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   216281篇
  免费   3898篇
  国内免费   163篇
耳鼻咽喉   1623篇
儿科学   8002篇
妇产科学   3605篇
基础医学   21356篇
口腔科学   2136篇
临床医学   16580篇
内科学   40093篇
皮肤病学   1355篇
神经病学   20440篇
特种医学   10513篇
外科学   35790篇
综合类   2681篇
一般理论   82篇
预防医学   21122篇
眼科学   3867篇
药学   11551篇
中国医学   663篇
肿瘤学   18883篇
  2023年   408篇
  2022年   693篇
  2021年   1594篇
  2020年   796篇
  2019年   1334篇
  2018年   23295篇
  2017年   18286篇
  2016年   20501篇
  2015年   2161篇
  2014年   2539篇
  2013年   2841篇
  2012年   10388篇
  2011年   24334篇
  2010年   20573篇
  2009年   13134篇
  2008年   22167篇
  2007年   24292篇
  2006年   3168篇
  2005年   4624篇
  2004年   5782篇
  2003年   6342篇
  2002年   4341篇
  2001年   537篇
  2000年   627篇
  1999年   434篇
  1998年   556篇
  1997年   524篇
  1996年   327篇
  1995年   334篇
  1994年   264篇
  1993年   226篇
  1992年   201篇
  1991年   241篇
  1990年   245篇
  1989年   180篇
  1988年   133篇
  1987年   145篇
  1986年   120篇
  1985年   121篇
  1984年   115篇
  1983年   124篇
  1982年   140篇
  1981年   85篇
  1980年   109篇
  1979年   58篇
  1978年   57篇
  1977年   57篇
  1974年   63篇
  1938年   60篇
  1932年   56篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.

Purpose

Post-dural puncture headache (PDPH) is a well-known neurological outcome caused by leakage of cerebrospinal fluid during neuraxial anesthesia. Studies aimed at assessing the efficacy of finer gauged spinal needles to reduce the incidence of PDPH have produced conflicting results. We have therefore examined the effect of the gauge of cutting needles and pencil-point needles, separately, on the incidence of PDPH.

Methods

The PubMed, EMBASE and Google Scholar databases were searched for randomized studies which compared PDPH incidence in a head-to-head analysis of individual needle gauges of similar needle designs (cutting and pencil-point). A meta-regression analysis was performed taking into account various covariates, such as needle gauge and design, mean age of patient population, surgery type, percentage of males and females in study population and year of publication.

Results

Of the 22 studies (n = 5631) included in the analysis, 12 (n = 3148) and ten (n = 2483) compared different gauges of cutting needles and pencil-point needles, respectively. After adjusting for covariates, meta-regression analysis was performed for all studies that randomly compared individual needle gauges of similar needle design. Whereas the incidence of PDPH inversely correlated with gauge in cutting needles (β = ?1.36 % per gauge, P = 0.037), no relationship was noted in pencil-point needles (β = ?0.32 % per gauge, P = 0.114). Female gender was the only covariate that reached a statistically significant correlation with the incidence of PDPH in both models.

Conclusions

A significant relationship between needle gauge and subsequent rate of PDPH was noted in cutting needles, but not pencil-point needles.
  相似文献   
992.

Purpose

Anatomic variations complicate surface landmark-guided needle placement, thereby increasing nerve blockade failure rate. However, little is understood about how anatomic distances change under different clinical conditions. As the cricoid cartilage is an easy and accurate landmark, we investigated changes in distance between the sixth or seventh cervical transverse processes (C6TP or C7TP) and the cricoid cartilage in neutral and extended supine positions.

Methods

Forty-two patients (16 men, 26 women) were included in this study. Distances between the cricoid cartilage and C6TP/C7TP were measured using ultrasonography with the patient in neutral and extended supine positions.

Results

C6TP and C7TP were caudally located at 6.0 ± 8.1 and 15.1 ± 7.2 mm, respectively, from the cricoid cartilage in the neutral supine position, and at 15.2 ± 8.0 and 25.3 ± 8.0 mm, respectively, in the extended supine position. In the extended supine position, the cricoid cartilage was more cephalad than C6TP and C7TP in all patients. The distance from the cricoid cartilage to C6TP was 12.1 ± 7.6 mm in men and 17.2 ± 7.7 mm in women.

Conclusion

C6TP and C7TP are located approximately 15 and 25 mm, respectively, caudal to the cricoid cartilage in the extended supine position. Our results highlight the fact that there can be significant anatomic variation between the extended and neutral supine positions used in stellate ganglion block, which should be kept in mind when devising easily identifiable and palpable surface landmarks.
  相似文献   
993.

Purpose

The present report intended to introduce the hemilaminoplasty technique and evaluate the efficacy of our surgical procedure for LISCs.

Methods

This retrospective study was conducted to analyze the results in 24 LISCs who had undergone our hemilaminoplasty between 2000 and 2012 in two hospitals. All were confirmed by pathological histology and mid- to long-term follow-up had been performed in all cases with a mean of 4.9 years. Using the Japanese Orthopedic Association scoring system (JOA score) and visual analog scale (VAS), symptoms resulting from cyst compression were quantified at various stage for statistical analysis.

Results

The JOA score and VAS of back/leg pain following surgery were improved significantly (P < 0.01). At final follow-up, with normal aging there was a little decrease in JOA score and VAS of back/leg pain, but still significantly improved (P < 0.01). Similarly, mean improvement rate of JOA was 83.5 % at 1 year after surgery while 75.6 % at final visit. Successful bone healing was obtained at a mean of 3.8 months after surgery. No cyst reformation and recurrent back/leg pain were observed around the surgical sites.

Conclusions

These lesions could be regarded as a result of facet arthrosis/instability and repetitive facet minor trauma with herniation of synovium through the defective joint capsule. Improvement in lumbago and leg pain may be a consequence of complete cyst resection via hemilaminoplasty plus partial facetectomy with anatomical reconstruction of the posterior spinal elements.
  相似文献   
994.
995.

Purpose

To introduce a new clinical neck tilt grading and to investigate clinically and radiologically whether neck tilt and shoulder imbalance is the same phenomenon in AIS patients.

Methods

89 AIS Lenke 1 and 2 cases were assessed prospectively using the new clinical neck tilt grading. Shoulder imbalance and neck tilt were correlated with coracoid height difference (CHD), clavicle\rib intersection distance (CRID), clavicle angle (CA), radiographic shoulder height (RSH), T1 tilt and cervical axis.

Results

Mean age was 17.2 ± 3.8 years old. 66.3 % were Lenke type 1 and 33.7 % were type 2 curves. Strong intraobserver (0.79) and interobserver (0.75) agreement of the clinical neck tilt grading was noted. No significant correlation was observed between clinical neck tilt and shoulder imbalance (0.936). 56.3 % of grade 3 neck tilt, 50.0 % grade 2 neck tilt patients had grade 0 shoulder imbalance. In patients with grade 2 shoulder imbalance, 42.9 % had grade 0, 35.7 % grade 1, 14.3 % grade 2 and only 7.1 % had grade 3 neck tilt. CHD, CRID, CA and RSH correlated with shoulder imbalance. T1 tilt and cervical axis measurements correlated with neck tilt.

Conclusions

In conclusion, neck tilt is distinct from shoulder imbalance. Clinical neck tilt has poor correlation with clinical shoulder imbalance. Clinical neck tilt grading correlated with cervical axis and T1 tilt whereas clinical shoulder grading correlated with CHD, RSH CRID and CA.
  相似文献   
996.

Purpose

Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine, with unknown origin. Some studies have noted impaired postural balance in AIS, in particular, difficulty to manage situations with sensory conflict. The motion sickness susceptibility can be secondary to a sensory conflict, for example, between visual and vestibular information. Our hypothesis is: patients with AIS have difficulty in managing situations with sensory conflict and therefore have increased motion sickness susceptibility. The purpose of this study was to evaluate in AIS subjects by evaluating their susceptibility to motion sickness, as compared to a control group.

Methods

We conducted an analysis of data on motion sickness susceptibility collected prospectively from 2012, with the B score of motion sickness susceptibility questionnaire. This evaluation was completed for 65 adolescents (age 14.5 ± 1.6 year) with major right thoracic AIS (Cobb = 40.7° ± 13.1°) and 71 matched controls (14.6 ± 1.6 year).

Results

Adolescents with major right thoracic AIS were more susceptible to motion sickness (B score = 5.3 ± 5.8) than controls (B score = 3.4 ± 3.7) with significant difference (p = 0.025).

Conclusions

We interpret our results suggesting there is difficulty for patients with AIS to manage situations with sensory conflict. Previous studies focusing on situations with sensory conflict in AIS have required sophisticated technology. They are not accessible for routine patient management. Our research shows the same result with simple, non invasive, low-cost and quick method: B score of motion sickness susceptibility questionnaire.
  相似文献   
997.

Purpose

Posterior surgery with intraoperative radiotherapy for spinal metastases offers effective therapy, as we have reported previously. However, the procedure involves transfer from the operating room to the radiotherapy room, and as these patients are somewhat immunocompromised, the risk of postoperative surgical site infection (SSI) may be increased. The aim of our study was to identify risk factors and patient characteristics associated with postoperative SSI following posterior fixation surgery and intraoperative radiotherapy for spinal metastases.

Methods

Participants comprised 279 patients who underwent IORT for the treatment of spinal metastases between August 2004 and June 2013. Patients who suffered SSI within 1 month after surgery were categorized as infected, and all others were categorized as non-infected. We compared factors of age, sex, use of pre-operative corticosteroid, medical history of diabetes, prognosis scores (Tomita, Tokuhashi, and Katagiri), pre- and postoperative Frankel scale scores, site of tumor origin, administration of pre-operative radiotherapy, operation time, intraoperative blood loss, intraoperative irradiation dose, and pre- and postoperative performance status between groups.

Results

SSI occurred in 41 patients (14.7 %). Katagiri’s and Tokuhashi’s prognostic scores (P < 0.05 each), postoperative Frankel scale score (P < 0.01), administration of pre-operative radiotherapy (P < 0.05), and postoperative performance status (P < 0.05) all correlated significantly with occurrence of SSI. Multivariate analysis using those factors revealed administration of pre-operative radiotherapy as a factor independently associated with SSI (P < 0.05).

Conclusions

Patient prognosis, postoperative ambulatory function, and pre-operative radiotherapy were risk factors for SSI in patients with spinal metastases. Duration of surgery and intraoperative blood loss were not associated with occurrence of SSI.
  相似文献   
998.

Purpose

We report a single-center, prospective, randomized study for pedicle screw insertion in opened and percutaneous spine surgeries, using a computer-assisted surgery (CAS) technique with three-dimensional (3D) intra-operative images intensifier (without planification on pre-operative CT scan) vs conventional surgical procedure.

Material and method

We included 143 patients: Group C (conventional, 72 patients) and Group N (3D Fluoronavigation, 71 patients). We measured the pedicle screw running time, and surgeon’s radiation exposure. All pedicle runs were assessed according to Heary by two independent radiologists on a post-operative CT scan.

Results

3D Fluoronavigation appeared less accurate in percutaneous procedures (24 % of misplaced pedicle screws vs 5 % in Group C) (p = 0.007), but more accurate in opened surgeries (5 % of misplaced pedicle screws vs 17 % in Group C) (p = 0.025). For one vertebra, the average surgical running time reached 8 min in Group C vs 21 min in Group N for percutaneous surgeries (p = 3.42 × 10?9), 7.33 min in Group C vs 16.33 min in Group N (p = 2.88 × 10?7) for opened surgeries. The 3D navigation device delivered less radiation in percutaneous procedures [0.6 vs 1.62 mSv in Group C (p = 2.45 × 10?9)]. For opened surgeries, it was twice higher in Group N with 0.21 vs 0.1 mSv in Group C (p = 0.022).

Conclusion

The rate of misplaced pedicle screws with conventional techniques was nearly the same as most papers and a little bit higher with CAS. Surgical running time and radiation exposure were consistent with many studies. Our work hypothesis is partially confirmed, depending on the type of surgery (opened or closed procedure).
  相似文献   
999.

Purpose

To directly compare the safety of fluoroscopic guided percutaneous thoracic pedicle screw placement between Caucasians and Asians.

Methods

This was a retrospective computerized tomography (CT) evaluation study of 880 fluoroscopic guided percutaneous pedicle screws. 440 screws were inserted in 73 European patients and 440 screws were inserted in 75 Asian patients. Screw perforations were classified into Grade 0: no violation; Grade 1: <2 mm perforation; Grade 2: 2–4 mm perforation; and Grade 3: >4 mm perforation. For anterior perforations, the pedicle perforations were classified into Grade 0: no violation, Grade 1: <4 mm perforation; Grade 2: 4–6 mm perforation; and Grade 3: >6 mm perforation.

Results

The inter-rater reliability was adequate with a kappa value of 0.83. The mean age of the study group was 58.3 ± 15.6 years. The indications for surgery were tumor (70.3 %), infection (18.2 %), trauma (6.8 %), osteoporotic fracture (2.7 %) and degenerative diseases (2.0 %). The overall screw perforation rate was 9.7 %, in Europeans 9.1 % and in Asians 10.2 % (p > 0.05). Grade 1 perforation rate was 8.4 %, Grade 2 was 1.2 % and Grade 3 was 0.1 % with no difference in the grade of perforations between Europeans and Asians (p > 0.05). The perforation rate was the highest in T1 (33.3 %), followed by T6 (14.5 %) and T4 (14.0 %). Majority of perforations occurred medially (43.5 %), followed by laterally (25.9 %), and anteriorly (23.5 %). There was no statistical significant difference (p > 0.05) in the perforation rates between right-sided pedicle screws and left-sided pedicle screws (R: 10.0 %, L: 9.3 %).

Conclusions

There were no statistical significant differences in the overall perforation rates, grades of perforations, direction of perforations for implantation of percutaneous thoracic pedicle screws insertion using fluoroscopic guidance between Europeans and Asians. The safety profile for this technique was comparable to the current reported perforation rates for conventional open pedicle screw technique.
  相似文献   
1000.

Purpose

A conventional midline posterior approach is used for most of the described surgical techniques. We describe a technique of percutaneous fixation of the pars interarticularis, augmented where necessary by grafting the defect, which minimises muscle injury.

Method

A 4.5 mm partially threaded dynamic compression screw is placed over a wire inserted percutaneously across the pars interarticularis defect. Compression is achieved across the pars interarticularis defect on placement of the screw. The screw is locked in a compressed state.

Results

The patient is mobilised the same day with a corset for comfort and discharged the following day. Aerobic fitness is maintained for 3 months; then, focused rehabilitation performed until a CT scan confirms healing at 5–6 months, at which stage full (sports) activity is resumed.

Conclusions

The minimal tissue injury and small incision used allow for the minimising of complications and for a rapid recovery and discharge from hospital. With adolescents, we have the opportunity to treat symptomatic pars interarticularis defects with minimal disruption to their academic and physical development.
  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