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   29114篇
  免费   1629篇
  国内免费   260篇
耳鼻咽喉   248篇
儿科学   557篇
妇产科学   591篇
基础医学   2974篇
口腔科学   673篇
临床医学   2066篇
内科学   8283篇
皮肤病学   379篇
神经病学   2523篇
特种医学   1086篇
外科学   5463篇
综合类   59篇
一般理论   5篇
预防医学   1147篇
眼科学   537篇
药学   1691篇
中国医学   57篇
肿瘤学   2664篇
  2024年   31篇
  2023年   296篇
  2022年   615篇
  2021年   1049篇
  2020年   588篇
  2019年   857篇
  2018年   1021篇
  2017年   749篇
  2016年   899篇
  2015年   922篇
  2014年   1264篇
  2013年   1538篇
  2012年   2355篇
  2011年   2246篇
  2010年   1283篇
  2009年   1240篇
  2008年   1931篇
  2007年   1869篇
  2006年   1752篇
  2005年   1741篇
  2004年   1634篇
  2003年   1398篇
  2002年   1257篇
  2001年   161篇
  2000年   164篇
  1999年   194篇
  1998年   228篇
  1997年   172篇
  1996年   173篇
  1995年   165篇
  1994年   139篇
  1993年   126篇
  1992年   120篇
  1991年   76篇
  1990年   76篇
  1989年   56篇
  1988年   48篇
  1987年   50篇
  1986年   64篇
  1985年   50篇
  1984年   45篇
  1983年   42篇
  1982年   54篇
  1981年   31篇
  1980年   29篇
  1979年   24篇
  1978年   19篇
  1976年   16篇
  1975年   13篇
  1974年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Objective: To evaluate the effects of a new timing strategy of band adjustment on the short-term outcome of obese women operated with adjustable silicone gastric banding. Subjects: The outcome of 30 women without binge-eating disorder operated with laparoscopic adjustable silicone gastric banding with a wider intraoperatory band calibration (LAP-BAND) was compared to that of 30 body mass index-matched women without binge-eating disorder previously operated with adjustable silicone gastric banding (ASGB) applied by laparotomy with the usual intraoperatory band calibration. The patients were evaluated 3, 6 and 12 months after surgery. Measurements: (1) weight loss; (2) total daily energy intake; (3) percent as liquid, soft or solid food; (4) vomiting frequency; (5) rate of postoperative percutaneous band adjustments; (6) rate of band-related complications. Results: Both the weight loss and the daily energy intake did not differ between patients with LAP-BAND and patients with ASGB. After surgery, the patients with LAP-BAND ate more solid food and less liquid food than the patients with ASGB. Vomiting frequency was higher in patients with ASGB than in patients with LAP-BAND. The total number of percutaneous band adjustments was higher in women with LAP-BAND than in women with ASGB. Band inflation because of weight stabilization was performed in six (20.0%) women with ASGB and in 19 (63.3%) women with LAP-BAND. Neostoma stenosis occurred in one women with ASGB, but in none of the women with LAP-BAND. One patient with LAP-BAND presented band slippage. Conclusions: The wider intraoperatory band calibration performed in patients with LAP-BAND did not reduce the short-term efficacy of adjustable silicone gastric banding. This new timing strategy of band adjustment required more postoperative percutaneous band inflations, but it improved the eating pattern of the patients (low vomiting frequency and high intake of solid food).  相似文献   
22.
The epsilon-sarcoglycan gene (SGCE) on human chromosome 7q21 has been reported to be a major locus for inherited myoclonus-dystonia. Linkage to the SGCE locus has been detected in the majority of families tested, and mutations in the coding region have been found recently in families with autosomal dominant myoclonus-dystonia. To evaluate the relevance of SGCE in myoclonus-dystonia, we sequenced the entire coding region of the epsilon-sarcoglycan gene in 16 patients with either sporadic or familial myoclonus-dystonia. No mutations were found. This study suggests that epsilon-sarcoglycan does not play an important role in sporadic myoclonus-dystonia and supports genetic heterogeneity in familial cases.  相似文献   
23.
The various causative and mechanistic phenomena associated with aneuploidy induction require considerable investigation to better understand the etiology of chromosome missegregation. We investigated the potential of vinblastine sulfate, pyrimethamine, diethylstilbestrol diphosphate, and chloral hydrate to induce numerical and structural chromosome changes in female mouse germ cells. Superovulated ICR mice were administered the compounds either by intraperitoneal injection or oral gavage, and oocytes were collected and processed for cytogenetic analysis 17 hr later. Vinblastine sulfate, administered i.p., induced a significant increase in the frequency of ovulated Ml oocytes and of hyperploid Mll oocytes compared to controls, but did not increase the frequency of structural aberrations. Pyrimethamine, diethylstilbestrol diphosphate, and chloral hydrate did not increase the frequency of numerical or structural chromosome changes in female mouse germ cells. © 1993 Wiley-Liss, Inc.  相似文献   
24.
25.
The aim of the present study was to evaluate the effect of long-term (12 months) administration of raloxifene hydrochloride (60 mg/day) on the steroid production of the adrenal cortex and on the hypothalamic-pituitary-adrenal axis in postmenopausal women. We performed a basal evaluation, a corticotropin releasing factor (CRF) (100 microg i.v. bolus) test and a dexamethasone (DXM) (0.25 mg) suppression-adrenocorticotropic hormone (ACTH) (10 microg i.v. bolus) stimulation test in 11 postmenopausal women, before and after 3, 6 and 12 months of raloxifene treatment. Raloxifene administration significantly modified circulating levels of adrenal steroids, decreasing cortisol (-24%), dehydroepiandrosterone (DHEA) (-36%), and its sulfate (DHEAS) (-41%), and androstenedione (-29%), and increasing circulating allopregnanolone (+39%) levels. Progesterone and 17OH-progesterone levels remained unmodified, while estradiol and estrone levels showed a significant decrease (-51% for estradiol and -61% for estrone). We also observed an increase in circulating ACTH (+58%) and beta-endorphin (+120%). No modifications in the hormonal responses to CRF were observed during the treatment. DXM significantly suppressed circulating steroids at any time with a lower suppression of cortisol from the third month and a higher suppression of DHEA at 12 months. ACTH administration was associated with a significantly blunted cortisol response from the sixth month and a significantly increased response of allopregnanolone from the third month. The present data exclude a raloxifene effect on pituitary sensitivity to CRF and demonstrate a reduced adrenal sensitivity to ACTH, sustained by the opposite changes in basal cortisol and Delta5 androgens, which were reduced, and in ACTH and beta-endorphin, which were increased, as well by the reduced response of cortisol to the direct ACTH stimulus. The reduction of circulating cortisol levels and cortisol response to the ACTH challenge suggests that raloxifene protects against the neurotoxic effects of endogenous glucocorticoids. Furthermore, the progressive increase in basal allopregnanolone and its increased response to ACTH indicate that chronic raloxifene administration exerts direct effects on the pattern of adrenal enzymes, leading to specific changes in the circulating levels of this anxiolytic progesterone metabolite. The important reduction in the circulating levels of estradiol and estrone under long-term raloxifene administration may represent a further mechanism by which this molecule may exert a protective effect against breast and endometrial malignancies.  相似文献   
26.
BACKGROUND: We tested the hypothesis that using a subgluteus approach to the sciatic nerve requires a lower concentration of mepivacaine to obtain complete anesthesia as compared with the popliteal approach. METHODS: With midazolam premedication (0.05 mg kg(-1) iv), 48 patients undergoing hallux valgus repair were randomly allocated to receive a sciatic nerve block using either a posterior popliteal (group Popliteal, n = 24) or subgluteus (group Subgluteus, n = 24) approach with 30 mL of local anesthetic injected after elicitation of plantar flexion of the foot with a current 相似文献   
27.
28.
OBJECTIVE: It is not well established whether the blood flow of arterial composite Y-grafts can efficiently respond to the flow demand of the coronary system early postoperatively. The aim of this study was to evaluate if soon after the operation, arterial composite Y-grafts can increase blood flow in response to an increase in myocardial oxygen consumption (MVO2). METHODS: Twenty-seven patients who received complete arterial myocardial revascularization using the left internal thoracic artery (LITA) and the radial artery (RA) as composite Y-graft gave their consent to a pre-discharge coronary angiography and intravascular flow velocity measurements using a Doppler guide wire. Flow measurements were performed in the LITA main stem, the distal LITA and the RA, both at rest and during atrial pacing at the 85% of the patient age-predicted maximum. The heart rate-systolic blood pressure product was considered as an indirect index of MVO2. Hyperemic flow was determined after injection of adenosine. The flow reserve (FR) was defined as the ratio of blood flow during maximal hyperemia (Qmax) to baseline flow (Qbasal). RESULTS: Atrial pacing increased MVO2 significantly (P<0.000). None of the patients developed ischemic S-T segment modifications or complained of chest pain. Q(basal) increased significantly in the LITA main stem (P=0.001), distal LITA (P=0.041) and RA (P=0.004) while Qmax did not change significantly. As a consequence, the FR decreased in the LITA main stem (P=0.002), distal LITA (P<0.000) and RA (P<0.000) but was not completely exhausted. CONCLUSIONS: Soon after the operation, arterial composite Y-grafts can significantly increase blood flow in response to conditions of increased MVO2, keeping normal the myocardial O2 supply-to-demand ratio.  相似文献   
29.
Cancer cells elaborate metalloproteinases which may play a role in invasion and metastasis. The serum level of the M(r) 72,000 type IV collagenase (MMP-2) was measured in 87 lung cancer patients. Stage IV cancer levels were significantly elevated (P less than 0.0001) compared to normal sera. A significant difference (P less than 0.01) was found between enzyme levels in the presence versus the absence of distant metastasis. For 29 patients treated with combination chemotherapy, a positive relationship was noted between response failure and elevated enzyme levels. Serum metalloproteinase levels may provide information relevant to prognosis as well as treatment decisions.  相似文献   
30.
BACKGROUND: Sodium removal (NaR) may have a major impact on the survival of peritoneal dialysis patients. The dialysate/plasma sodium concentration ratio (D/P(Na)) is an indirect index of transcellular water transport by aquaporin channels, and thus of ultrafiltration. Sodium concentration can be assessed by means of flame photometry (F), and direct (D-ISE) or indirect ion-selective electrodes (I-ISE), but these methods have different properties. I-ISE is being used increasingly in clinical laboratories. The aim of this study was to evaluate NaR and D/P(Na) using the three different measurement methods. METHODS: We performed peritoneal equilibration tests (PETs) in 44 peritoneal dialysis patients and calculated the NaR. We also calculated D/P(Na) during the test; plasma and dialysate sodium concentrations were measured by F, D-ISE and I-ISE. RESULTS: NaR was lower (P<0.001) with D-ISE (69+/-29 mmol) than with F (81+/-29 mmol) or I-ISE (79+/-28 mmol). D/P(Na) was also lower at baseline (0.92+/-0.02 vs 0.95+/-0.02 and 0.95+/-0.02; P<0.001), after 60 min (0.87+/-0.03 vs 0.90+/-0.03 and 0.90+/-0.03; P<0.001) and at the end of PET (0.88+/-0.04 vs 0.92+/-0.04 and 0.92+/-0.04; P<0.001) when measured by D-ISE in comparison with F and I-ISE, respectively. CONCLUSIONS: NaR and D/P(Na) were lower when measured by the D-ISE method compared with the F and I-ISE methods. NaR and D/P(Na) were similar when measured by F or I-ISE. I-ISE can be used reliably in the evaluation of NaR and D/P(Na) in everyday clinical practice of peritoneal dialysis.  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