-fluorouracil (FUra) in liver tissue were studied in ten patients with hepatocellular carcinoma (HCC). The plasma concentration of FT after its intravenous injection (dosage: 800 mg) was computerfitted to a bi-exponential function (C = Ae-alpha t + Be-beta t), indicating a two-compartment disposition. The pharmacokinetic parameters did not significantly differ between the five patients with, and the five without cirrhosis of the liver. The plasma concentrations of FUra likewise showed no significant difference between the two groups. The rates of FT degradation in the liver tissue homogenate were similar for four of the patients with cirrhosis (0.10 +/- 0.05 mumol/g liver protein/30 min) and four of those without it (0.13 +/- 0.05). The rates of cytochrome P-450-dependent FUra formation in the microsomal fraction of liver tissue from two patients (1.1 and 1.3 nmol/mg microsomal protein/30 min) were dramatically reduced to less than half of those of two control subjects (2.4 and 2.7). The estimated rates of FUra formation in the soluble fraction (105,000 X g supernatant fraction) from the two patients (0.1 and 0.13 nmol/mg protein/30 min) were almost identical to those from the controls (0.12 and 0.14), suggesting that the rate in the soluble fraction from HCC patients may not be as strongly affected as the rate in the microsomal fraction.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
5.
BACKGROUND: Although it is clear that dissemination via the blood system involves angiogenesis, it is uncertain whether tumors also induce lymphangiogenesis or simply invade existing peritumoral vessels. The purpose of this study was to elucidate changes in tumor blood and lymph vessels in cases involving the invasion of squamous cell carcinoma in the oral cavity, and its significance. Blood and lymph vessels densities in tongue carcinomas induced in hamsters were investigated. METHODS: Tongue cancer was induced by abrading the right margin of the tongue of each hamster with an endodontic barbed broach and subsequently applying 1.0% 9,10-dimenthl-1,2-benzanthracene (DMBA) dissolved in acetone, three times a week, at the same site. Fresh frozen sections were prepared and blood vessels stained blue by perfusion with Coomassie Brilliant Blue and lymph vessels stained brown for 5'-nucleotidase. The effects on the blood vessels and lymph vessels were observed. RESULTS: The results showed that blood and lymph vessel densities were greater in the advanced carcinoma tissues than in normal tissue. These were compared in terms of the mode of cancer invasion. As tumor invasion progressed, the blood vessel density decreased but lymph vessel density tended to be higher in high-degree tumor invasion than in low-degree tumor invasion. The expression of vascular endothelial growth factor-C was seen more frequently as tumor invasion progressed. CONCLUSIONS: The present findings indicated that angiogenesis and lymphangiogenesis are affected by cancerous invasion.  相似文献   
6.
Somatosensory vertex potentials (SVPs) were examined in 12 healthy subjects in response to painful electrical stimulation of the finger. SVPs consisted of N1, P1, and N2. The average latencies of the 3 peaks were 150, 225, and 350 msec, respectively. The latency and amplitude of each potential were reproducible for each subject. Recovery functions of the SVPs were analyzed in 10 subjects. A pair of stimuli were delivered to the right or left finger with interstimulus intervals (ISIs) of 50, 100, 150, 200, 350, 500 and 650 msec. SVPs partially recovered with the shortest ISI (50 msec). Full recovery could not be obtained even with the longest ISI (650 msec). Differences in recoveries within 650 msec of ISI were not observed between right and left stimulations. To examine the interaction between SVPs evoked by right and left finger stimulation, recovery functions from prior contralateral finger stimulation were analyzed with the same ISIs. SVP recoveries for right after left or left after right patterns of stimulus delivery were nearly the same as those for ipsilateral ones. It is suggested that SVPs are generated at nearly the same site in the sensory pathway regardless of the side stimulated.  相似文献   
7.
The relationship between indigenous bacterial floras in the lower genitals and the uterocervical region is of importance due to a barrier-like role against ascending infections through the mechanism of the localized protection at a boundary of the uterocervical region. Therefore, bacterial flora in the uterocervical and uterine regions was studied in cases for which gynecological operations were performed (n = 77). 1. Ratios of incidences of the detection of bacteria on the uterocervical and in the uterine regions were 50/77 (64.9%) and 6/77 (7.8%), respectively. When different age groups are compared, the detection ratio from the uterocervical region was high among patients in the 40 s, and all the cases in which bacteria were detected from the uterine region were in the 40 s. 2. Gram-positive bacteria were detected at a high ratio, and anaerobic bacteria were noted in the uterocervical region, and ratios of detection of Staphylococcus epidermidis, Lactobacillus sp. and Propionibacterium acnes were high. Six strains of Gram-positive bacteria and 1 strain of Candida sp. were noted in the uterine region. 3. When cefmetazole (CMZ) was administered for the prevention of the infections after these panhysterectomy cases examined here, no postoperative infectious diseases nor adverse reactions were noted.  相似文献   
8.
9.
Of 200 lung cancer lesions resected in our hospital, there were 15 cases (7.5%) with middle lobe origin. The histological types were adenocarcinoma in 13 patients (4 patients with alveolar cell carcinoma), squamous cell carcinoma in one and large cell carcinoma in one. These patients were classified into two groups according to the type of operation they received and each group was evaluated. Group I (resection of the middle lobe) included 8 patients. Each one of Stage IIIB and Stage IV received the operation to improve their symptoms. The six patients of Stage I received only middle lobectomy as absolute curable cases. Group II (resection of the middle and lower lobes) included 7 patients, who had preoperative diagnosis of stage III. Two of them were postoperatively found to be cases of Stage I and Stage II. Although it was still short-term, the follow-up evaluation proved that these patients survived without local recurrence and distant metastasis, except for two with pleural dissemination and one with cerebral metastasis, who had received lobectomy as palliative operation. No difference was observed between the two groups receiving different types of operation.  相似文献   
10.
The kapurimycins A1, A2 and A3 were revealed to be new antitumor antibiotics with molecular formula of C27H26O9, C26H24O9 and C27H24O9, respectively. The structures of the kapurimycins were determined by NMR spectroscopic analysis. The kapurimycins are new class of polycyclic microbial metabolites having the tetrahydroanthra-gamma-pyrone skeleton and the beta, gamma-unsaturated delta-keto carboxylic acid structure. The individual components of the kapurimycins differ from one another in the side chain at the pyrone ring of the molecule.  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