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   11881篇
  免费   612篇
  国内免费   53篇
耳鼻咽喉   66篇
儿科学   425篇
妇产科学   289篇
基础医学   1805篇
口腔科学   354篇
临床医学   1017篇
内科学   2258篇
皮肤病学   145篇
神经病学   1027篇
特种医学   967篇
外科学   1543篇
综合类   46篇
一般理论   3篇
预防医学   564篇
眼科学   123篇
药学   897篇
中国医学   26篇
肿瘤学   991篇
  2022年   74篇
  2021年   109篇
  2020年   79篇
  2019年   161篇
  2018年   174篇
  2017年   138篇
  2016年   173篇
  2015年   237篇
  2014年   325篇
  2013年   490篇
  2012年   671篇
  2011年   726篇
  2010年   415篇
  2009年   423篇
  2008年   607篇
  2007年   712篇
  2006年   674篇
  2005年   704篇
  2004年   657篇
  2003年   652篇
  2002年   707篇
  2001年   211篇
  2000年   192篇
  1999年   225篇
  1998年   190篇
  1997年   197篇
  1996年   148篇
  1995年   114篇
  1994年   118篇
  1993年   104篇
  1992年   141篇
  1991年   110篇
  1990年   125篇
  1989年   127篇
  1988年   97篇
  1987年   80篇
  1986年   89篇
  1985年   96篇
  1984年   85篇
  1983年   76篇
  1982年   67篇
  1981年   79篇
  1980年   69篇
  1979年   59篇
  1978年   59篇
  1977年   52篇
  1976年   49篇
  1975年   71篇
  1974年   45篇
  1972年   45篇
排序方式: 共有10000条查询结果,搜索用时 43 毫秒
1.
Abstract The aim of the present clinical trial was to test tolerability during 2 treatments with EMDOGAIN® in a large number of patients. An open, controlled study design in 10 Swedish specialist clinics was chosen, with a test group of 107 patients treated with EMDOGAIN® in connection with periodontal surgery at 2 surgical test sites per patient. The procedures were performed 2 to 6 weeks apart on one-rooted teeth with at least 4 mm deep intraosseous lesions. A control group of 33 patients underwent flap surgery without EMDOGAIN® at I comparable site. In total 214 test and 33 control surgeries were performed. Serum samples were obtained from test patients for analysis of total and specific antibody levels. 10 of the patients had samples taken before and after the first surgery. 56 other samples were taken after one treatment with EMDOGAIN®, and 63 after 2 treatments. None of the samples, not even from allergy-prone patients after 2 treatments, indicated deviations from established baseline ranges. This indicates that the immunogenic potential of EMDOGAIN® is extremely low when applied in conjunction with periodontal surgery. Comparison between the test and control groups demonstrated the same type and frequency of post-surgical experiences, i.e., reactions caused by the surgical procedure itself. Clinical probing and radiographic evaluation was performed at baseline and 8 months postsurgery. About half of the patients (44 test and 21 control) were also evaluated after 3 years. There was a significant difference between the test and control results at 8 months post surgery. and this difference had increased further at the 3 year follow-up. The 2.5–3 mm increase in attachment and bone level after treatment with EMDOGAIN® was of the same magnitude as seen in the studies with split-mouth design aiming for lest of effectiveness of EMDOGAIN®.  相似文献   
2.
Eleven patients with refractory rheumatoid arthritis were submitted to a total lymphoid irradiation up to a dose of 20 Gy. A constant improvement of clinical symptoms was observed in four out of the eleven patients already during the treatment and in the other patients not later than two months after. The frequency of attacks decreased and the number of joints involved in the attack was reduced. Morning rigidity and joint swellings decreased. One patient developed joint empyemas 4 and 26 months after the treatment. Four patients died in the meantime. In two patients the cause of death were renal insufficiency and a postoperative cardiogenic shock associated with generalized amyloidosis. The third patient died because of a toxically induced left cardiac decompensation with sepsis that could not be controlled by antibiotic drugs and multiple joint empyemas. The fourth patient developed an abscess after surgical treatment of a Kaposi syndrome. She died three months later from acute left cardiac decompensation. The therapy induced a lymphocytopenia with decrease of T helper lymphocytes and unchanged number of T suppressor lymphocytes. The constant therapy results of total lymphoid irradiation in primary chronic polyarthritis is probably due to this modification in the immune regulation.  相似文献   
3.
BACKGROUND: Low molecular weight heparins (LMWH) like dalteparin are increasingly used for anticoagulation during haemodialysis (HD). The available laboratory tests for monitoring LMWH anticoagulation are time-consuming and expensive, and the suitability of the conventional activated clotting time (ACT) is controversial. A simple and cheap bedside test would be useful. METHODS: We studied the factor Xa-activated whole blood clotting time (Xa-ACT) in vitro and in vivo in nine patients undergoing chronic HD with i.v. dalteparin bolus anticoagulation and compared it with the conventional ACT. Plasma anti-factor Xa (antiXa) activity was determined with a chromogenic assay. Thrombin-antithrombin complexes were measured to detect coagulation activation. RESULTS: Xa-ACT and ACT were prolonged with rising dalteparin concentration. In vitro, both clotting times were strongly correlated with the antiXa levels (r = 0.94 and 0.89, respectively). Nevertheless, compared with the ACT, the Xa-ACT was considerably more sensitive to the LMWH in vitro (healthy blood: Xa-ACT 90 s/U vs ACT 26 s/U; uraemic blood: Xa-ACT 96 s/U vs ACT 31 s/U) as well as in vivo (Xa-ACT 81 s/U vs ACT 22 s/U) and reflected different intensities of anticoagulation. An initial dalteparin bolus of 80+/-11 U/kg body weight was able to prevent coagulation activation for up to 4 h of HD. CONCLUSION: For monitoring LMWH anticoagulation the Xa-ACT was superior to the conventional ACT in vitro as well as in vivo during HD. The Xa-ACT can be useful as a LMWH bedside test. The ACT was not sensitive enough to serve as a LMWH monitoring tool.  相似文献   
4.
In search of potential drugs for the treatment of estrogen- and androgen-dependent cancer as well as the prophylaxis of metastases, tetralones, tetralins, and dihydronaphthalenes bearing a OCH3 substituent at the benzene nucleus and an imidazol-4-yl, imidazol-1-yl, or 1,2,4-triazol-1-yl substituent in 2-position were synthesized with and without C1-spacer between the rings (compounds 2 – 26 ). The compounds were tested in vitro for inhibition of the three target enzymes P450 arom (human placental microsomes), P450 17 (rat testicular microsomes), and P450 TxA2 (citrated human whole blood). To examine selectivity, some compounds were further tested in vitro for inhibition of P450 18 (bovine adrenal mitochondria), P450 see (bovine adrenal mitochondria) and corticoid formation (aldosterone, corticosterone; ACTH stimulated rat adrenal tissue). In vivo, selected compounds were examined in Sprague Dawley rats regarding P450 TxA2 inhibition, reduction of plasma testosterone concentration, antiuterotrophic activity (inhibition of the uterotrophic activity of androstenedione), reduction of plasma estradiol concentration (pregnant mares' serum gonadotropin-primed rats), and mammary tumor inhibiting activity (dimethylbenzanthracene-induced tumor; pre- and postmenopausal model). In the series of imidazol-4-yl compounds, which represent a novelty in the field of azole inhibitors of steroidogenic P450 enzymes, strong inhibitors of P450 arom and/or P450 17 were found: 7-OCH3-2-(imidazol-4-ylmethylene)-1-tetralone ( 4 ) and 7-OCH3-2-(imidazol-4-ylmethyl)-tetralin ( 12 ) are among the most potent inhibitors of P450 arom in vitro known so far. Compound 4 is a selective inhibitor, whereas 12 shows in addition strong inhibition of P450 17. In contrast to 12 , the 6-OCH3 derivative (compound 11 ) is a selective inhibitor of P450 17, being 50 times more potent than ketoconazole. Some imidazol-1-yl compounds show a marked inhibition of P450 TxA2: 2-(imidazol-1-ylmethyl)-1-tetralone ( 13 ) is a selective inhibitor of P450 TxA2, whereas 7-OCH3-2-(imidazol-1-ylmethyl)-tetralin ( 17 ) as well as 2-(imidazol-1-ylmethyl)-tetralin ( 16 ) and 7-OCH3-2-imidazol-1-yl-3,4-dihydronaphthalene ( 25 ) additionally show strong inhibition of P450 arom and P450 17. Regarding the other steroidogenic P450 enzymes as well as corticosterone formation, the compounds show only little inhibitory activity. Aldosterone formation, however, is inhibited at low concentrations. Nevertheless, 4 and 12 are more selective, i.e. inhibit aldosterone synthesis less than the well known inhibitor of P450 arom fadrozole. The compounds show activity in the aforementioned in vivo tests.  相似文献   
5.
6.
An efficient shim system and an optimized localization sequence were used to measure in vivo 1H NMR spectra from cerebral cortex, hippocampus, striatum, and cerebellum of C57BL/6 mice at 9.4 T. The combination of automatic first- and second-order shimming (FASTMAP) with strong custom-designed second-order shim coils (shim strength up to 0.04 mT/cm2) was crucial to achieve high spectral resolution (water line width of 11-14 Hz). Requirements for second-order shim strengths to compensate field inhomogeneities in the mouse brain at 9.4 T were assessed. The achieved spectral quality (resolution, S/N, water suppression, localization performance) allowed reliable quantification of 16 brain metabolites (LCModel analysis) from 5-10-microL brain volumes. Significant regional differences (up to 2-fold, P < 0.05) were found for all quantified metabolites but Asp, Glc, and Gln. In contrast, 1H NMR spectra measured from the striatum of C57BL/6, CBA, and CBA/BL6 mice revealed only small (<13%, P < 0.05) interstrain differences in Gln, Glu, Ins, Lac, NAAG, and PE. It is concluded that 1H NMR spectroscopy at 9.4 T can provide precise biochemical information from distinct regions of the mouse brain noninvasively that can be used for monitoring of disease progression and treatment as well as phenotyping in transgenic mice models.  相似文献   
7.
8.
Copolymerization of propene with 1-octene (1 mol/1 mol) was performed in toluene at 40°C in the presence of homogeneous methylaluminoxane (MAO)-activated ansa-metallocenes in order to study the role of benzannelation and 2-methyl-substitution of the silylene-bridged bisindenyl ligand on comonomer incoporation, molecular mass, molecular mass distribution, and end groups. While 2-methyl-substitution promoted higher degree of polymerization without affecting copolymerization parameters, benzannelation improved markedly 1-octene incorporation. Only with MAO-activated rac-Me2Si(2-MeBenz[e]Ind)2ZrCl2 catalysts vinylidene end groups were formed exclusively. Molecular weight distribution remains narrow in all experiments.  相似文献   
9.
The present study was conducted on 33 children (median age at initial cardiac catheterization 0.4 years [0.1 to 11.8]) with anomalous origin of the left coronary artery from the pulmonary artery, without associated hemodynamically significant cardiovascular anomalies, who were treated throughout a period of 18 years in our hospital. A two coronary artery circulation was reestablished in 31 of 33 children. One child died before the intended operation, and in one child the left coronary artery was ligated. There were six operative deaths, five intraoperative and one 12 hours after operation. The purpose of the study was to assess which preoperative clinical and angiographic features were associated with a higher perioperative mortality. The following preoperative factors were associated with a statistically significant higher perioperative mortality: young age at operation (p less than 0.03), left and balanced type of coronary circulation (p less than 0.01), and electrocardiographic signs of extensive acute myocardial infarction, namely, marked ST elevation (greater than or equal to 0.2 mV in at least two leads) (p less than 0.03). Left axis deviation on the electrocardiogram was associated with an extreme right dominant type of coronary circulation (p less than 0.005). The latter was also linked with adequate perfusion of the posterolateral left ventricular wall (p less than 0.005). At autopsy, severe increase of heart weight to two or three times the normal heart weight was established in six of seven children. Thus the perioperative mortality was determined primarily by the extent of myocardial ischemia. This in turn is decisively influenced by the dominant type of coronary circulation and the extent of inter-arterial collateralization. Young age, in addition, proved to be a risk factor for mortality at corrective surgery.  相似文献   
10.
STUDY OBJECTIVE: To assess the clinical utility of measuring urinary pregnanediol glucuronide in random samples in an infertility practice. DESIGN: Samples of urine were collected from patients approximately 3 weeks from their last menstrual period to ascertain if ovulation had occurred. Each sample was tested for specific gravity before analyzing for pregnanediol glucuronide. Simultaneous venipuncture was performed to compare results from the urinary assay to quantitative measures of serum progesterone (P). SETTING: All patients were randomly sampled. PATIENTS: Three hundred ninety women undergoing pituitary down regulation with leuprolide acetate were chosen for study because they routinely initiate medication after documentation of ovulation. OUTCOME MEASURES: The performance of the urinary pregnanediol glucuronide was evaluated as to its sensitivity, specificity, predictive value, and test efficiency compared with a serum measurement of 2.5 ng/mL and 10.0 ng/mL. RESULTS: The performance characteristics of the pregnanediol glucuronide assay were directly related to the hydration status of the patient at the time of sample collection. Regardless of urine specific gravity, if pregnanediol glucuronide was qualitatively detected (greater than 3 micrograms/mL), serum P was greater than 2.5 ng/mL. However, in cases in which pregnanediol glucuronide was undetected (less than 3 micrograms/mL), results were only accurate when the specific gravity was greater than or equal to 1.020. When comparing urinary pregnanediol glucuronide values to serum greater than 10 ng/mL, both specificity and predictive value of a positive test decreased because of increased numbers of false-positive results. CONCLUSIONS: The enzyme immunoassay measurement for pregnanediol glucuronide may replace the use of serum P in documenting the ovulatory status of many patients. However, all specimens must be checked for specific gravity and if less than 1.020, a serum P should be used to ensure accuracy.  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